Radial piston pump

A suction-restricted radial piston pump, comprising a housing having a cylindrical recess formed therein, a rotor mounted for rotation in said recess in a direction about an axis eccentric to said cylindrical recess, said rotor formed with a plurality of radial piston bores, a plurality of pistons slidably received within said piston bores of said rotor, a stroke-generating member engaging one end of each of said pistons, the other end of each of said pistons defining pumping chambers in said rotor piston bores and a fixed control pin received within said rotor, said pumping chamber each having a portion opening onto the surface of said control pin, said control pin formed with respective suction and pressure control orifices, a suction channel and a pressure channel communicating respectively with said suction and pressure control orifices, said control orifices separated by webs, with said control orifices, upon rotation of said pressure chambers in said rotor, successively communicating with said piston bores, wherein said control orifice associated with said suction connection comprises a restriction groove formed into the surface of said control pin extending circumferentially partly around said control pin, of small cross-sectional area, said restriction grooves beginning adjacent said suction-mode dead center whereat said pumping chambers are at minimum volume, a suction bore joining said restriction groove, and, with said suction bore spaced from a rotor dead center at which said pumping chambers are at maximum volume, and further including a filling groove of larger cross sectional area than said restriction groove, which supply groove extends from said suction bore towards said rotor maximum volume dead center.