Abstract: An air operated liquid pump includes a pump with a reciprocating plunger driven by a piston contained in a cylinder. The plunger is connected to and reciprocates a dispensing piston that moves between two positions relative to the plunger to open and close flow through valve holes that pass through the dispensing piston.

Abstract: An automatic air operated grease gun comprising a reciprocating grease plunger for ejecting grease, and a piston, connected to the plunger, for operating the plunger. The piston is slidably mounted in a cylinder to move between a retracted position and an advanced position. A return spring resiliently biases the piston to its retracted position. A switch selectively connects the cylinder to a source of gas under pressure to advance the piston against the return spring. The piston has a plurality of apertures therein, each aperture having an individual seal, and a release for opening the individual seals to relieve the pressure behind the cylinder and allow it to retract under the force of the return spring.