Patent Publication Number: US-2022227068-A1

Title: Apparatus and method for securing a zipper closure to polymeric film

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. application Ser. No. 16/252,070, filed Jan. 18, 2019, the complete disclosure as filed being incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a method and apparatus for securing a zipper closure to polymeric film. More specifically, this disclosure relates to an apparatus and method for securing the zipper closure to the film using minimal tension. 
     BACKGROUND 
     U.S. Pat. No. 5,906,438, incorporated herein by reference, describes a flexible pouch-type bag (package) having a recloseable closure and a method of making it. In many typical recloseable bags, the zipper closure is pre-made by an extrusion process and then secured to a bag film. The zipper closure can be a “press to close” type of closure having a protruding male member that is received by a female groove. These are known as the zipper interlocking members. Other types of closures can also be used, including, e.g., closures having slider devices. 
     The zipper closures are pre-made into a continuous strip and stored by coiling around a roll. The packages are made by feeding a continuous web or sheet of polymeric film from a roll and folded so that half the sheet forms a front panel and the other half forms a rear panel. The continuous strip of zipper closure is fed between the panels and then bonded, typically by heat, to the opposing panels. Side seals are formed by heat between the opposing panels transverse to the direction of the zipper closure. The packages are separated along parting lines by a cutting process along the side seals. 
     In existing technologies, a dancer mechanism is used that has only a crude control of the tension on the strip of zipper closure. This can result in packages in which the film is wrinkled or deformed. Improvements are desirable. 
     SUMMARY 
     In one aspect, a method of securing a zipper closure to polymeric film using minimal tension on the zipper closure is provided. The method includes paying out a continuous strip of plastic zipper closure from a roll of zipper closure; paying out polymeric film from a film roll, the polymeric film having periodic eyemarks thereon; passing the strip of zipper closure through a tension control mechanism; passing the strip of zipper closure through a first tension control loop; advancing the film toward a sealing station and past an eyemark detection to detect an eyemark on the film; after detection of the eyemark on the film, punching a hole into the strip of zipper closure upon detection of the eyemark on the film; passing the strip of zipper closure with a punched hole through a second tension loop; applying the strip of zipper closure to the sealing station while simultaneously supplying the film to the sealing station at the same speed as the strip of zipper closure; aligning the hole in the strip of zipper closure with the eyemark on the film; and sealing the strip of zipper closure to the film. 
     In some embodiments, the step of sealing includes sandwiching the strip of zipper closure between two walls of the film and using heated sealing bars to transfer heat to the strip of zipper closure and the film. 
     The step of sealing can include using three sets of opposing sealing bars. 
     In some implementations, the step of sealing includes using opposing sealing bars, with a first of the opposing sealing bars controlling sealing pressure and a second of the opposing sealing bars controlling distance between the sealing bars. 
     In some methods, there are steps of detecting a position of the eyemark; detecting a position of the hole; comparing a distance between the detected eyemark and the detected hole to a predetermined target value; and if distance is not equal to the target value, adjusting a length of an index distance so that the distance becomes equal to the target value. 
     In some methods, the step of passing the strip of zipper closure through a first tension control loop includes threading the strip of zipper closure under a weighted disk movable up and down by gravity to provide constant tension to the strip of zipper closure. 
     In some methods, the step of passing the strip of zipper closure through a second tension loop includes threading the strip of zipper closure under a weighted disk movable up and down by gravity to provide constant tension to the strip of zipper closure. 
     The method can include, after the step of detecting an eyemark on the film, a step of folding the film. 
     The step of sealing can include using multiple sets of opposing guide rollers to guide the position of the strip of zipper closure relative to the film. 
     In a further aspect, an apparatus for securing a zipper closure to polymeric film using minimal tension on the zipper closure is provided. The apparatus includes a tension control mechanism to provide at least some tension to a strip of zipper closure. A first tension control loop is downstream of the dancer mechanism. An eyemark detector is positioned to detect an eyemark on the film. A hole punch is downstream of the first tension control loop and programmed to punch a hole in a strip of zipper closure upon detection of an eyemark on the film. A second tension control loop is downstream of the hole punch. A sealing station is downstream of the second control loop and of the eyemark detector and constructed and arranged to seal a strip of zipper closure to the film. 
     In one or more embodiments, the first tension control loop includes a weighted disk movable up and down by gravity. 
     In some embodiments, the second control loop can include a weighted disk movable up and down by gravity. 
     The apparatus can further include an aperture detector downstream of the second control loop and upstream of the sealing station. The apparatus can also include a controller to compare a distance between the detected eyemark and the detected hole. 
     In some embodiments, the sealing station includes at least a first set of opposing sealing bars, with a first of the opposing sealing bars controlling sealing pressure and a second of the opposing sealing bars controlling distance between the sealing bars. 
     The sealing station can include three sets of opposing sealing bars, in some embodiments. 
     In a further aspect, a system for sealing a zipper to a film is provided. The system includes: a zipper roll station and a film roll station from which the zipper and film are paid out, respectively; a dancer mechanism for tensioning zipper from the zipper roll station; a minimal tension loop and a nip; an earmark detector, a punch, and an aperture detector; a sealing station; and a controller for receiving signals from the earmark detector and aperture detector and transmitting signals to the nip. The nip receives instructions from the controller and operates to feed zipper to the minimal tension control loop so that the nip and minimal tension control loop operate in an index and dwell mode such that the zipper and film are fed to the sealing station at the same speed, and the zipper tension upon entering the sealing station is between 0.05 lbs and 0.7 lbs. 
     In some systems, the zipper tension, upon entering the sealing station, is less than 0.2 lbs. 
     In some embodiments, the zipper tension, upon entering the sealing station, is about 0.1 lbs. 
     A variety of examples of desirable product features or methods are set forth in the description that follows, and in part, will be apparent from the description, or may be learned by practicing various aspects of this disclosure. The aspects of this disclosure may relate to individual features, as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are explanatory only, and are not restrictive of the claimed inventions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an apparatus and process for securing a zipper closure to polymeric film; and 
         FIG. 2  is a front view of a zipper closure with periodic holes, used in the process depicted in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     A method and apparatus are described below, which results in improvements over the prior art. For example, the aesthetics of the packages, or bags, are improved, as the polymeric film does not wrinkle or deform. The zipper closure has a periodic mass of material removed from it, which needs to be aligned with eyemarks on the film indicating the position of the parting lines of the bags. The mass of material removed corresponds to the interlocking elements of the press-to-close zipper. The interlocking elements are much thicker than the rest of the zipper flange. In prior art processes, when the side seals of the bags are made, these thick interlocking members are flattened out by the sealing bars, and this delays the sealing process. By punching out the interlocking members, the sealing time is reduced. The method and apparatus described below ensures precise alignment of the removed mass of material in the zipper closure with the eyemarks, while maintaining the same minimal tension in the zipper closure and bag film to result in advantages. Other advantages that result include reducing instances of overheating or underheating film and a zipper closure, when the zipper closure is sealed to the film. This advantage is achieved by ensuring that the sealing perimeters, including pressure, sealing time, and the gap between opposing sealing bars, are controlled. 
     Reference is made to  FIG. 1 .  FIG. 1  shows an apparatus  110  for securing a zipper closure  4  to polymeric film  3 . 
     A roll  6  having a continuous strip of the plastic zipper closure  4  coiled therearound is provided. The method includes a step of paying out the continuous strip of zipper closure  4  from the roll  6  and passing the strip of zipper closure  4  through a tension control mechanism, embodied herein as a dancer mechanism  80 . 
     The dancer mechanism  80  provides at least some tension to the strip of zipper closure  4 . The dancer mechanism  80  includes a plurality of guiding rollers  31 ,  32 ,  33 ,  34 ,  35  and  36 . The guiding mechanism  80  further includes a carriage bar  37  and carriage guide  38 . 
     The dancer mechanism  80  can be the type of tensioning mechanism that is described in U.S. Pat. No. 5,276,950, incorporated herein by reference. The guiding rollers  31 ,  32 ,  34  and  36  are stationary and are fixed permanently to a frame of the apparatus  110 . The guiding rollers  33  and  35  are mounted on the carriage bar  37 , which moves up and down along the carriage guide  38 . A sensor  39 , which is fixed, continuously detects the position of the carriage bar  37 . If the carriage bar  37  goes up beyond a certain height, the detector sends a signal to the controller  99  so that the motor controlling the roll  6  causes rotation of the roll  6  to an unwind further zipper closure  4 . Unwinding of further zipper closure  4  causes the carriage bar  37  to go downward. Once the carriage bar  37  has reached a minimum height, another signal is sent to the controller  99  to stop rotation and dispensing zipper closure  4 . This cycle is continuously repeated while apparatus  110  is in operation. 
     The method further includes a step of passing the strip of zipper closure  4  through a first tension control loop  61 . The first tension control loop  61  is located downstream of the dancer mechanism  80 . The first tension control loop  61  is provided to result in a minimum tension needed to keep the zipper closure  4  linear and to prevent entanglement. A weighted disk  54  is provided, and the zipper closure  4  is threaded under the weighted disk  54 . The weighted disk  54  is movable up and down by gravity to provide a constant tension to the zipper closure  4 . The zipper closure  4  and the weighted disk  54  are contained within a loop box  60 . A sensor  81  provides feedback to the controller  99  to keep the zipper closure  4  inside the loop box  60 . 
     Still in reference to  FIG. 1 , it can be seen how the zipper closure  4  is threaded around guide roller  51  and into nip  75  between guide rollers  52  and  53 . After nip  75 , the zipper closure enters the loop box  60  and is threaded around the weighted disk  54 . 
     As can be appreciated by comparing the tension loop  61  with the dancer mechanism  80 , in the tension loop  61 , there are no rotating arms or sliding members that have frictional force affecting the tension of the zipper closure  4 . This helps to result in better control of the tension than the in the dancer mechanism  80 . 
     The apparatus  110  and method includes a step of paying out polymeric film  3  from a film roll  5 . The film  3  has periodic eyemarks thereon. The eyemarks are for indicating parting lines where the side seals and cutting will be to create the individual bags or packages. The eyemarks  70  appear at a regular pitch P. In general, the pitch distance P is constant throughout the roll of film  3 , but the placement accuracy of the eyemarks  70  can vary within the roll  5 . 
     The film  3  is advanced toward a sealing station  10 . While it is being advanced, an eyemark detector  72  is provided to detect the eyemark  70  on the film  3 . The eyemark detector  72  sends a signal to the controller  99  to indicate that the eyemark  70  has been detected. 
     After the eyemark  70  is detected on the film  3 , the film  3  is guided around a triangle board  7  to be folded into a desired shape. Typically, this will involve forming the film  3  to have a U-shape, and result in opposing panels with a fold between the opposing panels. At an open side of the folded film  3  is where the zipper closure  4  will be provided. 
     As mentioned previously, the eyemark detector  72  sends a signal to the controller  99 , which captures the position of the nip  75 . The nip  75  is servo-controlled and has a rotational encoder for keeping track of the position of the film  3 . After the eyemark  70  has been detected, an aperture or hole  71  is punched into the zipper closure  4  at the hole punch  57 . The hole punch  57  is located downstream of the first tension control loop  61 .  FIG. 2  illustrates the zipper closure  4  having periodic holes  71  therein, separated by distance P 2  and interlocking members  97 . 
     Once the zipper closure  4  passes the punching operation, the zipper closure  4  is passed on to the second tension control loop  62 . The second tension control loop  62  helps to ensure that the zipper closure  4  that has been punched with hole  71  is maintained with minimal tension, such that the zipper closure  4  is straight and untangled. The second tension control loop  62  also allows for the stopping of the zipper which is necessary for actuating hole punch  57 . The second tension loop  62  is preceded by a driven nip  76  to introduce the punched zipper closure  4  into a loop box  63 . The nip  76  includes a pair of rollers  58 ,  59 . 
     Nip  76  runs in an index and dwell repeat sequence. The controller  99  controls nip  76 , and during the index portion of the sequence, the nip  76  runs for a given distance generally close to, or equal to, the pitch distance P ( FIG. 2 ). The distance that the nip  76  runs in a given index will vary when the system is making adjustments to align the eyemark  70  to the detected hole  71 . Nip  76  stops in a dwell between indexes to allow for the actuation of hole punch  57 . 
     The second tension control loop  62  is constructed similarly as the first tension control loop  61 . A weighted disk  64  moves up and down by force of gravity, and the punched zipper closure  4  is threaded under the weighted disk  64 . The disk  64  provides the punched zipper closure  4  at a constant tension. A detector  82  monitors the level of the punched zipper closure  4  within the loop box  63  and is used as an indication that nip  76  needs to run to keep a loop. Both the loop box  60  and  63  are open in the bottom. 
     After passing through the second tension control loop  62 , the punched zipper closure  4  proceeds through the guide  78  and around guiding roller  79 . 
     An aperture detector  73  is provided downstream of the second tension control loop  62 , and in this embodiment, downstream of the guide  78  and roller  79 . The aperture detector  73  detects the aperture or hole  71  in the zipper closure  4 . After the eyemark  70  is detected by the eyemark detector  72 , the position of film nip  75  is captured by controller  99 . Then the aperture detector  73  detects hole  71 , and the controller  99  captures this position of film nip  75 . The controller  99  is able to calculate the distance between the detected eyemark  70  and the detected hole  71 . The controller  99  compares this distance to the target value that has been entered into controller  99  by the operator. If the compared distances are not equal, controller  99  will adjust the length of the index distance by nip  76  so that they will become equal. If the compared distances are equal, but the hole  71  is not lined up with the eyemark  70 , then the operator is able to perform a step of calibrating the apparatus  110  and provide a correction. The correction can be performed by adjusting the target value entered into controller  99 . 
     By having eyemark detector  72  and aperture detector  73 , in addition to controller  99  that receives the position of both the locations and then automatically adjusts the distance between the holes  71  by changing the index distance from nip  76 , advantages are realized. The advantages include being able to accurately line up the holes  71  in the zipper closure  4  with the film eyemarks  70 , in spite of variations and tension on the zipper closure  4  on the roll  6 , variations in the tension of the film  3 , or variations in the distance between printed eyemarks  70  on the film  3 . 
     The method includes the step of supplying the strip of zipper closure  4  to the sealing station  10 , while simultaneously supplying the film  3  to the sealing station  10  at the same speed as the strip of zipper closure  4 . The sealing station  10  is downstream of the second tension control loop  62  and aperture detector  73 , as well as being downstream of the eyemark detector  72 . 
     Although the zipper closure  4  is stopped intermittently for punching the holes  71 , the accumulation of a sufficient length of zipper closure  4  in the dancer mechanism  80  and tension control loops  61 ,  62  allows the zipper closure  4  to be supplied continuously to the sealing station  10  at the same net speed that the film  3  is supplied. The holes  71  in the zipper closure  4  are lined up with the eyemarks  70  with the zipper closure  4  at minimal tension, so that minimum wrinkles are formed after the bag is made. 
     The method further includes sealing the strip of zipper closure  4  to the film  3 . The sealing step is done while the hole  71  is aligned with the eyemark  70 . 
     During the step of sealing, the strip of zipper closure  4  is sandwiched between two opposing walls of the film  3 , and heated sealing bars transfer heat to the film  3  and zipper closure  4 . In this embodiment, there are three pairs of opposed heating sealing bars, shown at  11   a  and  11   b ;  12   a  and  12   b ; and  13   a  and  13   b . The sealing bars  11   a ,  12   a , and  13   a  extend and retract by actuation of air cylinders  14 ,  15 , and  16 . The air cylinders  14 ,  15 ,  16  are controlled by electro-pneumatic regulators, which accurately control sealing pressure. The controller  99  sends signals to the air cylinders  14 ,  15 ,  16  to extend and retract the sealing bars  11   a ,  12   a , and  13   a.    
     The sealing bars  11   b ,  12   b , and  13   b  are mounted on rod-type electric actuators  17 ,  18 ,  19  that accurately control the amount of extension and retraction. All of the sealing bars  11 ,  12 ,  13  includes electric heaters and thermocouples to control the temperature of the sealing bars by way of a programmable controller having an operator interface. 
     Sealing of the zipper closure  4  to the film  3  is accomplished by extending the heating sealing bars  11 ,  12 ,  13  toward the moving film  3  and applying pressure on Teflon belts  21 ,  22  disposed between the film  3  and the opposing sealing bars. The belts  21 ,  22  rotate continuously in their respective loops. The belts  21 ,  22  move synchronously with the film  3  and zipper closure  4  and are in contact with opposing edges of the film  3 . 
     Depending on the linear speed of the film  3 , a selected number of the sealing bars will be actuated for sealing. That is, only a single set of the opposed sealing bars, two sets of the opposed sealing bars, or all three sets of the opposed sealing bars can be used. At lower film speeds, only one pair of the opposing sealing bars may be actuated. At intermediate film speeds, two sets of the sealing bars may be actuated. At the highest speed, all three sets of sealing bars can be actuated. This results in advantages in that less film  3  and zipper closure  4  is wasted, as there are fewer instances of overheating or underheating. 
     As can be appreciated from the above, by having independent control of single sets of opposed sealing bars, any unsealed film  3  and zipper closure  4  located between sealing bars  11   a  &amp;  11   b  and  13   a  &amp;  13   b  which did not get sealed together during normal line stops will be sealed completely during the process startup. During process startup, sealing bars  11   a  &amp;  11   b  extend towards the moving film  3  and apply pressure on the Teflon belts  21  &amp;  22  sealing film  3  and zipper closure  4  together. At the same time, controller  99  instructs sealing bars  13   a  &amp;  13   b  to extend towards the moving film  3  and apply pressure on the Teflon belts  21  &amp;  22  sealing film  3  and zipper closure  4  together. Depending on the linear speed of the film  3 , controller  99  will retract  13   a  &amp;  13   b  so as not to overheat film  3  and zipper closure  4 . Sealing bars  11   a  &amp;  11   b  will remain in the extended position to seal film  3  and zipper closure  4  together. This operation is helpful to a reduction, or in many cases, elimination of wasted film  3  and zipper closure  4  not sealing together and being rejected by the downstream processing equipment. 
     After the film  3  and zipper closure  4  are processed through the sealing station  10 , they are advanced to a bag machine for product filling and for final bag sealing. Because the holes  71  remove the interlocking members of the zipper  71  at the parting lines between the bags, the amount of heat required to make the final seals is lower as compared to if the holes  71  were not provided. 
     As can be appreciated from the above, the first and second tension control loops  61 ,  62  help to deliver the zipper closure  4  with minimal tension at the time of attachment of the zipper closure  4  to the film  3 , while ensuring accurate alignment of the holes  71  with the film eyemarks  70 . This results in individual bags that are wrinkle free. The minimal tension is a tension less than 0.8 lbs, and is typically between 0.05 lbs and 0.7 lbs. In many preferred systems and methods, the tension is less than 0.2 lbs, indeed often less than 0.15 lbs. In an example system, the tension is about 0.1lbs. 
     Modifications can be made to this process and still result in the above advantages. For example, three tension control loops can be used instead of a dancer mechanism and two tension control loops. Alternatively, only one tension control loop can be used. 
     The above represents example principles. Many embodiments can be made using these principles.