Automatic hollow punch search method for die-cutting machines, particularly for footwear production

A method of operating a die-cutting machine particularly for cutting material for footwear, said machine being of the type which has a fixed faceplate on which the material to be cut is placed and a mobile head mounted for motion in a horizontal plane above substantially the entire surface area of said faceplate, said machine further being of the type that uses separate hollow punches of different sizes and shapes positioned by the operator on the material to be cut on said faceplate, the method which comprises the steps of moving said mobile head in said horizontal plane starting from a rest position to seek a hollow punch therebelow, sensing a hollow punch on said material with means on said head as said head is moved in said horizontal plane, moving said head in a continuous and automatic cycle of operation starting from said rest position, moving said head in said horizontal plane until said sensitive element senses a hollow punch, stopping the motion of said head in said horizontal plane after said sensitive element has sensed that it has passed over said hollow punch and that said mobile head is therefore positioned over said sensed hollow punch, moving said head down to said hollow punch and then back up to said horizontal plane in a vertical cutting stroke, and then returning said head to said rest position, said machine comprising electrical circuit means and providing a pair of condensers in said electrical circuit means, causing said sensitive element to generate a signal starting from the time it first senses a hollow punch positioned on said material to be cut until the time it passes over said sensed hollow punch, providing a relatively large capacity in one of said condensers and providing a relatively small capacity in the other of said condensers, positioning both of said condensers in parallel circuits within said circuit means, and arranging said condensers within said circuit means such that either one of said condensers, upon its discharging, will operate other means to cause said head to cease its motion in said horizontal plane and to commence its motion in said vertical cutting stroke, and the step of selectively adjusting the capacity of said condenser of relatively smaller capacity, whereby said large capacity capacitor will not discharge until said head has completely passed over punches of normal to larger than normal size, and whereby said adjusted capacity of said capacitor of relatively smaller capacity will cause stoppage of motion in the horizontal plane and initiation of a vertical cutting stroke when said sensitive element senses a punch of relatively small size.