IDENTIFYING THE SWEET SPOT OF A BAT

Description

TECHNICAL FIELD

The subject matter of this disclosure is generally related to test equipment, and more particularly to analyzing bats used in bat-and-ball games.

BACKGROUND

It is well known that bats have an optimal point of contact for maximizing transfer of kinetic energy from the bat to a ball. That optimal point of contact, generally known as the “sweet spot,” is located on the barrel section of a baseball bat in the space between Node 1 and Node 2. Node 1 is the place closest to the end of the bat barrel where Mode 1 and Mode 2 intersect and Node 2 is the next intersecting point of Mode 1 and Mode 2 moving in a direction away from the barrel end of the bat in a direction closer to the handle. The precise location of the sweet spot varies between bats and can be difficult to identify. Center of percussion techniques identify the sweet spot as the location at which a perpendicular impact against a bat attached to a pivot point along the length of the bat does not generate a reactive shock at that pivot point. The absence of reactive shock occurs when the translational and rotational motions cancel at the pivot point. Barrel-end node of the first bending mode of vibration techniques identify the sweet spot based on finding Node 1 directly. U.S. Pat. No. 5,672,809 issued to Brandt describes using a gas cannon to propel a ball into a bat. The velocity prior to impact and the rebound velocity following impact are used to calculate the coefficient of restitution of the bat. Published United States Patent Application 2009/0221388 of Giannetti describes a modified baseball bat that includes a housing for a sensor, processor, and audible and optical feedback means integrated into the body of the bat at the tapered transition between the handle and the barrel. The sensor is located proximate to the antinode of the bat to identify contact with the sweet spot based on maximum peak acceleration. Unites States U.S. Pat. No. 11,717,733 issued to Carr, which is incorporated by reference, describes a test fixture for identifying the sweet spot of a bat suspended in a vertical orientation via a fixed pivot point with rotational movement limited to a single plane.

SUMMARY

Some aspects of the presently disclosed invention may be predicated in part on recognition that there is a need to be able to quickly and accurately analyze bats to identify their sweet spots in places such as sporting goods stores and team clubhouses at which hitting balls and swinging bats is impractical.

In accordance with some implementations an apparatus for analyzing a bat characterized by a handle, a barrel and a transition, comprises: at least one vibration absorber adapted to inhibit gross movement of the bat and quiesce oscillatory vibration of the bat; an accelerometer adapted to sense acceleration at the handle of the bat; and an impact mass adapted to strike a plurality of locations on the barrel of the bat.

In accordance with some implementations a method of identifying a sweet spot of a bat characterized by a handle, a barrel and a transition, comprises: striking the bat at a series of locations along the barrel of the bat; measuring maximum acceleratory response to each strike at the handle of the bat; quiescing oscillatory vibration of the bat and inhibiting gross movement of the bat with at least one vibration absorber; and identifying the sweet spot based on the location corresponding to minimum of the maximum acceleratory responses.

All examples, aspects, implementations, and features mentioned in this disclosure can be combined in any technically possible way. Other aspects, features, and implementations may become apparent in view of the detailed description and figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a front view of an apparatus for identifying the sweet spot of a bat.

FIG. 2 is a side view of the apparatus of FIG. 1.

FIG. 3A is a side view of the vibration absorber cuff.

FIG. 3B is a top view of the vibration absorber cuff.

FIG. 3C is a cross-section view of the vibration absorber cuff of FIG. 3B taken along A-A.

FIG. 4A is a side view of the vibration absorber cap.

FIG. 4B is a top view of the vibration absorber cap.

FIGS. 4C and 4D are implementations shown as cross-section views of the vibration absorber cap of FIG. 4B taken along B-B.

FIG. 5A illustrates response to a single impact.

FIG. 5B illustrates response to a series of impacts and identification of the sweet spot.

FIG. 6 illustrates the apparatus configured to analyze a bat mounted vertically with the barrel end up and the knob resting against a vibration absorber cap.

FIGS. 7A, 7B, and 7C illustrate alternative implementations in which the types and positions of vibration absorbers differ.

FIGS. 8A and 8B illustrate implementations in which the accelerometer is integrated into a vibration absorber.

FIG. 9 illustrates a method for identifying the sweet spot of a bat.

DETAILED DESCRIPTION

Although the invention will be described in the context of testing baseball bats, the invention is not limited to test equipment for baseball bats. The inventive concepts could be applied to testing of bats for a wide variety of bat-and-ball sports and non-bat sports equipment that is used for striking an object. Further, the inventive concepts are not limited to wooden bats and can be applied to bats made of aluminum and other materials.

Some aspects, features, and implementations described herein may include machines such as computers, electronic components, optical components, and processes such as computer-implemented procedures and steps. It will be apparent to those of ordinary skill in the art that the computer-implemented procedures and steps may be stored as computer-executable instructions on a non-transitory computer-readable medium. Furthermore, it will be understood by those of ordinary skill in the art that the computer-executable instructions may be executed on a variety of tangible processor devices, i.e., physical hardware. For practical reasons, not every step, device, and component that may be part of a computer or data storage system is described herein. Those of ordinary skill in the art will recognize such steps, devices, and components in view of the teachings of the present disclosure and the knowledge generally available to those of ordinary skill in the art. The corresponding machines and processes are therefore enabled and within the scope of the disclosure.

Referring to FIGS. 1 and 2, a baseball bat 100 exhibits diametrical symmetry around a center axis 101. The diameter of the bat varies along the length dimension of the bat between distal ends. The section of the bat known as the barrel 108 exhibits the greatest diameter, and the handle 102 of the bat exhibits the smallest diameter. The diameter of the transition 110 section decreases from a location proximate to the barrel to a location proximate to the handle. A knob 103 at the distal end of the bat adjacent to the handle 102 has a greater diameter than the handle. A batter grips the bat at the handle 102 with both hands when hitting a ball. The sweet spot is located somewhere along the barrel 108 of the bat but the precise location of the sweet spot is unique to each individual bat. The test apparatus disclosed herein functions to quickly analyze a bat to identify the sweet spot based on the minimum of maximum acceleration measured at the handle 102 as the bat is struck at various locations along the barrel 108. The apparatus advantageously analyzes the bat without the need to hit a ball or swing the bat, so it is suitable for use in places such as sporting goods stores and team clubhouses.

The test apparatus shown in FIGS. 1 and 2 includes a base 112, vibration absorber cuff 104, vibration absorber cap 106, an impact mass 114, motors 116, a controller 118, a display 120, and an accelerometer 122. The bat is mounted to the test apparatus via the vibration absorbers 104, 106, both of which are vibration isolators that are attached to the base 112. The base may include a cabinet or rigid sheet of material that fixes positions of the vibration absorbers relative to each other. The vibration absorbers 104, 106 are configured to align the center axis 101 of the bat perpendicular with a first linear axis 10 of strike travel of the impact mass 114 and parallel with a second linear axis 12 of relocation travel of the impact mass. The accelerometer 122 is attached to the handle 102 of the bat where the hands of the batter will be located during batting, e.g., centered on the location where the right and left hands touch. The motors 116 are configured to linearly move the impact mass 114 in the first linear axis 10 to strike the bat with a predetermined force and to linearly move the impact mass in the second axis 12 to change the location of impact along the barrel between successive strikes. The controller 118, which may include a single board computer with a microprocessor, memory, and peripheral board, controls the motors 116 to cause the impact mass to strike the bat at predetermined distance increments along the barrel of the bat in rapid succession while measuring responsive vibration as acceleration at the handle of the bat using the accelerometer. The controller identifies the sweet spot of the bat based on the measured acceleration values and presents the results on the display 120. Further, the controller causes the location of the sweet spot to be marked on the bat, e.g., with an adhesive sticker or ink. The vibration absorbers are not drawn to scale and the illustrated dimensions are not limiting.

In the illustrated example the bat is mounted vertically with the barrel end down during analysis, but this is not a limitation. The bat may be mounted in any of a wide variety of orientations. In the specifically illustrated implementation the distal end of the barrel of the bat is placed against vibration absorber cap 106, which supports the weight of the bat against the base 112 and inhibits gross (non-vibrational) movement of the bat at the barrel 108. The vibration absorber cuff 104 holds the bat in the vertical orientation relative to the base and inhibits gross movement of the bat at the transition 110. The vibration absorber cuff 104 may be adapted to be repositioned along the base in order to locate the vibration absorber cuff at a section of the transition 110 with a suitable diameter to be gripped by the vibration absorber cuff. In response to being struck by the impact mass 114, the bat 100 exhibits oscillatory vibration but does not exhibit gross movement because gross movement of the bat is inhibited by the vibration absorbers 104, 106. Further, the vibration absorbers decrease the amount of time it takes to quiesce oscillatory vibration, i.e., they accelerate quiescence of oscillatory vibration. Inhibiting gross movement of the bat and accelerating quiescence of oscillatory vibration between strikes helps to reduce the time delay between successive impacts, which facilitates quicker analysis of the bat and enables a greater number of impacts to be completed within a given period of time, thereby improving the precision of identification of the location of the sweet spot without increasing testing time. In some implementations, gross movement and oscillatory vibration cease before repositioning of the impact mass is completed.

FIGS. 3A, 3B and 3C illustrate a cylindrical vibration absorber cuff 104 with open ends. An annular or cylindrical vibration damping layer 300 is disposed within a rigid collar 302, e.g., attached thereto with adhesive. The vibration damping layer may include resilient foam, rubber, cork, polyurethane, polyvinyl chloride, and combinations thereof. The collar and vibration damping layer are split into halves that are linked by a hinge 304. A latch 306 enables the collar 302 to be opened when necessary and secured in a closed position during tests. The collar is unlatched and opened to receive the bat to be analyzed and subsequently latched to cause the vibration damping layer to establish continuous 360-degree circumferential contact with the adjacent surface of the bat during analysis.

FIGS. 4A, 4B, 4C, and 4D illustrate a cylindrical vibration absorber cap 106 with a single open concave end defined by an opening 400 characterized by a spherical cap, spherical segment, conical, or truncated conical shape. A vibration damping layer 402 is disposed within a rigid receiver 404, e.g., attached thereto with adhesive. The vibration damping layer may include resilient foam, rubber, cork, polyurethane, polyvinyl chloride, and combinations thereof. The rigid receiver 404 is cylindrical and includes a sidewall 406, an enclosed bottom 408, and an open top. The vibration damping layer 402 fits against the sidewall 406 and bottom 408 of the receiver and includes a concave curved opening 400 that defines a void that is shaped as a spherical cap or spherical segment as shown in FIG. 4C, or a cone or truncated cone as shown in FIG. 4D, for receiving either the barrel end or knob of the bat. More specifically, the barrel end or knob of a bat sits within the curved top section (opening 400) during analysis. The varying cross sectional diameter of the concave curved top section of the vibration damping layer facilitates alignment and mounting of bats of different sizes and diameters.

FIG. 5A illustrates vibrational response to a single impact as sensed by the accelerometer. The vibrational response of the bat is oscillatory and decays over time. The magnitude of maximum acceleration 500 is recorded by the controller. The next successive impact is implemented after oscillatory vibrations quiesce. As shown in the figure, the vibration absorbers reduce the time to quiescence of oscillatory vibration relative to an implementation that does not include vibration absorbers. The vibration absorbers also inhibit gross movement of the bat, which in some prior art techniques can take longer to quiesce than the oscillatory vibrations. It will be understood by those of ordinary skill in the art that a human being is incapable of accurately measuring or accurately comparing the oscillatory vibrations described herein.

FIG. 5B illustrates vibrational response to a series of impacts and identification of the sweet spot. The recorded maximum acceleration values are plotted against their respective strike locations on the bat, which correspond to elevation of the impact mass. The minimum of the maximum acceleration values 502 is indicative of the sweet spot 504. The strike location corresponding to the minimum of the maximum acceleration values may be selected as the sweet spot. Alternatively, a curve may be fitted to the maximum acceleration values and the strike location corresponding to the minimum of the curve may be selected as the sweet spot.

FIG. 6 illustrates the apparatus configured to analyze a bat mounted vertically with the barrel end up and the knob 103 resting against a first vibration absorber cap 106. A second vibration absorber cap 106 receives the barrel end of the bat. The accelerometer 122 is attached to the handle of the bat as previously described. The test apparatus functions according to the same principles described with regard to the previous example. However, two vibration absorber caps 106 are used rather than one vibration absorber cap and one vibration absorber cuff, so the gross-movement counter-forces are applied to the bat at different locations than in the previous example. The vibration absorbers are not drawn to scale and the illustrated dimensions are not limiting.

FIGS. 7A, 7B, and 7C illustrate alternative implementations in which the types and positions of vibration absorbers differ. FIG. 7A illustrates an implementation in which a vibration absorber cap 106 is in contact with the barrel end of the bat and a vibration absorber cuff 104 is in contact with the transition of the bat. FIG. 7B illustrates an implementation in which a vibration absorber cap 106 is in contact with the knob of the bat and a vibration absorber cuff 104 is in contact with the transition of the bat. FIG. 7C illustrates an implementation in which a first vibration absorber cap 106 is in contact with the knob of the bat and a second vibration absorber cap 106 is in contact with the barrel end of the bat. In all of the illustrated implementations the accelerometer is attached to the handle of the bat. The vibration absorbers are not drawn to scale and the illustrated dimensions are not limiting.

FIGS. 8A and 8B illustrate implementations in which an accelerometer is integrated into a vibration absorber cuff 800. The vibration absorber cuff 800 is attached to the handle if the bat. As shown in FIG. 8A, the vibration absorber cuff 800 may be used with a vibration absorber cuff 104 attached to the transition of the bat. As shown in FIG. 8B, the vibration absorber cuff 800 may be used with a vibration absorber cap 106 in contact with the barrel end of the bat.

FIG. 9 illustrates a method for identifying the sweet spot of a bat. Step 600 is striking the bat with an impact mass at a series of locations along the barrel of the bat. In some implementations the strike points are between a first vibration absorber and a second vibration absorber. Step 602 is quiescing oscillatory vibration of the bat and inhibiting gross movement of the bat with a first vibration absorber. This may be a cap, cuff, or cuff/accelerometer combination. Step 604 is quiescing oscillatory vibration of the bat and inhibiting gross movement of the bat with a second vibration absorber. This may be a cap, cuff, or cuff/accelerometer combination. Oscillatory vibration of the bat is quiesced between successive strikes. Step 606 is measuring the maximum acceleratory response to each strike at the handle of the bat using an accelerometer. Step 608 is selecting the impact location corresponding to the minimum of the maximum acceleratory responses as the sweet spot. As previously explained, a curve may be fitted to the measured values and the sweet spot selected from the curve rather than a single measurement. Step 610 is marking the location of the sweet spot on the bat. This may include applying an adhesive sticker to the bat or marking the bat with ink.

Specific examples have been presented to provide context and convey inventive concepts. The specific examples are not to be considered as limiting. A wide variety of modifications may be made without departing from the scope of the inventive concepts described herein. Moreover, the features, aspects, and implementations described herein may be combined in any technically possible way. Accordingly, modifications and combinations are within the scope of the following claims.