Abstract:
In order cost effectively and in spite of the lowest possible expenditure on construction to permit the logical provision of printing plates of different types and sizes for an extremely wide range of printing plate exposers, in an apparatus for loading and/or unloading an exposer, in particular a drum exposer, with printing plates, having a suction means comprising at least one sucker plate and at least two suction heads connected to a vacuum system for picking up printing plates, in particular thermal printing plates, and a pivoting device for pivoting the suction means, it is proposed that the sucker plate be constructed in the form of a cylindrical segment and the suction means be pivotable about an axle which is arranged substantially parallel to the axis of the cylindrical segment.

Description:
RELATED DOCUMENTS  
         [0001]    This patent application is a continuation-in-part application of the international patent application PCT/CH02/00124 which international patent application includes the designation of the USA and which international patent application is incorporated by reference, hereby.  
         FIELD OF THE INVENTION  
         [0002]    The invention relates to an apparatus for loading and/or unloading an exposer (output scanner, output recorder), in particular a drum exposer, with printing plates, comprising a suction means and a pivoting device for pivoting the suction means. The invention also relates to a printing system and process based on this apparatus.  
         TECHNICAL BACKGROUND  
         [0003]    Books, newspapers, brochures or other products to be printed are produced by means of different printing processes. The production of such printed products can be carried out, firstly, by conventional printing processes, such as planographic, relief, gravure or screen printing and, secondly, by digital processes, such as the computer-to-plate (CTP) technique. In the case of offset printing, the printed products are produced by using printing forms. In this case, the image or the text to be printed is transferred to printing form blanks—also called printing plates. In this case, a light-sensitive layer applied to a metal or plastic plate, based on silver or made of a photopolymer, is exposed by means of UV radiation. In addition, in particular in the area of the CTP technique, thermal plates are also used, on which an image can be set by the action of specific temperatures. Lasers are suitable both for exposing photosensitive plates and for setting images thermally. The size of the printing plate to be produced depends on the object to be printed. For all the processes in printing technology, an extremely wide range of plate formats belong to the prior art. In the area of the CTP technique, a series of systems for setting images on printing plates with an extremely wide range of formats have been known for a long time, such as the Laserstepper from Misomex, the Laserstar from Krause or Xpose! from the Lüscher company.  
           [0004]    In printing technology, time is a key component. Automation of the production of printing plates is therefore a logical consequence. This is because fully automatic printing plate production as one operation in the entire printing process accelerates the throughput and increases the productivity of a print shop.  
           [0005]    DE-A 40 38 544 describes an apparatus for producing printing plates. In this case, the plate blanks are arranged in stacks on stack carriers inside a magazine. This magazine contains a circulating conveyor constructed as a paternoster and driven, having a plurality of stack carriers arranged one behind another. The stack carriers can be removed from the magazine in the horizontal direction by means of a displacement device and can be conveyed onto the copying table by a holding or feeding apparatus. This feeding apparatus comprises a suction frame with suckers. The suction frame can be moved in the horizontal and vertical plane and, can transfer a plate blank to a copying table. The disadvantage with this apparatus is, in particular, the complicated elevator mechanism within the magazine.  
           [0006]    The apparatus described in DE-C1 41 05 269 for loading and unloading printing plates is less complicated than the apparatus described previously. Here, the plate blanks, likewise mounted in cassettes, are stacked in the manner of a tower as a magazine. The individual plate blanks can be transferred from a desired cassette to the copying table by means of a feeding apparatus. For this purpose, the cassettes can be moved in the horizontal plane out of the magazine, so that the feeding apparatus can have access to the individual plate blanks. Not every cassette can be moved individually out of the tower; instead in each case the part of the tower is moved out, so that the desired cassette with the printing plates is arranged at the top. The feeding apparatus in turn comprises a rotary star, to whose projecting pivoting arms suction heads are fixed.  
           [0007]    The disadvantage with the apparatuses described in DE-A 40 38 544 and DE-C 41 05 269 is that they are not capable of loading cylindrical drum exposers.  
           [0008]    EP-A 0822 453 describes an apparatus and a method for picking up and transporting printing plates into an automated exposure device. A large number of printing plates is stored in the form of stacks in cassettes or magazines. Here, different magazines can contain different plate formats. The plate removal described in the application is carried out by a feeding apparatus. For this purpose, the desired plate formats are arranged by means of a complex elevator mechanism such that they can be reached by the feeding apparatus. The feeding apparatus comprises a horizontally arranged and horizontally displaceable plate with suction heads, by means of which heads the plate on which an image is to be set can be picked up by vacuum. The disadvantage with this apparatus is, in particular, the complicated elevator mechanism. In addition, this application does not provide any solution as to how the planar printing plate can ultimately be put into the cylindrical drum exposure by the feeding apparatus, on which it is arranged by means of vacuum, as described.  
           [0009]    An apparatus for loading drum exposers is disclosed by EP-A 0887 181. In this case, a printing plate which is arranged in a planar fashion by means of vacuum on a feeding apparatus is inserted into a cylindrical drum exposer with the aid of a loading device. The printing plate is transferred from the feeding apparatus to the loading device via rotating rolls. The loading apparatus in turn moves over rails along the inner surface of the drum exposer, carrying the printing plate with it. The same loading device can move in the opposite direction and, as a result, can transfer a printing plate on which an image has already been set out of the drum exposer to a developing machine arranged downstream. The disadvantage with this device is its complexity. Firstly, there must be a roll system to remove the printing plate from the feeding apparatus and, secondly, specific rail systems have to be arranged on a drum exposer so that the loading device can move along the internal drum. In addition, this apparatus is suitable only for loading internal drum exposers.  
           [0010]    The prior art likewise includes apparatuses for printing plate loading and unloading which can be obtained on the market, such as the plate loading system (PHS) relating to the “Xpose!” CTP exposer from the Lüscher company. In this apparatus, the printing plates are stored in a planar fashion and in stacks in cassettes. These cassettes are arranged on one another and can be moved out of the front side in the horizontal direction. The feeding apparatus comprises a cylinder and a device for positioning the cylinder. The cylinder is mounted on the positioning device such that it can be rotated with respect to its longitudinal axis. Arranged on the cylinder are suction heads which are connected to a vacuum system. By means of the positioning device, the cylinder can be moved both in the vertical and in the horizontal direction. In order to pick up a printing plate, a cassette is pushed horizontally out of the cassette stack and the cylinder is lowered vertically onto the printing plate until the suction heads make contact with the printing plate. The cylinder is rotated over the printing plate by means of a horizontal movement of the positioning device with the vacuum switched on, as a result of which the topmost printing plate of a cassette is firmly held on the outside of the cylinder as the cylinder rotates. By means of the vertical drive of the positioning device, the cylinder is drawn upward, together with the printing plate. The cylinder with the printing plate which has been picked up is then moved over the drum of the exposer by means of a horizontal displacement by the positioning device. Using the vertical drive of the positioning device, the cylinder with the printing plate is positioned on the inside of the drum, and the printing plate is inserted into the drum by switching off the vacuum. In order to remove the printing plate on which an image has been set, the same sequence of movements is carried out in the opposite order, with the difference that the printing plate is not put back again into the cassette from which it was removed but is placed in or on a carrier, which can be arranged instead of a cassette. This carrier is then connected to a developing device. The apparatus described is also capable of removing intermediate papers, which are located between the individual printing plates in order to protect the side on which an image is to be set, by means of the same mechanism described above. This can be done, for example, while a printing plate is having an image set on it. The disadvantage with this apparatus is its complexity. Firstly, a cylinder that can be rotated about its axis and has suction heads is needed. Secondly, a device which can be moved both in the vertical and in the horizontal direction is needed to position the cylinder. In addition, the size of the apparatus is disadvantageous.  
         SUMMARY OF THE INVENTION  
         [0011]    The object of the present invention is, therefore, to provide an apparatus which, cost effectively and in spite of the lowest possible expenditure on construction, permits the logical provisioning of printing plates of different types and sizes for an extremely wide range of types of printing plate exposers. In particular, this apparatus is intended likewise to be suitable for loading and unloading drum exposers. Additionally, the apparatus is to be cost-effective and space-saving.  
           [0012]    A further object of the present invention is to provide a printing system and a method with which exposers, in particular drum exposers, can be loaded efficiently with printing plates and unloaded.  
           [0013]    The object is achieved by an apparatus for loading and/or unloading an exposer, in particular a drum exposer, having printing plates with a suction means, comprising at least one sucker plate and at least two suction heads connected to a vacuum system, for picking up printing plates, in particular thermal printing plates, a pivoting device for pivoting the suction means, wherein the sucker plate is constructed in the form of a cylindrical segment and the suction means can be pivoted about an axis which is arranged substantially parallel to the axis of the cylindrical segment.  
           [0014]    These measures advantageously permit the simplified and therefore cost-effective production and use of the apparatus according to the invention. In addition, these measures permit a space-saving design of the apparatus.  
           [0015]    A very simplified pick-up device is possible on account of the suction means according to the invention, the suction means comprising a sucker plate and suction heads. In this connection, a plate is to be understood not to mean a flat, planar surface, but rather the plate has the shape of a cylindrical segment. On account of this shape, it is possible to discharge a printing plate which has been picked up to a cylindrical drum exposer, without a loading device additionally having to be arranged. According to the invention, the suction means can be pivoted about an axle which is arranged substantially parallel to the axis of the cylindrical segment. The suction means substantially maintains its axial alignment when pivoted. In this case, the sucker plate is aligned axially by the force of gravity.  
           [0016]    A further developed embodiment of the invention provides for the use of a sucker plate which is designed such that it can be deformed in relation to its surface form. In this case, the sucker plate can be fixed by webs to an upper axle of the apparatus, it being possible for the angle or the distance between the webs to be varied.  
           [0017]    According to one aspect of the invention, the sucker plate can be deformed by means of spindles with a spindle drive, and the webs can be constructed as pneumatic cylinders. In a development of the invention, the sides of the sucker plate, which are arranged parallel to the axis of the cylindrical segment, can be deformed more easily with respect to the surface form than the center of the sucker plate.  
           [0018]    By means of the pivoting movement, the pick-up apparatus can reach different heights. In the case of an apparatus having a plate magazine, therefore, it is possible to dispense with a complicated elevator mechanism which brings the cassettes or printing plates into a position accessible to the pick-up apparatus. In this case, simple drawer systems can be used, in which the printing plates are stacked. The pick-up device is constructed in such a way that, by means of the arcuate pivoting movement of the suction means, all the drawers of a plate magazine can be reached. Use is preferably made of such drawers which permit the printing plates to be stored without the influence of light.  
           [0019]    In an advantageous refinement of the invention, the base plate or an insert at the bottom of a drawer is curved convexly. A printing plate stack which is stored in a drawer consequently likewise has such a curvature. In this case, the radius of the curvature is matched approximately to the radius of the sucker plate. This measure makes possible the use of a large number of different printing plate formats.  
           [0020]    A further advantageous measure can consist in both the opening and closing of the drawers of the plate magazine, and the movement of the suction means, being able to take place fully automatically and under software control.  
           [0021]    According to another aspect of the invention, two pickup apparatuses according to the invention can load a drum exposer, it being possible for one apparatus to be used for the removal of the printing plate from the plate magazine and the subsequent transfer of the printing plate into an exposer and for the removal of an intermediate paper, and the other apparatus can be used for the removal of the printing plate on which an image has been set from the exposer and the transfer of said printing plate to a developing apparatus.  
           [0022]    The apparatus according to the invention can in principle be used irrespective of the type of plate magazine, the printing plate format and the type of the exposing device. It can be used for any of the printing processes described at the start.  
           [0023]    Further advantageous details of the invention are presented in the dependent claims, of which individual claims in turn have their own inventive contribution beyond the basic invention described here. 
       
    
    
     BRIEF INTRODUCTION OF THE DRAWINGS  
       [0024]    The invention will be explained in more detail using the exemplary embodiments illustrated schematically in the figures, in which:  
         [0025]    [0025]FIG. 1 shows a schematic illustration of the apparatus according to the invention,  
         [0026]    [0026]FIG. 2 shows a schematic illustration of an apparatus having two pick-up apparatuses according to the invention,  
         [0027]    [0027]FIG. 3 shows a perspective illustration of a pick-up apparatus according to the invention,  
         [0028]    [0028]FIG. 4 shows a cross section through a schematically illustrated, deformable sucker plate according to the present invention,  
         [0029]    [0029]FIG. 5 shows a cross section of a schematically illustrated, further embodiment of a deformable sucker plate according to the present invention and  
         [0030]    [0030]FIG. 6 shows a plan view of a deformable sucker plate according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    [0031]FIG. 1 shows a schematic illustration of the apparatus according to the invention. The apparatus comprises a plate magazine  1 , a pick-up apparatus  2  and an exposer  3 . The pick-up apparatus  2  according to the invention is depicted without covering and in detail in FIG. 3.  
         [0032]    The plate magazine  1  comprises a housing  4  having a plurality of drawers  5 ,  6 . The bottom plate of a drawer  5  is of convexly curved design. Printing plates  7 , illustrated hatched here, of an extremely wide range of types and of different formats can be placed in the manner of a stack in a drawer  5 . The use of plate magazines in which the printing plates are stored in planar fashion is likewise possible. In the present embodiment, the drawers  5  are equipped with plate stacks, including the intermediate papers located as a protection between the individual plates. In each case one plate format is stored in a drawer  5 , the side of the printing plate  7  on which an image is to be set being oriented upward. Up to 100 plates can be stacked per drawer  5 . In the process, the printing plates  7  match the curvature of the drawer  5 . The drawers  5  can be arranged to be extended by an electric motor. A detection device, not illustrated here, such as an optical sensor, for example, which is arranged in or on a drawer can detect the lack of one or more printing plates  7  in a drawer  5 .  
         [0033]    On the front side of the plate magazine  1  there is a trough  8  having a stack holder  9  to hold the intermediate papers removed from the plate stack.  
         [0034]    The pick-up apparatus  2  comprises a sucker plate  10  with suction heads  11 , which are fitted to arms  13  via webs  12 . By means of the pivoting movement of the arms  13 , a printing plate  7  can be removed from the drawer  5  and inserted into a drum exposer  3 . For the purpose of removal, the sucker plate  10  is lowered onto the printing plate  7  until the suction heads  11  of the sucker plate  10  can make contact with the printing plate  7 . The printing plate  7  can be held firmly on the sucker plate  10  by vacuum. In this case, picking up a specific plate type can be controlled by applying the vacuum selectively to specific suction heads  11 .  
         [0035]    Contact with the suction heads  11  is made with that side of the printing plate  7  on which an image is to be set. The suction heads  11  are put in place in such a way that their lateral movement on the printing plate surface is kept as small as possible. The suction heads  11  are therefore designed in such a way that injury to or destruction of this side is not possible. For example, the suction heads  11  are fabricated from resilient, soft plastic material.  
         [0036]    As FIG. 4 illustrates, in one embodiment of the apparatus the surface form of the sucker plate  10  can be changed. The shape change of the sucker plate  10  has the effect that suction heads  11  which are arranged closer to the sides of the sucker plate  10  can make contact with the printing plate  7 .  
         [0037]    A printing plate  7 , once picked up, is inserted into the semicircular drum exposer  3  by means of a pivoting movement of the arms  13 . Depending on the embodiment of the apparatus, the form of the sucker plates  10  with the printing plate  7  fixed to it can be matched to the size of the opening in the exposer  3 . Exact positioning of the printing plate  7  in the exposer  3 , not illustrated here, can be carried out either via a punched-out portion of the printing plate  7 , which can be inserted in exact register in pins arranged on the exposer  3 , or the position of the printing plate  7  can be registered digitally.  
         [0038]    While the laser of the exposer  3  is setting an image on the printing plate  7 , the pick-up apparatus  2  is able to remove an intermediate paper which is located between the individual plates  7  for the purpose of protecting stacked printing plates  7 . After a printing plate  7  has been removed from a plate stack, such an intermediate paper is at the top in a drawer  5 . The removal of this sheet is done with the same mechanism as the picking up of a printing plate  7 , that is to say via the sucker plate  10  and the vacuum system which can be applied. In order that an intermediate paper is not picked up together with a printing plate, different sizes of suction heads  11  are arranged on the sucker plate  10 . An intermediate paper is in this case picked up by means of a vacuum system which is applied to smaller suction heads. Once the intermediate paper has been picked up, the drawer  5  moves back into the plate magazine  1 . As a result of canceling the vacuum, the sheet falls into the stack container  9  in front of the plate magazine  1 .  
         [0039]    The presence or absence of a printing plate  7  or of an intermediate paper can be established by a sensor mechanism which is not illustrated here but which can be arranged on the sucker plate  10 . For example, an inductive detector can report whether metal or nonmetal is resting on the sucker plate  10 .  
         [0040]    After an image has been set on the printing plate  7  and the intermediate paper has been removed, the printing plate  7  is transferred onto the conveyor belts of the planar drawer  6  by means of the pick-up apparatus  2 . Via the conveyor belts, not illustrated here, of the drawer  6 , the plate is output to the output ramp  14  and can subsequently be fed to a developing device, not illustrated here. The output ramp  14  can also be arranged at the rear of the plate magazine.  
         [0041]    Both the construction of the exposer  3  and that of the developing device are known per se and therefore do not require any specific explanation in the present connection.  
         [0042]    For the further time optimization of the printing plate production, two of the pick-up apparatuses  2  according to the invention can be arranged on an exposer  3 . A schematic illustration of such an apparatus is shown in FIG. 2. In this case, one pick-up apparatus  2  loads the drum exposer  3  with printing plates  7  and removes the intermediate papers. This pick-up apparatus is therefore arranged to a plate magazine  1 . The other pick-up device  2  removes the printing plates  7  on which images have been set from the drum exposer  3  and passes these on via an output ramp  14  to a developer, not illustrated here.  
         [0043]    The pick-up apparatus  2  is illustrated schematically in FIG. 3. It comprises a frame  15  having a bottom part  16  and two side parts  17 . The side parts  17  are connected at their upper end to a rotatable, lower axle or shaft  19  driven by a motor  18 . The drive shaft of the motor  18  goes onto a pinion  20 . The pinion  20  is operatively connected via a first tooth belt  21  to a belt pulley  22 . The belt pulley  22  is firmly seated on the shaft  19  so as to rotate with it. The latter is connected at both ends to an arm  13  in each case. Here, the end of the arms  13  arranged at the shaft  19  is of curved or disk-like design. The arms  13  are synchronized via the shaft  19  and execute parallel pivoting movements. At the other end of the arms  13 , a sucker plate  10  is rotatably arranged via a mounting comprising an upper axle  23  and webs  12 . The sucker plate  10  is constructed in the form of a cylindrical segment. The upper axle  23  of the sucker plate  10  is arranged substantially parallel to the shaft  19 . The sucker plate  10  is arranged such that it can be pivoted about the upper axle  23 . When pivoted, the sucker plate  10  maintains the axial alignment, the sucker plate  10  being aligned on the basis of the force of gravity. The upper axle  23  is operatively connected to the shaft  19  via a further toothed belt  24 . As a result of the drive, the sucker plate  10  executes a controllable pivoting movement.  
         [0044]    The sucker plate  10  comprises at least two suction heads  11 . Illustrated here are a plurality of suction heads  11 , which are fitted in rows in or on the sucker plate  10 , parallel to the upper axle  23 . It is possible for suction heads  11  of different sizes to be arranged on the sucker plate  10 . Another arrangement of the suction heads  11  is likewise possible. The suction heads  11  are connected to a controllable vacuum system, not illustrated here. The sucker plate  10  is constructed such that it can be deformed in relation to its surface form. Various embodiments of the sucker plate  10  are illustrated in FIGS. 4 and 5.  
         [0045]    The drive motor  18  is assisted by a counterweight system  25 . For this purpose, a rod  26  having a weight  27  is in each case fixed to the curved end of the arms  13 . The weight  27  is guided on the frame  15  SO that it can execute only vertical movements. To this end, in each case a guide carriage is arranged on the weight  27  and a guide rail on the frame  15 , neither of which is shown here. When the arms  13  are lowered, the weight  27  is pulled upward by the pivoting movement, and downward when the arms  30  are lowered. The torque acting about the axles  19  therefore retards the pivoting movement during lowering, while during raising it assists the torque of the motor force.  
         [0046]    [0046]FIGS. 4 and 5 illustrate schematically the cross sections of various embodiments of a deformable sucker plate  10  having means for fixing to the upper axle  23 . The fixing means in FIG. 4 comprises two pneumatic cylinders  28  and a spindle  29  with a spindle drive  30 . Shown in FIG. 5 is a means for fixing the sucker plate  10  which, in each case, comprises two webs  12  and a connecting piece  31 , on which the webs  12 , the upper axle  23  and the arms  13 , the latter not illustrated, [lacuna].  
         [0047]    The webs  12  or the pneumatic cylinders  28  are rotatably fitted to the sucker plate  10  and to the connecting piece  31  or to the spindle drive  30 . By reducing the size of the angle between the webs  12  or the pneumatic cylinders  28 , the sucker plate  10  can be deformed in relation to its surface form.  
         [0048]    In this case, the angular change and therefore the form change of the sucker plate  10  can be controlled, as shown in FIG. 4, by a spindle drive  30 . As an alternative to this, the angular change can be induced on account of the force of gravity. If the sucker plate is guided upward from the drum exposer  3  or from a drawer  5 , as illustrated in FIG. 5, then the angle between the webs  12  changes on account of the force of gravity which acts on the sucker plate  10 .  
         [0049]    A further exemplary embodiment of a sucker plate  10  is shown in FIG. 6. At the sides, which are arranged parallel to the axis of the cylindrical segment, the sucker plate  10  has holes so that it can be deformed more easily in relation to its surface form at these sides than in the center.  
         [0050]    The invention also relates to a printing system and a method for automatic printing plate loading and unloading. FIG. 1 illustrates an apparatus with which the method according to the invention may be carried out. A drawer  5  belonging to the plate magazine  1 , containing a stack of printing plates  7  of a specific format, is extended horizontally by a drive. The pickup apparatus  2  is then pivoted in the direction of the plate magazine  1  to such an extent that the sucker plate  10  can make contact with the printing plate  7 . In an embodiment of the invention with a deformable sucker plate  10 , all the suction heads  11  make contact with the printing plate  7  as a result of the pivoting movement being continued. By applying vacuum to the suction heads  11 , the printing plate  7  is held on the sucker plate  10 . After a printing plate  7  has been picked up on the sucker plate  10 , the latter is positioned into the drum of the exposer  3  by means of the pivoting movement of the arms  13 , and is inserted into the drum as a result of the vacuum being switched off.  
         [0051]    While the exposer  3  is setting an image on the printing plate  7 , the intermediate paper is removed. For this purpose, the arms  13  pivot back from the exposer  3  toward the still-open drawer  5  of the plate magazine  1 . The sucker plate  10  is then lowered onto the intermediate paper which, following the removal of the printing plate  7 , is located at the top in the drawer  5 . The action of picking up the sheet is carried out via the same mechanism as that of a printing plate  7 . In order to prevent a printing plate being picked up together with an intermediate paper, the vacuum system is applied selectively to the smaller suction heads  11 . In addition, the presence of a printing plate  7  and/or of an intermediate paper on the sucker plate  10  can be detected via a sensor mechanism.  
         [0052]    After the intermediate paper has been picked up by the sucker plate  10 , the drawer  5  is moved back into the plate magazine  1  again. As a result of the vacuum being switched off, the intermediate paper falls down, into the stack container  9  of the trough  8 .  
         [0053]    The pick-up apparatus  2  then pivots back to the drum exposer  3  again and picks up the printing plate  7  on which an image has been set, by applying the vacuum. The arms  13  pivot back again toward the open drawer  6 . The drawer  6  is closed, and the printing plate  7  on which an image has been set is transferred to the output ramp  14  by the conveyor belts of the drawer  6 . Finally, the printing plate  7  is fed to the developing device arranged downstream by means of the output ramp  14 .  
         [0054]    In a further embodiment of the method according to the invention, two pick-up apparatuses  2  can be used for loading and unloading an exposer  3  and for removing an intermediate paper. The first pick-up apparatus  2  removes the printing plate  7 , loads the exposer  3  and removes the intermediate paper. All the method steps are carried out as described above. After an image has been set, the second pick-up apparatus  2  removes the printing plate  7  on which an image has been set and transfers it either directly to a developing device or to an interposed output ramp  14 . While the second pickup apparatus  2  is removing the printing plate  7 , the first pick-up apparatus  2  can already pick up a next printing plate  7  and keep it ready to load the exposer  3 .