| 摘要 |
PURPOSE:To obtain the powdery formed body free from cracks, cut-off, etc., by providing an upper punch having a lower end surface partially insertable along a pressing direction, press-forming powder poured in a die with upper and lower punches, and then smoothly withdrawing the powdery press-formed body from the die and the upper punch. CONSTITUTION:Powder 2 in a die 3 is pressed by the dropping of upper punches and the rising of a lower punch 7. When the pressing power is at the maximum value, the pressure of a coil spring 13 inserted onto an inside upper punch 9 goes under the main pressure of an outside upper punch 8 and the lower punch 7 to bring the upper end surface of the punch 9 into contact with a stopper 11. Consequently, difference in level is formed at the lower end surfaces of the upper punches to reform the pressed powder into a formed body 6 having a projection 14 at is upper part. The withdrawal of said formed body 6 is performed by pushing out the punch 9 downwards with the pressure of the spring 13, since the pressure is reduced by raising the upper punches after the completion of the pressing. At this time, the projection 14 of the formed body 6 is smoothly withdrawn from the cylindrical cavity of the punch 8 without the formation of disorder such as cracks or cut-out in the formed body 6. |
