WO2001070491A1

WO2001070491A1 - Apparatus and method for inserting a slider onto a fastener

Info

Publication number: WO2001070491A1
Application number: PCT/US2001/006232
Authority: WO
Inventors: Toby R. Thomas
Original assignee: Pactiv Corporation
Priority date: 2000-03-22
Filing date: 2001-02-27
Publication date: 2001-09-27
Also published as: AU2001241804A1

Abstract

A method of making reclosable plastic bags includes the following steps: moving a continuous fastener (10) along a predetermined path, the fastener (10) including a pair of interlocking profiles (16, 20) and a pair of fins (18, 22) extending downward from the respective profiles; severing the fastener at a station along the path to produce adjacent cut ends (32, 34) in the fastener (10); moving the cut ends of the fastener (10) laterally relative to each other to expose the ends (32, 34); inserting a slider (26) over one of the exposed ends (32); continuing the movement of the fastener (10) for a distance approximately corresponding to a predetermined width of the reclosable plastic bag to advance a new section of the fastener to the fastener severing station; after inserting the slider (26) over one of the exposed ends (32), attaching the fastener (10) to a continuous web of plastic bag material; and forming side seals in the bag material and severing the bag material from the remaining continuous web.

Description

APPARATUS AND METHOD FOR INSERTING A SLIDER ONTO A

FASTENER

FIELD OF THE INVENTION

The present invention relates generally to methods of making reclosable plastic bags and, more particularly, relates to an apparatus and method of making reclosable plastic bags in which a slider is inserted onto a fastener prior to attaching the fastener to a continuous web used to form the walls of the bag.

BACKGROUND OF THE INVENTION Plastic reclosable fasteners or zippers operated by sliders are well known in the art. Such a fastener includes interlocking male and female profiles and a pair of fins extending downward from the respective profiles. To open and close the fastener, a slider is slidably mounted to the fastener. The slider is generally of a U-shaped configuration having inwardly extending shoulders at the open end of the U to maintain the slider on the fastener as the slider is moved from one end to the other of the fastener. In the manufacture of thermoplastic bags, the fastener extends along the mouth of a bag and is secured in any suitable manner to flexible walls of the bag. For example, the fins of the fastener may be integrally formed with the respective walls of the bag, or may be extruded separately and thereafter attached to the respective walls along the mouth of the bag.

For reasons of economy, it is desirable to make the reclosable plastic bags by a continuous bag-making process. In one such process disclosed in U.S. Patent No. 5,431,760 to Donovan, a continuous web of thermoplastic film having a fastener attached to one edge thereof is moved along a predetermined path. The movement of the fastener and the web along the path is periodically interrupted. While the movement is interrupted, the fastener is severed at a station along the path to produce adjacent cut ends of the fastener. Next, the cut ends of the fastener are moved laterally relative to each other to expose the cut ends. A slider is inserted over one of the exposed ends prior to forming side seals in the bag material and severing the bag material from the remaining continuous web. Thereafter, the fastener and the web of bag material are moved for a distance corresponding to a predetermined width of the

l reclosable plastic bag to advance a new section of the fastener and the web to the severing station.

The Donovan process is advantageous in that it eliminates the need for installing a slider transversely of the fastener in a continuous bag-making machine and enables the use of a one-piece slider with no moving parts. A one-piece slider is normally structurally stronger than sliders that require assembly as they are placed on the fastener.

The Donovan process inserts a slider endwise onto a fastener that has already been attached to a web of bag material. This sequence of process steps is acceptable if the entire bag-making process, including installation of the sliders, is performed on a single manufacturing line. It, however, has become increasingly common for a first manufacturer or manufacturing line to mount sliders on a continuous fastener, and a second manufacturer or manufacturing line to attach such a slider-carrying fastener to a continuous web of bag material and form individual bags. Accordingly, there is a need to apply the advantages of the Donovan process to the situation where a slider is inserted onto a fastener prior to attaching the fastener to the continuous web of bag material.

SUMMARY OF THE INVENTION A method of making reclosable plastic bags includes the following steps: moving a continuous fastener along a predetermined path, the fastener including a pair of interlocking profiles and a pair of fins extending downward from the respective profiles; severing the fastener at a station along the path to produce adjacent cut ends in the fastener; moving the cut ends of the fastener laterally relative to each other to expose the ends; inserting a slider over one of the exposed ends; continuing the movement of the fastener for a distance approximately corresponding to a predetermined width of the reclosable plastic bag to advance a new section of the fastener to the fastener severing station; after inserting the slider over one of the exposed ends, attaching the fastener to a continuous web of plastic bag material; and forming side seals in the bag material and severing the bag material from the remaining continuous web. To preserve the integrity of the fastener in the bag-making process, the profiles and only a portion of the fastener fins are severed at the severing station. A portion of the fastener fins remains intact so that sections of the fastener on opposite sides of the cut ends remain connected.

A bag-making apparatus includes means for periodically severing a fastener to produce adjacent cut ends in the fastener; means for moving the cut ends of the fastener laterally relative to each other to expose the ends; means for inserting a slider over one of the exposed ends; means, downstream from the insertion means, for attaching the fastener to marginal edges of a continuous web of plastic bag material; and means for forming side seals in the bag material and severing the bag material from the remaining continuous web. The above summary of the present invention is not intended to represent each embodiment, or every aspect of the present invention. This is the purpose of the figures and detailed description which follow.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a fractional perspective view of a plastic fastener at a station for severing the fastener to produce adjacent cut ends in the fastener; FIG. 2 is a fractional perspective illustrating the severing operation and moving the cut ends of the fastener laterally relative to each other to expose the ends;

FIG. 3 is a fractional perspective view illustrating the insertion of the slider over one of the cut ends of the fastener;

FIG. 4 is a fractional perspective view illustrating the slider after it has been inserted onto the fastener;

FIG. 5 is a fractional perspective view illustrating the attachment of the slider- carrying fastener to one edge of a continuous web of plastic bag material; and

FIG. 6 is a fractional perspective view illustrating the formation of side seals in the bag material and the severing of the bag material from the remaining continuous web.

While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIGS. 1-6 collectively illustrate an apparatus and method of making reclosable plastic bags. The bag-making process is continuous in the sense that a continuous slider-carrying fastener is attached to a continuous web of plastic bag material, which is then divided into individual plastic bags. The sliders may be inserted onto the fastener at a manufacturing site or line different from the site or manufacturing line on which the fastener is attached to the continuous web of bag material.

FIG. 1 illustrates a continuous fastener 10 moving along a predetermined path designated by the arrow. The fastener 10 includes first and second opposing tracks 12 and 14. The first track 12 includes a profile 16 and a fin 18 extending downward from the profile 16, while the second track 14 includes a profile 20 and a fin 22 extending downward from the profile 20. To provide tamper evidence, the fins 18 and 22 may be joined to each other along a line of weakness 24 to effectively create a single fin comprised of the two fins 18 and 22. The line of weakness 24 may be a scored line, a perforated line, or a thinned die line.

The profiles 12 and 14 have complementary cross-sectional shapes such that they can be interlocked by pressing the profiles together with a slider 26 (see FIG. 4). One of the profiles 12 and 14 preferably includes a rib-type element, while the other of the profiles 12 and 14 includes a groove-type element adapted to interlock with the rib-type element. The cross-sectional shapes of the interlocking profiles 12 and 14 may be of any type, such as that disclosed in U.S. Patent No. 5,007,143, which is incorporated herein by reference in its entirety. It should be understood that the present invention is not limited to the shapes of the profiles 12 and 14 illustrated herein and that other shapes can be utilized in connection with the present invention. Referring to FIG. 1, a pair of reciprocating knives 28 and 30 are positioned on opposite sides of the predetermined path of travel of the continuous fastener 10. The knives 28 and 30 are adapted to move transversely to the path of fastener travel as indicated by the arrows in FIG. 1. The movement of the fastener 10 along the path of travel is periodically interrupted.

Referring to FIG. 2, while the movement is interrupted, the knives 28 and 30 sever the fastener 10 at a station along the path to produce adjacent cut ends 32 and 34 in the fastener 10. The cut ends 32 and 34 of the fastener 10 are moved laterally relative to each other to expose the ends. This can normally be accomplished by the frictional engagement between the cut ends 32 and 34 of the fastener 10 and the adjacent side surfaces of the knives 28 and 30. Referring to FIG. 3, while the cut ends 32 and 34 are laterally displaced, a slider 26 is fed from a magazine supply 36 of sliders over one of the exposed ends. Once the cut ends 32 and 34 of the fastener 10 are laterally displaced by the action of the knives 28 and 30, they will normally remain displaced due to the flexible nature of the fastener fins 18 and 22. However, vertically extending retractable fingers may be utilized if necessary to maintain the cut ends 32 and 34 of the fastener 10 displaced at the severing station illustrated in FIG. 3 during insertion of the slider 26.

The slider 26 is threaded or moved onto the end 32 of the fastener 10 as shown in FIG. 4, and thereafter the movement of the fastener 10 continues for a distance approximately corresponding to a predetermined width of a reclosable plastic bag to advance a new section of the fastener 10 to the fastener severing station. When the slider 26 is inserted onto the exposed end 32, the slider 26 is oriented in such a way that the slider 26 properly operates to open and close the bag-width fastener section 38. For example, if the fastener section 38 is to be closed by moving the slider 26 toward the end 32 and is to be opened by moving the slider 26 away from the end 32, then the slider 26 should be oriented such that its narrower closing end 26a is inserted onto the fastener section 38 before its wider opening end 26b.

Referring to FIG. 5, after the slider 26 has been positioned on the fastener 10, the slider-carrying fastener 10 is attached to marginal edges of a continuous folded web 40 of plastic bag material. If the sliders 26 are inserted onto the fastener 10 at a different manufacturing site or line, the fastener 10 carries the sliders 26 at bag- width distances apart and the fastener 10 is fed between the marginal edges of the folded web 40 from a storage medium such as a reel or a box. If, however, the sliders 26 are inserted onto the fastener 10 on the same manufacturing line as the folded web 40, the each bag- width section of the fastener 10 carrying a slider 26 may be fed between the marginal edges of the folded web 40 immediately after the slider 26 is inserted onto the fastener section to be attached to the web.

Sealers 42 and 44 seal the fins 18 and 22 to respective flexible walls of the folded web 40. The sealers 42 and 44 may be stationary convective (hot air) sources that do not contact the web 40, or reciprocating heated bars that intermittently contact the web 40. If the sealers 42 and 44 are convective sources, the movement of the slider-carrying fastener 10 and the folded web 40 along their predetermined path need not be interrupted to effectuate the attachment of the fastener 10 to the web 40. If, however, the sealers 42 and 44 are heated bars, the movement of the slider- carrying fastener 10 and the folded web 40 is periodically interrupted. While the movement is interrupted, the heated bars move transversely inward and contact the respective walls of the web 40 for a length of time sufficient to seal the fastener fins 18 and 22 to the respective walls of the web 40. If the sliders 26 are inserted onto the fastener 10 on the same manufacturing line as the folded web 40, the interruption of movement to accommodate the heated bars (FIG. 5) may be the same interruption of movement to accommodate the insertion of the slider 26 (FIGS. 1-4). Therefore, as the slider 26 is inserted onto one fastener section (e.g., section 38), the heated bars simultaneously attach a downstream fastener section to the web 40. Referring to FIG. 6, a reciprocating heated bar 46 seals the opposing walls of the folded web 40 to each other in the transverse direction at bag-width distances apart and, at the same time, severs the bag material from the remaining continuous web to create an individual plastic bag. Alternatively, the heated bar 46 may only form the side seal, and a separate knife could sever the web along the side seal. In a manner similar to that discussed above in connection with attaching the fastener 10 to the web 40, the movement of the web 40 is interrupted during the step of forming the side seal. This interruption of movement to accommodate the heated bar 46 (FIG. 6) may be the same interruption of movement to accommodate the heated bars 42 and 44 (FIG. 5).

In a conventional continuous bag-making process or slider installation process, the fastener 10 moves intermittently through the machine in a continuous stream, so there is no end to the fastener 10 onto which the slider 26 can be inserted endwise.

Under the present invention, during the intermittent motion-part of the machine, the fastener 10 is cut apart at the location that is to be aligned with the side of a bag, the ends formed by the cutter are moved laterally relative to each other to expose the cut ends, and the slider 26 is inserted over one of the exposed ends. This eliminates the need for installing a slider transversely of the fastener in a continuous machine and enables the use of a one-piece slider with no moving parts. A one-piece slider is normally structurally stronger than sliders that require assembly as they are placed on the fastener.

The packaging web 40 may be composed of various plastic polymers, copolymers, coextrusions and/or laminations. The web 40 is preferably comprised of mono-layer or multi-layer combinations of: polyethylene (high, medium, low, linear low, and or ultra low density polymers including metallocene); polypropylene (oriented and/or biaxially oriented); ethylene vinyl acetate; nylon (oriented and/or biaxially oriented); polyethylene terephthalate (oriented and/or biaxially oriented); polyvinyl chloride; ethylene vinyl alcohol (ENOH); polyvinylidene chloride (PNDC); polyvinyl alcohol (PNOH); polystyrene; foil and/or metalization; and paper. The slider 26 is preferably comprised of mono-material, blends, alloys, and/or co-polymers of: polyethylene (high, medium, low, linear low, and/or ultra low density polymers); polypropylene (oriented and/or biaxially oriented); ethylene vinyl acetate; nylon (oriented and/or biaxially oriented); thermoplastic polyesters; polycarbonate; acrylics; and/or polystyrene. The fastener tracks 12 and 14 are preferably comprised of mono-layer, blends, alloys, coextrusions, laminations and/or coatings of: polyethylene (high, medium, low, linear low, and/or ultra low density polymers including metallocene); polypropylene (oriented and/or biaxially oriented); ethylene vinyl acetate; nylon (oriented and/or biaxially oriented); polyethylene terephthalate (oriented and/or biaxially oriented); polyvinyl chloride; ethylene vinyl alcohol (ENOH); polyvinylidene chloride (PNDC); polyvinyl alcohol (PNOH); polystyrene; foil and/or metalization; and paper.

While the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. For example, movement of the fastener need not be periodically interrupted to sever the fastener, expose the cut ends, and insert the slider over one of the exposed ends.

Rather, the same steps may be accomplished with a fully continuous process and relative motion to sever the fastener and insert the slider. Furthermore, the fastener need not be attached to marginal edges of a continuous folded web of plastic bag material. Rather, the fastener can alternatively be attached (1) at one edge of the folded web, (2) on a layflat (non-folded) web in the direction of material movement, or (3) on a layflat web transverse to the direction of material movement. If the fastener is attached to a layflat web , the web is later folded and appropriately sealed to form a bag with opposing sides and opposing top and bottom bridging the sides. Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of making reclosable plastic bags, comprising: moving a continuous fastener along a predetermined path, the fastener including a pair of interlocking profiles and a pair of fins extending downward from the respective profiles; severing the fastener at a station along the path to produce adjacent cut ends in the fastener; moving the cut ends of the fastener laterally relative to each other to expose the ends; inserting a slider over one of the exposed ends; continuing the movement of the fastener for a distance approximately corresponding to a predetermined width of the reclosable plastic bag to advance a new section of the fastener to the fastener severing station; and after inserting the slider over one of the exposed ends, attaching the fastener to a continuous web of plastic bag material.

2. The method of claim 1 , further including the steps of forming side seals in the bag material and severing the bag material from the remaining continuous web.

3. The method of claim 1 , wherein the step of severing the fastener includes severing the profiles and only a portion of the fastener fins so that sections of the fastener on opposite sides of the cut ends remain connected.

4. The method of claim 1 , wherein the fins are j oined to each other along a predetermined area of weakness to effectively create a single fm comprised of the pair of fins.

5. The method of claim 1 , further including the step of periodically interrupting the movement of the fastener along the path, and wherein the severing step, the moving step, and the inserting step are performed while the movement is interrupted.

6. The method of claim 1, wherein the continuous web is folded, and wherein the step of attaching the fastener includes attaching the fastener to marginal edges of the continuous folded web of plastic bag material.

7. The method of claim 1, further including the step of forming the continuous web of plastic bag material into a plastic bag.

8. A method of making reclosable plastic bags, comprising: moving a continuous fastener along a predetermined path; severing the fastener at a station along the path to produce adjacent cut ends in the fastener; moving the cut ends of the fastener laterally relative to each other to expose the ends; inserting a slider over one of the exposed ends; and after inserting the slider over one of the exposed ends, attaching the fastener to a continuous web of plastic bag material.

9. The method of claim 8, further including the steps of forming side seals in the bag material and severing the bag material from the remaining continuous web.

10. The method of claim 8, wherein the fastener includes first and second opposing tracks, the first track including a rib-type element, the second track including a groove-type element adapted to interlock with the rib-type element, wherein the step of severing the fastener includes severing only a portion of the first and second tracks, including the rib-type and groove-type elements, so that sections of the fastener on opposite sides of the cut ends remain connected.

11. The method of claim 8, wherein the first and second tracks are joined to each other along a predetermined area of weakness to effectively create a single fin comprised of the pair of fins.

12. The method of claim 8, further including the step of forming the continuous web of plastic bag material into a plastic bag.

13. A bag-making apparatus, comprising : means for periodically severing a fastener to produce adjacent cut ends in the fastener; means for moving the cut ends of the fastener laterally relative to each other to expose the ends; means for inserting a slider over one of the exposed ends; and means, downstream from the insertion means, for attaching the fastener to a continuous web of plastic bag material.

14. The apparatus of claim 13, further including means for forming side seals in the bag material and severing the bag material from the remaining continuous web.

15. The apparatus of claim 13 , wherein the means for periodically severing the fastener includes a pair of reciprocating knives.

16. The apparatus of claim 15, wherein the means for moving the cut ends of the fastener includes the pair of reciprocating knives.

17. The apparatus of claim 13 , wherein the means for attaching the fastener includes sealing members that apply heat.