Abstract:
The zippers include flanges with fully or partially formed apertures or notches to allow drive rolls to positively engage and feed the zippers. Alternatively, a T-shaped guide rail can be formed on at least one flange to allow drive rolls to engage the zipper. These aspects are particularly adaptable to feeding a zipper or zipper segment to a transverse direction zipper applicator.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for producing perforated zipper for positive and improved feeding and tracking of the zipper through a transverse direction zipper applicator, particularly in the art of producing reclosable packaging. 
         [0003]    2. Description of the Prior Art 
         [0004]    In the prior art of reclosable packaging and the methods of manufacture thereof, including form fill and seal (FFS) and related methods, it is well-known to provide and apply the reclosable zipper in a direction which is transverse to the direction of movement of the film (i.e., the machine direction). While these methods are well-developed and suitable for their intended purposes, further improvements are sought in the reliability of the tracking and placement of the zipper into the final position where it is sealed to the film, particularly when production rates and speeds are increased. 
         [0005]    In particular, nip roll systems typically include one or more sets of smooth or patterned rolls. However, these systems may have difficulty in consistently pushing a soft zipper to the final desired position prior to sealing to the film. Similarly, due to the asymmetrical nature of some zipper profiles, zippers that travel through the nips may become skewed and lose their tracking. Similarly, the zipper may need to be supported between or after a set of nips. This is typically done with rollers, which may further contribute to the skewed tracking of the zipper. 
         [0006]    Similarly, grip and pull drive systems use a chain drive or a servo driven clamp system to place the zippers. While these systems are well-developed and suitable for their intended purposes, the zipper may have to be released and recaptured from the drive system in order to perform necessary options such as end crushing or cutting. This may become less reliable at higher production rates. Similarly, if a zipper segment that is ready to be sealed to the film is gripped by a clamp, the clamping assembly may obstruct the zipper-to-film sealing process. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0007]    It is therefore an object of the present invention to provide a method for the transverse placement of zippers on a moving film, particularly in the production of reclosable packages wherein the reliability of the tracking and placement of the zipper are improved, thereby leading to the possibility of higher production rates. 
         [0008]    This and other objects are attained by providing a zipper with perforated or punched flanges that will allow the feeding apparatus to feed and drive the zipper positively to a transverse direction (TD) zipper application device, which places the zipper onto a film perpendicular to the direction of film travel. 
         [0009]    Alternatively, a textured surface is provided on the portion of the zipper flanges that face the driving rollers in the transverse direction drive train. The texturing allows the zipper drive rollers or belts to positively engage and move the zipper forward. The texturing can be rough surface which is engaged by gnurled drive rolls, or can be a shape extruded into the zipper flange that allows the drive rollers or belts to grab the zipper. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a perspective view of a double-flanged zipper profile for a reclosable package, with a first flange illustrating a first alternative of punched apertures and the second flange illustrating a second alternative of perforations. 
           [0012]      FIG. 2  is a perspective view of a zipper formed from a double-flanged zipper profile of  FIG. 1 , and a single-flanged zipper profile. 
           [0013]      FIG. 3  is a perspective view of a roller device punching apertures, perforations or similar cuts into the flanges of a double-flanged zipper profile for a reclosable package. 
           [0014]      FIG. 4  is a perspective view of a double-flanged zipper profile for a reclosable package being driven by a toothed drive wheel which positively engages the apertures, perforations or similar cuts in the flanges of the zipper. 
           [0015]      FIG. 5  is a plan view of two toothed drive wheels, illustrating the resulting positive control of zipper tension and steering. 
           [0016]      FIG. 6  is a perspective view of a zipper being driven by rollers which engage a rail extruded into the zipper. 
           [0017]      FIG. 7  is a cross-sectional view along plane  7 - 7  of  FIG. 6 . 
           [0018]      FIG. 8  is a perspective view of a zipper with driving notches extruded or otherwise into the flanges. 
           [0019]      FIG. 9  is a cross-sectional view of the zipper of  FIG. 8  being driven by a pair of drive wheels, one with a complementary texture to the extruded driving notches of  FIG. 8 . 
           [0020]      FIG. 10  is a schematic of a first method for forming the reclosable zipper. 
           [0021]      FIG. 11  is a schematic of a second method for forming the reclosable zipper. 
           [0022]      FIG. 12  is a schematic of a third method for forming the reclosable zipper. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    Referring now to the drawings in detail wherein like numerals indicate like elements throughout the several views, one sees that  FIG. 1  illustrates double-flanged zipper profile  12  as is used for a reclosable package (not shown) formed from walls of polymeric or similar material. Double-flanged zipper profile  12  is typically paired with a single-flanged zipper profile to form a reclosable zipper  10  (see  FIG. 2 ). Double-flanged zipper profile  12  includes interlocking element  16  with first flange  20  and second flange  22  extending therefrom. First and second flanges  20 ,  22  may be formed from a single piece of polymeric material or separate pieces of polymeric material. 
         [0024]    In  FIG. 1 , the first flange  20  illustrates a first aspect of the present invention, wherein apertures  24  are punched or otherwise formed so as to pass completely through first flange  20  so that material is removed, or at least absent from, the aperture or channel  24 . The second flange  22  illustrates a second aspect of the present invention wherein a C-shaped or similar cut or incision is formed in second flange  22  whereby no significant material is removed from second flange  22 , but a flap-like structure is formed (referred to as “perforated” herein) whereby gears and similar structures can pass through the resulting partially formed aperture  26 . 
         [0025]    While first and second aspects of the present invention are illustrated on respective first and second flanges  20 ,  22 , it is envisioned that first and second flanges  20 ,  22  of zipper profile  12  will typically have substantially identical structures. 
         [0026]      FIG. 2  illustrates the double-flanged zipper profile  12  of  FIG. 1 , joined with a single-flanged zipper profile  14 , to form zipper  10 . Single-flanged zipper profile  14  includes second interlocking element  18  and flange  19 . Second interlocking element  18  is configured and arranged to be releasable attachable or reclosable with first interlocking element  16 . Flange  19  is illustrated with apertures  24  but may likewise be formed with partially formed apertures  26  as described above. 
         [0027]    Flanges  19 ,  20 ,  22  provide locations for attachment to the polymeric walls of the reclosable package (not shown). 
         [0028]      FIG. 3  illustrates how rotary punch  100  with two sets of laterally adjacent protrusions  102 ,  104  will form apertures  24  or  26  on a moving length of double-flanged zipper profile  12 . Protrusions  102 ,  104  may be formed as a punch to remove significant material thereby forming an aperture or channel  24  or may be formed as a C-shaped blade thereby forming an incision and the flap-like structure of the partially formed aperture  26  as described above. 
         [0029]      FIG. 4  illustrates how drive roll  200  with radially extending spike-like protrusions  202  to extend through apertures  24  (or likewise, partially formed apertures  26  which are defined as perforated as described above) thereby positively engaging double-flanged zipper profile  12 , particularly for feeding to a transverse direction zipper applicator (not shown). Drive roll  200  can have one row of radially extending spike-like protrusions or two rows. 
         [0030]      FIG. 5  illustrates that two drive rolls  200 ,  200 ′, particularly if the rotation is monitored and controlled, such as through a servo mechanism, can closely control the tension of zipper  10  therebetween. 
         [0031]      FIGS. 6 and 7  illustrate zipper profile  30  with male interlocking element  32  and flange  34  extending therefrom (typically provided with a corresponding zipper profile with complementary female interlocking element). Flange  34  further includes drive rail  36 , comprising stem  38  (extending perpendicularly from flange  34 ) and head  40  (parallel to and separated from flange  34 ) thereby forming a T-shaped cross section, extending therefrom. Drive rail  36  is typically integrally extruded with zipper profile  30 . Drive rail  36  is engaged by drive rolls  210 ,  212  (also see the cross-sectional view of  FIG. 7 ) thereby permitting drive rolls  210 ,  212  to positively engage and feed the zipper profile  30 . 
         [0032]      FIGS. 8 and 9  illustrate zipper profile  30  with male interlocking element  32  and row of notches or indentations  44 . Notches  44 , which may be formed by extrusion, cutting, or similar processes, are parallel to each other and transversely oriented with respect to a length of the zipper  10 . This permits drive roll  214 , which includes a gnurled surface complementary in shape to the row of notches or indentations  44 , to positively engage and feed the zipper profile  30 . Typically, a smooth drive roll  216 , with a cylindrical cross section, opposes drive roll  214 . 
         [0033]      FIGS. 10-12  illustrate three possible non-limiting examples of manufacturing methods for zipper  10 . However, those skilled in the art will recognize a broad range of equivalents after review of this disclosure. 
         [0034]      FIG. 10  illustrates a first method for manufacturing the zipper  10  as described above. The zipper  10  is extruded at extrusion station  400  so as to form separate first and second profiles  12 ,  14 . Rotary punch  100  forms the apertures  24  or  26  in the flanges  19 ,  20 ,  22  as described above. First and second profiles  12 ,  14  are joined by interlocking the respective interlocking elements together at joining station  402  and then wound onto outgoing spool  404 . 
         [0035]      FIG. 11  substitutes a supply spool  396  and separating station  398  for the extrusion station  400  of  FIG. 9 . 
         [0036]      FIG. 12  substitutes a package or bag making process  406 , typically with a transverse direction zipper applicator (not shown), for the outgoing spool  404  of  FIG. 10 . 
         [0037]    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.