RESISTANCE TRAINING DEVICE AND USES THEREOF

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This present application claims priority to U.S. Provisional Patent Application No. 63/714,824, filed Oct. 31, 2024, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to fitness equipment, specifically to a portable resistance training device and uses thereof.

BACKGROUND

Regular exercise is important for maintaining physical health, and the use of physical training as an instrument of recovery has led to an increased demand for convenient, versatile fitness equipment. For instance, one of the most researched back methodologies to treat musculoskeletal illnesses involves resistance training to produce muscle fatigue that leads to muscle development. Existing resistance training tools, such as weight machines and free weights, are effective but often bulky, expensive, and impractical for use outside of dedicated fitness centers. This has spurred the development of portable resistance training tools that offer users a more accessible way to engage in strength training without the need for large, heavy equipment. Portable resistance training tools, such as resistance bands, compact weights, and body-weight-based devices, allow for versatile exercise routines in various environments, including home, travel, or outdoor settings. These tools are designed to be lightweight, easily transportable, and adaptable for users of different fitness levels. For example, resistance bands can be used for a wide range of exercises targeting different muscle groups and provide variable levels of resistance based on the elasticity of the material.

SUMMARY

In a first example, a portable resistance training device can include a housing that can include a cable spool within the housing around which a cable is at least partially wound, a spring assembly disposed within the housing and can be configured to exert a retraction force on the cable, and a transmission coupled between the spring assembly and the cable spool in the housing. The transmission can be configured to provide a substantially uniform resistance to extension of the cable throughout a range of motion of the cable.

In a second example, a portable resistance training device can include a spring that can be configured to exert a baseline retraction force on a cable and a plurality of power spring enclosures. Each power spring enclosure can have a power spring configured to exert an incremental retraction force when engaged. The portable resistance training device can further include a drive cone, and the cable can be wound around the drive cone. The portable resistance training device can further include a rotary shaft coupled to the power spring enclosures and to the drive cone via a drive cone shaft, a camshaft supporting a plurality of engagement cams having graduated numbers of cam teeth, and a selection knob coupled to the camshaft. The selection knob can be configured to rotate the engagement cams to selectively engage cam teeth thereof with corresponding engagement teeth on one or more of the power spring enclosures to couple one or more of the plurality of power springs to the rotary shaft to add the incremental retraction force of the one or more of the plurality of power springs to the baseline retraction force to provide substantially uniform resistance to extension of the cable throughout a range of motion.

In a third example, a portable resistance training device can include a housing. The housing can include a spring casing enclosing a spring coiled around an arbor shaft. The arbor shaft can include an extension. The housing can further include a first coupler that can include a coupler cavity to receive the extension of the arbor shaft and a protruding portion that can be coupled to a first end of a drive cone shaft. The housing can further include a plurality of power spring enclosures axially aligned, and each enclosing a power spring. The housing can further include a rotary shaft that can extend through the power spring enclosures and can include a protruding extension. The housing can further include a rotary shaft that can extend through the power spring enclosures and can include a protruding extension. The housing can further include a second coupler that can include a coupler cavity to receive the protruding extension of the rotary shaft and can include a protruding portion that can be coupled to a second end of the drive cone shaft. The housing can include the drive cone shaft, and the drive cone shaft can extend between the first coupler and the second coupler. The housing can further include a drive cone at least partially enclosing the drive cone shaft, a camshaft, and a plurality of engagement cams that can be rotatably mounted on the camshaft and each including cam teeth. The portable resistance training device can further include a selection knob that can be coupled to the camshaft.

These and other features and advantages of the present disclosure will become apparent from the following description of particular embodiments, when viewed in accordance with the accompanying drawings and appended claims.

Before the embodiments of the present disclosure are explained in detail, it is to be understood that the technology is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The technology described herein can be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the technology to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the technology any additional steps or components that might be combined with or into the enumerated steps or components. Any reference to claim elements as “at least one of X, Y and Z” is meant to include any one of X, Y or Z individually, and any combination of X, Y and Z, for example, X, Y, Z; X, Y; X, Z; and Y, Z.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B illustrates a portable resistance training device, according to one or more embodiments described herein.

FIG. 2 illustrates an example exploded perspective view of a core torque transmission assembly according to one or more embodiments described herein.

FIG. 3 illustrates an example assembled perspective view of a core torque transmission assembly according to one or more embodiments described herein.

FIG. 4 illustrates an example partial perspective view of the core torque transmission assembly according to one or more embodiments described herein.

FIG. 5 illustrates an example partial side cross-sectional view of the core torque transmission assembly according to one or more embodiments described herein.

FIG. 6 illustrates an example exploded perspective view of a drive cone half of a drive cone according to one or more embodiments described herein.

FIG. 7 illustrates an example perspective view of a resistance training device according to one or more embodiments described herein.

FIGS. 8A-8E illustrates example arrangements of one or more spring assemblies according to one or more embodiments described herein.

FIG. 9 illustrates an example perspective view of a cable spool according to one or more embodiments described herein.

FIG. 10 illustrates an example of an in-line gear transmission according to one or more embodiments described herein.

FIG. 11 illustrates an example of a continuously variable transmission according to one or more embodiments described herein.

FIG. 12 illustrates an example of a mounting configuration of a resistance training device according to one or more embodiments described herein.

DETAILED DESCRIPTION

Embodiments/examples of the present disclosure will now be described in detail with reference to the accompanying figures. Like elements in the various figures may be denoted by like reference numerals for consistency. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the claimed subject matter. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. Additionally, it will be apparent to one of ordinary skill in the art that the scale of the elements presented in the accompanying Figures may vary without departing from the scope of the present disclosure.

Portable resistance training solutions are often limited in terms of resistance variability, durability, and ease of use. Additionally, many portable training tools require users to have a significant understanding of exercise techniques to avoid improper usage, which may lead to injury. Current designs may also lack the ability to be easily customized for specific exercises or body types, and some require additional anchoring points, limiting their versatility in certain environments. Beyond this fundamental flaw in resistance mechanics, resistance bands pose several additional disadvantages. Comfort is often compromised, as the bands can dig into the skin or slip during exercises, making them uncomfortable or even unsafe for certain movements. The material of resistance bands also tends to degrade over time, especially with regular use, leading to cracks, tears, or loss of elasticity, which compromises their long-term reliability and effectiveness.

Another issue is the challenge of securely gripping or anchoring the band during exercises. Many users struggle with keeping the band in place, especially when performing dynamic movements, which can lead to inconsistent resistance or the risk of the band snapping back unexpectedly. This lack of stability can also contribute to poor user compliance, as individuals may become frustrated with the frequent adjustments required during a workout. Additionally, users must often purchase multiple bands to achieve varied levels of resistance, adding to the cost and inconvenience. Each band typically offers a fixed range of resistance, so to accommodate different exercises or progressions in strength, users need an assortment of bands, which diminishes the simplicity and portability that resistance bands are supposed to offer.

Embodiments in accordance with the present disclosure generally relate to a portable resistance training device that utilizes a cable system to provide substantially consistent resistance throughout both the concentric (e.g., shortening) and eccentric (e.g., lengthening) phases of the exercise. Unlike existing resistance training tools (e.g., resistance bands and conventional cable machines), which often provide inconsistent resistance across a range of motion, various embodiments described herein allow for uniform resistance from the start to the end of each movement, offering a more efficient and effective workout experience.

In some embodiments, the portable training device includes a compact, lightweight housing unit containing a retractable cable system. The housing unit can be designed for easy transport and can be securely anchored to various fixed objects (e.g., doorways, walls, or other stable surfaces), making the portable training device adaptable for use in different environments, whether at home, outdoors, or while traveling. In some instances, the portable training device can include a spring assembly coupled to a transmission that can be driven by operation of a cable. For example, the spring assembly can include, but is not limited to one or more torsion springs, one or more compression springs, power springs, a combination thereof, and/or the like. Additionally, the transmission can include, but is not limited, to a gear transmission (e.g., an inline gear train transmission), a planetary gear system, a continuously variable transmission, a variable force compensating cone, a combination thereof, and/or the like.

In some examples, the amount of resistance that a user must overcome to extract the cable from the portable training device, and keep the cable extracted, can be adjusted via operation of the transmission and can remain substantially consistent throughout the travel of the cable. For example, during operation, a user can pull the cable of (or from) the device to initiate a concentric phase of a movement (e.g., a row, press, or curl). As the cable is pulled during the movement, a substantially uniform retraction force biases the cable back to the device consistently across the full range of motion, ensuring that the user experiences uniform resistance to an extraction of the cable from the starting point of the movement to its peak (e.g., where the muscle is strongest). Further, the spring assembly and transmission, in combination, can inhibit slack and/or variation in resistance, unlike systems with weight stacks or elastic bands that often provide the least resistance at the start of a movement.

In some examples, as the user returns the cable to an original position, the movement enters the eccentric phase, wherein the retraction force remains uniformly applied, requiring the user to actively engage muscles to resist the retracting force. This results in the user meeting a balanced and substantially uniform resistance to the extraction of the cable during both the concentric and eccentric phases of the movement and ensures that the muscles are continuously under a desired amount of tension (e.g., promoting enhanced muscle activation, strength gains, and/or overall workout efficiency).

Thus, the portable training device of the various embodiments described herein can be configured to apply a substantially uniform resistance (or a consistent retraction force) to the cable (e.g., where the retraction force remains within a 5% margin) during both phases of muscle contraction, addressing the limitations found in traditional resistance bands or cable systems. As used herein, “substantially uniform resistance” refers to a retraction force applied to the cable by the spring assembly and transmission that remains consistent within a tolerance of about 5% (or less) across the full range of motion of the cable, such as from full retraction to maximum extension (e.g., 3-5 feet as an example). This uniformity can be achieved through structural features of the device that compensate for inherent nonlinear torque variations in the spring assembly, such as the tapered frustoconical shape of the cable spool (which increases an effective moment arm as the cable unwinds), the adjustable gear ratios of an in-line gear transmission, the variable pulley diameters of a continuously variable transmission, or the tapered surface of a variable force compensating cone, ensuring the user experiences a steady, predictable opposing force during both the concentric (extension) and eccentric (retraction) phases of an exercise, without the inconsistent loading typical of elastic bands or weight stacks. Resistance bands typically deliver their highest resistance when the muscle is in its weakest position, whereas the various embodiments described herein offer a substantially uniform and user-defined resistance profile, allowing the user to engage their muscles effectively through the entire range of motion.

For example, in some embodiments described herein, adjustable resistance settings can be used to allow users to customize an amount of resistance force that needs to be exerted on the cable to resist retraction of the cable by the retraction force asserted by the spring assembly. These adjustable resistance settings allow the user to select a desired force level (referred to herein as a “user-selected force level”), such as predefined increments, by way of example, from 2.5 pound-force to 50 pound-force, which can set a magnitude of the substantially uniform resistance encountered when extending the cable. For instance, a needed resistance force can be adjusted between, for example, 2.5 pound-force to 50 pound-force to match a user's fitness level and specific exercise needs. In various embodiments, the resistance level can be adjusted using, for example, a rotatable knob, dial, shifter, or setting mechanism, allowing for a wide range of resistance levels (e.g., with each level attributable to a respective amount of resistive force required to keep the cable extracted from the device throughout the concentric and eccentric phases of the exercise). The spring assembly can include, but is not limited to, one or more power springs, in some instances, in combination with a spring to provide baseline retraction independent of selectable additive resistance, one or more torsion springs, one or more compression springs, a spring-loaded hydraulic piston, or combinations thereof. The transmission coupled between the spring assembly and the cable spool can include, but is not limited to, an in-line gear transmission with a selectable gear train, a continuously variable transmission with adjustable pulleys, a variable force compensating cone over which the cable or a flexible element is routed, or combinations thereof, to modify a spool-to-spring relationship and thereby adjust the resistance while maintaining substantial uniformity. The cable spool can include, for example, a tapered frustoconical drive cone with helical grooves that increase an effective moment arm during unwinding to compensate for torque variations, or a cylindrical spool with grooves for helical winding. Therefore, the portable resistance training device is suitable for users of varying strength levels and for different exercises targeting various muscle groups. This adaptability eliminates a need for multiple pieces of equipment or additional bands, enhancing both convenience and portability.

In some embodiments of this disclosure, additional features of the portable training device can include, but are not limited to, portability, durability, comfort, and/or versatility. The resistance training device can be lightweight (e.g., less than or equal to about five pounds in weight) and compact, making such a device easily portable for users who want to engage in resistance training at locations without fixed training equipment. Further, the retractable cable can coil neatly into a housing of the training device, reducing a bulk of the device. In some examples, the cable and housing can be constructed from durable, wear-resistant materials designed to withstand regular, high-tension use. One or more handles attached to the cable can be ergonomically designed to ensure comfort during extended training sessions and allow for a secure grip, minimizing strain or discomfort during exercise. The resistance training device can be compatible with a wide variety of exercises (e.g., pulling, pushing, and rotational movements), providing a full-body workout experience in a single piece of equipment. Example uses can include, but are not limited to, functional strength training, rehabilitation exercises, and general fitness improvement.

FIGS. 1A-1B are perspective views of a portable resistance training device 100 (referred to herein for simplicity as device 100) according to one or more embodiments of the disclosure. The device 100 can include a housing 104 that encloses internal components, such as described herein. For example, the housing 104 can provide structural support and protection for components therein against environmental factors. The housing 104 can be ergonomically shaped with contoured surfaces to facilitate comfortable handling for transportation and/or use. The housing 104 can be constructed from durable, lightweight materials such as injection-molded plastic and/or aluminum alloys to balance portability and robustness. In some embodiments, the housing 104 can include rounded edges to reduce injury risk during dynamic workouts and/or transportation. In some examples, an overall form factor of the housing 104 can be compact, allowing the device 100 to fit within a gym bag or under a bed for easy storage.

For example, the device 100 can include a selection knob 102. The selection knob 102 can be rotatably mounted on a face portion 108 of the housing 104 opposite a face portion 110 of the housing. The selection knob 102 extends outwardly away from the face portion 108 to provide accessible user interaction without a need for the device 100 to be repositioned in some examples. The selection knob 102 can be used to allow a user to adjust a resistive force of the device 100 as described herein. A resistive force refers to an opposing pull tension generated by one or more selected power springs, calibrated to represent weights from 10 to 100 pounds (by way of example) in incremental steps. This adjustment enables the user to select predefined resistance levels corresponding to different exercise intensities, such as light for warm-ups or heavy for strength training, by way of example. This selection of predefined resistance levels allows the user to set a desired force magnitude (corresponding to a user-selected force level, which determines a substantially uniform resistance encountered when extending a cable during exercises.

In yet some examples, the selection knob 102 can include one or more detents 103. Each detent 103 can correspond to a specific resistance level, with the user twisting the knob 102 until a desired setting. For instance, in some examples, the face portion 108 can include a fixed alignment indicator, such as an etched line or arrow, positioned adjacent to the selection knob 102 to guide resistance or weight level setting. To adjust a resistance, the user pulls the selection knob 102 outward to disengage an internal locking mechanism as described herein, allowing free rotation of one or more underlying cams. With the knob 102 extended, the user then twists the knob 102 until a desired detent, in some instances, aligning a corresponding marking on a knob's perimeter, such as, for example, a numeral indicating “30 lb” or a color-coded band with the fixed alignment indicator on the face portion 108. This visual and/or tactile confirmation ensures the selected detent matches a target resistance level, minimizing errors in setup. In some instances, shallower detents can be used for lighter loads, while deeper dents can correspond to heavier settings, and in some instances, with the fixed alignment indicator providing a reference point even in dim lighting. Once aligned, releasing the knob 102 locks the internal locking mechanism, securing a power spring combination for consistent performance during exercises as described herein. In yet some examples, adjacent to the selection knob 102, an access door 107 on the face portion 108 can be provided to allow for removal of one or more components therein for maintenance and/or resistance upgrades. In some examples, the access door 107 can have a hinged latch for secure closure and can be sealed to prevent debris ingress. In some examples, the hinge can incorporate a torsion spring for automatic closure, enhancing user convenience.

In some examples, the device 100 can include a handle 106. For example, the handle 106 can be located on a longitudinal side portion 130 of the housing 104. In some examples, the handle 106 is an ergonomic handle 106. The handle 106 can extend away from a surface of the longitudinal side portion 130. The handle 106 can provide a secure grip for portability and/or stability during use. In some examples, the handle 106 can be contoured with at least a textured surface to enhance user comfort. The textured surface can include rubberized overmolding for slip resistance, even with sweaty hands. In yet some examples, the handle 106 can include a depression for thumb placement, promoting a natural four-finger grip. During transport, the handle 106 can distribute weight evenly across a palm, reducing fatigue over extended carrying periods.

In some examples, the housing 104 can include an opening 120 on a longitudinal portion 132 of the housing 104, opposite to the longitudinal side portion 130 on which the handle 106 can be located. In yet some examples, the opening 120 and the handle 106 can be located on the longitudinal portion 132 (or the longitudinal side portion 130) of the housing 104. The opening 120 can define a cable exit port through which a cable can exit. The cable can be a flexible resistance cord, for example, constructed from high-strength nylon webbing or braided steel cable, in some instances, coated in plastic for durability and smooth retraction. For example, one end of the cable (or cord) can be fixedly attached to a drive cone 138 located internally within the housing 104. The cable can be helically wrapped around the drive cone 138 within circumferential grooves 140 formed on a drive cone's tapered surface, allowing for controlled unwinding as the user pulls. An opposite end of the cable can extend outward through the opening 120.

In some examples, the opposite end of the cable permanently terminates in a small metal eyelet or reinforced loop, compatible with standard fitness attachments. This eyelet can allow for a secure connection to an interchangeable fitness handle, such as a D-ring grip, carabiner clip, or padded loop used in resistance training for exercises such as rows or presses. For example, the fitness handle can be attached via a quick-release snap hook that clips onto the eyelet, or a velcro strap that wraps around both the eyelet and handle base for adjustable tension. In some examples, the handle is an interchangeable fitness handle, such as a D-ring grip, carabiner clip, or padded loop used in resistance training for exercises such as rows or presses. In some examples, the handle attaches via a quick-release snap hook or velcro strap, enabling customization based on workout type. When not being pulled, the resistance cord retracts fully under tension from a permanent preload spring, winding tightly around the drive cone 138 and stowing within the housing 104 through the opening 120, maintaining a compact profile and preventing overrides or tangles.

In some examples, the housing 104 can include one or more ventilation slots 126 for heat dissipation from one or more internal components of the device 100, while, in some instances, maintaining dust resistance. The housing 104 can have a top longitudinal portion 124. The ventilation slots 126 can extend from the top longitudinal portion 124 downward through the longitudinal side portion 132, forming curved, elongated apertures that follow contoured edges of the housing 104 to direct airflow across internal heat sources. The ventilation slots 126 can dissipate heat generated by friction in power springs (not shown in FIGS. 1A-1B) and/or the drive cone 138 during prolonged use, as well as, in some instances, thermal buildup from bearing rotation. In some examples, airflow through the ventilation slots 126 can be passive, driven by natural convection as warmer internal air rises within the housing 104 and exits via upper slots (e.g., the ventilation slots 126), drawing cooler ambient air in through a lower vent (e.g., the opening 120). In some examples, fine mesh screens can be used within the ventilation slots 126 to block dust and/or sweat ingress, preserving component longevity. In high-intensity sessions, this ventilation can prevent overheating, which could otherwise increase spring torque variability or degrade lubrication.

In some examples, the device 100 can include anchor cleats 114 (or also can be referred to as anchors), which can be attached to or integrally formed on an underside longitudinal portion 142 of the housing 104. The anchor cleats 114 and an adjustment mechanism 116 can collectively form a clamping mechanism because U-shaped cleats hook over a structural edge, while a threaded knob (as the adjustment mechanism 116 in some examples) drives pads 118 to apply adjustable compressive force, securely gripping the surface without permanent fixtures. By way of example, the anchor cleats 114 can be door cleats, frame cleats, and/or anchor brackets. The anchor cleats 114 can be spaced apart at respective ends of the underside longitudinal portion 142, which can be opposite to the top longitudinal portion 124, in some instances, providing balanced anchoring. Each anchor cleat 114 can have a U-shaped profile designed to hook over a door jamb or frame edge, securing the device 100 in place for anchored exercises. In some examples, the anchor cleats 114 can have padded inner surfaces to prevent scratching on door surfaces and flared openings for easy installation over varying thicknesses. For example, each anchor cleat 114 can have a contoured profile for secure engagement and disengagement with standard door frames ranging from 1 to 2 inches thick, or thinner or thicker in some instances.

In some examples, the device 100 can include the adjustment mechanism 116. In some examples, the anchor cleats 114 and the adjustment mechanism 116 can be referred to as the clamping mechanism. The adjustment mechanism 116 can be provided for each anchor cleat 114 to tension each anchor cleat 114 against a door frame, as described herein. The adjustment mechanism 116 can include a knob 112 that the user can engage (e.g., rotate, push, etc.) to advance or retract the pads 118 at an end of a shaft 117 passing through a clearance hole 113 in a base of each anchor cleat 114. In some examples, rotating the adjustment mechanism 116 clockwise (or applying a force to the knob 112) pushes the pads 118 toward an opposite end of the anchor cleat 114 (e.g., opposite end of which the clearance hole 113 is located) to clamp the door frame securely to secure the device 100 to the door frame for workout (exercises). Counterclockwise rotation of the adjustment mechanism 116 (or pulling the knob in an opposite direction in which the force was applied) releases the tension, allowing detachment and/or repositioning of the device 100. In some examples, the pads 118 can be small circular foam or rubber pads (e.g., grips) at ends of the shaft 117 (opposite ends to which the adjustment mechanism 116 can be coupled) that press against the doorway when the adjustment mechanism 116 is engaged by the user, distributing pressure evenly and preventing scratches on the door frame. In some examples, the pads 118 can be compressible neoprene discs, in some instances, about 1 inch in diameter, for non-marking contact. Beyond door frames, the anchor cleats 114 can attach to other structures such as squat rack uprights or vertical posts by similar clamping, with a U-shape profile of the anchor cleats 114 accommodating bars up to 3 inches in diameter (in some instances more or less) for versatile gym and/or home setups.

FIG. 2 is an exploded perspective view of the portable resistance training device 100 of FIGS. 1A-1B, illustrating a disassembled perspective view of a core torque transmission assembly 201 of the device 100. In the exploded perspective view of the device 100, a spring casing 208 is shown as removed from the face portion 110 of the housing 104, opposite the face portion 108 on which the selection knob 102 is located, exposing an opening 202. The opening 202 can function as a mounting interface for the spring casing 208. When the spring casing 208 is detached from the housing 104, the opening 202 provides access to components of the device 100.

In some examples, the device 100 includes the spring casing 208, which functions as a dedicated enclosure for a spring 249 to maintain cord tension independently of selectable resistances from power springs 250-254 of the device 100. A constant spring refers to a power spring that delivers a fixed torque output across a working range, in some instances, calibrated to about 5 pounds of tension, ensuring a cable (e.g., resistive cable) remains snug against a drive cone 224 of the device 100 regardless of which of the power springs 250-254 are engaged via engagement cams 262-268 of the device 100. In some examples, the drive cone 224 can be drive cone 138 of FIG. 1B. In some examples, the spring 249, can be a constant-force spring that remains constantly engaged to deliver a fixed baseline retraction force (e.g., 5 pounds) for maintaining cord tautness independent of which of the power springs 250-254 are be used or engaged. In other examples, the spring 249 is a power spring. In yet some examples, one or more of the power springs 250-254 can be constant-force springs (e.g., in some instances higher-tension constant-force springs compared to the spring 249) that can be variably engaged via the engagement cams 262-268 by a user through the knob 102 to add adjustable resistance levels (e.g., 10-50 pounds each) to an overall pull force during exercises. The spring 249 can function continuously to prevent slack, overrides, and/or loose windings in idle states (e.g., when no pull is applied), while the power springs 250-254 can be selectively activated for exercise-specific torque, allowing user-controlled intensity without affecting baseline retraction, thereby enhancing overall device reliability and safety.

In some examples, the spring casing 208 can include a spring enclosure 204, which can be a machined cylindrical canister formed from steel or high-strength plastic, in which the spring 249 is coiled around at least a portion of an arbor shaft 212 for delivering, for example, a steady torque output. The spring 249 can be a flat, high-carbon steel strip, in some instances about 0.005 inches thick and pre-stressed into a tight spiral around the arbor shaft 212, providing near-constant force over an extension range. A portion of the arbor shaft 212 extending through and/or into the spring enclosure 204 can function as a central cylindrical spool and can be a winding core around which the spring 249 coils and uncoils, transmitting rotational torque to a drive cone shaft 234 of the device 100. For example, the spring 249 can generate, by way of example, a baseline 5-pound tension to keep the cable (e.g., a resistance cord) fully retracted (e.g., completely wound around the drive cone 224) and taut (e.g., pulled tight without slack or gaps between windings), when idle, preventing slippage, overrides, and/or loose loops that could cause jamming during initial pulls. This preload can be used for user safety and device reliability, as this configuration eliminates slack that can lead to sudden snaps or inconsistent starts in exercises such as bicep curls or rows.

In some examples, the spring casing 208 can include an arbor retaining collar 206 and a bearing 210, which can integrate with the spring enclosure 204 to support the arbor shaft 212. The arbor retaining collar 206 can be a threaded retaining ring with a slotted drive head. The arbor retaining collar 206 can engage an outer race (e.g., a stationary outer ring of the bearing 210 that houses rolling elements) of the bearing 210 to axially secure the arbor shaft 212 against longitudinal movement and prevent end-play that could cause vibration and/or misalignment under a load, while allowing free rotation. For example, at least a portion of the arbor shaft 212 can extend coaxially through a central opening 255 in the spring enclosure 204, then through the bearing 210, and into the arbor retaining collar 206, which threads onto a splined end 263 of the arbor shaft 212. The arbor retaining collar 206 threads onto the splined end 263 of the arbor shaft 212.

In some examples, the bearing 210 can be a deep-groove ball type. The bearing 210 can journal the arbor shaft 212 and can function as a rotational axis for the spring 249, through the central opening 255 in the spring enclosure 204. The arbor shaft 212 can be a hardened steel rod with the splined end 263. The arbor shaft 212 on an opposite end of the splined end 263 includes an extension 214. The extension 214 of the arbor shaft 212 can protrude coaxially from an opposite end and mate with (or be inserted into) a coupler cavity 218 of a coupler 216 of the device 100. The extension 214 can sit (e.g., snuggly fit into) in the coupler cavity 218 to engage the coupler 216. The coupler 216 functions as an adapter hub that bridges (or couples) the arbor shaft 212 to the drive cone shaft 234, transmitting torque from the spring 249 to the drive cone 224 and, in some instances, providing radial support to maintain alignment under dynamic loads. For example, the coupler 216 includes a protruding portion 217, which can be an annular flange or sleeve extending from a body of the coupler 216.

The device 100 can include, in some instances, a ball bearing 220. The ball bearing 220 can be positioned, press-fit, or mounted around the protruding portion 217 to absorb lateral forces during retraction and/or prevent wobble that could accelerate wear. The protruding portion 217 can include an internal cavity (e.g., a second keyed bore opposite the coupler cavity 218) into which a first end of the drive cone shaft 234 inserts snugly. For example, the first end of the drive cone shaft 234 can be inserted into the internal cavity of the protruding portion 217, by way of example, via a keyed or interference fit for positive engagement, preventing relative rotation while accommodating minor thermal expansion. This configuration (e.g., a mating of the extension 214 in the coupler cavity 218 on one side and a rotary shaft end in the internal cavity on the other side of the coupler 216) transmits rotational motion from the extension 214 through the coupler 216 to the drive cone shaft 234. The coupler 216 can be precision-machined from aluminum or steel. For example, the extension 214 can be a coaxial protrusion at one end of the arbor shaft 212, in some instances, having a rectangular or D-shaped cross-section designed for a snug, anti-rotational fit into the coupler cavity 218 of the coupler 216. This structure allows for alignment and torque transmission from the spring 249 to the drive cone shaft 234 without slippage, while a compact design of the extension 214 minimizes added mass to the rotating assembly.

In some examples, the drive cone shaft 234 couples the coupler 216 to the drive cone 224, forming a torque transmission path for both preload and power spring forces. By way of example, the drive cone 224 can be formed by a pair of substantially identical halves that assemble together along a longitudinal axis to enclose the drive cone shaft 234, as illustrated in FIG. 6, which depicts a drive cone half 600. For example, the drive cone half 600 can include a contoured outer surface defining helical grooves 630 for receiving the cable, and channels or cutouts 602-614 within a body of the drive cone half 600 extending along a central portion thereof. Two drive cone halves can be substantially identical in form but configured as mirror-image counterparts (e.g., one left-hand and one right-hand version) to facilitate symmetric assembly and allow for balanced helical grooves when joined. This mirrored design allows the channels or cutouts 602-614 in each half to precisely register with those of the opposing half, forming a cylindrical cavity 227 of the drive cone 224, in some instances, without gaps or misalignments.

In some examples, the channels or cutouts of two drive cone halves can align and cooperate to form the first opening 223 at a base of the drive cone 224 and the second opening 225 at an apex or tip of a tapered portion of the drive cone 224, with the cylindrical (or longitudinal) cavity 227 extending coaxially therebetween through the body of the drive cone 224. In some examples, the cylindrical cavity 227 is a cylindrical bore sized to receive the drive cone shaft 234 with clearance for rotation. For example, to assemble the drive cone 224, the drive cone shaft 234 is positioned within the channels 602-614 of a first drive cone halve (e.g., the drive cone halve 600 of FIG. 6), after which the second drive cone halve can be aligned over the first drive cone halve and the drive cone shaft 234 such that the channels register to enclose at least a body of the drive cone shaft 234 while respective first and second ends of the drive cone shaft 234 protrude from one of the first and second openings 223 and 225. The first and second drive cone halves can be secured together via bolts, fasteners, and/or interlocking engagements to form the drive cone 224, as shown in FIG. 2, with the first end of the drive cone shaft 234 protruding coaxially from the first opening 223 and a second end of the drive cone shaft 234 protruding from the second opening 225 for coupling to downstream components.

In some examples, the drive cone 224 can be a tapered, conical spool rotatably mounted within the housing 104 and configured to controllably dispense and retract the cable under torque. The drive cone 224 can include a base portion 229 at which the first opening 223 can be located. The drive cone 224 can gradually taper from the base portion 229 toward an apex 222 of the drive cone 224 at which the second opening 225 can be located. In some examples, the drive cone 224 can have a frustoconical body, for example, for efficient cable winding and/or unwinding. In some examples, an outer surface of the drive cone 224 can be machined or molded with a series of helical grooves 226 that spiral circumferentially around the cone from the base portion 229 to the apex 222, wherein the helical grooves 226 decrease in circumferential length as a diameter of the drive cone 224 reduces along a taper, accommodating successive layers of the cable with progressively shorter wraps to maintain uniform tension distribution. In some examples, the helical grooves 226 can correspond to the circumferential grooves 140 of FIG. 1B. In some examples, one end of the cable is fixedly anchored to the drive cone 224 at or near the base portion 229, such as via a pinned or crimped attachment within or at a dedicated anchor slot 241 at about the base portion 229, after which the cable is helically wound along the helical grooves 226 toward the apex 222, seating snugly within contoured channels (e.g., the helical grooves 226) to prevent slippage or overrides during retraction. A remaining or free end of the cable can extend from the apex 222 through the opening 120 (e.g., cable exit port) of the housing 104. This allows the user to pull the cable outward. As more cable is unwound, a tapering geometry of the drive cone 224 increases an effective moment arm from an axis of rotation. This amplifies a user-applied torque and compensates for nonlinear torque buildup in the power springs 250-254. As a result, a more consistent resistive force profile can be maintained over a full range of cable extensions.

In some examples, the device 100 can further include a rotary shaft 256 for transmitting torque from the power springs 250-254 to the drive cone 224. The rotary shaft 256 can include a body 257. The body 257 can extend coaxially through a front mounting opening 270 of a spring pack housing 238 of the device 100. The rotary shaft 256 continues through central openings 271 in each of the power spring enclosures 240-246 and exits through a rear opening 273 of the spring pack housing 238. At a rear end (or an end) of the rotary shaft 256, a protruding extension 258 mates with a coupler cavity 272 of a coupler 236, which can be structurally similar to the coupler 216 and the coupler cavity 218 that receives the extension 214 from the arbor shaft 212. The coupler 236 can function as an adapter hub to allow for concentric alignment and anti-rotational engagement, for example, via a keyed or D-shaped interface, preventing slippage under load while accommodating thermal expansion. In some examples, at a front end (or other end) of the rotary shaft 256 (e.g., a remaining end protruding from the rear opening 273), a ball bearing 260 can be positioned around this portion of the rotary shaft 256 to journal this shaft portion for low-friction rotation, absorb radial and axial loads from spring retraction forces, and/or minimize end-play or vibration during high-torque operation.

In some examples, the coupler 236 includes a protruding portion 259, which can be similar to the protruding portion 217. The protruding portion 259 can include a cavity. In some examples, the cavity of the protruding portion 259 can be a keyed cavity (e.g., a bore on an opposite side of the coupler cavity 272 of the coupler 236, and can be sized to receive and secure the end of the drive cone shaft 234, for example, with an interference or splined fit, completing a torque path by linking the power springs 250-254 through the drive cone shaft 234. The drive cone shaft 234 can have one end that mates with the cavity in the protruding portion 217 of the coupler 216 and another end that mates with the cavity in the protruding portion 259 of the coupler 236. This mating can form a coaxial assembly. The drive cone shaft 234 couples to the drive cone 224 by extending through the first opening 223 and the cylindrical cavity 227 of the drive cone 224, with a shaft's end protruding from the base portion 229 and secured, in some examples, via a flange, set screw, or keyed retainer (not shown) to rotate the drive cone 224, allowing, for example, synchronized winding/unwinding of the cable under combined preload and selectable power spring forces.

In some examples, the spring pack housing 238 includes power spring enclosures 240-246. These enclosures can align axially along the drive cone shaft 234. Each enclosure contains one of the power springs 248-254. The power springs 248-254 can provide incremental resistance levels. While four power spring enclosures are shown and thus four power springs, other examples can include more or fewer power spring enclosures. In yet some examples, each power spring enclosure 240-246 houses a respective power spring 248-254 that exerts an incremental retraction force when engaged, such as 10-40 pounds of additive torque (by way of example) contributed to a total retraction force upon selective coupling to a rotary shaft 256 via one or more engagement cams 262-268. This incremental contribution allows for user-customizable total force levels while preserving a substantially uniform resistance profile across a cable's range of motion.

In some examples, the spring pack housing 238 can have a modular form factor. This form factor can accommodate varying numbers of power spring enclosures. In some examples, the power spring enclosures 240-246 can differ in size (e.g., diameters and/or lengths). These variations can accommodate power springs with different torques. In some examples, power spring enclosures 240-244 have similar sizes, and these power spring enclosures can house the same or different power springs (e.g., power springs have different torque capabilities). In such examples, the power spring enclosure 246 can be larger and house a power spring with higher torque than those in power spring enclosures 240-244.

For example, the power spring enclosure 240 can house the power spring 248. This spring can have the lowest torque among the power springs 248-254. The power spring 248 can have a narrow strip width and fewer coils relative to the remaining power springs of the power springs 250-254. The power spring 248 can provide a baseline resistance, such as about 10 pounds by way of example. The power spring enclosures 242-244 in some examples each house one of the power springs 250 or 252. These springs can have wider strips and more coils than power spring 248. The power springs 250-252 can provide an additive torque, such as about 20 to 30 pounds each by way of example. The power spring enclosure 246 can house the power spring 254. In some examples, this spring has the highest torque among the power springs 248-254. The power spring 254 can have a widest strip and most coils relative to the power springs 248-252. The power spring 254 can provide a maximum resistance, such as about 40 pounds by way of example.

In some examples, each power spring of the power springs 248-252 is a pre-stressed high carbon steel strip. The strip coils tightly in a spiral and around a central arbor. The central arbor can be a portion of the body 257 of the rotary shaft 256. An inner end of the strip, which can be closest to an axis of the arbor (e.g., a central longitudinal line of the arbor), can be fixed by a mechanical fastener to the arbor. Examples of fasteners can include, but are not limited to, a pin, crimp, or weld. This attachment can allow for anti-rotational engagement during winding, such that the strip does not slip relative to the arbor as the strip winds. In some examples, an outer end of the strip forms an outermost coil. For example, a hooked tab, anchor slot, or adhesive bond can be used to secure the outer end to an inner circumferential wall of a power spring enclosure (e.g., a cylindrical inside surface of the power spring enclosure).

In some examples, the device 100 includes a camshaft 228. The camshaft 228 can extend through central openings 239 of the engagement cams 262-268. Each engagement cam of the engagement cams 262-268 includes cam teeth. The cam teeth can be radial protrusions on an outer circumference of an engagement cam. For example, the engagement cam 262 includes multiple cam teeth 290. The engagement cam 264 can include fewer cam teeth 292 than the engagement cam 262. The engagement cam 266 can include cam teeth 294. The engagement cam 266 can have fewer teeth than the engagement cam 264. The engagement cam 268 can include a cam tooth 296. The engagement cam 268 can have fewer teeth than the engagement cam 266. In other examples, the engagement cam 268 can include more than one tooth. In some examples, a number of cam teeth decreases from the engagement cam 262 to the engagement cam 268, which allows binary selection for resistance levels as described herein.

In some examples, the cam teeth 290-296 engage respective engagement teeth 282-288 on the power spring enclosures 240-246. Engagement occurs, for example, when a cam tooth meshes with or interlocks against an engagement tooth, thereby preventing rotation of one or more power spring enclosures relative to the spring pack housing 238 and allowing the rotary shaft 256 to wind an enclosed power spring for torque addition. For example, one of the cam teeth 290 of the engagement cam 262 can engage the engagement tooth 282 of the power spring enclosure 240. In some examples, one of the cam teeth 292 of the engagement cam 264 can engage the engagement tooth 284 of the power spring enclosure 242. In yet some examples, one of the cam teeth 294 of the engagement cam 266 can engage the engagement tooth 286 of the power spring enclosure 244. The cam tooth 296 of the engagement cam 268 can engage the engagement tooth 288 of the power spring enclosure 246 in some instances.

For example, cam engagement with the power spring enclosures 240-246 can occur when the user selects a resistance level via the selection knob 102. By way of example, the user pulls the selection knob 102 outward (e.g., away from the face portion 108). This disengages an internal locking mechanism. The internal locking mechanism can include spring-loaded pawls 209 (referred to herein for simplicity as pawls). The pawls 209 retract from a corresponding notch of notches 211 on the camshaft 228. As such, the pawls 209 move inward or away from the notches 211 under spring compression. This frees the camshaft 228 from rotational restraint. The selection knob 102 can be fixedly attached to one end of the camshaft 228, in some instances, via a keyed or splined connection, as shown in FIG. 2. With the pawls 209 retracted, the user twists the knob 102 from one tactile detent to another. Each detent 103 corresponds to (or represents) a specific resistance level, indicated by visual markings on the knob perimeter, such as “10 lb” or “30 lb.” A varying number of cam teeth on the engagement cams 262-268 enables binary selection of resistance combinations.

For instance, in some examples, the engagement cam 262 has a most teeth (e.g., eight, spaced evenly at 45 degrees circumferentially by way of example), the engagement cam 264 has fewer teeth (e.g., four at 90 degrees by way of example), the engagement cam 266 has two teeth (at 180 degrees by way of example), and the engagement cam 268 has one tooth. This graduated tooth count and spacing ensures that, at each detent position, one or more cam teeth of one or more of the engagement cams 262-268 can align with a corresponding engagement tooth of the power spring enclosures 240-246 for additive torque. The twisting of the knob 102 transmits torque through the camshaft 228 and rotates one or more of the engagement cams 262-268, which mount rotatably along the camshaft 228. The rotation can align one or more cam teeth with engagement teeth on desired power spring enclosures. In some examples, releasing the knob 102 re-engages the pawls 209 into a nearest notch of the notches 211. This locks one or more of the engagement cams 262-268 in the new position. The selected engagements can be held securely during use.

Thus, the selection knob 102 can control cam engagement. For example, the user pulls the knob 102 outward along an axis. In some examples, this shifts a pull collar on a knob stem of the selection knob 102. The collar compresses a torsion return spring and the pawls 209 retract from the notches 211 on the camshaft 228. In some examples, the pawls 209 can be radial pins in a knob hub (e.g., the camshaft 228) and thus protrude circumferentially from a body 231 of the camshaft 228. In some examples, the notches 211 can be circumferential grooves spaced for resistance levels. With the pawls 209 retracted, the engagement cams 262-268 can rotate freely. For example, the user twists the knob 102 to a desired detent. The twisting, in some instances, rotates the engagement cams 262-268 via the camshaft 228. The rotation can align one or more of the cam teeth 290-296 with one or more corresponding engagement teeth 282-288 on the power spring enclosures 240-246. Binary combinations select which springs engage. For example, one of the cam teeth 290-292 on a respective one of the engagement cams 262-264 can be aligned with corresponding engagement teeth 282 and 284 of the power spring enclosures 240-242. Once aligned, releasing the selection knob 102 re-engages the spring-loaded pawls 209 into the nearest notches of the notches 211 on the camshaft 228, locking the engagement cams 262 and 264 in position to maintain the alignment during use. For example, releasing the knob 102 allows the torsion spring to push the collar forward, and the pawls 209 sit in the nearest notches. This locks the engagement cams 262-264 rotationally. The selected engagements hold under load. For example, during exercise, the user pulls on the cable, and this rotates the drive cone 224. This torques the rotary shaft 256. The power spring enclosures 240-242 wind corresponding power springs 248-250. The power springs 248-250 provide near constant retraction torque. The drive cone 224 can vary a moment arm as the cable unwinds to compensate for minor spring torque rise. The result is an about consistent resistive force to a user over a full range. For example, a substantially uniform resistive force can be experienced by a user over a full range, as the combined baseline and additive retraction forces from the engaged power springs, transmitted through the rotary shaft 256 and drive cone 224, maintain consistency within approximately 5% across the cable's range of motion (e.g., 3-5 feet as an example). The combined baseline and additive retraction forces refer to a fixed preload torque (e.g., approximately 5 pounds by way of example) provided continuously by the baseline spring 249 independent of user selection, plus one or more incremental torque contributions (e.g., 10-40 pounds each as an example) from one or more selectively engaged power springs 248-254, which together yield a total, user-defined retraction force that remains substantially uniform throughout the cable's extension and retraction.

In some examples, the camshaft 228 includes a body 231. At one end of the camshaft 228, a collar 230 secures the camshaft 228. The collar 230 can be a split ring design. One or more set screws can be used to secure the collar 230 to a shaft end. In some examples, a bearing 280 mounts around the body 231 of the camshaft 228. The bearing 280 can be adjacent to the collar 230. The bearing 280 supports rotation and absorbs thrust loads. Toward the other end of the camshaft 228, bearing bushings 232 support the camshaft 228. In some examples, the bearing bushings 232 can include a bushing 215, 219, and 221. The bushing 215 can be smaller than the bushings 219 and 221. The bushing 219 can be smaller than the bushing 221. These bushings 215, 219 and 221 can be self-lubricating sleeves and can be used to reduce friction and dampen vibration. Another end of the camshaft 228 can be secured to the selection knob 102, as shown in FIG. 2, and as described herein.

FIG. 3 is an example of an assembled perspective view of a core torque transmission assembly 300 of the device 100. The core torque transmission assembly 300 can correspond to an assembled version of the exploded core torque transmission assembly of FIG. 2. FIG. 4 is a partial perspective view of the core torque transmission assembly 300 during resistance selection operation according to one or more embodiments of the disclosure. In this view, the selection knob 102 can be pulled outward along the camshaft 228 to retract the pawls 209 from the notches 211, allowing rotation of the engagement cams 262-268 to align select cam teeth 290-296 with engagement teeth 282-288 on targeted power spring enclosures 240-246 for a desired additive resistance level.

The core torque transmission assembly 300 can include a constant retraction assembly 304, a drive cone winding assembly 306, a selectable power spring assembly 308, and a resistance selection assembly 310. For example, the constant retraction assembly 304 can be configured to maintain baseline cable tension independently of selectable resistances from the selectable power spring assembly 308, where baseline cable tension refers to a fixed, low-level preload force (e.g., ˜5 lb) that keeps a cable 302 fully retracted and taut against the drive cone winding assembly 306 during idle states to prevent slack, overrides, and/or tangles. For example, the constant retraction assembly 304 can achieve this by continuously biasing a forward end of the drive cone shaft 234 with a dedicated spring, transmitting steady torque through coaxial couplers (e.g., the couplers 216 and 236) to the drive cone winding assembly 306 without variation under load or selection changes.

In some examples, the constant retraction assembly 304 includes the spring 249 coiled around the arbor shaft 212 within the spring enclosure 204. The spring 249 can be a flat, prestressed high-carbon steel strip that delivers a fixed torque, for example, about 5 lb-in. The spring 249 can apply this torque through the extension 214 that mates with the coupler cavity 218 in the coupler 216. The protruding portion 217 of the coupler 216 journals the ball bearing 220 to provide radial stability. The coupler 216 connects coaxially to a forward end of the drive cone shaft 234, for example, through a keyed interface, which transmits a preload torque (e.g., the fixed torque) without slippage. In some examples, the arbor retaining collar 206 of the constant retraction assembly 304 threads the splined end 263 of the arbor shaft 212 to secure the bearing 210 of the constant retraction assembly 304 against axial play and vibration.

In some examples, the drive cone winding assembly 306 coordinates cable retraction and extension under the combined torques of the selectable power spring assembly 308 and the constant retraction assembly 304. This configuration delivers a consistent resistive force profile across the cable's extension range by varying an effective moment arm as layers unwind. For example, the drive cone winding assembly 306 includes a tapered spool rotatably mounted on the drive cone shaft 234. Helical cable windings interact with a shaft's bidirectional torque to dispense the cable 302 outward under user pull and to rewind the cable 302 upon release. The tapered geometry compensates for nonlinear spring torque buildup through geometric amplification. In some examples, the drive cone winding assembly 306 includes the drive cone 224 having the helical grooves 226 that spiral from the base portion 229 to the apex 222. The drive cone shaft 234 of the drive cone winding assembly 306 extends through the cylindrical cavity 227, with both ends protruding from first and second openings 223 and 225. These ends mate with couplers in the constant retraction assembly 304 and the selectable power spring assembly 308. In some examples, the anchor slot 241 at the base portion 229 secures one end of the cable 302 using a pin or crimp as an example. The free end of the cable 302 exits the apex 222 after being helically wrapped around the drive cone 224 within the helical grooves 226. The helical grooves 226 can have a decreasing pitch toward the apex 222 to compensate for the diameter reduction. This configuration allows components to rotate synchronously with the drive cone shaft 234, unwind layers of the cable 302 outward under pull to increase an effective radius for torque amplification, and retract smoothly without overrides.

In some examples, the selectable power spring assembly 308 can be configured to provide modular additive torque in incremental steps (e.g., 10-40 lb) to the baseline from the constant retraction assembly 304, enabling total resistances from 10 to 100 lb based on user selections. For example, the selectable power spring assembly 308 can achieve this by axially aligning multiple power spring enclosures as described herein along the rotary shaft 256 within the spring pack housing 238, where engaged enclosures couple respective power springs to a shaft for torque addition, allowing disengaged ones to freewheel idly during operation.

In some examples, the selectable power spring assembly 308 includes the spring pack housing 238. The power spring enclosures 240-246 can be axially along the rotary shaft 256, with each enclosing a prestressed power spring 248-254. The power springs 248-254 can be high-carbon steel strips varying in width and coil count, coiled around a portion of the body 257 of the rotary shaft 256. Inner ends of the power springs 248-254 can be pinned, crimped, or welded to the body 257 for anti-rotational engagement. Outer ends of the power springs 248-254 can be anchored via hooked tabs or slots to enclosure walls. The protruding extension 258 of the rotary shaft 256 of the selectable power spring assembly 308 can engage a coupler cavity 272 in a coupler 236. The protruding portion 259 of the coupler 236 can key to a rear end of the drive cone shaft 234 for anti-rotational torque transfer. In some examples, the ball bearing 260 of the selectable power spring assembly 308 can journal a front end of the rotary shaft 256 to minimize friction. This configuration ensures the components wind engaged power springs onto the rotary shaft 256 under load to add torque that flows forward through the coupler 236 without affecting disengaged power spring enclosures.

In some examples, the resistance selection assembly 310 can be configured to enable binary selection and locking of power springs in the selectable power spring assembly 308 via user input, providing precise, tactile control over additive resistance levels without mechanical complexity. For example, the resistance selection assembly 310 can achieve this by mounting the camshaft 228 with graduated cams adjacent to the power spring enclosures, where knob rotation indexes one or more of the cam teeth 290-296 to immobilize targeted power spring enclosures relative to the spring pack housing 238, locking the selection via pawls 209 to hold under exercise loads.

For example, the resistance selection assembly 310 mounts the camshaft 228 parallel to the rotary shaft 256. The engagement cams 262-268 of the resistance selection assembly 310 can be rotatably journaled thereon via the central openings 239 and positioned adjacent to the engagement teeth 282-288 on the power spring enclosures 240-246. The selection knob 102, in some instances, part of the resistance selection assembly, can be coupled to one end of the camshaft 228, with the detents 103 providing tactile stops aligned to a fixed indicator on the face portion 108. The pawls 209 can interact with the notches 211 on the body 231 of the camshaft 228 of the resistance selection assembly to retract upon knob pull and free rotation. The engagement cams 262-268 can have graduated tooth counts (e.g., 8:4:2:1) spaced circumferentially. These can mesh select teeth 290-296 with enclosure teeth 282-288 to immobilize targeted power spring enclosures. The twisting of the knob 102 can rotate one or more of the engagement cams 262-268 to align teeth for desired combinations (e.g., engagement cams 262 and 264 for 40 lb total) before pawl re-engagement locks the position. This locked position sets the substantially uniform resistance encountered when extending the cable at a user-selected force level, determined by an additive torque from the engaged power springs transmitted coaxially to the drive cone. Once locked, the selected engagements deliver a substantially uniform resistance to cable extension, where the retraction force remains consistent (e.g., within 5% by way of example) throughout a full range of motion due to a coaxial torque path from the constant retraction assembly 304 through the selectable power spring assembly 308 to the drive cone winding assembly 306.

In some examples, the drive cone shaft 234 can be configured as the primary torque conduit shared across assemblies, unifying torque transmission from the constant retraction assembly 304 and selectable power spring assembly 308 to the drive cone winding assembly 306 for bidirectional force flow during extension and retraction. For example, the drive cone shaft 234 can achieve this by extending coaxially through the drive cone winding assembly 306, branching preload torque from the constant retraction assembly 304 at its forward end while receiving additive torque from the selectable power spring assembly 308 via the coupler 236 at its rear end under load.

FIG. 5 is a partial side cross-sectional view of the core torque transmission assembly 300 under partial cable extension during exercise load according to one or more embodiments of the disclosure. In some examples, the drive cone winding assembly 306 is shown with the cable 302 partially unwound from the helical grooves 226 of the drive cone 224, illustrating a varying moment arm effect that compensates for spring torque buildup to maintain about a consistent resistive force to the user. A central axis of rotation 504 extends coaxially along the drive cone shaft 234 and the rotary shaft 256, representing a common torque transmission path through the assemblies. In some examples, near the apex 222 of the drive cone 224 (corresponding to initial or minimal extension states), a first moment arm Y0 extends radially from the central axis of rotation 504 to a first force application point F0 on the cable 302, where the cable 302 is tangent to a cone's surface at a smaller effective radius. In some examples, closer to the base portion 229 (corresponding to greater extension states), a second moment arm Y1 extends radially from the central axis of rotation 504 to a second force application point F1 on the cable 302, where the cable is tangent at a larger effective radius.

In some examples, the drive cone 224 can be configured with a tapered, frustoconical profile that increases in diameter from the apex 222 to the base portion 229, such that as the user pulls the cable 302 outwardly through the opening 120, successive layers unwind from smaller radii near the apex 222 toward larger radii near the base portion 229. This geometry results in a progressive increase in an effective moment arm (e.g., from Y0 to Y1) for a user's constant pull force applied at points F0 and F1, respectively, thereby amplifying torque on the drive cone shaft 234 to counteract the inherent nonlinear torque rise in the spring 249 and engaged power springs 248-254 as these springs wind onto the rotary shaft 256. For instance, at minimal extension, the short moment arm Y0 at F0 provides lower amplification near the apex 222, aligning with lower initial spring torque; as extension increases, the longer moment arm Y1 at F1 near the base portion 229 delivers higher amplification, matching a springs' increasing torque output over turns to yield a near-constant resistive force profile (e.g., within +5% variation in some instances) across a full 3-5 ft cable travel range as an example. The central axis of rotation 504 remains fixed, with the drive cone shaft 234 rotating synchronously thereunder to transmit the compensated torque rearward through the coupler 236 to the selectable power spring assembly 308 and forward baseline from the constant retraction assembly 304.

In yet some examples, while FIG. 5 depicts the drive cone 224 with a linear triangular cross-section taper for simplicity, the disclosed configuration encompasses any spool geometry with monotonically increasing or decreasing diameter along its length to tailor the torque-turn relationship, including nonlinear profiles such as hyperbolic, parabolic, or stepped variations that match a prescribed spring torque curve or adjust the cable force to a desired output profile (e.g., linear ramp-up for progressive overload exercises). The helical grooves 226, visible in cross-section as spiraling channels, maintain uniform cable seating at each radius (e.g., Y0 or Y1), preventing slippage at force points F0 and F1 during dynamic pulls up to 100 lb. Under load, user tension at F1 rotates the drive cone 224 clockwise (by way of example), torquing the drive cone shaft 234 and winding engaged power springs in the power spring enclosures 240-246, with the ventilation slots 126 of the housing 104 facilitating heat dissipation from frictional buildup at the increased radius. Upon release, the combined spring forces rewind the cable 302 along the grooves 226, restoring the moment arm to Y0 at the apex 222 for compact storage. This design enhances exercise consistency, such as in rows or presses, by minimizing perceived force fluctuations, while the modular assemblies allow profile adjustments via spring swaps or cone redesigns accessed through the spring casing 208 or access door 107.

FIG. 7 illustrates yet another example of a resistance training device 700 in accordance with various embodiments described herein. As shown in FIG. 7, the resistance training device 700 can include a housing body 702 that includes, for example, a spring assembly chamber 704, a transmission chamber 706, a cable chamber 708, and/or a mounting anchor 710. The spring assembly chamber 704 can house one or more spring assemblies 712 and/or spring selectors 713 as described herein. In accordance with various embodiments described herein, the one or more spring assemblies 712 can assert a retraction force that is applied to a cable spool 714, which can be housed within the cable chamber 708. The spring assembly 712 can be coupled to the cable spool 714 via a transmission 716 housed within the transmission chamber 706.

FIGS. 8A-8E illustrates example arrangements of one or more spring assemblies 712 that can be housed within the spring assembly chamber 704 of the resistance training device 700 of FIG. 7, according to one or more embodiments described herein. FIG. 8A illustrates a torsion spring arrangement 802 of the spring assembly 712. FIG. 8B illustrates a power spring arrangement 804 of the spring assembly 712. FIG. 8C illustrates a compression spring arrangement of the spring assembly 712. FIG. 8D illustrates a long torsion spring arrangement 806 of the spring assembly 712. FIG. 8E illustrates a spring-loaded hydraulic piston arrangement 808 of the spring assembly 712.

In some examples, a cable 906 can be wrapped around a cable spool 902 within grooves 906 of the cable spool 902, as shown in FIG. 9. In yet some examples, the cable spool 902 can correspond to the drive cone 224 of FIG. 2. Thus, in some examples, the core torque transmission assembly 201 can include a cable spool as the drive cone 224. As a user pulls the cable 906 from the cable chamber 708, the cable spool 904 can be rotated, and a rotational force can be translated to the spring assembly 712 via the transmission 716. For example, rotation of the cable spool 714 can translate to an unwinding of one or more springs of the spring assembly 712. As the spring (e.g., a constant torque spring or power spring) tries to return to its wound state, the spring exerts a force on the cable spool 714, via the transmission 716, that biases the cable spool 714 to retract the cable 906 to the cable chamber 708. The force exerted on the cable spool 714 to bias the retraction of the cable 906 can be referred to as a retraction force in some examples.

In accordance with various embodiments described herein, the spring assembly 712 can exert a substantially constant retraction force. For instance, the retraction force can be the result of respective power springs selectively engaged or disengaged depending on the travel of the cable. In another instance, the retraction force can be the result of one or more constant torque springs which can have a substantially uniform distribution of stress in the material of the spring. Thus, the amount of force applied to the cable spool 714 by the spring assembly 712 (e.g., the retraction force) can remain substantially (or about) constant throughout the extraction of the cable 906 from the cable chamber 708. For example, in one or more embodiments, the cable 906 can have a length ranging from, for example, 1 foot to 15 feet, and the retraction force can remain within a ten percent variation margin throughout the travel of the cable 906.

In some examples, the transmission 716 can transfer a resistance force exerted by the user to the spring assembly 712 to overcome the retraction force. In one or more embodiments, the transmission 716 can modify a relationship between the rotation of the cable spool 714 and the wind/unwinding of the springs of the spring assembly 712, referred to herein as the spool-to-spring relationship. The transmission 716 can enable a user to designate a resistance level from a plurality of predefined settings. For instance, the transmission 716 can enable a user to select a resistance level from 10 possible options. Each respective resistance level is associated with a respective modification to the spool-to-spring relationship. Further, each modification to the spool-to-spring relationship can be associated with a respective resistance force that must be exerted by the user throughout the extension of the cable 906 to overcome the retraction force.

In some examples, the transmission 716 can function as a force multiplier, where the amount of force multiplication varies depending on the resistance level set by the user of the resistance training device 700. For instance, at a first resistance setting, the amount of force required to pull the cable 906 from the cable chamber 708 can be 2.5 pound-force (e.g., the resistance force that must be exerted by the user is 2.5 pound-force to unspool the cable 906). At a second resistance setting, the amount of force required to pull the cable 906 from the cable chamber 708 can be 5 pound-force (e.g., the resistance force that must be exerted by the user is 5 pound-force to unspool the cable 906). At the first and second resistance settings, the spring assembly 712 can exert the same amount of retraction force. Yet, the transmission 716 can serve as a higher force multiplier at the first resistance setting than at the second resistance setting. As such, the amount of resistance force required by the user to overcome the retraction force and unspool the cable 906 is less at the first resistance setting than the second resistance setting. In yet some examples, in both resistance settings, the retraction force, and thereby the minimum required resistance force, remains substantially constant throughout the extension of the cable 906 from the cable chamber 708, as the gear selector's adjustment of a spool-to-spring relationship (e.g., via predefined ratios) ensures the retraction force stays consistent (within about 5% in some examples) at each user-selected level across a full range of motion.

In some examples, the transmission 716 can enable a plurality of resistance settings, ranging from, for example, 2 to 15 predefined resistance settings. Further, the difference in required resistance force between each setting can range from, for example, 1 to 10 pound-force. In some embodiments, the change in required resistance force can be consistent between each resistance setting (e.g., the difference between each sequential resistance setting can be 3 pound-force). In some embodiments, the change in a desired resistance force can vary between resistance settings (e.g., the difference between a first and second sequential resistance setting can be 3 pound-force, while the difference between a third and fourth sequential resistance setting can be 5 pound-force). In various embodiments, the resistance setting can be adjusted via an adjustment mechanism (e.g., a shifter, adjustment wheel, switch, digital interface, a combination thereof, and/or the like) accessible on, for example, the housing body 702.

FIG. 10 illustrates an example of an in-line gear transmission 1000 that can be housed within the transmission chamber 706. In some examples, the in-line gear transmission 1000 can correspond to the transmission 716 of FIG. 7. As shown in FIG. 10, the in-line gear transmission 1000 can include a gear train 1002 that includes a series of gears that can be selectively engaged by a gear selector 1004 based on the resistance setting. For example, the gear train 1002 can comprise a plurality of spur or helical gears arranged coaxially or in mesh to provide stepped gear ratios, enabling variable mechanical advantage between input from the spring assembly 712 and output to the cable spool 714. The gear selector 1004 can include sliding forks, collars, or synchronizers that shift to couple selected gears in the train, adjusting the effective gear ratio to correspond to the desired resistance level while minimizing backlash or engagement shock. For example, FIG. 10 depicts an example adjustment mechanism 1020 in which a user can move a shifter 1006 between a plurality of predefined locations across the in-linear gear transmission chamber 1000, such as detent positions along a shift rail, with each predefined location associated with a respective resistance setting and resulting in the engagement of a respective gear on the gear train 1002 by the gear selector 1004. In some examples, the shifter 1006 can be a lever or dial ergonomically accessible from the exterior of the housing body 702, providing tactile feedback via notches or springs to confirm selection and prevent inadvertent shifts during use. In some examples, the in-line gear transmission 1000 can include an anti-overtravel mechanism 1030 configured to prevent excessive overrun or reverse rotation of the gear train 1002 during rapid retraction or load release, for instance, by incorporating a one-way clutch, sprag bearing, or ratcheting pawl that allows unidirectional torque flow from the spring assembly 712 to the cable spool 714 while inhibiting backlash-induced trailing that could cause cable slack or jamming. The anti-overtravel mechanism 1030 can be positioned at an intermediate or output stage of the gear train 1002, ensuring smooth, controlled retraction even under high-speed unwinding of the springs. In some examples, an output spool 1040 can be coupled to the terminal end of the gear train 1002, serving as a drive interface to the cable spool 714 or drive cone.

FIG. 11 illustrates an example of a continuously variable transmission 1100 that can be housed within the transmission chamber 706. In some examples, the continuously variable transmission 1100 can correspond to the transmission 716 of FIG. 7. As shown in FIG. 11, the continuously variable transmission 1100 can utilize a series of pulleys 1102 to vary the effective gear ratio. For example, the pulleys 1102 can include a driver pulley 1102a and a driven pulley 1102b, each composed of conical halves that face each other to form a variable-diameter sheave. For each pulley 1102, one of the conical halves can remain fixed while the other is movable, such that the movable half shifts toward or away from the fixed half along an I/O shaft 1108 to adjust the effective diameter (e.g., increasing or decreasing). The I/O shafts 1108 can include an input shaft coupled to the cable spool 714 via the driver pulley 1102a for receiving user-applied torque and an output shaft coupled to the spring assembly 712 via the driven pulley 1102b for transmitting retraction torque, with the shafts journaled by bearings for low-friction coaxial rotation. As the movable half of the driver pulley 1102a moves toward the fixed half, the diameter of the driver pulley 1102a can increase; simultaneously, the movable half of the driven pulley 1102b can move away from its fixed half, decreasing the driven pulley's diameter to maintain belt tension and optimize the gear ratio. The position of the movable halves of the pulleys 1102 can be controlled via an adjustment mechanism 1110, for example, a user-turnable dial whose rotation actuates a cam or screw drive to synchronously shift the halves along the I/O shafts 1108. To ensure consistent belt engagement without slippage, a tensioner mechanism 1104, such as an idler arm with a spring-loaded roller, can apply dynamic pressure to a belt loop, while a tension cam lever 1106 provides fine cam-actuated adjustment for preload, compensating for thermal expansion or wear in the belt during operation. The driver pulley 1102a can be coupled to the cable spool 714, and the driven pulley 1102b can be coupled to the spring assembly 712, such that as the diameter ratio between the pulleys 1102 changes, the mechanical advantage varies, modifying the resistance force needed by the user to overcome the spring retraction while preserving near-constant output torque across the cable's extension range. Thus, a substantially uniform resistance can be delivered and encountered when extending the cable, where a variable effective gear ratio (via adjustable pulley diameters) maintains force consistency (e.g., within 5% in some examples) at user-selected levels throughout the full range of motion.

In some embodiments, the transmission 716 can include a variable force compensator cone, having, for example, a tapered or conical shape with a gradually increasing/decreasing diameter along its length. For example, as shown in FIG. 9, a flexible element (e.g., a belt, cord, cable, chain, and/or the like) corresponding to the cable 904 can be coupled to the cable spool 714 and routed over a compensator cone in some instances corresponding to the cable spool 904. Rotation of the cable spool 714 can move the flexible element along the tapered surface of the compensator cone, thereby the effective tension or force applied to the flexible element is variable. In one or more embodiments, the variable force compensator cone can adjust the tension on the flexible element in relation to torque variations of the spring assembly 712 as one or more springs are unwound. In some examples, the variable force compensator cone can be implemented to ensure smooth operation and/or consistent retraction force, where the spring assembly 712 exerts variable force as the springs unwind. In one or more embodiments, the transmission 716 can include a variable force compensating cone in conjunction with the spring assembly 712 that utilizes power springs (e.g., a plurality of power springs, such as five power springs) and a spring selector.

FIG. 12 illustrates an example of a mounting configuration, where the resistance training device 1212 corresponds to the resistance training device 100 of FIGS. 1A-1B or 700 of FIG. 7 can be mounted to a door jamb 1210. In some embodiments, the mounting anchor 710 of FIG. 7 can interface with one or more mounting attachments to facilitate hand-held or mounted operation of the resistance training device 1212. For instance, the resistance training device 1212 can include one or more (e.g., two) mounting anchors 1220, each of which can interface with a hook-shaped mounting attachment. In some examples, the mounting anchors 1220 correspond to the anchor cleats 114 of the device 100 of FIGS. 1A-1B. In yet some examples, the mounting attachments (or the anchor cleats 114) can be positioned around a side of the door jamb 1210. In one or more embodiments, each mounting attachment can be tightened (e.g., the hook shape can be adjustable) around a support structure, can be fastened to the support structure, and/or can be anchored by a friction-fit with the support structure. Additionally, examples of mounting attachments include, but are not limited to, mounting straps and/or anchoring blocks.

In yet some examples, for the device 100 of FIGS. 1A-1B, the anchor cleats 114 can form a clamping mechanism with the adjustment mechanism 116, where the U-shaped profile of each cleat 114 hooks over the door jamb 1210, and rotation of the knob 112 advances the pads 118 via the shaft 117 to apply compressive force for secure gripping. This setup distributes load evenly across the underside longitudinal portion 142 of the housing 104, preventing slippage during high-tension pulls up to 100 lb in some examples. In some examples, the pads 118, being compressible neoprene discs, ensure non-marking contact with the door jamb 1210, accommodating thicknesses from 1 to 2 inches or more. In some examples, for the device 700 of FIG. 7, the mounting anchor 710 can similarly engage the door jamb 1210 via adjustable hooks or straps integrated into the housing body 702, providing balanced anchoring at the spring assembly chamber 704 or transmission chamber 706 ends. This modular anchoring allows quick setup in under 10 seconds, enhancing portability for home or travel use.

As illustrated in FIG. 12, a user 1202 (or a different user) positions the resistance training device 1212 securely on the door jamb 1210 before commencing an exercise routine. The user 1202, standing and/or seated as needed, extends an arm 1240 to grip a handle 1204 with a hand 1206. In some examples, the handle 1204 can be an ergonomic D-ring grip, padded loop, or quick-release attachment compatible with an eyelet at the end of a cable 1208, as shown in FIG. 12. In some examples, the handle 1204 can couple at one end to the cable 1208, which extends from the opening 120 (or cable chamber 708) of the resistance training device 1212. In some examples, the cable 1208 can be a flexible resistance cord as described herein, constructed from high-strength nylon webbing or braided steel coated in plastic for smooth retraction.

By way of example, during operation, the user 1202 pulls the cable 1208 outwardly from the resistance training device 1212 to initiate a concentric phase of a movement, such as a row, press, or curl. As the cable 1208 is pulled, the drive cone 224 (or cable spool 714) rotates synchronously with the drive cone shaft 234 (or via the transmission 716), unwinding successive layers from the helical grooves 226. This rotation transmits torque rearward through the coupler 236 to the rotary shaft 256, winding one or more engaged power springs 248-254 of the selectable power spring assembly 308. In some examples, the constant retraction assembly 304 maintains baseline tension via the spring 249, coiled around the arbor shaft 212 and coupled through the coupler 216.

The tapering geometry of the drive cone 224 increases the effective moment arm as layers unwind (e.g., for example from Y0 near the apex 222 to Y1 near the base portion 229 as shown in FIG. 5), amplifying user-applied torque to counteract nonlinear spring torque buildup. As a result, a substantially uniform retraction force biases the cable 1208 back toward the resistance training device 1212 consistently across a full range of motion, such that the user 1202 experiences uniform resistance from a starting point of the movement to a peak, where a muscle is strongest. In some examples, for the device 100, this uniformity arises from a binary cam selection via the resistance selection assembly 310, locking one or more corresponding engagement cams 262-268 to engage specific power springs for additive torque (e.g., 10-100 lb in 10 lb increments as an example), while a drive cone's frustoconical profile compensates for minor torque variations in the springs.

In some examples, the spring 249 delivers a fixed ˜5 lb preload independently, preventing slack even at zero selectable resistance. The helical grooves 226 seat the cable 1208 snugly, avoiding overrides or tangles during dynamic pulls by the hand 1206 of the user 1202. Upon reaching peak extension (e.g., 3-5 ft), the user 1202 holds or slowly releases, entering the eccentric phase where the uniform retraction force needs active muscle engagement to control return. This balanced resistance promotes enhanced muscle activation and strength gains, unlike elastic bands that peak at weakest positions.

In some examples, for the device 700, the spring assembly 712, housing constant torque springs or power springs, exerts the retraction force through the transmission 716, such as the in-line gear transmission 1000 or continuously variable transmission 1100, which adjusts the spool-to-spring relationship for predefined resistance levels. In a gear transmission example, the gear selector 1004 engages specific gears in the gear train 1002 via the shifter 1006, multiplying force from 2.5 lb to 50 lb while the anti-overtravel mechanism 1030 prevents backlash. The output spool 1040 then drives the cable spool 714 for precise, uniform retraction. In a CVT example, the pulleys 1102 vary in diameter via the adjustment mechanism 1110, with the tensioner mechanism 1104 and tension cam lever 1106 maintaining belt grip, ensuring seamless ratio changes without slippage. Regardless of transmission type, the retraction force remains within ±5-10% (in some examples) across 1-15 ft of cable travel, as the springs' uniform stress distribution couples with mechanical compensation. The user 1202 benefits from this in exercises such as seated rows, where the hand 1206 pulls the handle 1204 steadily, feeling about a consistent load from elbow flexion to full extension. Safety features, such as the pawls 209 locking selections or one-way clutches in the transmission 716, inhibit sudden snaps, protecting the user 1202 during release. In some examples, the ventilation slots 126 (or equivalent in device 700) dissipate heat from friction, preserving torque consistency over sessions and enabling substantially uniform resistance to cable extension, as a progressive increase in moment arm (e.g., from Y0 at the apex to Y1 at the base) compensates for spring torque buildup, resulting in a near-constant force profile (e.g., within +5% variation in some examples) across a full cable travel range (e.g., 3-5 feet in some examples).

In yet some examples, in a hand-held mode, without mounting, the user 1202 grips the handle 106 directly, using bodyweight for anchoring in floor-based curls. The cable 1208's eyelet enables swaps to ankle straps for leg work, expanding versatility. As such, in some implementations, full-body workout routines are supported, from rehab to high-intensity training, with a uniform force reducing injury risk by matching natural strength curves. The mounted setup on the door jamb 1210 can stabilize against pulls up to 100 lb, distributing forces via the cleats 114 or anchor 710. In some examples, quick-release attachments on the handle 1204 allow seamless transitions between different exercises, minimizing downtime for the user 1202.

In yet some examples, the mounting attachments (or the anchor cleats 114) can be positioned around a side of the door jamb 1210. In one or more embodiments, each mounting attachment can be tightened (e.g., the hook shape can be adjustable) around a support structure, can be fastened to the support structure, and/or can be anchored by a friction-fit with the support structure. Additionally, examples of mounting attachments include, but are not limited to, mounting straps and/or anchoring blocks. Further, in accordance with one or more embodiments described herein, various types of handles can be attached to the distal end of the cable 1208. Example types of handles can include, but are not limited to single or double grip handles (e.g., D-handles), rope handles, curl bar handles, straight bar handles, straps (e.g., ankle straps), pulldown bars, v-bar handles, multi-grip handles, abdominal crunch straps, cuffs, sport-specific attachments (e.g., handles shaped to mimic sports equipment), T-bar row handles, stirrup handles, a combination thereof, and/or the like.

Several aspects of the present technology are set forth in the following numbered examples.

• • Example 1. A portable resistance training device includes a housing that contains a cable spool around which a cable is at least partially wound, a spring assembly disposed within the housing and configured to exert a retraction force on the cable, and a transmission coupled between the spring assembly and the cable spool. The transmission is configured to provide substantially uniform resistance to extension of the cable throughout a range of motion of the cable.
  • Example 2. In some implementations of Example 1, the spring assembly includes one or more power springs and an additional spring configured to maintain a baseline retraction force on the cable independent of a selected resistance level, the selected resistance level adjusting an additive resistance to extension of the cable from the one or more power springs.
  • Example 3. In some implementations of Example 1, the spring assembly includes a plurality of power springs, and the housing further includes a selection mechanism configured to selectively engage one or more of the power springs, such that the substantially uniform resistance encountered when extending the cable is set at a user-selected force level.
  • Example 4: In some implementations of Example 3: the selection mechanism is configured to allow a user to select the user-selected force level from a plurality of predefined incremental force levels by operating the selection mechanism to engage a corresponding combination of the plurality of power springs.
  • Example 5. In some implementations of Examples 3 or 4, the selection mechanism includes a rotatable knob coupled to a camshaft, the camshaft supporting a plurality of engagement cams having varying numbers of cam teeth that engage corresponding engagement teeth on enclosures housing the power springs to select additive resistance to extension of the cable from the engaged power springs.
  • Example 6. In some implementations of Example 1, the transmission includes an in-line gear transmission having a gear train and a gear selector configured to engage selected gears of the gear train to adjust a gear ratio, wherein the adjusted gear ratio modifies a relationship between rotation of the cable spool and winding of the spring assembly, such that the substantially uniform resistance encountered when extending the cable is set at a user-selected force level.
  • Example 7. In some implementations of Example 1, the transmission includes a continuously variable transmission having a driver pulley and a driven pulley, each pulley having adjustable diameters controlled by an adjustment mechanism to vary an effective gear ratio that modifies a spool-to-spring relationship between rotation of the cable spool and winding of the spring assembly, such that the substantially uniform resistance encountered when extending the cable is set at a user-selected force level.
  • Example 8. In some implementations of Example 1, the transmission includes a variable force compensating cone, and the cable is routed over a tapered surface of the compensating cone to vary tension on the cable based on a position along the tapered surface, such that the substantially uniform resistance encountered when extending the cable is maintained by compensating for torque variations in the spring assembly.
  • Example 9. In some implementations of Example 1, the cable spool has a tapered frustoconical shape configured to increase an effective moment arm as the cable unwinds to compensate for variations in torque output from the spring assembly, such that the substantially uniform resistance encountered when extending the cable is provided throughout the range of motion.
  • Example 10. In some implementations of any of Examples 1-9, the housing includes at least one anchor cleat and an adjustment mechanism forming a clamping mechanism configured to secure the housing to a door frame or other support structure.
  • Example 11. A portable resistance training device includes a spring configured to exert a baseline retraction force on a cable, a plurality of power spring enclosures each housing a power spring configured to exert an incremental retraction force when engaged, a drive cone around which the cable is wound, a rotary shaft coupled to the power spring enclosures and to the drive cone via a drive cone shaft, a camshaft supporting a plurality of engagement cams having graduated numbers of cam teeth, and a selection knob coupled to the camshaft and configured to rotate the engagement cams to selectively engage their cam teeth with corresponding engagement teeth on one or more of the power spring enclosures, thereby coupling one or more of the power springs to the rotary shaft to add incremental retraction force to the baseline retraction force and provide substantially uniform resistance to extension of the cable throughout a range of motion.
  • Example 12. In some implementations of Example 11, pawls are configured to retract upon pulling of the selection knob to allow rotation of the camshaft and to re-engage upon release to lock the camshaft in a position that maintains the selected engagements of the cam teeth with the engagement teeth on the power spring enclosures.
  • Example 13. In some implementations of any of Examples 11-12, the drive cone includes two mirror-image halves assembled to form helical grooves for receiving the cable and a cylindrical cavity receiving the drive cone shaft.
  • Example 14. In some implementations of any one of Examples 11-13, the device includes a spring casing enclosing the spring and coupling to the drive cone shaft via a first coupler, and a spring pack housing enclosing the power spring enclosures and coupling to the drive cone shaft via a second coupler, the first and second couplers providing coaxial torque transmission.
  • Example 15. In some implementations of any one of Examples 11-14, the device includes a housing enclosing the spring, the power spring enclosures, the drive cone, the rotary shaft, the camshaft, and the selection knob, where the housing includes ventilation slots for dissipating heat from the power springs and drive cone during operation.
  • Example 16. In some implementations of Example 15, the housing includes at least one anchor cleat and an adjustment mechanism forming a clamping mechanism configured to secure the housing to a door frame or other support structure.
  • Example 17. A portable resistance training device includes a housing having a spring casing enclosing a spring coiled around an arbor shaft, the arbor shaft including an extension; a first coupler having a cavity receiving the arbor shaft extension and a protruding portion coupled to a first end of a drive cone shaft; a plurality of axially aligned power spring enclosures each enclosing a power spring; a rotary shaft extending through the power spring enclosures and including a protruding extension; a second coupler having a cavity receiving the rotary shaft extension and a protruding portion coupled to a second end of the drive cone shaft; the drive cone shaft extending between the first and second couplers; a drive cone at least partially enclosing the drive cone shaft; a camshaft; a plurality of engagement cams rotatably mounted on the camshaft and each including cam teeth; and a selection knob coupled to the camshaft.
  • Example 18. In some implementations of Example 17, the drive cone includes two mirror-image halves that at least partially enclose the drive cone shaft.
  • Example 19. In some implementations of any of Examples 17-18, each of the power spring enclosures includes an engagement tooth positioned to interact with the cam teeth of a corresponding engagement cam.
  • Example 20. In some implementations of any of Examples 17-19, the device includes a retractable cable at least partially helically wound around the drive cone.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the technology. As used herein, for example, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “contains”, “containing”, “includes”, “including,” “comprises”, and/or “comprising,” and variations thereof, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Terms of orientation are used herein merely for purposes of convention and referencing and are not to be construed as limiting. However, it is recognized that these terms could be used with reference to an operator or user. Accordingly, no limitations are implied or to be inferred. In addition, the use of ordinal numbers (e.g., first, second, third, etc.) is for distinction and not counting. For example, the use of “third” does not imply there must be a corresponding “first” or “second.” Also, as used herein, the terms “coupled” or “coupled to” or “connected” or “connected to” or “attached” or “attached to” may indicate establishing either a direct or indirect connection, and is not limited to either unless expressly referenced as such.

While the disclosure has described several exemplary embodiments, it will be understood by those skilled in the art that various changes can be made, and equivalents can be substituted for elements thereof, without departing from the spirit and scope of the technology. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation, or material to embodiments of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the technology is not limited to the particular embodiments disclosed, or to the best mode contemplated for carrying out this technology, but that the technology will include all embodiments falling within the scope of the appended claims. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.