Mechanisms for driving punch pins in punching apparatus

Abstract

In a punching apparatus, a die set supports, in mutual opposition, an upper die part on which a plurality of punch pins upwardly urged by a plurality of springs are axially slidably disposed at predetermined intervals, and a lower die part formed with a plurality of holes opposing the punch pins. A device for driving the punch pins includes a plurality of drive shafts each having at least three shaft portions disposed adjacent to each other, part of the shaft portions being formed of a magnetic material and the remaining part thereof being formed of a non-magnetic material. At least two electromagnetic coils are fitted around the shaft portions of each drive shaft, and a clutch mechanism disposed on one end of each drive shaft separably couples the drive shaft with the punch pin. The driving device greatly reduces the amount of heat generated by the electromagnetic coils to allow the adoption of an air cooling system, and increases punching force to assure positive working. The clutch mechanism includes male and female clutches, both flanged, and a bush sleeve which, upon abutting on an end of the male clutch, forms predetermined clearances between flanges of the male and female clutches. The clutch mechanism securely couples a punch pin with its drive shaft, while compensating for deviation in their axes so as to prevent bending and breakage of punch pins.