Vane pump or motor

Claim 1

A vane pump or motor comprising a cylindrical disc rotatably arranged in a housing surrounding it, said disc having a plurality of radial grooves extending in the axial direction and regularly distributed on its circumference, said grooves being provided with radially movable vanes which, with their ends remote from the disc are guided by the inner wall of the housing, said vanes being arranged for pivotal movement within said grooves, said housing comprising at least one pair of associated inlet and outlet apertures for liquid, and means producing pressure difference across said vanes, the part of the inner wall of the housing situated between each pair of associated inlet and outlet apertures being cylindrical and having a larger diameter than the disc, said wall part also forming a boundary for a working space, said grooves in the disc being regularly distributed about the circumference thereof in such manner that the angle enclosed by radial planes passing through the center of two adjacent grooves and the axis of the disc is equal to no greater than half of the angle enclosed by two planes each passing through the axis of the disc and one of which passes through the end of the wall part of the housing forming the boundary of the working space which communicates within the inlet aperture and the other passes through the end of said wall part which communicates with the outlet aperture, equal discharge grooves provided on each cylindrical wall part which forms a boundary for a working space communicating at its ends with inlet and outlet apertures, said discharge grooves extending in the circumferential direction over a distance equal to the arc length of the cylindrical wall part diminished by twice the distance between the vanes measured on the same diameter as that of the relative wall part, said grooves being arranged so that when a vane passes thereacross the resistance to flow across said vane is substantially equal to half the resistance to flow across a vane which contacts the track of the wall part in which no discharge grooves are arranged.