Abstract: A method of manufacturing a bobbin in which a plastic flange is first insert molded to one end of a winding shaft of nonferrous metal alloy. A bushing of synthetic resin is the forced into a bore in the winding shaft at the other end thereof, and a core having a head is inserted into a bore in the bushing to close an open end of the bore in the bushing with the head of the core. The end of the winding shaft, an outer end of the bushing, and the head of the core are placed in a mold, and a synthetic resin material is injected through a sprue, a runner, and a gate in the mold into a cavity therein to mold a second flange on the end of the winding shaft therearound to obtain a bobbin having plastic flanges at both ends.

Abstract: The present invention relates to a method for manufacturing component thermoplastic sections and for joining them into bobbins for spinning and twisting machines. A frictional surface is formed by injection molding at the outer end surface of a male section and the inner end surface of a female section of a bobbin. By joining the sections and subjecting them to a high-speed rotation relative to each other the frictional surfaces melt and the sections are fused into an integral break resistant bobbin. The specific shapes of the male and female contacting surfaces and the manner of fusing them together are described as being critical.