Sprue bushing assembly and method of making same

Abstract From the Canadian patent

A sprue bushing which eliminates melt leakage and a method of making the same are described. A cylindrical bushing body having a first, preselected uniform diameter has an annular cavity formed therein which axially extends within the bushing body for a predetermined length and which separates the bushing inner core from the bushing body. A heating element in the form of a ceramic insulator sleeve is inserted into the annular cavity and a particulate refractory material is deposited into the annular cavity to fill the remainder of the annular cavity. When filled, the bushing body is swaged down to a second preselected uniform diameter to compact the powdered refractory together with the …