Abstract: A plastic injection mold apparatus which includes a multiple tip torpedo heater in a fluid plastic flow passageway. The torpedo heater includes an elongated body having an exposed outer cylindrical surface with tips at opposite ends thereof over which the fluid plastic material may be directed at an elevated temperature. The body is formed with an internal bore at the location of each tip for receiving a respective heating element. The torpedo heater is supported within the fluid plastic flow passageway by means of an outer cylindrical collar portion and three circumferentially spaced radial supporting elements which are formed of a softer metallic material than the body of the torpedo heater, and hence, are susceptible to repeated thermally induced expansion and contraction without undesired cracking or failure which can result in leakage of the flow stream and heater failure.

Abstract: A plastic injection mold apparatus which includes a multiple tip torpedo heater in the fluid plastic flow passageway. The torpedo heater includes a pair of substantially identical tip members and a mounting collar which together define an exposed outer cylindrical surface of substantially uniform diameter with a tip at each end thereof over which the fluid plastic material may be directed at an elevated temperature. The tip members each are formed with an internal bore for receiving a respective electrical heating element, the leads of which exit the heater through the central mounting collar. The torpedo heater is retained in mounted position by means of a removable bushing, which permits relatively easy removal and replacement of the heater. The mounting collar and bushing each are formed so that an insulating air space is defined about their outer peripheries for enhancing the energy efficient operation of the molding operation.

Abstract: A plastic injection molding system having a plurality of multiple tip torpedo heaters which each have a casing with a pair of opposed tips disposed in respective sprue passageways in a mold. An unsheathed electrical heating element is disposed in an internal bore of the casing at each tip and heat transmitting material is compacted in the bore in surrounding relation to the heating element for electrically insulating each heating element from the casing and filling all air voids between the casing and heating element to effect direct heat transfer to the casing. Electrical leads couple the plurality of heating elements to a power source to permit independent temperature control of the individual heating elements and the exposed surfaces of the respective casing tips over which fluid plastic material is directed.

Abstract: A plastic injection molding system having a plurality of multiple tip torpedo heaters which each have a casing with a pair of opposed tips disposed in respective sprue passageways in a mold. An unsheathed electrical heating element is disposed in an internal bore of the casing at each tip and heat transmitting material is compacted in the bore in surrounding relation to the heating element for electrically insulating each heating element from the casing and filling all air voids between the casing and heating element to effect direct heat transfer to the casing. Electrical leads couple the plurality of heating elements to a power source to permit independent temperature control of the individual heating elements and the exposed surfaces of the respective casing tips over which fluid plastic material is directed.

Abstract: A electric runner distributor heater for use in passageway of a mold into which a flow stream of fluid plastic material is introduced and which in turn communicates with a plurality of sprue orifices. The heater includes a metal casing having an exposed surface over which the fluid material is directed at an elevated temperature, a plurality of unsheathed electrical heating elements disposed in respective zones of the casing corresponding to the location of selected of the sprue orifices, heat transmitting material compacted in the bore of the casing and surrounding each heating element for electrically insulating the heating element from the casing and filling all air voids between the casing and heating element to effect direct heat transfer to the casing from the heating element, leads coupling the heating elements to a power source, and a control for independently controlling the temperature of the heating elements and thus the temperature of respective zones of the casing.