The present invention relates to a method of and an apparatus for transferring a file of sheets of paper, plastic or like material from the top of a sheet stack to a treatment station, for instance to a vibratory table.
When cutting paper with the aid of a single-knife guillotine, it is first necessary to separate the sheets with air and then lift the sheets onto the vibratory table in order to shake the sheets into their correct positions before the file can be cut. This is effected fully manually. The sheets may measure 1400 x 1000 m. This means that the file can weigh up to 25-30 kg, depending on the size of the sheets and on the thickness of the file. Three to four files form a cutting file, the weight of which may be of the order of 70-75 kg. In order to cut the sheets correctly and to loosen any sheets that may have fused together, it is necessary to blow air between the sheets before placing the sheets on the vibratory table. A method of and an apparatus for transferring a file of sheets uppermost in a sheet stack to a treatment station, comprising the steps of gripping one edge of the file and swinging the edge upwards-rearwards and rolling the file over a part of the upper surface of the stack and transferring said file to the treatment station have earlier been proposed in EP 0 098 385 A for instance. However, this method is very complicated and consists of no fewer that eleven steps which means that the corresponding apparatus will be very expensive and functional sensitive. It also shows that the problem in question is great.
The object of the present invention is to solve the aforesaid problem and to provide a method and apparatus for transferring a sheet file from a sheet stack to a treatment station, including loosening of fused sheets and separation thereof by air. This object is achieved with an inventive method and inventive apparatus having the characteristic features set forth in claims 1 and 7.
Further embodiments of the invention are defined in dependent claims 2 to 6 and 8.
The invention will now be described in more detail with reference to the accompanying drawing, in which
Shown in the drawing is a stack of sheets 1 from which a file of sheets is to be loosened and transferred to a treatment station, for instance to a vibratory table. To this end, there is provided at least one clamping device 3 which is mounted on a substantially vertical operating arm 4 for pivotal movement through 180° about a horizontal axle 5. The operating arm 4 can be moved reciprocatingly in the horizontal plane with the aid of a servo-device. The clamping device 3 is provided with a nozzle for blowing air between the sheets.
As will be seen from Fig. 1, one edge 6 of the file 2 is gripped and swung upwardly-rearwardly through 180° and drawn in the direction of the arrow 7 while rolling the file 2 over a part of the upper surface of the stack 1. The operating arm 4 is then returned and the file 2 rolled in the opposite direction, back over the upper surface of the stack. As the file of papers is returned, air is blown in between the sheets from the sides thereof so as to air-separate all sheets in the file. The opposing edge 10 of the file may optionally be clamped firmly during this return movement. The folding device intended to hold the sheets firmly at the opposing edge 10 is symbolized by the weight 8 in Fig. 2. The operating arm 4 is now moved in the direction of the arrow 9.
As before mentioned, the gripping device is operated with servo-assistance, wherein the operator grips a control lever on the operating arm 4 and moves it in the desired direction. The apparatus may be suspended either from a swivel crane, an overhead crane, or may run in tracks.
The described movement generates shearing between the sheets in the file 2. As the upper outwardly sheared part of the file is held firmly and the rolling movement is partly repeated, the sheets will separate and allow air to flow therebetween.
Upon completion of the return rolling movement according to arrow 9, the file can either be drawn directly to the treatment station or can be turned by again rolling over the file and then drawn over to the treatment station. Air is suitably blown in beneath the file 2, in order to reduce friction.