Abstract:
A device for controlling a pneumatic consumer in a sheet-processing machine, for example a printing press or a diecutter, includes a rotary valve supplying a fluid, such as suction air, to the pneumatic consumer to be driven in a sinusoidal manner in accordance with a cycle of the sheet-processing machine. The rotary valve is drivable by an electric motor for increased flexibility. A rotary printing press or diecutter having the device is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2012 005 258.8, filed Mar. 15, 2012; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a device for controlling a pneumatic consumer in a sheet-processing machine, for example a suction bar for lifting sheets being fed to the sheet-processing machine, such as a sheet-fed rotary printing press or diecutter, after being aligned on a feed table. The invention also relates to a rotary printing press or diecutter having the device. 
         [0003]    U.S. Pat. No. 7,665,722 B2 discloses a pneumatic lifting device disposed transverse to a direction of sheet travel above a feed table and supplied with blown air. The blown air is provided by a rotary valve in accordance with the cycle of the sheet-processing machine and acts on a trailing edge of a sheet by using blowing/suction nozzles that are provided to lift a trailing edge. 
       SUMMARY OF THE INVENTION 
       [0004]    It is accordingly an object of the invention to provide a device for controlling a pneumatic consumer in a sheet-processing machine, in particular a rotary printing press or diecutter, and a rotary printing press or diecutter having the device, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which provide a pneumatically operating device to hold up a sheet as it is fed to a sheet-processing machine and supply pressure to the pneumatic consumer in a variably adjustable way and in accordance with an operating cycle of the sheet-processing machine. 
         [0005]    With the foregoing and other objects in view there is provided, in accordance with the invention, a device for controlling a pneumatic consumer in a sheet-processing machine. The device comprises a rotary valve communicating with the pneumatic consumer, and an individual drive configured to drive the rotary valve. The individual drive is an electric motor configured to be driven in accordance with a sinusoidal or non-uniform movement profile. 
         [0006]    With the objects of the invention in view, there is also provided a sheet-processing machine, comprising a feed table for guiding sheets in a sheet travel direction, front lays associated with the feed table, a pneumatic consumer being a suction bar disposed above the feed table and positioned within a distance upstream of the front lays in the sheet travel direction, and a device for controlling the pneumatic consumer. 
         [0007]    A particular advantage of the invention is that the rotary valve is actuatable by using an individual drive. Due to this feature, the actuation of a pneumatic consumer, such as a suction or blower bar, may be individually controlled during an operating cycle. The individual drive is advantageously controlled by a control computer of the sheet-processing machine and may be controlled based on characteristic curves as a function of properties of the machine and the material. 
         [0008]    In accordance with a preferred embodiment, the pneumatic consumer is a vacuum consumer, for example a suction bar that is disposed transversely to the direction of sheet travel above the feed table and acts on an upper side of a sheet within a shingled distance between a first sheet and a second sheet at a distance to provided front lays in order to act on the sheet by suction and to lift it as the sheet is being drawn off the feed table. 
         [0009]    This measure has a braking effect that acts to reduce a wave which the sheet describes as it enters the machine and to positively influence the formation of waves on the feed table. 
         [0010]    When the braking force is sufficient, the sheet that has been drawn off acts as a guide element for the second sheet that follows the first sheet in the shingled stream. 
         [0011]    Advantageously, the suction bar is vertically adjustable to be specifically adaptable to the printing material to be processed. 
         [0012]    In accordance with an advantageous embodiment, the suction bar has a multi-part construction, being formed of a crossbar and suction chambers disposed adjacent each other on the crossbar. 
         [0013]    If, for example, three suction chambers are used, the width of the central suction chamber approximately corresponds to the width of the smallest format to be processed. Due to this measure, the two outer suction chambers may be switched off to avoid leakage. 
         [0014]    The suction chambers are directly connected to the rotary valve by feed lines such as hoses. A chamber in which the feed lines are connected to the suction chambers is provided on the crossbar to receive the feed lines. 
         [0015]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0016]    Although the invention is illustrated and described herein as embodied in a device for controlling a pneumatic consumer in a sheet-processing machine, in particular a rotary printing press or diecutter, and a rotary printing press or diecutter having the device, 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. 
         [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 SEVERAL VIEWS OF THE DRAWING 
         [0018]      FIG. 1  is a diagrammatic, longitudinal-sectional view of a sheet-fed rotary printing press; 
           [0019]      FIG. 2  is an enlarged, longitudinal-sectional view of a suction bar disposed above a feed table; and 
           [0020]      FIG. 3  is a further enlarged, elevational view of the suction bar in the region of front lays. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a sheet-processing machine, for example a printing press  1  or a non-illustrated diecutter, which includes a feeder  2 , at least one printing unit  3 ,  4  and a delivery  6 . Sheets  7  are taken from a stack  8  of sheets and are fed to the printing units  3  and  4  either individually or in shingled formation over a feed table  9 . As is known in the art, each of the printing units  3 ,  4  includes a plate cylinder  11 ,  12 . Each of the plate cylinders  11 ,  12  has a device  13 ,  14  for mounting flexible printing plates. Each plate cylinder  11 ,  12  is furthermore assigned a device  16 ,  17  for changing printing plates in a semiautomatic or fully automated way. 
         [0022]    The stack  8  of sheets rests on a main stack plate  10  that is liftable in a controlled way. Sheets  7  are removed from the top of the sheet stack  8  by a so-called suction head  18  which, among other components, includes a number of suction elements to lift and drag the sheets  7  and thus to separate them. Furthermore, blowers are provided to aerate the upper layers of sheets  7 . The stack  8  can be lifted as required, which is activated by push buttons. A number of lateral and rear stops are provided to align the stack  8  of sheets  7 , in particular the uppermost sheets  7  in the stack  8 . 
         [0023]    At the end of the feed table  9 , a first sheet  7  that is being conveyed in the shingled stream is aligned against front and side lays  19 ,  21  seen in  FIGS. 2 and 3  before the sheet  7  is gripped by a pre-gripper  22  seen in  FIG. 1  and fed to the printing units  3 ,  4  of the machine  1  for processing sheets. 
         [0024]    A pulling gap  23  for the adjustable side lays  21  is disposed in the feed table  9  at a distance a from the front lays  19  and is perpendicular to the direction of sheet travel. A suction bar or consumer  24  is provided above the feed table, immediately upstream of the pulling gap  23 , as viewed in the direction of sheet travel (indicated by an arrow in  FIGS. 2 and 3 ). The suction bar  24  is disposed in such a way as to be perpendicular to the direction of sheet travel and is disposed within a shingle length s upstream of the front lays  19  to provide a distance z between the front lays  19  and suction openings  31 ,  32 ,  33  of the suction bar  24 . The suction bar  24  is formed of a crossbar  26  disposed in such a way as to be vertically adjustable and to pivot. A number of suction chambers, for example three suction chambers  27 ,  28 ,  29 , are disposed adjacent each other on the crossbar  26 . 
         [0025]    Each of the suction chambers  27 ,  28 ,  29  has a number of the suction openings  31 ,  32 ,  33  directed towards the upper side of the sheet  7 . The suction chambers  27 ,  28 ,  29  are connected to outlets  41 ,  42  of a rotary valve  44  by respective suction connections  34 ,  36 ,  37  and feed lines  38 ,  39 . The feed lines  38 ,  39  are received by a closed chamber  45  of the crossbar  26 . The feed line  38  supplies the central chamber  28  with suction air provided by the rotary valve  44 , whereas the feed lines  39  supply the outer suction chambers  27 ,  29  with suction air provided by the rotary valve  44 . The feed line  39  includes a switchover valve  46 , allowing the feed line  39  to be switched off. This measure prevents undesired air from being sucked in when sheets of small width are being processed. The width of the central suction chamber  28  approximately corresponds to the width of the smallest format F to be processed. 
         [0026]    The rotary valve  44  includes an inlet  49  connected to a vacuum source  48  and an individual drive  47 , for example an electric motor. A control computer  51  of the sheet-processing machine  1  drives the individual drive  47  in accordance with the operating cycle of the machine  1  and with a sinusoidal or non-uniform movement profile. The sinusoidal movement profile may be selected on the basis of stored characteristic curves  52 , which factor in different parameters of the sheet material to be processed such as size, thickness, surface properties, etc. 
         [0027]    The individual drive  47  of the rotary valve  44  allows variable and independent adjustment of the starting point and end point of the supply to the suction bar or consumer  24 . 
         [0028]    As soon as a first sheet  7  of the shingled stream has been aligned against the front and side lays  19 ,  21 , the first sheet  7  is gripped by the grippers of the pre-gripper  22  and drawn off the feed table  9 . As the sheet  7  is drawn off, it tends to form a wave on the feed table  9 . In order to reduce this waving effect, suction air is supplied to the suction bar  24 . Due to this measure, the sheet  7  is lifted up in the rear region of the first shingle and thus decelerated. 
         [0029]    As a result, the sheet may be fed to the sheet-processing machine  1  in a controlled way. The lifted sheet simultaneously acts as a guide element for a following second sheet, which is thus easier to align against the front lays  19 . 
         [0030]    A rotor  53  of the rotary valve  44  includes a track  54  that connects the inlet  49  to the outlets  38 ,  39 . During one revolution (cycle) of the sheet-processing machine  1 , the drive motor  47  likewise moves through precisely one revolution. The extrema of the movement profile are always at the center of the switch-on or switch-off phase, i.e. they are always at the same angular position relative to the rotary body although the angular position of the extrema relative to the machine varies, which means that the amplitude of the sinus wave is varied. 
         [0031]    When the value of the extremum in the switch-off phase is reduced, the switch-off phase is prolonged. As a consequence, the extremum in the switch-on phase increases and the length of the switch-on phase is reduced.