Positive control non-return valve for an injection molding machine

The invention relates to the injection molding process, blow molding process or the like and in particular to a positive control non-return valve that controls the flow of molten plastic fluids. More specifically, the invention relates to an improved non-return valve assembly that allows the proper flow through said valve in one direction and positively stops the reverse flow of material therethrough. An improved positive control non-return valve assembly which is mounted on the front end of a helical plasticating screw of an injection molding machine. The valve assembly comprises a thread retainer with means for attachment to the plasticating screw. The valve assembly also comprises a distribution chamber that has an annular shaped flow gap and a cylindrical passageway that leads to a plurality of discharge ports. The non-return valve assembly forms a seal, builds pressure, and displaces molten plastic fluid from the distribution chamber through a discharge chamber passageway, and into a mold.