Abstract:
A rotary printing press includes at least one form cylinder, a transmitting gear via which the form cylinder is drivable together with at least another cylinder during a printing operation, and a device for setting an image on a printing form disposed on the form cylinder. A freewheeling clutch is disposed, during the printing operation, between the form cylinder and the gear for driving the form cylinder. A separate drive is provided for driving the form cylinder during an image setting operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the benefit of copending Provisional Application No. 60/316,845, filed Aug. 31, 2001.  
         BACKGROUND OF THE INVENTION  
         [0002]    Field of the Invention  
           [0003]    The invention relates to a rotary printing press including at least one integrated imaging or image-setting device for a printing form which, during imaging, is fastened to a form cylinder driven rotatably relative to the imaging device.  
           [0004]    A printing press of that general type is described in German Published, Non-Prosecuted Patent Application DE 197 23 147 A1, corresponding to U.S. Pat. No. 6,393,987. This printing press has two different drive systems. During the printing operation, all components of the printing press required for printing, which are mutually coupled via a gear train, are driven by a main drive. During the imaging or image setting operation, the form cylinder is driven separately by an auxiliary drive, the main drive being inactivated and the form cylinders being decoupled from the gear train with the aid of decoupling clutches. Deactivation of the main drive is necessary in order to prevent mechanical oscillations or vibrations and impacts, which would otherwise occur during the operation of the main drive, from influencing the imaging system made up of the imaging device and form cylinders. The mechanical vibrations and impacts would cause imaging and printing errors, respectively. During imaging, it is possible, besides driving the form cylinder with the aid of an auxiliary drive, also therewith to drive components which cause only small mechanical oscillations. After imaging, the form cylinder must be coupled into the main drive strand or loop in the correct or proper phase, for which special precautions must be taken. The in-phase reintegration of the form cylinder into the gear train can be monitored by measuring systems or performed by mechanical elements such as phase couplers.  
           [0005]    In order to prevent printing errors, German Published, Non-Prosecuted Patent Application DE 44 03 673 A1 teaches how to compensate for mechanical oscillations or vibrations of the printing press during imaging, by corrective controlling of the imaging heads in the circumferential direction.  
         SUMMARY OF THE INVENTION  
         [0006]    It is accordingly an object of the invention to provide a rotary printing press which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which low material and cost expenditures are required for driving a form cylinder in both printing and imaging operations performed therein.  
           [0007]    With the foregoing and other objects in view, there is provided, in accordance with the invention, a rotary printing press, comprising at least one form cylinder, a transmitting gear via which the form cylinder is drivable together with at least another cylinder during a printing operation, and a device for setting an image on a printing form disposed on the form cylinder. A freewheeling clutch is disposed, during the printing operation, between the form cylinder and the gear for driving the form cylinder. A separate drive is provided for driving the form cylinder during an image setting operation.  
           [0008]    In accordance with another feature of the invention, the freewheeling clutch further comprises clamping connecting pieces.  
           [0009]    In accordance with a further feature of the invention, the connecting pieces are actable via a clamping ring on a shaft of the form cylinder.  
           [0010]    In accordance with an added feature of the invention, the form cylinder is positionable by the separate drive at a defined angular position relative to the gear for driving the form cylinder during the printing operation, and is fixable in the defined angular position.  
           [0011]    In accordance with an additional feature of the invention, the rotary printing press further comprises a sensor provided for detecting the angular position between the form cylinder and the gear for driving the form cylinder during the printing operation.  
           [0012]    In accordance with a concomitant feature of the invention, the sensor provided for detecting the angular position is rotatable with the form cylinder and is directable to a marking on a side surface of the gear.  
           [0013]    The utilization of a freewheeling clutch, which acts upon one side, between the form cylinder and the gear from the gear transmission or train for driving, during the printing operation, offers the advantage that the form cylinder can be brought to imaging speed at any time, with the aid of the separate drive, without engaging and disengaging operations, while the gear train of the main drive loop is stopped. With the separate drive, the form cylinder can be moved into the proper or correct phase relative to the gear train or transmission electrically or mechanically, for example, by a locking journal pin.  
           [0014]    Other features which are considered as characteristic for the invention are set forth in the appended claims.  
           [0015]    Although the invention is illustrated and described herein as embodied in a rotary printing press, it is nevertheless not intended to be limited to the details shown.  
           [0016]    On the contrary, 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.  
           [0017]    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  
       [0018]    [0018]FIG. 1 is a diagrammatic, side-elevational view of a four-color rotary printing press;  
         [0019]    [0019]FIG. 2 is a cross-sectional, end view of a drive for a form cylinder of the printing press; and  
         [0020]    [0020]FIG. 3 is an end view of the drive shown in FIG. 2.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Referring now to the figures of the drawings in detail and, first, particularly to FIG. 1 thereof, there is seen a sheet-fed rotary printing press  1  having a feeder  2 , four printing units  3 ,  4 ,  5  and  6 , and a delivery  7 . Each printing unit  3  to  6  has a form cylinder  8 , a transfer cylinder  9 , an impression cylinder  10 , two transfer cylinders  11  and  12 , a multiplicity of ink transfer rollers  13  and dampening-solution transfer rollers  14 , as well as imaging mechanisms  15 . Transfer rollers  16  are disposed between the printing units  3  to  6 . Additional cylinders  17  and  18  serve for feeding sheets  19  to the first printing unit  3 . Deflection cylinders  20  and  21  are located in the delivery  7 , with chains  22  of a chain gripper system looped about the cylinders  20  and  21 . The cylinders and rollers in the printing units  3  to  6 , as well as all rotatably driven cylinders and drums, respectively, in the feeder  2  and the delivery  7 , respectively, are connected to one another by a gear transmission or train. An additional gear train  23  to  25  meshes with the gear of the transfer cylinder  12  of the second printing unit  4 . A pulley  26  of a belt drive  27  is located on the shaft of the gear  25 . A second pulley  28  is seated on the shaft of a main drive motor  29 . Moreover, auxiliary drive motors,  30  which are coupled directly with the form cylinders  8 , are located in the printing units  3  to  6 . The main drive motor  29  and the auxiliary drive motors  30  are connected to a control device  31  of the sheet-fed rotary printing press  1 . Besides additional actuators and sensors, the imaging mechanisms  15  are also in contact with the control device  31 .  
         [0022]    During the printing operation, sheets  19  are transported from the feeder  2  to the delivery  7  through the printing units  3  to  6 , the main drive motor  29  driving all of the components via the gear transmission or train. Harmonic and non-harmonic oscillations occur during the driving of the sheet-fed printing press  1  due to eccentricities, imbalance, and reciprocating assemblies, such as oscillation grippers or gripper mechanisms. The effects of the oscillations and impacts on the print quality are ameliorated by the high pressure exerted between the transfer cylinders  9  and the respective impression cylinders  10  during the printing operation.  
         [0023]    In order to avoid circumferential and axial oscillations during the imaging operation, the form cylinders  8  are driven by the auxiliary drive motors  30 , while driving by the sheet-fed rotary printing press  1  by the main drive motor  29  is disabled. Furthermore, the transfer cylinders  9  are disengaged from the form cylinders  8  and the printing cylinders  10  during the printing operation.  
         [0024]    According to the invention, the form cylinders  8  are driven via self-blocking freewheels between the respective form cylinder  8  and the drive gear of the respective transfer cylinder  9 , without additional controllable or switchable couplers.  
         [0025]    [0025]FIGS. 2 and 3 represent, with reference to the printing unit  3 , how the form cylinders  8  are driven during the imaging operation. FIG. 2 shows a side wall  32  of the sheet-fed rotary printing press  1 . The sidewall  32  is formed with openings containing bearings  33  and  34  for receiving shaft journals  35  and  36 , respectively, of the form cylinder  8  and the transfer cylinder  9 . A gear  37  of the gear train or transmission for driving the transfer cylinder  9  during printing is fixed on the shaft journal  36 . A gear  38  rotates in a bearing  39  mounted on the shaft journal  35 . The gear  38  is structurally united with an additional gear  40  for driving an inking and dampening unit. The gear  38  is continuously engaged with the gears  37 , and the gear  40  is continuously engaged with another gear  41 .  
         [0026]    The gear  38  is formed with a bored portion wherein a self-blocking freewheel or slipping clutch is located, which is formed of a clamping ring  42  at the surface of the shaft journal  35  and of four connecting pieces  43  which are evenly distributed in the circumferential direction of the bored portion of the gear  38 . A marking  44  which can be detected by a sensor  45  is applied to the face of the gear  38 . The sensor  45  is seated on a holder  46 , which is fixed to the shaft journal  35 . For driving the form cylinder  8  during the imaging operation, the axle  47  of the auxiliary drive motor  30  is coupled directly with the shaft journal  35 . The auxiliary drive motor  30  and the sensor  45  are connected to the control device  31  by way of lines  48  and  49 , respectively.  
         [0027]    During the printing operation, the gear  37  is driven by the main drive motor  29 . The gears  38 ,  40  and  41  which are connected to the gear  37  rotate in the direction indicated by the arrow  50 . When rotation is in the direction  50 , the connecting pieces  43  are clamped between the bored portion in the gear  38  and the clamping ring  42 . The clamping ring  42  is pressed against the shaft journal  35  by radial forces, so that the shaft journal is entrained simultaneously and in synchronism with the rotation of the transfer cylinder  9 .  
         [0028]    During the imaging operation, the main drive motor  29  is stopped, due to which the gears  37 ,  38 ,  40  and  41  are stopped or at standstill. The auxiliary drive motor  30  drives the form cylinder  8  in the direction represented by the arrow  51 . The clamping of the connecting pieces  43  and, therewith, the pressing of the clamping ring  42  against the shaft journal  35  are discontinued. The imaging of the printing form located on the form cylinder  8  is accomplished without the mechanical disturbances which would occur during the printing operation due to the driven elements. The auxiliary drive motor  30  allows for imaging at a higher form-cylinder speed than during the printing operation. With a rotary transducer which is coupled with the form cylinder  8 , it is possible to determine instantaneous speed of rotation and cylinder position. These signals can be processed in the control device  31 , in order to control the imaging. It is not necessary to shut down the main drive motor  29  if the elements which are driven by the gear transmission or train during the printing operation operate within a speed range such as a crawl speed, for example, wherein, it is quite certain that disturbing oscillations or impacts will not occur. In this way, due to the aforementioned elements, the processes preparatory to the printing process, such as washing and exchanging printing forms, for example, can be performed.  
         [0029]    After the imaging or image setting of the printing form on the form cylinder  8 , the form cylinder  8  and the transfer cylinder  9  must have the correct phase relative to one another. To this end, the form cylinder  8  and, therewith, the sensor  45  must be brought or moved, by the auxiliary drive motor  30 , into an angular position wherein the sensor  45  is situated opposite the marking  44 . The signal of the sensor  45  is evaluated in the control device  31 , in order to derive control signals for the auxiliary drive motor  30 . In this position, the gear  38  is fixed on the shaft journal  35 , in that the precise blocking point of the freewheel is controlled by electronics. Alternatively, the gear  38  can be oriented and fixed in the correct or proper phase relative to the form cylinder  8  by mechanical elements, such as stops and locking journal pins.