| 摘要 |
<p>Apparatus and controls therefor are provided for piercing sheet material. A punch is driven by a cylinder and piston positioned in tandem with a second cylinder and piston. The arrangement is such that a small pressure applied to the second piston results in a large force applied by the punch to the sheet material. Controls for the apparatus include means to sense a sudden drop in pressure in the second cylinder and means to then supply return air to the rod ends of the cylinders The controls are quickly responsive so that as the punch breaks through the sheet material, it is immediately reversed toward its original position. The noise and jarring ordinarily resulting when a punch breaks through sheet material being pierced are thereby substantially eliminated.</p> |
