1. Field of the Invention
This invention relates to a paper cutting machine.
Such a machine, and its operation in general, is described in U.S. Pat. No. 4,331,050, Gergek, May 25, 1982. The disclosure of that patent is hereby incorporated by reference.
The apparatus shown in that patent is equipped for sensing the position of an initial cut through a pile of paper on the machine and for moving the back gauge to repeat the cut in precisely the same position on another pile.
The present invention is directed to positioning the pile to be cut so that the cut will be made precisely along a predetermined cutting line.
This aim is to overcome inaccuracies in locating the cutting line encountered with previous apparatus.
2. Description of the Prior Art
In accordance with the prior art, one way of locating the cutting line has been to provide the machine with a light which shines a beam on to the surface of the top sheet of paper. A problem here is that the paper is some distance away from the light source so that the intensity of the light on the paper is too low for good observation and the beam too wide for accuracy. Moreover, the beam on the paper must be observed by the operator looking at it diagonally from his position in front of the machine and this further limits accuracy.
An alternative way of setting the paper is to lower the clamp and to observe where its edge is relative to indicia on the paper. A problem here is that, while the clamp is down against the paper, the pile cannot be moved to adjust the position with respect to the desired cutting line and the clamp has to be raised and lowered again. Further, the operator can only see the paper in front of the clamp which obscures the paper behind it. So, if the cutting guidemark is obscured by the clamp, the latter must be raised so that the paper can be moved in another attempt to locate the pile into cutting position. Besides not being precise, this process is time-consuming.