US2524032A - Sealing method for cartons - Google Patents

Description

L. BACK SEALIN'G METHOD FOR cARToNs Oct. 3, 1950 2 sheets-sheet 2 Filed June 7, 1945 LEU/YARD BHCK INVEN TOR.

Patented Oct. 3, 1950 2,524,032 Y SEALING METHOD VFon cAR'roNs Leonard Back, Middletown, Ohio, assignor to The Interstate Folding Box Company Application June 7, 1945, Serial No. 598,063 claims. (o1. 93-6) My invention relates to the problem of producing tight closures in seal end cartons. Seal end cartons are a well recognized type of folding paperboard box having a tubular body formed of body wallsin articulation With each other and closure means consisting of ilaps articulated to the ends of the body walls, Which ilaps are bent over inwardly, interfolded, and adhesively secured to form the closure, In the term tight closures I mean to include'closures ranging from those which are siftproof as respects nely powdered contents to those which may be liquid or gas tight and constitute hermetic seals.

The seal end carton has long presented a distinct problem in the carton industry. The usual commercial practice is to up-end the erected tubular cartons over a sealing mandrel, apply adhesive to the sealing flaps, interfold them accurately and then press them between the internal mandrel and an external pressure element. In this Way a reasonably siftproof result may be obtained with accurately cut cartons, although for many uses closures so formed are not as tight as they should be. But this method of sealing is capable of use only on the bottom closure of a seal end carton or on that carton closure which is made first, for the reason that in making the second or last closure after contents have been introduced into the cartons, an internal mandrel can no longer be used. The practice has been to fold a pair of ilaps inwardly While another pair is outwardly folded, to apply adhesiveat least to the outfolded aps, and then to fold these flaps inwardly successively. There is nothing, however, to supportthe ilaps from beneath .when they are in folded position. Thus, no effective pressure can be exerted on them from without. The ilaps, particularly the innermostflaps, tend to curl or become depressed and 4hence to spring away from overlying flaps so that no good adhesive bond can be obtained. As a consequence, the last formed seal end closure of a seal end carton is likely to be not only imperfect in physical construction but also perforate,` particularly at the corners ofthe closure, so that such cartons are frequently found not to be satisfactory carriers even for coarse grained granular materials.

Since a carton is no better than its poorest closure, those intended for use with powders now employ, wherever cost will permit, either an inner liner or an outer wrap or both.

What is needed, as a first consideration is a procedure, applicable to both ends of a seal endv carton, which will result in enforced physical Conformation of all aps in the closure so that an out using a conventional mandrel on either end.`

It is an object of my invention to provide means and a method which, while they can be carried' on without mechanism other than a simple tool hereinafter described, are nevertheless well adapted for .use in connection with mechanical carton closing and sealing equipment.

It is also an object of my invention to provide means and a method applicable to the sealing of either or both ends of a seal end carton irrespective of the position of the carton, so that the operation of inverting the carton, hitherto generally used in carton sealing', may be eliminated with attendant economies in both time and equipment.

' These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications I accomplish by that mode of operation and `by that means of which I shall now describe certain exemplary embodiments.

Reference is made to the accompanying drawings wherein:

Figure 1r is a partialplan View of an exemplary seal end carton.

-' and showing a means which I may use.

Figure '7 is a partial isometric view of the closed carton.

Figures 8, 9, 10 and 1l are isometric views showing successive stages in ak modied mode of sealing a similar carton.

.Referring to Figure 1, I have shown an ordi- It is characteristic of my invention, however,

that the sealing method and means hereinafter described and illustrated as applyinglto the seal.'

end closure shown in Figure 1 is similarly and even simultaneously applicable to a sealendclosure on the other end of the carton blank.

From the form of the carton blank illustrated in Figure l, it will be apparent to one skilled in.

the art how the blank may be folded or tubed inl the ordinary way by being bent upon a pair of the score lines articulatingl the body walls to each other, with the adhesiveattaclfinient` of the glue flap 5 to the outer edge of the body wall l. The size of the cartons, the number andY shape of"the.enclosing body walls and seal end flaps, and the specific cross sectional shape of the erected tubular structure do not constitute limitations upon my inventionl and may be varied as desired". in accordance withl known practices. For purposes of my invention I prefer accurately made and accurately cut'cartons having seal end flaps which are also accurately cut and of as full asize asis consistent with good carton practice and board economy. Two at least of the naps constitutingan opposedpair arepreferably of suificient size to extendY across the entire'end of the erected carton.

In formingmy cartons I prefer to make the horizontal score lo" by means of a continuous rule, the vertical scores and vertical outlines beingvmade by rules .butted against the first mentioned rule. Thisinsures that the cut lines demarkingthe seal end flaps from each other donot extend into the area of the score by which, these flaps are articulated to the respectivebodywalls. Otherwise, my, seal end cartons may be the Same as any commercial seal end structure, and' maybe printed .or not, as desired. In order tol make the tightest possible closures, even iorsiftproofing, I prefer to impose. upon thev board from which the cartons are. made areas of thermoplastic adhesive soplacedthatin the finished carton the seal end flaps, the score lines by which theyy are articulated to the body walls, and adjacent'areas of the body walls themselves are continuously coated with the adhesive substanceY as indicated at Il in'Fig. 1.

.W here the cartons are to hold liquids, the board should `be Vtreated soa-s to be impervious' to the liquids and so as to have its capillarity destroyed, as in the copending application of Samuel Bergstein entitled Liquid Tight Seal End Cartons, Serial No. 600,754, filed June 2l,` 1945. One .eX- emp1arywayof doingthis is to impose uponone side of the board a proong substance which'V is drivenintotheboard to theextent of saturating itthrough or nearly throughto. theother side,

after which on the other side a continuous coating. of v thermoplastic proofing and. adhesive` substance is applied. However, where liquid tightness .is nota necessity, I may -make my cartons of untreated-board. Y

My procedure is based upon a concept oiinter folding` and. adhesivelysecuring ataleast` a pair 0f opposed caps in a seal end carton while these flaps are supported from within by a thin but sufficiently stiiT metal plate, having a mounting portion extending outside the carton at the same end. The plate operates to keep all the naps (so interfolded) in accurate over-all face-to-face contact until the adhesive bond has sufficiently formed. It prevents any of the ilaps from springing or curling away from others and serves as an'inner pressure element against which interoldedflaps may be compressed by means of an outer pressure element. It is manipulated and may be inserted and Withdrawn from the end of the carton uponwhich the interfolding and sealing operation is being performed. It does not employ anymeans such as a mandrel inserted into the carton from the other end. Consequently, it'may be used on either end of the carton, and in particular may be employed for forming the last closure on cartons which have alread;7 been filled.

The rstessential is the bringing about of complete conformity and good adhesion between the initially folded flaps; but when at least two opposite ilaps have been so folded and secured, they form, as hereinafter more fully explained, a platform or bridge extending across the carton onto which another ldap or flaps may be folded and adhesively secured, the platform at this time furnishing suiiicient support for the last folded flap or flaps so that external pressure means can bring the last folded iiaps into complete conformity and adhesive union with the first folded flaps.

Referring to Figure 2, when the carton has been erected, I place across the open end of it a thin but relatively stiff metal or other plate l2, the seal end flaps having been folded sulficiently out of the way. The plate may be moved and positioned entirely by hand, if desired, but it is also` readily susceptible of mechanical operation. I have shown it mounted upon a rod or shaft IS-which may be regarded either as a handle for manual operation or as a means for mounting the plate l2'upon mechanical agencies to move it.

The plate l2, being widerthan the carton in oneI dimension, will overlie a seal end fiap such as the flap 9; so that the iiap 9 must be bent outwardly and downwardly sufficient to permit the positioning of the plate. The manner in which the plate is moved into position is not a limitation on the invention. It may be broughty in from the side by a sliding motion transverse to the outfoldedflap 9. It may simply be lowered into position. Itmay be brought into position by a' downward and inward movement. It may be located at a fixed station in a carton sealing` The rst vsealing operation aiter'the positioning of the plate may be the inward folding vof flaps and 8, as shown in Figure 3. The dimensions of. the plate are such that it extends across Vthe end of the carton and .therebeyond in one direction at least as indicated. When .the iiaps 6A and.` 8 have been folded as shown, adhesive may be applied to them and/or to the outwardly folded flap 'I by means in*v current use-on. carton sealing machines. 1f, as I prefer, the carton has `already been provided with an area I I of thermoplastic adhesive, this adhesive is reactivated, as may be done by applying radiant heat to flap 'I prior to its folding.

The flap I may then be folded over as shown in'Figure 4, coveringr flaps 6 and 8.- Pressure to cause the flaps to conform with each other may then be exerted by an external pressure means I4 (Figure 5). The plate I2 insures an accurate folding of the flaps 6, 8 and 'I holds the flaps together when interfolded by clamping them between itself and the external member I4. Under the action of the external pressure means I4, the inner end of the plate can depress slightly, as shown in Figure 5, permitting tight closure to be made at the corners A and B of the carton; but

the clamping pressure will be'sufliciently positive to enforce surface conformity of the flaps throughout their area.

Where the carton has been precoated with the adhesive I I the corners are sealed by the flow of the softened adhesive. This is of the greatest importance in producing closures which are completely and hermetically tight. It is to be pointed out, however, that the accurate folding and inward support of the carton flaps insures their complete surface conformity and accurate adhesive union, and even with adhesive applied in the ordinary way at the time of closure producesY a result superior to results hitherto obtained, where internal mandrels could not be used, as for example, onV the top closure of a carto Where adhesive is applied at the ltime of closure, I may use the means and method of Bergstein Patent 1,976,980, dated October 16, 1934, resulting in the depositing of extra quantities of adhesive adjacent the corners of the flaps.

I have encountered no problem of adhesion of carton parts to the supporting plate. When adhesive is applied to flap 'l during the process of effecting closure, it will be understood that the flaps 6 and 8, if they meet, overlie the plate completely and protect it from contact with the adhesive. In cartons of certain shapes, as for example a carton which is quite wide in relation to its depth, the inner, first folded flaps will not meet unless extra board is used to make them longer. gether, and a heavy application of hot melt or other adhesive is made to flap I, I may relieve my supporting plate in the space between the ends of the inner flaps, or even cut it away altogetherin this area, y

In the case of cartons which have been precoated with thermoplastic adhesive, as in my preferred practice, the under sides of flaps 6 and B may be coated on their under sides with adhesive. Also the score lines may be covered as described. The application of heat to flap 1, by radiant or other means, softens the adhesive on this flap and along its score line and at the corners; but is quite easily so applied as not to soften the adhesive on the other flaps. When flap 'I is folded over, the adhesive on it will be in a condition to adhere to the flaps beneath, and upon cooling to form a firm bond with them; but it does not follow that suicient heat is transmitted through these flaps to effect great softening of the adhesive on their under sides. On the contrary, the

.adhesive upon flaps 6 and 8 is not much affected,

especially since the supporting plate and the pressure element are preferably not in a heated v condition..

When the inner flaps do not come to- The amount of pressure on the flaps between ling means brought close to its upper surface, or

if the flap 9 has not'previously been treated with adhesive, it will now be Vcoated as by a suitable roll coating device.

When the flap 9 is folded over onto the rigid platform formed of flaps 6, 'l and 8, it can be brought into accurate registry with them and made to have complete surface conformation with them by external pressure means through the supporting effect of the platform.

It will be seen that the result is a seal or closure of seal end type in which all flaps'have complete and accurate surface conformation. None of the flaps spring, bend or twist away from others during the sealing and hence cannot fail to be adhered throughout to the other flaps. A

At the corners C and D'of the cartonfFigure 4), the act of infolding the flap 9 and drawing it over the platform compresses the board and forms a tight closure at these corners also. The pre-applied thermoplastic adhesive at these points, in my preferred practice, again flows to ll all interstices and providesV an hermetic clo- Sure.

I prefer also to employ an expedient taught in the copending application of Samuel Bergstein, Serial No. 586,970, filed April 6, 1945now abandoned, and effect a slight inward bowing of the body wall 4 of the carton adjacent the line of articulation of flap 9. This may be accomplished by a finger or the like on means for holding the carton as illustrated in Figure 6 at 15. The result of bowing the wall 4 inwardly is to provide a ledge at the score line of flap 9 upon which the edge C-D of the platform will rest. Then when the flap 9 is folded inwardly,` the platform is not only supported at its otherwise free edge but the adhesive treated surface of flap 9 is drawn tightly over the said free edge of the platform making a tight adhesive closure all along this edge and inclusive of the corner portions C and D.

By the `means and mode of Yoperation hereinabove described, I have succeeded in producing tight and siftproof closures on seal end cartons without the use of internal mandrels. Where the board of the cartons is precoated with liquid proof thermoplastic adhesiveV as described,v the closure itself becomes liquid tight. Where the board of the cartons has also been treated so as not to be softenable by liquids, a carton so sealed is capable of holding liquids for long periods of time and is in effect hermetically sealed.

In Figures 8 to 11 inclusive, I have indicated a modified procedure. A thin metal strip or plate I6 is caused to extend over the open end of the carton. It should not be wider than the carton.

If the carton has not previously been treated with thermoplastic adhesive, a suitable adhesive (thermoplastic or solvent) may be applied to either of flaps 'I and 9. In Figure 9 I have Shown the flap 'I folded over onto the plate I6, and in Figure 10 the flap 9 infolded to overlie the flap 1.

lIfheftwo liaps are thus adheredtogether insaccu- 'rate' surface conformation -while supported by the V.plate 16. fAn-.eXternal cooperating pressure element may,of course, Vbe used. After the adhesive has set, the plate i6 is withdrawn endwise.

VFlaps 'l and 9 in adhesive union form a platform extending across the carton endV from side to side, and supported-by the carton side walls 4 and .2.A With an application of adhesivel to flaps f6 and '1, if they have not -previcusly been coated, these fiapsare folded over onto the platform. j ln doing this, l prefer to indent the end walls Al Vand -.3 adjacent Ythe lines of articulation of'theirfaps as by fingers, oneof which is shown at llin Figure 11. The result is that the ends of afname the-platform are not only supported, but the ilaps 6 and -'are drawn tightly over the edges of the platform, forminga Very-tight closure at the corners. Thestiffness of the platform-supports flaps Gand 1 and enables an external pressure element to produce accuratesurface conformation. ben tween these flaps and the platform until the adhesive has set.

Itwill .be clear from the teachings herein that my'means and modes ofsealingare applicable to either-.or both ends ofa seal end carton irrespective .of the position of the carton. Hence both ends ofthe carton .may be closed and sealed while the carton is Ain a single orientation, and no up-ending of the carton .is necessary between .closure operations. I may, for. example, position .a carton vertically, close it on the bottom and .then close and seal it on the top,.all without turning it endfor end, .and withvorwithout moving it from station to station ina machine.

Modifications may be made in my invention without departing from thezspirit of it. Having thus described my invention in certain exemplary embodiments, 4what I claim-as new and desire to secure byLetters Patent is:

1. The .method of producing uniform adhesion between and surface conformation of sealing flaps articulated to the end of a carton body, which method includes supporting a pair of initially infolded flaps over a relatively thin plate extending across the carton body Vat said end and extending beyond the carton body at one side thereof over an outfolded flap, adhering at least one remaining flap to the previously infolded flaps in superposed position thereon while all of said flaps'are so supported, thereupon withdrawing said plate ovel1 said outfolded flap and from beneath said infolded flaps and `adhering the previously outfolded nap in superposed position over said previously adhered flaps.

2. A method ofsealing flaps atthe end of. a cartonbody,.which includes as separate stages of folding and adhesively securing, the folding in of apair of opposite flaps and the adhering of another flap theretov while said flaps are supported by a plate extending across the carton end and therebeyond at one side, and located on the inner side'of the said flaps, and when an adhesive bond has been secured, withdrawing the said plate transversely of the carton end and folding inwardly and adhesivelysecuring another flap to said previously folded and adhesively secured flaps.

3. A method of sealing naps articulated to an end of a carton body, which includes positioning across the open end of a carton body a platelike Ymember extending transversely of the carton body therebeyond at one side edge, folding inwardly over said plate a -pair of opposite sealing flaps, folding inwardly and securing to the first mentioned nap another flap, thereupon withdrawing said supporting plate transversely yof the `carton end to provide across the end of theA carton a supporting structure formed `of .infolded Vflaps secured together complete surface conformity, and thereafter folding in and adhesively securing tosaidv-previously folded and secured aps anfother carton flap to complete the closure.

4. `A process of closing seal end cartons .which comprises interfolding and adhesively securing some lbut `not all -of the sealend Vflaps-ofsuch cartons, -twoat least of said flaps beingattached to opposite carton walls, pressing said fla-ps so as to secure surface conformity against a platelike member positioned Atransversely inwardly from the same end of said'carton so as to lielbeneath said flaps, whereby to form of said'adhesively secured flaps a platform extending across the end of said carton, then transversely.withdrawing said plate-like member, and interfolding and adhesivelysecuring the remainderof ysaid flaps, said remainder being supported -by said vpreformed platform and pressed thereagainst sogas tor-be brought into surface conformity therewith.l

5.*A process of yclosing rectangular seal end cartons which comprises interfolding andfad-hesively securing :a pair of opposite .seal end -iiaps plus athird seal end Hap of such cartons, lpressing said flaps so vas to secure surface conformity against aplate-like memberpositioned from the same endof thesaid cartonsoas to lie inwardly .of said flaps with a portionprojecting Abeyond the carton in the direction of the remaining-'unfolded flap, whereby toform .of said adhesively `secured flaps a .platform extending across the-end of said car-ton, then :withdrawing-said .plate-like member from the carton in the ydirection oi' said unfolded flap, andfoldingover and adhesively securing said last mentioned flap, said ap being supported by said preformed platformand pressed .thereagainst so as to be .brought tinto sur-face Vconformity therewith.

6. The process claimed in claim 5 .including the step of .applying adhesive to certain at least of said. flaps after the .positioning of .said .plate-like Y -gether in this fashion until an'adhesive bond has beensecured whereby to formv of said adhesively secured flaps.a'platform-extending across theend of said carton, then withdrawing said'platerlilre member substantially the plane of the carton end, applying adhesive to the remainder of said flaps and folding them while supporting them by and pressing them against said preformed platform so. as to holdY them in surface `conformity therewith.

8. The'process claimed in claim 5 in vwhich the cartons vhave preformed coatings of thermoplastic adhesive on the flaps thereof and in which just prior to interfolding the adhesive is'reactivated by heat on a sufficient number of `lapsto produce the adhesive unions set forth.

` 9. A process of closing rectangular seal end cartons which comprises positioning a thin. platelike member across an open end of said carton so that it extends beyond said open end at two opposite sides and at least partially overlies two opposite seal end flaps which are in outfolded condition, folding inwardly and adhesively securing together the remaining pair of opposite flaps while pressing them against said plate-like member so as to secure surface conformity, whereby to form of said adhesively secured flaps a platform extending across the end of said carton, then withdrawing said plate-like member in an endwise direction7 and then folding over onto said platform and adhesively securing thereto said rst mentioned pair of opposite flaps, pressing said flaps against said platform as a support so as to secure surface conformity between said platform and said flaps.

10. A process of closing seal end cartons without inverting them, which comprises effecting closure on both ends by steps involving folding some but not all of the seal end flaps of the cartons at each end over plate-like members positioned from the same ends of the carton inwardly of the folded flaps, and adhesively securing said flaps so as to form platforms extending across the ends of said carton, then withdrawing said plate-like members transversely and adhesively securing the remainder of said flaps to said preformed platforms and pressing them thereagainst.

LEONARD BACK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,365,415 Lawrence Jan. 11, 1921 1,577,850 Peters et al Mar. 23, 1926 1,634,073 Labombarde June 28,1927 1,965,897 Jurgens et al July 10,1934 2,074,357 Bergstein Mar. 23, 1937 2,206,203 Richard July 2, 1940 2,217,757 Lindley Oct. l5, 1940 2,266,054 Lowey et al Dec. 16, 1941 2,328,758 Vergobbi Sept. 7, 1943 2,330,466 Bergstein Sept. 28, 1943 FOREIGN PATENTS Number Country Date 281,794 Great Britain Dec. 15, 1927

Images