Wire feed apparatus

Abstract

A wire feed apparatus for a wire cut electric discharge machining apparatus, capable of moving a wire conveyor belt from an automatic wire extension position to a non-wire-transfer shunt position at the time of electric discharge machining, thereby preventing wear of the belts and reducing variation in the wire feed speed. The apparatus includes first and second conveyor belts selectively operated in accordance with predetermined conditions for wire feeding. At the time of automatic wire extension, an air cylinder of a wire feed mechanism is driven to move the second conveyor belt from a non-wire-transfer shunt position to the automatic wire extension position using a parallel link mechanism. The second conveyor belt is pressed against the first conveyor belt at the automatic wire extension position. When both these belts rotate as a motor is driven, a wire electrode held between the belts is transported from an upstream side of a wire transfer path to a downstream side thereof, whereupon the automatic wire extension is finished. When the air cylinder is de-energized, the second conveyor belt is restored to the non-wire-transfer shunt position and separated from the first conveyor belt by means of the urging force of a spring. Accordingly, the wire electrode and the two belts are out of contact with one another during the electric discharge machining operation, thus preventing wear of the belts and variation in wire feed speed.