Abstract:
An apparatus positions a plate cylinder and a blanket cylinder in a transport position for assisting in transporting printing plates. The apparatus spaces the blanket cylinder and plate cylinder apart from one another such that a pressure acting on a printing plate during the printing operation is reduced in the transport position. Optionally, one of the cylinders can be replaced with an inking and/or damping roller.

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to a method and an apparatus for transporting plate-shaped material, in particular a printing plate, by use of cylinders of a printing press. 
   It is known, when feeding printing plates to the plate cylinder of a printing press or removing the used printing plate from the plate cylinder of the printing press, to use cylinders or rollers which interact with the plate cylinder during printing operation. This is, for example, the blanket cylinder or the ink or damping solution applicator rollers. 
   International patent disclosure WO 94/06630 (corresponding to U.S. Pat. No. 5,540,151) shows a plate cylinder of a rotary press, which plate cylinder interacts with one of the ink or damping solution applicator rollers when the used printing plate is removed, in order to transport the printing plate into a printing plate store. 
   During the transport of the printing plate by manipulating the contact pressure, as is required for the printing operation, it can lead to uncontrolled adhesion of the plate to the blanket cylinder or to the ink or damping solution applicator rollers, in particular during the transport of a used printing plate in conjunction with ink or detergent residues on the printing plate, and thus to interruptions of the unclamping procedure or even to damage being caused to the printing plate. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide a method and an apparatus for the transport of printing plates which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type. 
   With the foregoing and other objects in view there is provided, in accordance with the invention, a method for transporting printing plates between two cylinders of a printing press which interact during a printing operation. The method includes using a plate cylinder and a blanket cylinder of the printing press as the two cylinders interacting during the printing operation. The plate cylinder and the blanket cylinder are positioned in a transport position for transporting the printing plates, spaced apart from one another such that pressure acting on a printing plate during the printing operation is reduced in the transport position. Instead of using the blanket cylinder, at least one ink and/or damping solution roller in place of the blanket cylinder. 
   It is a particular advantage of the invention that, in particular, the blanket cylinder is used for transporting the plates. The blanket cylinder has a throwing-on and throwing-off apparatus that is particularly suitable for modification to set a desired transport gap between the blanket cylinder and the plate cylinder, in order that the plate can be transported with a predefined pressure by the rotation of the two cylinders. 
   A particularly advantageous solution for producing the desired pressure relates to the reduction of the pivoting path of the blanket cylinder from a “thrown-off” or “service” position into the “thrown-on” or “operating” position by the arrangement of an adjustable stop. In one advantageous refinement, the adjustable stop can be actuated pneumatically and can thus be adjusted remotely, in particular can be adjusted remotely automatically. The stop is disposed on the actuating element for the blanket cylinder adjusting system. 
   Other features which are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in a method and an apparatus for the transport of printing plates, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic, side-elevational view of a sheet-fed rotary printing press; and 
       FIG. 2  is a diagrammatic, sectional view through a printing unit according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a machine which processes sheets  7 , for example a printing press  1 . The printing press  1  has a feeder  2 , at least one printing unit  3  and  4  and a deliverer  6 . The sheets  7  are taken from a sheet stack  8  and, separated or overlapped, are fed over a feed table  9  to the printing units  3  and  4 . The latter each contain a plate cylinder  11 ;  12  in a known manner. The plate cylinders  11  and  12  each have a device  13 ,  14  for fastening flexible printing plates. Furthermore, each plate cylinder  11 ;  12  is assigned a device  16 ;  17  for semiautomatic or fully automatic printing plate change. 
   The sheet stack  8  lies on a stack board  10  which can be raised under control. The removal of the sheets  7  takes place from the top of the sheet stack  8  by a suction head  18 , as it is known, which inter alia has a number of lifting and dragging suckers  19 ,  21  to separate the sheets  7 . Furthermore, blowing devices  22  for loosening the top sheet layers and sensing elements  23  for tracking the stack are provided. In order to align the sheet stack  8 , in particular the top sheets  7  of the sheet stack  8 , a number of side and rear stops  24  are provided. 
     FIG. 2  shows the first printing unit  3  with the plate cylinder  11  and a blanket cylinder  26  which can be moved into operative connection with the latter. The blanket cylinder  26  is mounted rotatably in side frames of the printing press  1 , in each case by a double eccentric mounting  27 . The blanket cylinder  26  can be pivoted by a first pivoting movement of the double eccentric mounting  27  from a “thrown-on” operating position into a service position or “thrown-off” position. In the “thrown-off” or service position, the blanket cylinder  26  is positioned without contact to the plate cylinder  11  and without contact to an impression cylinder  28 . 
   In order to transport a printing plate  29 , in particular in order to remove the used printing plate  29  from the plate cylinder  11 , into a printing plate store device, disposed for this purpose ahead of the printing unit  3 , of the printing plate changing device  16 , the blanket cylinder  26  is pivoted by a pivoting movement of the double eccentric mounting  27  into a transport position. In the transport position, the blanket cylinder  26  is spaced apart from the impression cylinder  28  but is at a small transport gap S from the plate cylinder  11 . The transport gap S is configured in such a way that a light transport pressure is exerted onto the printing plate  29  by the plate cylinder  11  and the blanket cylinder  26 . 
   A linkage is provided to pivot the double eccentric mounting  27 , which linkage contains a connecting rod  32  and a coupler  33  which is articulated on the former, the connecting rod  32  and coupler  33  each acting on one end on the double eccentric  27 . A second end of the connecting rod  32  is articulated on a two-armed rocker arm  34  which is mounted pivotably on the side frame of the printing press. The pivoting movement is caused by an actuating element  36 . 
   In the exemplary embodiment, the actuating element  36  is a double stroke cylinder  36  with a first piston rod  37  which is articulated on a second arm of the rocker arm  34  and has a first piston  38  at its end, which piston  38  is disposed in a first cylinder body  39 . The first cylinder body  39  is adjoined by a second cylinder body  41  which has a second piston  42  with a second piston rod  43  disposed on it. The two cylinder bodies  39 ,  41  are connected to one another at their bases  44  and thus form a single component. That end of the piston rod  43  that lies opposite the second piston  42  is mounted pivotably on a bolt  45  which is fixed to the side frame. At the same time, the bolt  45  bears a pivotable stop  48  which interacts with an adjustable stop  47  which is fixed to the cylinder and disposed on a stop bracket  46 . 
   The exhaust work of the cylinder  41  is limited, depending on the position of the stop  48 . In order to limit the displacement path of the second cylinder  41 , the stop  48  is pivoted out of a first position into a second position. The pivoting movement is produced by an operating cylinder  49  which is fastened to the side frame and can be acted on, for example, pneumatically. The operating cylinder  49  can be configured such that it can be adjusted remotely from the control desk of the machine as a function of the machine mode. 
   If the blanket cylinder  26  is to be moved into the “service position”, both piston rods  37  and  43  are retracted fully. The operational positioning of the blanket cylinder  26  for continuous printing is carried out by the extending both of the first piston rod  37  and of the second piston rod  43 . In this position, the stop  48  is pivoted away. 
   In the “transport position” for the printing plate  29 , the blanket cylinder  26  is set away from the impression cylinder  28  and is situated in a relatively close position compared with the plate cylinder  11 , which position forms the transport gap S. In this position, the operating cylinder  36  has a fully retracted first piston rod  37  and a partially extended piston rod  43 . Here, the stop  48  is pivoted by the operating cylinder  49  in such a way that it interacts with the stop  47 . 
   The printing plate  29  can then be transported under slight transport pressure, preferably transported away from the plate cylinder, by rotation of the plate cylinder  11  and the blanket cylinder  26 . Here, an angled-away edge of the printing plate  29  passes into a holding device  51  which is configured to hold the printing plate  29 , in accordance with German patent DE 195 07 908 C2 (corresponding to U.S. Pat. No. 5,649,487). 
   The blanket cylinder  26  is described merely as a preferred exemplary embodiment for transporting the printing plate in interaction with the plate cylinder  11 . It goes without saying that it is also possible to use the ink applicator rollers  52 ,  53 ,  54 ,  55  or damping solution applicator rollers  56  individually or together or else together with the blanket cylinder  26  for transporting the printing plate  29 , as long the rollers are positioned in a corresponding transport position, in which the spacing S is set between them and the plate cylinder  11 . 
   This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 022 213.4, filed May 4, 2004; the entire disclosure of the prior application is herewith incorporated by reference.