Self-flushing piston assembly for slurry pump

摘要

A slurry pump is provided having a self-flushing piston assembly mounted in a mating cylinder. The piston assembly includes a first piston having a peripheral sealing member and a reciprocating piston rod for driving the first piston for pumping action. A second piston mounted adjacent to the first piston includes a sealing member and forms an enclosed chamber with the first piston. A lost motion coupler connects the pistons together and varies the size of the chamber. On the return stroke of the piston assembly, flushing liquid on the non-slurry side is sucked into the chamber as the chamber expands. On the power stroke, the flushing liquid is forced past the second sealing member to remove slurry particles and prevent wear of the cylinder. The disc on the first piston has sufficient flexibility to allow filling of the chamber and an accumulator is provided to control the back pressure after the chamber has been filled on the return stroke. The flexible sealing discs are mounted by retainer plates and the lost motion coupler includes a hollow carrier mating with a shoulder on the rod for limited reciprocating movement.