| 摘要 |
PURPOSE:To obtain a rim having good balancing accurcy without variance in wall thickness by rolling a blank pipe in a diametral direction by roll forming to have a prescribed wall thickness. CONSTITUTION:An upper roll 3 under rotation is brought into press contact with a blank pipe and is rotated together with a lower roll 2 to roll the blank pipe in a diametral direction and to expand the pipe toward the diametral outside while making the wall thickness uniform, by which the 1st cylindrical body 11 provided with a cylidrical part 11a, large diameter part 11b, 11b and tapered parts 11c, 11c having prescribed sizes is obtd. The body 1 is then set in a press die 12 and is pressed with right and left punches 13, 13 to size a recess 52, large diameter parts 21b, 21b and large diameter parts 21c, 21c at the outside end, by which the 2nd cylindrical body 21 having a prescribed size is obtd. The lower roll is then set in the body 21 and while the upper roll is rotated from the outside, said roll is brought into contact with the cylindrical body from above. A rim consisting of a bead receiving part and the recess 52 is thus obtd. |
