Abstract:
An improved web accumulator with two arms where at least one arm is a swinging dancer arm and at least one arm is attached to a sliding carriage. Each arm has a set of rollers attached. A web is threaded alternately between the two sets of rollers. The arms are mechanically connected to move simultaneously towards or away from each other. The arms are initially position at their maximum separation to accumulate a maximum length of web. When web infeed is interrupted while web outfeed or draw persists, the arms are first rotated in towards each other to pay out the stored length of web. As the demand persists and the dancer arm is rotated beyond some predefined position, the sliding carriage begins to slide to a least storage position. As web infeed returns to normal operational speeds, the dancer arm and the sliding carriage are returned to their original position to again accumulate a maximum amount of web.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/563,840, filed 20 Apr. 2004, and entitled “Method of Increasing Web Storage in a Dancer.” 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention disclosed herein relates to a method for increasing the amount of web storage available from a web accumulation dancer system. The invention pertains to an accumulator for accumulating a substantial length of a running web such that if the infeed to the accumulator is stopped or slowed for a short interval the web in storage is paid out continuously to a web-utilizing device so that the device has a constant web supply and thus need not be slowed or stopped. Increased storage is an imperative for successful operation of zero speed splicing at very high machine speeds.  
         [0003]     A common use of a web accumulator is where a web is fed from a primary supply wheel and it is necessary to splice the leading edge of the web from a standby supply wheel to the trailing edge of the web from the primary supply wheel in a manner that will not cause interruption of the web supply to a web consuming or utilizing device.  
         [0004]     In one known type of accumulator, the swinging dancer arm type, there is a set of spaced apart rollers on a swingable dancer arm cooperating with another set of rollers on an arm that may be stationary or swingable. A web is looped back and forth between the sets of rollers on opposed arms in a serpentine fashion. When the swingable arm is swung away from the other arm a substantial length of web is accumulated. During normal running of the web the arms will be urged to their maximum practical separation from each other to accumulate the maximum length of web. If the infeed web is slowed or stopped for a short time the tension in the web urges the arms to the minimum separation position in order to make the accumulated web available to the machine. After infeed to the accumulator is resumed the arms separate again and return to their original position to accumulate and store another length of web.  
         [0005]     In another known type of accumulator, the linear sliding carriage type, there is a set of rollers mounted on a movable carriage which can run linearly toward or away from a set of corresponding rollers which may either be stationary or similarly slidably mounted. During normal operation of the accumulator, the two sets of rollers will be slid to their maximum practical separation to accumulate the maximum amount of web. If the infeed supply to the web accumulator is slowed or stopped, the rollers will be slid toward each other to allow the stored web to be paid out. As the web infeed is returned to regular operational speed the movable rollers slide back toward the original position to accumulate another length of web.  
         [0006]     It is well known in the art that the swinging arm dancer type of web accumulator first discussed is efficient in that the friction losses to the web are low. However, the dancer type of accumulator does not store a sufficient length of web. Alternatively, the linear sliding carriage type of accumulator allows more web to be accumulated; however, more frictional losses occur.  
         [0007]     The consequences of friction and inertia may be appreciated when it is realized that the web may be running at a very high speed when suddenly, for some reason, such as when making a splice, the infeeding web is stopped or decelerated. This change in web motion will result in a reaction by the components of the accumulator. Most notable of these reactions is the motion imparted to the movable assembly of the accumulator. After the web is slowed or stopped, the web at the infeed can only accelerate as fast as the rollers can accelerate. The force to accelerate the rollers is provided by tension in the web. Minimizing the number of rollers and minimizing the inertia of each roller minimizes the necessary web tension.  
         [0008]     Minimization and control of the inertia and friction associated with this reaction is therefore an important desired attribute of such accumulators. There is an important need for a web accumulator which provides the benefits of low friction and minimized inertia, allowing it to handle the most delicate of webs at high speeds without breakage or loss of control.  
         [0009]     The invention disclosed herein combines a swinging arm dancer with a linear slide. Thus the invention disclosed herein has the advantage of web storage capability substantially equal to that of a linear accumulation system but with minimized frictional losses.  
       SUMMARY OF THE INVENTION  
       [0010]     The new arrangement combines the best features of both previously known accumulators to gain the advantages of both systems while eliminating the disadvantages of each. The new web accumulator achieves a large amount of web storage for the amount of rollers it utilizes.  
         [0011]     In general terms, the preferred new web accumulator includes arms, each arm has a set of rollers attached. A web is threaded alternately between the two sets of rollers. The arms are mechanically connected to move simultaneously towards or away from each other. The arms are initially position at their maximum separation to accumulate a maximum length of web. When web infeed is interrupted while web outfeed or draw persists, the arms are first rotated in towards each other to pay out the stored length of web. As the demand persists and the dancer arm is rotated beyond some predefined position, the sliding carriage begins to slide to a least storage position. As web infeed returns to normal operational speeds, the dancer arm and the sliding carriage are returned to their original position to again accumulate a maximum amount of web.  
         [0012]     There are several possible variations to this system, such as vertical or horizontal orientation, one or more swinging dancer arms, and either the dancer arm or the linear arm can be sliding. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a front elevational view of the preferred embodiment of the web accumulator.  
         [0014]      FIG. 2  is a side elevational view of the accumulator of  FIG. 1 .  
         [0015]      FIG. 3  is a simplified front elevational view of the preferred embodiment of the accumulator of the present invention with its roller carrying arms in the position in which the maximum length of web is accumulated.  
         [0016]      FIG. 4  is a similar to  FIG. 3  except that the dancer arms of the accumulator are rotating toward each other as would be the case when infeed of the web is stopped and the length of web that is stored in the accumulator is being paid out.  
         [0017]      FIG. 5  is similar to  FIG. 4  except that the dancer arms of the accumulator have begun to slide toward each other to further pay out the stored web material.  
         [0018]      FIG. 6  is similar to  FIG. 5  except that the dancer arms of the accumulator have slid to the least storage position.  
         [0019]      FIG. 7  is a simplified front elevational view of an alternate embodiment of the accumulator of the present invention with its roller carrying arms in the position in which the maximum length of web is accumulated.  
         [0020]      FIG. 8  is similar to  FIG. 7  except that the swinging dancer arm of the accumulator is rotating toward the nonrotating linear arm as would be the case when infeed of the web is stopped and the length of web which is stored in the accumulator is being paid out.  
         [0021]      FIG. 9  is similar to  FIG. 8  except that the nonrotating linear arm has begun to slide toward the rotating arm to further pay out the stored web material.  
         [0022]      FIG. 10  is similar to  FIG. 9  except that the arms of the accumulator are in the least storage position.  
         [0023]      FIG. 11  is a front elevational view of an alternate embodiment of the web accumulator.  
         [0024]      FIG. 12  is simplified front elevational view of the accumulator of  FIG. 11  with its roller carrying dancer arms in the position in which the maximum length of web is accumulated.  
         [0025]      FIG. 13  is a similar to  FIG. 12  except that the dancer arms of the accumulator are rotating toward each other as would be the case when infeed of the web is stopped and the length of web that is stored in the accumulator is being paid out.  
         [0026]      FIG. 14  is similar to  FIG. 13  except that the dancer arms of the accumulator have begun to slide toward each other to further pay out the stored web material.  
         [0027]      FIG. 15  is similar to  FIG. 14  except that the dancer arms of the accumulator have slid to the least storage position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention.  
         [0029]      FIG. 1  illustrates the preferred embodiment of the new web accumulator  20 . The accumulator  20  consists of a first swinging dancer arm  22  rotatably mounted to a first carriage  24 . First dancer arm  22  rotates about axle shaft  26 . A first pneumatic actuator  28  is attached to both first carriage  24  and first dancer arm  22  such that the actuator  28  will function to rotate the dancer arm  22  about axle shaft  26 . Dancer arm  22  supports a first set of web accumulator rollers  30  which are individually numbered  30 A- 30 F, inclusive (see, e.g.,  FIG. 3 .) The web accumulation rollers  30 A- 30 F, inclusive, are rotatably mounted on the dancer arm  22 . The carriage  24  is slidably mounted on an upper track  32  and a lower track  34 .  
         [0030]     On the opposite end of the tracks  32  and  34  is a second swinging dancer arm  36  which is preferably identical to first swinging dancer arm  22 , but rotated 180 degrees from the first swinging dancer arm  22 . Second dancer arm  36  is rotatably mounted to a second carriage  38  for rotation about second axle shaft  40 . A second pneumatic actuator is attached to the second dancer arm  36  and the second carriage  38  to facilitate rotation of the second dancer arm  36  about the second axle shaft  40 . The second carriage  38  is slidably mounted to the upper track  32  and the lower track  34 . A second set of web accumulator rollers  44  which are individually numbered as  44 A- 44 E (see  FIG. 2 ), inclusive are rotatably mounted on the second dancer arm  36 .  
         [0031]     The drive system includes two idler arms  46  and  48  with flexible mechanical linkage  50 . In the preferred embodiment of this invention, the flexible mechanical linkage is a toothed belt. Slidable carriages  24  and  38  are affixed to the belt such that they will not move independently of each other and can only move simultaneously in opposite directions. Carriages  24  and  38  are attached to the toothed belt by clamps  52  and  54 , respectively. The drive system is driven by servomotor  56 .  
         [0032]     It will be noted that in the illustrated embodiment the roller set  30  includes six (6) individual rollers and the roller set  44  includes five (5) rollers. This number can be varied using either a lesser or greater number of rollers as selected for a particular application. However, it will be obvious to one of skill in the art that in order to loop the web between the arms and practice the invention as described herein, the first roller set  30  should include at least two individual rollers and the second roller set  44  should include at least one individual roller. The sets of rollers  30  and  44  are common in the art and therefore are of known configuration.  
         [0033]     In  FIG. 1  the accumulator  20  is in its maximum storage position as would be the case when the web  60  is being drawn out of the accumulator  20  and is being fed into the accumulator  20  at the same rate. The dancer arms  22  and  36  are swung apart as far as is practical to store the maximum amount of web  60  in the form of loops running back and forth between the dancer arms  22  and  36 .  
         [0034]     The web  60  is fed into the web accumulator  20 . The web  60  first passes around an idler roll assembly  58  which is mounted on the second carriage  38 . The web  60  then passes around the first roller  30 A of roller set  30  mounted on first dancer arm  22  and next around the first roller  44 A of the roller set  44  mounted on second dancer arm  36 . The web  60  continues to alternate between the consecutive rollers of roller set  30  and roller set  44  until the web  60  has passed over all the rollers. The web  60  then exits the accumulator  20  and is fed to a web utilization device (not shown).  
         [0035]      FIG. 2  is a side elevation view of the accumulator  20  of  FIG. 1 . This view shows how the individual rollers  44 A- 44 E of roller set  44  are rotationally mounted to dancer arm  36 . This view also shows how the dancer arm  36  is attached to the second axle shaft  40  and to the second actuator  42 . Servomotor  56  is shown with idler arm  48  shown in phantom lines.  
         [0036]     Referring now to  FIGS. 3, 4 ,  5 , and  6 , the dancer arms  22  and  36  are shown rotating and driven towards each other to pay out accumulated web  60  to the outfeed when infeed of web  60  is stopped for a short interval.  FIG. 3  shows the web accumulator  20  in the maximum storage position.  FIG. 4  shows the dancer arms  22  and  26  as they are swinging towards each other. The dancer arms  22  and  36  swing towards each other until some specified point when, as shown in  FIG. 5 , the carriages  24  and  38  on which the dancer arms  22  and  36  are mounted begin to slide toward each other to further continue pay out.  FIG. 6  shows the web accumulator  20  in its least storage position, which is the position at which the dancer arms  22  and  26  are the closest.  
         [0037]     More specifically, the control of the sliding carriages  24  and  38  is dependent on the displacement of the dancer arms  22  and  36 . As the web infeed is slowed or stopped, the tension due to drawing the web  60  from the outfeed end of the web accumulator  20  causes the dancer arms  22  and  36  to move towards the less storage position while the length of web  60  in storage is paid out. The web tension causes the dancer arms  22  and  36  to begin to move. However, the actuators  28  and  42  help drive the swinging dancer arms  22  and  36  to overcome the inertia and friction losses of the roller sets  30  and  44  and dancer arms  22  and  36 . If the dancer arms  22  and  36  and roller sets  30  and  44  had no inertia or frictional losses, the force applied to the dancer arms  22  and  36  by the web tension forces would be sufficient to rotate the dancer arms  22  and  36  to the appropriate positions to pay out the stored web. However, because friction and inertia are a factor, the actuators  28  and  42  must drive the rotating dancer arms  22  and  36  to overcome the losses from friction and inertia.  
         [0038]     When the dancer arms  22  and  36  reach some predetermined position, the carriage slide drive  56  is commanded to move the carriages  24  and  38  towards each other. Under normal circumstances the carriages  24  and  38  maintain their preset position. In this manner nominal changes in dancer arm  22  and  36  positions are ignored.  
         [0039]     As discussed above, the carriages  24  and  38  are mechanically coupled to each other through the drive belt  50  such that they move away from or towards each other synchronously. The velocity of the carriages  24  and  38  is proportional to the rate of displacement of the dancer arms  22  and  36 . This allows the system to pay out web  60  such that the web utilizing device is not slowed or stopped. The servomotor  56  is given the command to move the sliding carriages  24  and  38  to the least storage position at a velocity proportional to the displacement error of the dancer arm  22  and  36  position.  
         [0040]     As the displacement error is nullified, the carriage slide drive  56  is slowed to a stop even if it has not reached its final commanded position. If the error goes negative, the carriage slide drive  56  is commanded to return the sliding carriages  24  and  38  to the preset position at a velocity proportional to the dancer arm  22  and  36  error.  
         [0041]      FIGS. 7, 8 ,  9 , and  10  depict the operation of an alternate embodiment of the web accumulator of the present invention. The alternate embodiment shown in  FIG. 7  consists of a first linear arm  122  with a set of rollers  130  rotatably mounted thereon. The linear arm  122  is nonrotatably attached to a carriage  124 . The carriage  124  is slidably mounted on a set of tracks (not shown). The carriage  124  is mounted in a known fashion, as described regarding the preferred embodiment above. At the other side of the web accumulator  120  of  FIG. 7  is a swinging dancer arm  136  mounted to a plate  138 . The dancer arm  136  has a set of rollers  144  rotatably attached thereon.  
         [0042]      FIG. 7  shows this alternate embodiment of the accumulator  120  in its maximum web storage position. When the infeed to the accumulator stops or slows, the dancer arm  136  swings toward the linear arm as shown in  FIG. 8 . When the dancer arm  136  rotates past some predetermined point, the carriage  124  upon which linear arm  122  is mounted begins to slide toward dancer arm  136  as can be seen in  FIG. 9 .  FIG. 10  shows this alternate embodiment of the accumulator  120  in its least storage position.  
         [0043]     Another alternate embodiment of the invention (not shown) has one swinging dancer arm and one linear arm, as described above in  FIG. 7 . However, in this embodiment the swinging dancer arm is slidably mounted on tracks while the linear arm is stationary. When the web infeed slows or stops, the web will pull the swinging dancer arm toward the stationary linear arm. At some predetermined point the dancer arm will be slid toward the stationary linear arm to pay out the remaining accumulated web.  
         [0044]      FIGS. 11-15  illustrate yet another alternate embodiment of the web accumulator  220  of the present invention. This embodiment is similar to the preferred embodiment of the invention, however in this embodiment the first swinging dancer arm  222  and the second swinging dancer arm  236  are mirror images of each other. As shown in  FIG. 11 , the web accumulator  220  consists of a first swinging dancer arm  222  rotatably mounted to a first carriage  224  and a second swinging dancer arm  236  rotatably mounted to a second carriage  238 . The first and second carriages  224 , 238  are slidably attached to an upper track  232  and a lower track  234 . The swinging dancer arms  222 , 236  and carriages  224 , 238  operate in the manner as described above regarding the preferred embodiment above.  
         [0045]      FIG. 12  shows this alternate embodiment of the web accumulator  220  in its maximum web storage position. When the infeed to the accumulator  220  slows or stops, the dancer arms  222 , 236  swing toward each other as shown in  FIG. 13 . When the dancer arms  222 , 236  rotate past some predetermined point, the first and second carriages  224 , 238  begin to slide towards each other as seen in  FIG. 14 .  FIG. 15  shows this alternate embodiment of the web accumulator  220  in its least storage position.  
         [0046]     The embodiments described above, and depicted in the  FIGS. 1-15  disclose a web accumulator with a horizontal orientation. That is, the carriages slide on tracks in a horizontal direction. However, it is within the purview of the invention to utilize the web accumulator, as disclosed above, with a vertical orientation.  
         [0047]     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention.