Abstract:
The invention relates to a suction roll for the transport of aligned sheets. Said roll may be intermittently driven for the transport of a sheet, until said sheet is taken by a subsequent transport system.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a suction roller. The suction roller is used for conveying sheets in a sheet processing machine.  
         BACKGROUND OF THE INVENTION  
         [0002]    A sheet feeding device is known from DE 33 11 196 C2, in which an alignment cylinder has a suction drawing strip in the vicinity of its front lay marks. The suction drawing strip is used for aligning the lateral edges of sheets. In the course of the transfer of the sheets to a following drum, the start of each sheet is held by grippers, and the front lay marks border the sheet.  
           [0003]    DE 23 30 484 C3 describes a suction roller with individual suction rings.  
           [0004]    EP 0 846 638 A2 describes a device for mounting a sheet on a suction drum with detents.  
         SUMMARY OF THE INVENTION  
         [0005]    The object of the present invention is directed to creating a suction roller.  
           [0006]    In accordance with the present invention, this object is attained by providing a suction roller for conveying sheets in a sheet processing machine. The suction roller can be driven at varying circumferential speeds. A portion of its exterior surface projects through a slit provided in a guide element. The suction roller has front lay marks on its circumference and has its own drive motor.  
           [0007]    The advantages which can be achieved by the present invention reside, in particular, in that printed sheets can be passed, with their front edges aligned, to a further processing station by use of a single roller. In this case, every sheet is bent only slightly, during its transport to the further processing station by use of a suction roller. During the transfer to the next conveying means, the start of the sheet is free of holding elements or detents.  
           [0008]    Furthermore, a great amount of flexibility of the chain of movements of the suction roller is possible because of the suction roller having its own electric motor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    A preferred embodiment of the present invention is represented in the drawings and will be described in greater detail in what follows. Shown are in:  
         [0010]    [0010]FIG. 1, a view from above on the right end of a suction roller with a drive mechanism in accordance with the present invention; and in  
         [0011]    [0011]FIG. 2, a section taken along line II-II in FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    A suction roller  01  consists, for example, of a hollow cylinder  02  with bores  03  extending in the radial direction, as shown in FIG. 1. The hollow cylinder  02  is rotatably seated on a support tube  06 , which has a first end that is fixed in lateral frames and whose exterior is provided with white metal  04 . The radially extending bores  03  extend approximately over half, i.e. 150° to 210°, in particular 180° to 210°, of the outer surface, or the circumferential line or surface  07  of the suction roller  01 .  
         [0013]    The support tube  06 , as well as the white metal  04 , are provided with air supply slits  08  which terminate on their upper, i.e. close to the sheet, side, so that suction air supplied through the first end of the support tube  06 , seated fixed in the lateral frames, can reach the respective bores  03  of the hollow cylinder  02 . Regarding the suction effect, there exists an effective portion of the exterior surface  07  of the suction roller  01 , approximately 20 to 30 degrees of arc.  
         [0014]    On its second end, the support tube  06  is provided with a journal  09 , on which an engagement sleeve  15 , seated on a roller, is rotatably arranged and which engagement sleeve  15  is connected, fixed against relative rotation, with the rotatable hollow cylinder  02  by use of a crimped engagement arm  10  oriented in the radial direction. The engagement sleeve  15  is seated by rolling bearings  18 ,  19  of the journal  09 , or on a lateral frame  17  in rolling bearings  18 ,  19 . A drive motor  12 , for example a step motor, or an angular position-controlled electric motor; i.e. an individual drive, for generating an uneven or variable speed of the hollow cylinder  02  in the circumferential direction, is flanged to the side of the lateral frame  17  facing away from the roller and is connected with the engagement sleeve  15 .  
         [0015]    Viewed in the clockwise direction of rotation A of the suction roller  1 , as seen in FIG. 2, at the start of its cut-in bores  03 , the hollow cylinder  02  has front lay marks  13  which are arranged next to each other in the direction toward the suction roller  01 , and which protrude by an amount b, for example three to five millimeters, past the circumferential surface or line  07  of the hollow cylinder.  
         [0016]    In accordance with a preferred embodiment, the hollow cylinder  02  has suction rings  14 ,  16 , which are provided with bores  03  and which are located, spaced apart in the axial direction, next to each other on the hollow cylinder  02 . The suction rings  14 ,  16  are spaced apart by respective annular grooves  20  cut into the hollow cylinder  02 . It is also possible to provide additional suction rings, which are not specifically represented. Each suction ring  14 ,  16  also has bores  03  extending over half the circumferential surface or line  07 , which bores  03  also penetrate the hollow cylinder  02 .  
         [0017]    Viewed in a conveying direction of a sheet, the suction roller  01  is arranged at the discharge end of a feed table, for example, in such a way that its exterior surface or circumferential line  07  is located slightly above the table top.  
         [0018]    If—as represented—the suction roller  01  has suction rings  14 ,  16 , a separate slit is provided in the feeding table for each of the suction rings  14 ,  16 .  
         [0019]    Viewed in the conveying direction and after the feeding table, a further processing station, for example a conveying roller or a printing cylinder, is arranged, which can take over the sheet, for example by means of gripper systems.  
         [0020]    The mode of functioning of the suction roller  01  of the present invention is as follows:  
         [0021]    A sheet, whose lateral edges have already been aligned, is conveyed by generally known means in the conveying direction on the feeding table up to the front lay marks  13  of the idle suction roller  01  whose circumferential speed now equals zero. The hollow cylinder  02  is accelerated from zero to 0.7 m/s, for example, by operation of the drive, which can be rotated at different numbers of rotation and which includes the motor  12 , the engagement sleeve  15  and the engagement arm  10 , so that on a straight acceleration path and a subsequent synchronized path, the sheet attains the circumferential speed of the printing cylinder of, for example 0.6 m/s, and is held fast on the printing cylinder by the provision of a gripper system at a preset gripper closing point. In the course of conveying a sheet, respectively at least one or several bores  03  of the rotating suction rings  14 ,  16  are connected with the air supply slit  08  of the support tube  06 , so that a movement of the sheet in the conveying direction can take place. Thus, in the course of one rotation of the suction roller  01 , the circumferential speed swings between zero and 1.3 to 2.5 times the circumferential speed of the printing cylinder.  
         [0022]    The conveying speed of the sheet can be slightly, for example 10%, greater than the conveying speed of a following conveying means, for example a cylinder. This following conveying means also can have front lay marks, so that an alignment takes place again.  
         [0023]    While a preferred embodiment of a suction roller in accordance with the present invention has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that a number of changes, for example in the printing press used with the suction roller, the type of sheet being printed and the like could be made without departing from the true spirit and scope of the present invention which is to be limited only by the following claims.