Spring biased check valve for an injection molding machine

Abstract

An improved check valve assembly which is mounted on the front end of a feedscrew of an injection molding machine has a check ring which is slidably mounted on the shank of a retainer within the heated barrel of the molding machine. An annular-shaped flow gap is formed between the inner periphery of the check ring and retainer shank for feeding sleeves of heated material into a discharge chamber at the forward end of the barrel. The check ring is movable between a forward material feed position where it is engaged with a front valve seat and a rearward material blocking position where it is engaged with a rear valve seat. A compression coil spring is telescopically mounted on the retainer shank and is located within the annular-shaped flow gap and biases the check ring toward the material block position to provide a positive valve shut-off irrespective of the viscosity of the heated material. In an alternate embodiment, a plurality of circumferentially spaced coil springs extend between opposed annular end surfaces of the check ring and the front valve seat for biasing the check ring toward the material block position.

Dependencies are inferred from the claim text.