Abstract:
A method for laterally aligning a sheet in a sheet-processing machine, the sheet being retained by sheet grippers which are displaced axially on a common carriage with respect to an alignment cylinder, includes fixing the carriage when it reaches a predetermined desired position; and device for performing the method.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method and a device for laterally aligning a sheet, more particularly, by an axially displaceable sheet gripper device on a cylinder or a drum of a sheet-processing machine, having a control roller and a cam disk cooperating with the control roller at an end face. 
     The published German Patent Document DE 36 44 431 A1 discloses a cam disk which is mounted on a side frame so that it can pivot in the axial direction of a cylinder carrying sheet grippers. An adjusting movement is produced by an adjusting motor and adjusting gearing connected downstream of the latter. The cam disk is respectively pivoted only to the extent which is intended to correspond to the axial displacement of a carriage. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a method and a device for an axial adjusting movement of a sheet gripper device, wherein a cam disk is arranged in a stationary manner, which provides a considerable improvement over the state of the art. 
     With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for laterally aligning a sheet in a sheet-processing machine, the sheet being retained by sheet grippers which are displaced axially on a common carriage with respect to an alignment cylinder, which comprises fixing the carriage when it reaches a predetermined desired position. 
     In accordance with another mode, the method of the invention includes axially displacing the carriage and the sheet retained thereon with respect to the alignment cylinder, from a given position, until a sensor identifying a desired position emits a signal to fix the carriage, and then fixing the carriage. 
     In accordance with a further aspect of the invention, there is provided a device for laterally aligning a sheet by an axially displaceable sheet gripper device on a cylinder or a drum of a sheet-processing machine, having a control roller and a cam disk cooperating with the control roller at an end face, comprising a carriage to which the sheet gripper device is fastened, and a braking system by which the carriage is fixable with respect to the alignment cylinder. 
     In accordance with another feature of the invention, the braking system includes a strip and two activatable brake blocks for clamping the strip. 
     In accordance with a further feature of the invention, the carriage is axially displaceably mounted in a cylinder gap formed in the sheet alignment cylinder. 
     In accordance with an added feature of the invention, the cam disk is mounted fixedly on the frame and has a control contour within an effective range of a control roller. 
     In accordance with an additional feature of the invention, the aligning device includes a sheet lateral position detection system connected to the braking system. 
     In accordance with yet another feature of the invention, the device includes a first spring element for producing at least one of a restoring movement and a deflecting movement of the carriage. 
     In accordance with a concomitant feature of the invention, the control roller is displaceable with respect to the carriage, the control roller being displaceable counter to a force of a second spring element. 
     The advantage of the invention resides, in particular, in the fact that a sheet to be transported can be aligned laterally even at high processing speeds. In an advantageous manner, braking of the lateral movement of the gripper carriage can be performed significantly faster than driving to a desired position by an adjusting motor. Sensors which are provided for the detection of the sheet side positions are integrated in the alignment cylinder. By this measure, the actual lateral position (nominal value) of the sheet in relation to the cylinder is measured. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as a method and device for laterally aligning a sheet, 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. 
     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, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic top plan view of a sheet alignment cylinder incorporating the device according to the invention; 
     FIG. 2 is an enlarged diagrammatic end view of the sheet alignment cylinder of FIG. 1; and 
     FIG. 3 is an enlarged diagrammatic top plan view of a control contour of a cam disk shown at the right-hand side of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and, first, particularly to FIGS. 1 and 2 thereof, there is shown therein a sheet alignment cylinder  1  of a sheet-fed rotary printing machine arranged between a feeder table  2  and an impression cylinder  3 . The sheet alignment cylinder  1  has an axially parallel cylinder gap or channel  4  formed therein, in which a carriage  6  is axially movably mounted. The carriage  6  carries a number of sheet gripper devices  7 , which are arranged alongside one another and spaced apart from one another and are controlled in a conventional manner. Each sheet gripper has a gripper finger  8 , a gripper pad  9  cooperating with the latter and a sheet leading edge alignment lay  11  (front lay). A cam disk  12  having a control contour  13  formed on the end face thereof is arranged in a fixed manner, but able to be rotated in order to set control times. The cam disk  12  is effectively connected, by the control contour  13  thereof, to a control roller  14 . The control roller  14  is rotatably mounted on a rod  16  which is axially displaceable with respect to the carriage  6 . A compression spring  17  arranged coaxially around the rod  16  is supported on an end face  18  of the carriage  6  and on a shoulder  19  of the rod  16  and thus ensures that the control roller  14  introduces an axial adjusting movement of the carriage  6  up to a force corresponding to the force of the compression spring  17 . On an end face  21  of the carriage  6  which faces away from the cam disk  12 , there is arranged a second compression spring  22 , which is dimensioned to be smaller than the compression spring  17  and applies a restoring force. This spring  22  is supported at one end thereof on the end face  21  and at the other end thereof on an inner wall of the sheet alignment cylinder  1 . 
     On a side facing away from the sheet gripper device  7 , the carriage  6  has a strip  23  with two parallel side walls  24  and  26  (FIG.  2 ). During the axial deflection of the carriage  6 , the strip moves between two brake blocks  27  and  28  of a braking system  29  fixed to the cylinder. An operating cylinder  31  of the braking system  29  can be activated hydraulically or pneumatically, and preferably magnetically. When activated, the operating cylinder actuates the brake blocks  27  and  28  in such a manner that the latter clamp the projection  23  firmly, so that the carriage  6  is fixed. 
     A sheet detection system  34  of conventional construction for the purpose of detecting the position of the sheet side edges is arranged parallel to the cylinder gap or channel  4 , as viewed in the sheet transport direction, in front of the cylinder gap or channel  4  and within the periphery of the alignment cylinder  1 . The system includes two sensors  36  and  37 . In this case, the sensor  36  is provided for detecting the left-hand and the sensor  37  for detecting the right-hand sheet side edges. In order to set the format, the sensors  36  and  37  are axially adjustably mounted on a spindle  38  having contrarotating threads. The sensors  36  and  37  are connected to the braking system  29  via a computing/control unit of conventional construction. 
     As shown in FIG. 3, the control contour  13  of the cam disk  12  has a control cam  41  having a resting region and a control valley  42  having a resting region. A control region having a rise  43  or a fall  44  is, respectively, arranged between the control cams  41  and  42 . The running direction of the control roller  14  on the control contour  13  corresponds to the arrow in FIG.  3 . 
     A sheet  47  which is conveyed on the feeder table  2  supported by a cyclically operated roller  46  is conveyed with the leading edge thereof directly into the sheet gripper device  7  of the sheet alignment cylinder  1  and is aligned on the front lays  11 . The control roller  14  is located in the resting region of the control valley  42  during this process. After the grippers have been closed, the control roller  14  passes onto the rise of the control region  43  and displaces the carriage  6 , together with the sheet  47 , axially to the right-hand side with respect to the alignment cylinder  1  and counter to the force of the compression spring  22 , until the sheet lateral edge reaches the sensor  37 . A pulse conducted from the sensor  37  to the computing/control unit activates the braking system  29  and fixes the carriage  6  in the desired axial position. The sheet  47  which has been aligned in this manner is transferred to the downstream impression cylinder  3 . If, at the instant of the fixing of the carriage  6 , the control roller  14  is still on the rise of the control region  43 , the further overstroke is absorbed by displacing the rod  16  with respect to the alignment cylinder  1  counter to the force of the compression spring  17 . The release of the braking system  29  occurs following the sheet transfer, preferably at the instant when the control roller  14  reaches the fall region in the vicinity of the control region  44 , which corresponds to the rise region at which the carriage  6  was fixed. 
     If a sheet  47  is intended to be pulled to the left-hand side for its alignment, so that the sensor  36  is used for determining the lateral position of the sheet  47 , the cam disk  12  can be pivoted through 180 degrees and then fixed once more. 
     The alignment process is performed inversely proportionally to that described previously, the sheet  47  being taken over from the feeder table  2  when the control roller  14  is located in the resting region of the control cam  41 .