Check Valve Lip Seal for an Injection Molding Machine

1 . A check valve for a molding machine, said check valve having a stem portion and a ring portion movable along said stem portion between a melt channel open position and a melt channel closed position, a groove formed in a forward face of said ring portion, said groove, in operation, receiving melt to force an outer circumferential portion of said ring in a radial direction to provide a seal between said ring portion and a wall in said machine.

2 . A check valve as defined in claim 1 wherein said groove is a V-shaped groove.

3 . A check valve as defined in claim 1 wherein said groove is a V-shaped groove with one side of said V extending in a direction parallel to said wall to form said outer circumferential portion.

4 . A check valve as defined in claim 1 wherein said groove is relatively shallow with respect to the length of said ring.

5 . A check valve for a molding machine, said check valve having a stem portion and a ring portion movable along said stem portion between a melt channel open position and a melt channel closed position, a groove formed in a forward face of said ring portion, said groove forming a relatively thin annular lip around said ring to create a thin flexible extension from said ring, said extension being flexed, in operation, by injection material to form a seal between said ring and a wall of an injection channel.

6 . A check valve as defined in claim 5 wherein said groove is a V-shaped groove.

7 . A check valve as defined in claim 5 wherein said groove is a V-shaped groove with one side of said V extending in a direction parallel to said wall to form said annular lip.

8 . A check valve as defined in claim 5 wherein said groove is relatively shallow with respect to the length of said ring.