| 摘要 |
PURPOSE:To increase the wall thickness of a thick walled cylindrical body to a required wall thickness in one stage using a general purpose press by acting a liquid pressure on the outside circumferential part of the cylindrical body to prevent bulging of the cylindrical body toward the outside in the radial direction in the stage of compressing said body and generating the liquid pressure cooperatively with the axial compressing effect of a punch. CONSTITUTION:Dies are opened while a punch 8 is kept lifted together with a punch attaching body 17 and a knock-out 12. A cap-shaped thin walled cylindrical body 1 is inserted and fitted into a male die 5. The punch 8 is then lowered and when the bottom surface thereof arrives at an oil surface 21, the air in a pressure chamber 9 is escaped through a passage 14 to the outside to replace the greater part of the chamber 9 inside with the oil. The punch 8 is further lowered to restrain the body 1 by sandwiching the same with the punch 8, the knock-out 12 and the die 5. The body 1 in this state is pressed to bulge outward against the high oil pressure in the chamber 9 toward the chamber 9 so that the wall thickness thereof is increased. The wall thickness of the body 1 is consequently increased by as much as the decrease in the axial length thereof. |
