Hydraulic piston pump having distribution through a bi-directional port plate

A hydraulic piston pump of the type having a plurality of pistons sliding in bores formed in a barrel mounted in rotation in a casing of the pump, said barrel bearing against a distribution port plate borne by a cylinder head, said distribution port plate being provided with two symmetrical crescents serving alternately as a suction crescent and a delivery crescent according to the direction of rotation of the pump, in which the cylinder head is provided with two drainage channels placing an inner space of the casing in respective communication with two suction/delivery orifices of said cylinder head;

• each drainage channel being provided with a valve, wherein the valve has in each case a compression spring housed in the drainage channel so as to maintain the valve in an open position by default, the valve being able to close the drainage channel in response to an overpressure in the suction/delivery orifice such that, according to the direction of rotation of the pump, the inner space of the casing is in communication through one of the drainage channels with the suction line;
• whereas the communication through the other drainage channel between the delivery side and the inner space of the casing is closed.