The field of art to which the invention relates includes motors and pumps, and more especially fixed displacement fluid motors and pumps.
It has long been a problem in the art to which this invention pertains to effectively disengage during certain modes of operation of fluid motors and pumps of the type contemplated, the cam track and pistons such that during high speed free-wheeling operation, for example, of the motor or pump the pistons are held in inactive retracted positions without engaging the driving cam surface at any point in the rotary cycle of operation, thereby both protecting the motor or pump from damage as a result of the pumping action of the pistons at excessive rpm, and minimizing the wear and tear of parts associated with reciprocating parts. Heretofore, to my knowledge, no fully satisfactory means has been devised for effectively operating at high speed, fixed displacement fluid motors or pumps while holding the pistons thereof in fixed inoperative positions.
In the use of hydrostatic wheel motors in certain types of vehicles, such as an off-the-road construction type tractor vehicles, for example, it is often necessary to tow the vehicle on highways from one work location to another. Heretofore in certain applications highway towing speeds have been relatively low in order to minimize wear and tear on parts such as pistons, cylinders and bearings, and so that the motors were not damaged or destroyed by high speed towing operation beyond the design limits of the motors.
Again, in operating certain types of cable winches it is desirable, for example, to disengage the winch drive from time to time in a high speed cable pull-off operation. My invention is adapted to effectively disengage such a winch drive motor to stop the piston action which would otherwise occur. Also, for example, it is frequently desirable to accelerate a fly wheel to a relatively high speed to store energy, subsequent to which the fly wheel speed and energy is conserved by minimizing losses. During such fly wheel acceleration powered by the engaged drive motors it is then desirable to disengage the pistons by holding them in retracted positions, and following fly wheel acceleration to conserve fly wheel speed and energy and then extract the stored energy as needed from time to time by reenergizing the pistons when drawing power from the flywheel.
Fixed displacement camming ball or roller radial or axial piston type air compressor motors, steam engines and pumps may be used in a variety of applications in which the kind of problem indicated above exits. My invention may be applied to all such exemplary types of fluid motors or pumps to provide overspeed protection, and/or reduce wear and tear on the motor or pump under certain operational modes, and/or minimize the noise and heat losses generated in such modes of operation.