Dispensing gun

In a fluid operated dispensing gun for dispensing a viscous material, said gun having means defining a hand grip and means defining a barrel receiving portion on which a barrel is releasably secured and wherein a disposable cylindrical cartridge containing said viscous material and formed with an outlet for dispensing said viscous material therefrom has a rear cylindrical rim and is equipped with a piston-like rear wall, said viscous material being located between said piston-like rear wall and said outlet, said cartridge being positioned inside said barrel of said gun for advance of said piston-like rear wall of said cartridge toward said outlet by pressurized fluid introduced into the rear end of said barrel on the rear side of said piston-like rear wall, the improvement comprising:

• fluid passageway means in said hand grip means and said barrel receiving portion for providing a fluid passageway to said rear end of said barrel;
• first manually operated valve means on said hand grip means and in said fluid passageway means for opening and closing said fluid passageway means;
• second manually operated flow rate control valve means on said barrel receiving portion and in said fluid passageway means between said first valve means and said rear end of said barrel and being independent of said first manually operated valve means for controlling the rate of flow of said fluid through said fluid passageway means and said rear end of said barrel to thereby control the rate at which said piston-like rear wall is advanced toward said outlet and the rate at which said viscous material is ejected from said outlet;
• and
• a bleeder hole in said barrel receiving portion providing fluid communication between said rear end of said barrel and the atmosphere, said fluid communication being controlled by said second manually operated valve means.