Check valve assembly for injection molding apparatus

In a improved check valve assembly for an injection molding apparatus having a rotatable and axially translatable feedscrew within a barrel bore and adapted for moving a polymeric material through the valve assembly towards an exit chamber of the apparatus, the check valve assembly comprising:

• (A) a valve body member attached to the forward end of the feedscrew and moveable with the feedscrew, said body member having at least one valve seat surface thereon;
• (B) an axially slidable member mounted on the body member for limited axial movement thereon, said slidable member having;
• (1) at least one valve seat surface which frictionally engages a corresponding valve seat surface on the body member, and
• (2) a circumferential surface at the outside diameter of said axially slidable member which frictionally engages the inner surface of the barrel bore;
• (C) the improvement comprising a substantially abrasion-resistant coating bonded to at least one of the frictionally engaging surfaces of the check valve assembly, said bonded coating effectively reducing frictional wear between coacting frictionally engaging surfaces and between the surfaces and the plasticized material as it is moved through the check valve assembly.

In an injection molding apparatus having a rotatable and axially translatable feedscrew within a barrel bore and adapted for moving a polymeric material through the barrel from an input end to an exit end and having a check valve assembly mounted forwardly on the feedscrew toward the exit end to govern the amount of a plasticized polymeric material being ejected from the apparatus, an improved check valve assembly comprising in combination:

• (A) a valve body having a conically-shaped forward end and a rearward shank end, the forward end having axially oriented flute passages through the valve seat surface and said shank end having a valve passage portion and a threaded end portion for threaded engagement within an axial bore in the end of the feedscrew;
• (B) a valve seat ring mounted on the shank end of the valve body at the juncture of the valve passage portion and the threaded portion and having a forwardly facing valve seat surface;
• and
• (C) an annular valve check ring mounted coaxially about the valve passage portion of the valve body shank end, said check ring having forward and rearward frustoconical valve seat surfaces for alternate seating engagement with the rearward-facing valve seat surface of the conically shaped forward end of the valve body when the valve is in an opened position and with the forward-facing valve seat surface of the valve seat ring when the valve is in a closed position in response to a back-pressure generated by the plasticized material passing through and forwardly of the check valve assembly;
• (D) said valve seat surfaces of the valve body, the valve seat ring, and the valve check ring being treated with an abrasion-resistant bonded coating to effectively reduce friction wear between the relatively engaging valve seat surfaces and between the plasticized material and the valve seat surfaces as the material passes through the check valve assembly.