Patent Publication Number: US-2022212415-A1

Title: Web welding system and welding method

Description:
TECHNICAL FIELD 
     The present invention relates to web welding systems and welding methods mainly for wearing articles. 
     BACKGROUND ART 
     A welding system is known in which in order to seal (weld) a plurality of webs for each disposable article unit, a pair of ultrasonic horns and a pair of anvils are provided (patent literatures 1 to 3). 
     In the conventional technique described above, the webs which are overlaid on each other are transported, are passed between the horn of an ultrasonic device and an anvil roller, are intermittently sandwiched between an anvil formed on the outer circumference of the anvil roller and the horn and are intermittently welded together. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: WO 05/005296 A1 (front page) 
     Patent Literature 2: WO 05/080065 A1 (front page) 
     Patent Literature 3: WO 14/077152 A1 (front page) 
     SUMMARY OF INVENTION 
     In the conventional technique described above, since a welding time is sufficiently taken when the webs are welded, the transport speed of the webs is periodically changed such that the transport speed is lowered. 
     However, the transport speed is changed as described above, and thus it is inevitable that the webs flutter or expand and contract. In particular, in the case of wearing articles, the thickness of part of an absorbent core is increased and is uneven, and thus the flutter easily occurs. In a case where the material of the webs is unlikely to be welded, the webs flutter or expand and contract when the speed is changed, with the result that a welding failure easily occurs. 
     Hence, an object of the present invention is to provide a web welding system and a welding method in which a welding failure is unlikely to occur. 
     A web welding system of the present invention includes: a transport device  3  that transports a work W in a state where a plurality of webs of the work W are overlaid on each other; an anvil roller  10  that includes an anvil  11 ,  12  which intermittently makes contact with a first surface W 1  of the work W being transported; an ultrasonic horn  21 ,  22  that is opposite a second surface W 2  of the work W and that cooperates with the anvil  11 ,  12  to apply vibration energy to the work W so as to intermittently weld the plurality of webs; a speed changing device  4  that lowers a transport speed of the work W supplied between the horn  21 ,  22  and the anvil  11 ,  12  when the welding is performed; and a pressing device  5  that presses the first surface W 1  of the work W to the anvil  11 ,  12  when the welding is performed. 
     A web welding method using the welding system described above includes: a step of supplying the work W between the horn  21 ,  22  and the anvil  11 ,  12  while changing the transport speed of the work W with the speed changing device  4 ; a step of welding the plurality of webs between the horn  21 ,  22  and the anvil  11 ,  12  when the transport speed of the work W is lowered and a step of pressing, with the pressing device  5 , the first surface W 1  of the work W to the anvil  11 ,  12  when the welding is performed. 
     According to the present invention, the pressing device presses the work to the anvil, and thus it is possible to decrease the influence of the flutter or the expansion and contraction of the work and thereby to reduce a welding failure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a schematic configuration view showing a welding system when welding is performed according to an embodiment of the present invention and  FIG. 1B  is an enlarged view of an anvil roller; 
         FIG. 2  is a schematic configuration view showing the welding system when the welding is not performed; and 
         FIG. 3  is a schematic front view showing an example of a work before being cut into individual products. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In a preferred system, the pressing device  5  includes a first pressing roller  51  that is arranged on an upstream side in the transport direction of the work W and that makes contact with the second surface W 2  and a second pressing roller  52  that is arranged on a downstream side in the transport direction of the work W and that makes contact with the second surface W 2 , and the horn  21 ,  22  is arranged between the first pressing roller  51  and the second pressing roller  52 . 
     In this case, when the anvil rotates to a position between the first pressing roller and the second pressing roller, the work is pressed to the anvil with the two pressing rollers, and thus the webs are welded, with the horn, between the horn and the anvil. Hence, the work is unlikely to flutter or expand and contract when the welding is performed. 
     In a further preferred system, the anvil  11 ,  12  makes contact with the work W between a first point P 1  where the work W makes contact with the first pressing roller  51  and a second point P 2  where the work W makes contact with the second pressing roller  52  such that the pressing device  5  presses the first surface W 1  of the work W to the anvil  11 ,  12 . 
     In this case, the anvil makes contact with the work between the first point and the second point, and in a state where the anvil is pressed to the work, the horn welds the work between the horn and the anvil. 
     In a preferred system, a pair of the horns  21 ,  22  are provided around the anvil roller  10 , the anvil roller  10  includes a plurality of the anvils  11 ,  12  such that the plurality of the anvils  11 ,  12  correspond to the pair of the horns  21 ,  22 , the transport device  3  further includes a reverse roller R 3  which transports the work W such that the work W welded with one of the horns is welded with the other horn and the system includes a belt B 1  that transports the work W while sandwiching the work W with the reverse roller R 3 . 
     In this case, the belt sandwiches the work with the reverse roller, and thus it is possible to decrease the flutter of the work on the surface of the reverse roller. 
     In a further preferred system, the speed changing device  4  includes a first dancer roller R 1  that receives the work W from the upstream side to supply the work W to the anvil roller  10 , a second dancer roller R 2  that receives the work W from the anvil roller  10  to transport the work W to the downstream side and another belt B 2  (separate from the belt B 1 ) that transports the work W while sandwiching the work W with both the first and second dancer rollers R 1  and R 2 . 
     In this case, the belt sandwiches the work with the first and second dancer rollers R 1  and R 2 , and thus it is possible to decrease the flutter of the work on the surface of the dancer rollers. 
     In a preferred welding method, the pressing device  5  includes a first pressing roller  51  and a second pressing roller  52  that respectively make contact with the work W on upstream and downstream sides of the horn  21 ,  22 , and when the anvil roller  10  rotates and the anvil  11 ,  12  is opposite (faces) the horn  21 ,  22  through the work W, the anvil  11 ,  12  protrudes to the side of the horn beyond the first and second pressing rollers  51  and  52  to apply tension to the work W between the first and second pressing rollers  51  and  52  so as to press the first surface W 1  of the work W to the anvil  11  and  12 . 
     As described above, the anvil makes contact with the work to which the tension is applied between the first and second pressing rollers, with the result that the structure of the pressing device is prevented from being complicated. 
     Any feature illustrated and/or depicted in conjunction with one of the aforementioned aspects or the following embodiments may be used in the same or similar form in one or more of the other aspects or other embodiments, and/or may be used in combination with, or in place of, any feature of the other aspects or embodiments. 
     Embodiments 
     The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative and should not be taken to define the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures. 
     An embodiment of the present invention will be described below with reference to drawings. 
     In the following discussion, an outline of a welding system of the present invention will first be described, and a speed changing device  4  provided in the welding system will then be described. 
     The present system includes: the transport device  3  of  FIG. 1A  that transports a work W like a wearing article including a plurality of webs N shown in  FIG. 3  and overlaid on each other; and a pair of ultrasonic welding devices  1  and  2  that weld the webs N being transported. 
     In  FIG. 1A , the ultrasonic welding devices  1  and  2  include: an anvil roller  10  that includes a pair of anvils  11  and  12 ; first and second ultrasonic horns  21  and  22  that cooperate with the pair of anvils  11  and  12  to apply vibration energy to the work W; and a pair of sonic devices  20  and  20  that generate ultrasonic vibration in the ultrasonic horns  21  and  22 . The anvils  11  and  12  intermittently make contact with the first surface W 1  of the work W. 
     High-frequency mechanical vibration is applied to the horns  21  and  22 , and thus the webs that pass between the horns  21  and  22  and the anvils  11  and  12  are welded together by frictional heat. The horns  21  and  22  are opposite (face) the second surface W 2  of the work W, and cooperate with the anvils  11  and  12  to apply the vibration energy to the work W so as to weld the webs. 
     As the ultrasonic horns  21  and  22 , for example, ultrasonic horns disclosed in JP 10-513128 W may be used. 
     The work W is formed by overlaying a plurality of thermoplastic webs that need to be welded together. The welding regions S of the work W shown in  FIG. 3  and sealed with the sonic devices  20  and  20  are, for example, the end portions of a product like disposable underwear (an example of the wearing article). 
     The pair of anvils  11  and  12  in  FIG. 1B  are provided symmetrically with respect to the axis line (line extending along the rotation center O of the anvil  11 ) of the anvil roller  10 . In other words, the pair of anvils  11  and  12  are provided in the anvil roller  10  with a pitch of 180°. The pair of ultrasonic horns  21  and  22  are arranged such that one of the pair of anvils  11  and  12  can be opposite (face) the first ultrasonic horn  21  and that the other of the pair of anvils  11  and  12  can be simultaneously opposite (face) the second ultrasonic horn  22 . 
     In a state where the pair of anvils  11  and  12  are respectively opposite the first and second ultrasonic horns  21  and  22 , the pair of ultrasonic horns  21  and  22  simultaneously apply the vibration energy to the work W. Hence, the work W (webs) is simultaneously welded at two places. 
     In  FIGS. 1A and 1B , the transport device  3  transports the work W such that the work W passes through a first gap Δ 1  between the anvil roller  10  and the first ultrasonic horn  21  and thereafter passes through a second gap Δ 2  between the anvil roller  10  and the second ultrasonic horn  22 . The transport device  3  includes a reverse roller R 3 , the speed changing device  4  which will be described in detail later and the like. The work W which has passed through the first gap Δ 1  ( FIG. 1B ) moves along the outer circumferential surface of the reverse roller R 3  and is thereafter transported into the second gap Δ 2  ( FIG. 1B ). 
     The speed changing device  4  includes first and second dancer rollers R 1  and R 2  and a drive roller  4 R. The first dancer roller R 1  receives the work W that moves in from the upstream side, and ejects the work W toward the first gap Δ 1  ( FIG. 1B ). The second dancer roller R 2  receives the work W that is ejected from the second gap Δ 2  ( FIG. 1B ), and ejects the work W toward the downstream side. 
     The speed changing device  4  reciprocates (swings) the first and second dancer rollers R 1  and R 2  as indicated by virtual and solid lines. The drive roller R 4  rotates the first and second dancer rollers R 1  and R 2  at the same rotation speed (peripheral speed). 
     On the upstream side of the first dancer roller R 1 , a first guide roller G 1  is rotatably provided. On the downstream side of the second dancer roller R 2 , a second guide roller G 2  is rotatably provided. The first guide roller G 1  guides the work W that moves toward the first dancer roller R 1 . On the other hand, the second guide roller G 2  guides the work W that moves out from the second dancer roller R 2 . In a position above the area between both the dancer rollers R 1  and R 2 , the drive roller R 4  is arranged. The five rollers R 1 , R 2 , Gl, G 2  and R 4  described above are driven by the drive roller R 4  to rotate synchronously through an unillustrated timing belt. 
     A drive device for the five rollers is disclosed in WO 2005/080065 A1, the entire disclosure of which is incorporated herein by reference. 
     The speed changing device  4  transports the work W at high speed and at low speed alternately and repeatedly. In the high-speed transport, the moving speed of the work W between the dancer rollers R 1  and R 2  is higher than the speed V of the work W that moves in the first dancer roller R 1 . On the other hand, in the low-speed transport, the moving speed of the work W between the dancer rollers R 1  and R 2  is lower than the speed V. 
     S p ecifically, in the high-speed transport of  FIG. 2 , both the dancer rollers R 1  and R 2  are moved such that, as indicated by arrows D 1 , the first dancer roller R 1  moves close to the anvil roller  10  and that the second dancer roller R 2  simultaneously moves away from the anvil roller  10 , with the result that the work W is transported at high speed between both the dancer rollers R 1  and R 2 . 
     On the other hand, in the low-speed transport of  FIG. 1A , both the dancer rollers R 1  and R 2  are moved such that, as indicated by arrows D 2 , the first dancer roller R 1  moves away from the anvil roller  10  and that the second dancer roller R 2  simultaneously moves close to the anvil roller  10 , with the result that the work W is transported at low speed between both the dancer rollers R 1  and R 2 . 
     In this way, when the anvils  11  and  12  of  FIG. 1A  are respectively opposite the first and second ultrasonic horns  21  and  22 , control is performed such that the speed of the work W between the first dancer roller R 1  and the second dancer roller R 2  is lower than the speed V of the work W which moves in the first dancer roller R 1 , and the welding is performed by ultrasonic energy. 
     As described above, when the horns  21  and  22  apply the vibration energy to the work W, the speed of the work W passing between the horns  21  and  22  and the anvils  11  and  12  is low, and thus the time during which the vibration energy is received is increased, with the result that energy received by the work W per unit area is increased. Hence, the reliability of the welding is enhanced. 
     The present welding system includes a pressing device  5  that presses the first surface W 1  of the work W to the anvils  11  and  12  when the welding is performed. The pressing device  5  includes: first pressing rollers  51  that are arranged on the upstream side in the transport direction of the work W and that make contact with the second surface W 2 ; and second pressing rollers  52  that are arranged on the downstream side in the transport direction of the work W and that make contact with the second surface W 2 . Between the first pressing rollers  51  and the second pressing rollers  52 , the horns  21  and  22  are arranged. 
     In  FIG. 1B , the anvils  11  and  12  make contact with the work W between first points P 1  where the work W makes contact with the first pressing rollers  51  and second points P 2  where the work W makes contact with the second pressing rollers  52 , and thus the pressing device  5  presses the first surface W 1  of the work W to the anvils  11  and  12 . 
     In  FIG. 1B , as indicated by a chain double-dashed line, the anvils  11  and  12  rotate about the rotation center O. The pressing rollers  51  and  52  are arranged close to the outside of the chain double-dashed line. 
     The present system of  FIG. 1A  further includes a first belt B 1  and a second belt B 2 . The first belt B 1  is an endless belt that is guided by a plurality of guide rollers R, and transports the work W while sandwiching the work W with the reverse roller R 3 . The second belt B 2  is an endless belt that is guided by a plurality of guide rollers R, and transports the work W while sandwiching the work W with the first and second dancer rollers R 1  and R 2 . 
     The control of the present system will then be described. 
     Both the dancer rollers R 1  and R 2  repeatedly reciprocate (swing) in the directions of the arrows D 1  and D 2 , and thus the high-speed transport and the low-speed transport are repeated. 
     In  FIG. 1A , when the anvils  11  and  12  are respectively opposite the first and second ultrasonic horns  21  and  22 , the sonic devices  20  are controlled such that the pair of ultrasonic horns  21  and  22  apply the vibration energy to the work W, and thus the work W is welded. 
     On the other hand, the speeds of the drive roller R 4  and the reverse roller R 3  are changed synchronously such that the peripheral speeds of the drive roller R 4  and the reverse roller R 3  are equal to each other. The speeds of the drive roller R 4  and the anvil roller  10  are periodically changed such that, when the work W is welded, the peripheral speeds of the anvil roller  10  and the drive roller R 4  are equal to each other. In this way, control is performed according to the movements of the dancer rollers R 1  and R 2  such that the peripheral speeds of the drive roller R 4  and the reverse roller R 3 , the peripheral speed of the anvil roller  10  when the work W is welded and the transport speed of the work W between the first dancer roller R 1  and the second dancer roller R 2  are equal to each other. 
     The operation of the present system will then be described. 
     The work W of  FIG. 1A  moves from the first guide roller G 1  along the outer circumferential surface of the first dancer roller R 1  at a substantially constant speed V, passes through the first and second gaps Δ 1  and Δ 2 , moves along the outer circumferential surface of the second dancer roller R 2  and is thereafter transported along the second guide roller G 2  at the substantially constant speed V. The work W between the first dancer roller R 1  and the second dancer roller R 2  is supplied into the gaps Δ 1  and Δ 2  ( FIG. 1B ) between the horns and the anvils while the speed of the work W is being changed with the speed changing device  4 . 
     Specifically, as shown in  FIG. 1A , the first dancer roller R 1  is moved in the direction of the arrow D 2  such that the length of the work W between the first dancer roller R 1  and the first gap Δ 1  ( FIG. 1B ) is increased, and the second dancer roller R 2  is moved in the direction of the arrow D 2  such that the length of the work W between the second dancer roller R 2  and the second gap Δ 2  ( FIG. 1B ) is decreased. In this way, the speed of the work W between the first dancer roller R 1  and the second dancer roller R 2  is lower than the speed V of the work W that moves in the first dancer roller R 1 . 
     When the work W is transported at low speed, the anvils  11  and  12  of the anvil roller  10  are opposite the ultrasonic horns  21  and  22 , the sonic devices  20  are operated and thus the welding regions S of the work W of  FIG. 3  adjacent to each other are simultaneously welded (sealed). 
     As shown in  FIG. 2 , the first dancer roller R 1  is moved in the direction of the arrow D 1  such that the length of the work W between the first dancer roller R 1  and the first gap Δ 1  ( FIG. 1B ) is decreased, and the second dancer roller R 2  is moved in the direction of the arrow D 1  such that the length of the work W between the second dancer roller R 2  and the second gap Δ 2  ( FIG. 1B ) is increased. In this way, the speed of the work W between the first dancer roller R 1  and the second dancer roller R 2  is higher than the speed V of the work W that moves in the first dancer roller R 1 . 
     When the welding of  FIGS. 1A and 1B  is performed, the pressing device  5  presses the first surface W 1  of the work W to the anvils  11  and  12 . 
     Specifically, when the anvil roller  10  rotates and the anvils  11  and  12  are opposite the horns through the work W, the anvils  11  and  12  protrude to the sides of the horns beyond the first and second pressing rollers  51  and  52  to apply tension to the work W between the first pressing rollers  51  and the second pressing rollers  52  so as to press the first surface W 1  of the work W to the anvils  11  and  12 . 
     Hence, in a state where the desired tension is applied to the work W, the webs N ( FIG. 3 ) are welded together. Therefore, in a state where the work W does not flutter or expand and contract, the webs N ( FIG. 3 ) of the work W are welded together, with the result that a welding failure is unlikely to occur. 
     Although as described above, the preferred embodiment has been described with reference to the drawings, a person skilled in the art easily conceives various variations and modifications from the present specification within an obvious range. 
     For example, the reverse roller does not necessarily need to be provided. 
     Furthermore, the reverse roller may be supported by a support means through a means that can finely adjust the position of the axis center. 
     The drive roller R 4  does not need to be in contact with the work W. 
     The dancer rollers may swing not vertically but laterally. 
     Hence, the variations and modifications as described above are interpreted to be within the scope of the present invention defined by the scope of claims. 
     INDUSTRIAL APPLICABILITY 
     The welding system of the present invention can be utilized, for example, not only for the production facilities of disposable wearing articles such as disposable pants, diapers and sanitary items but also for the production facilities of medical wound dressing materials and the like. 
     REFERENCE SIGNS LIST 
       1 ,  2 : first and second ultrasonic welding devices 
       10 : anvil roller 
       11 ,  12 : first and second anvils 
       20 : sonic device 
       21 ,  22 : first and second ultrasonic horns 
       3 : transport device 
       4 : speed changing device 
       51 : first pressing roller 
       52 : second pressing roller 
     B 1 , B 2 : belt 
     O: rotation center 
     P 1 : first point 
     P 2 : second point 
     R 1 : first dancer roller 
     R 2 : second dancer roller 
     R 3 : reverse roller 
     R 4 : drive roller 
     W: work 
     W 1 : first surface 
     W 2 : second surface 
     Δ 1 , Δ 2 : gap