EP2085314A2

EP2085314A2 - Method and apparatus for constructing a carton

Info

Publication number: EP2085314A2
Application number: EP09151823A
Authority: EP
Inventors: Denis Boscart; Pascal Martini; Alain Vergnaud
Original assignee: Meadwestvaco Packaging Systems LLC
Current assignee: WestRock Packaging Systems LLC
Priority date: 2008-02-01
Filing date: 2009-01-30
Publication date: 2009-08-05
Also published as: EP2085314A3; GB0801890D0

Abstract

A method of constructing a carton (8) from a carton blank (10) and apparatus for performing said method, the method comprising providing a carton blank, having a main panel (16) comprising a plurality of article-receiving apertures (22a, 22b, 22c, 22d, 22e, 22f), in a flat form to group of articles (A) such that each of said plurality of apertures is in registry with a respective article in said group of articles, folding said main panel such that it becomes substantially V-shaped bringing a lowermost portion of said V-shaped main panel into engagement with the article such that innermost portions of the plurality of apertures engage with a protruding portion of a respective article wherein said engagement maintains the grouped configuration of the articles during further processing of the carton blank.

Description

Field of Invention

The present invention provides a method for constructing a carton from a carton blank, which carton is for receiving a plurality of articles, and an apparatus for the same, more particularly, but not exclusively the carton provides a top gripping carrier for said plurality of articles.

Background Art

Cartons for engaging multiple articles are useful for enabling consumers to obtain and transport a desired quantity of individual articles such as soft drinks or other beverages or food stuffs.
It is well known to provide top gripping article carriers in which an aperture is formed in a panel of the carrier; wherein a plurality of tabs are struck from said aperture around the periphery of the aperture. The tabs being displaced out of the plane of said panel when an article is received in the aperture and wherein said tabs surround the article and engage a flange or lip of the article.
Such a carrier is disclosed in US 2,936,070 to Poupitch and in US 5,188,225 to Jorba . It can be difficult to remove the articles from such carriers without damaging the carton.
It is desirable to provide an article carrier which can be reused such that empty articles can be replaced in the carrier to facilitate transportation of the empty articles, for example to a recycling station or for return to the distributor.
It is also desirable for ecological and economic reasons to minimise the quantity of material required whilst at the same time providing a secure carrier for the articles.
It is also desirable to construct the carton in a straight line packaging machine, wherein the carton is constructed efficiently in order to maximise the production rate.

Summary of Invention

A first aspect of the invention provides a method of constructing a carton from a carton blank comprising providing a carton blank, having a main panel comprising a plurality of article-receiving apertures, in a flat form to a group of articles such that each of said plurality of apertures is in registry with a respective article in said group of articles, folding said main panel such that it becomes substantially V-shaped bringing a lowermost portion of said V-shaped main panel into engagement with the article such that innermost portions of the plurality of apertures engage with a protruding portion of a respective article wherein said engagement maintains the grouped configuration of the articles during further processing of the carton blank.
Preferably, the method comprises providing a pattern shaped to complement at least an upper portion of the group of articles which is brought into contact with the main panel such that the main panel engages opposing sides of each article of the article group.
Preferably, the method comprises moving a guide transversely relative to the group of articles such that an outermost portion of each aperture, opposing said innermost portion, is brought into engagement with each article in the group.
Preferably, the method comprises providing folding side and end panels of the carton blank about the group of articles and maintaining said end panels in alignment by exerting an upward force on the end panels.
Preferably, the method comprises applying said upward force to a panel interconnecting the side and end panels.
Preferably, the method comprises providing folding each of the side panels about a respective fold line defined therein to facilitate application of adhesive to the side and/or end panel.
A second aspect of the invention provides an apparatus for constructing a carton from a carton blank comprising a conveyor for providing a carton blank, having a main panel comprising a plurality of article-receiving apertures, in a flat form to a group of articles such that each of said plurality of apertures is in registry with a respective article in said group of articles, a guide for folding said main panel such that it becomes substantially V-shaped and a means for bringing a lowermost portion of said V-shaped main panel into engagement with the article such that innermost portions of the plurality of apertures engage with a protruding portion of a respective article wherein said engagement maintains the grouped configuration of the articles during further processing of the carton blank.
Preferably, said apparatus comprises a pattern shaped to complement at least an upper portion of the group of articles which is coupled to an overhead conveyor such that the pattern contacts the main panel whereby the main panel engages opposing sides of each article of the article group.
Preferably, said apparatus comprises a mobile guide which mobile guide is moveable in a transverse direction relative to the group of articles such that an outermost portion of each aperture, opposing said innermost portion, is brought into engagement with each article in the group.
Preferably, said apparatus comprises a means for folding side and end panels of the carton blank about the group of articles and an alignment guide for maintaining each of said end panels in alignment by exerting an upward force on the respective end panel.
Preferably, said alignment guide engages a panel interconnecting the side and end panels.
Preferably, said apparatus comprises a folding guide for folding each of the side panels about a respective fold line defined therein to facilitate application of adhesive to the side and/or end panel.
A third aspect of the present invention provides a carton of the top gripping type for receiving and retaining a group of cylindrical articles said carton comprising a main panel having an aperture for receiving and retaining an upper portion of a cylindrical article wherein said aperture defines an engaging edge of said main panel which engages with a curved portion of a cylindrical article, said aperture comprising at least one U-shaped section, said U-shaped section being struck from or defined by a first portion of said main panel, said first portion of said main panel being foldable such that an edge of said U-shaped section is engagable with an article received in the aperture, the carton comprising an end retention structure for retaining end most articles in a group of articles within the carton, a side panel hinged to said first portion by a first hinge line wherein the side panel comprises a second hinge line parallel to said first hinge line such that the side panel may be folded about the second hinge line to facilitate securing the side panel to the end retention structure.
A fourth aspect of the present invention provides a blank for forming a carton of the top gripping type for receiving and retaining a group of cylindrical articles said blank comprising a main panel having an aperture for receiving and retaining an upper portion of a cylindrical article wherein said aperture defines an engaging edge of said main panel which is engagable with a curved portion of a cylindrical article, said aperture comprising at least one U-shaped section, said U-shaped section being struck from or defined by a first portion of said main panel, said first portion of said main panel being foldable such that an edge of said U-shaped section is engagable with an article received in the aperture, the blank comprising an end retention structure for retaining end most articles in a group of articles within a setup carton, a side panel hinged to said first portion by a first hinge line wherein the side panel comprises a second hinge line parallel to said first hinge line such that the side panel is foldable about the second hinge line to facilitate securing the side panel to the end retention structure.

Brief Description of Drawings

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 illustrates a plan view of a blank for forming a carton according to a first embodiment of the present invention;
FIGURE 2 illustrates a perspective view of a carton blank being brought into registry with a group of articles;
FIGURE 3 illustrates a perspective view of a first stage of the folding process for assembling the carton;
FIGURE 4 illustrates an enlarged perspective view of a central region of the carton;
FIGURE 5 illustrates a perspective view of a second stage of the folding process for assembling the carton;
FIGURE 6 illustrates an enlarged perspective view of the second stage of the folding process for assembling the carton;
FIGURE 7 illustrates a perspective view of the base of an assembly tool for use in a third stage of the assembly process shown in Figure 8;
FIGURE 8 illustrates a perspective view of a third stage in the folding process for assembling the carton;
FIGURE 9 illustrates a perspective view of a fourth stage in the folding process for assembling the carton;
FIGURE 10 illustrates a perspective view of the carton after completing the fourth stage in the folding process shown in FIGURE 9;
FIGURE 11 illustrates a perspective view of a fifth stage in the folding process for assembling the carton;
FIGURE 12 illustrates a perspective view of a sixth stage in the folding process for assembling the carton;
FIGURE 13 illustrates a perspective view of a seventh stage in the folding process for assembling the carton;
FIGURE 14 illustrates a perspective view of an assembled carton according to a first embodiment of the present invention; and
FIGURE 15 illustrates a perspective view of a carton according to an alternative embodiment of the present invention.

Detailed Description of Exemplary Embodiments of the Present Invention

Referring to the drawings there is shown in Figure 1, a blank 10 for forming the carton 8 shown in Figure 14. Blank 10 comprises a top panel 16 which comprises apertures 22a, 22b, 22c, 22d, 22e, 22f each for receiving an article A, as illustrated in Figures 2.
Each of the apertures 22a, 22b, 22c, 22d, 22e and 22f are substantially the same; they will be described by reference to only aperture 22a.
Aperture 22a comprises first and second opposing arcuate portions 80, 82 and a linear portion 84. In the preferred embodiment the linear portion 84 is disposed along an outer edge of the top panel 16. Optionally, aperture 22a also comprises a plurality of tabs 40. Tabs 40 are defined in part by a weakened line 41. In the preferred embodiment weakened line 41 is a cutline. The weakened line 41 facilitates folding of the tabs 40 out of the plane of the top panel 16. In the preferred embodiment there are three tabs 40 positioned so as to fold in an arc, which are is disposed opposite the linear portion 84. The tabs 40 are located on a section of the aperture 22a which is adjacent a notional line bisecting the top panel 16 in a longitudinal direction. In this way the tabs 40 are structured and arranged so as to facilitate displacement of the top panel 16 such that the top panel is placed in a state of tension when articles are received in the apertures 22a, 22b, 22c, 22d, 22e, 22f.
Top panel 16 comprises a pair of fold lines 11, 13, which hingedly connect the top panel 16 to side panels 12 and 14 respectively.
Fold lines 15a and 15b, together with fold lines 11 and 13 respectively, define, at least in part, outer shoulder portions 24a, 24b which in a setup carton 8 are folded about a shoulder portion of an article A received in one of the apertures 22a, 22b, 22c, 22d, 22e, 22f, as shown in Figures 2 to 4.
The outer shoulder portions 24a, 24b comprise fold lines 45 which in combination with fold line 11 and linear portion 84 define a trapezoidal portion 42. Fold line 11 and 13 each comprise cut lines 51 which are arranged in pairs. Each pair of cut lines 51 is disposed along a portion of fold line 11 or 13 which forms a part of a trapezoidal portion 42.
The trapezoidal portions 42 facilitate tightening of the carton 8 about the articles C.
Blank 10 further comprises finger apertures 60 disposed along a notional line bisecting the top panel 16 in a longitudinal direction. Finger apertures 60 are disposed between four adjacent apertures 22a, 22b, 22e, 22d and 22b, 22c, 22e, 22f respectively. The finger apertures 60 comprise a pair of tabs 62a, 62b which are hinged to top panel 16 along fold lines 63a, 63b respectively. Tabs 62a, 62b are separated by a cutline 61. Tabs 62a, 62b are optionally provided for cushioning a user's finger when the finger aperture 60 is deployed for carrying the carton 8.
Blank 10 also comprises additional fold line 45 and 47 disposed in each corner of the top panel 16. Additional fold line 45 and fold line 15a/15b define in part a first tab 46 whereas additional fold line 47 and fold line 15a/15b define in part a second tab 44. These first and second tabs 44, 46 can be folded so as to provide relief in the corner of the main panel. In an alternative embodiment this reduction in the rigidity in the corner of the main panel 16 allows the carton 8 to be wrapped in a tertiary material such as shrink wrap or other known material.
Blank 10 comprises a pair of end retention structures 90a, 90b hinged to each of the side panels 12, 14.
The end retention structures 90a, 90b comprise an end panel 18, 20 at each end of which a corner panel 28a, 28b; 30a, 30b is hingedly connected thereto along a fold line 21a, 21b; 23a, 23b respectively. Each corner panel 28a, 28b; 30a, 30b is also hinged to a respective first gusset panel 32a, 32b; 34a, 34b.
Each first gusset panels 32a, 32b; 34a, 34b is hingedly connected to a second gusset panel 36a, 26b; 38a, 38b respectively. Second gusset panels 38a, 36a are hingedly connected to opposing ends of side panel 12 whereas second gusset panels 36b, 38b are hingedly connected to opposing ends of side panel 14.
Optionally, blank 10 may include fold lines 3a and 3b in panels 12 and 14 respectively. Side panels 12 and 14 can therefore be folded about the fold line 3a, 3b respectively to facilitate the application of adhesive to either the inner surface of side panel 12, 14 or the outer surface of first gusset panels 32a, 32b; 34a, 34b.
Turning now to Figures 2, there is shown a first step in the assembly process, a carton blank 10 is supplied to a group of articles A in a flat form, such that the apertures 22a, 22b, 22c, 22d, 22e, 22f are brought into registry with a respective one of the articles A in the group. In the preferred embodiment the group of articles consist of six substantially cylindrical articles, such as beverage cans, arranged in two rows of three articles. Although it is envisaged that groups of articles A may have alternate configurations. The carton blank 10 is assembled in a packaging machine (not shown in the Figures), in a preferred embodiment it is envisaged that the packaging machine will be a straight line packaging machine, although other configurations could be used in alternative embodiments. In the preferred embodiment the carton blank 10 is supplied to the group of articles A by a rotary infeed device (not shown) comprising vacuum cups (not shown), the carton blanks 10 are stored in a carton hopper (not shown) disposed above a conveyor (not shown) which conveys the articles through the packaging machine.
Figures 3 shows a first stage in the folding process in construction of the carton 8, carton blank 10 has been folded about a notional longitudinal line which bisects the carton blank 10. Carton blank 10 is folded into a substantially V-shaped configuration. This is achieved by guide rail 100 being brought in to contact with an upper surface of carton blank 10. Guide rail 100 forms part of the packaging machine. In one embodiment this is achieved using a dynamic or moving guide rail 100 which is brought into contact with carton blank 10 by lowering it in the direction indicated by direction arrow D1, it is envisaged that this dynamic guide rail 100 would be coupled to an overhead conveyor (not shown). In an alternative embodiment the folding process could be achieved using a fixed guide rail and conveying the carton blank 10 in a forward direction simultaneously with the group of articles A.
Figure 4 is an enlarged view of the central portion of the carton blank 10 illustrating assembly of the tabs 40 about the article A. As a consequence of the action of guide rail 100 the tabs 40 have been folded out of the plane of the top panel 16 of carton blank 10. Each of the tabs 40 engages a protruding portion or flange of the article A. Returning again to Figure 3 it can be seen that the outer edge portions of the apertures 22a, 22b, 22c, 22d, 22e, 22f disposed adjacent side panels 12 and 14 have not been engaged around the articles A. The central portion of the carton blank 10 is therefore clipped to the group of articles A. This serves to keep the group of articles A together during the proceeding assembly process. The group of articles A and the carton blank 10 are conveyed together through the packaging machine.
Figure 5 illustrates a second stage in the assembly process; the packaging machine comprises mobile guide rails 112a, 112b which facilitate folding of side panels 12, 14 into a substantially vertical orientation. It can be seen that the guide rail 100 optionally comprises a plurality transverse lug elements 110. The series of transverse lug elements 110 form a comb like structure having teeth which are spaced apart so as to be in registry with those portions of top panel 16 on both sides of each aperture 22a, 22b, 22c, 22d, 22e, 22f so as to encourage said portions of top panel 16 to engage each of the respective articles A. This is achieved by movement of the guide rail 100 in the direction of direction arrows D2.
Figure 6 shows an enlarged view of the guide rail 100 and transverse lug elements 110 engaging top panel 16. It can be seen that the central portion of the top panel 16 is engaged with the articles A.
Figure 7 illustrates a view of the base of a pair of patterns 114a, 114b which are used to form the top panel 16 about the group of articles A. The patterns 114a, 114b comprise recesses 116 in their base each of which is shaped to complement the form of an upper portion of a respective article A.
Figure 8 illustrates the patterns 114a, 114b being brought down in the direction indicated by direction arrow D9. The patterns 114a, 114b are located on either side of guide rail 100 between guide rail 100 and a respective one of mobile guides 112a, 112b. In this way the top panel 16 engages the side of each respective article beneath the protruding portion of the flange.
Turning now to Figure 9 there is shown a further stage in the assembly process, mobile guides 112a, 112b move outwardly in direction D5 and D6 respectively thereby forcing the remaining portion of the top panel 16 to engage the free edge of the each of the articles A. Each mobile guide is also moved downwardly as indicated by direction arrow D4. A fixed guide 118a, 118b disposed on either side of the group of articles A engage an inner surface of a respective side panel 12, 14 from underneath as indicated by direction arrow D3, thus preventing side panels 12, 14 from being folded downwardly. Fixed guides 118a, 118b also facilitate the clipping of the outer edges of top panel 16 about the articles A, by providing a platform against which the side panels can rest. It is envisaged that the mobile guide could be replaced with a static guide which is shaped such that as a carton and respective articles are conveyed past or along the static guide the static guide effectively moves in a direction transverse to the direction of travel of the carton and articles, in this way the static guides would spaced further apart downstream.
Turning now to Figure 10 the product of the folding process described above and shown in Figures 2 to 9 is illustrated; it can be seen that the end retention structures 90a, 90b as shown in Figure 1 which comprise end panel 18, 20 are curved downwardly such that they are substantially U-shaped. In order to invert the end panels 18, 20 side panels 12, 14 are folded downwardly in the direction indicated by direction arrow D6, as this is done outer shoulder portions 24a, 24b are folded about the shoulder portion or chine of the articles A as illustrated in Figure 11. This folding process could be achieved with fixed or dynamic guides (not shown).
Figure 12 illustrates the end panels 18, 20 being folded about the ends of the group of articles A. This is achieved using a wheel or lug chain device known in the art. In order to ensure accurate positioning of the side panel 12, 14 positioning guides 120a ,120b are brought into contact with first gusset panels 32a, 32b; 34a, 34b respectively; such that the positioning guides 120a, 120b are disposed between first gusset panels 32a, 32b; 34a, 34b and a respective side panel 12, 14. The positioning guides are moved in the direction indicated by direction arrows D7, such that the gusset panels 36a, 36b, 38a, 38b to be folded inwardly and thereby cause end panels 18, 20 to be moved downwardly. Alternatively, the end panels 18, 20 may be folded downwardly by means for example of a wheel or lug chain device. The end panels 18, 20 may then be tightened about the group of articles A by using positioning guides 120a, 120b to engage with the gusset panels 36a, 36b, 38a, 38b.
Figure 13 illustrates a gluing process of the preferred embodiment of the present invention, in which side panels 12, 14 are folded about fold lines 3a, 3b such that glue may be applied by an inline gluing machine (not shown) to a lower portion of the first gusset panels 32a, 32b; 34a, 34b prior to folding the lower portion of panels 12, 14 into contact with first gusset panels 32a, 32b; 34a, 34b. The panels 12, 14 are then compressed against the first gusset panels 12, 14 to securely adhere the side panels 12, 14. This could be achieved using a static or dynamic guide, such as a wheel or belt.
In this way the carton blank 10 is formed into a carton 8 as shown in Figure 14, which carton 8 together with the group of articles A forms a package suitable for distribution.
In alternative embodiments the packaging machine may be used to assemble carton blanks having a central keel structure 226a, 226b such as that disclosed in co-pending application no. GB0715917.1 . Figure 15 illustrates a carton 208 having this structure, it can be seen that the carton 208 comprises inner shoulder panels 226a, 226b which are disposed between panels 235a, 235b forming the top panel.
The present invention provides an economical carton requiring a minimal quantity of material to provide a package for a plurality of articles, wherein a main panel comprises apertures for engaging articles and a strap portion for maintaining the bases of the articles in close proximity. Furthermore an efficient method and apparatus is provided for assembling cartons.
It will be recognised that as used herein, directional references such as "top", "base", "end", "side", "inner", "outer", "upper" and "lower" do not limit the respective panels to such orientation, but merely serve to distinguish these panels from one another. Any reference to a frangible line can also be construed as a cut line, score line, perforate line or slit, without departing from the scope of invention. Also, any reference to hinged connection or fold line should not be construed as necessarily referring to a single fold line only; indeed it is envisaged that hinged connection can be formed from one or more of the following, a line of demarcation or weakened line, a score line, a frangible line or a fold line without departing from the scope of invention.

Claims

A method of constructing a carton (8) from a carton blank (10) comprising providing a carton blank, having a main panel (16) comprising a plurality of article-receiving apertures (22a, 22b, 22c, 22d, 22e, 22f), in a flat form to a group of articles (A) such that each of said plurality of apertures is in registry with a respective article in said group of articles, folding said main panel such that it becomes substantially V-shaped, bringing a lowermost portion of said V-shaped main panel into engagement with the article such that innermost portions of the plurality of apertures engage with a protruding portion of a respective article wherein said engagement maintains the grouped configuration of the articles during further processing of the carton blank.
A method according to claim 1 comprising providing a pattern (114a, 114b) shaped to complement at least an upper portion of the group of articles bringing said pattern into contact with the main panel such that the main panel engages opposing sides of each article of the article group.
A method according to either of claims 1 or 2 comprises moving a guide (112a, 112b) transversely relative to the group of articles such that an outermost portion of each aperture, opposing said innermost portion, is brought into engagement with each article in the group.
A method according to claim 3 comprising folding side (12, 14) and end (18, 20) panels of the carton blank about the group of articles and maintaining said end panels in alignment by exerting an upward force on the end panels.
A method according to claim 4 comprising applying said upward force to a panel (32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b) interconnecting the side and end panels.
A method according to claim 4 or 5 comprising folding each of the side panels about a respective fold line (3a, 3b) defined therein to facilitate application of adhesive to the side and/or end panel.
An apparatus for constructing a carton (8) from a carton blank (10) comprising a conveyor for providing a carton blank, having a main panel (16) comprising a plurality of article-receiving apertures (22a, 22b, 22c, 22d, 22e, 22f), in a flat form to a group of articles (A) such that each of said plurality of apertures is in registry with a respective article in said group of articles, a guide (100) for folding said main panel such that it becomes substantially V-shaped means (100; 110) for bringing a lowermost portion of said V-shaped main panel into engagement with the article such that innermost portions of the plurality of apertures engage with a protruding portion of a respective article wherein said engagement maintains the grouped configuration of the articles during further processing of the carton blank.
An apparatus according to claim 7 comprising a pattern (114a, 114b) shaped to complement at least an upper portion of the group of articles which is coupled to an overhead conveyor such that the pattern contacts the main panel whereby the main panel engages opposing sides of each article of the article group.
An apparatus according to either of claims 7 or 8 comprising a guide (112a, 112b) which guide moves in a transverse direction relative to the group of articles such that an outermost portion of each aperture, opposing said innermost portion, is brought into engagement with each article in the group.
An apparatus according to claim 9 comprising a means (112a, 112b) for folding side (12, 14) and end (18, 20) panels of the carton blank about the group of articles and an alignment guide (120a, 120b) for maintaining each of said end panels in alignment by exerting an upward force on the respective end panel.
An apparatus according to claim 10, wherein said alignment guide engages a panel (32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b) interconnecting the side and end panels.
An apparatus according to claim 10 or 11 comprising a folding guide (112a, 112b, 118a, 118b) for folding each of the side panels about a respective fold line (3a, 3b) defined therein to facilitate application of adhesive to the side and/or end panel.
A carton (8) of the top gripping type for receiving and retaining a group of cylindrical articles (A) said carton comprising a main panel (16) having an aperture (22a, 22b, 22c, 22d, 22e, 22f) for receiving and retaining an upper portion of a cylindrical article wherein said aperture defines an engaging edge (80, 82, 84) of said main panel which engages with a curved portion of a cylindrical article, said aperture comprising at least one U-shaped section (84), said U-shaped section being struck from or defined by a first portion (42) of said main panel, said first portion of said main panel being foldable such that an edge of said U-shaped section is engagable with an article received in the aperture, the carton comprising an end retention structure (90a, 90b) for retaining end most articles in a group of articles within the carton, a side panel (12, 14) hinged to said first portion by a first hinge line (11, 13) wherein the side panel comprises a second hinge line (3a, 3b) parallel to said first hinge line such that the side panel may be folded about the second hinge line to facilitate securing the side panel to the end retention structure.
A blank (10) for forming a carton (8) of the top gripping type for receiving and retaining a group of cylindrical articles (A) said blank comprising a main panel (16) having an aperture (22a, 22b, 22c, 22d, 22e, 22f) for receiving and retaining an upper portion of a cylindrical article wherein said aperture defines an engaging edge (80, 82, 84) of said main panel which is engagable with a curved portion of a cylindrical article, said aperture comprising at least one U-shaped section (84), said U-shaped section being struck from or defined by a first portion (42) of said main panel, said first portion of said main panel being foldable such that an edge of said U-shaped section is engagable with an article received in the aperture, the blank comprising an end retention structure (90a, 90b) for retaining end most articles in a group of articles within a setup carton, a side panel (12, 14) hinged to said first portion by a first hinge line (11, 13) wherein the side panel comprises a second hinge line (3a, 3b) parallel to said first hinge line such that the side panel is foldable about the second hinge line to facilitate securing the side panel to the end retention structure.