High pressure hydraulic gear pump or motor

In a high pressure hydraulic gear pump of the type having a housing with a main bore accommodating therein a pinion surrounded by and cooperating with an internal gear ring, and a curved filler member occupying at least that end sector of the sickle-shaped space between the pinion and the internal gear ring where the gear teeth converge and in which the pressure space of the pump is located, in such a gear pump, the combination comprising:

• a radially movable sealing plate interposed between at least one of the two peripheral surfaces of the filler member and the associated gear periphery, at a short circumferential distance from the converging gear teeth, the sealing plate having a curved outer surface in alignment with said associated gear periphery and bearing against the gear teeth which move along said gear periphery;
• a shallow radial recess in the filler member, for the accommodation therein, with a small circumferential clearance, of the sealing plate;
• means for positioning the sealing plate in the circumferential sense in relation to the filler member, said positioning means including a circumferentially forwardly facing abutment flank on the rear side of said radial recess;
• means for biasing the sealing plate radially away from the filler member, towards said moving gear teeth, said biasing means including a pressure fluid space defined between the filler member and the sealing plate and channel means bringing pressurized fluid to said pressure fluid space, when the pump is in operation, said biasing means further including spring means engaged between the filler member and the sealing plate, for the creation of a radial bias which is also present when the pump is in a pressureless state;
• and
• means for positioning and abutting the filler member in the circumferential sense, against its inherent operative tendency of backing away from the converging, pressure generating gear teeth, at least that portion of the filler member which cooperates with the sealing plate being likewise radially movable, so that, under the influence of said sealing plate biasing means, the sealing plate bears at all times against one gear, while the filler member bears against the other gear, thereby taking up any changes in gear position due to manufacturing tolerances, or resulting from operational wear and displacements, under changing temperatures and pressures.