Rotary positive displacement pump - has segment-shaped piston elements rotated at variable speed by cranks on eccentric shaft

摘要

Pump has segment-shaped rotary piston elements and a cylindrical housing with two or more pistons (4,8) whose included angle is less than 360 deg. divided by the number of pistons. The pistons rotate at variable speed such that the space between the flanks of two neighbouring pistons is at maximum volume when presented to the inlet port and fully closed when passing the outlet port. The piston segments may be driven by rollers (19,20) on cranks (6,14) which rotate about an axis eccentric relative to the axis of piston rotation, whilst the rollers engage radial grooves (3,13) provided in the end faces of the pistons or of discs (2,12) connected with the pistons.