Caterpillar Inc.

Dale B Childress

Noah D Manring

Charles Earl Rose

A variable margin pressure control for a variable displacement load sensing pump comprises a body having a bore therein and a valve spool slidably disposed in the bore defining a chamber in continuous communication with a discharge passage in the body. The valve spool is movable in a first direction for communicating the discharge passage with a control port in the body and in a second direction for communicating the control port with an exhaust flow path. The valve spool is biased in the first direction by discharge fluid pressure in the chamber. A spring mechanism biases the valve spool in the second direction against the force generated by the discharge pressure with a biasing force sufficient to establish a predetermined margin pressure. A remotely controllable variable biasing force is applied against the valve spool by a device so that the margin pressure can be selectively varied in response to receiving a pressure signal. Another devices applies a load pressure generated biasing force against the valve spool in the second direction so that the margin pressure is maintained throughout the pressure operating range of the pump.

Variable margin pressure control

A swash plate actuating device for an axial piston unit has a swash plate tiltably mounted within the housing. A pair of axially aligned actuating chambers defined in the housing slidably receive the opposite ends of an elongate actuator and are disposed on opposite sides of a distal end portion formed on an actuator lever connected to the swash plate. A connector has a mounting portion spanning a transverse slot in the actuator and seated on a planar surface of the actuator. A guide portion of the connector is disposed within the transverse slot and has a bearing slot slidably receiving the distal end portion of the actuator lever.

Swash plate actuating device for axial piston pumps and motors

A pump displacement control for a variable displacement pump includes a torque control valve disposed between a variable torque limiter and a force applying device disposed in axial alignment within a common bore. A sleeve and a valve spool are movable relative to each other to establish a first condition communicating discharge pressure into an actuator chamber to move a swashplate toward a minimum displacement position against the bias of a spring or a second condition communicating the actuating chamber with an exhaust passage to allow the spring to move the swashplate toward its maximum displacement position. A torque control piston disposed between opposing springs resiliently bias the valve spool in a direction to establish the second condition when control fluid is directed into a control chamber. Pump discharge pressure communicated into a pressure chamber exerts a force against the valve spool proportional to the discharge pressure so that the valve spool moves in a second direction to establish the first condition when the control force exceeds the biasing force exerted by the torque limiter.

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Plainfield, IL, United States of America

Dale B Childress