Abstract: The invention relates to a rotary piston pump comprising a housing (10), an annular piston (18) in the form of a tubular segment, which is connected to a shaft (22) in a rotationally fixed manner and which is guided rotationally and displaceably in an annular chamber (28, 10) of the housing, said chamber being coaxial with the shaft (22). The rotary piston pump also comprises at least one inlet and one outlet which are configured in the housing in such a way that the inlet or outlet on the annular chamber side are located inside an axial area of a surface area of the annular chamber, said surface area being determined by the maximum axial distance of the wave troughs of the end surfaces that face each other.

Abstract: The invention relates to a rotary piston machine, comprising a housing (10) and a piston (12) which is situated in a hollow area of the housing (10) in such a way that it can rotate and which is rotationally fixed to a shaft (18) that passes through the housing (10). At least one inlet channel and at least one outlet channel for guiding a working fluid in or out of the hollow area are configured in the housing (10). According to the invention, the hollow area has a section which is configured in the form of a cylindrical ring cavity that is coaxial to the shaft (18). The piston (12), as a ring piston, is configured in the form of a cylindrical tubular section which engages in the ring cavity of the housing (10) and is axially displaceably guided in said ring cavity. The end surfaces (20,26) of the ring cavity and the ring piston (12) facing away towards each other are configured as constant wavy surfaces with an axially parallel amplitude.