Abstract: A high-pressure rotary fluid-displacing machine is described which is suitable for use as a motor or pump. It comprises a housing, an internally toothed annular gear, an externally toothed pinion arranged eccentrically within said annular gear and intermeshing therewith, an engagement-free crescent-shaped gap being left between the addendum circles of the pinion and of the annular gear, respectively, on the side thereof opposite the contact point of the pitch circle of the pinion with the pitch circle of the annular gear, a shaft bearing the pinion and being adapted for transmitting torque, and a gap-filling member in the gap having an inner and an outer curved surface, the inner surface being sealingly contacted by the addendum surfaces of the teeth of the pinion, and the outer surface being sealingly contacted by the addendum surfaces of the teeth of the annular gear.

Abstract: A hydrostatic gear machine is described which comprises a pair of gear wheels meshing with one another, one of the gear wheels being an internally toothed annular gear wheel and the other an externally toothed pinion, the tooth profile of at least one of said wheels being at least substantially trochoidal; the tooth profile of a first one of the two wheels being defined as being obtained by rolling the first wheel with meshing on the other wheel. The teeth of at least one of said wheels bear the thus defined profile only on a limited zone having a length just sufficient for the ratio of the angles of rotation of the two wheels to be constant throughout rotation of the wheels, and have their profile set back, outside the said limited zone, by a sufficient distance to eliminate contact, outside the limited zone, with the teeth of the other gear wheel.

Abstract: A method for grinding the tooth flanks of a roughed-out, annular, internally-toothed gear wheel wherein the pitch circle of the internally-toothed gear wheel is rotated about or rolled off a fixed circle having a diameter equal to the pitch circle of an externally-toothed pinion, adapted to mesh with the finished internally-toothed gear wheel; and, simultaneously with the rotation of the gear wheel, a grinding wheel is rotated on an axis parallel to the plane of the gear wheel, is reciprocated through the interior of the gear wheel along an axis parallel to the axes of the pitch circle of the gear wheel and the fixed circle and maintained a fixed distance from the axis of the fixed circle, except for normal infeed, and has a circumferentially-disposed grinding surface whose cross-sectional profile is equivalent to the profile of at least a part of the profile of at least one tooth of the pinion; the ratio of the diameter of the fixed circle to the diameter of the pitch circle of the gear wheel being an aliqua