US2749966A - Method and apparatus for heat sealing closure tapes to containers - Google Patents

Description

June 12, 1956 R. c. ROETGER 2,749,966

METHOD ANO APPARATUS FOR HEAT sEALING cLosuEE TAPES To CONTAINERS Filed Nov. 12, 1954 s sheets-sheet 1 AENA xl un A' E N INVENTOR.

E CHA RD C IPOETcE/P.

June 12, 1956 R. c. ROETGER METHOD AND APPARATUS FOR HEAT SEALING CLOSURE TAPES TO CONTAINERS Filed NOV. l2, 1954 5 Sheets-Sheet 2 INVENTOR. f/cH/MD C'. ROL-T651?.

June l2, 1956 R. c. ROETGER METHOD AND APPARATUS FOR HEAT SEALING CLOSURE TAPES TO CONTAINERS 5 Sheets-Sheet 3 Filed NOV. l2, 1954 1N V EN TOR.

/P/CHARD CJPQETGEE.

ATTORNEYS.

n; n BY United States Patent() METHOD AND APPARATUS FOR HEAT SEALING CLOSURE TAPES T CONTAINERS Richard C. Roetger, Warrington, Fla., assignor to St. Regis Paper Company, New York, N. Y., a corporation of New York Application November 12, 1954Serial No. 468,383

8 Claims. (Cl. 154-1.6)

This invention relates to fmethodsand apparatus for adhering closure tapes and the like to containers, the invention more particularly being adapted among other possible uses for the application of Vclosure tapes which ,are folded over and applied to the ,end edges at the mouths of bags made of sheet material, for example multiwall paper bags.

It is a common practice to adhere a .folded-over tape `astride ,the end edges of multiwall bags and additionally to secure the closure by the ,use of a sewn seam, the stitches -of which pass .through the tape ,as well as the paper 'walls Aof the bag along a line parallel .to and spaced somewhat from the end edges of the bag. Attempts have .also been made in' various ways vto apply the line of stitching rstand then to ,adhere a tape `astride .the end of the bag in a position to seal not only the end `edges of the bag, but also the stitch holes at ,the line of stitching. But so far as known, all of the various ways which have `heretofore .been proposed for securely sealing with ,tape the ends of bag-s with sewn closures, have had certain recognized shortcomings. For example, one .method has been to Aglue a folded-over tape onto .the end of the bag by adhesives which will dry in due course, but if the sewn seam is thereafter applied, then the needle holes will not be satisfactorily sealed. But if .the glued tape is applied after the sewing, -it will tend to become displaced before the v,gluedries -Or sets. Another common practice has vbeen to `dip the whole end of the .tape .and sewn closure in wax or the like, but .this generally results in a somewhat unsightly appearance and ,the wax may become cracked or abraded away and does .not penetrate well in under the tape to seal same securely .to the bag. Other proposals lhave been made to apply a `folded-over tape, of thermoplastic material for example, and then pass the bag in between a pair of cooperating heated `pressure rollers in .an attempt to press and seal `the tape in position, but this method affords onl-y a momentary opportunity for heating the outside surfaces of the tape and the tape tends to insulate against heating the actual surfaces which should be adhered and sealed together, that is, the outer surface of the paper of the rbag walls and theinner surfaces of the tape.

The present invention Vprovides `a method and `arrange- `ment which satisfactorily overcomes the above-noted difficulties and permits the tape to be very rapidly folded over and securely applied. The invention is particularly well-adapted for efliciently applying a tape, for example of paper, which has on its under surface a vthermoplastic coating, for example of polyethylene. Also the invention is well adapted for applying such a tape to bag ends which have already been closed by a sewn seam so that the tape covers and seals the seam and the needle holes as well as the end edges of the bag, this being accomplished while the bag ends are rapidly moving, for example just `subsequent to passage througha sewing machine. And to insure a securely lbonded `sealing relation between the `thermoplastic coating on the .undersurface of the tape to the :paper of vthe bag ends and to the line of stitching, the

'surfaces of `the lbag ends and of the tape are simultane- Patented June 12, 1956 ICC `pressure accompanied by further heating, if desired, insur- .ing that the tape will b e firmly and permanently bonded in place.

Other objects, features and advantages of the invention will appear from the more detailed description given below, taken in connection with the accompanying drawings Which form a part of this specification.

In the drawings:

Fig. l is a somewhat schematic perspective view of a preferred arrangement of apparatus for carrying out the invention;

Fig. la is a diagram showing an alternative construction for a portion of the apparatus of Fig. l;

Fig. 2 is a sectional View taken substantially along line 2 2 of Fig. l and showing a completed bag closure portion made according to a preferred embodiment of the invention;

Fig. 3 is a vertical sectional View of a heated pressure roll arrangement for finally applying heat and pressure to the folded-over tape on the bag ends;

Fig. 4 is another perspective view of a preferred embodiment of the invention, showing in further detail the means for folding-over and placing the tape in position on the advancing bag ends and for simultaneously heating both the tape and the bag ends before same come into Contact;

Fig. 5 is a plan View of the tape folding and heating arrangement, showing the closure tape and bag ends advancing therethrough;

Fig. 6 is an elevational view of the parts shown in Fig. 5; and

Figs. 7, 8 and 9 respectively are vertical sectional views taken substantially along lines 77, 8 3, and 9-9 of Fig. 6.

Referring tothe drawings in further detail, a plurality of ilat multiwall paper bag ends as at l are shown ,in Fig. l, the bags being advanced as by conventional conveying apparatus (not shown) first past a sewing machine at 12, then through an electrical heating means at 13 and nally after application of the closure tape thereto, between pairs of pressure rollers as at ld, l5. As appears in Fig. l, the heating means 13 is shown covered by a guard plate 13a, which may, for example, be formed of a transparent sheet of plastic material. As the bag ends advance following the sewing head which closes the ends by a sewn seam lo, closure tape as indicated at 1/ is simultaneously drawn from a roll ld thereof over a guide roll as at i9 into the heating means 13, which is hereinafter described in detail, and in which the tape is also simultaneously folded over astride the bag ends. The

tape may, for example, comprise kraft paper, either creped or in flat form, having its inner surface as at la coated with thermoplastic material such as polyethylene, although other thermoplastics having generally similar heat sensitive characteristics may be used.

In passing through the heating means at 13, as hereinafter explained, both the bag end surfaces and the tape surfaces are directly subjected to a relatively high tein` However, it has been found that if the bags, as well as the tape, are rapidly advanced, say at a speed of the order of from about 450 to 900 inches per minute, and preferably at a speed which corresponds to the usual sewing machine speed, then the thermoplastic coating and the paper of the bags to which it is to adhere, will be quickly brought up to the necessary temperature, whereby the plastic will firmly stick to the paper when same are brought into contact, yet without danger of charring or injuring either the thread, plastic or paper. As the bag ends leave the heating means 13, the folded-over tape will be positioned astride same and possibly somewhat loosely covering the area of the sewn seam, but the parts will not be firmly compacted together and the sticky plastic will not have become set. Thus when the bag closures pass on between the pairs of pressure rollers 14, 15, the tape areas may be firmly pressed against the paper bag end surfaces and become properly located in permanent position to embrace and cover the sewn seam, without danger of splitting or tearing the tape along the line where it has to bulge somewhat to accommodate the sewn searn therein.

The pressure rolls 14 are preferably heated, as for example by internal electrical heating means as hereinafter described, and so as to insure that the tape will not be forced into its nal place upon the sewn seam before the plastic sets, which setting would tend to prevent proper shaping and positioning of the tape upon the seam without overstraining the tape. While a second pair of pressure rollers is indicated at 15, in some cases these may not be required, and usually they need not be heated, unless desired. If they are relatively cold, they will tend to cool the tape and cause the plastic to set at the moment during which it receives its final pressure against the bag ends. Heavy bags of many plies may accumulate suicient heat to prevent thorough setting of the plastic by the time they have passed between the pressure rollers 15, and then because of exing or other disturbance of the bags, the tape might be disturbed or displaced from proper position. In such cases, to prevent this, the taped bag ends may be squeezed between endless belts, tapes, chains or the like, as somewhat schematically indicated at 15a in Fig. 1a, one pair of such belts or the like being placed above the path of the bags at each side of the sewn seam and another pair being similarly placed below the path of the bags. Such belts or the like may have stretches extending for example from six to thirty inches in contact with the bags to insure adequate cooling before the taped bag ends are released therefrom. To insure a substantially uniform and sufcient pressure of the belts or the like against the bag ends, same may be urged against the bag ends by spring loaded shoes or the like as indicated at 15b. When such belts are used as shown in Fig. l, the pressure rollers 15 may be omitted, but preferably the rollers 14 are used as indicated in Fig. 1a.

While as above explained, so long as the bags and the tape are moving rapidly through the machine same Will not be injured by the heating means 13, yet if for any reason it is necessary to stop the machine, suitable provisions should be made for either manually or automatically disconnecting the heating current to the heating means 13 and to the heated pressure rollers; and to further insure prompt cooling, jets may be provided such as indicated at for projecting blasts of cooling air into the heating means 13 and also if desired, of course, onto the heated rollers. In Fig. 1 such jets are shown only for the upper side of the heating means 13, but it will be understood that the parts of these heating means which are below the bag ends may be similarly cooled by jets when the operation of the machine is interrupted. The air jets may be turned on manually or automatically at the time the machine is stopped and the heating currents shut olf.

As shown, in Fig. 2, the finished bag closure or end may include the multiple layers of paper 22 forming the side walls of the bag end, secured together by the sewn seam 16 and covered by the folded-over tape 17 bearing on its undersurface the thermoplastic coating 17a securely sealed to the outer surfaces of the paper layers 22 and closely embracing, covering and sealing the line of stitching as indicated at 23.

Each of the pairs of pressure rollers, as indicated at 14a, 14b in Fig. 3, is preferably formed with a peripheral groove as at 23a to provide clearance for the central portion of the applied closure tape where the tape bulges over the sewn seam. Thus the remaining peripheral surface areas of these rollers are free to press the tape firmly against the bag ends. One of each of these pairs of rollers, preferably the upper one as shown in each case, is springpressed, same being supported by bearing means as at 24, pivoted as at 25 (Fig. l) and with the bearing means arranged to be pressed downwardly as by a spring 26. These rollers may be driven as by gears 27, 28 and 29. Each roller may have mounted internally thereof a suitable circumferentially extending electrical heating resistance 30, connected as by wires 31 positioned internally of the roller shaft to slip ring means as at 32, engaged by contacts 33 connected to a suitable source of current. It will be understood that the pressure rollers 15 may be constructed in the same way as pressure rollers 14 except preferably without heating means therein.

Preferably the tape is precreased before it enters the apparatus in order to promote its uniform straight folding upon and astride the ends of the bags. This is advantageous in producing rm bag ends, that is with the tape pressed tightly against the ends of the plies of the bag and to insure an equal overlap of the two sides of the tape upon the two bag surfaces respectively. Such precreasing may be accomplished in various ways. For ex` ample, as shown in Figs. 4-6, a pair of rollers may be used for that purpose, between which the tape 17 is drawn, one of the rollers 34 having a groove 35 and the other having a disc 36 for pressing a crease along the mid portion of the tape into the groove 35.

The heating means which preheats the bag ends and tape and which also acts as the means for folding the advancing tape into position, may comprise three sheet metal resistance heating elements 37, 38 and 39 and a so-called tape binder 40. All three of these sheet metal heating elements 37, 38 and 39 have their ends electrically connected respectively to a source of current. These heating elements may be formed of any suitable resistance material, such as some form of stainless steel or well-known sheet resistance material sold under the trademark Nichrome, for example. The source of current used for these elements is preferably of low voltage, for example l or 2 volts, and the current value may be adjusted by trial to insure heating of the elements to the above-mentioned temperature range.

As the tape 17 passes over the roller 34, it comes into contact with the binder strip 40 at a point where such binder is flat in a vertical plane, as shown in Fig. 9. At this point the heating element 37 is also at and engages the plastic coated surface of the tape 17, the tape sliding rapidly along between members 37 and 40 toward the right. At points further toward the right, the members 37 and 40 assume V-shaped cross-sections as shown in the sectional view of Fig. 7. At this point the tape 17 has been folded to a corresponding V-shape. Further on toward the right the members 37 and 40 assume a U-shaped cross-section as shown in the sectional view of Fig. 8 and with the tape 17 therebetween and now in a position astride the bag ends although spaced therefrom by the heating element 37. Finally as the tape passes on out of contact with the heating element 37, its inner plastic surface will be adequately heated and will come into contact in proper position astride the heated bag ends.

Referring back now to the left hand ends of Figs. 4-6, the ends there shown of the heating elements 38 and 39 are flared apart to facilitate entry of the bag ends therebetween, the element 38 then serving to heat the upper surface of the bag end, and the element 39 the `-lower surface thereof. These two heating elements preferably, as shown, are flat strips which respectively slidably engage and heat the bag end surfaces as the bag ends move past the various positions indicated by the sectional views of Figs. 6-8.

As best shown in Fig. 4, heating element 37 at its left hand end maybe lformed with supporting and retaining lugs as at 42, 43, one or both of which have electrical terminal connections as at 44, 44. Heating elements 38 and 39 respectively may be supported and connected to the electrical connections at 44, 44 as by angularly shaped portions 45 and 46. At their right hand ends, all of the heating elements maybe connected to electrical terminals 47, 47 vand also supported asby angularly shaped bracket portions at 48, 49.

Preferably the binder member 40, together with the precreasing rollers, are mounted on frame structure in a manner so that they may be swung lback with the tape 17 thereon, so as quickly to move the tape away from the heating element 37 whenever the machine is stopped. For this purpose frame structure 50 on which the binder parts are mounted may Vbe vconnected in Vturn to any suitable stationary support by 'a -link as at -51 and a bell crank as at 52 (Fig. 5), the bell crank being operable automatically as by an air cylinder or solenoid at 53, suitably connected to be actuated upon stoppage of the apparatus, whereupon the binder member 40 and the precreasing rollers and the supporting frame therefor, will be moved respectively to the dotted line positions indicated in Fig. 5. In this position the tape will be safe against overheating by the heating element 37. It is also convenient to have the binder element 40 shiftable in this way in order to facilitate cleaning out the passage for the tape or straightening the tape in case it should become jammed, torn or out of place in passing through the apparatus.

With the above-described arrangement, it will be apparent that both the inner and outer surfaces of the tape, including the plastic coating thereon, may be very quickly heated to the necessary temperature to secure a good bonding action with the bag ends, and since at the same time both the upper and lower surfaces of the paper of the bag ends are also similarly heated to or within the same relatively high temperature range, there will be an effective permanent bonding between the plastic and the paper when the assembly is subjected to pressure between the rollers 14, 15, or belts a. That is, the plastic, while still in sticky condition, will be forced into and about the hot fibres of the paper before the plastic cools and sets.

Although particular embodiments of the invention are herein disclosed for purposes of explanation, various modifications thereof, after study of this specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

l. Method for sealing flattened sewn end closures of paper bags which comprises: continuously advancing a series of bags longitudinally of the end edges thereof while subjecting the surface areas of such ends directly to heat by causing same to be slidably engaged between electrical heating elements; continuously and simultaneously advancing tape along the bag ends, which tape has a polyethylene coating on its surface facing the bag ends; folding over said tape during its advance into position to be astride the bag ends and simultaneously directly heating said tape by causing the coated surface thereof slidably to engage an electrical heating element; and then applying pressure to bring the folded-over sides of the heated tape respectively into rm engagement with the opposite wall surfaces of the heated bag ends, said heating elements being maintained at temperatures of the order of several hundred degrees Fahrenheit, but the 'tape' and 'bags being advanced at a speed of at least several hundred inches per minute and sufiicient to avoid injury thereof by reason of said temperatures.

2. VMethod for sealing sewn end closures of paper bags which comprises: continuously advancing a series -of Ithe bags with their sewn .end closures in flattened condition and moving longitudinally of the end edges thereof while subjecting the exposed end surface areas thereof to heat; continuously and simultaneously advancing tape along the thus heated bag ends, -Which tape has a thermoplastic coating on a surface facing the bag ends; folding over said tape during its advance into position to be astride the bag ends and also, prior to its application to the bag ends, heating said tape; and then after such application applying heat and pressure to bring the folded-over sides of the heated tape respectively into firm bonding engagement with the opposite wall surfaces of the heated bag ends.

3. Method for sealing end closures of sewn end paper bags which comprises: continuously advancing a series of the bags with `their end closures in flattened condition and moving longitudinally of the end edges thereof while exposing the sewn end surface areas thereof directly to heat; 'continuously and simultaneously advancing tape along the bag ends, which tape has a thermoplastic coating on a surface facing the bag ends; folding over said tape during its advance into position to be astride the bag ends and also exposing said coating directly to heat before same contacts the bag ends; thereafter applying pressure to bring the folded-over sides of the heated tape respectively into rm engagement with the opposite wall surfaces of the heated bag end; and also subjecting the folded-over tape simultaneously to further heating while being thus subjected to pressure.

4. Method for sealing sewn end closures of paper bags which comprises: continuously advancing a series of the bags with their end closures in flat condition and moving longitudinally of the end edges while exposing the surface areas thereof directly to heating means; continuously and simultaneously advancing tape along the bag ends, which tape has a polyethylene coating on a. surface facing the bag ends; folding over said tape during its advance into position to be astride the bag ends and also exposing said coating directly to heating means; and thereafter applying pressure to bring the folded-over sides of the heated tape respectively into firm bonding engagement with the opposite wall surfaces of the heated bag end, said heating means being maintained at temperatures of the order of several hundred degrees Fahrenheit, but the tape and bags being advanced at a speed of at least several hundred inches per minute and sufficient to avoid injury thereof by reason of said temperatures.

5. Method for sealing end closures of paper bags which comprises: continuously advancing a series of the bags with their endsv which are to be closed in attened condition and moving longitudinally of the end edges while exposing the sewn end surface areas thereof directly to heating means; continuously and simultaneously advancing tape along the bag ends, which tape has a polyethylene coating on a surface facing the bag ends; folding over said tape during its advance into position to be astride the bag ends and also exposing said coating directly to heating means; thereafter applying pressure to bring the folded-over sides of the heated tape respectively into rm bonding engagement with the opposite wall surfaces of the heated bag ends; and also subjecting the folded-over tape simultaneously to further heating while being thus subjected to pressure.

6. Method for sealing flattened sewn end closures of paper bags which comprises: continuously advancing a series of the bag ends longitudinally of the end edges thereof while subjecting the surface areas thereof directly to heat by causing same to be slidably engaged between electrical heating elements; continuously and simu1taneously advancing tape along said bag ends, which tape comprises a thermoplastic material; folding over said tape during its advance into position to be astride the bag ends and simultaneously directly heating said tape by causing same slidably to engage an electrical heating element; and then applying pressure to bring the foldedover sides of the heated tape respectively into rm engagement with the opposite Wall surfaces of the heated bag end, said heating elements being maintained at temperatures of the order of several hundred degrees Fahrenheit, but the tape and bags being advanced at a speed of at least several hundred inches per minute and sufcient to avoid injury thereof by reason of said temperatures.

7. Apparatus for sealing flattened end closures of bags comprising in combination: conveyor means for continuously conveying a series of the bags longitudinally of the end edges thereof; means for simultaneously directly exposing the surfaces of the bag end to heat; means for continuously supplying a strip of closure tape having a thermoplastic surface; guide means for slidably engaging such tape while folding same into a position to be astride the advancing bag edges, said guide means including an electrical resistance heating element for heating the thermoplastic before contact with the bag ends; and pressure rollers for then pressing the folded-over sides of the previously heated tape respectively into engagement with the opposite wall surfaces of the preheated bag ends.

8. In apparatus for applying and sealing folded-over thermoplastic-bearing tape in position astride attened bag ends, means for continuously conveying a series of the bags longitudinally of their end edges and at a speed of the order of several hundred inches per minute, tape folding means formed with elements which comprises electric resistance heaters for slidably engaging and preheating the tape before contact With the bag end surfaces, heating elements for preheating the bag end surfaces just before contact of the preheated tape therewith, and means for applying current to said heating elements suflicient to maintain same at temperatures of the order of several hundred degrees Fahrenheit.

References Cited in the file of this patent UNITED STATES PATENTS 1,628,800 ODonnell May 17, 1927 2,244,282 Bergstein June 3, 1941 2,660,100 Doyle Nov. 24, 1953 2,690,633 Denton Oct. 5, 1954

Images