Abstract: A hydraulic pump including a pressure chamber, a drain passage communicable with the pressure chamber, a delivery port, a discharge path fluidly connecting the pressure chamber with the delivery port, and an orifice disposed in the discharge path. A first flow control valve is provided for variably controlling fluid communication between the pressure chamber and the drain passage in response to a difference between fluid pressures upstream and downstream of the orifice. A second flow control valve is disposed within the discharge path, which is operative to variably control an opening area of the orifice in response to energy of fluid passing through the discharge path. The second flow control valve includes a moveable spool exposed to a fluid pressure within the pressure chamber, a spring biasing the spool in such one direction as to increase the opening area of the orifice, and a spring retainer cooperating with the spool to define a spring chamber accommodating the spring.

Abstract: A pump comprising a pump body having a control valve for controlling working fluid flow from the pump body to an actuator through a joint. The joint is connected mechanically to the pump body through a washer made of a material different from that of the pump body. The washer has a side surface held in contact with the pump body at a junction. The pump also includes an annular seal member provided to keep the junction from exposure to the environment. In an embodiment of the invention, the seal member is placed in an annular groove formed in the outer peripheral surface of the pump body. The seal member may have a side surface in fluid-sealing contact with the surface of the washer so as to keep the junction between the pump body and the washer from exposure to the environment.

Abstract: A pump comprising a pump body having a control valve for controlling working fluid flow from the pump body to an actuator through a joint. The joint is connected mechanically to the pump body through a washer made of a material different from that of the pump body. The washer has a side surface held in contact with the pump body at a junction. The pump also includes an annular seal member provided to keep the junction from exposure to the environment. In an embodiment of the present invention (FIG. 7), an annular member is provided between the pump body and the washer, with the annular member being made of an insulating material to prevent electrical conduction between the pump body and the washer.

Abstract: A pump comprising a pump body having a control valve for controlling working fluid flow from the pump body to an actuator through a joint. The joint is connected mechanically to the pump body through a washer made of a material different from that of the pump body. The washer has a side surface held in contact with the pump body at a galvanic junction. The pump also includes an annular seal member provided to keep the junction from exposure to the environment.