Override control for a variable displacement pump

Claim 2

An override control, for a variable displacement axial piston pump having a fluid discharge port, comprising; an angularly adjustable swash plate movable between minimum and maximum displacement positions for determining pump displacement; an actuator system in fluid communication with the fluid discharge port for controlling the position of said swash plate as a function of pump discharge pressure during pump operation but adapted to urge the swash plate toward its maximum displacement position when the pump is not in operation; means providing a passage connecting the fluid discharge port of the pump with the actuator system; a manually actuated pump; a conduit connecting said manually actuated pump to said passage; an accumulator connected to said conduit and adapted to receive and store pressurized fluid from said manually actuated pump; a manually operable control valve disposed within said conduit between said accumulator and said passage, said control valve being actuatable between a closed and an open position for selectively controlling communication between said accumulator and the actuator system to override the actuator system causing it to shift the swash plate to its minimum displacement position when the variable displacement pump is not in operation; a first check valve dispoSed within said passage between the fluid discharge port and the actuator system for blocking flow of fluid from said manually actuated pump to the fluid discharge port; and a second check valve disposed in said conduit for blocking flow of fluid from the fluid discharge port to said manually actuated pump.

Claim 3

An override control, for a variable displacement axial piston pump having a fluid discharge port, comprising; an angularly adjustable swash plate movable between minimum and maximum displacement positions for determining pump displacement; pressure responsive means in fluid communication with such fluid discharge port for urging said swash plate toward its minimum displacement position; a servo-mechanism in fluid communication with the fluid discharge port for controlling the swash plate position as a function of discharge pressure during pump operation; resilient means coacting with said servo-mechanism for biasing the swash plate to its maximum displacement position in the absence of pump discharge pressure; means providing a passage connecting the fluid discharge port with said pressure responsive control means and said servo-mechanism; a manually actuated pump; a conduit connecting said manually actuated pump to said passage; an accumulator connected to said conduit and adapted to receive and store pressurized fluid from said manually actuated pump; a manually operable control valve disposed within said conduit between said accumulator and said passage, said control valve being actuatable between a closed and an open position for selectively controlling communication through said conduit simultaneously to said servo-mechanism for actuating it to a venting condition and to said control means causing it to move the swash plate to its minimum displacement condition against the bias of said resilient means when the variable displacement pump is not in operation; a first check valve disposed in said passage between the fluid discharge port and the pressure responsive control means for blocking fluid flow from said manually actuated pump to the fluid discharge port; and a second check valve disposed in said conduit for blocking flow of fluid from the fluid discharge port to said manually actuated pump.

Claim 4

An override control, for a variable displacement axial piston pump having a fluid discharge port, comprising; an angularly adjustable swash plate movable between minimum and maximum displacement positions for determining pump displacement; pressure responsive means in fluid communication with such fluid discharge port for urging said swash plate toward its minimum displacement position; a servo-mechanism in fluid communication with the fluid discharge port for controlling the swash plate position as a function of discharge pressure during pump operation; resilient means coacting with said servo-mechanism for biasing the swash plate to its maximum displacement position in the absence of pump discharge pressure; means providing a passage connecting the fluid discharge port with said pressure responsive control means and said servo-mechanism; a manually actuated pump; a conduit connecting said manually actuated pump to said passage; an accumulator connected to said conduit and adapted to receive and store pressurized fluid from said manually actuated pump; a manually operable control valve disposed within said conduit between said accumulator and said passage, said control valve being actuatable between a closed and an open position for selectively controlling communication through said conduit simultaneously to said servo-mechanism for actuating it to a venting condition and to said control means causing it to move the swash plate to its minimum displacement condition against the bias of said resilient means when the variable displacement pump is not in operation; a first check valve disposed in said passage between the fluid discharge port and the pressure responsive control means for blocking fluid flow from said manually actuated pump to the fluid discharge port; and a second check valve disposed in said conduit for blocking flow of fluid from the fluid discharge port to said manually actuated pump.