US3779139A

US3779139A - Method of forming plastic bag with integral tie

Info

Publication number: US3779139A
Application number: US00226710A
Authority: US
Inventors: D White
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1972-02-16
Filing date: 1972-02-16
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18
Also published as: CA976013A; DE2249584A1; BE792014A

Abstract

A plastic film web is perforated and sealed at the open end of a bag to provide an integral tear strip portion of the bag material which can later be either wholly or partially detached for use as a closure tie.

Description

United States Patent [191 White Dec. 18, 1973 PLASTIC BAG WITH INTEGRAL TIE AND METHOD OF FORMING SAME [75] Inventor: Daniel A. White, Green Bay, Wis.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Feb. 16, 1972 [21] Appl. No.: 226,710

[52] US. Cl 93/35 VL, 93/1 TS, 93/35 DS, 93/33 H [51] Int. Cl B31b 1/90, B3lb 49/04 [58] Field of Search 93/35 R, 35 DS, 35 VL, 93/1 TS, 33 H, 35 H, 58 P [56] References Cited UNITED STATES PATENTS Peterson 93/35 R 3,567,074 3/1971 Brown 93/1 TS 3,411,419 11/1968 Becker et al.... 93/19 X 3,283,672 11/1966 Mueller 93/1 TS X 3,579,397 5/1971 Schwarzkopf.. 93/1 TS 2,643,049 6/1953 Barelt 93/35 R X 3,568,576 3/1971 Lehmacher et a1 93/33 H Primary Examiner-Andrew R. Julhasz Assistant Examiner.lames F. Coan Attorney-F. W. Anderson et a1.

[ 5 7 ABSTRACT A plastic film web is perforated and sealed at the open end of a bag to provide an integrall tear strip portion of the bag material which can later be either wholly or partially detached for use as a closure tie.

4 Claims, 15 Drawing; Figures PATENTED DEC! 81375 SHEU 1 [IF 3 PLASTIC BAG WITH INTEGRAL TIE AND METHOD OF FORMING SAME BACKGROUND OF THE INVENTION The field of the present invention concerns plastic film bags. Relatively recent convenience products for residential and other users are a wide variety of inexpensive plastic film bags intended for limited or onetime use. Among these, at present, are large trash bags or trash can liners which are usually packaged with loose tying devices such as paper or plastic covered wire ties for closing the throat of the bag after filling. The ties must be separately manufactured, handled and counted, and can easily be dislodged from the packaged bags and lost, and for these reasons are less than satisfactory both to the manufacturer and the consumer. Moreover, the ties increase the cost to the consumer since they are separately produced and handled. A further disadvantage in separate ties is that even after a tie has been placed on a bag, it can easily become detached and allow the bag to open or spill.

SUMMARY OF THE INVENTION By perforating the margin of a bag around the open end during its production, a separable tear strip formed of the bag material is later readily freed for use as a closure tie. Thus the tie and the bag are formed, handled and packed as a unit to eliminate the inherent disadvantages of separate bags and closure ties, and can be produced at rates as high as are now attained for ordinary bags requiring separate ties. The tear strip tie can be made either entirely or partially separable, and can be either single ply, multi-ply, or a reinforced form of either.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevation of a bag making machine adapted to carry out the bag forming method and to produce the bag article of the present invention.

FIG. 2 is an enlarged schematic elevation including a sealing and perforating mechanism at the inlet end of the bag machine shown in FIG. 1. i I

FIG. 3 is an enlarged schematic elevation of a selectively operable perforating mechanismshown in FIG. 1.

FIG. 4 is a schematic perspective of the FIG. 2 perforating mechanism.

FIG. 5 is a schematic perspective of a web sealing and severing station of the bag machine.

FIG. 6 is a schematic isometric of one embodiment of a completed bag.

FIG. 7 is a schematic perspective of the FIG. 6 bag after filling and tying.

FIGS. 8-15 are schematic perspectives of further embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a known type of bag making machine 20, which. in the present case is arranged to heat seal and sever a prefolded film web W supplied from a roll R. The web W is supplied longitudinally folded so that one edge is slightly spaced from the other edge, in the form known, due to this type of fold, as J-stock. When the foldedweb is eventually sealed and severed across its width, two adjacent sealing and severing operations produce one bag known as a side-weld bag because the sealed and severed portions extend along the side margins of the completed bag.

Driven draw rolls at 22 continuously pull the web W from the roll R and past a folding station 24 at which one narrow edge portion of the web is doubled to make two plies, or in certain instances, several plies. Beyond the draw rolls, the web is trained around an anvil roll 26 at a selectively operable sealing and perforating station 28 where the double plies are sealed together and the adjacent single ply is perforated so that the doubled edge portion can later be torn from the remaining web in a completed bag.

Because the web feed downstream of the perforating station 28 is intermittent, the web is trained through a conventional dancer roll assembly 30 which operates to automatically accumulate and pay out the web according to the web requirements downstream of the dancer roll assembly. The next station is a selectively operable intermittent perforating station 32 which is used only when the perforating mechanism of the sealing and perforating station 28 is inactive.

The intermittent perforating station 32 produces in terrupted bag perforations, whereas the station 28 produces continuous perforations. As previously indicated, continuous perforations provide a removable tear strip, while the interrupted perforations retain the tear strip attached to the body of the bag. In some instances where the tear strip includes more than one ply, selected portions of the tear strip can be consolidated by a spot-sealing operation at a sealing station 34, following which the web passes through the intermittent feed rolls at 36, and a sealing and severing station at 38 where the side margins of the bag are simultaneously sealed and severed from the web. A conveying section at 40 then transfers the finished bags onto a stacking table 42 where they are assembled into stacks and are subsequently removed for packaging or other handling. Those stations of the bag machine 20 which differ from a conventional bag machine are

stations

24, 28, 32 and 34, as will presently be described. 1

With more specific reference to both an exemplary form of the bag and to the apparatus for producing the bag, reference is made to FIGS. 4 7. The prefolded web W adjacent the draw rolls 122 includes a lower panel 44 and a narrower upper panel 46. At the folding station 24 the exposed edge 48 of the lower panel 46 is guided through a stationary folding shoe 50 (FIG. 2) which functions to fold back a narrow hem or skirt 52 which ultimately becomes one edge of the open end of a bag B, as clearly shown in FIG. 6. The folding shoe 50 is actually the hemming attachment of a conventional household sewing machine, and functions in the usual manner, whereby according to the width of the margin of material run through the attachment, either a single fold of U-shape section will be formed, or a double fold having the edge of the material disposed within the confines of a U-shaped fold.

Again referring to FIG. 4, the sltirt 52 on the folded edge of the web passes around the anvil roll 26 and under a cooperating perforating wheel 54 to form a linear series of spaced perforations at 56 between the previously identified edge 48 of the web panel 46, and an edge 58 of the web panel 44, and through both the skirt 52 and the web panel 46. At the same time the perforations are made, an electrically energized sealing bar 60 continuously heat-seals the skirt 52 to the web panel 46. An air cylinder 62 carries the sealing bar 60 so that the sealing bar can be removed from the web when the machine is idle, or when a later described optional procedure is used and no longitudinal sealing operation is required. Thus folded, heat-sealed, and made separable from the remainder of the web, the skirt 52 now forms a removable tear strip TS when the web is later transversely sealed and severed.

When producing the bag B shown in FIGS. 6 and 7, the only remaining operation is the sealing and severing of the web W (FIG. by a conventional heated sealing bar 64 which is actuated each time the feed rolls 36 (FIG. 1) have advanced one bag length of web, and the web is static. None of the described folding, sealing and perforating operations interrupt progress of the web, because each is a continuous operation. For this reason, the production rates of the bag machine are substantially as high as have formerly been attained. Moreover, the tear strip TS is an integral part of the bag having the same handling characteristics as the body of the bag, and the bags B can therefore be handled in stacking and packing operations with the same procedures presently in use. In contrast to present bags, however, the bag B now has a readily separable closure the tear strip TS which cannot be accidentally dislodged, lost or misplaced, and which is ready for immediate use when needed.

, FIGS. 8-15 disclose some of the numerous possible other embodiments of the bag and bag forming method of the present invention, the structural means for effecting the same being the same elements already described, plus a spot-sealer 66 (FIG. 1) at the sealing station 34, and a skip-perforator 68 (FIG. 3), at the perforating station 32, which is used in lieu of the mechanism at the perforating station 28.

FIG. 8 illustrates a bag B1 which is similar to the bag B but has a single ply, only, in its tear strip TS, thus being formed wihtout use of the folding shoe 50, and being a suitable construction for a light duty bag, or for a bag of one of the stronger film materials. It will be understood that in FIG. 8, as well as in FIGS. 9-15, the side margins of the bag are shown open in order to clearly illustrate the plies, and that in actuality these margins are sealed together by a sealing bar 64 at station 38 as each bag is severed from the upstream web portion.

FIG. 9 depicts a bag construction for a bag B2 in which the tear strip TS comprises a once folded web portion, as in the bag B, but wherein the arcuate sealing bar 60 (FIG. 4) is retracted by the air cylinder 62 to eliminate the longitudinal seal through the tear strip. In place of that type of seal, the spot-sealer 66 produces two spaced area seals, indicated by shaded areas at 70, which secure the two plies together at the ends of the tear strip and thus preserve the dual ply construction. Since the actual length of a tear strip in a trash can liner might be two feet or more, it is apparent that the central portion of the tear strip can easily be opened flat, if desired, so as to provide a wide wrap around the throat of the ba g. bag.

The FIG. 10 bag B3 is comparable to the bag B, with an additional folding step which may be accomplished by repositioning the folding shoe 50. As previously mentioned the width of material run through the folding shoe determines the type of fold. Thus, when the margin is about 94 inch, a 1% inch fold is made, plus a V4 inch return fold. This produces three plies through part of the folded margin. It might also be possible to use a different folding shoe to produce a similar but four ply fold in the form of a flattened helix. In either event, the arcuate sealing shoe 60 is used to interconnect all plies with a longitudinal seal through the tear strip TS, and the thus produced tear strip provides a stronger than usual tie for the bag.

Bags B4-B6 (FIGS. l113) all have single ply tear strips TS, and are formed by inactivating or removing the folding shoe 50 (FIG. 4), the perforating wheel 54, the sealing shoe 60, and the spot sealer 66 (FIG. 1), and by use of the skip-perforator 68 (FIGS. 1-3). As best shown in FIG. 3, the skip-perforator includes

rollers

72, 74 for guiding the web W around an anvil roll 76. A perforator wheel 78 is carried by a pivot arm 80 for selective engagement with the web by means of a power cylinder 82. Automatic, programmed operation of the perforator wheel for producing a preselected pattern of perforations may be effected in different ways, a preferred way (not shown) being a camoperated valve timed to the operation of the bag machine 20 for energizing and deenergizing the power cylinder 82.

A common feature of the bags 84-36 is that the perforations 56 of the tear strip TS in each case is interrupted so that the tear strip has a major portion separable from the bag, but remains connected to the bag at one or more points. By this means, the tear strip retains its closure utility, as intended, but cannot slip off the bag when it is wrapped and tied around the throat of the bag. Thus, in FIG. 11 the bag B4 is provided with a tear strip TS having opposed free end portions v84 centrally interrupted and thereby connected to the bag panel 46. In FIG. 12 the bag B5 has an attached tear strip TS with only one free end 86, whereas the tear strip of the bag B6 (FIG. 13) has no free ends.

The bag B7 (FIG. 14) is provided with a two ply tear strip TS which has no free ends and is produced by use of the folding shoe 50 (FIG. 4) to form the double ply, and by use of the spot-sealer 66 (FIG. 1) to bond the two plies together with area seals at 88. By means of area seals (FIG. 15) and non-interrupted perforations 56, the tear strip TS of the bag B8 is especially adapted for initial use as a handle, and for possible eventual use as a closure tie. While the perforations 56 (which extend only through the bag panel 46) may be interrupted to stop short of the side margins of the bag, an advantage of the FIG. 15 construction is that it eliminates the more elaborate mechanism for skipperforating.

From the preceding description, it is believed evident that the disclosed bags and bag forming method represent a marked improvement over bags of the separate closure-tie type, in that the ties are integral with the bags, cannot be lost, andare capable of being simultaneously produced at less cost than separate closure ties. Further, the conventional handling operations used for ordinary bags are not affected by the integral closure ties, and there are no separate handling steps required for the ties.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

I claim:

1. A bag forming method comprising the steps of moving a longitudinally folded web along a predetermined path, longitudinally perforating the entire bag near the upper longitudinal edge thereof, and transversely severing and sealing said web at spaced intervals to form one bag with two successive severing and sealing operations, the marginal portion of the perforated ply providing a tear strip at least partially separable from the thus formed bag for use as a closure tie, said perforating step producing interrupted perforations for leaving a part of said tear strip inseparable from the bag.

2. A bag forming method comprising the steps of moving a longitudinally folded web along a predetermined path, longitudinally perforating the entire bag near the upper longitudinal edge thereof, and transversely severing and sealing said web at spaced intervals to form one bag with two successive severing and sealing operations, the marginal portion of the perforated ply providing a tear strip at least partially separable from the thus formed bag for use as a closure tie, folding the marginal edge portion of the ply which ultimately forms said tear strip to make a double ply, and sealing said double plies together to form a double strength tear strip in the completed bag.

3. The method of claim 2, wherein said sealing step longitudinally seals said tear strip plies.

4. A bag forming method comprising the steps of moving a longitudinally folded web of J-stock along a predetermined path, folding the marginal edge portion of the wider ply which ultimately forms said tear strip to form a double ply, sealing each end portion of said double plies together, longitudinally perforating the wider ply near the upper longitudinal edge of the narrower ply to form a tear strip, and transversely severing and sealing said web at spaced intervals to form one bag with two successive severing and sealing operations, the marginal portion of the perforated wider ply providing a double thickness tear strip at least partially separable from the thus formed bag for use as a closure are w =r

Claims

4. A bag forming method comprising the steps of moving a longitudinally folded web of J-stock along a predetermined path, folding the marginal edge portion of the wider ply which ultimately forms said tear strip to form a double ply, Sealing each end portion of said double plies together, longitudinally perforating the wider ply near the upper longitudinal edge of the narrower ply to form a tear strip, and transversely severing and sealing said web at spaced intervals to form one bag with two successive severing and sealing operations, the marginal portion of the perforated wider ply providing a double thickness tear strip at least partially separable from the thus formed bag for use as a closure tie.