Patent Publication Number: US-7590378-B2

Title: Device and method for guiding a continuous web by means of a pivotable apparatus

Description:
BACKGROUND 
   The present preferred embodiment relates to devices for guiding an endless web as used for example in a printer or copier. The present preferred embodiment also relates to methods for guiding an endless web. 
   In the guiding of a paper web through a printer, non-uniform mechanical properties of the web or a basic setting of the various guide rolls that is not precisely parallel can result in a lateral shifting of the paper web, and can cause the formation of waves in some areas and/or sagging at one side of the web, even if the front edge is running in a stable fashion. At points of deflection with counter-pressure or back pressure rolls, as are, for example, required for transport, such waves can be pressed to form folds. In addition, sagging at one side of the web, for example in the area of a fixing station that operates in contactless fashion, is disturbing, because the sagging web segment can come into contact with mechanical parts, so that the toner images are smudged, or the sagging segment is exposed to an excessively high energy load. 
   From U.S. Pat. No. 5,021,673, a device is known for guiding a paper web in which for the guiding of the web, rolls are situated at both lateral edges that exert pressure on the web with different forces. In this way, a lateral shifting of the web can be corrected. 
   In U.S. Pat. No. 5,323,944, a device for controlling the lateral position of a web is described with which the web is guided between a pressure roll and a counter-pressure roll. The pressure roll can be pivoted, and the force exerted on the counter-pressure roll along its shaft or axle can be varied in order to shift the side edges of the web. The current position of the side edges of the web is acquired using optoelectronic sensors. 
   U.S. Pat. No. 6,104,907 describes a device for guiding a paper web in a printer. In order to avoid vibrations and variations in speed, the web is guided around rolls and is clamped by them, which also counteracts a lateral shifting of the web. For example, in order to avoid lateral shifting, a guide roll is used having pins that engage in corresponding holes in the web. In another variation, the force that a roll exerts along its axis on the web is varied. In another variation, the web is guided between pairs of upper and lower rolls. These upper and lower rolls wrap and clamp the web with an enlarged wrap angle, thus preventing a variation in speed of the web. 
   From documents DE 689 07 466 T2, DE-OS 14 24 318, DE 195 20 637, and DE 199 60 649 A1, web guiding devices are known for guiding an endless web. In addition, pivotable draw-off devices for paper webs are known from DE 199 53 353 A1 and DE 44 35 077 A1. 
   SUMMARY 
   An object is to indicate devices and methods that enable a precise guiding of an endless web, and with which a sagging at one side of the web is avoided. 
   In a method or device for guiding an endless web, the endless web is guided via a first positionable roll to an additional positionable roll with a predetermined angle of wrap on each roll, shafts of the rolls lying parallel to one another in a plane and being held by a frame. The web is fed to and led away from the positionable rolls via a respective first stationary roll and a respective additional stationary roll. The frame is pivoted relative to the stationary rolls about a first axis of rotation substantially perpendicular to the plane in order to modify a position of an edge of the web in a direction of the positionable roll shafts. The frame is pivoted relative to the stationary rolls about a second axis of rotation one component of which runs parallel to a movement direction of the web between the positionable rolls. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are respectively side and plan views as schematic representations of the paper transport device in a high-performance printer, having a rotating frame that can be moved in two axes of rotation and a pivotable draw-off device; 
       FIG. 2  shows the design of the rotating frame; 
       FIG. 3  shows an inlet roll with web tension measurement; 
       FIG. 4  shows a schematic representation of the controlling of the web transport device according to a first variation; 
       FIG. 5  shows a second variation of a control system; 
       FIG. 6  schematically shows a control system according to a third variation; 
       FIG. 7  shows the design of an electrographic printer in which a web guiding system is realized; 
       FIG. 8  shows a schematic arrangement having a first sensor for acquiring the side edge of the web; 
       FIG. 9  shows a block diagram of the control circuit for controlling the position of the side edges; 
       FIG. 10  shows a schematic design with an additional second sensor in the feed-in area of the web; 
       FIG. 11  shows a block diagram of the position control system having two sensors; 
       FIG. 12  shows the design with three sensors; 
       FIG. 13  shows the block diagram of the position control system in which the signals of the three sensors are taken into account; 
       FIG. 14  shows a rotating frame having a single driven roll and counter-pressure rolls; 
       FIG. 15  shows a schematic view according to  FIG. 1  in cross-section; 
       FIG. 16  shows an example with a small wrap angle; 
       FIG. 17  shows examples in which the axis of rotation of the frame stands perpendicular to the drawn-off web; 
       FIG. 18  shows examples in which the axis of rotation runs parallel to the direction of movement of the drawn-off web; 
       FIG. 19  shows an example of a web guiding device; 
       FIG. 20  shows an example of a web with attached adhesive labels; 
       FIG. 21  shows the roll characteristic of the counter-roll having a soft lining or facing; 
       FIG. 22  shows a roll having labels that are glued to the side of the driven roll; 
       FIG. 23  shows an arrangement in which the counter-roll device is pivoted away; and 
       FIG. 24  shows a web guiding device having a stationary driven roll and a multiplicity of counter-rolls that can be rotated. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and/or method, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates. 
   According to this solution, the endless web is guided via two rolls with a predetermined wrap angle for each roll. The shafts of the rolls are situated parallel to one another in a plane and are held by a frame. The frame can be pivoted about a first axis of rotation essentially perpendicular to this plane in order to modify the position of the edge of the web in the direction of the roll shafts. In this way, a lateral shifting of the web can be corrected. In addition, the frame can be pivoted in a second axis of rotation having one directional component in three-dimensional space that runs parallel to the direction of movement of the web between the two rolls. In this way, the web tension can be modified on one side of the web, so that a sagging of the web at one side is avoided. The second axis of rotation can also run exclusively parallel to the direction of movement of the web. The additional components in three-dimensional space then relate to the zero direction of movement. However, constructive advantages result from an oblique positioning of the axis of rotation in relation to the direction of movement, where only one component need run parallel to the cited direction of movement. 
   According to a further aspect of the preferred embodiment, a method is indicated for guiding an endless web. 
     FIGS. 1A ,  1 B schematically shows the transport of an endless paper web  10  through a high-performance printer. In the upper half  FIG. 1A , a side view is schematically shown, and in the lower half of the Figure a top view is shown. The web transport through the printer takes place in three zones Z 1 , Z 2 , and Z 3 . In zone Z 1 , paper web  10  is conveyed through a pull-back device  12  that contains a roll  14  and a counter-pressure roll  16 . Pull-back device  12  is used to give paper web  10  a predetermined tension in the direction of transport. Paper web  10  is subsequently deflected at a deflector roll  18  and is supplied to an inlet roll  20  that is positioned before a rotating frame  22 , as seen in the direction of transport. Inlet roll  20  comprises two sensors S 1 , S 2  for measuring the tensile force on the web, as is explained in more detail below. Rotating frame  22  contains two positionable rolls  24 ,  26  whose shafts are parallel to one another and are held by a frame  28  shown in broken lines. Frame  28  can be pivoted about an axis of rotation  30  in the direction of arrow  32 . The web transport system is monitored by two sensors S 3 , S 4  that monitor paper web  10  from above in the area between positionable rolls  24 ,  26 . Alternatively, the web  10  can also be monitored from below using corresponding sensors. 
   In the output area of rotating frame  22  an edge sensor  34  is situated fixedly on the device that determines the actual position of the side edge of paper web  10 . Dependent on the actual position and the deviation of the edge from a target position, rotating frame  22  is pivoted on a framework about axis  30 , so that the side edge is controlled to a predetermined target position. 
   As seen in the direction of transport of paper web  10  after rotating frame  22  in zone Z 2 , there is situated a stabilizing roll  36  that acts to compensate the tension in paper web  10 . Stabilizing roll  36  can be slightly flexible or yielding radially, thus effecting a passive compensation for web  10 . In addition, a deflecting roll  38  and a drive roll  40  are situated in this zone Z 2 . Drive roll  40  exerts a tensile force on paper web  10  and transports web  10  forwards against the resistance of a braking device  13 , e.g. a vacuum brake. Drive roll  40  determines the speed with which paper web  10  is transported forwards. Alternatively, pullback device  12  can be used as a permanent brake. 
   In zone Z 3 , paper web  10  is printed on one or both sides at transfer rolls  42 ,  44 . Web  10  subsequently passes through a fixing station  46  in which the toner images applied to web  10  are fixed, for example by infrared fixing. In the area of fixing station  46  there are situated sensors S 5 , S 6  that monitor paper web  10 . At the end of zone Z 3  there is situated a draw-off device  48  having rolls  49 ,  50  that draw off web  10  with a predetermined tensile force. 
   In the case of limited infrared fixing, paper web  10  must not come into contact with mechanical parts between draw-off device  48  and transfer rolls  42 ,  44 , in order to avoid smudging of the toner image. Sagging at one side of the paper web must therefore be stopped. 
   Draw-off device  48  can be pivoted in the direction of double arrow  56  about an axis of rotation  54  that passes through rotation point  52 . In this way, the tension can be varied along the two side edges  11 ,  13  of paper web  10 , in order to reduce or to prevent a sagging at one side of paper web  10 . 
   Rotating frame  22  can additionally be pivoted in a second axis of rotation  58  in the direction of arrow  60 . Axis  58  runs essentially parallel to or identical to the direction of movement of paper web  10  between the two positionable rolls  24 ,  26 . In this way, the tension on one side of paper web  10  can be increased or decreased, thus avoiding a sagging comprising movement in a direction perpendicular to a plane of the web at one side of paper web  10 . 
   In the lower part  FIG. 1B , a top view of the transport of paper web  10  through the high-performance printer is shown. In a variation, the transport of paper web  10  takes place in such a way that one side edge has a fixed target position independent of the width of paper web  10 . In the present example, this has been determined to be the left side edge  11 , seen in the direction of transport. This side edge  11  agrees with second axis of rotation  58 . In the present example according to  FIG. 1 , a pivoting of the entire rotating frame  22  takes place about axis of rotation  58  by pivoting frame  28  about a bearing  62  that is situated approximately below the prolongation of axis of rotation  58 . For this purpose, a screw-nut combination  64  is situated on the opposite side of bearing  62 , with which frame  28  can be pivoted about axis of rotation  58 . It is to be noted that other determinations of side edge  11  in relation to axis of rotation  58  can be made. Other devices can also be used for the pivoting that operate electrically, hydraulically, or pneumatically. The depicted screw-nut combination  64  merely indicates a particularly simple device that can be actuated by hand. 
   Sensors S 1 , S 2  are preferably formed as force sensors, and measure the forces exerted by paper web  10  on the shaft of inlet roll  20 . If the force on one side of web  10  is reduced, the typical result is a sagging of web  10  at this side. A sagging at one side of this sort can be compensated by adjusting screw-nut combination  64 . 
   In the one-sided determination of side edge  11  of web  10  shown in  FIGS. 1A ,  1 B, web  10  is not situated centrically in relation to inlet roll  20 . This asymmetry also has the result that, due to different lever arms, asymmetrical forces occur in sensors S 1 , S 2  along the shaft of inlet roll  20 . Here, the target values for a correction that may be required are likewise asymmetrical. They are determined for example using computer programs or by measurements, and form the basis for corrective data. 
   Sensors S 3 , S 4  and S 5 , S 6  monitor the edge areas of web  10  having side edges  11 ,  13 , and can recognize a sagging at one side. For example, video cameras can be used as sensors. Another possibility is to acquire the web tension in the area of side edges  11 ,  13 , for example using one or more force sensors. Another possibility is to determine the sagging of the respective side edge  11 ,  13  using path sensors that operate optically, inductively, and/or capacitively. 
     FIG. 2  schematically shows rotating frame  22  having two rolls  24 ,  26 , whose shafts  66  run parallel to one another and are held by frame  28 . Through a rotation in the direction of arrow  32  about axis  30  in relation to stationary rolls W 1 , W 2  (inlet roll  20  and stabilizing roll  36  in  FIGS. 1A ,  1 B), the position of side edges  11 ,  13  of web  10  can be modified in the direction of roll shafts  66 . Through a pivoting in the direction of arrow  60  about axis  58 , the tension within paper web  10  can be modified at the side of an edge  11 ,  13  of the web. In the example according to  FIG. 2 , axis of rotation  58  is situated in the center of web  10 . However, it can also be situated at the edge of web  10 , as in the example according to  FIGS. 1A ,  1 B, or even outside paper web  10 . 
     FIG. 3  shows an example of the measurement of the tension of paper web  10  using draw-in roll  20  and sensors S 1  and S 2 , which are realized as bending beams with expansion measurement strips for force measurement. Inlet roll  20  is held at both ends in receptacles  68 . These receptacles  68  are connected fixedly with the printer housing (not shown) by means of mounts (bending beams)  70 ,  72 . The expansion measurement strips of sensors S 1 , S 2  measure the bending of these mounts  70 ,  72 , and thus the forces F 1 , F 2  that occur at each side of draw-in roll  20 , which, given an asymmetrical situation of paper web  10  and draw-in rolls  20 , are approximately proportional to the tension in each side edge  11 ,  13  of paper web  10 . Sensors S 1 , S 2  provide electrical signals via lines  74 ,  76 . If the web tension in the area of a side edge  11 ,  13  of web  10  is less than the target value, the respective force F 1 , F 2  is also less than the target value, so that a sagging of this side edge  11 ,  13  of web  10  can be inferred. Given an asymmetrical situation of paper web  10  and draw-in roll  20 , the lever arms for sensors S 1 , S 2  along the shaft of inlet roll  20  are to be taken into account, i.e., the target forces are likewise asymmetrical and the forces are to be corrected accordingly. 
   The depicted measurement of the tension of paper web  10  at draw-in roll  20  can of course also be applied at other rolls in the web transport through the printer, so that using a similar system it is possible to determine sagging at one side of web  10  at almost any location within the printer. 
     FIGS. 4 ,  5  and  6  show three variations for controlling or regulating the web tension in the printer. In the variation according to  FIG. 4 , a controlling or regulating of the web tension takes place using sensors S 3 , S 4  on rotating frame  22  as well as sensors S 5 , S 6  in the area of fixing station  46 . The signals of sensors S 3 , S 4  and S 5 , S 6  are provided to a control unit  80  that processes them preferably by means of software, in a control or regulation algorithm. This control unit  80  then produces control signals  82 ,  84  for controlling corresponding drives for rotating frame  22  and for draw-off device  48 . The control algorithm processes predetermined target values  86 ; control unit  80  also produces items of information concerning operating states that are shown on display  88 . 
   If it has been determined with the aid of sensors S 3 , S 4  that in the area of rotating frame  22  web  10  is sagging along a side edge  11 ,  13 , rotating frame  22  is pivoted about axis of rotation  58 , for example using an electrically actuated screw-nut combination  64  or using other pivot mechanisms. In this way, paper web  10  is made rigid in the sagging area. In a similar manner, a sagging at one side in the area of fixing station  46  is acquired by sensors S 5 , S 6  and is counteracted and/or completely compensated by pivoting draw-off device  48  about axis of rotation  52  along double arrow  56 . In this way, a sagging at one side is also corrected in the area of the fixing. In the described first variation, a sagging at one side in the area of rotating frame  22 , as well as in the area of fixing station  46 , is thus corrected. This can take place using control algorithms that are stored in the control unit. However, a regulating can also take place in such a way that target values are pre-indicated to the control unit and are compared with actual values from sensors S 5 , S 6  and S 3 , S 4 ; any deviation is corrected by adjusting rotating frame  22  or draw-off device  48 . 
   In the second variation according to  FIG. 5 , in which identical parts have identical reference characters, for the correction of the web tension the signals of sensors S 1 , S 2  in the area of draw-in roll  20  and sensors S 5 , S 6  in the area of fixing station  46  are evaluated. With the aid of the signals from sensors S 1 , S 2 , a web tension that is lessened along one edge  11 ,  13  of paper web  10  can be detected, which is interpreted as a sagging at one side of paper web  10 . Rotating frame  22  is then controlled so as to counteract this decreasing of the tension at this side of web  10 . By means of a control algorithm, the pivoting of rotating frame  22  about axis of rotation  58  takes place in such a way that predetermined forces are achieved for sensors S 1 , S 2 . The setting of the web tension with the aid of sensors S 5 , S 6  takes place as described in relation to the variation according to  FIG. 4 . In this variation as well, a sagging of the paper web at one side is corrected or avoided in the area of rotating frame  22  and in the area of fixing station  46 . 
   In the variation according to  FIG. 6 , a monitoring of paper web  10  takes place only with the aid of sensors S 1 , S 2 , which are situated in the area of draw-in roll  20 . Assuming that the axes of all the conveyor rolls for transporting the paper web are in a basic setting in which they are parallel to one another, a sagging at one side of paper web  10  can be caused only by non-uniform mechanical characteristics of paper web  10 . The signals from sensors S 1 , S 2  thus provide diagnostic information about the characteristics of the web, for example as to whether the web is curved, or has a varying density, or has varying tensions along the axes of its surface. With the aid of empirical values determined from trials and measurements, for each tuple of values of sensors S 1 , S 2 , in which the web width and type of paper are also taken into account, an associated deflection of rotating frame  22  about axis  58  and/or an associated deflection of draw-out device  48  about axis of rotation  52  can take place. Typically, such tuples of values, and the associated control parameters for the required deflection for the rotating frame and for draw-off device  48 , are stored in a memory as a table. In this variation, the expense for sensors is minimal, but a high-quality guiding of the paper web in the printer is achieved nonetheless. Of course, the described variation according to  FIG. 6  can also be combined with the variations according to  FIG. 4  or  FIG. 5 , i.e., the signals of sensors S 3 , S 4  and/or S 5 , S 6  can also be used for the controlling and regulation of paper web  10 . 
   According to a fourth variation, a monitoring of the web tension and a correction take place only in the area of fixing station  46 , in order to avoid a harmful sagging at one side of the paper web. With the aid of the signals from sensors S 5 , S 6  and pivotable draw-off device  48 , a stable web guiding is achieved for the relatively long path of a fixing station  46  operated with infrared radiation. 
   In  FIGS. 7 to 13 , according to a further aspect of the preferred embodiment examples are described that can also be combined with the examples described above.  FIG. 7  shows a high-performance printer in which the device and method according to the preferred embodiment are realized. The printer is divided into a printing mechanism  110  and a fixing station  112 , each having an independent housing  114 ,  116  that are connected to one another. A web  118  of endless paper is fed through both housings  114 ,  116 . In a web inlet area  120  for printing mechanism  110  there is situated a web pull-back motor  122  that exerts a retaining force on web  118  with the aid of a pair of rolls. In addition, a web brake  124  is provided that smoothes web  118  and likewise exerts a retaining force on web  118 . Web brake  124  is, for example, realized by a piece of felt that lies against web  118 . Another possibility is to use a vacuum brake. Here, a variable vacuum is used to apply a vacuum, i.e. suction, to the underside of the web, and the frictional force is modified accordingly. In the web inlet area of pull-back device  120 , or, more precisely, just after (seen in the normal direction of transport) web brake  124 , a second sensor  126  is situated that acquires the actual position of the side edge of web  118 . 
   Via a deflecting roll  128 , web  118  is supplied to a rotating frame  130  that acts as an actuating element for shifting the position of the side edge of web  118 . Rotating frame  130  executes rotational movements about an axis situated perpendicular to web  118 , thereby shifting the side edge in a direction perpendicular to the plane of the paper in  FIG. 7 . In the outlet area of rotating frame  130  there is situated a first sensor  132  that acquires the actual position of the side edge of web  118 . Via two additional deflecting rolls  134 ,  136 , web  118  is supplied to a web drive  138  that contains a roll pair. Web drive  138  moves web  118  forward in the direction of transport, against the retaining force of web brake  124 . 
   Further along the transport path, an upper transfer print station  140  and a lower transfer print station  142  are situated at both sides of web  118 . Both transfer print stations  140 ,  142  print toner images simultaneously on the upper and lower sides of web  118 . The two transfer print stations  140 ,  142  are essentially identical in construction; for this reason, only upper transfer print station  140  is explained in more detail below. Upper transfer print station  140  comprises a character generator  144  that produces an electrostatic charge image on a photoconductor belt  146 , corresponding to a print image that is to be printed. An upper developer station  148  colors in the electrostatic charge image with toner material; the toner images are then transferred onto a transfer belt  150 . Further along, the toner images situated on transfer belt  150  are then transferred onto web  118  at transfer point  152 ; that is, at transfer point  152  toner images are transferred simultaneously by both transfer print stations  140 ,  142 . 
   Seen in the direction of transport, after transfer point  152  there is situated a third sensor  154  that also acquires the actual position of the side edge of web  118 . The not-yet-fixed toner images on web  118  are supplied to fixing station  112 , where they are fixed and cooled on both sides of the web in infrared fixing devices  156 ,  158  and subsequent fans  160 ,  162 . In the outlet area of fixing station  112  there is situated a web draw-off motor  164  that acts on a pair of rotating rolls and that conveys web  118  out of fixing station  112 . 
   The depicted high-performance printer has various operating states in which different tasks occur that relate to controlling the position of the side edges of web  118 : 
   Operating State 1: Automatic Web Placement or Insertion 
   When a new web  118  is put into place, with the aid of a clamp it is automatically passed through printing mechanism  110  and through fixing station  112 , and from there is transported to the web outlet. During the guiding of web  118  with the aid of the clamp, rotating frame  130  and the position controlling system remain inactive. After the putting into place of the web has been completed, rotating frame  130  and the position controlling system are activated. 
   Operating State 2: Placement of a Glued-on Web 
   If a new web is glued onto a previous web, the new web is guided through printing mechanism  110  and fixing station  112  with a transport speed that is significantly less than the normal print speed, in order not to overload the glued point. During the transport of the glued point through the printer, a controlling adapted to the slow transport speed is active. Positional deviations at the side edge can occur as a result of the glued point between the old web and the new web. The controlling task here is to cause the side edge of web  118  to settle into a target position as quickly as possible. After the web has been put into place, the normal positional controlling is activated. 
   Operating State 3: Slow Forward Transport and Backward Transport of the Web 
   In order to position the web as precisely as possible when pre-printed paper (form paper) is being put into place, a slow forward and backward transporting is required. During this positioning, the control device and rotating frame  130  are not active. After this fine positioning is terminated, the following movement of the paper activates the controlling and the rotating frame  130 , and the side edge of web  118  should be brought into the target position as quickly as possible (as in operating states  4  and  5  described below). In this process, it is important that there be as few wasted sheets as possible. 
   Operating State 4: Rapid Forward Transport Without Print Operation 
   At the end of a print job, the side edge of the web should be held in the target position with a defined printing speed, but without printing operation, so that the last-transferred toner images can be fixed in fixing station  112 . At the end of the forward motion of web  118 , a backward motion is introduced so that a new beginning of the operation can be carried out in a correct relation to the form; that is, the print images must be printed on web  118  with a precise positioning in relation to a form. During this forward and backward movement of the web, the controlling and the rotating frame  130  are active; the target position of the side edge of the web should be achieved as quickly as possible, resulting in only a few wasted pages. 
   Operating State 5: Web Transport in Print Operation 
   At the start of the print operation, web  118  is first brought to the target speed, corresponding to the print speed, with transfer stations  140 ,  142  pivoted away. The transfer stations with the transfer belts are subsequently pivoted into place and print operation takes place. At the end of a print operation with forward movement of the web, a backward transport of web  118  is carried out with pivoted-away transfer stations, so that a new beginning of the print operation can take place with a correct positioning in relation to the form. In this operating state the controlling and the rotating frame  130  are active. A rapid settling of the side edge into the target position should take place within the various transport speeds of web  118 . 
   On the basis of a first example having only one sensor  132 ,  FIG. 8  schematically shows the path of web  118  inside devices  110 ,  112  that is necessary for controlling the position of the side edge. Web  118  is conveyed through web inlet area  120 , symbolized by a pair of rolls, to rotating frame  130 , in whose web outlet first sensor  132  is situated. Web  118  is subsequently guided along web drive  138 , transfer point  152 , and draw-off device  164 . 
     FIG. 9  shows a block diagram of the position controlling system for the first exemplary embodiment. Actual signal S 1  from first sensor  132  is supplied to an adder element  170 , and control deviation E is formed. A controller  172 , for example a PID controller, produces a control signal R that is supplied to rotating frame  130  as actuating element  130 . On the basis of control signal R, rotating frame  130  modifies its angle of rotation, thus modifying the lateral position of the side edge of web  118 . The actual position of the side edge is acquired by first sensor  132  as actual signal S 1 , which, as mentioned, is fed back to adder element  170 . This control process continues to take place until control deviation E is equal to zero. The target position and target signal S 0  are defined at the location of first sensor  132  as an electrical signal. 
   First sensor  132  determines measurement values at predetermined intervals along the path of web  118 . A mean value of these measurement values is used as actual signal S 1 . Preferably, a sliding mean value or an exponential mean value is used as the mean value. In the case of a sliding mean value, first a mean value is formed from n measurement values. For each new measurement value that is added, a new mean value is calculated from the previous mean value and the new measurement value. Target value S 0  can be determined in a similar manner in a calibration process. Preferably, the mean value is determined over a predetermined length of the web, in general a whole-number multiple of a standard format length of a print page. Typically, the 12-inch format is used as a standard format length, and the multiple factor is preferably 3. 
   Due to the mean value formation, short-waved positional deviations along the edge of the web do not result in undesirable deflections of the rotating frame. Moreover, due to the mean value formation, excessive positional deviations, caused by resonance, at the transfer printing point are avoided. Such positional deviations caused by resonance can occur in paper webs having side edges cut in the form of waves. Due to the calibration to the standard format length, waviness does not occur along printed lines in print images in the direction of transport of the web within a form length. 
   In this first exemplary embodiment, it can be problematic that the actual position agrees with the target position of the side edge only at the location of first sensor  132 , i.e., in the vicinity of rotating frame  130 . At transfer point  152 , which is essential for the print quality, the side edge of web  118  can again deviate from a target position. As a result of the mean value formation, moreover, the settling-in or response characteristic can be relatively slow. In addition, due to the mean value formation a control deviation can remain permanently, because maximum amplitudes are not removed by the controlling. 
     FIG. 10  shows a further exemplary embodiment having two sensors. Identical parts are designated with identical reference characters. Second sensor  126  is situated in web draw-in area  120 . The rest of the system agrees with the one shown in  FIG. 8 . 
     FIG. 11  shows a block diagram of the associated position control system for the side edge of web  118 . With the aid of signal S 2  from second sensor  126 , controller  172 , which outputs control quantity R to rotating frame  130 , is influenced. Second sensor  126  represents, in its signal S 2 , the deviation of the position of the side edge of web  118  in web draw-in area  120 , i.e., it determines the deviation of the actual position of the side edge from a target position in the area of web brake  124  (cf.  FIG. 7 ). For this purpose, it is useful that in web draw-in area  120  there is situated a web feed-in device that comprises a lateral stop (not shown) along which the relevant side edge of web  118  is guided. In this way, a stable initial situation for the side edge of the web is created in the draw-in area of web  118 . 
   Second sensor  126  preferably contains a delay element VZ. The delay time for signal S 2  corresponds to the time required for web  118  to be transported from the location of second sensor  126  to the location of first sensor  132 . In this way, the deviation of the side edge from a target value in web draw-in area  120  can be compensated in a time-delayed manner. Thus, the deviation of the side edge from a reference value in the web draw-in area is determined, and as a first alternative, signal S 2  is added to target value S 0  (shown in broken lines in  FIG. 11 ). As a second alternative, signal S 2  is applied directly to controller  172 , which forms control quantity R, taking into account this signal S 2 . In this exemplary embodiment according to  FIG. 11 , no mean value formation is carried out for signal S 1  of first sensor  132 , because this would disturb the compensation using signal S 2 . 
   The advantage of the positional controlling according to  FIG. 11  is that only the long-waved deviations of the mean actual position of the side edge from a target position at the location of first sensor  132  are compensated by rotating frame  130 . Due to the taking into account of a deviation of the side edge in the draw-in area of web  118 , the startup or response characteristic of the control circuit is relatively fast. In this example according to  FIG. 11 , it is also to be noted that the control deviation at the location of first sensor  132  can be minimal, but at the location of transfer point  152  deviations from an optimal position of the side edge can nonetheless occur. 
     FIG. 12  schematically shows the design having three sensors  126 ,  132 , and  154 . Second sensor  126  is optional, as is indicated by broken lines. Third sensor  154  is situated within an area of ±100 mm relative to transfer point  152  of transfer stations  140 ,  142 , because transfer point  152  itself is difficult to access. 
     FIG. 13  shows the associated positional controlling using signals S 1  of the first sensor, S 3  of the third sensor, and, optionally, signal S 2  of the second sensor. The positional control system contains, in addition to addition element  170 , addition elements  174  and  176 . Addition element  176  is supplied with signal SU, which reproduces the target position at sensor  154 , i.e., in the vicinity of transfer point  152 . Addition element  176  carries out the target value/actual value comparison between signals SU and S 3 . The result is supplied to addition element  174 , whose result is in turn supplied to addition element  170 . At addition element  170 , actual value S 1  of first sensor  132  in the area of rotating frame  130  is taken into account. As in the example according to  FIG. 5 , the signal of second sensor S 2  can optionally be taken into account as a delayed signal at controller  172  or at addition element  170  (this variant is not depicted). Optionally, signal S 2  can also be taken into account in the formation of signal S 3 , i.e., signal S 2  acts on third sensor  154 . 
   With the aid of the controlling according to  FIG. 13 , it is possible to take into account the positional deviation directly at transfer point  152 . Signal S 3 , possibly also taking into account signal S 2 , forms, after combination in adder elements  176  and  174 , target signal S 0  for the control circuit containing addition element  170 . In order to keep the control system free of oscillations, signal S 0  must change only slowly, for example more slowly than signal S 1  by a factor of 110. The advantage of the arrangement according to  FIG. 13  is that a deviation of the side edge in the area of transfer point  152  is also recognized and is controlled out by rotating frame  130 . 
   In the following  FIGS. 14 to 24 , examples of a rotating frame are shown according to a further aspect of the present invention. These examples can be combined with the previously described examples. In  FIG. 14 , a web guiding device is shown that has a single driven roll  210  mounted in a rotating frame  212 . Rotating frame  212  can be pivoted about an axis of rotation  214  that runs essentially perpendicular to drawn-off web  216 . Within rotating frame  212 , counter-rolls  218  are also mounted that press web  216  against roll  210  with a predetermined force. Roll  210  is driven by a drive  220  and a gear mechanism  222 . Due to the friction on the surface of roll  210 , web  216  is conveyed in the direction of arrow P 21 . Web  216  has the tendency to be conveyed in the tangential direction away from the surface of the jacket of roll  210 . By rotating the rotating frame  212  by an angle α about axis  214  corresponding to arrow P 22 , the transport direction of web  216  conveyed by roll  210  is also influenced. Accordingly, the position of the edge of web  216  in relation to a reference position can be modified in the direction of the shaft of roll  210 . 
   In order to rotate rotating frame  212 , an electrical drive  226  can for example be used that moves rotating frame  212  by small angular amounts, typically by 1°, clockwise or counterclockwise corresponding to arrow P 22 . Drive  226  contains a nut  228  in which a spindle  230  is moved back and forth. In order to ensure definite positions in the deflection of rotating frame  212 , the unavoidable play due to tolerances between nut  228  and spindle  230  is prevented by a tension spring  232 . This has the effect that when spindle  230  moves forward and backward, nut  228  always lies against the same flank of the spindle. 
   When there is a rotational movement in the direction of arrow P 22 , conveyed web  216  is subjected only to minimal forces. However, it is also possible to situate axis of rotation  214  off-center in relation to rotating frame  212 . In the example according to  FIG. 14 , web  216  is guided centrically in relation to roll  210 . However, it is also possible to situate web  216  off-center. 
   In addition, in the example according to  FIG. 14 , web  216  is narrower than roll  210 . However, it is also possible for this web to extend past one or both sides of roll  210 , so that the width of roll  210  is smaller than the width of web  216 . 
     FIG. 15  schematically shows the arrangement according to  FIG. 14  in cross-section. Web  216  comes into contact with the surface of roll  210  with a predetermined wrap angle β. Typically, the angular range for the wrap angle is between 3° and 80°. The greater the wrap angle, the stronger the frictional connection is with the surface of driven roll  210 . 
   Wrap angle β defines the length of contact zone  234  in which web  216  makes contact with the surface of roll  210 . This contact zone  234  has a smoothing effect on incoming web  216 , so that the effect of the creasing of web  216  when roll  210  is rotated is reduced. The smoothing effect can be increased if the contact point of counter-roll  218  with web  216 , seen in the direction of travel of web  216 , is situated at the end of wrap angle β. 
   Roll  210  has on its surface a friction lining made for example of a pure closed cell material having a hardness of approximately 80 ShA. Spring-loaded counter-rolls  218  effect a largely drag-free transmission from driven roll  210  to web  216 . Through a defined setting of the pressure forces of counter-rolls  218  on driven roll  210 , a denting or damaging of the surface of roll  210  is avoided, and a constant surface speed of web  216  is thus ensured. Counter-rolls  218  have a lining made of a softer material than roll  210 . For example, the lining is made of foamed pure material having a hardness of approximately 50 ShA. 
     FIG. 16  shows an example having a small wrap angle β. With a wrap angle of this sort as well, the position of web  216  can be shifted by rotating the rotating frame. 
     FIG. 17  shows an example in which web  216  is fed in from below. In addition, axis of rotation  214  is situated perpendicular to drawn-off web  216 , as can be seen in examples a) and b). Examples c), d), and e) show web guiding in a top view in example a), with various angles of rotation α in relation to a normal position of 0°. 
     FIG. 18  shows an example in which axis of rotation  214  is situated parallel to the direction of transport of drawn-off web  216 . When there is a rotation by angle of rotation P 12 , a change of the position of web  216  likewise takes place in the direction of shaft  224  of roll  210 . Examples a) and b) illustrate the arrangement with axis of rotation  214  situated parallel to the direction of transport of web  216 . Examples c), d), and e) show different deflections in the direction of angle of rotation P 22 , seen in the direction of axis of rotation  214 . 
     FIG. 19  shows a web guiding device  240  that is situated before the driven roll  210  depicted in the preceding Figures, seen in direction P 10  of web transport. Web guiding device  240  acts on the one hand to preset a position of the edge of web  216 , and on the other hand to create a predetermined web tension. 
   Web guiding device  240  contains a guide sheet  242 , for example a guide plate, in the form of a partial cylinder jacket surface on which web  216  slides. Guide sheet  242  has, at each web edge side, plates  244 ,  246  that guide web  216  at both sides. The spacing from one another of plates  244 ,  246  can be adjusted to fit the width of web  216 . 
   Before guide sheet  242 , guide elements  248 ,  250 ,  252  are situated that can also bear plates, as is shown for guide element  252  with plates  254 ,  256 . These plates  254 ,  256  have the effect that web  216 , drawn off by a roll  258 , already assumes a predetermined lateral position in the inlet area. 
   Guide elements  248 ,  250 ,  252  can be realized as cylinders over whose respective jacket surfaces web  216  is guided at predetermined wrap angles. The respective wrap angle can be set by modifying the position of the shafts of guide elements  248 ,  250 ,  252  relative to one another. This is important if the same web tension is required for web materials having different thicknesses. 
   In order to further set the web tension in a defined manner, a braking device is provided that engages guide sheet  242 . For example, this braking device can be realized by a felt flap  260  that presses with a modifiable weight against web  216  sliding over guide sheet  242 . In addition, devices as described in patent application DE 44 01 906 of the present applicant can be used for the pre-centering and tightening of web  216 . The cited patent application DE 44 01 906 is hereby incorporated by reference into the content of the disclosure of the present application. 
     FIG. 20  shows a web  216  provided with adhesive labels E. In a web  216  of this sort used in practice, in a printer or copier only the labels are to be printed. Here the problem arises that when the edge of a label meets counter-roll  218 , this counter-roll is deflected by a travel distance h, as is shown in broken lines in  FIG. 19 . The travel work of counter-roll  218  that is applied causes an abrupt change in torque, with an accompanying change in the load angle on drive motor  220  (cf.  FIG. 14 ). During operation, in a printer such an effect results in a worsening of the print image, in particular if fine gray rasters are printed. The use of a soft lining for counter-pressure roll  218 , for example a foamed pure material, reduces this effect, because the travel energy of counter-roll  218  is absorbed by the elasticity of the lining. 
   In  FIG. 21 , it is indicated that the travel h is reduced if a corresponding elastic lining is used. 
     FIG. 22  shows an arrangement of web  216  in which the labels are situated on the side facing driven roll  210 . Due to the wedge effect of web  216  on the edge of the labels, a kind of starting bevel is formed, so that the travel work for counter-roll  218  is not applied abruptly. Of course, the arrangement according to  FIG. 22  can be combined with the arrangement according to  FIG. 21 . 
     FIG. 23  illustrates that counter-rolls  218  can be jointly pivoted away from driven roll  210 , thus opening a gap SP that is sufficiently large to admit a web  216 , shown in broken lines. In this way, the putting into place of a new web  216  is made easier. 
     FIG. 24  shows a further example of the preferred embodiment. Driven roll  210  is situated in stationary fashion, i.e., its axis does not change. Counter-roll device  270  contains a multiplicity of rolls  272  that press web  216  against roll  210 . The multiplicity of rolls  272  and roll  210  are held by a rotating frame. Each roll  272  can be pivoted to the same degree about an axis of rotation  274 . Through a rod  276  that engages with a lever end for each roll  272 , the angle of rotation of the respective roll  272  can be adjusted. Here as well, web  216  has the tendency to be conveyed away in a direction tangential to the surface of the respective roll  272 , and in this way the position of the edge of web  216  can be modified in the direction of the roll shaft. The additional variations described above, for example with respect to the linings of driven roll  210  and the linings of rolls  272 , can also be used here. 
   Many variations are possible. The rotating frame described in  FIG. 14  can for example be part of a control circuit. The actual position of the edge of web  216  is determined with the aid of a sensor in relation to a target position. Dependent on the signal from the sensor, the angle of rotation P 12  of the frame is adjusted in steps or continuously in such a way that a control deviation between the actual position and the target position of the edge is reduced. 
   In relation to the exemplary embodiment according to  FIG. 24 , all counter-pressure rolls  272  are controlled simultaneously with the aid of rod  276  and a drive. This drive can be part of a control circuit. With the aid of a sensor, the actual position of the edge in relation to a target position is determined. Depending on the signal of the sensor, the angle of rotation for each counter-roll  272  is adjusted in such a way that a control deviation between the actual position and the target position of the edge is reduced or eliminated. 
   The depicted examples of the various aspects of the preferred embodiment can be advantageously combined with one another, resulting in further variations. Thus, the rotating frame shown in  FIGS. 14 and 24  can be used in the example according to  FIGS. 1 and 7 . The controlling of the side edge of the web according to  FIGS. 7 to 13  can be used in the examples according to  FIGS. 1 to 7  and  FIGS. 14 to 24 . 
   Although in the drawings, and in the above description, a preferred exemplary embodiment has been shown and described in detail, these should be understood only as examples, and not as limiting the present invention. It is hereby noted that only the preferred exemplary embodiment has embodiments have been represented and described, and that all changes and modifications lying within the scope of protection of the present invention currently and in the future are to be protected.