Abstract

A fluid operated dispensing gun for dispensing viscous material in a disposable cylindrical cartridge. The dispensing gun has a hand grip and a barrel releasably secured to the hand grip. The cartridge containing the viscous material is positioned inside the barrel of the gun and a piston-like rear wall is advanced toward the open front end of the cartridge by pressurized fluid introduced into the rear end of the barrel on the rear side of the piston-like rear wall. Fluid passageways are provided in the hand grip for providing fluid communication from a source to the rear end of the barrel. A pair of manually operated valves are provided, one valve being provided for opening and closing the fluid passageway to the rear end of the barrel and the other valve being provided for controlling the rate of flow of the fluid entering the rear end of the barrel to thereby control the rate at which the viscous material is ejected from the cartridge. An inflatable bladder is provided at the rear end of the barrel and is adapted to inflate into the cartridge in response to the introduction of pressurized fluid at the rear end of the barrel to urge the piston-like rear wall toward the outlet of the cartridge and, consequently, urge the viscous material out of the cartridge through the outlet. A bleeder hole is provided in the hand grip and cooperates with the flow rate controlling valve to bleed the air trapped in the inflatable bladder during installation of the cartridge and inflatable bladder to the dispensing gun and when the pressurized fluid is a liquid.