Patent ID: 7588713

Claim:
A method of manufacturing a resin boot for a constant velocity universal joint, comprising: preparing a bellows that has a conical shape with a hollow space and has a first opening at a large diameter side end portion and a second opening at a small diameter side end portion; forming an injection space between an inner periphery of the large diameter side end portion and a core mold, the core mold having an outer periphery opposed to the inner periphery, the outer periphery having a plurality of first concave portions circumferentially disposed at regular intervals, the injection space having a plurality of narrow spaces between the adjacent first concave portions and a plurality of wide spaces continuously formed with the plurality of narrow spaces, corresponding to each of the plurality of first concave portions; injecting a molten material from a plurality of injection gates to the injection space, each of the plurality of injection gates corresponding to each of the plurality of narrow spaces; allowing the injected molten material to flow from each of the plurality of injection gates through each of the plurality of narrow spaces to two of the plurality of wide spaces continuously adjacent in a circumferential direction to each of the plurality of narrow spaces, and to interflow in each of the plurality of wide spaces; and hardening the molten material to be integrally formed with the inner periphery of the large diameter side end portion, wherein a position of each of the plurality of injection gates is set to 0≦t≦2a/3 in which a distance between the inner periphery of the large diameter side end portion of the bellows and the injection gate is set to t, and a diametrical distance of the large diameter side end portion of the injection space is set to a.