Abstract:
An apparatus for separating printing plates which are separated from one another in a stack, preferably individually by intermediate layers, has a lifting device for raising a printing plate or an intermediate layer from the stack. The apparatus further has a separating device for the intermediate layers, in particular as a constituent part of a loading device of a unit for setting images on printing plates. The separating device is configured as a rocker which can be pivoted onto the lifting device and can be pivoted away from the lifting device and contains suction elements and one drivable transport roller. An adhering intermediate layer is pulled off from the printing plate with the suction elements, and the intermediate layer is transported away with the transport roller.

Description:
BACKGROUND OF THE INVENTION  
     Field of the Invention  
       [0001]     The invention relates to an apparatus and a method for separating printing plates which are separated from one another in a stack, preferably by intermediate layers. The apparatus has a lifting device with at least one suction element for raising a printing plate from the stack, and a separating device for the intermediate layers, in particular as a constituent part of a loading device of a unit for setting images on printing plates.  
         [0002]     An apparatus of the above-mentioned generic type is known from the published, non-prosecuted German patent application DE 10 2004 015 195.4 A1, corresponding to U.S. patent publication No. 2005/0230901 A1.  
         [0003]     The lifting device of the known apparatus has at least two suction elements which are independent of one another, of which one suction element can be pivoted or angled away relative to the other suction elements. If the suction elements are angled away with respect to one another after attracting the printing plates by suction and raising them, the printing plate which is attracted by suction is bent somewhat as a result. As a result of the bending, an object which still adheres to the printing plate falls off, which object could be an intermediate layer or a further printing plate. This can therefore obviate the need for a separate separating device for the intermediate layers.  
         [0004]     Nevertheless, an additional separating device for separating and transporting the intermediate layers away is appropriate, in order to ensure a reliable and controlled operation for all types of printing plates and intermediate layers during the separation of printing plates.  
       SUMMARY OF THE INVENTION  
       [0005]     It is accordingly an object of the invention to provide an apparatus and a method for separating printing plates which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which has a separating device configured to be as compact as possible, preferably also for easy retrofitting.  
         [0006]     With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for separating printing plates stacked in a tray alone and/or for separating printing plates stacked in the tray separated from one another individually by intermediate layers. The apparatus contains a lifting device for raising a printing plate or an intermediate layer from a stack. The lifting device contains at least one suction head and is moveable in a movement plane in a substantially horizontal direction. A separating device is provided for removing the intermediate layers. The separating device has a rocker being pivotable to the movement plane and being pivotable away from the movement plane. The rocker contains at least one suction element and one drivable transport roller.  
         [0007]     According to the invention, the object is achieved in that the separating device is configured as a rocker which can pivot to and away from the lifting device, attracts an intermediate layer by suction by suction elements, which intermediate layer adheres to a printing plate and is composed of paper as a rule, peels the intermediate layer from the printing plate by pivoting the rocker away, and transports it into a collecting container by a driven transport roller.  
         [0008]     A sensor, preferably an ultrasound sensor, detects whether the lifting device has gripped only one printing plate, only one intermediate layer or an adhering combination of the printing plate and the intermediate layer. Depending on the situation which is detected, different methods are started for the possibly necessary separation of the printing plate and the intermediate layer and for the further transport of the materials.  
         [0009]     Other features which are considered as characteristic for the invention are set forth in the appended claims.  
         [0010]     Although the invention is illustrated and described herein as embodied in an apparatus and a method for separating 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.  
         [0011]     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  
       [0012]      FIG. 1  is a diagrammatic, vertical sectional view through a lifting device of a unit for setting images on printing plates according to the prior art;  
         [0013]      FIG. 2  is a diagrammatic, side view of an external drum exposer having the lifting device and a separating device positioned thereon according to the invention;  
         [0014]      FIG. 3  is a diagrammatic, vertical sectional view through the separating device and the lifting device;  
         [0015]      FIG. 4  is an illustration of an intermediate layer being transported away;  
         [0016]      FIG. 5  is an illustration showing an adhering intermediate layer being separated;  
         [0017]      FIG. 6  is an illustration showing the separating device having an additional clamping jaw;  
         [0018]      FIG. 7  is an illustration showing an adhering printing plate being detached; and  
         [0019]      FIG. 8  is a diagrammatic, side view of the external drum exposer having the lifting device and the separating device integrated into the cover. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a diagrammatic vertical sectional view through a lifting device  16  above an entry slide of a unit for setting images on printing plates, as is known from the published, non-prosecuted German patent application DE 10 2004 015 195.4 A1.  
         [0021]     The lifting device  16  contains a suction unit  1  with suction heads  2 ,  3  above a stack of printing plates  4 , which stack is positioned on a tray  5  which for its part is pushed into a type of shell  6 . The tray  5  can also be a cassette which is open on its upper side.  
         [0022]     The shell  6  is mounted on springs  7  and can be moved to and fro with an actuator  8  along a guide  9  in the direction of a double arrow  10 , in order to keep the printing plate level uniform as the stack height changes.  
         [0023]     The suction unit  1  can be moved horizontally in a direction of double arrow  11  while driving a printing plate  4 ′ which is attracted by suction, to be precise until over an entry slide  13  of a unit (not shown in greater detail) for setting images on printing plates. The moved suction unit  1 ′ with its suction heads  2 ′,  3 ′ is shown with dashed lines, in the same way as the printing plate  4 ′ attracted by suction.  
         [0024]     As shown, the suction head  3 ′ can be angled or tilted with respect to the suction head  2 ′, with the result that the printing plate  4 ′ is bent or tilted slightly in the intermediate region by both suction heads  2 ′,  3 ′. As the printing plate  4 ′ is no longer flat as a result, an object which possibly adheres to the underside falls off. This does not necessarily have to happen above the entry slide  13 , but can also happen at a different location. For example, the suction unit  1  in the illustration of  FIG. 1  could be moved initially to the left to the side which faces away from the entry slide  13 , in order to discharge, for example, an intermediate layer there which adheres to the printing plate  4 ′, and could subsequently move into the position over the entry slide  13 . The printing plate  4 ′ is also pretensioned there in the direction of an arrow  12  toward the entry slide by the tilting of the suction head  3 ′. If the suction head  2 ′ is then switched off and the printing plate  4 ′ is still held only by the suction head  3 ′, that edge of the printing plate  4 ′ which is then free falls initially onto the entry slide  13  in the direction of the arrow  12 . If the suction head  3 ′ is also switched off subsequently, the printing plate falls completely onto the entry slide  13 ; the printing plate will be situated transitionally approximately in the position  4 ″ before it rests flat on the entry slide  13 . On the entry slide  13 , the printing plate  4 ″ is then conveyed into the unit for setting images on printing plates via the assistance of transport rollers  14 .  
         [0025]      FIG. 2  shows a side view of an external drum exposer for printing plates, onto which the lifting device  16  has been positioned. The cassette  5  with printing plates is pushed in under the lifting device  16 . The lifting device  16  contains the suction unit  1  which cannot be seen in  FIG. 2 , however, and which can be moved along the double arrow  11  over the entry slide  13 . After image setting, the printing plates can be removed from a printing plate delivery device  17 .  
         [0026]     According to the invention, a separating device  18  for the intermediate layers is added to the loading device, which separating device  18  operates in conjunction with the lifting device  16  described. The separating device  18  is preferably disposed at the level of the lifting device  16  on that side of the printing plate exposer which lies opposite the entry slide  13  (see  FIG. 2 ).  
         [0027]      FIG. 3  shows a diagrammatic vertical section through a preferred embodiment of the separating device  18  together with the lifting device  16 . The separating device  18  contains a pivotable rocker  20  which can be pivoted about a pivot point  21  onto the horizontal movement plane  22  of the lifting device  16  or can be pivoted away from the movement plane  22  (shown with dashed lines in  FIG. 3 ). The pivoting movement is carried out by a non-illustrated pivoting drive, for example by an electric motor. At least one suction element  23  is integrated into the rocker  20 , with which suction element  23  an object which lies on the upper side of the rocker  20  can be attracted by suction via non-illustrated suction holes in the rocker  20 . Suction fans or else suction cups which are connected to a vacuum generator can be used, for example, as the suction elements  23 . Furthermore, the rocker  20  contains a driven transport roller  24  for transporting away the object which rests on it. Discharge brushes  41  for conducting away an electrostatic charge from the object which is being transported away can also be integrated into the transport roller  24  or into the rocker  20 .  
         [0028]     The lifting device  16  is provided with a first sensor  25 , for example with a capacitive sensor, which can be used to detect whether the object which is raised by the lifting device  16  or, in the case of a plurality of adhering objects, the uppermost of the raised objects is a printing plate or an intermediate layer. Furthermore, a second sensor  26 , for example an ultrasound sensor, is attached in the vicinity of the separating device  18 , which second sensor  26  can be used to detect whether a plurality of adhering objects have been raised by the lifting device  16 . To this end, the raised objects are moved by the lifting device  16  over the second sensor  26  in the movement plane  22 . The first sensor  25  and the second sensor  26  can be used together to detect the different possible situations, namely whether:  
         [0029]     only one printing plate has been raised;  
         [0030]     only one intermediate layer has been raised;  
         [0031]     a printing plate has been raised together with an intermediate layer which adheres to the bottom of the former;  
         [0032]     an intermediate layer has been raised together with a printing plate which adheres to the bottom of the former; and  
         [0033]     a printing plate has been raised together with a plurality of intermediate layers and/or printing plates which adhere to the bottom of the former.  
         [0034]     If only one printing plate has been raised, the printing plate is transported horizontally by the lifting device  16  over the entry slide  13  and is deposited into the entry slide  13 .  
         [0035]      FIG. 4  shows the situation where only one intermediate layer  30  has been raised. In this case, the intermediate layer  30  is transported horizontally by the lifting device  16  over the separating device  18 , and the rocker  20  is pivoted into the movement plane  22 , with the result that the intermediate layer  30  is clamped between the transport roller  24  and a back pressure roller  28  which is attached to the lifting device  16 .  
         [0036]     After the suction unit  1  is switched off, the intermediate layer  30  is then transported away into a collecting container  31  by the transport roller  24 .  
         [0037]      FIG. 5  shows the situation where a printing plate  4  has been raised together with an intermediate layer  30  which adheres to the bottom of the printing plate. First, the two adhering objects are transported horizontally by the lifting device  16  over the separating device  18 , and the rocker  20  is pivoted into the movement plane  22 . The adhering intermediate layer  30  is then attracted by suction with the suction elements  23 , and the rocker  20  is pivoted away from the movement plane  22  again, the intermediate layer  30  being peeled partially from the printing plate  4 . Subsequently, the lifting device  16  transports the printing plate  4  over the entry slide  13  and deposits it there. Here, the intermediate layer  30  continues to be held firmly by the suction elements  23 , with the result that it is detached completely from the printing plate  4  during the transport of the printing plate  4 . After this, the lifting device  16  is positioned over the separating device  18 , and the rocker  20  is pivoted into the movement plane  22  again, with the result that the intermediate layer  30  is clamped between a transport roller  24  and a back pressure roller  28 . After the suction unit  1  and the suction elements  23  are switched off, the intermediate layer  30  is transported away into the collecting container  31 , as is shown in  FIG. 4 .  
         [0038]     The firm holding of the intermediate layer  30  while the printing plate  4  is being transported away can also be assisted by a clamping jaw  32  which is integrated additionally into the rocker  20 , as is shown in  FIG. 6 . The clamping jaw  32  is mounted rotatably in the rocker  20  and clamps the intermediate layer  30  firmly on the upper side of the rocker  20 . The clamping jaw  32  is preferably coupled mechanically to the pivoting movement of the rocker  20 , in such a way that it is moved into the shown clamping position when the rocker  20  is pivoted away from the movement plane  22 . This mechanical coupling could take place, for example, by gearwheels which convert the pivoting movement of the rocker  20  into a suitable rotational movement of the clamping jaw  32 .  
         [0039]      FIG. 7  shows the situation where an intermediate layer  30  has been raised together with a printing plate  4  which adheres to the bottom of the intermediate layer. In this case, the raised intermediate layer  30  and the adhering printing plate  4  are positioned over the tray  5  by the lifting device  16 . The suction head  3  is then switched off, with the result that those ends of the intermediate layer  30  and the printing plate  4  which are no longer attracted by suction hang down into the tray  5 . A stop  33  is situated in the tray  5 , against which stop  33  the lifting device  16  subsequently moves both raised objects. Here, the printing plate  4  is blocked by the stop  33  and, during the further movement of the lifting device  16  (to the right in  FIG. 7 ), the printing plate  4  is detached from the intermediate layer  30  and falls back into the tray  5 . After this, the intermediate layer  30  is transported horizontally by the lifting device  16  over the separating device  18 , and the intermediate layer  30  is transported away into the collecting container  31  using the process which is explained with reference to  FIG. 4 .  
         [0040]     If a printing plate has been raised together with a plurality of intermediate layers and/or printing plates which adhere to the bottom of the former, the loading device outputs a disruption signal, in order that the operator can intervene and eliminate the disruption manually. In order to make this easier, the lifting device  16  and the separating device  18  are advantageously integrated into a cover  40  of the printing plate exposer. The lower side of the lifting device  16  and the separating device  18  are made readily accessible to the operator by folding up the cover  40  ( FIG. 8 ).  
         [0041]     This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2005 035 325.8, filed Jul. 28, 2005; the entire disclosure of the prior application is herewith incorporated by reference.