Stamping apparatus and stamping method

Abstract

A stamping apparatus includes a die, a punch, a back-pressure device, a lift-up mechanism, and a delay device. A workpiece is mounted on the die. The punch is arranged to approach and recede from the die and configured to punch out a product from the workpiece. The back-pressure device includes a pushing member disposed in the die and urges the pushing member toward the punch to apply back pressure to the workpiece. The lift-up mechanism is configured to lift the workpiece above the die when the punch recedes from the die. The delay device is configured to delay lifting movement of the pushing member in relation to receding movement of the punch when the punch recedes from the die.

What is claimed is: 
     
         1 . A stamping apparatus, comprising:
 a die on which a workpiece is mounted;   a punch arranged to approach and recede from the die and configured to punch out a product from the workpiece;   a back-pressure device including a pushing member disposed in the die, the back-pressure device urging the pushing member toward the punch to apply back pressure to the workpiece;   a lift-up mechanism configured to lift the workpiece above the die when the punch recedes from the die; and   a delay device configured to delay lifting movement of the pushing member in relation to receding movement of the punch when the punch recedes from the die.   
     
     
         2 . The stamping apparatus according to  claim 1 , wherein
 the back-pressure device includes an urging portion that upwardly urges the pushing member and an intermediate portion disposed between the pushing member and the urging portion, and   during a set period from when the receding movement of the punch starts, the delay device restricts upward movement of the intermediate portion to delay the lifting movement of the pushing member in relation to the receding movement of the punch.   
     
     
         3 . The stamping apparatus according to  claim 2 , wherein the urging portion includes a gas cylinder. 
     
     
         4 . The stamping apparatus according to  claim 2 , wherein the delay device includes
 a lower pin movable in an approaching-receding direction of the punch, the lower pin having a lower end opposed to an upper surface of the intermediate portion,   an upper pin that moves together with the punch in the approaching-receding direction of the punch, the upper pin having a lower end configured to contact and separate from an upper end of the lower pin,   a switch member including an opposing surface opposed to an upper end of the upper pin and a recess disposed in a portion of the opposing surface to accommodate the upper end of the upper pin, wherein while the switch member moves together with the punch in the approaching-receding direction of the punch, the switch member does not lift or lower when the punch is located between a bottom dead center and a set position that is located above the bottom dead center, and   a drive mechanism configured to move the switch member between an accommodated position in which the upper end of the upper pin is accommodated in the recess and an opposing position in which the upper end of the upper pin is opposed to the opposing surface,   
       while the punch is punching out the product, the switch member is set to the accommodated position, and 
       while the punch is receding from the bottom dead center to the set position, the switch member is set to the opposing position, so that the upper pin and the lower pin are in contact with each other and held between the opposing surface and the upper surface of the intermediate portion. 
     
     
         5 . The stamping apparatus according to  claim 4 , wherein
 the switch member is rotational about an axis that extends in the approaching-receding direction of the punch, and   the drive mechanism rotates the switch member about the axis between the accommodated position and the opposing position.   
     
     
         6 . The stamping apparatus according to  claim 1 , wherein
 a lifter is disposed in the pushing member and urged toward the punch to retractably extend from the pushing member, and   the lifter is configured to lift the product above an upper surface of the pushing member.   
     
     
         7 . The stamping apparatus according to  claim 6 , wherein a holding pin is disposed in the punch to retractably extend from the punch so that when the product is lifted by the lifter, the holding pin presses an upper surface of the product to hold a position of the product. 
     
     
         8 . A stamping method, comprising:
 when punching out a product from a workpiece by causing a punch to approach and recede from a die on which the workpiece is mounted, applying back pressure to the workpiece from a side opposite to the punch using a pushing member; and   when the punch recedes from the die, lifting the workpiece above the die and delaying lifting movement of the pushing member in relation to receding movement of the punch.