| 摘要 |
A sprue bushing which has improved heat transfer characteristics and a method of making the same are described. A cylindrical bushing body having a first, preselected uniform diameter has a cavity formed therein which axially extends within the bushing body for a predetermined length. A bushing inner core which has an outer layer or sleeve or a high heat conductive material is formed in the cavity extending between the two ends of the bushing body. A heating element in the form of a ceramic insulator sleeve is inserted into the bushing body cavity and a particulate refractory material is deposited into the cavity to fill the remainder of the cavity. When filled, the bushing body is swaged down to a second preselected uniform diameter to compact the powdered refractory together with the preformed sleeve to form a solid heating element. A runner passage is then drilled through the inner core.
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