Patent ID: 6923348

Claim:
A pump for dispensing a fluid comprising a pneumatic reciprocating motor, a dispenser, and a reciprocal plunger driven by said motor; wherein said motor comprises: a motor cylinder having a head end and a rod end; a motor piston reciprocable in the cylinder, said motor piston having a forward and a back side, said motor piston being reciprocable through a forward stroke toward the rod end of the cylinder and a return stroke back toward the head end and being biased to return back through a return stroke; said plunger extending forward from the motor piston through the rod end of the cylinder and being reciprocable by the motor piston; said cylinder having an air inlet for admission of compressed air thereto on the back side of the motor piston for driving it forward through a forward stroke against the return bias and an air outlet on the forward side of the motor piston for venting air; said motor piston having through passaging extending from its forward side to its back side; a valve movable in the motor piston relative to the motor piston between a position blocking said through passaging and a position unblocking said through passaging; said cylinder and motor piston having auxiliary passaging for delivery of air under pressure from the back side of the motor piston to move the valve to its said through-passaging-unblocking position at the conclusion of a forward stroke of the motor piston, the motor piston acting as a valve and opening said auxiliary passaging at the conclusion of the forward stroke of the motor piston; and wherein said dispenser comprises: a dispensing chamber; a dispensing piston in the dispensing chamber and supported by the plunger for reciprocal movement in response to reciprocal movement of the plunger, the dispensing piston being further moveable relative to the plunger between a charge position for charging the dispensing chamber with fluid and a discharge position for discharging fluid from the dispensing chamber.