US3908890A

US3908890A - Heat sealable carton and method of forming same

Info

Publication number: US3908890A
Application number: US244119A
Authority: US
Inventors: Thomas R Baker
Original assignee: Kliklok LLC
Current assignee: Kliklok LLC
Priority date: 1972-04-14
Filing date: 1972-04-14
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30
Also published as: JPS5652776B2; DE2308870C2; GB1424035A; IT982134B; NL7301627A; FR2179729A1; BR7302687D0; DE2308870A1; ES411335A1; JPS4916577A; FR2179729B1; ES438527A1

Abstract

A carton of paperboard or the like has thermoplastic adhesive applied to the surfaces to be bonded and employs major end panels, end flaps and minor end panel strips to form a leakproof carton with a minimum size flat stock blank. In the blank, the end flaps are articulated to the opposite sides of the bottom panel for bonding to the major end panel and with a guide tab to guide said flaps during folding. A minor end panel strip overlies the free edge of the major end panel to complete the sealed carton. Embossed fold beads cooperate with free edges to enhance sealing efficiency and the panel forming slits are spaced from the center line of the beads to provide further caulking of the joints. Blanks are oppositely directed on the flat stock with the major and minor panels, and the guide tabs being contiguous to each other for conservation of material. Hot air nozzles are provided at a process station to activate preapplied thermoplastic material on not only the panels, but also on the fold beads.

Description

United States Patent 1191 Baker 1451 Sept. 30, 1975 1 i HEAT SEALABLE CARTON AND METHOD OF FORMING SAME [75] Inventor: Thomas R. Baker, Los Altos, Calif.

[73] Assignee: Kliklok Corporation, Greenwich,

Conn.

22 Filed: Apr. 14, 1972 211 Appl. NO.I 244,119

152] US. Cl 229/37 R; 229/33; 229/16 R; 229/48 T; 229/48 R [51] Int. Cl B65d 5/02; 865d 5/22 [58] Field of Search 229/37 R. 33, 48 SC, 48 T. 229/48 R. 16 R. 38

[56] References Cited UNITED STATES PATENTS 2.373.701 4/1945 Meredith 229/33 2,485.235 10/1949 Graf 229/37 R 2.496.043 l/l950 Farrell 229/37 R 3.198.416 8/1965 Hickin et al. 229/48 R Primary ExaminerWilliam 1. Price Assistant E.\zuninerDouglas B. Farrow Attorney. Agem, or Firm-Lowe, King & Price [57] ABSTRACT A carton of paperboard or the like has thermoplastic adhesive applied to the surfaces to be bonded and employs major end panels. end flaps and minor end panel strips to form a leakproof carton with a minimum size flat stock blank. In the blank, the end flaps are articulated to the opposite sides of the bottom panel for bonding to the major end panel and with a guide tab to guide said flaps during folding. A minor end panel strip overlies the free edge of the major end panel to complete the sealed carton. Embossed fold beads cooperate with free edges to enhance sealing efficiency and the panel forming slits are spaced from the center line of the beads to provide further caulking of the joints. Blanks are oppositely directed on the flat stock with the major and minor panels. and the guide tabs being contiguous to each other for conservation of material. Hot air nozzles are provided at a process station to activate preapplied thermoplastic material on not only the panels, but also on the fold beads.

13 Claims, 14 Drawing Figures Sept. 30,1975 Sheet 1 of 3 3,908,890

U.S. Patnt US. Patent Sept. 30,1975 Sheet 2 of3 3,908,890

F/. Z4 ELEM US. Patent Sept. 30,1975 Sheet 3 of3 3,908,890

HEAT SEALABLE CARTON AND METHOD OF FORMING SAME The present invention relates to cartons for effective holding of liquid or semi-liquid products and the method of forming the same, and more particularly, to improvements relating to a carton wherein effective sealing for liquid tightness is accomplished with a minimum size blank.

BACKGROUND OF THE INVENTION In the carton or box forming art, there have been several attempts to design, and effectively machine form at high speeds, a carton that is fabricated of a minimum size blank for greatest economy, while at the same time assuring liquid tightness for packaging of liquid or semi-liquid products that may then be immediately frozen. These attempts have met with only limited success so that prior to the present invention a commercially acceptable carton for low cost food items packed in liquid, such as frozen vegetables, fruits and fish, has still eluded the most inventive minds in this art, insofar as I am aware. In almost all instances, the main problem has been the difficulty of getting liquid tightness while maintaining a premium on minimum blank size, and thus economy, as well as high speed forming machine operation (in the order of 80 boxes/minutes).

Routes of escape for liquid in a folded box occur in several ways, and these routes tend to be harder to consistently close under production conditions as the amount of stock in the carton is attempted to be reduced. Most prevalent perhaps is the triangular leakage channel that is created when two or more overlying flaps or panels are lap sealed to each other. The leakage channel is formed where one flap or panel must step down a board thickness to the other flap. In other instances, lap joints are avoided by abutting adjacent edges of flaps together and then covering this joint with still another flap. This is somewhat more expensive in terms of paperboard used, and leakages persist; the liquid following the path along the abutment and out through the side of the joint or the corner of the carton. An example of this known type of carton is shown in the U.S. Pat. to Phin, 3,021,043, issued Feb. 13, 1962.

Invariably, designers have always gone back to more expensive carton designs with a decidedly greater bulk of stock blank, such as designs involving gussets and/or several layers of paperboard (such as used in conventional milk cartons) in order to avoid leaks. The only other alternative previously available, and one that is comparatively expensive but nevertheless one that has been used often in the past because of the lack of anything better, is the separate sealed poly-pouch as a lining for the box. A need for an advancement in this art 5 was and is self evident.

OBJECTIVES oF'f THE INVENTION form leakage channels or corner pinholes when the car-,

ton is formed.

It is still another object of the present invention to provide a carton wherein the edges of the panels and flaps cooperate with the corresponding embossed fold bead to ,provide a liquid-tight seal.

It is still a further object of the present invention to provide a method for forming the carton that is intimately related to the novel carton in that the free edges and fold beads of the end panels are activated with adhesive to enhance the efficiency of the sealing operation on the carton.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the present invention, a foldable carton or box utilizing a minimum size stock blank is adapted for efficient formation by machine and is liquid-tight. The size of the blank for a give size carton is not only minimized, but the blank is also designed for nested cutout of multiple blanks from sheet stock with minimum wastage.

The carton of the invention is characterized in one aspect by elimination of all overlaping joints or seams and the elimination of pinholes in the corners of the box that have plagued liquid-tight carton formation in the past. An end flap articulated to the bottom panel of the carton is folded up first along the end of the carton, it being understood that both ends are formed the same so that only one needs to be discussed. The flap is held erect at a process station where activation of the adhesive coating takes place. This is accomplished by a guide tab that engages the top of the adjacent hot-air nozzle box, which eliminates marring of the board by preventing hot metal contact in the critical seal area. The tabs are further used to assure final guidance by the major end panel as it swings around during folding for bonding to said flap. The major end panel bonded to the flap seals the carton at the one corner and along the bottom thereof.

A minor end panel strip is folded over the free edge of full width end panel to form the side seam and to seal the remaining corner of the bottom of the carton. Advantageously, the edge of the major end panel abuts the internal score bead formed along the panel strip to enhance the sealing of the side seam. Similarly, the end flap abuts the fold bead formed by the major end panel along a defined distance so that the bottom of the container is effectively leakproof.

The guide tab is triangular and provided immediately above the area of the hot air activated adhesive strip. This guide tap is adhesive-free (not activated) and is engaged by the major end flap as the same is folded over in order to prevent the end flap from springing back or flying out of its initially folded position. An adhesive strip area across the inside bottom of the end panel cooperates with the strip along the outside bottom of the end flap to form the secure, leakproof bond desired. The panel strip is next plowed into final positionoverlying the free edge of the major end panel and the carton is subjected to compression (as is conventional for setting of the seals. Y

Preferably the carton is of the precoated type with the coating material being activated to a tackiness condition to form an adhesive by blowing of hot air onto the surface. Paperboard of acaliber' of approximately 15 points (15 thousandths of an inch), uncoated, havcoating may be selectively provided, for example, along the convex surfaces of the fold bead to give these areas higher sealing and caulking efficiency. For a more detailed description of this type of carton, reference is made to an earlier Hoyrup et al US. Pat. No. 3,394,635, issued July 30, I968 and owned by the same assignee as the present application.

The sealing efficiency of the carton of the present invention is enhanced by providing specific length slits in the paperboard stock to define the panels, i.e., slits are provided that terminate approximately at the outside edge of the bead. This structure induces advantageous compressing and crushing of the paperboard and the thermoplastic material along the score bead for greater caulking action. Secondly, the feature tends to cause a pucker of the fold bead at the corner area, which puckering of the material exactly at the corner of the package effectively and efficiently eaulks the pinholes that normally occur in other carton designs.

In accordance with the method steps relating to the novel carton and more particularly to the same basic concept of providing greater sealing efficiency is performed by (l) placing the blank at the process station, (2) applying adhesive to the selected carton portions including the free edges and the cooperating fold beads, and then (3) folding the end panels and flaps into engagement with the free edges in abutment for the greater sealing efficiency. The panel strip, which is folded into position last, is heated across its full expanse, and in the same process step, the fold bead is heated to cause tackiness of the coated material. Also, the heated air applied to the bottom of the end flap is advantageously deflected in toward the ends of the carton blank to the adjacent fold beads to further insure the effectiveness of the free edge-to-fold bead and the corner seals.

Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein l have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by me of carrying out my invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a layout view of a carton blank formed in accordance with the principles of the present invention and showing the surfaces forming the inside of the finished carton;

FIG. 2 is a perspective view of the carton blank of the invention positioned on a forming die or folding head in readiness for folding in accordance with certain carton structure and method aspects of the invention;

FIGS. 2A2D are detailed cross sectional views taken along corresponding lines 2A2A through 2D2D of the heating manifolds of the die showing the application of adhesive activating hot air to the seal areas further in accordance with the invention;

FIG. 3 is a view of the carton in a partially folded state showing further important aspects of the invention;

FIG. 4 is a perspective view of the finished carton;

FIG. 5 is a cross sectional view taken along line 55 of FIG. 4;

FIGS. 5A-5B show the final folding and sealing sequence along the outside panel strip and in cross section at line 5-5A, 8;

FIG. 6 is a layout of the blanks for cut-out from a single piece of board according to a feature of the invention; and

FIGS. 7A and 7B are enlarged showings of the embossed fold beads and panel forming slits, and the corncr sealing effects thereof, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to the drawings in composite and particularly starting with FIG. 1, a more complete and detailed description of the important features of the present invention can be given. A blank 10 is shown in FIG. I with the side forming the interior of the carton or box facing up. The blank includes a grid S of score lines along the width and length of the blank and slits ll, 12 at the sides of the blank 10, which together define the plurality of panels and flaps of the carton.

Specifically, a bottom panel 13 is provided with side panels l4, l5 articulated along parallel score lines to the sides thereof. To the other two sides of the side panel 15 are attached major end panels l6, 16'. The slit 12 in the blank 10 delineates one side of an end flap 18, I8 articulated to the sides of the bottom panel 13; the opposite edge of the end flap l8, 18' being defined by the slit 11. Minor end panel strip l9, 19' form the remainder of the novel portion of the blank 10.

A major top panel or closure 20 with gusseted end flap 21, 21' is provided at one end of the blank 10. A minor top flap 22 that may include an appropriate tear strip for ease of opening is positioned at the opposite end to complete the blank 10.

The carton blank just described is fabricated of paperboard, preferably of a caliber of approximately 15 points or 15 thousandths of an inch (approximately 0.3 millimeters). The blank is coated on both sides with a relatively thin coating of a thermoplastic composition, such as polyethylene or other synthetic plastic materials. Alternatively, the board may be coated with compositions including high melting point waxes. The coating must provide a good moistureproofing characteristic to the paperboard, and must provide a satisfactory heat bond when the coating is heated by hot air (so as to become tacky) and then pressed together with an adjoining part of the carton. The coating must also be sufficient to form caulking at the sealed joints in accordance with the invention. A coating of 4 pounds per 1,000 square feet of stock on the inside of the carton and 3 pounds per 1,000 square feet on the outside has been found to meet these objectives although it is to be understood that this may be varied to suit the specific application of the resulting carton as desired or necessary.

FIG. 2 illustrates a process station at which the thermoplastic coating preapplied to the carton blank may be suitably activated to form an adhesive. Generally, a manifold complex 30, 30 is provided on each side of the station to supply heated air, preferably at extremely high temperatures in the order of 900 F. to I00O F. for very brief periods of time. Nozzle boxes receive such heated air from a source as indicated, and direct the air against the blank, at thedes'ire'd locations. These nozzle boxes have been designatedby reference numerals 31-33 and 3l'33, as shown in FIG. 2. The nozzle boxes have slotted or multiple aperture openings therein to release the heated air immediately adjacent the blank to heat the thermoplastic coating to a state of tackiness so that it then becomes an activated adhesive.

The

nozzle boxes

31, 31 release air to the region of the edge along the major end panels 16, 16' through a suitable slotted orifice 35 to form an adhesive area A as clearly shown in FIG. 2A. The air is directed to the underside of the blank (shown by light shading in FIG. 1) and directed for full heating of the edge that forms an important part of the side seam seal, as will later be seen. The amount of excess heating of the interior area of the blank is also advantageously minimized by the outward direction of the nozzle 35.

The second nozzle box 32, 32' (FIG. 28) serves to eject air on the lower portion of the major end panels l6, 16' to form the seal strip area A This area A is shown by heavy shading in FIG. 1 since it is formed on the near side of the blank 10. The slot 36 is directed downwardly to thus engage the region of the end panel adjacent the bottom of the cartonjApertures 37 also in box 32, 32 may be seen in FIG. 2B, which apertures perform the function of ejecting hot air against the upturned end flaps 18, 18, as shown in FIGS. 2 and 2C. It should be noted that the springiness of the board serves to hold the flaps at an acute angle to the face of the box 32, 32' so that only the lower portion of the flaps 18, 18' are heated, and thus only a limited strip A of adhesive is activated on these two parts of the blank. In FIG. 1, the full width area lying between the slits ll, 12 is the area necessary to have activated adhesive. Also, the flap 18, 18' advantageously deflects a portion of the hot air around the sides and onto the grid S of score lines immediately adjacent thereto so as to activate or enhance the activation of the coating in areas A A for a purpose that will presently be seen.

The

nozzle box

33, 33, shown in FIG. 2D, ejects air from a downwardly directed slot 38 across the full width area A of the

panel strip

19, 19 and in addition includes the adjacent score lines S, also for an important reason that will more fully appear below.

The blank 10 of the present invention is particularly adapted by the shape of its panels to be formed on high speed, automatic machinery of the plunger and die type. Basically, the blank 10 may be positioned on the top of the die, at the process station shown in FIG. 2, in readiness for the application of a plunger to engage along the bottom panel 13. This serves to draw the blank 10 through the throat of the die causing the

side panels

14, 15 to be erected to the upstanding position and the end panels 16, l6, l9, l9 and end flaps 18, 18' to be folded to their overlying positions for bonding together. As can be now basically understood from viewing FIGS. l-3 of the drawings, the areas A A are bonded to each other to form the bottom of the box, and areas A,, A are bonded to form the side seam (see FIG. 4 also).

During the adhesive activation process step and the early stages of the folding operation through the forming die, the end flaps 18, 18' are held in the upright angled position. as shown in FIGS. 2 and 2C, by the upper edge of the nozzle box 32, 32. This is made possible'by novel guide tab 40 that extends abo'vethe seal area A By holding the

flap

18, 18 away from the hot face of the nozzle box 32, 32 and with only line contact along the upper edge, the tacky adhesive in area A is not disturbed, the chance of the flap sticking to the face is obviated and buildup of adhesive on the nozzle box face is practically eliminated. The triangular shape of the

tab

40, 40 gives progressively greater strength near the base thereof for maximum bending resistance as the flap is erected when the blank 10 is placed in position by the transport device (not shown). Also, only point contact of the apex or top of the

tab

40, 40 is assured as the final movement down into the die takes place, thus assuring against significant adhesive transfer to the nozzle box 32, 32'.

The

tabs

40, 40 are also functionally important in the downward folding process immediately after the box 32, 32' is cleared. At this point it is important that the flaps 18, l8'-not be allowed to fly back because of the springiness in the board to their original position. The

guide tab

40,40 prevents this.

Vertical edge

41, 41 of the tab (FIG. 3) is captured and held in the proper relationship by the end panels 16, 16' as they are plowed into position along the end of the carton. Since the adhesive has been activated only along the strip A the guide tab has substantially free sliding movement over the corresponding panel 16, 16' (see FIG. 3). The cooperating heated areas A A., with the tacky adhesive come together at the end of the guiding movement and form a watertight bond and seal. The sliding

edge

41, 41 gathers excess adhesive in the areas ,A A, for concentration at the corner for enhancing the seal formation in the area A, along the score line as desired.

With reference to FIG. 5, a full discussion of the concept of the present invention concerning enhancing of the sealing efficiency can take place. In a nutshell, this concept employs abutting the free edges of the carton portions snugly into engagement with raised fold beads 50 that form the grid S and forming a caulking" line at these points.

First, the nature of the embossed fold beads that forms all of the score grid S of the blank should be fully understood and can be seen in FIG. 2D. In this figure, the embossment or fold bead 50 that delineates the line between the side panel 14 and the minor end panel strips 19, 19 is shown. As can be seen in this figure, the raised or convex surface of the embossment is on the inside side of the carton blank, and the concave portion is on the outside. This is of importance since the raised surface forms an abutment for interaction with the free mating edge of the cooperating carton portion.

Thus, with reference back to FIG. 5, the major end panel 16 can be seen as having its free edge abutting the raised fold bead 50 so that a definitive sealing line is formed on the interior side of the carton along the full height of the package. FIG. 5A shows in enlarged detail how the major end panel 16 is brought toward the fold bead 50 by the plunger and die mechanism of the carton forming machine; it being understood that such mechanism is not shown or described herein, but is adequately described in the prior art aforementioned I-Ioyrup et al. US. Pat. No. 3,394,635 and incorporated herein by reference. As the free mating edge of the end panel 16 is moved toward its final sealing position, the panel strip 19 is being closed into overlying engagement therewith. The outer face area A of the major end panel 16 has had the thermoplastic coating transformed into activated adhesive (see FIG. 2A); whereas, the area A A has activated adhesive across the full expanse of the panel strip 19, and also importantly, the raised fold bead 50, all as explained above. Although it has been exaggerated for illustrative purposes in FIG. 5B, an excess of thermoplastic sealing material forming a caulking line 53 is formed in the niche at the point of abutment between the free mating edge and the bead 50. This caulking line 53 is noted to be at the interior of the carton l0, and thus forecloses any chance of leakage of material to the exterior of the panel 16.

It is noted that because of the effectiveness of the caulking line 53 that the seal areas A A that need be activated and the width of the minor end panel l9, 19 may be held to a minimum. The prime prerequisite is that the free edge be heated sufficiently to assure full activation of the abutting joint. Another important advantage lies in the fact that as the panel 19 is folded over, the convex surface of the fold bead 50 is being compressed and the thermoplastic material thereon is being concentrated in the important area for forming of the caulking line 53. Also, as the edge abuts the bead 50 a crushing effect is also believed to take place assuring that the mating relationship is complete. Since this area is the critical sealing line for assuring against leakage, it is contemplated that an extra thickness of coating could be advantageously added to the carton blank 10 along the bead 50. Any extra coating thickness can be determined by the nature of the specific carton, the viscosity of the material being packaged and other factors.

At the far side of the carton or adjacent the side panel 15, a similar fold bead and free edge abutment seal is formed. In this instance, the upwardly extending edge 41 in the region of the seal area A is mated with the fold bead 60 formed in the juncture between the major end panel 16 and said side panel 15. An upwardly extending caulking" line 55 is formed in this area to seal this corner of the box. Since there is no side seam to be formed at this juncture, the effective sealing area A A, need be extended only a relatively short distance up the side, as can be seen clearly in FIG. 1. The guide tab 40 above the seal area A A is left free of activated adhesive for its guiding function, as previously set forth above. it is noted at this point that the sealing with caulking lines or joints formed by the free edge and fold bead abutment concept as just described, has eliminated the prior art lap joints that require the stepdown of panels and that cause leakage channels.

FIGS. 7A and 7B show the construction for improved sealing of the four bottom corners of the carton. The sealing of the corners is important to prevent leakage through pinholes that heretofore have resulted when the three panels of a carton come together to form a point. This concept constitutes terminating the slits l 1, 12 approximately at the outer limit of fold bead 70 (a distance AX from the center line). In effect, this feature Causes corner fold beads, that is, intersecting

fold beads

70, 71, (shown in FIG. 7A) to pucker or gather toward the corner. This excess material and the activated thermoplastic coating caulk the corner thereby assuring a tight seal and elimination of any tendency for a pinhole to develop, as can be seen in FIG. 7B. To further explain, as the end flap 18 is folded up and the side panel is folded up to meet the same, after the corner areas A.,, A have been thoroughly heated by the flow of hot air, the compressed material and activated adhesive of the

foldbeads

70, 71 converge at approximately 45 angle and actually project into the corner, thus causing total occlusion.

In one exemplary carton blank manufactured in accordance with the present invention, the embossed beads 60, were approximately 2 millimeters in width and the distance AX of approximately I millimeter was adopted. Generally speaking then, the slits ll, 12 are patterned to terminate at the outer limits of the score beads which has been found to give a satisfactory sealing of the corner of the box.

The approach for minimization of wastage when cutting the carton blanks from flat stock is shown in FIG. 6. The adjacent carton blanks 10 are oppositely directed so that the major end panel 19 of one is contiguous to the minor end panel 16 of the adjacent carton 10. Further, the end flaps 18 are contiguous to each other. In effect then, the wastage is limited to the very small cutouts formed at the ends of the tope of the package, and each portion of the blank remaining is functional, as set forth above, so that the blanks 10 fully meet the important objective of conservation of the paperboard.

In summary, the carton 10 of the present invention has been shown to accomplish results and advantages not heretofore gained in the art. The carton is not only characterized by its design for minimum size blank for a given carton size and minimum paperboard wastage, but most importantly, this has been accomplished while forming a box that eliminates leakage channels and pinholes for true leakproof construction. The

fold beads

50, 60 cooperate with the free mating edges of the carton panel and

flap

16, 18, respectively, to assure the formation of the liquid-tight seals that are aided by the special caulking characteristics. The end flap 18 has guide tab 40 that assures proper adhesive activation and positioning of said flap with respect to the major end panel 16 in proper underlying relationship therewith.

In this disclosure, there is shown and described only the preferred embodiment of the invention, but, as aforementioned, it is to be understood that the invention is capable of use in various other combinations and environment and is capable of changes or modifications within the scope of the inventive concept as expressed herein.

I claim;

1. A foldable carton of paperboard or the like having overlying panels to be bonded to each other by thermoplastic adhesive material on at least one of each pair of the surfaces to be bonded comprising a bottom panel, a pair of major side panels articulated to opposite sides of said bottom panel, major end flaps articulated to the other two sides of said bottom panel, major end panels articulated to two upstanding edges of one of said side panels, the width of said end panels and said end flaps being substantially the same as said bottom panel for full overlap, minor end panel strips articulated to the upstanding edges of the other side panel to overlie the free edge of said major end panels, said end flaps having a thermoplastic adhesive material strip across the full width thereof adjacent said bottom panel for bonding to said major end panel, and said end flaps each including a guide tab above said strip only on the side adjacent said major endpanel for extended engagement with said end panel for guiding the same during folding,

said carton being formed of blanks cut from flat stock, adjacent blanks being oppositely directed with the major end panel of one beiing contiguous with the minor end panel strip of the other, said end flap including said guide tab of one blank being formed in the stock contiguous to said end flap including said guide tab of the of the other blank, and the adjacent guide tabs on the flat stock being defined by a diagonal bisecting line, whereby said tabs are triangular to give maximum resistance to bending during folding and simplicity of blank cutting and whereby a full sealed bottom is assured while paperboard is conserved.

2. The carton of claim 1 wherein said carton has said panels and end flaps delineated by embossed lines, the convex side of said lines being on the inside of said carton to form fold beads, the free edge of said major end panel abutting the fold bead for said minor end panel strip to assist in forming the side seal of said carton.

3. The carton of claim 2 wherein the fold bead for said panel strip has sufficient adhesive applied to form a caulking line for enhanced sealing with the mating free edge.

4. The carton of claim 3 wherein the fold bead for said major end panel ahs sufficient adhesive applied to form a caulking line with the lower portion of abutting free edge of said end flap.

5. The carton of claim 3 wherein said panel strip and its fold bead have adhesive material substantially over the full expanse thereof to further enhance the sealing efficiency of the side seal.

6. The carton of claim 2 wherein are provided slits forming said panels and end flaps, said slits only extending substantially up to the outer limit of the convex surface of said embossed lines to cause full compression of said convex surface and whereby puckering of excess paperboard and adhesive caulks the corner formed to obviate pinhole leakage.

7. The Carton of claim 2 wherein said end flap in the region of said adhesive material strip abuts the inside fold bead of the major end panel to further provide an efficient sealing relationship.

8. The carton of claim 2 wherein said fold beads are provided with adhesive material for positive sealing and caulking action.

9. A foldable carton of paperboard or the like having overlying panels to be bonded to each other by thermoplastic adhesive material on at least one of each pair of the surfaces to be bonded comprising a bottom panel, a pair of major side panels articulated to opposite sides of said bottom panel, major end flaps articulated to the other two sides of said bottom panel, major end panels articulated to two upstanding edges of one of said side panels, the width of said end panels and said end flaps being substantially the same as said bottom panel for full overlap, minor end panel strips articulated to the upstanding edges of the other side panel to overlie the free edge of said major end panels, said end flaps having a thermoplastic adhesive material strip across the full width thereof adjacent said bottom panel for bond ing to said major end panel, and said end flaps each incuding a guide tab above said strip only on the side adjacent said major end panel for extended engagement with said end panel for guiding the same during folding, said guide tab of said end flap being substantially free of adhesive material to allow relatively resistance-free guiding movement against said major end flap during folding.

10. A foldable carton of paperboard or the like having overlying panels to be bonded to each other by thermoplastic adhesive material on at least one of each pair of the surfaces to be bonded comprising a bottom panel, a pair of major side panels articulated to opposite sides of said bottom panel, major end flaps articulated to the other two sides of said bottom panel, major end panels articulated to two upstanding edges of one of said side panels, the width of said end panels and said end flaps being substantially the same as said bottom panel for full overlap, minor end panel strips articulated to the upstanding edges of the other side panel, the free edge of said major end panel abutting the inside of the fold forming the panel strip and forming a seal therewith, the free edge of said end flap abutting the fold forming the major end panel and forming a seal therewith, said folds being created along embossed lines, the convex side of said lines being on the inside of said carton to form raised fold beads, said fold beads having sufficient adhesive material applied to form a caulking line, whereby efficient sealing without leakage channels or corner pinholes, enhanced sealing along the free edge and the fold of the major end panel, and a simplified carton blank structure are realized.

11. The carton of claim 10 wherein is further provided slits forming the panels and end flaps, said slits extending only substantially up to the outer limit of the convex surface of said embossed lines, whereby to cause full compression of said convex surface upon folding of the carton, puckering of excess paperboard and concentration of adhesive to caulk the corner of the carton so as to obviate pinhole leakage.

12. The carton of claim 10 wherein said panel strip and its fold bead have adhesive applied substantially over the full expanse thereof to further enhance the sealing efficiency.

13. The carton of claim 10 wherein is formed a portion of the fold bead of said major end panel abutting the free edge of said end flap, said portion only having adhesive applied thereto to further enhance the sealing efficiency.

Claims

1. A foldable carton of paperboard or the like having overlying panels to be bonded to each other by thermoplastic adhesive material on at least one of each pair of the surfaces to be bonded comprising a bottom panel, a pair of major side panels articulated to opposite sides of said bottom panel, major end flaps articulated to the other two sides of said bottom panel, major end panels articulated to two upstanding edges of one of said side panels, the width of said end panels and said end flaps being substantially the same as said bottom panel for full overlap, minor end panel strips articulated to the upstanding edges of the other side panel to overlie the free edge of said major end panels, said end flaps having a thermoplastic adhesive material strip across the full width thereof adjacent said bottom panel for bonding to said major end panel, and said end flaps each including a guide tab above said strip only on the side adjacent said major end panel for extended engagement with said end panel for guiding the same during folding, said carton being formed of blanks cut from flat stock, adjacent blanks being oppositely directed with the major end panel of one beiing contiguous with the minor end panel strip of the other, said end flap including said guide tab of one blank being formed in the stock contiguous to said end flap including said guide tab of the of the other blank, and the adjacent guide tabs on the flat stock being defined by a diagonal bisecting line, whereby said tabs are triangular to give maximum resistance to bending during folding and simplicity of blank cutting and whereby a full sealed bottom is assured while paperboard is conserved.

9. A foldable carton of paperboard or the like having overlying panels to be bonded to each other by thermoplastic adhesive material on at least one of each pair of the surfaces to be bonded comprising a bottom panel, a pair of major side panels articulated to opposite sides of said bottom panel, major end flaps articulated to the other two sides of said bottom panel, major end panels articulated to two upstanding edges of one of said side panels, the width of said end panels and said end flaps being substantially the same as said bottom panel for full overlap, minor end panel strips articulated to the upstanding edges of the other side panel to overlie the free edge of said major end panels, said end flaps having a thermoplastic adhesive material strip across the full width thereof adjacent said bottom panel for bonding to said major end panel, and said end flaps each incuding a guide tab above said strip only on the side adjacent said major end panel for extended engagement with said end panel for guiding the same during folding, said guide tab of said end flap being substantially free of adhesive material to allow relatively resistance-free guiding movement against said major end flap during folding.