Patent Publication Number: US-6656297-B2

Title: Method for applying a narrow web zipper transverse to the film direction

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to method for applying a zipper to a web, particularly a relatively narrow zipper in a direction transverse to the film direction in a form fill and seal apparatus. 
     2. Description of the Prior Art 
     In the prior art, form fill and seal apparatus and methods are known. While these methods and apparatus have been extremely successful for the high speed packaging of various kinds of foodstuffs, improvement is desired with respect to the application of narrow zippers in the direction transverse to the direction of the film. More particularly, improvement is desired with respect to the handling of narrow zippers during installation. 
     SUMMARY OF THE INVENTION 
     The present invention provides an applicator which uses a series of grooved rollers or a grooved guide plate to trap the zipper as it is being fed across the web. When in position, the web momentarily stops to allow the seal bar to tack the zipper to the film from below the film. The rollers and guide plate act as an anvil to provide pressure from the seal bar. The rollers, guide plate and seal bars then retract to allow the film to index forward. After the cylindrical shape of the bag or other container has been formed, the bottom and top bag seal jaws close. The zipper seal bars then apply heat and pressure to the zipper to tack and seal the zipper to both sides of the bag. 
     More particularly, a guide system is used to guide and move the zipper in a precise position perpendicular or transverse to the direction of the web. This system of rollers provide positive tensioning to the zipper by increasing the speed over the zipper feed roller. It also allows a wide range of lengths to be fed because there will always be at least one roller in contact with the zipper. The roller assembly will further retract from the zipper guide plate to allow the zipper, which is attached to the film at the station, to travel with the film without interference. 
     Additionally, seal bar assemblies are used with a first seal bar for forming the upper transverse seal on a package along with a second seal bar for forming the lower transverse seal on a subsequent package. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein: 
     FIG. 1 is a perspective view showing the applicator for the zipper, using grooved rollers. 
     FIG. 2 is a plan view showing the positioning of the guide plate with respect to the guide rollers. 
     FIG. 3 is a perspective view of the top seal bar, bottom seal bar and zipper seal bar of the present invention. 
     FIGS. 4 a - 4   d  are plan views showing the sequence of the operation of the present invention in a form fill and seal apparatus. 
     FIG. 5 is a plan view showing the position of the various seal bars after a prior bag has been completed and is falling away, and the present bag is ready to be indexed into position for filling and sealing. 
     FIG. 6 is a plan view showing the position of the various seal bars after the present bag of the FIG. 5 has been indexed into position and filled, with one seal bar forming an upper transverse seal in present bag and another seal bar forming a lower transverse seal in the subsequent bag. 
     FIG. 7 is a plan view showing the position of the zipper seal bar completing the sealing the zipper to the web on the top of the present bag. 
     FIG. 8 is a plan view showing the position of the various seal bars as the knife separates the present bag from the subsequent bag, in preparation for the present bag falling away as shown in FIG. 5 after the various seal bars are retracted. 
     FIG. 9 is a perspective view of the web running between the separated seal bars, similar to the configuration shown in FIG.  5 . 
     FIG. 10 is a perspective view of the web with several successive bags running between the separated seal bars. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in detail wherein like numerals refer to like elements throughout the several views, FIG. 1 is a perspective view of the web  100  which is running in the direction indicated as A in the environment of a form fill and seal apparatus. A length of zipper material  200  is fed in the direction indicated as B, which is transverse to the direction indicated as A. Zipper material  200  includes successive zipper segments  202 . Zipper material  200  is further envisioned as being relatively narrow. Installed zipper segments  202 ′ are further shown as having been previously tacked to web  100 . Zipper material  200  is positioned by applicator  10  which includes a series of grooved rollers  12  with axes of rotation substantially parallel to the direction indicated as A. Applicator  10  drives and positions zipper material  200  and further includes guide plate  14  which may similarly be grooved. 
     As depicted by FIG. 2, seal bar  16  is positioned underneath web  100 , opposing grooved rollers  12  and guide plate  14 . When web  100  is in the proper position for application of a zipper segment  202 , web  100  momentarily stops to allow seal bar  16  to tack-seal the zipper segment to the web  100  from below the web  100 . Grooved rollers  12  and guide plate  14  act as an anvil for seal bar  16  and remain in a static position as seal bar  16  is urged against the underside of web  100 , in the direction indicated as C. Seal bar  16  is then retracted in the direction indicated as D. By retracting seal bar  16 , web  100  is allowed to index forward in direction A. 
     Rather than tack-sealing, a sealing part of the lower zipper base at seal bar  16  could be used to increase the inside opening force of the bag. Such a system would be more suited to double-string zippers, compression post zippers or other wider construction zippers. Sealing the remaining areas of the zipper base is described below. 
     Applicator  10  may be enhanced by providing a system of rollers providing positive tension on zipper segment  202 ′ by increasing its speed over that of the zipper feed roller. This also allows a wide window of zipper lengths to be fed because at least one roller will be in contact with the zipper segment  202 ′. The roller assembly would retract from the zipper guide plate to allow the zipper segment  202 ′, which is attached to the web  100  at this station, to travel with the web  100  without any interference. 
     The form fill and seal apparatus then forms the web into a cylindrical shape and fills and seals in the sequence shown in FIGS. 4-8. Similarly, FIG. 3 shows the seal bar assembly  20  used in this sequence. Two opposing seal bar assemblies  20 ,  20 ′ are used as shown in FIGS. 5-8. 
     The lower portion of seal bar assembly  20  includes a top bag forming seal bar  22  for forming the top transverse seal  302  (see FIGS. 4-8) of a bag  300  substantially simultaneously with the formation of a bottom transverse seal  304 ′ on a subsequent bag  300 ′ by bag bottom forming seal bar  24  which is formed on an upper portion of seal bar assembly  20 . 
     When zipper seal bars  32  are used where part of the lower zipper base has previously been sealed by the seal bar  16  to increase the inside opening force of the bag; the portions of seal bars  32  in contact with the previously sealed areas will remain unheated. Opposing zipper seal bars  32  should be wide enough to seal the entire base of the zipper, in order to differentiate between the remaining sections of the base and the partially (hinged) sealed section. 
     In both circumstances of sealing the bag, slot  26  is formed between top bag forming seal bar  22  and bag forming bottom seal bar  24 . Slot  26  of seal bar assembly  20 ′ includes a knife blade  28  which extends and retracts therefrom. Slot  26  of seal bar assembly  20  provides a path into which knife blade  28  can extend and retract. 
     Recess  30  is centrally located within top seal bar  22 . Zipper seal bar  32  extends and retracts from recess  30 . 
     Zipper seal bars  32  are large enough in the machine direction to allow for proper sealing of the zipper segment  202 ′, which is envisioned to be relatively narrow, to the opposite bag wall given the ability of the apparatus to properly feed the bag film the length of the package. Therefore, during the manufacture of several consecutive packages, different regions of zipper seal bars  32  may perform the sealing operation. Zipper seal bars  32  are designed to close to a point sufficient to seal the zipper segment  202 ′ to the opposite bag wall. However, if a sensor (not shown) is used to sense the position of the zipper segment  202 ′, this may be used to reduce the sealing area of the zipper seal bars  32  in the machine direction. Zipper seal bars  32  may be designed to limit the pressure applied to the zipper during sealing thereby avoiding deformation of the zipper. Zipper seal bars  32  may also be designed to the full length of the seal bar  20 , allowing a full-length zipper for the width of the bag. The zipper seal bar  32 , depicted in FIG. 2, would provide a bag with a zipper that is shorter than the width of the bag and where the rest of the bag is sealed closed. 
     Furthermore, the zipper segment  202 ′ may include a sealing bridge  203 ′ that aids in quick sealing and prevents damage to the zipper lock members. Such damage may be caused when sealing the zipper to film directly behind zipper lock members. The sealing bridge  203 ′ as shown in FIG. 4 b  is a buffer strip of sealable material pre-attached to zipper segment  202 ′. As shown in FIG. 4 a,  sealing bridge  203 ′ would be on the face of zipper segment  202 ′ which permanently seals as a result of zipper seal bars  32 . The sealing bridge  203 ′ may be used in any area where zipper segment  202 ′ attaches or seals to the bag structure. 
     Similarly, the back side of the zipper segment  202 ′ may be designed to seal to the film in a manner that increases the product side opening force. The zipper segment  202 ′ may also contain a tamper evident feature such as a peel seal or a joined web. Additionally, the top bag forming seal bar  22  may be designed to create an easy open feature such as a shaped seal with a tear notch. 
     As can be seen from FIGS. 5-8, seal bar assembly  20 ′ is driven by pneumatic cylinder  40 , or a similar mechanical or electromechanical device, to reciprocate to and from the position that engages web  100 , while seal bar assembly  20  is illustrated as stationary. Seal bar assembly  20 ′ may be spring-loaded in order to aid in retraction. However, seal bar assembly  20  may likewise be driven by a pneumatic cylinder or similar mechanical or electromechanical device. Likewise, zipper seal bars  32  are driven to reciprocate to and from the position engaging web  100  by pneumatic cylinders  42 , or similar mechanical or electromechanical devices. The device built to move zipper seal bars  32  may be designed to limit the pressure applied to the zipper in order to prevent deformation of the zipper. 
     The typical sequence of events is as follows. A prior bag  400  falls away as shown in FIG.  5 . Top transverse seal  402  of prior bag  400  has been formed simultaneously with bottom transverse seal  304  of bag  300  by the prior operation of seal bars  22 ,  24 . Web  100  is indexed downwardly to the position shown in FIG. 4 a  and filled with foodstuffs or similar contents  1000 . At this point, zipper segment  202 ′ has been previously tacked to one side of web  100 . Seal bar assembly  20 ′ is then driven by pneumatic cylinder  40  to engage web  100  between seal bar assemblies  20  and  20 ′ as shown in FIG.  6 . Top seal bars  22  form the top transverse seal  302  while bottom seal bars  24  form the bottom transverse seal  304 ′ of subsequent bag  300 ′. 
     Subsequent to or simultaneously with the formation of transverse seals  302 ,  304 ′, pneumatic cylinders  42  drive zipper seal bars  32  together thereby engaging zipper segment  202 ′ and a portion of web  100  therebetween as shown in FIGS. 4 b  and  7  thereby permanently sealing zipper segment  202 ′ to both sides of web  100 . 
     Knife  28  then extends from slot  26  of seal bar assembly  20 ′ partially into slot  26  of seal bar assembly  20  thereby separating bag  300  from web  100  as shown in FIGS. 4 c  and  8 . Seal bar assemblies  20 ,  20 ′ retract away from each other, knife  28  is retracted into slot  26  of seal bar assembly  20 ′, and zipper seal bars  32  are retracted from each other as shown in FIG. 4 d.  Filled bag  300  then falls away in the same manner that prior bag  400  fell away in FIG.  5 . 
     A variation on this apparatus and method would manufacture unfilled pre-made pouches without forming bottom transverse seal  304  in order to allow subsequent filling and sealing. 
     Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.