Apparatus for hydraulically forming sheet metal pulleys

Abstract

Apparatus for forming a sheet metal pulley from a cup-shaped blank in a single hydraulic forming operation. A pair of die holding members supports a plurality of groove-forming inner dies and is movably mounted on a base for horizontal reciprocal movement between open and closed die positions for capturing a pulley-forming blank therebetween. Tapered pins extend vertically through aligned openings formed in overlapping shelf members of the die holding members to wedgingly clamp the dies toward each other and to lock them in a horizontally closed position. A ram plate is mounted on a plurality of vertical posts for reciprocal vertical movement with respect to the captured blank. The ram plate has a top die which exerts axial pressure on the hub portion of the blank during the hydraulic bulging of the blank side wall by a confined fluid within the blank in cooperation with the groove-forming inner dies. A plurality of pistons mounted on the vertical ram plate cammingly engage mating surfaces provided on the posts and adjacent cam shafts to mechanically lock the ram plate die in a vertically closed position. A burst of high pressure is applied to the trapped, partially formed pulley to final form the pulley by setting the metal of the pulley against the inner dies by exceeding the elastic limit of the metal, eliminating springback after the pulley is removed from the dies. Certain of the groove-forming inner dies are movable vertically independently of the top ram plate and hub die by hydraulic pistons to permit variation in the groove-forming sequence during the pulley forming procedure.