Cartridge plunger for injecting plastic - with radial and central slots for air venting

摘要

The plunger has a convex face to the cartridge and an outer lip to seal against the cartridge wall, against which it is guided by a hollow outer extension. The back of the plunger has a central projection with inner venting space and a slotted plug fits centrally into this space. When the cartridge is filled, the plunger is inserted and pushed in to meet the contents by a centrally bored tool applied to the back, air escaping through the central slots and also through narrow radial grooves in the face. A punch is then applied to the central plug and the cartridge is ready for use.