Incremental dispensing device

Abstract

A fluid actuated dispensing device having a valve assembly and an actuating piston provides incremental movement of a drive piston within a tube holder. The valve assembly includes a trigger piston and a valve ball biased into engagement with a valve seat. A trigger is adapted to engage the trigger piston and urge the valve ball away from its seat to allow fluid to enter an actuating chamber. The increase in fluid pressure within the chamber drives an actuating piston from an initial position to an extended position in the chamber. The actuating piston is adapted to drive a washer off-center against a push rod during the stroke of the actuating piston. The washer cocks and grabs the push rod and urges the rod forwardly within the tube holder. A drive piston connected to the push rod is thereby driven forward within the tube holder for the full stroke of the actuating piston. When the trigger is released, the fluid in the actuating chamber is exhausted through a passage in the trigger piston, which thereby reduces the pressure in the actuating chamber. The reduced pressure in the chamber allows a spring to uncock the washer and bias the washer and the actuating piston back into their initial positions, which provides for incremental movement of the push rod, and hence the drive position.