The clamp of conventional guillotines are constructed in one piece to move up and down as a whole, close to the knife, so that the sole surface or the clamping surface presses, in a straight line, the cutting material such as paper or the likes on the table surface of the guillotine.
If cutting material which is so uniform in thickness as a simple pile of paper, this type of clamp does not cause much trouble in cutting, as the cutting material is clamped with uniform pressure. However, if the cutting material is, for example, a pile of printed paper or bound books which are glued on the back or the like, in the former case where there is so uneven thickness as the printed parts with ink are thicker than other nonprinted parts, and, in the latter case where the glued back parts are thicker than other parts and also there is much variation in compressibility or compressive modulus, although the cutting material may be pressed in a straight line, the other parts mentioned above cannot uniformly be pressed. Consequently, in case of cutting, the cut surface is warped, or in the cut part which is not sufficiently clamped, there is slippage of paper at the cut, or worst of all, the knife blade of the guillotine is broken.
In order to prevent such an accident, a pad is usually attached to the clamping surface of the clamp to compensate for uneven thickness of cutting material. However, it is quite difficult to make a pad which can completely prevent the above-mentioned accident from ocurring, for even the same cutting materials must be more or less different in shape. Besides, in case of providing a pad, the position of cutting material to be placed should be exactly fixed, therefore, reduction of operating efficiency is inevitable. And, on the contrary, it may require much trouble to locate the pad properly on the cutting material for every cut, or, worse, it may be dangerous and is not possibly practicable.
USPTO Backgrounds
USPTO Backgrounds