Method And Apparatus For Manufacturing Bag Stock

Abstract

Method and apparatus for fitting together multiple pairs of interlocking beadlike closure members of a type extending continuously at the inside of tubular film while the film is moving such as during its manufacture, and at a rate accommodating at least the maximum extrusion speed of the film. Such apparatus can comprise a forward slitting station adapted to receive the tubular film in a flattened condition, separate it, and strategically slit the same for use as bagmaking stock; and thereafter to controllably direct the film to a mandrellike member including guide means such as, for example, grooves or the like. The latter align the pairs of closure members, respectively, to cooperatively assist subsequent fitting of the pairs together such as by application of external pressure. Such method and apparatus effectively overcomes problems relating to irregularities in the lateral spacing between the closure pairs.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to improved methods and apparatus for simultaneous fitting together multiple pairs of interlocking closure members of a type extending continuously at the inside of tubular film, while the film is moving, and at speeds at least as great as the film extrusion or manufacturing speed. More particularly, the invention relates to such methods and apparatus which can be placed "in line" with film extrusion apparatus, and which in cooperation therewith desirably provides bagmaking stock requiring, for example, only intermittent sealing or cross-sealing to complete a desired bag structure.

2. Discussion of the Prior Art

Plastic bags are oftentimes desirably provided with frictionally interfitting or interlocking closure members of a variety adapted to permit the bag to be repeatedly opened and closed. Such closure can be in the form, for example, of opposed beadlike locking members, one a male and the other a female, which fit together sufficiently tight to effect a substantially liquid and gastight closure of the bag. Exemplary of such closures are those set forth in U.S. Pat. Nos. 2,666,466; 2,789,609; 3,988,288; and 3,246,672.

Closures of the indicated type are advantageously coextruded or simultaneously extruded with tubular film material, oftentimes most economically in multiple pairs, as is shown in U.S. Pat. No. 3,291,177. It is normally required that such closure members be fitted together prior to bag making.

Prior art methods for joining or fitting together such closures have oftentimes employed a device termed a "floating" mandrel. Such a mandrel is adapted to be carried within the tubing and includes grooves on opposed faces thereof to precisely align the closure member pairs over each other. The aligned closures are subsequently fitted together, as for example, by external pressure applied such as by squeeze rolls or the like. While frequently used in the past, a floating mandrel is disadvantageously limited in the speed at which the film can be run, that is, its manufacturing speed or rate. At high manufacturing speeds, for example, the mandrel has a tendency to be carried forward by the moving film, and caused to pinch against the indicated squeeze rolls or like means which engage the film from the outside at a region slightly ahead of the mandrel. Film pinched between the mandrel and squeeze rolls can be damaged to an extent that ruins its use for subsequent bag fabrication. Such apparatus, moreover, is ill-adapted for joining together multiple pairs of closure members. For example, frequently it happens that the lateral spacing between adjacent closure members on one face of the film is more or less than the lateral spacing between the corresponding or opposed closure members on the opposite film face. Thus, when one or a first pair of closure members is aligned precisely over each other in aligning grooves, for example alignment of the second pair is difficult. In other words, the separate closure members comprising the second pair are frequently laterally positioned different distances from closure members comprising the first pair, respectively, and therefore are "offset" to a degree frequently making their precise alignment difficult. Specifically, the adjacent closure members of least spacing therebetween have a tendency to laterally "tug" at each when forced into separate aligning grooves, respectively, with resultant tendancy of one or more of the closures to leave its groove, thereby disrupting the process.

Joining apparatus also has been provided comprising a fixed mandrel including aligning grooves, and with the additional provision of a knife located at the connection between the mandrel and the forward edge of its fixed support. The knife is thus adapted to slit the film longitudinally as it passes over the mandrel. By mounting the mandrel in place, bruising or tearing of the film in high-speed film manufacturing is effectively eliminated. However, in instances of simulaneously joining multiple pairs of closure members, difficulties of an above-identified type are encountered in that even if one closure pair can be precisely aligned, the second may be "offset" and therefore troublesome to align properly.

Accordingly, it is among the objects of the present invention to provide the following:

Apparatus for continuously and simultaneously joining together multiple pairs of closure members of a type positioned at the inside of tubular film material, and while the film is moving such as during its manufacture,

Such apparatus wherein the same operates reliably regardless of nonprecise tolerances in the lateral spacing between the closure members;

Apparatus of the type indicated wherein the same is cooperatively operable "in line" with the extrusion apparatus manufacturing the film, and wherein the joining apparatus is adapted to receive the film in a flattened condition, separate it, and thereafter accurately and strategically slit the same for use in bagmaking stock; and generally simultaneously with slitting to reliably lock such closure members together at a rate accommodating film manufacturing speed; and

Such apparatus adapted to slit the film longitudinally into continuously extending separable parts, each suitable for use as bagmaking stock, and wherein the closure member pair on one such part is directed to a fixed guide means for aligning and fitting together of the pair; while the closure member pair on another such separable part is directed to and permitted to "seek" from amongst a plurality of guide means, the guide means most strategically positioned to receive the pair for alignment.

BRIEF SUMMARY OF THE INVENTION

Briefly then, the present invention contemplates improved methods and apparatus for joining together multiple pairs of closure members of a type, for example, extending continuously at the inside surface of tubularly extruded film. Such apparatus is advantageously set up "in line" with the apparatus manufacturing the film, and includes a film guide station adapted to receive the film in a flattened condition and controllably direct the same to a film-slitting station. The latter continuously slits the film in the longitudinal direction for use as bagmaking stock. A probe member desirably separates the film just prior to slitting whereby "offset" cuts can be made for subsequent fabrication of the film into lip bags; that is, bags having an offset or grasping lip to enable convenient bag opening. The film after slitting is controllably directed over a mandrellike member including a plurality of guide means or sets of grooves strategically positioned to precisely align the closure pairs, respectively. Nip or squeeze rolls, for example, can be employed to assist the aligning grooves to continuously fit together the respective closure pairs by applying pressure externally thereon. Most optimally, the film is slit longitudinally into separable continuously extending parts prior to the indicated closure member aligning and fitting together operations. Each of such parts is usable for bag fabrication, as will be explained more fully hereinafter.

The preferred embodiment of the present invention is shown in the accompanying drawings wherein wheresoever possible like reference numerals designate corresponding material and parts throughout the several views thereof in which:

FIG. 1 is a diagrammatic and schematic representation of apparatus receiving tubular film for simultaneously joining together multiple pairs of closure members, respectively, located continuously at the inside of the film, such apparatus being constructed according to the principles of the present invention;

FIGS. 2-6 are enlarged fragmentary cross-sectional views taken along reference lines 2--2, 3--3, 4--4, 5--5 and 6--6, respectively, of FIG. 1; and

FIG. 7 is a front elevational view of film edge control rolls of a type desirably employed in combination with the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Looking now with more particularity at the drawings, there is shown at FIGS. 1 and 2 apparatus 10 receiving tubular film 12; the film, for example, having been freshly extruded and delivered in flattened condition from a conventional extrusion assembly (not shown). Located continuously at the inner surface of film 12 are first and second pairs of interfittable or interlockable closure members 14 and 16 (see FIG. 2). Pairs 14 and 16 each normally comprise first elements 18 and 20, respectively, residing on one face 22 of the flattened film; and interfittable with second elements 24 and 26 located opposite thereto on the opposed film face 28. Techniques and apparatus for manufacturing film of the type indicated are illustrated in some detail, for example, in U.S. Pat. Nos. 3,291,177 and 3,371,696.

Referring now specifically to apparatus 10, the same comprises a film guide station 30 adapted to initially receive film 12 and controllably direct the same to a slitting station indicated at 32. Set downwardly a spaced distance from station 32 is a joining station 34 adapted to continuously fit closure member pairs 14 and 16 together.

Guide station 30 can comprise a pair of freely rotatable wheels or film guide means 36 and 38 supported in place such as by conventional yoke and bearing assembly (not shown). Wheels 36 and 38, at their surfaces of curvature, define peripherally continuous tracking grooves 40 and 42, respectively, cooperatively facing each other, as is best shown in FIG. 3; and adapted to engage the first closure pair 14 therebetween to assist controlled feeding of the film to the slitting station, as will be explained more fully hereinafter.

Slitting station 32 is desirably positioned a spaced distance downwardly from wheels 36 and 38. The same can comprise a relatively thin, flat part 44 disposed approximately normal to the plane of moving film 12 (see FIG. 4) and which is rigidly fixed in place such as by attachment to a stationary frame piece as is denoted generally at 45. Part 44, at its film-receiving or forwardmost end 47 defines spaced-apart depressed regions or cutouts 46 and 48 opening toward the direction of film movement, and separated by an elongated probe or film-separating means 50. Laterally positioned on each side of probe 50, across depressed regions 46 and 48, are flat planer aligned part sections 52 and 54, respectively. Sections 52 and 54 ultimately rigidly merge together with probe 50 adjacent lower extent 56 of part 44.

Cutting means or blades 58 and 60 are rigidly attached to opposed faces 62 and 64, respectively, of sections 52 and 54 such as, for example, by suitable clamping assemblies or like affixing means (not shown). The cutting edges 68 and 70 of the blades are directed diagonally downwardly, with respect to the direction of film 12 movement, and extend from a midregion portion of sections 52 and 54 across depressed regions 46 and 48, respectively. Thereafter the blades terminate approximately adjacent the center part of probe 50 as is denoted at 73 and 75. The "offset" positioning of the blades is best shown in FIG. 4, and is designated therein by letter "X" which represents approximately the thickness of probe 50.

Joining station 34 is positioned normal to part 44 (see FIGS. 1 and 5) and comprises a mandrel 74 of desirably relatively flat rectangular configuration, whereby the same defines generally flat, opposed surfaces 76 and 78, respectively. Mandrel 74 is positioned substantially in planar alignment with the moving film, and is held rigid such as by a stationary mounting arm 80 attached to the midregion of surface 78. Surfaces 76 and 78 cooperately define a plurality of guide means or groove sets (see FIG. 5) each comprising a first groove 82 located on first surface 76 and precisely aligned with a second groove 84 positioned opposite thereto on second surface 78. One such groove set designated as A is located to the left of arm 80 in substantially direct alignment with tracking grooves 40 and 42 at guide station 30. A plurality of such groove sets designated as B, C and D are strategically positioned to the right of arm 80 at spaced lateral distances from each other, and for purposes as will become more evident hereinafter.

OPERATION

In operation, moving film 12 is initially received at film guide station 30 where tracking grooves 40 and 42 assist each other to continuously engage therebetween first closure pair 14 from the outside of the film (see FIG. 3). The position of closure pair 14 is thereby established or continuously "tracked" to enable controlled guidance of the film to slitting station 32. At the slitting station, probe means 50 operates to separate film faces 22 and 28 at a region between closure pairs 14 and 16 (see FIG. 2). The film in its separated condition is then delivered to cutting blades 58 and 60 and cuts made between adjacent closure parts on panels 22 and 28, respectively, as is denoted at 86 and 88 in FIG. 4. Probe 50 cooperatively assisted by tracking grooves 40 and 42 enables precise "offset" cutting of the film. That is, a cut located closer to one closure element than the other. Film 12 is thus separated to two parts 90 and 92, as is best shown in FIGS. 5 and 6, each such part including an offset lip portion at 94 and 96, respectively. The extent of the offset portions 94 and 96, as is indicated by Y (see FIG. 6) is approximately equal to the thickness of probe 50 and, thus, is readily controlled to meet desired bag lip specifications such as by adjusting or controlling the thickness dimension X of the probe. Moreover, by staggering the male and female elements on film faces 22 and 28, respectively, as shown in FIG. 1, parts 90 and 92 are identical but are orientated differently or reversely to each other.

Film part 90, after slitting, is separately and controllably delivered to the left side of arm 80 and fed over mandrel 74 where closure elements 20 and 26 are received and precisely aligned over each other in groove set A.

Before and after mandrel 74 are sets of squeeze or nip rolls 98 and 100, respectively. The first set 98 urges the closure elements snugly into groove set A by pressing the same into the grooves; and the second set of rolls 100, in cooperation with groove set A, squeezably forces or fits the closure pair together on a continuous basis.

The second film part 92 is separably directed essentially without precise guidement to right side of mounting arm 74 into the region of the plurality of groove sets B, C and D. The second pair of closure members 16 is initially manually or otherwise assisted to seek or find from amongst the groove sets B, C and D the groove set of most compatible relative positioning thereto. Once in the best groove set, the second closure pair 16 is continuously fitted together assisted by nip rolls 98 and 100, as explained above.

Windup means (not shown) can be located downwardly of station 34 for purposes of continuously winding the finished film parts 90 and 92 on storage rolls for subsequent use as bagmaking stock; or alternately, parts 90 and 92 can be fed directly into bagmaking machinery for direct fabrication into bags. A suitable bag is made by cross-sealing parts 90 and 92 intermittently to comparment the same into connected bag elements. Thereafter the bags are readily separated from each other such as by making cuts along the midregion of each cross-sealed area, respectively. In any event, it is normally desirable to place apparatus 10 between spaced-apart sets of drive rolls (not shown). Optimally, the second set of drive rolls, that is, the drive rolls positioned downwardly of apparatus 10, are driven at a greater speed than the first set, whereby film 12 is placed under tension as it is pulled past the joining apparatus. Otherwise the film has a tendency to "pile up" such as at cutting blades 58 and 60.

As was generally indicated heretofore, it is frequently difficult to manufacture film 12 having precise lateral spacing between closure pairs 14 and 16. Accordingly, oftentimes the respective lateral distances, denoted by Reference Letters Z and W in FIG. 2, are slightly unequal. Resultant tendency, therefore, is for one of the closure pairs to be "offset" when the other is precisely aligned. Simultaneously joining or locking together of the pairs is thus made more difficult, especially at high operating speeds such as in the range of 100-200 feet per second film movement.

Apparatus 10, however, substantially overcomes such problems at maximum film manufacture or extrusion speeds; and with reliable continuous joining together of the pairs, while precisely slitting the film for use as bagmaking stock as explained above.

It is significant to note that in the present invention, therefore, film 12 most optimally is slit into separate parts 90 and 92 prior to precise alignment and fitting or joining together of the closure pairs 14 and 16 such as at joining station 34. More specifically, the first closure pair 14, throughout the process, is guided or "tracked" continuously. First, to controllably direct the film to cutting station 32 such that the cuts at film regions 86 and 88 are precisely positioned, and thereafter to accurately direct the film to joining station 34. The second part 92, however, after leaving cutting station 32 is free to "reposition" itself or be manually repositioned to engage a select one of the sets of grooves B, C and D since it is no longer attached to first part 90. Some mobility for repositioning conceivably could be obtained by slitting the film at just one region prior to joining and fitting together closure pairs 14 and 16. That is, slitting could be limited to region 86 or 88, alternately. Most optimally, however, by slitting at both regions 86 and 88 the film is made ready for immediate bag fabrication; and moreover, possible incurrance of lateral "tugging" between adjacent closure members, as would be possible at the uncut face of the film, is positively avoided. Such tugging can result in one or more of the closure members jumping from the aligning groove.

Referring now to FIG. 7, sets of rolls 102 and 104, respectively, can be desirably employed in combination with apparatus 10. Each such set can comprise a pair of nip engaged rolls (only one shown), normally rubber coated or including rubber jackets comprising their surfaces of curvature 106 and 108, respectively. The roll sets 102 and 104 can be freely rotatable and are designed to engage therebetween film edges 110 and 112, respectively, and thereby exert lateral tension on the film due to the angular position of the roll sets as indicated by .alpha., film 12 movement being indicated by arrow 114. Such roll sets are most desirably placed slightly below tracking station 30, but above cutting blades 58 and 60; and desirably remove wrinkles from film 12 to assist its fabrication into smooth, flat film stock or parts 90 and 92.

Referring now to some of the specifics of the invention, nip rolls 98 and 100 are desirably constructed of polished steel, preferably stainless steel, to minimize any possibility of the same marring the film by contact therewith. Polished stainless steel materials are also desirably used to construct part 44 and mandrel 74. Alternately, the leading surfaces or the film contacting surfaces can be coated with low coefficient of friction material such as polytetrafluoroethylene if desired. Blades 58 and 60 can comprise conventional razor blades or like cutting instruments. The amount of spacing between stations 30, 32 and 34 can vary. Normally it is desirable to position station 30 relatively close to part 44, for example, but with sufficient spacing to permit the film faces 22 and 28 to easily separate at probe 50. For example, a spacing of about 1/2 to 11/2 inches between the probe and nip of wheels 36 and 38 has operated satisfactorily. Part 74 has been found to operate satisfactorily, for example, when spaced approximately 10 to 12 inches from part 44, but has also been operated at approximately 6 inches spacing therebetween. The former range is preferred. Rolls 98 and 100 are desirably closely positioned to mandrel 74. For example, set 98 has been operated with approximately one-fourth inch spacing between the circumference of its rolls, respectively, and mandrel 74; and roll set 100 has operated with a like spacing of approximately one-sixteenth inch. The above values, of course, are given for exemplary purposes only.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. Apparatus for manufacturing bag stock from tubular film material having a plurality of closure members extending continuously in the longitudinal direction on opposed faces of the film, the closure members being of an interlocking variety and forming first and second spaced-apart pairs of such closure members, said apparatus comprising in cooperative combination: means to continuously engage said first closure pair and controllably direct the film to means for slitting at least one of said film faces continuously at a region between said first and second closure pairs and, thereafter, to controllably direct said film to means for continuously aligning the closure members comprising said first and second pairs, respectively, precisely over each other, and means to urge said aligned pairs of closure members into interlocking relationship, respectively.

2. The apparatus of claim 1 wherein said slitting means divides the film into separate first and second parts by continuously slitting said opposed faces, respectively, at a region between said first and second closure pairs, each such part comprising separate bagmaking stock.

3. The apparatus of claim 2 including means to separate said opposed faces prior to slitting the film.

4. The apparatus of claim 3 wherein said slitting means is adapted to slit said opposed faces, respectively, at regions offset from each other, whereby said first and second parts include offset lip portions, respectively.

5. The apparatus of claim 2 wherein first and second aligning means align said first and second pairs, respectively.

6. The apparatus of claim 5 wherein said guide means engages said first closure pair and controllably directs the film to said slitting means and, thereafter, directs said first part to said first aligning means, said guide means and first aligning means being in substantially planar alignment with each other in the longitudinal direction.

7. The apparatus of claim 6 wherein said second part is separably directed to said second aligning means.

8. The apparatus of claim 7 wherein the lateral position of said second aligning means is variable whereby the closure members comprising said second pair can be moved laterally for precise alignment of the same over each other.

9. The apparatus of claim 7 wherein said second aligning means is positioned a sufficient spaced distance downwardly of said slitting means with respect to the direction of film movement, whereby the closure elements comprising said second pair have lateral mobility to be moved laterally after slitting the film, when required, to assist precise alignment of the same over each other at said second aligning means.

10. The apparatus of claim 9 wherein said second aligning means comprise a plurality of groove set means, whereby the closure members comprising said second pair can be directed to the groove set most compatibly positioned with respect to the lateral position of said second closure pair.

11. The apparatus of claim 1 including means to continuously engage the opposite edges of the film to exert lateral tension whereby wrinkles are removed from the film.

12. The apparatus of claim 11 wherein said tensioning means is positioned upwardly of said slitting means with respect to the direction of film movement.

13. Apparatus for manufacturing bag stock from tubular film material having a plurality of closure members extending continuously in the longitudinal direction on opposed faces of the film, the closure members being of an interlocking variety and forming first and second spaced-apart pairs of such closure members, said apparatus comprising in cooperative combination: means to engage said first closure pair and thereby controllably direct the film to a slitting station and, thereafter, to a station for aligning and fitting together said first and second closure pairs, respectively, said slitting station comprising means to separate said film faces at a region between said closure pairs, and means to slit said opposed faces, respectively, in the longitudinal direction and at region between said closure pairs, whereby said film is continuously slit into first and second separable parts including said first and second closure pairs, respectively, said aligning and fitting together station including a first aligning means located substantially in longitudinal planar alignment with said guide means and adapted to align said first pair of closure members precisely over each other, second aligning means laterally spaced from said first means and adapted to align said second closure pair of closure members precisely over each other, and means to urge said closure member pairs into interlocking relationship, respectively.

14. The apparatus of claim 13 wherein said guide means comprises grooves facing each other and adapted to engage said first closure pair therebetween.

15. The apparatus of claim 13 wherein said separating means comprises a probe, and said slitting means comprises cutting edges located on each side of said probe, respectively, and adapted to slit said opposed faces at regions offset from each other, whereby said first and second parts include offset lip portions, respectively.

16. The apparatus of claim 13 wherein the lateral position of said second aligning means is variable whereby the closure members comprising said second pair can be moved laterally for precise alignment of the same over each other.

17. The apparatus of claim 16 wherein said second aligning means comprise a plurality of groove set means, whereby the closure members comprising said second pair can be directed to the groove set most compatibly positioned with respect to the lateral position of said second closure pair.

18. The apparatus of claim 16 wherein said second aligning means is positioned a sufficient spaced distance downwardly of said slitting means with respect to the direction of film movement, whereby the closure elements comprising said second pair have lateral mobility to be moved laterally after slitting the film, when required, to assist precise alignment of the same over each other at said second aligning means.

19. The apparatus of claim 13 including means for laterally tensioning said film at a position upwardly of said slitting means with respect to the direction of film movement.