Controlling system for positioning a swashplate of a multiple-piston rotary fluid pump or motor

Claim 1

In a multiple-piston rotary fluid pump or motor, a tiltable swashplate tiltable about a predetermined axis, a single servo piston means operatively connected with said swashplate for tilting the latter about said axis, said single servo piston means including a single servo piston and a cylinder in which the latter is movable, so that the angular position of the swashplate will always correspond to a given position of the single servo piston in its cylinder, a single spool valve means having a central neutral portion for providing communication between opposed ends of the cylinder of said single servo piston means and a pair of end portions one of which provides for movement of said single servo piston in one direction in said cylinder and the other of which provides for movement of said single servo piston in the opposite direction in said cylinder, manually operable means for manually setting the angular position of the swashplate, a single elongated link means having opposed ends respectively connected pivotally to said single servo piston and said manually operable means, said single elongated link means being pivotally connected intermediate its ends to said single spool valve means, so that said manually operable means may be operated to swing said single link means about its connection to said single servo piston means for displacing said single spool valve means in a direction which will bring about movement of said servo piston to adjust the angle of the swashplate while restoring said spool valve means to its neutral position where said central portion thereof provides communication between the opposed ends of said cylinder, and retaining means coacting with said manually operable means for releasably retaining the latter in the position to which it is moved by the operator, so that when a force tends to displace said swashplate from its adjusted angle the single servo piston will move to tilt the single link means about its connection to said manually operable means for displacing said spool valve means in a direction which will automatically return the single servo piston to its adjusted position and thus return the swashplate to its adjusted position.