Patent ID: 6865808

Claim:
A method of forming a pulley comprising the steps of: (A) fixing an edge of an opening of a plate working piece by using a first upper mandrel ring disposed at a lower end of a first supporting pin of a first forming device after disposing the plate working piece having the opening at a center portion thereof on a supporting block and a supporting ring, the supporting block being disposed around an upper end of a first spindle and rotatable along with the first spindle of the first forming device, the supporting ring being disposed around the supporting block; (B) forming an inner hub by inwardly pressing an upper surface of the plate working piece which is rotated along with the first spindle by a first pressing roller to reduce the thickness of the plate working piece while drawing the plate working piece around the first upper mandrel ring; (C) fixing the plate working piece to a second spindle so the plate working piece rotates with the second spindle by disposing an outer region of the inner hub between a second upper mandrel ring and a second lower mandrel ring disposed at an upper end of a second spindle of a second forming device; (D) forming a convex bead portion by pressing an edge of the plate working piece that rotates along with the second spindle by using a third pressing roller; and (E) forming an outer hub forming portion by pressing the convex bead portion in a direction toward the inner hub by using a fourth pressing roller and by drawing an outer hub, so as to make a first semi-manufactured pulley.