Abstract: An injection molding apparatus which includes a check valve assembly mounted at the forward end of a feed-screw, the valve assembly having forward and rearward valve seat surfaces which co-act in a first position to allow a plasticized polymeric material to enter and flow through the valve into an injection chamber and which co-act in a second position to stop any additional material from entering the valve assembly. The second valve position is effected by a feed-screw injection stroke which generates a back pressure to close the valve, the back pressure moving a check ring of the valve assembly into a position to block entry into the valve. Part of the valve seat surfaces are covered with a plurality of ceramic disks and other valve seat surfaces are covered with a metal alloy which effectively increases the abrasion resistance of the valve seat surfaces and thus also increases the wear service life of the check valve assembly.

Abstract: An injection molding apparatus which includes a check valve assembly mounted at the forward end of a feed-screw, the valve assembly having forward and rearward valve seat surfaces which co-act in a first position to allow a plasticized polymeric material to enter and flow through the valve into an injection chamber and which co-act in a second position to stop any additional material from entering the valve assembly. The second valve position is effected by a feed-screw injection stroke which generates a back pressure to close the valve, the back pressure moving a check ring of the valve assembly into a position to block entry into the valve. Part of the valve seat surfaces are covered with a plurality of ceramic disks and other valve seat surfaces are covered with a metal alloy which effectively increases the abrasion resistance of the valve seat surfaces and thus also increases the wear service life of the check valve assembly.

Abstract: An injection molding apparatus which includes a check valve assembly mounted at the forward end of a feedscrew, the valve assembly having forward and rearward valve seat surfaces which co-act in a first position to allow a plasticized polymeric material to enter and flow through the valve into an injection chamber and which co-act in a second position to stop any additional material from entering the valve assembly. The second valve position is effected by a feedscrew injection stroke which generates a back pressure to close the valve, the back pressure moving a check ring of the valve assembly into a position to block entry into the valve. The valve seat surfaces are covered with a preformed layer of ceramic material and/or metal alloy which effectively increases the abrasion resistance of the valve seat surfaces and thus also increases the wear service life of the check valve assembly. Other wear surfaces of the valve assembly may also be coated for abrasion resistance.

Abstract: This invention provides an improved injection molding apparatus which includes a check valve assembly mounted at the forward end of a feedscrew, the valve assembly being characterized by forward and rearward valve seat surfaces which co-act in a first position to allow a plasticized polymeric material to enter and flow through the valve into an injection chamber and which co-act in a second position to stop any additional material from entering the valve assembly. The second valve position is effected by a feedscrew injection stroke which generates a backpressure to close the valve, the backpressure moving a check ring of the valve assembly into a position to block entry into the valve. The valve seat surfaces are coated with a bonded metal, metal alloy, or ceramic material which effectively increases the abrasion resistance of the valve seat surfaces and thus also increases the wear service life of the check valve assembly. Other wear surfaces of the valve assembly may also be coated for abrasion resistance.