MULTI- ENGINE HYDRAULIC-DRIVE POWER TROWEL

Description

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Application 63/625,255 filed Jan. 25, 2024, which is fully incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present application relates generally to power trowels, and more specifically to speed control for ride-on power trowels powered by multiple engines.

Description of Related Art

Ride-on power trowels for finishing newly poured concrete surfaces are well known in the art. A general design for such apparatus is disclosed, for example, in U.S. Pat. No. 8,708,598 owned in common by the present applicant and incorporated herein by reference. A ride-on power trowel typically has two rotors, each with multiple blades that extend radially from the rotor axis so that the working edge of each blade lies in a plane perpendicular to the rotor axis and generally parallel to a concrete surface to be finished. The combined rotor blade diameters define a total troweling width or path width. The rotors may be driven by electric, mechanical or hydraulic drive motors that are ultimately powered by an internal combustion engine. The engine, drive motors, rotors, various subsystems, subcomponents, operator seat and operator controls are mounted to or otherwise supported by a rigid frame that rides on and is steered by the rotor blades. Ride-on power trowels can be generally classified according to operating weight as light-duty (under 1000 lbs), medium duty (1000 to 2000 lbs), or heavy duty (over 2000 lbs). Generally, trowel operating weight is proportional to the troweling width.

For any size power trowel, the engine and other components of the engine system contribute significantly to the overall weight. But when scaling a design from a lighter duty machine to a heavier duty machine, the operating weight tends to increase nonlinearly in an exponential fashion. Larger blades require a more powerful power train, and as each power train component and subcomponent is scaled up, more size and weight is added such that a larger and heavier frame is needed to support the heavier duty parts. Regulatory requirements can exacerbate this problem. For example, additional subsystems for exhaust treatment (catalytic converters, exhaust gas recirc, diesel exhaust fluid, etc.) must be added to the engine when horsepower ratings reach certain thresholds. These subsystems add to manufacturing and operating costs, by increasing the overall weight and complexity of the trowel, and by introducing additional failure modes, failure effects, and maintenance concerns.

What is needed is an innovation in power trowel systems that will allow for more efficient scaling.

SUMMARY OF THE INVENTION

The present invention provides a significant advancement in the design of power trowels that enables a more linear scaling of the design for heavier duty machines with minimal effect on overall weight and system complexity. Principles of the invention are disclosed herein in non-limiting fashion in the context of a twin-engine hydraulically driven ride-on power trowel, with the understanding that the inventive principles apply equally to any configuration of a multi-engine power trowel, whether it may include more than two engines or two or more non-identical engines.

In one embodiment, a ride-on power trowel according to the present invention includes the following essential components: a rigid frame, first and second engines mounted to the rigid frame, and a first hydraulic drive loop having a first hydraulic pump powered by the first engine and a first drive motor powered by the first hydraulic pump. Also provided is a second hydraulic drive loop having a second hydraulic pump powered by the second engine and a second drive motor powered by the second hydraulic pump. First and second rotor assemblies are coupled respectively to the first and second drive motors and configured to contact a concrete surface beneath the rigid frame. A means for feedback control is provided for setting rotor speed in each rotor assembly to a power limited speed based on loads sensed in the drive loops. The power limited speed is an estimated maximum rotor speed achievable for the highest sensed load. In one variation, the power limited speed may be affected by operating data received by the feedback controller from the engine associated with the highest sensed load.

The feedback control means may include a first means for sensing rotor load in the first hydraulic drive loop, and a second means for sensing rotor load in the second hydraulic drive loop. The feedback control means may be configured to set the rotor speed in each rotor assembly based on the loads sensed in the hydraulic drive loops.

In another embodiment of the aforesaid trowel, the means for determining the power limited speed may include a controller, such as a programmable logic controller, that is configured to receive from the first means a first load signal representing load in the first hydraulic drive loop and to receive from the second means a second load signal representing load in the second hydraulic drive loop. The controller may be further programmed or configured to determine a first speed from the first load signal and to determine a second speed from the second load signal. In one implementation, the controller determines the first speed from the first load signal and the second speed from the second load signal using a lookup table. In a preferred embodiment, the controller may be further configured to determine the power limited speed as the lowest value of the first speed and the second speed. The power limited speed may be further affected by engine operating data, for example a CAN bus signal, received by the controller from the first engine or the second engine.

In other variations of the invention, in the hydraulic drive loops, one or both of the means for sensing load may comprises a pressure transducer, a torque sensor, or a fuel consumption monitor. In another embodiment, one or both of the means for sensing load may comprise a CPU or controller that is mounted locally on the power trowel and that is configured to receive a signal from an engine control unit (ECU) associated with one or both of the first and second engines. For example, the locally mounted controller may be configured to receive data via CAN bus protocol and the ECU may be an OEM-configured controller mounted on one or both engines.

Another embodiment of the invention provides for a ride-on power trowel that includes the following salient features: a rigid frame, a first power train mounted to the rigid frame and comprising a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor. Also included are a second power train mounted to the rigid frame and comprising a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor. The first and second rotor assemblies are configured with finishing blades for contacting a concrete surface beneath the rigid frame, thereby supporting the frame above the surface while rotating the blades to move the trowel about the surface while finishing the structure and appearance of the surface.

A more elaborate embodiment of the aforesaid trowel may further include the following additional components: a means for sensing a first load on the first hydraulic pump, a means for sensing a second load on the second hydraulic pump, and control means configured to generate, responsive to receiving the sensed first load and the sensed second load, a control signal causing a change in speed of at least one of the first and second drive motors. In one implementation, the generated control signal may be based on a comparison of the sensed first load to the sensed second load. In another implementation, the generated control signal represents slowest speed between a first power limited speed associated with the sensed first load and a second power limited speed associated with the sensed second load. In another implementation, the generated control signal causes speed of the first drive motor to be substantially equal to speed of the second drive motor.

Another embodiment of the invention provides a method for controlling rotor speed of a hydraulically driven trowel, which method includes the following salient steps performed by an automatic controller, such as a programmable logic controller executing instructions stored in memory, for (i) receiving a first load signal representing load in a first hydraulic loop having a first hydraulic pump that provides power to a first rotor; (ii) receiving a second load signal representing load in a second hydraulic loop having a second hydraulic pump that provides power to a second rotor; (iii) determining a first power limited rotor speed associated with the first load signal and a second power limited rotor speed associated with the second load signal; (iv) comparing the first power limited rotor speed to the second power limited rotor speed to determine an adjustment to an operator-desired rotor speed; and (v) transmitting a command to drive both the first rotor and the second rotor at the operator-desired rotor speed plus or minus the adjustment. In one embodiment, a power limited rotor speed is an estimated maximum rotor speed achievable for a sensed load, may be determined by the controller reading a lookup table. In other embodiments, a power limited rotor speed may be determined as a function of the received load signals by means of the controller executing a mathematical algorithm.

In a variation of the foregoing method, further steps are provided for (a) receiving, at the controller, first operating data from a first engine mechanically coupled to the first hydraulic pump; (b) receiving, at the controller, second operating data from a second engine mechanically coupled to the second hydraulic pump; and (c) transmitting, by the controller, the command to drive both the first rotor and the second rotor at a command speed derived from one or more of (i) the operator-desired rotor speed, (ii) the adjustment, and (iii) the first operating data, and (iv) the second operating data. One or both of the first operating data and the second operating data may be received as a CAN bus signal.

In related methods of the invention, a power limited rotor speed for either rotor may be a maximum rotor speed achievable by the rotor under the highest load. In another embodiment, power limited rotor speed may be defined according to empirical test data that defines a maximum safe operating rotor speed achievable by a rotor at the load represented by the load signal. In any of the foregoing embodiments, a system according to the invention sets all rotor speeds for the ride-on trowel to the lowest power limited rotor speed determined from the comparison between the first and second power limited rotor speeds. In any of the foregoing embodiments, the command signal transmitted by the controller may achieve desired rotor speeds by causing a change in stroke angle of a swash plate in one or both the first hydraulic pump and the second hydraulic pump. In any of the foregoing embodiments, the first or second load signal may be derived from pressure sensed in a hydraulic loop, from torque sensed in a drive train component of the trowel, from an indication of the rate of fuel consumption, or from a signal received from an engine control unit associated with an engine that serves as a prime mover for the first hydraulic drive loop or for the second hydraulic drive loop.

In another embodiment, a ride-on power trowel according to the invention is constructed on and supported by a rigid frame. A first power train is mounted to the rigid frame and includes a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor and configured to contact a concrete surface beneath the frame. A second power train is also mounted to the rigid frame and includes a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor and configured to contact the concrete surface beneath the rigid frame. A programmable controller is mounted to the power trowel and programmed to limit speed of the first drive motor and speed of the second drive motor according to a power limited rotor speed of whichever one of the first drive motor and the second drive motor is under heavier load. The power limited rotor speed may be determined according to a lookup table that maps hydraulic pressure to rotor speed. The controller may be further configured to adjust the power limited rotor speed according to a feedback-controlled trimming algorithm. The trimming algorithm may provide a positive adjustment or a negative adjustment to the power limited rotor speed. In the aforesaid embodiment, the programmable controller may determine a stroke control command for the first drive motor and for the second drive motor as a function of both feed-forward control and feedback control. The feed-forward control may comprise the lookup table that maps hydraulic pressure to rotor speed, and the feedback control may compare one or more feedback signals representing speed of one or both of the first drive motor and the second drive motor to an operator set point.

Broadly described, another embodiment of the invention provides a ride-on power trowel having multiple engines, multiple hydraulic motors, and multiple trowel rotors, wherein each of the engines is configured to drive only one of the hydraulic motors, and wherein each of the hydraulic motors is configured to drive only one of the trowel rotors. A controller mounted to the power trowel is programmed to limit speed of all of the hydraulic motors according to a power limited speed of whichever one of the hydraulic motors is under heaviest load.

BRIEF DESCRIPTION OF THE DRAWINGS

Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. Component parts shown in the drawings are not necessarily to scale, and may be exaggerated to better illustrate the important features of the invention. Dimensions disclosed or shown are exemplary only. In the drawings, like reference numerals may designate like parts throughout the different views, wherein:

FIG. 1 is a perspective view of one embodiment according to the invention for a multi-engine hydraulic-drive power trowel.

FIG. 2 is a top view of the multi-engine trowel of FIG. 1.

FIG. 3 is a block diagram of one embodiment of a control scheme for the multi-engine trowel of FIG. 1.

FIG. 4 is a graph of a speed-pressure curve for a hydraulic drive loop on the multi-engine trowel of FIG. 1, under a first operating condition.

FIG. 5 is a graph of a speed-pressure curve for a hydraulic drive loop on the multi-engine trowel of FIG. 1, under a second operating condition.

FIG. 6 is a block diagram of a scheme for power management and speed control for a multi-engine trowel according to one embodiment of the invention.

FIG. 7 is a block diagram of a scheme for power management and speed control for a multi-engine trowel according to another embodiment of the invention.

FIG. 8 is a block diagram of a scheme for power management and speed control for a multi-engine trowel according to another embodiment of the invention.

FIG. 9 is a block diagram of a control scheme for power management for a multi-engine trowel according to one embodiment of the invention.

FIG. 10 is a block diagram of one embodiment of the invention for a feed-forward control scheme for controlling rotor speed in a multi-engine trowel.

FIG. 11 is a graph representing one embodiment of an experimentally determined lookup table for mapping hydraulic pressure to rotor speed to optimize performance of a multi-engine trowel according to a control scheme of the present invention.

FIG. 12 is a block diagram of a control scheme for power management and speed control for a multi-engine trowel according to another embodiment of the invention.

FIG. 13 is a block diagram of a control scheme for power management and speed control for a multi-engine trowel according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention overcomes the aforesaid scaling difficulties for ride-on power trowels by disclosing design schemes for a multi-engine ride-on power trowel. Throughout the disclosure, designs for such a trowel are presented using a dual-engine or twin-engine design as a primary example of a multi-engine trowel, though the invention is by no means limited to a ride-on power trowel having only two engines or having two identical engines. The disclosed multi-engine solution introduces additional design challenges regarding power management and speed control. Accordingly, the disclosure also addresses these considerations and proposes novel solutions.

As used throughout the drawings and disclosure, the abbreviations have the following meanings: ECU (engine control unit); E (engine); HCU (hydraulic control unit); S1 (speed of first hydraulic motor; S2 (speed of second hydraulic motor); L (left-hand or first power train); R (right-hand or second power train); P1 (pressure in first hydraulic circuit); P2 (pressure in second hydraulic circuit); LH (left-hand); RH (right-hand); Engine Operating Setpoint (a programmer-selected data point or data provided by CAN bus, for example, a maximum load value or an RPM value; OP (operator); TPS % (percentage of maximum throttle position); ENG (engine); MACH (hydraulic machine or system); PM (power management); % OUT (command signal); CMD (command); PRES. (pressure).

The invention is described in greater detail in the drawings labeled FIGS. 1 to 13 that accompany this disclosure. In one embodiment, a ride-on power trowel according to the present invention includes the following essential components: a rigid frame, first and second engines mounted to the rigid frame, and a first hydraulic drive loop having a first hydraulic pump powered by the first engine and a first drive motor powered by the first hydraulic pump. Also provided is a second hydraulic drive loop having a second hydraulic pump powered by the second engine and a second drive motor powered by the second hydraulic pump. First and second rotor assemblies are coupled respectively to the first and second drive motors and configured to contact a concrete surface beneath the rigid frame. A means for feedback control is provided for setting rotor speed in each rotor assembly to a power limited speed based on loads sensed in the drive loops. The power limited speed is an estimated maximum rotor speed achievable for the highest sensed load. In one variation, the power limited speed may be affected by operating data received by the feedback controller from the engine associated with the highest sensed load.

The feedback control means may include a first means for sensing rotor load in the first hydraulic drive loop, and a second means for sensing rotor load in the second hydraulic drive loop. The feedback control means may be configured to set the rotor speed in each rotor assembly based on the loads sensed in the hydraulic drive loops.

In another embodiment of the aforesaid trowel, the means for determining the power limited speed may include a controller, such as a programmable logic controller, that is configured to receive from the first means a first load signal representing load in the first hydraulic drive loop and to receive from the second means a second load signal representing load in the second hydraulic drive loop. The controller may be further programmed or configured to determine a first speed from the first load signal and to determine a second speed from the second load signal. In one implementation, the controller determines the first speed from the first load signal and the second speed from the second load signal using a lookup table. In a preferred embodiment, the controller may be further configured to determine the power limited speed as the lowest value of the first speed and the second speed. The power limited speed may be further affected by engine operating data, for example a CAN bus signal, received by the controller from the first engine or the second engine.

In other variations of the invention, in the hydraulic drive loops, one or both of the means for sensing load may comprises a pressure transducer, a torque sensor, or a fuel consumption monitor. In another embodiment, one or both of the means for sensing load may comprise a CPU or controller that is mounted locally on the power trowel and that is configured to receive a signal from an engine control unit (ECU) associated with one or both of the first and second engines. For example, the locally mounted controller may be configured to receive data via CAN bus protocol and the ECU may be an OEM-configured controller mounted on one or both engines.

Another embodiment of the invention provides for a ride-on power trowel that includes the following salient features: a rigid frame, a first power train mounted to the rigid frame and comprising a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor. Also included are a second power train mounted to the rigid frame and comprising a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor. The first and second rotor assemblies are configured with finishing blades for contacting a concrete surface beneath the rigid frame, thereby supporting the frame above the surface while rotating the blades to move the trowel about the surface while finishing the structure and appearance of the surface.

A more elaborate embodiment of the aforesaid trowel may further include the following additional components: a means for sensing a first load on the first hydraulic pump, a means for sensing a second load on the second hydraulic pump, and control means configured to generate, responsive to receiving the sensed first load and the sensed second load, a control signal causing a change in speed of at least one of the first and second drive motors. In one implementation, the generated control signal may be based on a comparison of the sensed first load to the sensed second load. In another implementation, the generated control signal represents slowest speed between a first power limited speed associated with the sensed first load and a second power limited speed associated with the sensed second load. In another implementation, the generated control signal causes speed of the first drive motor to be substantially equal to speed of the second drive motor.

Another embodiment of the invention provides a method for controlling rotor speed of a hydraulically driven trowel, which method includes the following salient steps performed by an automatic controller, such as a programmable logic controller executing instructions stored in memory, for (i) receiving a first load signal representing load in a first hydraulic loop having a first hydraulic pump that provides power to a first rotor; (ii) receiving a second load signal representing load in a second hydraulic loop having a second hydraulic pump that provides power to a second rotor; (iii) determining a first power limited rotor speed associated with the first load signal and a second power limited rotor speed associated with the second load signal; (iv) comparing the first power limited rotor speed to the second power limited rotor speed to determine an adjustment to an operator-desired rotor speed; and (v) transmitting a command to drive both the first rotor and the second rotor at the operator-desired rotor speed plus or minus the adjustment. In one embodiment, a power limited rotor speed is an estimated maximum rotor speed achievable for a sensed load, may be determined by the controller reading a lookup table. In other embodiments, a power limited rotor speed may be determined as a function of the received load signals by means of the controller executing a mathematical algorithm.

In a variation of the foregoing method, further steps are provided for (a) receiving, at the controller, first operating data from a first engine mechanically coupled to the first hydraulic pump; (b) receiving, at the controller, second operating data from a second engine mechanically coupled to the second hydraulic pump; and (c) transmitting, by the controller, the command to drive both the first rotor and the second rotor at a command speed derived from one or more of (i) the operator-desired rotor speed, (ii) the adjustment, and (iii) the first operating data, and (iv) the second operating data. One or both of the first operating data and the second operating data may be received as a CAN bus signal.

In related methods of the invention, a power limited rotor speed for either rotor may be a maximum rotor speed achievable by the rotor under the highest load. In another embodiment, power limited rotor speed may be defined according to empirical test data that defines a maximum safe operating rotor speed achievable by a rotor at the load represented by the load signal. In any of the foregoing embodiments, a system according to the invention sets all rotor speeds for the ride-on trowel to the lowest power limited rotor speed determined from the comparison between the first and second power limited rotor speeds. In any of the foregoing embodiments, the command signal transmitted by the controller may achieve desired rotor speeds by causing a change in stroke angle of a swash plate in one or both the first hydraulic pump and the second hydraulic pump. In any of the foregoing embodiments, the first or second load signal may be derived from pressure sensed in a hydraulic loop, from torque sensed in a drive train component of the trowel, from an indication of the rate of fuel consumption, or from a signal received from an engine control unit associated with an engine that serves as a prime mover for the first hydraulic drive loop or for the second hydraulic drive loop.

In another embodiment, a ride-on power trowel according to the invention is constructed on and supported by a rigid frame. A first power train is mounted to the rigid frame and includes a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor and configured to contact a concrete surface beneath the frame. A second power train is also mounted to the rigid frame and includes a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor and configured to contact the concrete surface beneath the rigid frame. A programmable controller is mounted to the power trowel and programmed to limit speed of the first drive motor and speed of the second drive motor according to a power limited rotor speed of whichever one of the first drive motor and the second drive motor is under heavier load. The power limited rotor speed may be determined according to a lookup table that maps hydraulic pressure to rotor speed. The controller may be further configured to adjust the power limited rotor speed according to a feedback-controlled trimming algorithm. The trimming algorithm may provide a positive adjustment or a negative adjustment to the power limited rotor speed. In the aforesaid embodiment, the programmable controller may determine a stroke control command for the first drive motor and for the second drive motor as a function of both feed-forward control and feedback control. The feed-forward control may comprise the lookup table that maps hydraulic pressure to rotor speed, and the feedback control may compare one or more feedback signals representing speed of one or both of the first drive motor and the second drive motor to an operator set point.

Broadly described, another embodiment of the invention provides a ride-on power trowel having multiple engines, multiple hydraulic motors, and multiple trowel rotors, wherein each of the engines is configured to drive only one of the hydraulic motors, and wherein each of the hydraulic motors is configured to drive only one of the trowel rotors. A controller mounted to the power trowel is programmed to limit speed of all of the hydraulic motors according to a power limited speed of whichever one of the hydraulic motors is under heaviest load.