Guns intended for extruding pastry products

Claim 1

In a gun for dispensing pasty products which includes a cylinder into which compressed gas is charged and which gas passes through a piston seal member which substantially closes one end of the cylinder so that the gas is directed through a cartridge to a piston means which acts to discharge a product from a supply container through a nozzle, the improvement comprising; said piston seal member having inner and outer ends and an outer surface, said inner end being in sealing engagement with the one end of the cylinder, first and second peripheral grooves in the outer surface of said piston seal member and spaced inwardly of said outer end thereof, a first radial lip of a first diameter formed between said first groove and said outer end, a second radial lip of a second diameter which is larger than said first diameter formed between said first and second grooves, said inner end being formed as a conical skirt extending radially outwardly relative to said second groove and having a diameter greater than said second diameter, and at least one gas passage way extending through said piston seal member whereby when gas pressure is supplied to the cylinder, such pressure will act to force one of said first and second radial lips into a sealed engagement with the cartridge.