a suction - restricted radial piston pump is described , in particular for use with automotive vehicles . the pump delivers a flow constant over a broad speed range and involving low losses in output and generating only negligible noise . in one embodiment , a control slot , on the pressure side , is subdivided into several grooves which at least in part are in communication , through check valves , with the pressure connection . an alternative embodiment provides a shape of the pressure - sided control slot in which the introducing end thereof is comparatively narrow to reduce noise at a high speed and the outlet - sided end thereof with a wider width sufficient to meet the required output . according to a third embodiment , the suction - sided slot is provided with a narrow width section and a subsequent wider width section .