Multistroke punching method and apparatus therefor

An apparatus having a striker for punching a sheet-like workpiece, which comprises:

• (a) a height-different punch formed with a lower front edge, an upper rear edge, and an intermediate edge extending between [two edges] the lower front edge and the upper rear edge ;
• (b) a die having a recess thereunder and mated with said height-different punch;
• (c) means for moving the workpiece on a horizontal plane in predetermined directions;
• (d) means for controlling strokes of said height-different punch in such a way that in a first stroke, the lower front edge thereof cuts off the workpiece partially in cooperation with said [diee] die ;
• at succeeding strokes, the intermediate edge thereof cuts off the workpiece mincingly and curls refuse of the workpiece within the recess of the die;
• and at a last stroke, the upper rear edge thereof cuts curled refuse away from the workpiece to complete multistroke punching operation in cooperation with the die.

A punch tool for a press for punching a sheet-like workpiece by cutting a predetermined length of curl of a curled refuse away from the workpiece, comprising:

• a punch guide adapted to be mounted on a punch tool support means of the punch press, the punch guide being formed with a through hole having a longitudinal axis;
• a punch fitted in the through hole of the punch guide, said punch being movable in the direction of the longitudinal axis of the through hole, between a rest position in which a tip section of the punch is located within the punch guide, and a working position in which the tip section protrudes from the punch guide for performing a multiple stroke punching operation:
• a punch head provided on the punch, the punch being moved toward the working position by a strike of a ram of the punch press against the punch head:
• a spring provided between the punch head and the punch guide for urging the punch toward the rest position;
• said tip section of the punch having a shape of a rectangle in cross-section;
• the tip section being formed with a high edge section at one side of the rectangle in the transverse direction thereof, a low edge section formed at and extending along the opposite side of the rectangle, and a curved intermediate edge section extending between said high and tow edge sections;
• wherein, in the process of the punching operation, at a first stroke the low edge section is adapted to break through the workpiece to form a break therein, at repeated second strokes the intermediate edge section is adapted to widen the break, thereby forming a curled refuse and at a last stroke the high edge section is adapted to cut off the refuse from the rest of the workpiece to complete a punching
• operation.

An apparatus having a punch tool for punching a sheet-like workpiece by cutting a predetermined length of curl of a curled refuse away from the workpiece, which comprises:

• (a) a punch tool for a punch press, including:
• (i) a punch guide adapted to be mounted on a punch tool support means of the punch press, the punch guide being formed with a through hole having a longitudinal axis;
• (ii) a punch fitted in the through hole of the punch guide, said punch being movable in the direction of the longitudinal axis of the through hole, between a rest position in which a tip section of the punch is located within the punch guide, and a working position in which the tip section protrudes from the punch guide for performing a punching operation;
• (iii) a punch head provided on the punch, the punch being moved toward the working position by a strike of a ram of the punch press against the punch head;
• (iv) a spring provided between the punch head and the punch guide for urging the punch toward the rest position;
• (v) said tip section of the punch being formed with a high edge section, a low edge section, and a curved intermediate edge section extending between said high and low edge sections;
• wherein, in the process of the punching operation, the low edge section breaks the workpiece to form a break therein at a first step, the intermediate edge section widens the break at a second step, and the high edge section cuts off a refuse of the workpiece from the rest of the workpiece at a third step to complete a punching operation;
• (b) a die having a recess thereunder and mated with said punch tool;
• (c) means for moving the workpiece on a horizontal plane in predetermined directions;
• (d) means for controlling strokes of said punch tool in such a way that in a first stroke, the low edge section thereof cuts off the workpiece partially in cooperation with said die;
• at succeeding strokes, the intermediate edge section thereof cuts off the workpiece mincingly and curls refuse of the workpiece within the recess of the die;
• and at a last stroke, the high edge section curls refuse away from the workpiece to complete a multistroke punching operation in cooperation with the die.