US2758432A - Method of sealing closures for containers - Google Patents

Description

Aug. 14, 1956 G. A. MOORE METHOD OF SEALING CLOSURES FOR CONTAINERS Filed NOV. 25, 1953 l N V E N TO R 620/7615 fiRU/vc; TON/70 ORE United States Patent METHOD OF SEALING CLO'SURE'S FOR CONTAINERS George Arlington Moore, New York, N. Y.

Application November 25, 1953, Serial No. 394,376

8 Claims. (Cl. 53-14) This invention relates to paper containers, more particularly to a method for sealing the closure of containers. The method constitutes a process whereby molten resinous adhesive material having thermoplastic properties may be efficiently and economically embodied in the structure of container closures to insure a strongly united and tightly sealed container.

Conventional folding carton type paper containers usually have the co-operation of inner-liner sheet materials or bags inserted within the container, deemed necessary to hold the product for distribution to prevent leakage and safeguard against other deleterious effects to particular products. In addition to incorporating such inner liners, outer wrapping materials are employed to the containers, such as cellophane or foil to add further protection. The sequence of operations made necessary to employ these methods results in added costs and complicates the construction of the complete container.

It is an object of this invention to eliminate the need of extraneous sheet materials used in conjunction with conventional paper containers.

Another object of the invention is to provide means whereby a tongue-like component part of the closure of containers is bathed with a thermoplastic material to provide a sealing gasket when the closure is formed.

A further object of the invention is to provide means whereby molten resinous adhesives may be used and applied to closures of containers in an efficient manner at low cost of adhesive applying equipment.

Further, said invention has for its object to provide an overall coating to a part of the closure of a sealing medium of any desired weight of dry solids.

And still further, said invention has for its object to provide closures for containers having gasket-tight seams made by the application thereto of heat and pressure.

To the attainment of the aforesaid objects and ends, my invention consists in novel features, and in the steps constituting the method, hereinafter more fully described and then pointed out in the claims.

In the accompanying drawings:

Fig. 1 is a view in perspective of the container with a component part thereof positioned to receive an application of resinous adhesive,

Fig. 1a is a fragmentary view in perspective of a component part of the closure forming end segments being submerged in a bath of resinous adhesive,

Fig. 2 is a fragmentary view in perspective of the closure partially folded,

Fig. 3 is a fragmentary View in perspective of the completed closure, and

Fig. 4 is a'fragmentary view in cross-section of the closure taken on line 44 in Fig. 3.

The invention is particularly applicable for the closing and sealing of folding-carton types of containers. The walls of the containers may be treated with protective coating materials selected to be compatible with the closure sealing adhesive. The efiiciency of the con- Patented Aug. 14, 1956 tainer may be increased by utilizing the improved structural features of the closure illustrated in this invention. The folding features of certain parts of the closure are somewhat similar in the disclosure of my co-pending application Serial No. 302,961 filed August 6, 1952, now U. S. Patent No. 2,737,336 issued March 6, 1956.

The conventional containers hereinbefore referred to usually employ aqueous adhesives such as paste or glue, being Water laden adhesives they require a relatively long time in which to reach sufiicient tack for the adhesive to grip. The water must be evaporated thus having reaction tendencies to cause warping of the paper board material. Paste applicator fountains require constant attention and must be cleaned periodically.

The method of this invention dispenses with such aqueous paste or glue by employing resinous types of adhesives commonly named hot-melts. Such adhesives are used conventionally for fabricating containers, but the adhesive is applied on expensive machinery equipment known as hot-melt applicators. The application is controlled by etched cylinder rolls revolving in a heated bath of the resinous material, the cells of the etch picking up the adhesive and transferring it to the container blank prior to the container being formed. The quantity of adhesive to be transferred is limited to the size and depth of the etched cells in the face of the applicator cylinder. The problem inherent in this method is to apply enough body of adhesive with limited cell capacity, furthermore the application of adhesive is limited to fiat surfaces only.

The method of my invention eliminates the requirements of costly applicator machinery with which to apply hot resinous adhesive for use of the container closure. Further, the quantity of adhesive to be applied is not limited.

Referring to Fig. 1 of the drawings, the container 5 is of the folding carton type, the body blank of the container having been cut, creased, folded and secured with a longitudinal body seam. The flat folded blank has been opened to shape the body and the panels 6 have been folded downwardly in a substantially vertical position away from a side wall of the body. The container in the position shown may be held and controlled by employing any suitable type of conveyor system to move the prefolded panels 6 through the coating operation. A tank 7 having embodied therewith suitable heating means (not shown) serves as a reservoir to hold a molten bath on of any desired resinous adhesive (hot-melt) having suitable temperature elevated as desired by the said heating means. The panel 6 is lowered into the tank, submerging the panel in the bath up to the folding hinge 8. The container is then elevated to withdraw the panel 6 from the bath. Both flat surfaces and the edges 9, 1t) and 11 and hinge junction 8 having been coated efliciently with suitable resinous adhesive to constitute a closure sealing gasket type sealing element adapted when re-folded to be the signal means of sealing seal the closure of the container.

The simple tank 7 illustrated in Fig. 1 is intended only to clarify at a glance the principle of this invention. The illustration in Fig. 1a is another example more in keeping with the mechanical principle that may be employed to carry out the method of coating the panel. The tank 12 is an elongated trough filled with a molten bath of adhesive material 6b. The tank side walls 13 terminate upwardly and inwardly to provide a slot 14 that may be adjusted in width. The container 5 is lowered while being moved in a longitudinal direction so that the downwardly extending panel 6 enters the slot 14 which at this point may be open wider to facilitate free entree. The panel is submerged in the bath 6b and moved through the bath in a longitudinal direction until it reaches a position where the slot '14-is narrowand of'the desired width. The container is then raised upwardly to withdraw the bathed panel 6 from the bath, the lips 15 serving to level off excess adhesive and froth to provide a smooth film over both flatsurfaces of the panel. The width of the slot determines the quantity of adhesive to be deposited to both sides of the'panel.

The viscosity of the resinous adhesive may be controlled as desired by regulation of heat. The tank-trough 12 may be equipped 'with'electrical heating elements regulated with a thermostat, the temperature of the bath being maintained atsubstantially-a uniform heat.

Thus, the application of hot-melt adhesives to a component part of a closure structure can be carried out by the method of this invention free of complicated and costly machinery. Any desired weight of dry solids of adhesive may be obtained without the limitations inherent in conventional methods 'usually employed. When the panel 6 is withdrawn from the liquid bath of hot adhesive, the coated film 16 (Fig. 29 solidifies quickly to a dry and tack-free condition. There are no solvents present to get rid of, the dry solid content of the adhesive being substantially one hundred per cent. 'There are available many varieties'of such adhesives compounded of resinous and wax materials that are non-toxic and odor-free having varying softening points of a wide range of temperatures, for example l80 degrees to 400 degrees F.

The forming of the closure is illustrated in Fig. 2. The wings 17 are folded inwardly and outwardly to provide resilient spring resistant sealing ledges on two opposing sides at the top of the container walls. The coated panel 6 is then folded inwardly and downwardly to engage the upper surfaces of the spring-like folded wings 17. The coated edges 10 and 11 of the panel 6 engage a marginal area of the interior surface of the opposing side wall adjacent to the junction of the foldable panel 18 in face to edge abutment relationship. The adhesive 16 upon the edges 10 and 11 of the panel 6 provides a sealing gasket medium at these edge abutting surfaces. The panel 18 is then folded inwardly and downwardly to overlap the folded panel. 6 in face to face engagement. The panel 18 is provided with a scored hinging line 19 extending between the hinges 20 of the folded wings 17. Cut score lines 21 extend from each terminal end of the score 19 to the opposite edges of the panel 18. When the panel 18 is folded downwardly in parallel relationship with the foldedipanel 6, the displacement of material in the score 19 caused by bending of the panel 18 moves material inwardly into and against the recessed edge 11 of the panel 6. The edges 10 remain in flat abutment upon the marginal surface of the opposing side wall inasmuch as the cut scores 21 permit the panel 18 to fold over a face to edge abutment 22 of the folded wings 17 when flattened downwardly, eliminating interferences of displaced material at these junctions.

The completed structure 'of the closure is illustrated in Fig. 3. The overall adhesive coated panel 6 constitutes a container self-embodied closure sealing element which is disposed inwardly and intermediate of the folded wings 17 and folded overlapping panel 18, thus forming an interiorally disposed sealing gasket which isolates the adhesive thereupon within the closure.

Heat and pressure applied to the exterior surface of the folded panel 18 activates the adhesive intermediately disposed, rendering it viscous momentarily to plug tightly all engaging areas disposed within the closure. When cooled the hardened adhesive seals the closure securely. The adhesive provided on edges 10, 11 and hinge 8 supplies the sealing medium to these vulnerable areas to plug and secure the engaging surface areas of material.

Another method with which to seal the closure of this invention may be employed by pro-heating the coated panel 6 with radiant heating means just prior to folding it in conjunction with'otherrnembers to form the closure.

In this manner of activating the adhesive it is not necessary to conduct heat through the folded overlapping panel '18 of the closure. Pressure without heat applied to the said panel will seal the closure eificiently. The upwardly directed pressure resistance of the folded wings 17 resists the downwardly directed pressure upon the panel 18 to insure a tight seal.

Elongated moving belts may be employed to supply pressure and/or heat upon the closure to provide a simple means of effecting a seal of the closure. If it is desired to supply heat through the .panel 18 with which to activate the adhesive, the closed container may be clamped with a pre-heated and moving steel belt to seal the bottom end closure and after filling thecontainer with its intended product, duplicate the same operation for sealing the top end closure of the'containcr.

Existing carton set-up machinery can be modified mechanically to carry out the sealing method of the pres ent invention. The panels 6 at each end of the container 5 can be simultaneously coated with adhesive by the fabricator of the containers prior to shipping them to packers plants. The adhesive coating is dry and non tacky, hence the containers may be shipped in collapsed form like folding cartons. The packer plants using the containers with, which to distribute their products do not require the use of any liquid adhesives for application to the closures, a dry non-tacky film of adhesive having been already provided to the container.

The method of this invention provides for greater efficiency and hygiene in closing containers and especially when they are used to carry food-stuffs. The range of temperature of heat employed to seal the closures is sufficient to sterilize the closure.

Other types of containers fabricated of foldable materials may employ the method hereinbefore described without departing from the method of this invention. A separate coated member may be inserted and disposed intermediately of the other folded members comprising the closure whereby, the separate coated member provides a sealing gasket within the closure.

The method and illustrations used in describing this invention provide means whereby wicking raw edges of material are avoided in the structure of the closure. The folded wings 17 (Fig. 4) provide turned corner edges 20 within the container, the edges 10, 11 and 22 are sealed in face to edge abutments to their engaging surface areas. The liberally pre-coated adhesive upon the said edges and hinged junction 8 when activated, becomes viscous and provides a sealing medium to the abutted edges '22 of the folded wings 17.

The sheet material or container blanks of which the containers are fabricated may be treated or laminated with plastic materials such as, polystyrene, polyethylene, saran and other similar suitable plastic materials. The hot-melt adhesives used may be compounded to be compatible for sealing purposes to the plastic material desired. The container may be waxed if desired for low cost protection of container contents and a hot-melt adhesive employed comprised basically of wax and ethyl cellulose materials with which to provide the sealing gasket in the closure. When the containers are treated as heretofore described, the mechanical contacting part used to apply either pressure and/or heat to the closure for activating the sealing gasket adhesive, may be treated with Teflon." This material when baked upon the apparatus surface will avoid any sticking or fouling of the surface when withdrawn from the closure.

The sealing gasket-type element between the juxtaposed portions of the closure receives heat to activate the sealing medium of the element. The heat in-put to the closure for sealing purposes may be regulated for temperature and time to also sterilize the closure. The activated adhesive may be cooled to set almost instantly and provide an efficiently sealed closure having a resilient structure to withstand any rough handling of the container.

The blanks of folding carton type containers are folded in flat overlapping relationship to form a longitudinal body seam. In this fiat form the panels 6 may be folded outwardly at right angles to the flatly folded body for dipping into the bath of adhesive substantially as illustrated in Figs. 1 and 1a of the drawings. The body of the container 5 will not be open but collapsed. This method of handling the containers for treating the panels 6 with adhesive simplifies the handling and conveyor mechanism for carrying the containers through the panel coating operation.

Although a single embodiment of the invention has been illustrated in the accompanying drawings, it is to be expressly understood that various changes may be made therein without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

I claim:

1. The method of forming and sealing a substantially rigid closure for a container having an open end and a plurality of substantially rigid side walls arranged in opposing pairs to provide a rectangular cross section, one pair of said side walls being provided with integral first foldable closure forming wall portions and the other adjacent pair of side walls being provided with integral second and third foldable end closing substantially rigid panels, which comprises bathing all surfaces and edges of said second foldable end closing panel with a thermoplastic adhesive while said adhesive is in molten condition, smoothing surfaces of the bathed panel prior to the solidifying of said adhesive, folding each of the pair of said first wall portions inwardly, upwardly, outwardly and downwardly to bring like marginal portions of the folds into self-superimposing relationship, thereby providing a pair of inwardly opposing rip-springing closure wall seating ledges with their opposing side edges substantially abutting adjacent interior surface portions of said foldable end closing panels, flattening downwardly the portions of said self-superimposing margins adjacent the folding line of said second bathed panel and then folding said bathed panel inwardly and downwardly, bringing the adhesive surface thereof upon up-facing surfaces of said margins, thereby causing opposite side edges of like margins to form abutting relationship upon the upper interior face of adjacent opposing side walls, folding said third panel inwardly and downwardly upon the adhesive face of said folded second panel, applying heat and pressure upon the exterior face of said third panel while said pressure is being firmly resisted by the up-springing tendency of said first folded like margins causing said heat to activate the adhesive to bonding condition upon all surfaces of the inner disposed second panel, thereby completely sealing the closed end of said container by the activation of the adhesive provided exclusively upon the folded second rigid panel and by the resistance exerted upon said panel surface engagements by the resiliency of said ledges.

2. The method of forming a closure for a container having a plurality of side walls with foldable end segments, said end segments comprising first and second foldable full end closing panels, the first of which constitutes a sealing element adapted to be dip coated with molten hot-melt thermoplastic adhesive free of solvent, and a pair of foldable closure ledge forming wall portions that will resiliently and firmly resist surface contact with said element for closure sealing purposes when being folded in sequence stages to form the structure of said closure, said method comprising positioning said first panel out of plane with respect to the associated side wall of said container, dipping said first panel in and out of a bath of said molten adhesive, upon solidification thereof, replacing the coated panel substantially in original position to constitute the sealing element, folding each of said pair of ledge forming wall portions inwardly of the associated side wall of said container, then folding a like portion of said ledge upwardly, outwardly and downwardly upon a first folded portion to provide a pair of inwardly opposed sealing element seating ledges that are resiliently active, folding said sealing element downwardly upon the up-facing portion of the flattened ledges, said ledges having a constant tendency to spring upwardly thereby imparting a substantial strong flexing resistance upon the adhesive coating of corresponding surface contact made by the sealing element, temporarily confining the position of said element upon the ledges, and folding said second panel downwardly upon the adhesive surface of said element and initiating permanent confining of the contacting engagement of the element and flattened. ledges while heating and pressing the exterior surface of said second panel to activate said adhesive, thereby uniting said closure of the container by said sealing element in seam forming relationship.

3. The method of forming a closure for a rectangular shaped container made of paper board sheet material and having four side walls arranged in opposing pairs, each pair having integral foldable wall portions that define an open end, comprising folding each wall portion of one pair of said side walls to dispose a relatively narrow width margin inwardly of the corresponding side wall and then folding a like margin upwardly, outwardly and downwardly in superimposing relation upon said first folded margin, the end edge of the last folded margin being disposed in substantial alignment with the first corner fold that defines the top edge of the corresponding side wall, thereby providing a pair of inwardly opposed pressure resistant seating ledges for a transverse foldable end closing panel having pre-applied dry thermoplastic adhesive coated over all surfaces and side edges thereof to constitute the sole bonding means with which to seal said closure, folding said end closing adhesive treated panel inwardly and downwardly upon upper faces of said pressure resistant seating ledges, compressing said ledges downwardly prior to said contacted engagement, folding a foldable panel opposed to the folded end closing adhesive coated panel inwardly and downwardly upon the exterior surface adhesive thereof to thereby keep said ledges compressed and simultaneously applying heat and pressure upon said last folded panel to activate said dry thermoplastic adhesive, the activated thermoplastic adhesive sealing said closure effectively by the constant upspringing tendency of said ledges upon corresponding marginal sides of said adhesive coated panel which is resisted downwardly by the last folded panel.

4. The method of forming and sealing a resilient closure in a container having an open end and a plurality of side walls arranged in opposing pairs to provide a body portion of rectangular horizontal cross section, said side Walls each having integral foldable closure forming wall portions, and one of said portions being adapted to constitute a rigid end closing and sealing element to be embodied in said closure, said method comprising coating opposing surfaces and side edges of said one foldable wall portion with molten hot-melt thermoplastic adhesive, thereby constituting said sealing element prior to the forming of said closure, forming said closure by first folding each wall portion of one pair of said side walls inwardly, upwardly, outwardly and downwardly thereby bringing the end edge of the folded portions coplanar with the surface of the corresponding side wall, and the opposing side edges of the folded portions into abutting relation with the interior face of an adjacent pair of said side walls, thereby to provide a pair of inwardly opposed resiliently active ledges upon the top of the corresponding side walls to firmly resist contact of said sealing element when folded, flattening said pair of ledges adjacent the lower fold line of the sealing element, then folding said element to close said open end of the container while bringing the adhesive into surface contact upon the up-facing surface portions of said ledges, bringing the longitudinal adhesive coated end edge of the element into meeting relation with the interior face of one of said adjacent side walls and into coplanar surface relationship with the adjacent lower side edge portions of said ledges, folding the remaining closure forming wall portion at right angles over said adhesive coated end edge and upon the up-facing surface adhesive of the sealing element, subjecting said element to heat to soften said adhesive coated surfaces thereof to bonding activated condition, pressing downwardly upon the exterior surface of said last folded wall portion against the resistance afforded by the spring resiliency exerted upwardly by said element seating ledges while said activated adhesive is solidifying thereby bonding said closure into tight seam forming relationship due to the co acting pressure effects upon the embodied rigid sealing element exerted by the constant resilient activity of the ledges in surface contact therewith and the opposite constant pressure exerted by said last folded wall portion of the closure.

5. The method as set forth in claim 4 wherein the activated adhesive upon the longitudinal end edge of the rigid sealing element effects a seal upon the upper interior surface adjacent the right angular corner fold of the last folded wall portion, thereby augmenting said tight seam forming relationship of the closure, the right angular corner fold of the sealing element and said corner fold of the last folded wall portion keeping adjacent lateral surfaces of said abutting end edge and edges of said ledges compressed flatly together, thereby further augmenting the sealing of said closure.

6. The method of forming an exclusive seal bonding rigid element in a closure for a container of paper board material, and of providing co-acting means in the structure of said closure with which to make said bonding element effective in sealing said closure in positive tight seam forming relationship, said container having four side walls arranged in opposing pairs to provide a tubular body of rectangular cross section and each pair of side walls of said tubular body being provided with foldable closure forming integral wall portions, said method comprising subjecting the one of said foldable wall portions that is to constitute said seal bonding element to a coating over all surfaces and edges thereof with a thermoplastic film of activatable adhesive substantially free of solvent, and when dry, composed of substantially 100% solids, and thereby forming said bonding element prior to the forming of said closure of the container, folding a first pair of said closure forming wall portions into superimposing like marginal relationship so that said margins have contant tendency to spring upwardly and thereby provide a pair of inwardly opposed flexible resisting closure wall seating ledges of relatively narrow width to enhance said resisting activity; compressing said ledges downwardly while folding said seal bonding rigid element downwardly upon said ledges thereby bringing the surface portions of the dry adhesive of said element into contact upon the up-faces of said ledges; then compressing said elernent and ledges downwardly while folding the other foldable wall portion downwardly upon the surface adhesive of the folded seal bonding element, subjecting said last folded panel to heat and while heating, pressing the panel downwardly, upon the bonding element against the resistance to downward movement alforded by saidledges and thereby causing said adhesive on said element to be activated tin surface bonding condition, the resisting effects upon opposite surface sides of the rigid sealing element imposed upwardly by the resilient ledges and downwardly by said panel pressing, insuring positive sealing of all surface areas of said contacts formedrin said'closure of the container in tight seam forming relationship.

7. The. method as set forth inclaim 6 wherein the opposing side edges of said resilient ledges are brought into abutting relation with the corresponding interior surface portions of the adjacent side walls, and the adhesive coated end edge of the sealing element is brought into coplanar surface relationship with the lower adjacent abutting side edges of said ledges, said activated adhesive sealing said end edge upon the interior surface of the adjacent side wall of said container thereby augmenting the positive sealing of said closure.

8. The method 'of forming and sealing a closure for a substantially rigid container having four side walls provided with foldable end segments, said side walls being arranged in opposing pairs to provide a tubular body portion of rectangular cross section with an open end, said end segments comprising a pair of foldable side wall marginal end segments, a second foldable end closing sealing segment having pre-applied and pre'dried adhesive,1said pair of foldable side wall marginal end segments being adapted to form pressure resisting seats for said second foldable end closing sealing segment, and a third foldable segment which applies downward pressure upon said pair of pressure resisting end segments when folded to form said closure, said. method comprising dip coating all'surfaces and side edges. of the second foldable t segment with thermoplastic adhesive; removing the surplus and drying said adhesive, folding a portion of the pair of opposing marginal end segments inwardly, and then bringing a like marginal portion of said pair of end segments into superimposing relationship upwardly, outwardly and downwardly upon .theinwardly disposed mar ginal portions, the free end edge of said second portion being coplanar with its associated side wall, thereby providing a pair of up-springingclosure wall seating ledges, temporarily flattening said ledges downwardly while folding said second adhesive treated end closing segment in order to bring the dry adhesive downwardly upon the up-facing margins of said ledges; temporarily holding said second segment downwardly upon the ledges while folding the third segment into overlapping relationship with the adhesive surface of the folded second segment, and heating said third segment to bringsaid adhesive to bonding condition while pressing said third segment against the resilient resistance afforded by said first folded ledges, thereby uniting said closure in tight bonding seam forming relationship.

References Cited in the file of this patent UNITED STATES PATENTS 1,803,951 Thoma May 5, 1931 2,097,515 Chambless Nov. 2, 1937 2,335,865 Lanigan et al. Dec. 7, 1943 2,341,845 Mark et al. Feb. 15, 1944 2,556,008 Spalding June 5, 1951

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