Composite ejecting piston with chamber

Device for dispensing a plastic mass comprising a composite piston for ejecting or dispensing the plastic mass from a substantially cylindrically-shaped receptacle wherein the improvement comprises that said composite piston includes a piston head having a central axis extending in the direction for ejecting the plastic mass from the receptacle and said piston head being axially displaceable in the receptacle, said piston head having a disc-like wall member extending transversely of the central axis and said wall member having a first face arranged to be directed against the plastic mass and an oppositely facing second face, said composite piston includes a plate-like pressure component extending transversely of the central axis and located on the second face side of said piston head, said pressure component having a first surface and a second surface extending transversely to the central axis with the first surface facing the second face of said piston head and said second surface facing in the opposite direction, said piston head and pressure component being spaced apart in the direction of the central axis for at least a part of the second face of said piston head and the first surface of said pressure component for forming a chamber therebetween, said piston head and pressure component being displaceable within the receptacle between an insertion position and a locked position, said disc-like wall member having an opening therethrough in the insertion position for flow of the mass into said chamber from the first face side of said disc-like wall member and said pressure component including means for sealing said opening in said disc-like wall member when said piston head and pressure component are in the locked position, said pressure component has at least one venting channel therethrough in communication with the ambient atmosphere in the insertion position of said piston and said venting channel being sealed by said piston head in the locked position of said composite piston.