Positive control non-return valve for an injection molding machine

A positive control non-return valve assembly for an injection molding machine, said molding machine comprised of an elongated helical plasticating screw that rotates about an axis and reciprocates along said axis within a heated barrel to discharge molten plastic material through said non-return valve assembly at a discharge end of said screw, said non-return valve assembly comprised of at least two independent components, said non-return valved assembly comprising:

• a) a thread retainer that has a means for attachment to, or is integral with, said screw, the threat retainer having a first portion that is generally cylindrical a second portion that is generally conical and a third portion that is generally cylindrical and extending telescopically forward along said axis with a means for attachment to a spherical retainer;
• b) a free rotating unattached shutoff mechanism that is sandwiched between said thread retainer and said spherical retainer, having an outer periphery that is first cylindrical, a second portion that is generally conical leading to a frustum, said frustum having generally a spherical concave facial with a cylindrical thru-hole;
• and
• c) said spherical retainer with a means for attachment to said thread retainer that when attached governs the axial forward movement of said free rotating unattached shutoff mechanism, that employs a spherical seat retaining area and a means for installation and removal.