US2403756A - Sewed bag closure - Google Patents

Description

July 9, 1946. R. E. READ SEWED BAG CLOSURE 2 Sheaets-Sheel'I 1 F11-ed Feb. v 1, 1945 July 9, 1946. Q

R. E. READ SEWED BAG QLOSURE l2 Sheet/s- Sheet 2- .Filed Feb. l, 1943 Patented July 9, 1.946

RobertE; Read,.Savannah, Gfanas'signorv to Union, f

corporation of New Jersey Bag & Paper Corporation, New York,lN. Y., a

Application February 1, 1943, serial No. 474,367

s claims. (01.'2'29-625 This invention relates to paper tubes or bags, and more particularly to closures, therefor.

A typeof paper bag widely used in commerce has Va closure in the formation of Which-a line of stitches is sewed through and across the bagat the closurey end thereof. For bags of 50#.or more capacity, the stitches are usually reinforced to prevent tearing through the paper. This type of closure hasjmany advantages, but Where an airtight or even a fhighly sift-proof closure isnecessary,'stitching, alone Will notsuilce rbecause yof the needle openings.n y f l ,It has -been proposed, heretofore, to fold a tape over the closure end of `the bag and then lmake theline of stitching across ,said end through both the tape and lthe bag. It also has been proposed to rst make the line of stitching across theclosure end of the bag, and then fold and glue a tape uponsaidy endof the bag so as to cover the lstitching. In the firstinstance, the Vneedleholes exeV tend through bothY the bag andthe tape, Aand y Figure 'l-ais a diagram illustrating the steps of mypreferredmethod of manufacturing-bags;

` Figure 1--bY is a diagram-o quence of .bag manufacturing steps;

Figure 1-c is a diagram, inustranng'tne ap.-

plicationof my method to the closing of filled bags; f Y, "fr rFigure l-d is a diagram -illustr'atingfmypreferred. method of formingmy closure on filledbags; v ,Figure 2 illustrates the 'general' principlesnf heating and pressing as applied in my method Figure `3 is a fragmentary perspective `View of one stitched type bag closure embodying the .in`` vention, a portion ofthe reinforcingstrip'being shown unfolded in order'to'more" clearly see'the,

-stithing 1 ,1. Figureglisa,transverse'vertical sectional View whilel siftingv or leakage of'material between' opposed closure end portions of the bag is largely prevented, substantial sifting orleakage does occur through the needle holes. In the second instance, it is necessary to hold Wet glued tape Ain folded position over the closure end of the bag until the substantial'area ofglue can fvset" or dry sufficiently to securethetape on the bag. For4 high ratesof production `this, requires large and expensive machinery, particularly in forming such closures on lledbags whichare subjected to immediate handling. ,v j f i Y Y l An object of this invention'istoprovide away of overcoming the above and other disadvanv tages heretofore encountered in theformation of sewed typev closures forpaper tubesor` bags.` j Another .object is to provide methodscf making I a sewed type paper. tube or bag end closure of my A, These. and other ,objects `will Vappear froin'the following description, and, in order. to morejclea'rly understand the invention reference may -be had to the accompanying: drawings .fornjiingfa vpart .of

this specification and in which: `f

inthe une 4-4 of Figure 3;

,Figures 5,V 6 and '7E re 'views rsimilar toFijgure 4, showingv other stitched type b ag closures ernbodyingthe invention; and j l Figures 8, i9 and 10 are /cross sectional views showing-altpernative` formsof reinforcing strips. n .Although the closureapplied'to the Ymouthof the lilledrbag isusually identical withthe closure applied to the bottom ofthe bag during manu-V facture, -the two c losuresjare formed under very different circumstances and face'extremely Adifferenttreatment. Bag'softhe classV here considered are formed by drawing a number of Webs offpaper into a continuous tube fromwhichconsec'utive` bag lengths f are severed;l vvThese Alaag lengths are, of course, ind flattenedcondition. The

bag lengths are placed on conveyorsl which move them-in the direction Foi.; theirV width, usually while" lying in a horizontal plane.; As-thebag lengths are advanced bythe conveyor a sealing tape is folded over one end, after which the bag end, .carrying the tape with it, passesI through a sewing head. -xIn the prior `art the`r presser `foot of the sewing head acts Vto guide a reinforcing member AWhich `supports kand strengthens the stitching and, ofcourse, lies outside the sealing tape, Thesewingfheadoperates continuously, as does the tape applicator andthe tapereinforcing member, and the linez of stitches yconnect one bag with the next.y After the sewingoperation thebags are cut apart. Y,

. Substantially the .same operation occurs in cles'-y ing thev open mouths of iilledfbagls, :but the conditions under which .the operation?, occurs are radically different. The bag bodyis'jdistended instead of Abeing flat; vitis inthe vertical plane instead ofthe horizontal; the operationis carried out at lower speed and is subject to frequent interruptions. More important yet from the standpoint of effective sealing is the fact that the folded bags are almost immediately handled, as by conveyors or trucks, and are stacked either in Warehouses or freight cars. In the manufacturing process the fiat bags are merely stacked and there is ample time for yany sealing' medium to set without being subject to disturbance of the tape.

My closure is designed so a-s to lend itself to the use of the most efficient methods, both for manufacturing and for the filled bag closing operations. Because the details of the closure are aging high bulk materials such as carbon black,

essential to an understanding of my Vimproved methods of forming the closure, the closure itself will be dealt with rst.

Bags I4, as herein shown, have'walls I, which, for simplicity of illustration, are shown as single thickness. In practice, however, the bags will usually have walls of from 3 to 6 plies. The bags may, of' course, be closed at both ends during manufacture inV which case they would be provided with valves suitably located.

Figures 3 and 4 illustrate thefundamental elements of my improved closure. A bag I4 has its Walls I6 collapsed together at one end. Over these collapsed walls I6 is folded a tape II A layer of thermoplastic lmaterial I2 is interposed between the tape II `and the walls I5. A pair of reinforcing strips 2I and 22 are applied, one on each side fof the tape II and ,a line of stitches 4U i's sewed through the reinforcing strips 2l and 22, the tape II, rthe thermoplastic material vI2 and the wallsIS. The reinforcing tapes 2I and k22 are formed from strips of paper so folded or prepared that a portion of the width of the reinforcing stripis of multi-,ply construction, While the remainder is of single-ply construction. Obviously, however, the requirement is for a differentialof thickness and the so-.called singleply portion might comprise two or more plies. In Figure 3 the single-ply portion is indicatedas 22?.

`Following `theforn-iation .of the line .of `stitches 40, .the single-ply portion 2|2 is folded over the multi-ply portion of the strip 22 so as .to cover the stitches 40 .and is secured in such position by adhesive, preferably of the thermoplastic type. I have referredto the layer -of thermoplastic material' I2 as being interposed between the tape I I and thewalls I5. In practice, however, this layer I2 `will usually be applied as acoating on the tape I'I. "I'n'any event, the material ofthe layer I2`wil1, by'means of heat, be brought toa Vplastic condition 'such that, under pressure, portions of the material I2 will flowto plug or seal the needle hol'e's 4 produced"incident to vthe sewing of the seam 40. In the embodiment 'of the invention shown in Figure 5, the bag I4 has its closure end I5 cov-- ered by tapev I I folded and secured onl said end as above described. In this case, however, no reinforcing y strips are provided. The bag is closed by a line of stitches aoross'the'bag through its Yclosureend I5 and the tape I I. 'One of these stitches is indicated atAI in Figure 5, and atthe closure end of the bag portions of the thermoplastic material I2 are forced into the needle openings to fill and seal. them. This closure has the virtue of economy in .eliminating the reinforcing strips, Lwh'ile at .the same time, by virtue of the thermoplastic material on the sealing tape, it preserves a. very high degree of sift-proofness. Where strength requirements are not severe, as in packthis closure has particular merit.

In the embodiment of the invention shown in Figure 6, the bag I4 has its closure end covered by tape II folded and secured on said end as above described. In this case, only one reinforcing strip 22 is provided. A line of stitches across the bag lthrough 5its.closure gni-'1d I5, the folded tape II, and the reinforcing'strip v22 make up the closure. One of these stitches is indicated at 42 in Figure 6. Portions of the thermoplastic material I2 are forced into the needle openings to close and seal them. This closure probably has the greatest all around utility. The reinforcingstrip supplies strength on the needle side of the stitching, and it is well known in the industry that the looper side of the stitch requires little, if any reinforcement. For almost all uses except those in which the most extreme strength, plus the most extreme tightness of closure is desired, 'this closure will be sufcient.'

In the embodiment of the invention shown in Fig. "7,v the bag vI4 has its closure end covered by tape I 'I folded and secured on said end as above described. In this case, reinforcing strips v2l 'and 22 are applied to both sides" of the folded'tape II. A line ofwstitches is sewed across-the bag through its closure end I5, the folded tape I I, and the reinforcingstrips 2'I and `22. One of these stitches is indicated at 43 in Fig. '7. Portions of the thermoplastic material I2 are forced into the needle openings to close'and seal them. This closure is somewhatV cheaper, both as to costjof material and as to the cost of the closing operation, than is the closure of Fig. 4. This is due to the elimination of the sealingk or covering ply of the reinforcing. strips. It is, however. equally -as strong as the closure of Fig.V 4 and should be usedwherever exceptional strengthis required without a concurrent requirement of exceptional tightness. Y

In Fig. 8 I show a reinforcing stripv 44 having a multi-ply section built up of accordion type folds instead of convolute asin strips 2| and 22. In Fig. 9 I Vshow a reinforcing strip 50 made upof simple laminations 5I. In Fig. l0 I show a laminated strip having a single-ply section made up of laminations 60. t

Any of these reinforcing strips may be formed at the time of use, or maybe suipplied in` preformed condition, Similarly, the strips may be coated or impregnated, or both with thermoplastic material before being formedto the con dition illustrated.

While, ofcourse, the same material could be used both for coating the sealing tape and sealing the last ply of the reinforcingstrip, the optimum characteristics of the material for each particular purpose are rather different and, therefore, the best results will .be obtained by the use of specialized materials The thermoplastic material applied to the sealing tape must vnot only be moisture-proof and hav-e the ability toflow under heat and pressure.. but fundamentally should have .adhesive characteristics, with .the adhesive characteristic enjoying at least equal importance with the qualities of moisture-proofness and flowability. vWith the reinforcing strip, on the other hand, the adhesive quality maybe sacrificed to some extent. Since the material on the sealing tapemay b e fairly plastic at the time the needle goes through it, 'there is some danger o-f gummng and overheating `the needle. This may be overcomeY by mixing a lubricant such -asparaffin with the thermoplastic material on lthef'sealing 1' tape.' Such 'admixtureg howeyerglt'ends'toreducethedef siredadhesive` properties of the material; In the reinforcing strip;howeveniitfis possibletouse f wax or paraffin alone and'fthenedle andthr'ead in Ipassing through the` reinforcing' strip may readily be suiiiciently'lubricatedto dispense with removal ofthelrip cordth'rinforcingistrip on the'loope'r side-may pulldoff carryingwith iiiy 'the looper' stitches andleaving the Vbag ready to .beopened so -far las the" `sewing `is concerned?. When;v as previously described, atapeisvs'ealed notonly overth'elmouth 'AoflA the bag but alsoover thestitches, it precludes-theuscof rth'erigcord and, therefore, loses considerable utilityin the packaging of certain commo'ditiesl' inforcing'iitape its 'that iin overlying the? stitches theL sealingcply of the reinforcingstrip' provides a' lo'ck lwhich,'ir1 the-feveiit` of-the failure' of one ormorestitches, preventsunraveling of theseam Vcurseifaprovided" by. complte sealing onf-'both sides; sealing:- of 'either side `Ricans-"f the re'- vin'forcing'strip supplies `a` very substantial degree ofprotection.; I r-zff* Y isMy-closure is the tomake possible ailier# metically sealedpacka'g'ef for heavy "duty lus'e'j'e'nljoyingthe. strengthV andfadvantage's of theseive' closure.' In short, rfor the useofthisclosurefthc inner ply of a! multieply bag. canllbecoated j-with an impervious Y,thermoplastic Amalterialand:"this material, Yextending' tol the edges 'of `thfe ply,L will engage and' mergewith I the thermoplastic iria-f- -terial applied to the `sealing tapelsofvajs toafv'id any. discontinuity'o'f impervious" surf ace throughf out Ithe entire'- interior` area of! the Ibag. This lis easily accomplished WhereV .the Ltherx'nopla'stic' is appliedto the tape.. in molten condi-tior-i'. Ifl'rtlfie.

tape-is precoatedzandthe 'same :effect :is desired; itv will be necessary eitherd to "reheatthe 'thermo-- plastio'material or to apply -v'asolventpreferably highly volatile, to atleast the centralportion of -the tape soY as to eifect the merger-between kthe impervious material on the tape" andthe imper# vious material on thefinner'surface of the lvinner plyr, 1

rFigs. l-a and l-b are `diagrammatic-representations of methods of forming my [closure which are particularly adapted tothe rhariu'i'acn ture 'of bags as distinguished from-the closing of lled'bags, In each' ofthesecases the treatment or sealtheneedlelholesfin the collapsedfend of: thebag. i AttheA same time,'th'e coating'andffold# ing'foperations should be correlated so` that the thermoplastic material is fluid when the tape first comes' inV contact with the bag mouth. Such yfluidity assures adhesion fbetweenf they tape and the Walls `of the bag. yIt also permits the-thermo-V plastic material' to' engage .thee'dges ofthe bag Walls'and thus; in effect, toplug the /mouth 'of the bag 'The folding operation is carried out. by conventional means comprising" an ordinary guide so shaped 'astoltake the` tape from 'fiat condition and bring it to Ulsliape. condition. 'The bag ends pass through this guide andreceive the .tape

"1 The controlfof ythe thermoplastic'materi'al 'is `basedfonthe` speed of movement of 'the'tape and the vcharacteristics -of the thermoplastic material itself. The lmaterial," whatever: itsv particular characteristics, must be brought rto atempera-z ture such that infr the -timerintervening 'between the? coating: operation andthe engagement offthe ,taped bag mouths: with the `sewing lhead the requisite changer from` fluidity to;v plasticityv Will take;p1a ce;z"'1`he,coating'fshould be' so applied asto'leave the niarginsof'thev sealing tape-free of thermoplastic-material and thus to avoid con# tamination of the exterior ofthe bag :by extrusion.

e' ,Thevzfunctionsl of the sealing tape withits as# sociated thermoplastic material are, first', to prevent egress of the bag contents-between the` Walls Y of thebag; second, to prevent egress 'of thefbag of the sealing 4tape ist based *onLA coating 'the tape with .amolt'en` thermoplastic v just 'before' the tapey out the sewing'foperation after-*the thermoplastic material has cooled-vbelowthe' pointof fluidity but While it is still sufiiciently plastic so thatthe pressure exerted between' the feed-dog Yand -the 'presserfooft of 'the sewing machinewill caus'the thermoplastic-imatrial-ltolflowand thus lto plug contents throughthe'needle'holes; and,` third, to afford a measure of 'reinforcement for thestitches. As was discussed in connection` Wiftl'iFig. 5,*fo'r relatively light loads this reinforcementrfm'ay be suflicient inzitself." At Aanyrate, in theprocesses as'diagrammedin Figs; l-a and l-'b the sealing tape has 'received complete treatment at'the time itleavesthesewing head; Y y -:The primary `functionr 'of th'e' reinforcement strip is purely a contribution ofstrengthi *Bags filled Withpulverulent material, particularly when such material iis relatively' free` flowing; behave much as though the contentswere a, liquid. If awbag thus filled is dropped, thereis a tendency forthe contents to iioW along lines atfrightangles to the direction `'of 'impact and this frequently results in a spreading-"force tending lto separate the bag Walls*` at -the closure;v This 'spreading or separating force is resisted directly by the stitches.

'I'he-threadused in the stitches is o'f small diameter and under shockloading ofthis sort would tend to c'ut through-'the Vsealingv tape 'and the bag Walls. The reinforcing, strip" is intended to resistV this force' and itself to sustain any damage incident to the application of the" force and thereby `to prevent such damage occurring to the bag walls. lThis function has been Well recognized in the 'prior art,- which also recognizes' that the greatest strain occurs on the needle side of the stitch'and lthat the loopergside of the stitch inherently affords" the support of the looper thread to absorb strains `on1thfe"sttch--and to act 'very largely"as"a"reinforcing strip; -For this reason Ait is not always necessary "toprovide extra support'forthelooper side of t'he stitch', avp-oint which has been discussed "heretofore in' 'connectionwith Fig. 6.1 r 1 ff "'So-"'fai2"as `rny'lreiriforcing'fstrip is concerned with Ythe function of f' 'contributing "strength, structure-is important as increasing the efficiency of the job; vThe kmulti-plycharacter" of nay-re'- infrcing' strip 'gives .greater strerigtlffA perfuiit weight of strip Athan A"does "a singlelply reinforcing strip; ,-fo'r'the' same reasonv that a bag made up of .alnumb'er :of relatively light plies has-greater strength than a single-ply bag of the same total basic weight. v

In Figs. lf-a., l-b and l-c the reinforcing strip is supplied as a roll of paper of fairly substantial width. The paper is drawn from the roll and passes through a conventional folder which brings the strip into the condition illustrated at the left side of Fig. 3 or into the condition illustrated in Fig. 8. rIhe folded strip is then guided so as to overlie one or both sides of the sealing tape, with the multi-ply section of the reinforcing strip underlying the line of stitches. The bag then passes through the sewing head, the lneedle of which penetrates not only the bag mouth and the sealing tape, but also the reinforcing strip or strips, as the Y.case may be. If only a single strip is used itwill, of course, always be placed on the needle side of the stitch.

As illustrated in Fig. l-a, the bag then goes through a waxing device which applies molten wax or other suitable thermoplastic material to the reinforcing strip so as to cover the multi-ply portion and the stitches. The bag then encounters a folder of any suitable type which turns up the free edge (2'2 in Fig. 3; 44 in Fig. 8) so as to cover the line of stitches. The reinforcing strip is then subjected to sufficient pressure to cause a firm engagement of the free edge with the thermoplastic material.

In Fig. l-b the strip in the supply roll has already been coated or impregnated with wax or other suitable thermoplastic material. It is folded to the desired form, applied to the bag mouth and sewed through. The free edge of the reinforcing strip is then plowed or folded up so as to cover the line of stitches and the strip is then subjected to 'a combination of heat and pressure which servessimultaneously to soften the thermoplastic material or strip and to bring about rm engagement of the free edge.

In Figs. l-c and l-d the treatment of the sealing tape is altered. Here the tape is supplied already coated'with thermoplastic material. It is folded over the bagimouth and sewed through and is then subjectedv to heat and pressure to soften the thermoplastic material and cause it to flow so as to plug the needle holes in the bag end. This avoids the necessity of maintaining a Vat of molten thermoplastic material for application to the sealing tape. This is a highly desirable feature if the operation of the unit is to be subject to interruptions'which is frequently the case in closing llecl bags. The treatment of the reinforcing strip illustrated in Fig. l-c is precisely the same as that illustrated in Fig. l-a.. In Fig. l-c the waxing of the reinforcing strip, while necessitating the maintenance of a vat of molten wax, serves the purpose of Aproviding pre-heating of the reinforcing strip and thus facilitates the nalheat and pressure stage so far as penetration of the heat to the thermoplastic of the sealing tape is concerned. Where the material used to coat the reinforcing strip is a wax, the objections to interrupted operation are lesssevere than in the case of a thermoplastic which, on cooling, has considerable adhesive properties.

In Fig. l-d I illustrate my method as it may be carried out with the minimum of equipment. Here both the sealing tape and the reinforcing strip are supplied already coated or impregnated with the requisite thermoplastic material. In addition, the reinforcing strip has been preformed to the'condition illustrated in Figs. 8 and l0 and at the-left side of Fig. 3. The sealing tape is folded over the bag mouth, the reinforcing strip is applied alongside and sewing takes place through all the members. The free edge of the reinforcing strip is then plowed or folded so as to cover the stitches and the whole combination is subjected to heat and pressure which simultaneously bring about -sealing of the needle holes inthe bag mouth through flowing of the thermoplastic on the sealing tape and rmly secures the free edge of the reinforcing strip in place-over the stitches.

' As has previously been mentioned, it is possible to supply the reinforcing strip completely vfolded which lwill be convenient in some instances. In such case there would be a folding step between the strip supplied in Fig. l-d and the point at which the strip is applied to the bag. This folding step would simply peel off 'one or two plies of the reinforcing strip and bring the strip into the condition illustrated inv Figs. 3,V 8 and l0.

Naturally, in forming -closures such as illustrated in Fig. 6, all ofthe reinforcing strip plowing or folding steps would be eliminated and the reinforcing strip would consist -simply of a. multiply structure which -c'ould be given the Yconvolute form of Fig. 6, the accordion form ofthe upper portion of Fig. Y8, or the laminated form illustrated in Fig. 9.y

Fig. 2 shows press rolls ylill] and IOI acting upon the closure of Fig. 4. These rolls or equivalent would be Aused at the heating and pressing stations in Figs. 1--b, 1-c and l-d. The rolls may be grooved at H0 and III respectively to equalize the pressure -applied to the reinforcing strip with that applied to the sealing tape.

The application-of heat and pressure after the sewing operation m'ay be lcarried out by means of press rolls, as indicated in Fig. 2, or where the heat must be Vapplied for a considerable time, the closure may be passed Ybetween heated Vcaterpillar treads which would have `the effect of maintaining heat and pressure lfor as long as desired, depending on the speed yof the .bags and the length of the caterpillar. The heat may be applied in any of a number of ways and the heating function may be divorced from the pressure function, that is, the `closures may be preheated and then subjected to pressure while cooling. Where the heat and pressure are combined, `inductive heating of the metallic pressure units will probably be most convenient but where preheatingf is desired, resort may usefully be hadto the use of infra-red light properly focused to supply maximum heat at the depth desired.

In designing-equipment for carrying out the various processes, certain `of the steps which have above Abeen described individually and as occurring in sequence would be performed Wsimultaneously. I do not, therefore, intend to be limited to any particular sequence of steps except as such sequence is expressly made a limitation in the subjoined claims.

What is claimed is:

.1. A paper bag comprising a tube having a collapsed end, a strip of `material folded over said collapsed tube end, a reinforcing-strip overlying said folded over strip, stitching through said reinforcing strip, folded over strip and collapsed tube end, and a portion of said reinforcing strip folded 'and Vadhesively secured over the stitching.

2. A paper bag comprising a tube having a collapsed end, a strip of 'material folded over said collapsed tube end, -a reinforcing strip overlying said folded lover strip, stitching through said reinforcing strip, folded over strip and colsaid collapsed tube end, reinforcing strips overlying said folded over strip, stitching through said reinforcing strips, folded over strip and collapsed tube end, and a portion of said reinforcing strips folded and adhesively secured over the stitchings. Y l

4. A paper bag comprising a tube having a collapsed end, a strip of material coated with thermoplastic material -folded over said collapsed tube, end, a reinforcing strip overlying said folded overV strip, strip, 'folded over strip, thermoplastic material and said collapsed tube end, and a portion of said reinforcing strip folded and adhesively 'secured over the stitching.

5. A methodof making a closure on a collapsed stitching through said reinforcing Vend of a paper tube which includes; folding over said end a strip coated on its inner surface with a plastic adhesive, in fluid state, arranging striplike reinforcing means along ai; least one side of the folded strip, sewing the folded strip, the collapsed end of the tube and a portion of the reinforcing means together along and through the same While the adhesive is still plastic, folding the remainder of the rein-forcing strip over and upon the stitches and causing a part of said plastic material while in a plastic state to flow into the needle openings produced in the complete assembly.

6, A method of making a closure on a collapsed end of a paper tube which includes; folding over said end a strip coated on its inner surface with a plastic adhesive, in fluid state, arranging striplike reinforcing means along at least one side of the folded strip, sewing the folded strip, the collapsed end of the tube and a portion of the reinforcing means together along and through the same While the adhesive is still plastic, folding the remainder of the reinforcing strip over and upon the stitches and applying pressure to force portions-of said needle openings rproduced in the complete assembly. i

` vROBERT E. READ.

plastic material into the

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