Patent Publication Number: US-2010107911-A1

Title: Printing Unit of a Printing Press

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to a printing unit having at least one printing couple, each printing couple including a form cylinder, a transfer cylinder, and an inking couple, the transfer cylinder having a circumference which is a whole-number multiple of the circumference of the form cylinder; an impression cylinder cooperating with the form cylinder to form a nip through which a substrate to be printed can be fed; and a drive connection between the transfer cylinder and the form cylinder. 
     2. Description of the Related Art 
     Printing units of web-fed printing presses known from practice have several printing couples, where each printing couple comprises a transfer cylinder, a form cylinder, an inking couple, and possibly a dampening unit. Form cylinders are also called plate cylinders, and transfer cylinders are also called blanket cylinders. An impression cylinder works together with the transfer cylinder or blanket cylinder of a printing couple to form a nip for the substrate to be printed, where the impression cylinder can be a satellite cylinder or a transfer cylinder or blanket cylinder of an adjacent printing couple. A satellite cylinder usually cooperates with several transfer cylinders of different printing couples. In the case of sheet-fed printing presses, the impression cylinder which cooperates with the transfer cylinder of a printing couple is called a printing cylinder. 
       FIG. 1  shows a schematic diagram of a printing unit  10  of a web-fed printing press known from the prior art with two printing couples  11 ,  12  for printing both sides of a substrate web  13 , where each of the two printing couples  11 ,  12  comprises a transfer cylinder  14 , a form cylinder  15 , an inking couple  16 , and a dampening unit  17 . In the case of the printing unit  10  of  FIG. 1 , therefore, the transfer cylinder  14  of the printing couple  11  forms the impression cylinder for the transfer cylinder  14  of the printing couple  12 , and the transfer cylinder  14  of the printing couple  12  forms the impression cylinder for the transfer cylinder  14  of the printing couple  11 . 
     In the printing unit  10  of  FIG. 1 , a drive motor  18  is assigned to the transfer cylinder  14  of the printing couple  12 . This motor acts on the transfer cylinder  14  of the printing couple  12 . The drive motor  18  of the printing unit  10  of  FIG. 1  serves to drive the transfer cylinders  14 , the form cylinders  15 , the inking couples  16 , and the dampening units  17  of both printing couples  11 ,  12 , where the drive motor  18  drives these assemblies with the help of intermeshing drive gears. In  FIG. 1 , intermeshing drive gears are shown in broken line. Thus a drive gear assigned to the drive motor  18  drives a drive gear assigned to the transfer cylinder  14  of the printing couple  12 . The drive gear of the transfer cylinder  14  of the printing couple  12  drives a drive gear assigned to the form cylinder  15  of the printing couple  12  and the drive gear assigned to the transfer cylinder  14  of the printing couple  11 , where the drive gear of the transfer cylinder  14  of the printing couple  11  drives a drive gear assigned to the form cylinder  15  of the printing couple  11 . According to  FIG. 1 , the drive gear of the form cylinder  15  of each printing couple  11 ,  12 , acting by way of an intermediate gear  19 , drives the drive gear assigned to the inking couple roller of the inking couple  16  of the associated printing couple  11 ,  12 . The dampening unit  17  of the printing couple  11  can also be driven by additional drive gears. According to the prior art shown in  FIG. 1 , therefore, the inking couples  16  of the printing couples  11 ,  12  are driven by way of intermeshing drive gears, namely, by way of the drive gears assigned to the form cylinders  15  of the printing couples  11 ,  12 . 
     In the case of the printing unit  10  of  FIG. 1 , the circumference of the transfer cylinder  14  in the area of each of the two printing couples  11 ,  12  is a whole-number multiple of the circumference of the associated form cylinder  15 . The form cylinders  15  of the printing couples  11 ,  12  are therefore slender form cylinders  15  with a relatively small diameter and a relatively large axial dimension, as a result of which they tend to sag. 
     In the above-described drive connection between the inking couples  16  and the form cylinders  15  of the printing couples  11 ,  12  in question, there is therefore the problem that torque variations, which result from the inking couple  16  in question, can lead to elastic deformation of the journals of the form cylinders  15 , on which the drive gears of the form cylinders  15  are mounted. As a result, the center points of the drive gears of the form cylinders  15  can be shifted, which ultimately leads to the occurrence of doubling on the printed product and thus to a loss of achievable print quality. The greater the axial dimension of the form cylinders  15 , the greater the severity of this problem. 
     SUMMARY OF THE INVENTION 
     Against this background, the present invention is based on the goal of creating a novel printing unit of a printing press in which better print quality can be achieved using slender form cylinders. According to the invention, the inking couple of the printing couple or of each printing couple can be driven by the transfer cylinder of the printing couple in question by way of intermeshing drive gears in such a way that the drive connection between the transfer cylinder and the inking couple of the printing couple in question is independent of the drive connection between the transfer cylinder and the form cylinder of the printing couple in question. In the inventive printing unit, the inking couple of each printing couple is therefore driven not via the form cylinder of the printing couple in question but rather by the transfer cylinder of the printing couple in question. 
     In the inventive printing unit, therefore, there is no mechanical drive connection via gears in the area of the printing couples between the form cylinders and the printing couples. Because the circumference of the transfer cylinder is a whole-number multiple of the circumference of the form cylinder and the transfer cylinder is therefore stiffer overall, it is possible with the present invention to avoid doubling in printing couples with slender form cylinders and thus to increase print quality. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a printing unit of a web-fed printing press with two printing couples as known from the prior art; 
         FIG. 2  shows a side view of an inventive printing unit of a web-fed printing press with two printing couples; and 
         FIG. 3  shows a part of the printing unit of  FIG. 1  in a view rotated 90° versus  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
       FIG. 2  shows a schematic diagram of an inventive printing unit  20  of a web-fed printing press with two printing couples  21 ,  22 , which serve in turn to print both sides of a substrate web  23 . Each of the printing couples  21 ,  22  of the printing unit  20  of  FIG. 2  has in turn its own transfer cylinder  24 , its own form cylinder  25 , its own inking couple  26 , and its own dampening unit  27 , where the circumference of the transfer cylinder  24  is in each case a whole-number multiple of the circumference of the form cylinder  25  in question. 
     A drive motor  28 , which drives the transfer cylinder  24  of the printing couple  22 , is also assigned to the printing couple  22 , where, for this purpose, intermeshing drive gears are assigned both to the drive motor  28  and to the transfer cylinder  24 . As can be seen in  FIG. 2 , in which the drive gears are shown in broken line, the drive gear assigned to the transfer cylinder  24  of the printing couple  22  drives directly a drive gear assigned to the form cylinder  25  of the printing couple  22 . 
     Similarly, the drive gear assigned to the transfer cylinder  24  of the printing couple  22  drives a drive gear assigned to the transfer cylinder  24  of the printing couple  21 , where the drive gear of the transfer cylinder  24  of the printing couple  21  drives directly a drive gear assigned to the form cylinder  25  of the printing couple  21 . To this extent the printing unit  20   FIG. 2  is the same as the printing unit  10  of  FIG. 1 . 
     In the inventive printing unit  20  of  FIG. 2 , each of the inking couples  26  is driven in the area of each printing couple  21 ,  22  by a transfer cylinder  24 , which acts by way of intermeshing drive gears. For this purpose, two intermediate gears  29 ,  30  are provided by which the associated inking couple  26  is driven indirectly by the transfer cylinder  24 . In the inventive printing unit  20 , therefore, the drive connection between the transfer cylinders  24  and the inking couple  26  of the associated printing couple  21 ,  22  is independent of the drive connection between the transfer cylinder  24  and the form cylinder  25  of the printing couple  21 ,  22 , however, the intermediate gear  29  and the drive gear of the form cylinder  25  both mesh with the drive gear of the associated transfer cylinder  24 . As a result, torque fluctuations in the inking couple  26  are not transmitted to the relatively slender form cylinder  25  but are instead absorbed in the area of the stiff transfer cylinder  24 , the circumference of which is a whole-number multiple of the circumference of the form cylinder  25 . 
       FIG. 3  shows a part of the printing unit  20  in the area of the transfer cylinder  24  and of the form cylinder  25 . The form cylinder  25  and the transfer cylinder  24  are rotatably supported by their cylindrical journals  31 ,  32  on bearings  33 ,  34  in a side wall  35 , as shown. On the side of the side wall  35  facing away from the cylinders  24 ,  25 , drive gears  36 ,  37  are supported on the cylindrical journals  31 ,  32  of the form cylinder  25  and of the transfer cylinder  24 . 
     It can thus be derived from  FIG. 3  that the drive gears  36  are supported on the cylindrical journals  31  of the form cylinders  25 , and that the drive gears  37  are supported on the cylindrical journals  32  of the transfer cylinders  24 , where the drive gears  36 ,  37  of each printing couple mesh with each other. 
     For the drive gears  37  of the transfer cylinders  24 ,  FIG. 3  shows by way of example that these gears are attached to the cylindrical journals  32  of the transfer cylinders  24  in question by means of clamping elements  38 , which provide a torque-transmitting connection between the drive gear in question and the associated cylindrical journal. 
     In the area of each printing couple  21 ,  22 , the drive gears  36  and  37  of the form cylinder  24  and of the transfer cylinder  25  mesh with each other. This intermeshing is by nature subject to backlash. The backlash, however, may not be allowed to cause any technical printing problems. To ensure that no such problems occur, an auxiliary gear  39  and preferably an adjusting disk  40  are assigned to the drive gear  37  of each transfer cylinder  24 , as shown in  FIG. 3 . The auxiliary gear  39  has the same tooth geometry as the drive gear  37  of the transfer cylinder  24  to which the auxiliary gear  39  is assigned. The auxiliary gear  39 , furthermore, like the drive gear  37  of the transfer cylinder  24 , meshes with the drive gear  36  of the form cylinder  25 . In the area of each printing couple  21 ,  22 , the auxiliary gear  39  assigned to the drive gear  37  of the transfer cylinder  24  in question and the adjusting disk  40  assigned to the drive gear  37  in question are connected to the drive gear  37  by way of spring elements or flexible elements designed as flexible rods  41 . These flexible rods  41  are distributed uniformly around the circumference of the drive gear  37 , of the auxiliary gear  39 , and of the adjusting disk  40 , where the flexible rods  41  extend in the axial direction and pass through the adjusting disk  40 , the auxiliary gear  39 , and the drive gear  37  of the transfer cylinder  24 . 
     According to  FIG. 3 , the auxiliary gear  39  is screwed to a first side of the drive gear  37  by way of the flexible rods  41 . The adjusting disk  40 , however, is screwed to the second side of the drive gear  37  by way of the flexible rods  41 . The auxiliary gear  39  and the adjusting disk  40  therefore act on opposite sides of the drive gear  37  in question. 
     By rotating the adjusting disk  40  in the circumferential direction with respect to the drive gear  37  of the transfer cylinder  24 , the auxiliary gear  39  can be rotated with respect to the drive gear  37  of that transfer cylinder  24 . The rotation of the adjusting disk  40  versus the drive gear  37  in question and thus the rotation of the auxiliary gear  39  versus that drive gear takes place in such a way that, when, on the one hand, the drive gears  37 ,  36  mesh and, on the other hand/end, the auxiliary gear  39  assigned to the drive gear  37  meshes with the drive gear  36 , the driving tooth flanks of the two drive gears  37 ,  36  of the transfer cylinder  24  and of the form cylinder  25  rest against each other and, furthermore, the non-driving tooth flanks of the auxiliary gear  39  rest against the non-driving tooth flanks of the drive gear  36  of the form cylinder  35  of the associated printing couple  21 ,  22 . As a result, the intermeshing, which is subject by nature to backlash between the two intermeshing drive gears  36 ,  37  of the transfer cylinder  24  and the form cylinder  25  in the area of each printing couple, can be kept free of backlash. So that the adjusting disk  40  in question can be rotated versus the drive gear  37 , a cam  42  is assigned to the adjusting disk  40 . Between the auxiliary gear  39  and the drive gear  37 , a plain bearing is provided, especially a plain bearing made of plastic, to prevent the two components, which move only slightly with respect to each other, from rusting together. 
     The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.