Reduction in deflection of valve pin in injection moulding apparatus

摘要

An injection moulding apparatus includes a manifold having a channel receiving an injection of molten polymer and delivering the molten polymer to a nozzle assembly. The nozzle includes a nozzle gate delivering the molten polymer to a mould. A valve gate drop assembly has a valve pin extending from a valve pin cylinder which passes through an eccentric bushing in the manifold. The valve pin extends into the nozzle assembly and terminates at the nozzle gate. The valve pin is aligned with the nozzle gate and is adapted for control of flow of molten polymer through the nozzle gate by movement into and away from the nozzle gate. The movement of the valve pin is controlled by the valve pin cylinder. During operation, the manifold can undergo a change in position relative to the positions of the valve pin cylinder and nozzle assembly as a result of thermal expansion and contraction of the manifold. The eccentric bushing in the manifold rotates on change of position of the manifold generally to maintain alignment of the valve pin with the nozzle gate and reduce deflection of the valve pin caused by change of position of the manifold.