Abstract:
The present invention provides a tension control device including a dancer for controlling the tension of a web by applying force to the web, wherein the dancer includes a first ultrasonic vibration unit, the first ultrasonic vibration unit carries out ultrasonic-vibration and applies the force to the web in a non-contact state by applying repulsive force according to the ultrasonic vibration thereof. In addition, the present invention provides a continuous web processing method, comprising the steps of: controlling the tension of the web by using the tension control device; and processing the tension-controlled web.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a tension adjustment device and a continuous web processing method using the same, and more particularly, to a tension adjustment device able to adjust the tension of a web by applying repelling force induced from ultrasonic vibrations to the web and a continuous web processing method using the same. 
         [0003]    2. Description of Related Art 
         [0004]    A web refers to a soft material that is continuous in length. A web processing system for continuously processing such a web includes a winder, an unwinder, a plurality of driven rollers, a plurality of idler rollers, etc. Continuous processing is generally undertaken using a roll-to-roll process or a roll-to-sheet process. A dancer device is used as an approach to control the tension of a web in the roll-to-roll and roll-to-sheet processes. The dancer device may be configured to apply a predetermined amount of tension to the web regardless of changes in the position of the web by applying a certain amount of force in one direction to the web using a pressing device, such as a spring, a pneumatic pressure device or a weight. 
         [0005]      FIG. 1  schematically illustrates a tension adjustment device commonly used in the related art. 
         [0006]    As illustrated in  FIG. 1 , a dancer roller  311  adjusts the tension of a web W through mechanical contact (friction) with the web W. Support rollers  312  and  313  support the web W in fixed positions. 
         [0007]    A web, more particularly, a thin glass web or thin glass sheets produced from the thin glass web can be used in a variety of fields, such as displays, electronic materials (e.g. photovoltaic cells, touch sensors, or wafers), construction and home appliances. Such a thin glass web is vulnerable to mechanical contact before being coated with a protective film. Thus, an uncoated glass web that has not yet been coated with a protective film is required to avoid mechanical contact. In addition, a thin glass web may damage the surface of a roller since it is typically a high-hardness glass material. Tension adjustment devices of the related art use chromium (Cr) coatings in order to protect rollers from damage. However, relatively expensive Cr coatings are a factor in increased equipment costs. 
         [0008]    In the related art, there are provided a method of supporting a web using a contact (friction) dancer roller and a method of supporting a web by discharging fluid from a fluid vent onto the outer surface of an arc-shaped dancer roller through non-contact technology. However, these methods have the following drawbacks. The former method tends to damage the surface of a thin glass web through mechanical contact. According to the latter method, it is critically difficult to uniformly adjust the height of the web using only the flow rate of the compressed air and the force of maintaining the dancer roller in a state of non-contact with the web (repelling force) is very weak. Thus, the web tends to touch the dancer roller when the web is in an unstable state (e.g. trembling) (Korean Patent Application Publication No. 10-2011-0095191, titled “NON-CONTACT DANCER MECHANISM”). 
         [0009]    In addition, since the thin glass web has the characteristics of a brittle material, it tends to break when subjected to any related-art method of controlling the tension of the web based on elongation. Furthermore, in the related art, when the web is transported, the tension of the web is controlled, based on the elongation of the web. More particularly, the tension of the web is controlled by elongating the web by moving the dancer roller upwardly and downwardly. However, this may increase the possibility that the thin glass web may be subjected to mechanical contact or may be damaged, since the thin glass web formed of a brittle material has a small elongation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    Various aspects of the present invention provide a dancer mechanism for maintaining a web under uniform tension against tension disturbances during transportation by applying a uniform amount of force (pressure) to the web without mechanical contact. 
         [0011]    In an aspect of the present invention, provided is a tension adjustment device including a dancer able to adjust the tension of a web by applying force to the web. The dancer includes a first ultrasonic vibrator that generates ultrasonic vibrations and applies the force to the web in a non-contact manner by applying repelling force induced from the ultrasonic vibrations to the web. 
         [0012]    In another aspect of the present invention, provided is a continuous web processing method that includes the following operations of: adjusting the tension of a web using the above-described tension adjustment device; and processing the tension-adjusted web. 
         [0013]    According to the present invention as set forth above, the tension adjustment device includes the non-contact dancer mechanism in order to reliably transport a web (e.g. by controlling tension that occurs during transportation and preventing mechanical contact), and the continuous web processing method continuously processes the web using the same device. 
         [0014]    Accordingly, it is possible to prevent a brittle material, such as a thin glass web, from being damaged through mechanical contact with, for example, a dancer roller. In addition, additional processing on the dancer roller, such as mechanical coating, is not required. Furthermore, it is possible to adjust the tension of the web while transporting the web at a uniform height. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  schematically illustrates a tension adjustment device commonly used in the related art; 
           [0016]      FIG. 2  schematically illustrates the basic principle of tension adjustment according to the present invention; 
           [0017]      FIG. 3  to  FIG. 13  schematically illustrate first to eleventh exemplary embodiments of a tension adjustment device according to the present invention; 
           [0018]      FIG. 14  and  FIG. 15  schematically illustrate a twelfth exemplary embodiment of the tension adjustment device according to the present invention; 
           [0019]      FIG. 16  to  FIG. 18  schematically illustrate a thirteenth exemplary embodiment of the tension adjustment device according to the present invention; and 
           [0020]      FIG. 19  schematically illustrates an exemplary embodiment of a continuous web processing method according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Reference will now be made in detail to the present invention, embodiments of which are illustrated in the accompanying drawings and described below, so that a person skilled in the art to which the present invention relates could easily put the present invention into practice. 
         [0022]    Throughout this document, reference should be made to the drawings, in which the same reference numerals and signs are used throughout the different drawings to designate the same or similar components. In the following description of the present invention, detailed descriptions of known functions and components incorporated herein will be omitted in the case that the subject matter of the present invention is rendered unclear. 
         [0023]    A roll-to-roll process or a roll-to-sheet process for continuous web processing controls tension disturbances occurring during the transportation of a web using a non-contact dancer. 
         [0024]    The present invention relates to the processing of a web formed of a brittle material, such as a thin glass web, and more particularly, to a tension control device including a non-contact dancer for transporting a web formed of a brittle material and a continuous web processing method using the same. 
         [0025]      FIG. 2  schematically illustrates the basic principle of tension adjustment according to the present invention. 
         [0026]    A tension adjustment device according to the present invention includes a dancer  320 . The dancer  320  shown in  FIG. 2  includes a first ultrasonic vibrator  321 , ultrasonic wave generator  322 , a vibration absorber  324  and a fixed frame  325 . The dancer  320  adjusts the tension of a web W by applying force to the web W. The first ultrasonic vibrator  321  of the dancer  320  generates ultrasonic vibrations. The first ultrasonic vibrator  321  applies force to the web W in a non-contact manner (or without contact) by applying the repelling force of a high-pressure air layer induced from the ultrasonic vibrations to the web W. 
         [0027]    The ultrasonic wave generator  322  of the dancer  320  vibrates the first ultrasonic vibrator  321  by generating ultrasonic waves. In addition, the vibration absorber  324  of the dancer  320  prevents the vibrations of the first ultrasonic vibrator  321  from being transferred to the other components of the tension adjustment device. 
         [0028]    Ultrasonic oscillation technology is applied in order to separate the web W from the outer surface of the dancer  320  (Korean Patent Application Publication No. 10-2010-0057530). Periodic air compression due to the ultrasonic waves generates a force for repelling the web W from the outer surface of the dancer  320 , thereby preventing mechanical contact and damage between the dancer  320  and the web W formed of a brittle material. 
         [0029]    Unlike a non-contact tension adjustment device using a fluid vent of the related art, when the web W is in an unstable state (vibrating or trembling), the amount of the repelling force is automatically adjusted. Consequently, the repelling force can be applied uniformly over the entire surface, thereby uniformly maintaining the dancer in a state of non-contact with the thin glass web W. 
         [0030]    For the purpose of tension control, an amount of force is continuously applied to the web W from the outside so that the web W remains under constant tension. For the purpose of speed control, when one of an unwinding side and a winding side is a master and the other is a slave, it is possible to control and synchronize the difference between the unwinding speed and the winding speed in real time by increasing and decreasing the winding speed of the slave by measuring and feedbacking the height of the dancer  320  in real time. 
         [0031]    Here, the web W can typically be thin glass, but the present invention is not limited thereto. The web W according to the invention can be formed of a variety of other materials. 
         [0032]      FIG. 3  schematically illustrates a first exemplary embodiment of the tension adjustment device according to the present invention. 
         [0033]    Referring to  FIG. 3 , the tension adjustment device includes a link  331  supporting the dancer  320 . One end of the link  331  is hinge-connected to the dancer  320 , and the other end of the link  331  is hinge-connected to a fixed point. Thus, the dancer  320  can freely rotate about the fixed point as the center of rotation, and can apply a uniform amount of force, corresponding to the weight thereof, to the web W. Accordingly, the tension adjustment device can actively adjust the tension of the web W. 
         [0034]      FIG. 4  and  FIG. 5  schematically illustrate second and third exemplary embodiments of the tension adjustment device according to the present invention. 
         [0035]    The portion of the outer surface of the first ultrasonic vibrator  321  that faces the web W may form an open curve along the lengthwise direction of the web W, as illustrated in  FIG. 4 , or the outer surface of the first ultrasonic vibrator  321  may form a circle, as illustrated in  FIG. 5 . Although a dancer roller of the related art rotates due to friction thereof with the web W, the dancer  320  according to the present invention does not rotate together with the web W since it pushes the web W using compressed air in a non-contact manner without friction. Therefore, unlike the circular dancer roller of the related art, the outer surface of the first ultrasonic vibrator  321  is not necessarily circular. 
         [0036]    Each of the tension adjustment devices illustrated in  FIG. 4  and  FIG. 5  includes a support unit supporting the web W in a fixed position. The support unit includes second ultrasonic vibrators  341  and  342  that generate ultrasonic vibrations. While the first ultrasonic vibrator  321  applies repelling force to the first surface of the web W, the second ultrasonic vibrators  341  and  342  apply repelling force induced from the ultrasonic vibrations thereof to the second surface, i.e. the rear surface of the first surface, thereby supporting the web W in a non-contact manner. 
         [0037]    The dancer  320  and the arc-shaped support unit are configured to hold the thin glass web W along a smooth curve, as illustrated in  FIG. 4  and  FIG. 5 . Consequently, stress on the thin glass web W formed of a brittle material is minimized, such that the thin glass web W is not broken. 
         [0038]    It is also possible to use the dancer  320  in place of the fixed position support unit as required. 
         [0039]      FIG. 6 ,  FIG. 7 ,  FIG. 8  and  FIG. 9  schematically illustrate fourth to seventh exemplary embodiments of the tension adjustment device according to the present invention. 
         [0040]    Each of the tension adjustment devices illustrated in  FIG. 6  to  FIG. 9  includes a link  332 , of which one end is coupled with the dancer  320 , and the other end is coupled with a piston of a cylinder  333  (e.g. a hydraulic cylinder or a pneumatic cylinder). The inner pressure of the cylinder is maintained constant, and the difference between the inner pressure and the outer pressure is applied to the dancer  320  through the link  332 . That is, the dancer  320  is mechanically connected to the cylinder  333  such that it applies constant pressure to the web W. 
         [0041]    A variety of other pressing means can be used. For example, a spring may be provided, of which one end is coupled with the dancer  320 , the other end is connected to a fixed point. That is, the dancer  320  is mechanically connected to the spring such that it uniformly applies constant elastic force to the web W. 
         [0042]      FIG. 10  and  FIG. 11  schematically illustrate eighth and ninth exemplary embodiments of the tension adjustment device according to the present invention. 
         [0043]    As illustrated in  FIG. 10  and  FIG. 11 , each of the tension adjustment devices according to these embodiments provides a non-contact dancer mechanism including the dancer  320  and the cylinder  333 . The non-contact dancer mechanism performs an operation of moving a web W upwardly or downwardly while maintaining the web W in a horizontal state. 
         [0044]      FIG. 12  and  FIG. 13  schematically illustrate tenth and eleventh exemplary embodiments of the tension adjustment device according to the present invention. 
         [0045]    As illustrated in  FIG. 12  and  FIG. 13 , each of the tension adjustment devices according to these embodiments provides a non-contact dancer mechanism including the dancer  320  and top and bottom cylinders  333 T and  333 B that are vertically disposed. This mechanism can minimize the bending stress of a brittle material by holding a web W along a smooth curve, and can minutely adjust tension in the upward-downward direction. 
         [0046]    Each of the tension adjustment devices illustrated in  FIG. 12  and  FIG. 13  further includes a top link  332 T and a bottom link  332 B that are coupled with the dancer  320 , in opposite directions towards both surfaces of the web W. One end of the top link  332 T is coupled with the dancer  320 , and the other end of the top link  332 T is coupled with a piston of the cylinder  333 T. One end of the bottom link  332 B is coupled with the dancer  320 , and the other end of the bottom link  332 B is coupled with a piston of the cylinder  333 B. 
         [0047]      FIG. 14  and  FIG. 15  schematically illustrate a twelfth exemplary embodiment of the tension adjustment device according to the present invention. 
         [0048]    As illustrated in  FIG. 14  and  FIG. 15 , when a thin glass web W is being transported, the widthwise ends of the non-contact dancer  320  may move upwardly and downwardly independently in response to difference between tensions of the widthwise ends of the web W. It is therefore possible to respond to widthwise difference in the tension without elongating the thin glass web W. 
         [0049]    The tension adjustment device illustrated in  FIG. 14  and  FIG. 15  includes a left link  332 L and a tilt link  334  coupled with both ends of the dancer  320  respectively along the width of the web W and a right link  332 R coupled with the tilt link  334  in order to allow the widthwise end positions of the dancer  320  to be adjusted respectively. One end of the left link  332 L is hinge-coupled with the dancer  320 , and the other end of the left link  332 L is coupled with a piston of a left cylinder  333 L. One end of the tilt link  334  is hinge-coupled with the dancer  320 . One end of the right link  332 R is hinge-coupled with the other end of the tilt link  334 , and the other end of the right link  332 R is coupled with a piston of a right cylinder  333 R. 
         [0050]    For example, supposing the left and right cylinders  333 L and  333 R apply downward force to the web W, the tension of the web W applies upward force to the left and right cylinders  333 L and  333 R in a responsive manner, thereby balancing the forces. It is assumed that the tension on the left edge of the web W remains constant while the tension on the right edge of the web W decreases. In this case, the position of the left edge of the dancer  320  will not change. However, this will collapse the balance between the downward force applied to the right edge of the dancer  320  from the right cylinder  333 R and the upward force applied to the dancer  320  from the tension of the web W, such that the dancer  320  will move downwardly until the forces are balanced again. Consequently, the right end of the dancer  320  will be positioned lower than the left end of the dancer  320 . 
         [0051]      FIG. 16 ,  FIG. 17  and  FIG. 18  illustrate a thirteenth exemplary embodiment of the tension adjustment device according to the present invention. 
         [0052]    As illustrated in  FIG. 16  to  FIG. 18 , left top and bottom cylinders  333 LT and  333 LB and right top and bottom cylinders  333 RT and  333 RB are coupled with both ends of the dancer  320  from above and below, thereby making it possible to more minutely adjust the tension even in the case that there is a widthwise difference in the tension of the web W. 
         [0053]    The tension adjustment device illustrated in  FIG. 16  to  FIG. 18  includes a left top link  332 LT, a left bottom link  332 LB, a tilt link  334 , a right top link  332 RT and a right bottom link  332 RB. 
         [0054]    The left top and bottom links  332 LT and  332 LB are hinge-coupled with one widthwise end (left end) of the dancer  320  along the width of the web W, and are disposed in opposite directions towards both surfaces of the web W. One end of the left top link  332 LT is hinge-coupled with one widthwise end of the dancer  320 , and the other end of the left top link  332 LT is coupled with a piston of the left top cylinder  333 LT. One end of the left bottom link  332 LB is hinge-coupled with one widthwise end of the dancer  320 , and the other end of the left bottom link  332 LB is coupled with the piston of the left bottom cylinder  333 LB. 
         [0055]    The tilt link  334  is hinge-coupled with the other widthwise end of the dancer  320  along the width of the web W. One end of the tilt link  334  is hinge-coupled with the other widthwise end of the dancer  320 . 
         [0056]    The right top and bottom links  332 RT and  332 RB are coupled with the tilt link  334 . One end of the right top link  332 RT is hinge-coupled with the other end of the tilt link  334 , and the other end of the right top link  332 RT is coupled with a piston of the right cylinder  333 RT. One end of the right bottom link  332 RB is hinge-coupled with the other end of the tilt link  334 , and the other end of the right bottom link  332 RB is coupled with a piston of the right cylinder  333 RB. 
         [0057]      FIG. 19  schematically illustrates an exemplary embodiment of a continuous web processing method according to the present invention. 
         [0058]    The present invention provides the continuous web processing method for processing a web W by adjusting the tension of the web W using the above-described tension adjustment device  300 . The continuous web processing method includes an operation of adjusting the tension of the web W using the tension adjustment device  300  and an operation of processing the tension-adjusted web W. The processing operation includes at least one selected from among, but not limited to, operations of shaping, cutting, polishing, printing on, coating, cleaning and examining the web W. The continuous web processing method is undertaken using a roll-to-roll process or a roll-to-sheet process.  FIG. 19  illustrates a continuous cleaning and examining method. Here, the operation of processing the web W refers to operations of cleaning and examining the web W. 
         [0059]    The web W together with a protective film is unwound from the unwinder roll  715 . The protective film is wound on a protective film winding roll  716 . The tension of the web W is adjusted by the tension adjustment device  300 , and the web W is transported by a transportation unit  100 . The web W is subsequently cleaned in a cleaning unit  800 , and is examined in an examining unit  900 . Afterwards, the web W is wound on a winding roll  717 . At this time, a protective film unwound from a protective film unwinding roll  718  is wound together with the web W.