Positive displacement pumps.

摘要

A pump comprises a casing (15) and a rotor (26) rotatably mounted on a pintle (24) fixed in the casing (15). The rotor (26) has four cylinder bores (32) angularly spaced by 90 DEG in which ball elements (33) are slidably and sealingly disposed. A cam track (35) formed in the casing (15) encircles the rotor (26) and causes the balls (33) to reciprocate as the rotor (26) rotates, and the inner ends of each cylinder bore (32) comes into communication alternately with inlet and outlet apertures (38, 40) in the pintle (24) to produce a flow of the working fluid. The profile of the cam track (35) is arranged so that the sum of the inward velocities of each two adjacent balls (33) during their delivery strokes is constant.