DOUBLE ACTING PISTON PUMP.

摘要

A piston pump which includes a seal formed by a valve member inside a cylinder with an end zone through which extends a fluid entry port, and wherein a piston rod is movable in a forward direction into a recess in the valve member, thereby to apply fluid pressure and then mechanical pressure to the valve member to displace the valve member into sealing engagement with end zone, and in a reverse direction to reduce pressure inside the recess thereby to unseat the valve member from the zone.