| 摘要 |
This invention relates to an improved method of making a sprue bushing for injection molding and the improved sprue bushing made thereby. The runner passage extends through a corrosion resistant inner core portion with an outer surface around which a helical electrical heating element is located. A stainless steel outer sleeve extends between an enlarged front portion which provides the opening to the gate and an enlarged back collar portion which provides for connection to the heating element leads. The space around the heating element is filled by a highly conductive material such as a beryllium copper alloy in a vacuum furnace which causes the beryllium copper to fuse with the adjacent materials. This improves the transfer of heat from the heating element to the melt and the outer sleeve substantially reduces the costly machining required to produce the finished product as well as provides additional strength. In one embodiment, wells extending into the front portion are filled with the highly conductive material which increases heat transferred to the gate area. A thermocouple may be located in one of the wells to monitor the transfer of heat to this area. |
