Patent Number: 6,168,399

Title: Shot piston for molten plastic material

Abstract: A shot piston device for molten plastic material with a force-operated piston guided in a cylinder provided with an inlet and an outlet, wherein valve arrangements ensure that the cylinder is filled during the return stroke of the piston and the cylinder content is discharged during the work stroke of the piston. The piston is fixedly connected by a drive bolt to a differential piston arranged upstream or in front of the piston. At least in its rearward extreme position, the differential piston covers and closes the outlet arranged in the corresponding differential cylinder. The circumference of the piston has at least one groove located underneath the inlet and extending from the end face of the piston facing the differential piston. The length of the groove is shorter than the length of the piston. A closing ring is arranged so as to be axially slidable on a cylindrical portion of the drive bolt arranged in front of the end face of the piston facing the differential piston. The closing ring is capable of closing the groove relative to the pressure space.

Inventors: Gneuss; Detlef (Bad Oeynhausen, DE), Muller; Hans-Otto (Bad Oeynhausen, DE)

Assignee: Gneuss Kunststofftechnik GmbH

International Classification: B29C 45/58 (20060101); F04B 039/10 ()

Expiration Date: 01/02/2018