Title:
CARTON WITH COMPOSITE WALL AND EXPANSION PANELS
Kind Code:
A1


Abstract:
An expansion panel assembly (200a) for use with a tubular carton (C). The expansion panel assembly (200a) includes means for cooperative relief, a slidable section (152a) and fixed sections (150a). Means for cooperative relief includes relief apertures (140a), expansion cuts (144a), and expansion hinges (146a). The relief apertures (140a) each span a portion of inner top panel (110) and expansion panel (136a). Expansion cuts (144a) define expansion hinges (146a), as well as expansion flap fixed sections (150a) and expansion panel slidable section (152a).



Inventors:
Holley Jr., John M. (Lawrenceville, GA, US)
Application Number:
11/379343
Publication Date:
10/19/2006
Filing Date:
04/19/2006
Primary Class:
International Classes:
B65D5/00
View Patent Images:
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Primary Examiner:
DEMEREE, CHRISTOPHER R
Attorney, Agent or Firm:
WESTROCK COMPANY (Richmond, VA, US)
Claims:
What is claimed is:

1. A carton for enclosing articles, comprising: a composite wall, comprising: an outer panel; and an inner panel secured to the outer panel such that at least a portion of the outside surface of the inner panel is fixedly secured to at least a portion of the inside surface of the outer panel; and an end wall closure, comprising: a composite end wall panel hingedly connected to the composite wall, comprising: an outer end wall panel hingedly connected to the outer panel; and an expansion panel hingedly connected to the inner panel, the expansion panel comprising: at least one fixed section, its outside surface being fixedly secured to the inside surface of the outer end wall panel; and at least one slidable section, its outside surface being disposed against the inside surface of the outer end wall panel in a face-contacting arrangement, and its outside surface being slidable from a neutral position to a stress relieving position with respect to the inside surface of the outer end wall panel.

2. The carton of claim 1, wherein the end wall panel is hingedly connected to the outer panel along a first fold line and the expansion panel is hingedly connected to the inner panel along a second fold line, the first and second fold lines being substantially coincident as to form a composite hinge.

3. The carton of claim 2, wherein the composite end wall panel is folded inwardly toward the composite wall and along the composite hinge.

4. The carton of claim 2, further comprising means for cooperatively relieving stress along the composite hinge.

5. The carton of claim 4, wherein means for cooperative relief comprises an expansion hinge flexibly connecting the fixed section to the slidable section, the expansion hinge controlling the extent to which the slidable portion slides from the neutral position to the stress relieving position.

6. The carton of claim 5, wherein means for cooperative relief further comprises an expansion cut for at least partially detaching the slidable section from the fixed section.

7. The carton of claim 4, wherein means for cooperative relief comprises at least one relief fold cut parallel and adjacent to the composite hinge.

8. The carton of claim 7, wherein the relief fold cut is formed in the fixed section.

9. The carton of claim 4, wherein means for cooperative relief comprises at least one relief aperture disposed through a portion of the expansion panel and of the inner panel.

10. The carton of claim 4, wherein means for cooperative relief comprises at least one relief aperture disposed through a portion of the slidable section and of the inner panel.

11. The carton of claim 1, wherein the composite wall further comprises a handle.

12. A carton for enclosing articles, comprising: a composite top wall, comprising: an outer top panel; an inner top panel secured to the outer top panel such that the outside surface of the inner top panel is fixedly secured to the inside surface of the outer top panel; and a handle comprising at least one handle aperture disposed through at least one of the inner and the outer top panels; a bottom wall opposite the composite top wall; an end wall closure, comprising: a lower end wall panel hingedly connected to the bottom wall; and a composite upper end wall panel hingedly connected to the composite top wall and secured to the lower end wall panel in an overlapping configuration, the composite upper end wall comprising: an upper end wall panel hingedly connected to the outer top panel; and an expansion panel hingedly connected to the inner top panel, the expansion panel comprising: a first fixed section, its outside surface being fixedly secured to the inside surface of the upper end wall panel; a slideable section adjacent to the first fixed section, its outside surface being disposed against the inside surface of the upper end wall panel in a face-contacting arrangement, and its outside surface being slidable from a neutral position to a stress relieving position with respect to the inside surface of the outer end wall panel; a second fixed section adjacent to the slidable section, its outside surface being fixedly secured to the inside surface of the upper end wall panel; a first expansion cut partially detaching the slidable section from the first fixed section; a second expansion cut partially detaching the slidable section from the second fixed section; a first expansion hinge flexibly connecting the slideable section to the first fixed section, comprising a slit extending from the toward expansion cut toward the second fixed section; and a second expansion hinge flexibly connecting the slideable section to the second fixed section, comprising a slit extending from the second expansion cut toward the first fixed section.

13. A blank for forming a carton for enclosing articles, comprising: an elongate transverse section comprising: an outer composite wall panel; a first side panel hingedly connected to the outer composite wall panel; a bottom panel hingedly connected to the first side panel; a second side panel hingedly connected to the bottom panel; an inner composite wall panel hingedly connected to the second side panel; and an end wall panel hingedly connected to the outer composite wall panel; and an expansion panel hingedly connected to the inner composite wall panel, the expansion panel comprising: a first fixed section defined in part by the hinged connection between the expansion panel and inner composite wall panel; a second fixed section defined in part by the hinged connection between the expansion panel and inner composite wall panel; at least one slidable section adjacently disposed between the first fixed section and the second fixed section; and means for cooperative relief.

14. The blank of claim 13, wherein the means for cooperative relief comprises: a first expansion cut partially detaching the slidable section from the first fixed section; a second expansion cut partially detaching the slidable section from the second fixed section; a first expansion hinge flexibly connecting the slideable section to the first fixed section, comprising a slit extending from the toward expansion cut toward the second fixed section; and a second expansion hinge flexibly connecting the slideable section to the second fixed section, comprising a slit extending from the second expansion cut toward the first fixed section.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application No. 60/672,933, filed Apr. 19, 2005, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

This invention relates generally to packaging, and in particular, to a carton having a composite wall with expansion panels.

BACKGROUND OF THE INVENTION

Many different types of paperboard cartons for enclosing products such as beverage cans and bottles are well known in the industry. When the product load is relatively heavy, carton manufacturers often reinforce all or part of the carton, such as by constructing one or more carton walls, end flaps, or end wall panels of high-bulk sheet material having a relatively high caliper, or by doubling-over the carton material to increase the thickness and durability of the resultant two-ply structure. A two-ply, hereinafter referred to as a composite or laminated structure, can be stronger than a doubly thick structure, particularly because of the adhesive layer that holds the plies together. Furthermore, a composite configuration is better able to resist scarring and deformation of the art side of the carton that can be caused by sharp edges of the products abrading or puncturing the walls of the carton. For instance, glass bottles are commonly sealed with metal crown caps having crimped annular edges that tend to scuff against the inside surface of the carton, which can cause visible imperfections to be evident from the outside of the carton. Consumers typically avoid purchasing products enclosed in packaging that is apparently damaged, often assuming that the contents are damaged as well, or generally perceiving the product to be of less value. Composite structures are useful because the inner layer of a composite carton composite carton wall tends to bear the brunt of the resulting deformation, sparing the outside surface of the outer layer.

Despite the inherent advantages of composite carton walls, there are several disadvantages to prior art efforts. In some instances, completely composite cartons have been manufactured with all walls having multiple laminated plies. Obviously, the cost of such cartons is unnecessarily increased by the excess sheet material, particularly as only certain carton walls need additional strength with respect to other carton walls. Furthermore, it can be difficult to fold a composite structure composed of two layers of sheet material with adhesive between the two plies, even if fold lines are scored into each of the layers. The adhesive resists the tendency of one layer to slide with respect to the other when the composite structure is flexed or bent, thereby generating a shear force along the layers of the composite structure. The opposing forces cause undesired stresses on the fold and on the adjacent panels, possibly precluding a clean fold, overcoming the holding power of glue applied to secure the composite panel in folded position, or otherwise impeding the operation of automatic packaging machinery.

What is needed is a carton configuration that selectively provides the added strength and thickness of a composite structure, efficiently utilizes sheet material, and provides composite portions that are easily manipulable into the desired configuration.

SUMMARY OF THE INVENTION

The various embodiments of the present invention address the identified need by providing a carton with a composite wall that is secured to adjacent walls by expansion means comprising one or more expansion panels. The expansion panels are connected to the composite wall and secured to an adjacent wall so as to prevent the layers of the composite wall from delaminating.

Advantageously, the expansion panel of the present invention includes at least one fixed section that is secured to the adjacent wall, and at least one slidable section differentiated by an expansion cut or an expansion hinge that permits the expansion panel to slide with respect to the adjacent wall to which it is attached. In certain embodiments, the expansion panel also includes relief apertures that are cut out of the expansion panel to facilitate a clean fold.

More specifically, the aspects and features of the invention are described with respect to an exemplary carton formed from a blank cut from a unitary piece of sheet material, such as paperboard. According to the invention, the blank includes an elongate transverse section comprising several panels that can be configured and secured to form several carton walls, including at least one composite wall consisting of at least an outer wall panel and an inner wall panel. An end wall panel secured to an expansion panel creates a foldable composite end wall panel that reinforces the lamination of the composite wall as part of an end wall closure structure.

The exemplary blank includes an outer top panel hingedly connected to a first side panel. The first side panel is hingedly connected to a bottom panel, which is hingedly connected to a second side panel. The second side panel is hingedly connected to an inner top panel. At each end, the inner top panel is hingedly connected to respective expansion panels. At each end, the outer top panel and the bottom panel are hingedly connected to respective upper end wall panels and lower end wall panels. The carton is erected by securing the outer surface of the inner top panel to the inside surface of the outer top panel, thereby creating a composite top wall. In this manner, the first side panel becomes a first side wall, the bottom panel becomes a bottom wall, and the second side panel becomes a second side wall. The composite top panel may include racetrack or other handle apertures disposed through both the inner and the outer top panels to facilitate carrying the carton. The outside surface of the fixed section of each expansion panel is secured to the inside surface of the upper end wall panel, thereby creating a composite upper end wall panel that is hingedly connected to the composite top wall along a composite hinge. The composite end wall panel and the lower end wall panel are folded toward one another and secured together in overlapping fashion to create an end wall closure, which may also include end flaps connected to both ends of each side wall, the outside surface of each end flap being secured to the inside surfaces of the composite end wall panel and the lower end wall panel.

According to one aspect of the invention, the configuration of the exemplary expansion panel facilitates folding the composite end wall panel along the hinged connection between the composite end wall panel and the composite top wall. The expansion panel extends from the hinged connection with the inner top panel, and has dimensions that yield at least one fixed section that is sufficient to reinforce lamination of the composite top wall. The fixed section is adjacent to at least one slidable section that is free from the upper end wall panel. An expansion hinge connects the fixed section to the slidable section, and permits the outside surface of the slidable section to slide against the inner surface of the upper end wall panel. Thus, undesired shear stress between the respective surfaces is avoided, while the advantages of the two-ply structure are maintained. More specifically, when the composite end wall panel and the composite top wall lie in the same plane, the slidable section is at a neutral first position with respect to the upper end wall panel and the fixed section. When the composite end wall panel is folded about the hinged connection with the composite top wall panel, the slidable section slides with respect to the upper end wall panel and the fixed section, to a stress relieving second position.

To reinforce the lamination of the composite top wall, the outside surface of each fixed section of the expansion panel is fixedly secured to the inside surface of the upper end wall panel, thereby creating the composite end wall panel. To facilitate folding the composite end wall panel, a slidable section is adjacent to each fixed section, its outside surface being disposed against the inside surface of the upper end wall panel in a face-contacting arrangement, and its outside surface being slidable from a neutral position to a stress relieving position with respect to the inside surface of the outer end wall panel. The slidable section also provides continuity of the thickness of the composite end wall panel to protect the outside surface from damage caused by the articles contained within the carton.

In certain embodiments, the expansion panel includes a single slidable section having a fixed section on each side. The slidable section is made slidable by a means for cooperatively relieving stress along the composite hinge. The means for cooperative relief includes an expansion cut or other severance means by which the slidable section is partially detached and defined with respect to each respective fixed section. Each expansion cut extends away from the hinged connection between the expansion panel and the inner top panel and turns toward a side edge of the expansion panel, defining an expansion hinge between the severance line and the end edge of the expansion panel. The expansion hinge allows and controls the transition from the neutral position to the stress relieving position. In still other embodiments, a two-ply structure is provided at those sections adjacent to the metal crown caps, or similar sharp elements, to reduce damage to the carton or articles.

In certain other embodiments, the expansion panel includes a single fixed section having a slidable section on each side. The fixed section is similarly partially detached and defined with respect to each slidable section by means for cooperative relief, preferably including respective expansion cuts, each of which extends away from the hinged connection between the expansion panel and the inner top panel and turns toward the center of the expansion panel, defining an expansion hinge between the severance line and the end edge of the expansion panel. In still other embodiments, the expansion panel includes a single fixed section and a single slidable section. The fixed section is defined with respect to the slidable section by an expansion cut or other severance means which extends away from the hinged connection between the expansion panel and the inner top panel and turns toward the center of the expansion panel, defining an expansion hinge between the expansion cut and the end edge of the expansion panel. In still other embodiments, the expansion panel includes one or more fixed sections and one or more slidable sections wherein the slidable sections are not hingedly attached to the fixed sections but to the respective adjacent top, bottom, or side panel.

According to another aspect, means are provided for relieving stress at the hinged connection between the composite end wall panel and the composite top wall. In certain embodiments, the stress relieving means include relief apertures disposed at or near the hinged connection between the composite end wall panel and the composite top wall. The location and extent of the stress relieving means is tailored to remove or liberate sheet material disposed at or near the hinged connection.

In certain embodiments, at least one relief aperture is disposed across at least a portion of the hinged connection, and is formed by creating an aperture that removes a portion of the expansion panel and of the inner top panel. The stress relieving means reduces bunching caused by congestion of sheet material at the fold, encouraging a cleanly creased fold that has less of a tendency to resist remaining in a folded condition.

It is contemplated that a carton incorporating the various aspects of the invention may include more than one composite wall. For example to strengthen the bottom wall of the carton, as well as the top, the blank may be formed from two pieces of sheet material. The first piece of sheet material includes the outer top panel, the first side wall, and an inner bottom panel having an expansion panel as described above. The second piece of sheet material includes the earlier described bottom panel, the second side panel, and the inner top panel having an expansion panel as described above. To begin erecting this exemplary carton, the outside surfaces of the inner bottom panel and the expansion panel are secured to the inside surfaces of the earlier described bottom panel and the lower end flap, respectively. In this fashion, a composite bottom wall and a composite lower end wall panel is created. Then, the carton is erected as described above with respect to the carton of the previous embodiments.

The foregoing has broadly outlined some of the aspects and features of the present invention, which should be construed to be merely illustrative of various potential applications of the invention. Other beneficial results can be obtained by combining portions of the disclosed information and the disclosed embodiments, such as by altering the orientation of the respective composite and single ply walls. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings, in addition to the scope of the invention defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plan view of one embodiment of a blank for forming a carton, according to the present invention.

FIG. 2 is a perspective view of a partially erected carton formed from the blank of FIG. 1 in a tubular condition, according to the present invention.

FIG. 3 is a partial interior perspective view of a fully constructed expansion panel assembly, according to the present invention.

FIG. 4 is a partial interior perspective view of a fully folded expansion panel assembly, according to the present invention.

FIG. 5 is a partial interior perspective view of an alternative embodiment of a fully constructed expansion panel assembly, according to the present invention.

FIG. 6 is a partial interior perspective view of an alternative embodiment of a fully constructed expansion panel assembly, according to the present invention.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosed herein. It must be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms, and combinations thereof. As used herein, the word “exemplary” is used expansively to refer to embodiments that serve as illustrations, specimens, models, or patterns. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. In other instances, well-known components, systems, materials, or methods have not been described in detail in order to avoid obscuring the present invention. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.

Referring now to the drawings in which like numerals indicate like elements throughout the several views, the drawings illustrate exemplary embodiments of an expansion panel assembly 200, best shown in FIG. 3, for use with a tubular carton C, best shown in FIG. 2. In the embodiments illustrated and described herein, the tubular carton C dispenses articles such as, but not limited to, beverage bottles. Generally described, the tubular carton C is formed from a foldable sheet material such as paperboard, corrugated board, plastic, or the like, and composites thereof.

With regard to the exemplary embodiment shown in FIG. 1, the tubular carton C is formed from a paperboard blank 100. The illustrated blank 100 includes five primary panels for forming the carton C. The panels of the blank 100 include an outer top panel 102, a first side panel 104, a bottom panel 106, a second side panel 108, and an inner top panel 110. The panels 102, 104, 106, 108, and 110 of the blank 100 are hingedly connected to one another. The outer top panel 102 is hingedly connected to the first side panel 104 by fold line 112. The first side panel 104 is hingedly connected to the bottom panel 106 by fold line 114. The bottom panel 106 is hingedly connected to the second side panel 108 by fold line 116. The second side panel 108 is hingedly connected to the inner top panel 110 by fold line 118. In the illustrated embodiment, a unitary blank 100 is used to form a single carton C, although in alternative embodiments two or more blanks may be employed to provide a carton C with the illustrated expansion panel assembly 200.

Each of the panels 102, 104, 106, 108, and 110 includes opposing end flaps defined in part by transverse fold lines disposed along opposite transverse edges of the blank 100. When the carton C is erected, the end flaps cooperate to form an end closure structure that includes an expansion panel assembly 200. In the embodiments illustrated, each end closure structure is sufficiently identical that like references have been used, with “a” or “b” affixed to distinguish the components of one end of the carton C from the other. Accordingly, the teaching will continue with reference only to those sections of the illustrated embodiments with the designation “a”. The outer top panel 102 is hingedly connected to end flap 120a along fold line 122a. First side panel 104 is hingedly connected to end flap 124a along fold line 126a. Bottom panel 106 is hingedly connected to end flap 128a along fold line 130a. Second side panel 108 is hingedly connected to end flap 132a along fold line 134a. Inner top panel 110 is hingedly connected to expansion flap 136a along fold line 138a.

The expansion panel 136a further comprises several elements. Relief apertures 140a each span a portion of inner top panel 110 and expansion panel 136a. Expansion cuts 144a define expansion hinges 146a, as well as expansion flap fixed sections 150a and expansion panel slidable section 152a. Expansion flap fixed and slidable sections are best described with regard to FIGS. 2 and 3.

With continued reference to FIG. 1, the blank 100 includes frangible severance line segments 160, 162, and 164, which, when the carton C is erected, form frangible severance lines 170, best shown in FIG. 2. It is contemplated that a frangible severance line includes, but is not limited to, perforations, a line of perforations, a line of short slits, a line of half cuts, a single half cut, any combination of slits, score lines, and half cuts, or the equivalent. In the embodiment illustrated, the severance lines 170 cooperate to provide removable sections T, which provide access to the articles, as understood by those skilled in the art.

The illustrated blank 100 further comprises a suitable known handle, formed from handle apertures 172, that allows the user to carry the carton C. The illustrated handle is often referred to as a race track handle. In a carton C with a race track handle, one carton C wall is provided with a first hand aperture at a position spaced from a second hand aperture such that the first and second apertures define a handle strip therebetween. To distribute stress away from the handle strip area, reinforcing fold lines 174 may be used according to the invention. Such fold lines may be provided to extend from each aperture 172 toward an adjacent corner of the wall formed by the top panel 102 of the carton C. A set of fold lines may emerge from each aperture 172 and diverge from each other as they approach the adjacent corner. Alternatively, a greater or lesser number of fold lines may emerge from each aperture 172.

With regard to the assembling and erecting of the illustrated blank 100 to form a carton C having an expansion panel assembly 200, reference will be made herein to the inside or inner surface and the outside or outside surface of the various panels. The inside or inner surface is that which is visible in the various figures while the outside or outer surface not visible in the various figures. Stated another way, upon forming a tubular carton C from the blank 100, the inside or inner surface of each panel typically face inwardly while the outside or outer surface of each panel are those sides typically face outwardly.

With reference now to FIG. 2, the carton C is arranged in a tubular condition as the outer surface of inner top panel 110 is matingly secured to the inner surface of outer top panel 102 to form the composite top wall 102/110 of an open ended tubular carton C. In the tubular condition, the composite top wall 102/110 is coplanar with the respective upper end wall flap 120a and expansion panel 136a. Stated differently, the end wall flap 120a and expansion flap 136a are shown prior to folding. In the illustrated embodiments, the panels, flaps, and their respective elements are aligned or placed immediately adjacent to each other such that they matingly cooperate. In other embodiments, corresponding elements do not have to be perfectly aligned as being merely proximate permits an enabling embodiment. In still other embodiments, elements of the inner flap may not be secured to the outer flap, or visa-versa. The panel and flap connection may be made by use of chemical or mechanical adhesives or other means for securing including locking tabs, as understood by those skilled in the art.

The inner top panel 110 is aligned with the outer top panel 102 such that the respective handle apertures 172 matingly cooperate, and such that the respective severance line segments 160 and 162 matingly cooperate. Further, expansion flap 136a is aligned and secured, in the manner described below with regard to the various embodiments, to upper end wall panel 120a, such that fold line 138a is aligned with fold lines 122a. In addition, each relief aperture 140a is disposed astride fold line 122a. Further, it should be clear that what is described herein with regard to the expansion panel assembly 200a located at one end of the carton C applies equally to the expansion panel assembly 200b located at the other end of the carton C, in those embodiments wherein the carton C has expansion flap assemblies at both ends.

As explained herein, one advantage of the present invention is to provide a carton C of increased strength and carrying capacity. One embodiment of a carton C of increased strength and carrying capacity comprises a two-ply top or bottom wall assembly and a two-ply end wall assembly. While a standard two-ply end wall assembly provides advantages, including increased strength and damage protection, the folding of such assemblies and the erecting of cartons C with such assemblies present certain challenges. These challenges include increased resistance to the folding of the end wall panels and the subsequent buckling of adjacent panels; however these challenges are overcome with the embodiments taught and claimed herein.

With regard to the two-ply end wall embodiments illustrated in FIGS. 2-4 inclusive, expansion flap 136a is secured to end wall flap 120a with adhesives or glues as well known to those skilled in the art. However, other means for securing may be used. As stated above, expansion flap 136a comprises at least one fixed section 150a and at least one slidable section 152a. Fixed panel section(s) 150a are secured to end wall flap 120a in face-contacting relationship while slidable section 152a is not.

After the articles to be placed into the carton C are grouped and loaded through either or both of the open ends of the carton C, the open ends are to be closed and sealed. With reference to FIG. 3, a partial sectional view of the interior of an expansion panel assembly 200a is shown before that assembly is folded to form a closed end wall structure. A folding sequence to close the open ends of carton C includes folding the end flaps 124a, 132a inwardly and positioning the end flaps 124a, 132a so that the outside of these flaps may be connected to the inside of the expansion flap 136a. In order to more clearly teach the movement of the expansion panel assembly 200, the end flaps 124a, 132a are shown to be torn away or are otherwise partially shown when in the fully folded position of FIG. 4. In other embodiments, the inside of end flaps 124a, 132a may be connected to the outside of the end wall flap 120a.

As understood by those skilled in the art, folding or otherwise bending a panel or flap causes the fibers of one surface to be put in compression while the fibers of the opposite surface are put in tension. For example, and with a momentary reference to FIG. 1, folding end wall flap 120a inwardly along fold line 122a so that the inside of that flap faces the inside of top panel 102, the fibers along the inside surface are in compression while the fibers along the outside surface are in tension. The effect of these compression and tension stresses is typically visible, particularly along the bend or fold line, in that the outside surface may appear stretched while the inside surface may appear bunched.

As further understood by those skilled in the art, when two panels are secured along their surfaces and then folded as a unit, the stresses along the joined surfaces act to create a shear force along the laminate. More specifically, in folding a two-ply panel that is not perfectly laminated, the upper surface of the lower panel is put into tension while the lower surface of the upper panel is put into compression. Folding an increased number of layers of material increases the shear stresses in the material and affects the performance characteristics of the material. For example, the increased thickness of a two-ply panel increases the folding resistance of the panel and, in folding such a panel, the shear stresses that are created may cause buckling.

To significantly reduce or eliminate the shear stresses and undesired performance characteristics introduced by folding a two-ply panel, a means for relief is provided in the expansion panel 136a. Means for cooperative relief includes a relief aperture 140a, or an expansion cut 144a, or an expansion hinge 146a. The configurations of the aperture 140a, expansion cut 144a, or the expansion hinge 146a, separately or together, are not limited to the illustrated cuts and hinges but may be of any shape desired that allows the slidable section 152a to move with respect to the fixed section 150a. Additional means for cooperative relief are described below.

Returning to FIG. 3, inwardly folding end wall panel 120a together with the connected expansion panel 136a will create the shear stress and related undesired performance characteristics described above. With regard to the means for relief provided in the expansion panel, the undesired performance characteristics and shear stresses are greatly reduced, if not eliminated, along the sections of fold line 122a where the relief apertures 140a are positioned. The relief apertures 140a are provided to prevent the overcrowding of material and may be of any shape. In some embodiments, the relief apertures are configured to absorb stresses by changing shape when folded.

The shear and compressive stresses that would otherwise remain along fold line 122a in a two-ply panel are reduced through the means for cooperative relief. As shown by the arrows labeled F that represent the shifting forces as well as the direction of movement for the slidable section 152a, the slidable section 152a is moved downwardly, about hinges 146a, from a first position P1 (best shown in FIG. 3) to a second position P2 (shown in FIGS. 3 and 4). The displacement of the slidable section 152a may be represented by the extent to which the hinges 146a have opened as well as by the extent to which the slidable portion edge 180 has shifted with regard to the adjacent fixed section edge 181.

Referring to FIG. 4, when the expansion panel assembly 200a has been folded as far as the carton C design requires and the slidable section has reached the second position P2, the assembly 200a may be attached to the end flaps 124a, 132a. Attaching the folded assembly to the end flaps may fix the slidable section at the second position P2. FIG. 4 illustrates a portion of the interior of an end wall structure of the carton C including the expansion flap assembly 200a, which is folded and attached to end flaps 124a, 132a. To facilitate clarity in teaching, FIG. 4 does not show the entirety the end flaps 124a, 132a shown in the blank 100, nor does it show the end wall flap 128a. Nevertheless, with regard to methods of folding and closing of an end wall structure, and as well understood by those skilled in the art, one method includes inwardly folding the end flaps 124a, 132a, inwardly folding and connecting expansion flap assembly 200a to the end flaps, and inwardly folding the bottom end flap 128a to the top end flap 120a, preferably in an overlapping arrangement. Other methods include alternating the sequence of folding and connecting the various flaps, as desired.

Expansion panel assemblies of various and alternative embodiments are considered, taught, and claimed herein. Two illustrated alternative embodiments are shown in FIGS. 5 and 6. To significantly reduce or eliminate the shear stress and undesired performance characteristics introduced by folding a two-ply panel, expansion panel assembly 300 includes a fixed section 350a and slidable sections 352a. The expansion panel assembly 300 further includes at least one means for cooperative relief. Means for cooperative relief includes one or more relief apertures 340a, one or more expansion cuts 344a, and one or more expansion hinges 346a.

Similar to the expansion panel assembly 200a shown in FIG. 3, the expansion flap assembly 300 shown in FIG. 5 is in the pre-folded first position P1. As the expansion flap assembly 300 is folded, the stresses that would otherwise remain along fold line 320—the area of concentration—are reduced or shifted through the means for cooperative relief. The arrows labeled F represent the direction of shifting forces on the slidable sections 352a wherein the shifting forces are applied as the expansion panel assembly 300 is folded along fold lines 322a, 338a. As the shifting forces are applied, the slidable sections 352a are moved downwardly about hinges 312 from a first position P1 to a second position P2 (not shown). The second position P2 resembles that shown in FIG. 3.

The extent to which the slidable sections 352a are displaced may be represented by the extent to which the hinges 346a have opened, or by the extent to which slidable portion edges 380 have shifted in relation to the adjacent fixed section edge 381. When the expansion flap assembly 300 has been folded as far as the carton C design requires and the slidable section has reached the second position P2, the assembly 300 may be attached to the end flaps (not shown) or otherwise folded and closed as described herein.

With reference now to FIG. 6, an expansion panel assembly 400 includes a fixed section 450a and slidable sections 452a. The expansion panel assembly 400 further includes at least one means for cooperative relief. Means for cooperative relief includes one or more relief apertures 340a and one or more expansion cuts 344a. In this embodiment, the expansion cuts 344a extend to the edge of the expansion panel 436a.

The slidable sections 452a are moved downwardly from a first position P1 to a second position P2 (not shown) as the expansion panel assembly 400 is folded along fold lines 422a, 438a. The extent to which the slidable sections 452a are displaced may be represented by the extend to which the sidable portion edges 480 are displaced or shifted in relation to the fixed section edge 481.

In certain embodiments, the end flap 120a may include the means for cooperative relief described with regard to end flap 136a. Additionally, as understood by those skilled in the art, the hinge 146a may be positioned proximate the fold line 122a.

The present invention has been illustrated in relation to particular embodiments which are intended in all respects to be illustrative rather than restrictive. Those skilled in the art will recognize that the present invention is capable of many modifications and variations without departing from the scope of the claims. For example, as used herein, directional references such as “top”, “base”, “bottom”, “end”, “side”, “inner”, “outer”, “upper”, “middle”, “lower”, “front” and “rear” do not limit the respective walls of the carton to such orientation, but merely serve to distinguish these walls, flaps, and panels from one another. Any reference to a hinged connection should not be construed as necessarily referring to a junction including a single hinge only; indeed, it is envisaged that hinged connection can be formed from one or more potentially disparate means for hingedly connecting materials.

The the above-described embodiments are merely exemplary illustrations of implementations set forth for a clear understanding of the principles of the invention. Variations, modifications, and combinations may be made to the above-described embodiments without departing from the scope of the claims. All such variations, modifications, and combinations are included herein by the scope of this disclosure and the following claims.