Machine for cross-cutting a web of material
BACKGROUND OF THE INVENTION 
     This invention relates generally to a machine for cross-cutting a web of material such as a running sheet of corrugated cardboard, and more specifically, to such a machine having a knife retained in a knife carrier that is arranged crosswise with respect to the sheet of material to be cut. The knife carrier is supported over its entire length on a stationary, bend-resistant support by supporting plates which are rotatably driven in synchronization with the knife carrier. 
     SUMMARY OF THE INVENTION 
     Machines for cross-cutting a running web of corrugated cardboard are known. Such machines include a cylindrical knife carrier which is supported by supporting plates in the form of eccentric disks that are rotatably driven in synchronization with the cutting roller. An example of such a machine is disclosed in German Patent No. 1 808 981.  In prior machines such as that disclosed in the referred-to German patent, the cutting roller is supported only on a short side thereof in the cutting position when the eccentric supporting disks are in supported contact with the cutting roller. In operation of such machine, immediately prior to and after engagement of the roller in its cutting postion, the eccentric supporting disks are moved out of contact with the cutting roller and the cutting roller then is in an unsupported condition. Thus, while cutting loads in prior art machines can be absorbed directly in the cutting position of the roller, possible undesirable vibrations of the cutting roller are not avoided in such machines. Furthermore, the weight of the cutting roller of such machines is not supported over the entire area of rotation of the roller. 
     The invention herein provides an improved machine in which the cutting roller thereof is supported over the entire length thereof. Further, the cutting roller herein moves with changes in the speed of the machine without undue delay. The invention accomplishes these objects by the provision of a knife carrier having an insignificant mass moment of inertia, and the provision of supporting plates having generally circular configuration with recesses on the circumference thereof to permit passage of the knife therethrough. 
     In the invention herein, known gearings for the generation of non-uniform rotative movement, as well as motors and brake coupling combinations which can produce periodic fluctuations in the number of rotations, are suitable as drive means for the cutting roller. These elements may be of much smaller size than that usually required because the mass moment of inertia of the knife carrier herein is substantially less than that of prior machines; the knife carrier therefore is quickly and easily adjustable with small-size control elements. 
     Other advantages of the invention will be apparent to those skilled in the art from the ensuing disclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective schematic view of the cross-cutting device of the invention, the same being shown partially exploded for better understanding thereof, and 
     FIG. 2 is a lateral sectional view taken through said device and a roller associated therewith. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The cross-cutting device includes a cutting roller 1 which has a relatively small diameter and is mounted in roller bearings 2 on both ends. The roller 1 carries a knife holder 3 with the knife blade 4. In order to obtain minimal cutting forces and the most uniform support for the roller, the knife holder 3 preferably has a slight pitch as shown. Drive for the cutting roller 1 is effected at one end 5 thereof to enable a periodically variable number of revolutions. The drive arrangement required for this purpose is of known type and is therefore not illustrated. 
     Supporting plates or rollers 7 are driven with the same number of revolutions as the cutting roller 1 by gears 6 mounted on shafts 8. The shafts 8 are disposed parallel to cutting roller 1. The supporting rollers 7 are arranged stationary on their respective shafts at a distance from one another and somewhat staggered relative to each other. The supporting rollers 7, which are arranged in pairs, support the cutting roller 1. Each roller 7 has a recess 15 on the circumference thereof to permit the passage of the knife blade 4 and the holder 3 therethrough. In cutting operation of the device, a web of material to be cut is passed between the rollers 7 and roller 1. The cutting forces which tend to bend the cutting roller 1 are absorbed by the supporting rollers 7 and transferred to the traverses 10 by way of bearings 9 and thereby into the main carrier 11 to prevent undesirable bending of the cutting roller. The shafts 8 are rotatably supported in bearings 9. 
     The device of the invention is adapted for operation with two such knife blades 4 which are operable against each other to produce a scissors cut. In the drawings, however, an embodiment to effect a punch cut is illustrated. In this case, the knife 4 cuts against a roller 12 which rotates at the same speed as the web (not shown). The roller 12 is covered with any material 13 suitable for protecting the roller during punch cut operation. 
     If it is desired to have the cutting roller 1 function as a tool, the supporting gears 6 can assume support of the device and bracing of the cutting roller. In this case it is possible to reduce the weight of the cutting roller even more with the result that the same has a still reduced mass moment of inertia. 
     The invention is of special advantage if the cutting roller 1 carries a knife 4 which is disposed generally slanted to the surface lines of the knife carrier 3 in the longitudinal direction thereof. In such case, the supporting rollers 3 with their recesses for the passage of the knife 4 are arranged staggered relative to one another. With such structure an even more uniform support of the knife carrier over the entire length of the carrier is achieved. A practical embodiment of the invention could be designed and dimensioned as next set forth: 
     1. Cylindrical knife carrier 1, of steel St 50; diameter: 130 mm length: 2800 mm. 
     2. Main carrier 11, welded structure of steel St 37; thickness: 10 mm length: 2550 mm. 
     3. Traverses 10 of the carrier 11, of steel St 37; thickness: 30 mm length: 350 mm width: 210 mm. 
     4. Supporting rollers 7, of steel St 50; diameter: 147 mm thickness: 20 mm. 
     The recess 15 extends over an angle of 95°. 
     5. Shafts 8, of steel St 50; diameter: 25 mm. 
     The mass moment of inertia thus obtained for the knife carrier is ca.1 kgm 2 , whereas the mass moment of inertia of known knife carriers amounts to approximately . . . 10 kgm 2 .