Patent ID: 7213434
Filing Date: 2007-05-08
Classification: B21C,B21J,B21K

Abstract:
1. A method for manufacturing a universal joint yoke, comprising a forging step for forming a universal joint yoke preform from a workpiece placed in a die comprising an upper die 103 and a lower die 65 , which are to define a closed space, the forging step being performed such that while a back pressure not lower than 0.5 kg/mm 2 is applied to an end of a prospective universal joint yoke cup portion of the workpiece via a ring knock 67 , material of the workpiece is allowed to flow into a pin-boss-forming cavity of the lower die adapted to form a pin boss portion extending opposite the prospective cup portion until a filling rate not lower than 75% is reached, and that the ring knock is then moved in a direction opposite a regular forming direction of the upper or lower die, in which the ring knock is disposed, so as to initiate flow of the workpiece material toward the prospective cup portion.