US Patent 7731489 Valve for co-injection molding apparatus

A coinjection molding apparatus includes at least one manifold having a first manifold melt channel and a second manifold melt channel. A hot runner nozzle is located between the manifold and a mold gate. The nozzle has melt channels communicating with the first manifold melt channel and the second manifold melt channel. A valve has a movable valve member for increasing and decreasing flow of melt in one of the melt channels of the nozzle. The valve member receives a pressure force from the melt. An actuator provides a control force to the valve member. The valve member moves in response to a difference between the pressure force and the control force.