Abstract: A hydraulic displacement machine including two external gears located in the machine housing and meshing with each other, with the teeth of the two gears sealingly engaging the inner surface of the housing, and with meshing teeth of the two gears sealing the two port regions from each other, and an arrangement for communicating pressure prevailing in the port region of the housing having a higher pressure to the port region of the housing having a lower pressure over a circumference of each of the two gears.

Abstract: A gear pump or motor comprises a pair of rotary gears which are in external meshing engagement with each other. A thrust plate is pressed against the side faces of the gears by means of a plurality of pressure areas which are produced by means of a sealing and compensating unit. The unit is urged piston-like by virtue of fluid pressure chambers against the back of the thrust plate to engage it against the gears. Depending on the direction of rotation of the gears of the machine the pressure areas define the general configuration of a 3 or a .epsilon..