Abstract:
A device for regulating the tension of a moving web of material, in particular a web of paper in a paper-working machine such as a corrugating machine, comprises a machine frame; a first roller that is mounted for rotation about a first axis of rotation in relation to the machine frame, taking up a web of material by an angle of contact a; and a supporting device, which supports itself on the machine frame, and which is mounted for pivoting about the first axis of rotation by a pivoting drive, and which supports at least a second roller mounted for rotation about a second axis of rotation that is substantially parallel to the first axis of rotation; wherein the angle of contact a of the web of material on the first roller is modifiable by the at least one second roller being pivoted about the first roller.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a device for regulating the tension of a moving web of material, in particular a web of paper in a paper-working machine such as a corrugating machine.  
           [0003]    2. Background Art  
           [0004]    A single facer for the manufacture of single-faced board is known from WO 00/00347, in which a liner and a medium are supplied to the unit for the manufacture of corrugated board. Prior to this, the liner is led around a cylinder, in the surface of which are provided numerous ports with water vapor exiting there-from for increased feeding of water into the liner. This arrangement is not capable of regulating and defining the tension of the liner web. Drawbacks of this arrangement further reside in that embodying the cylinder with corresponding steam passages is extraordinarily complicated. Moreover, quite a lot of vapor escapes unused in the peripheral areas of the cylinder that are not encircled by the liner web. Consequently, it is rather difficult, owing to this inaccuracy in the supply of water vapor, to pre-select and regulate the friction between the cylinder and liner web and thus the web tension that will result downstream of the cylinder.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to embody a device for regulating the tension of a moving web of material by which to regulate the web tension as precisely and in as simple a way as possible.  
           [0006]    The object is attained in that the angle of contact a of the web of material on the first roller is modifiable by the at least one second roller being pivoted about the first roller. The gist of the invention resides in providing a first roller and at least a second roller that is mounted for pivoting about the first roller, with a web of material being passed around the first roller and the at least second roller. By the second outer roller being pivoted about the first inner roller, the angle of contact of the web of material on the first roller can be modified, and thus the friction between the web of material and the first roller. This helps affect the tension of the web of material downstream of the first roller.  
           [0007]    Additional features and details of the invention will become apparent from the description of two exemplary embodiments, taken in conjunction with the drawing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]    [0008]FIG. 1 is a lateral view of a detail of a corrugating machine with a web-tension-regulating unit in a first embodiment;  
         [0009]    [0009]FIG. 2 is a plan view of the web-tension-regulating unit according to FIG. 1;  
         [0010]    [0010]FIG. 3 is a lateral view of the web-tension-regulating unit according to FIG. 1 in a first position;  
         [0011]    [0011]FIG. 4 is a lateral view of the web-tension-regulating unit according to FIG. 1 in a second position;  
         [0012]    [0012]FIG. 5 is a lateral view of a detail of a corrugating machine with a web-tension-regulating unit in a second embodiment;  
         [0013]    [0013]FIG. 6 is a lateral view of the web-tension-regulating unit according to FIG. 5 in a first position; and  
         [0014]    [0014]FIG. 7 is a lateral view of the web-tension-regulating unit according to FIG. 5 in a second position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    The following is a description of a first embodiment of the invention, taken in conjunction with FIGS.  1  to  4 . A machine  1  for the manufacture of a web of single-face board  2  comprises a liner web delivery unit  3 , with a liner web  4  being passed around several deflection rollers  5  and around a preheating roller  6  also designated as a pre-heating cylinder for heat-up of the liner web  4 . Then the liner web  4  is led through a web-tension-regulating unit  7  that serves for regulating the tension of the liner web  4  and will be described in detail below. Then the liner web  4  is fed, via further deflection rollers  5 , to a corrugated-board-manufacturing unit  8 . A web of board termed the medium  10  is supplied to the corrugated-board-manufacturing unit  8  by a medium delivery unit  9 . In the medium delivery unit  9 , the medium  10  is passed over several deflection rollers  5  as well as two preheating rollers  11 , also called pre-heating cylinders, and is then delivered to the corrugated-board-manufacturing unit  8 . This comprises a fluted unit  12  for the medium  10  to be corrugated. Then the corrugated medium  10  is passed along the adhesive applicator unit  13  and, in a nip pressure unit  14 , united with the liner web  4  that is trained over a pre-heating roller  15  (also pre-heating cylinder) and a web tension sensor  16 . The finished web of single-face board  2  is discharged upwards via a discharge unit  17  and temporarily stored in a place of deposit  18 . The units  3 ,  8 ,  9 ,  12 ,  13 ,  14 ,  17  are elements of a corrugating machine  1  that have been known for a long time.  
         [0016]    The following is a detailed description of the design of the web-tension-regulating unit  7 . The unit  7  comprises a main roller  21  which is vapor-heated from inside and rotatably mounted in bearings  20  relative to a machine frame  19 . The roller  21  has bearing journals  22  that project from its ends and are mounted in the bearings  20 . The roller  21  rotates about an axis of rotation  23 . Between the machine frame  19  and the roller  21 , a pulley  25  is rotatably mounted on both bearing journals  22  by way of a bearing  24 , having two radially projecting arms  26  and  27  that make between them an angle b of b≈60°, it being possible also to use other angles b. A front roller of web contact  28  and a rear roller of web contact  29  are rotatably mounted between the two opposing arms  26  and  27  of the two pulleys  25 . The rollers  28  and  29  rotate about corresponding axes of rotation  30  and  31 . The axes of rotation  23 ,  30  and  31  are parallel to each other. The pulleys  25 , inclusive of the rollers  28  and  29 , are mounted for pivoting relative to the axis of rotation  23  by a chain drive  32 . To this end, the pulleys  25  have an encircling gear rim  33  of a diameter Dz. Passed around each gear rim  33  is a chain  34  which, at the driving end, is passed over two gear rims  36  that are connected to a drive shaft  35 . The drive shaft  35  is run by both ends in bearings  37  in relation to the machine frame  19 . The shaft  35  is drivable by a motor  38  that is joined to it. The gear rims  36  have an outside diameter D K . The transmission ratio that the small gear rim  36  bears to the great gear rim  33  is D Z /D K ≈4, other transmission ratios being conceivable too. The main roller  21  is driven for rotation by a motor  39  that is connected to the bearing journal  22 , with the tangential outer peripheral velocity of the roller  21  being v W . The unit of the two pulleys  25  inclusive of the arms  26  and the rollers  28  and  29  is designated as a supporting device.  
         [0017]    A humidifier unit  40  is provided where the liner web  4  is delivered to the unit  7 , spraying water vapor on the side of the liner web  4 —the upper side in FIGS. 3 and 4—that is subsequently turned towards the main roller  21 . The liner web  4 , prior to reaching the main roller  21 , has a velocity termed v B . The liner web  4 , while passing around the rollers  21 ,  29  and  30 , is trained through the nip between the roller  29  and the roller  21  and then through the nip between the roller  28  and the roller  21 . The liner web  4  rests on the main roller  21  by a variable angle of contact a.  
         [0018]    For web tension determination, the web tension sensor  16  is provided in the unit  8  between the pre-heating roller  15  and the nip pressure unit  14 , taking the tension of the liner web  4  and transmitting a corresponding signal via a line  41  to a central control unit  42 . Via lines  43  and  44 , the control unit  42  is connected with the motors  38  and  39 .  
         [0019]    The following is a description of how the web-tension-regulating unit  7  works. The tension of the liner web  4  downstream of the unit  7  is affected by two variables, one of them consisting in how rapidly the main roller  21  is driven. For braking the liner web  4  i.e., for increasing the web tension downstream of the unit  7 , the peripheral velocity v W  of the main roller  21  is lower than the velocity v B  of the liner web. In the extreme, the main roller  21  does not rotate. Another possibility of web tension modification resides in modifying the angle of contact a of the liner web  4  around the main roller  21 , which changes the frictional force between the surface of the main roller  21  and the liner web  4 .  
         [0020]    The position of the rollers  28  and  29  seen in FIG. 3 shows the smallest angle of contact a, to which a ≈10° applies. In this arrangement, the liner web  4  is supplied by the liner web delivery unit  3  to the web-tension-regulating unit  7 , first passing the humidifier unit  40  which sprays water vapor on the upper side of the liner web  4 , thus increasing the friction between the liner web  4  and the main roller  21  as compared to a dry liner web  4 . Then the liner web  4  is slightly deflected by the roller  29  and passed along the main roller  21  by an angle of contact a, after which it is deflected on the roller  28  and led towards the corrugated-board-manufacturing unit  8 . The web tension sensor  16  continuously takes the tension of the liner web  4 . If the tension is too low, the control unit  42  transmits corresponding signals to the motors  38  and/or  39 . For web tension increase, the velocity v W  of the main roller  21  may be reduced. If this is not sufficient, the rollers  28  and  29  are pivoted clockwise by way of the motor  38  and the chain drive  32 , with the angle of contact a increasing. FIG. 4 shows a position with a great angle of contact a. The supply of water vapor augments the friction between the liner web  4  and the main roller  21 , which is in particular desirable for web tension regulation. Water vapor is supplied to the side of the liner web  4  that is turned towards the main roller  21 . Moreover, the liner web  4  must have a certain humidity for adhesion to the medium  10  in the nip pressure unit  14  to be produced impeccably. The web-tension-regulating unit  7  enables the tension of the liner web  4  to be kept constant near the web tension sensor  16  i.e., directly prior to adhesion to the medium  10 . Typically, the angle of contact a must be increased as the velocity v B  of the liner web  4  increases for constant web tension to be maintained at the web tension sensor  16 . It is also possible to determine the web tension by the current of the motor  38  of the pivoting drive. The higher the web tension, the greater is the energy to be mustered up by the motor  38 —and thus the current needed—for keeping a certain angle of contact a. There is no need of a web tension sensor in the case of this simple type of web-tension measuring.  
         [0021]    The following is a description of a second embodiment of the invention, taken in conjunction with FIGS.  5  to  7 . Identical parts have the same reference numerals as in the first embodiment, the description of which reference is made to. Parts of identical function that differ in construction have the same reference numeral provided with a prime. The essential difference from the first embodiment resides in that the liner web  4  is passed over the main roller  21  instead of substantially below the main roller  21  as in the first embodiment. Correspondingly, the humidifier unit  40 ′ is disposed underneath the liner web  4  in order for the side turned towards the main roller  21  to be moistened by vapor as with the first embodiment. FIG. 6 shows a position, corresponding to FIG. 3, of the rollers  28  and  29 , in which the angle of contact a is minimal. In the case of the arrangement according to the second embodiment, it is possible, as seen in FIG. 6, to obtain an angle of contact of a=0° i.e., the liner web  4  does not at all contact the main roller  21  and is passed only around the roller  28  and led off through the nip between the roller  29  and the roller  21 . In the case of this arrangement, there is the lowest frictional resistance as compared to all the other positions of the rollers  28  and  29 . Pivoting the rollers  28  and  29  counter-clockwise about the axis of rotation  23  will increase the angle of contact a. FIG. 7 illustrates a situation with a great angle of contact of a≈270°. Advantages of the second embodiment as opposed to the first embodiment reside in that there is a wide range of angles of contact that can be set, in the present case 0°≦a≦270°. It is possible to set even greater angles of contact a.