Patent Publication Number: US-2007095482-A1

Title: Label applicator

Description:
FIELD OF INVENTION  
      This invention relates to application of labels, and in particular, to removing adhesive labels from a web.  
     BACKGROUND  
      Adhesive labels are often packaged on long strips, called webs. These webs are generally sold in rolls that are mounted on a labeling machine.  
      In a typical labeling machine, the web is threaded between a feed spool and a take-up spool. The portion of the web wound on the feed spool is laden with adhesive labels. The portion of the web wound around the take-up spool ideally has no labels at all. Between the feed spool and the take-up spool is a label dispenser. In operation, the web travels between the feed spool and the take-up spool. At the label dispenser, labels are peeled off the web and applied to an applicator. In the case of a tamp applicator, the applicator is a tamping member that receives the label and tamps it on a package.  
      A typical label dispenser includes a peel-bar having an edge that contacts the moving web. In operation, the web, laden with labels, approaches the edge on one side of the peel-bar. At the edge, the web executes a turn, which causes a label to be peeled off the web.  
      During the peeling process, a separation line on the label divides the label into two portions: a peeled portion, which is no longer attached to the web, and an unpeeled portion, which remains attached to the web. The separation line begins at the leading edge of the label and moves progressively backward, toward the trailing edge of the label. As it does so, the peeled portion lengthens and the unpeeled portion of the label shortens. When the separation line reaches the trailing edge, the peeling is complete.  
      When the separation line meets the trailing edge of the label, the last line of adhesive often stays stuck to the web. This results in labels that remain on the web, held only by the last line of adhesive, as the web moves away from the peel-bar. Consequently, products that should have been labeled remain unlabeled. In addition, the presence of labels dangling from the web with their sticky sides exposed increases the likelihood of label jams in the dispenser.  
     SUMMARY  
      In one aspect, the invention includes an apparatus having a tamp applicator having a face plate for receiving a label moving in a first direction; and a barrier on the face plate to limit motion of the label along the first direction.  
      Among the embodiments of the apparatus are those having channels on the face plate, and a manifold for distributing moving air among the channels. Such a manifold can be configured to direct moving air in the first direction, or to direct moving air in a direction opposite to the first direction.  
      The barrier can take a variety of forms. For example, some embodiments have a lip as a barrier. Such a lip can extend across the face plate. The barrier can be disposed at a variety of locations. Some embodiments feature a barrier that is disposed to engage the label while a portion of the label is attached to a web.  
      The height of the lip can also vary. In some embodiments, the lip has a height that is less than the thickness of the label; in others, the lip has a height between 60% and 90% of the thickness of the label.  
      Other embodiments of the apparatus include those having a tamping arm coupled to the tamp applicator. The tamping arm causes the tamp applicator to move between a first position, in which the tamp applicator is disposed to receive the label, and a second position, in which the tamp applicator is disposed to apply the label to a substrate.  
      In another aspect, the invention includes a labeling machine having a label applicator in which a tamp applicator has: a face plate for receiving a label moving in a first direction; and a barrier on the face plate to limit motion of the label along the first direction.  
      Another aspect of the invention features an apparatus having a tamp applicator having a face plate for receiving a label moving in a first direction; and means for limiting motion of the label along the first direction.  
      Yet another aspect of the invention includes a method of removing an adhesive label from a web. The method includes receiving a leading portion of a label, the label having a trailing portion adhered to a web; the leading portion being free of the web and moving in a first direction; and limiting motion of the leading portion along the first direction, thereby causing application of a force tending to free the trailing portion from the web.  
      Among the practices of this method are those in which a partial vacuum is applied to urge the label in a direction having a component perpendicular to the first direction. Such a partial vacuum can be applied, for example, by directing moving air along one face of the label.  
      In other practices, limiting motion of the leading portion includes providing a barrier to engage a leading edge of the label. Providing such a barrier can include selecting a height of the barrier to be less than the thickness of the label.  
      Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.  
      Other features and advantages of the invention will be apparent from the following detailed description, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagram that shows labels adhering to a web;  
       FIG. 2  is a diagram that shows a label being peeled off a web;  
       FIG. 3  is a diagram that shows a tamp applicator receiving a label;  
       FIG. 4  is a diagram that shows the tamp applicator of  FIG. 3  dispensing a label; and  
       FIG. 5  is a diagram that shows the air-distribution system of the tamp applicator of  FIG. 3 . 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  shows labels  10  adhering to a web  11 . The labels  10  have a width, w, that is much greater than their length,  1 . Such labels  10  are commonly used for RFID (“Radio Frequency Identification) tags because the antennas  12  used in such tags are often much larger than the processing components of the RFID chip  14 . One label that incorporates an RFID chip is 12.7 mm in width and 101.6 mm in length. Another such label is 12.7 mm in width and 152.4 mm in length. Other labels include those that are used in connection with the ALIEN I (TM) tag (13 mm wide and 100 mm long), the ALIEN SQUIGGLE (TM) Tag (16 mm wide and 156 mm long), and the ALIEN D (TM) tag (16 mm side and 165 mm long), all of which are available from Alien Technology of Morgan Hill, California.  
      In an effort to maximize the number of labels  10  per unit length of web  11 , these labels  10  are often placed on the web  11  with their shorter dimension extending parallel to the web&#39;s direction of motion. This preferred orientation causes difficulty in peeling the label  10  off the web  11 .  
       FIG. 2  shows a label  10  in the process of being peeled off the web  11 . A leading portion  16  of the label  10 , extending between a leading edge  18  and a separation line  20 , is already off the web  11  and presented to an applicator  22 . A trailing portion  24  of the label  10 , extending from the separation line  20  to a trailing edge  26 , remains on the web  11 . In some embodiments, a partial vacuum draws the label towards the applicator  22 .  
      As shown in  FIG. 2 , the leading portion  16  of the label  10  functions as a moment arm for transmitting a torque about the separation line  20 . This torque assists in peeling the trailing portion  24  of the label  10 . As the separation line  20  moves backward, the leading portion  16  becomes progressively longer. Thus, the torque at the separation line  20  becomes larger. The torque is augmented by the vacuum in the applicator  22 .  
      In the case of a label  10  having an aspect ratio and orientation as shown in  FIG. 1 , the leading portion  16  of the label  10  never becomes very long. As a result, it is sometimes difficult to generate sufficient torque to completely peel the label  10  off the web  11 . This difficulty is further exacerbated in labels that hold RFID tags because such labels tend to be relatively stiff.  
       FIG. 3  shows an applicator  28  in which a tamp applicator  30  is disposed to receive a label  10  that is peeled from a web  11  as the web  11  executes a hairpin turn around a peel bar  32 . The tamp applicator  30  is rotatably coupled to a tamping arm  34  at a joint  36 . The tamp applicator  30  moves between a receiving position, shown in  FIG. 3 , in which it receives a label  10 , and a tamping position, shown in  FIG. 4 , in which it is ready to apply the label  10  to a package  38 . The tamping arm  34  translates and rotates the tamp applicator  30  between the receiving position and the tamping position.  
      The tamp applicator  30  has a face plate  39  for supporting the label  10 .The face plate  39  has a transversely-extending front edge  40  and a transversely-extending back edge  42 . Extending parallel to the front edge  40  is a barrier  44  that catches the leading edge  18  of the label  10 .  
      The tamp applicator  30  also includes a vacuum system  46 , best seen in  FIG. 5 , having a transversely extending manifold  48  that directs moving air through channels  50 . In  FIG. 5 , the channels  50  are shown as extending between the front edge  40  and the back edge  42  of the face plate  39 . However, the channels  50  can be oriented in any direction, including transversely across the face plate  39 , or at a diagonal. Air moving along these channels  50  creates a partial vacuum that holds the label  10  on the face plate  39 . The channels  50  further include an angled portion  51  to direct air away from the label  10 , thereby preventing the label  10  from fluttering while it is on the face plate  39 .  
      In operation, as the label  10  peels off the web  11 , the leading edge  18  of the label  10  engages the barrier  44 , as shown in  FIG. 3 . The barrier  44  resists further forward motion of the label  10 . The leading portion  16  of the label  10  transmits the resistive force provided by the barrier  44  back to the separation line  20 . This resistive force thus results in a shear force that assists in moving the separation line  20  back toward the trailing edge  26  of the label  10 , thereby enhancing the likelihood that the label  10  will be peeled off the web  11  successfully. In addition, air moving along the channels  50  exerts a negative pressure that tends to suck the label  10  toward the face plate  39 . This negative pressure helps prevent the label  10  from bowing outward, away from the face plate  39 .  
      As the web  11  continues to drive the trailing edge of the label  10  forward, the shear force increases further. In effect, the label  10  becomes a leaf spring exerting the shear force. Eventually, the shear force overcomes the force of the adhesive holding the label  10  to the web  11 , and the label  10  peels off the web  11  completely. The negative pressure then sucks the label  10  flat against the face plate.  
      Once the label  10  is on the face plate  39 , the tamping arm  34  swivels the tamp applicator  30  from the first position, shown in  FIG. 3 , to the second position, shown in  FIG. 4 . The tamping arm  34  then translates the tamp applicator  30  toward the package  38  until the adhesive face of the label  10  contacts the package  38 . The tamping arm  34  then withdraws the tamp applicator  30 , leaving behind the label  10  on the package  38 , and moves the tamp applicator  30  back into the first position to receive the next label  10 .  
      In alternative embodiments, the tamp applicator  30  is already oriented correctly for placement of the label on the package  38 . In such embodiments, the tamping arm  34  need not swivel the tamp applicator  30 , and the tamp applicator  30  need only be translated into position.  
      The barrier  44  extends outwardly from the face plate  39  to an extent that is less than the thickness of the label  10 . If the barrier  44  fails to extend outward sufficiently, it will fail to engage the label  10  sufficiently to block forward motion of the label  10 . Instead, the label  10  will simply slide over the barrier  44 . If, on the other hand, the barrier  44  is taller than the label  10  is thick, then the tamping arm  34  will be unable to place the label  10  in contact with the package  38 . Suitable ratios between the thickness of the label  10  and the height of the barrier  44  range between 60% and 90%. For a label  10  that is 0.006 inches thick, a suitable height of the barrier  44  is 0.005 inches.  
      As shown, the barrier  44  is a continuous lip extending all the way across the face plate  39 . However, this need not be the case. The barrier  44  can be a discontinuous lip, or a lip that extends only partway across the face plate  39 . Or, the barrier  44  can be a pair of pins or other obstructions. The barrier  44  need not be permanently in place. For example, the barrier  44  can be made retractable. In such a case, the barrier  44  height can be made equal to or greater than the thickness of the label  10  since the barrier  44  could then be retracted to a suitable height, or retracted all the way, just before the label  10  is applied to the package  38 .  
      Also as shown, the cross-section of the barrier  44  features a vertical wall. However, the cross-section of the barrier  44  can be varied in response to variations in the profile of the label  10 . The cross-section can also be a line that meets the face plate  39  at an angle other than ninety degrees, or the cross-section can form a curve shaped to engage the label  10 .  
      In other embodiments, the barrier  44  need not extend upwards at all. The barrier  44  may be, for example, a portion of the face plate  39  having a coefficient of friction that is sufficient to engage the label  10  and to resist forward motion thereof. Or, the barrier  44  may be a portion of the face plate  39  having an adhesive layer that likewise engages the label  10  and resists forward motion thereof.  
      Other embodiments of the barrier  44  are those in which an electrostatic charge is applied to the label  10  and an opposed electrostatic charge is applied at the front edge of the face plate  39 , thereby causing an electrostatic force that resists forward movement of the label  10 .  
      In yet other embodiments, the channels can be constricted toward the front edge of the face plate  39 , so that the air velocity, and hence the suction force, is greater at the front edge. In that case, the suction force is made strong enough to resist forward motion of the label  10 . In such a case, the air velocity can be varied so that the suction force is reduced when the label  10  is being tamped onto the package  38  and greatest when the label  10  is being peeled off the web.  
      As shown in  FIG. 3 , the manifold  48  is under the back edge  42  of the tamp applicator  30 , so that air flows in a direction from the back edge  42  toward the front edge  40 . However, the manifold  48  can also be under the front edge  40  so that air flows in the opposite direction. Or, the vacuum system  46  can be one in which channels  50  extend transversely across the tamp applicator  30 , or in a direction that has both a transverse and longitudinal direction relative to the tamp applicator  30 .  
      The velocity of air in the channels  50  depends on such factors as the size and weight of the label  10 , the stiffness of the label  10 , and the strength of the adhesive on the label  10 . The velocity is selected to be high enough to secure the label  10  against the tamp applicator  30 , but not so high that the label  10  is sucked into the channels  50  and deformed.  
      It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.