Pomp for supplying fluid to a system.

摘要

The disclosure relates to a cheek plate unloading pump for supplying fluid to a system. The pump has a discharge port concentric with its axis of rotation. The pump includes a rotor, a cam encircling said rotor and means for effecting relative rotation of the cam and rotor about an axis. A plurality of vanes are carried by the rotor and engage the cam to define pumping pockets which expand and contract on rotation of the rotor. A cheek plate extends radially of the axis and is disposed adjacent one axial side of the rotor and cam. The cheek plate is movable along the rotational axis to communicate expanding and contracting pumping pockets. ¡There is a cavity on one side of the cheek plate, and a fluid passage conducts fluid pressure into the cavity which fluid pressure biases the cheek plate into a position blocking the flow of fluid from the contracting pumping pockets to the expanding pumping pockets. The pump also includes a servo valve for venting the pressure in the cavity to thereby control the flow of fluid between the contracting and expanding pumping pockets. A fluid passage in the cheek plate receives flow from the contracting pockets. The passage has a portion directing flow from the contracting pumping pockets radially inwardly of the cheek plate. A tubular member is fixedly attached to the cheek plate coaxially with the axis of relative rotation of the rotor, and the interior of the tubular member communicates with the portion of the fluid passage directing flow radially inwardly. A housing member defines a chamber in which the cam ring, rotor and cheek plate are located, and the housing has a discharge orifice coaxial with the tubular member. A seal is provided between the tubular member and the housing member enabling the tubular member to move with the cheek plate relative to the housing member while maintaining the seal. A droop in the output flow rate is achieved by a variable control orifice which is in part defined by a tapered surface on the tubular member. As the cheek plate and tubular member move away from the cam and rotor, the tapered surface moves to decrease the size of the control orifice. This, in turn, decreases the pressure acting on one end of the servo valve spool and further reduces the output flow of the pump, thereby causing the desired droop.