Viscous material dispenser with vented delivery piston

Abstract

In the filling process of dispensing cartridges which have a self-sealing sliding delivery piston in the storage cylinder, it is essential to avoid the inclusion of air in the cylinder above the contents of the cartridge. For this purpose, the face of the piston toward the contents forms a continuous concavity having its vertex at the centre, where a vent hole passes through the piston to the outside. This hole seats a closing screw and has longitudinal grooves. These grooves are surrounded by an annular sealing surface which provides an axial seating for the screw head. When the screw is tightened, it securely closes all the longitudinal grooves. This design readily permits the automation of the filling, venting, and closing processes without impairment of the effectiveness of the piston's annular seal. A system of radial grooves in the face of the piston also ensures perfect venting of high-viscosity contents that form an irregular surface.

Dependencies are inferred from the claim text.