METERING DEVICE FOR A NOZZLE OF AN INJECTION MOLDING APPARATUS

摘要

An injection molding apparatus includes an injection piston (50) that is slidable within a nozzle (18) having a movable valve gate pin (28). The injection piston (50) is movable from a retracted position to an extended position in order to force melt towards a mold cavity (26). A valve (52) is located at a forward end of the piston (50) to selectively block communication between a recess (48), which is provided in an outer wall (51) of the piston (50) adjacent the valve (52), and a melt chamber (54) of the nozzle (18). Movement of the injection piston (50) from the retracted position to the extended position causes the valve (52) to close so that the predetermined volume of melt located below the valve (52) is forced into the mold cavity (26), when the valve gate pin (28) opens the mold gate (24).