BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Prior Art
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.
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.
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
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.
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.
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
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 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.
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.
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.
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.
FIG. 5 is a plan view of two toothed drive wheels, illustrating the resulting positive control of zipper tension and steering.
FIG. 6 is a perspective view of a zipper being driven by rollers which engage a rail extruded into the zipper.
FIG. 7 is a cross-sectional view along plane 7-7 of FIG. 6.
FIG. 8 is a perspective view of a zipper with driving notches extruded or otherwise into the flanges.
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.
FIG. 10 is a schematic of a first method for forming the reclosable zipper.
FIG. 11 is a schematic of a second method for forming the reclosable zipper.
FIG. 12 is a schematic of a third method for forming the reclosable zipper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
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.
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.
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.
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.
Flanges 19, 20, 22 provide locations for attachment to the polymeric walls of the reclosable package (not shown).
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.
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.
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.
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.
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.
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.
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.
FIG. 11 substitutes a supply spool 396 and separating station 398 for the extrusion station 400 of FIG. 9.
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.
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.
Patent Application
20090097782
