Pneumatic reciprocating motor and grease gun incorporating same

A pump comprising a pump tube having an inlet for material being pumped and an outlet through which said material is discharged, and a pump plunger reciprocable in the pump tube, said pump plunger being constituted at least in part by a piston rod of a pneumatic reciprocating motor, said motor comprising:

• 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 piston rod 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.

A grease gun comprising:

• a handle;
• a motor cylinder on the handle having a head end and a rod end;
• a pump tube extending forward from the rod end of the cylinder;
• a container holding grease under pressure for supplying the pump tube carried by the gun;
• 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;
• a piston rod constituting at least one part of a pump plunger extending forward from the motor piston through the rod end of the cylinder into the pump tube 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;
• a hand-operated valve for controlling said admission of compressed 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 passaging at the conclusion of the forward stroke of the motor piston.