Band heater clamp arrangement for an injection molding machine

摘要

The present invention relates to a bi-metallic clamping system for holding a heater firmly on the external surface of a hot runner nozzle body. The band heater-clamp arrangement of the present invention is formed by a cylindrical sheath which houses the heater coil. The sheath has an inner sleeve formed from a material having a relatively high thermal expansion and an outer sleeve formed from a material having a relatively low thermal expansion. The heater coil is positioned between the two sleeves. The desired clamping effect is produced by providing at least one axial slot in the inner sleeve. It has been found that during heating, the outer sleeve expands less than the inner sleeve due to the differences in the thermal expansion coefficients of the materials used to form the sleeves. This produces radial forces in the inner sleeve that are redirected into circumferential forces by the axial slot. These circumferential forces in turn cause the slot to close and thereby achieve the desired clamping effect. The band heater-clamp arrangement of the present invention has utility in injection molding machines having hot runner systems for providing liquified plastic material from a source to an injection gate.