Radial piston pumps or motors

Claim 1

A radial piston type pump or motor comprising a housing, a rotor including a disc portion within the housing and a shaft projecting from the housing, said disc portion being formed with a plurality of radial bores and with transverse passages communicating with said bores respectively and opening onto one face of said disc portion a plurality of pistons slidable respectively in said bores, a cam in the housing operatively related to the pistons to reciprocate the pistons in said bores as the rotor is rotated and high and low pressure ports in the housing into communication with which the passages are successively brought as the rotor is rotated the housing being formed with first and second recesses in communication with the high pressure pot, said first recess being disposed adjacent the shaft at a position axially spaced from the disc portion and has an effective area such that high pressure fluid therein applies a radial force to the shaft equal and opposite to a radial foRce applied to the rotor by high pressure fluid in said bores said radial forces having parallel lines of action spaced by a first distance from one another, said second recess being disposed adjacent a face of the disc portion opposite that on to which the transverse passages open and having an effective area such that high pressure fluid therein applies to the disc portion an axial force equal and opposite to an axial force applied thereto by high pressure fluid in the passages and the high pressure port at a position diametrically opposite the high pressure port with respect to axis of the rotor, so that the axial forces have lines of action spaced by a second distance, and the product of the effective area of the first recess and the first distance being equal to the product of the effective area of the second recess and the second distance so that the moments of the equal and opposite forces applied to the rotor are equal and opposite.