US Patent 7771190 High pressure injection molding nozzle with low pressure manifold

A hot runner system includes a having a cavity. Melt is fed from a source of melt into the cavity, and a valve isolates melt in the cavity from melt in the source. A plunger within the cavity is driven forward to inject melt in the cavity into a mold cavity at high pressure without significantly increasing the pressure of melt in the source. The plunger optionally functions as both the plunger and the valve by opening and closing communication between the cavity and the manifold as it is rotated.