PISTON INJECTION UNIT FOR AN INJECTION MOLDING MACHINE

The present invention relates to a piston injection unit for an injection molding machine with a cylinder (11), a piston (9) guided movably therein and a nozzle unit (4), which is disposed at one end of the cylinder. Flowable material can be pressed through the nozzle unit (4) by means of the piston. A supply opening (21) is provided in the cylinder wall in a region, which, in every position of the piston (9) during the operation, is on the side of the end of the piston, assigned to the nozzle unit, facing away from the nozzle unit, so that the flowable material can be introduced into the cylinder (11) transversely to the longitudinal axis of the piston or the cylinder. The piston (9) has at least one first sealing area (23) at the end of the piston assigned to the nozzle unit. The sealing area has an external surface of the piston and an internal surface of the cylinder, which seal by mutual flat contact. In the area between the supply opening and the first sealing region, a flow channel (15, 17, 18, 24) for the flowable material is provided and, in the piston end facing the nozzle unit, discharges at a distance from the outer surface of the piston and/or a scraper part (8) for a flat contact with the outer wall of the piston is provided at the cylinder (11). A scraper surface, extending transversely to the longitudinal axis of the piston or the cylinder and surrounding the piston (9), is formed in a plane, which is provided at an angle to the longitudinal axis of the piston.