Abstract:
The invention relates to an apparatus for image formation on cylindrical surfaces of printing machines.  
     Task of the invention is to establish a compact image formation unit with a broad application range regarding its usage, the sequence in time and variation in time of the process steps.  
     The task is solved according to the invention by processing units mounted on slides movable separately on a common cross bar. Each slide carries at least one processing unit. The cross bar is located in the godet between plate cylinder and blanket cylinder.

Description:
FIELD OF INVENTION  
         [0001]    The invention relates to an apparatus for image formation on cylindrical surfaces in printing machines consisting of multiple processing units arranged side by side and allocated to the plate cylinder of the printing machine. The processing units can me moved axially to the plate cylinder.  
         BACKGROUND OF INVENTION  
         [0002]    A printing machine with a printing unit having a gapless image cylinder, which is coated with a dryable polymer by a direct image formation process, is known through DE 19612927 A 1. The surface characteristic of this polymer layer on the image cylinder is changed completely or partially by a selective laser beam in order to changes its affinity to printing ink. The image cylinder is used instead a plate cylinder in a conventional offset press either in wet offset or dry offset printing. The image cylinder is cleaned from the image carrying layer after finishing printing. The layer must not be removed completely. The radiation source, the coating unit and the drying unit are arranged side by side on a spindle drive and moved by the spindle drive over the width of the cylindrical surface to be imaged. The cleaning unit is mounted separately.  
           [0003]    Disadvantage of this solution is the missing processing space caused by the number and fixed allocation of the processing units. The versatility of this apparatus is insufficient for many applications.  
         SUMMARY DESCRIPTION OF INVENTION  
         [0004]    Task of the invention is to establish a compact image formation unit with a broad application range regarding its usage, the sequence in time and variation in time of the process steps.  
           [0005]    The task is solved according to the invention by processing units mounted on slides movable separately on a common cross bar. Each slide carries at least one processing unit. The cross bar is located in the godet between plate cylinder and blanket cylinder.  
           [0006]    The advantage of this invention is the variability of using the single process steps. It is also possible to adapt the processing intensity of the single processing units to the process requirements by their time effecting the surface. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The invention is described below in greater detail by an embodiment of the invention, by reference being had to the drawing, wherein:  
         [0008]    [0008]FIG. 1: Schematic of the roller and cylinder scheme of a printing unit in a printing press with the invented apparatus in an embodiment with mounting on a cross bar  
         [0009]    [0009]FIG. 2: Schematic of the invented apparatus in an embodiment with mounting on a spindle drive  
         [0010]    [0010]FIG. 3: Schematic of the invented apparatus in an embodiment with mounting on a linear motor drive  
         [0011]    [0011]FIG. 4: Schematic of the roller and cylinder scheme of a printing unit in a printing press with the invent ed apparatus in an embodiment with mounting on two cross bars  
     
    
     DETAILED DESCRIPTION  
       [0012]    [0012]FIG. 1 shows the printing unit of a multi-color sheet fed offset press. The printing unit contains the impression cylinder  3  carrying the sheet and as the image transferring cylinders the plate cylinder  1  and the blanket cylinder  2 .  
         [0013]    An inking unit  4  and a dampening unit  5  is allocated to each plate cylinder  1 . The plate cylinder  1  can also carry a here not shown printing form.  
         [0014]    A cross bar  71  is located in the area of the godet between the plate cylinder  1  and the blanket cylinder  2 . The cross bar is located in a manner that other equipment in this area for instance the cleaning unit  16  are not obstructed in their operational space. The cross bar  71  carries the processing units  9 ,  10  and  11  for image formation on the surface of the plate cylinder  1  respectively a printing form mounted on the plate cylinder  1 .  
         [0015]    [0015]FIG. 2 shows the details of this embodiment. The cross bar  71  is mounted in the side frame  6  of the printing machine. The cross bar  71  stretches parallel to the surface of the plate cylinder  1  over the entire width of the printing press (see also FIG. 3). Parallel to the cross bar  71  is the spindle drive  8  is supported non-rotating in the pillow block  123 .  
         [0016]    The cross bar  71  and the spindle  8  are extending over the side frame  6 . Therefore the side frame  6  has a cut out  61  covered by housing  121 . The housing  121  is accessible by a coverable opening  124 .  
         [0017]    The first processing unit  9  is mounted on a slide  91 . This slide  91  is connected with a first motor  92  driving a first spindle  93 . The first spindle  93  is in an operational connection to the fixed spindle  8 . The first slide  91  carries also the erasing unit with an erasing head  94  and a suction  95  with a suction hose  96 . The erasing head  94  is embodied as a high-energy laser. The erasing head  94  must be located before the suction  95  in the moving direction of the first slide  91  (see arrow in FIG. 2).  
         [0018]    The first processing unit  9  is followed by the second processing unit  10  in the moving direction of the processing units  9 ,  10  and  11 . This unit is also mounted on a slide  101  and has a motor  102  and a spindle  103  of the same configuration. The slide  101  carries here the coating unit  104 . The coating unit is embodied as an ink jet printing head.  
         [0019]    The next and in this embodiment last processing unit is in the processing sequence the third processing unit  11 . It has as described above analogue to the processing units  9  and  11   a  motor  112  and a spindle  113 . The slide  111  carries an image formation unit and a fixation unit  115 .  
         [0020]    The FIGS. 1 and 2 do not show the supply cables and supply hoses to simplify these representations.  
         [0021]    The operation of the above-described embodiment is explained in the following.  
         [0022]    The three processing units  9 ,  10  and  11  are in its parking position on the side frame  6  at the beginning of the image formation process. They are partially or completely covered by the housing  121 .  
         [0023]    The first processing unit  9  moves in the arrow direction to the plate cylinder  1  for image formation. The motor  92  starts its operation and rotates the spindle  93 . The slide  91  is moved in the designated direction because the spindle  8  is non-rotating supported. The plate cylinder  1  rotates with an appropriate speed for this process.  
         [0024]    The erasing head  94  is activated if the plate cylinder  94  is reached. The laser of the erasing head  94  erases the image information respectively removes the image layer of the preceding printing job from the plate cylinder  1 . The suction  95  takes the loosened particles and removes them from the printing machine. The first processing unit reaches its park position at the opposite side of the side frame  6  after the complete removal of the old image layer. A housing  122  analogue to the housing  121  is provided for this purpose.  
         [0025]    The so prepared surface of the plate cylinder  1  is now coated by the coating unit  104  in the second processing unit  10  with a layer to be imaged. The movement of this second processing unit  10  realized is analogue to the first processing unit  9 . This process starts typically immediately after removal of the old layer respectively the old image information. The second processing unit  10  takes its park position also on the opposite side after finishing coating.  
         [0026]    The third processing unit  11  is now started as the last processing step after the required hardening time of the applied layer passed. The third processing unit  11  moves in the described manner over the surface of the plate cylinder  1 . The actual image information is applied by the laser of the imaging unit  114  and hardened by the fixation unit  115  during this movement.  
         [0027]    The processing units  9 ,  10  and  11  take their park positions on the opposite side after image formation. The printing process can now start. It is advantageous to move the processing units  9 ,  10  and  11  back to their original position before printing. The speed of this movement is a multiple of the processing speed. The processing units  9 ,  10  and  11  can moved one after the other or together in complex.  
         [0028]    The embodiment described above is only one possible embodiment. It is for instance also possible to insert or to integrate an additional processing unit after the second processing unit  10  to harden the layer if technically required. A unit for cleaning and developing can be also inserted after the third processing unit  11 .  
         [0029]    [0029]FIG. 3 shows the parking positions of the processing units after image formation. The FIG. 3 shows also another embodiment of the invention. The processing units  9 ′,  10 ′ and  11 ′ are equipped with linear motors  131 ,  141  and  151 . They are connected to the cross bar  71  through the drive members  132 ,  142  and  152 . The operation is the same as described above.  
         [0030]    [0030]FIG. 4 shows an embodiment with two cross bars  72  and  73 . This arrangement has the advantage that in embodiments with more processing units these units can be distributed between the two crossbars  72  and  73 . This results in better space distributions and more room in the parking positions in the adjacency of the side frame  6 . With it the processing units can be driven either by linear motors  131 ,  141  and  151  or with motors  92 ,  102  and  112 .