PANEL INTERLOCKING MEANS

Abstract: Panel interlocking means (20) and a carton blank incorporating panel interlocking means for securing together a first and a second panel (10, 12) in overlapping relationship, said panel interlocking means (20) comprising a locking tab (22) struck from said first panel (10), and a retaining tab (42) defining a locking aperture (43) struck from said second panel (12), wherein the retaining tab (42) is displaced out of the plane of said second panel (12) to receive said locking tab (22) through the locking aperture (43) to be engaged therewith, wherein the second panel (10, 12) further comprises flexural means (52) to receive the locking tab (22) and to enable an edge of the locking aperture (43) to be displaced out of the plane of the second panel (12) thereby to enable the locking tab (22) to move readily through said locking aperture (43).

Description: PANEL INTERLOCKING MEANS Technical Field of the Invention This invention relates to panel interlocking means for cartons for securing together a pair of panels, for example, adjacent overlapping panels of a paperboard carton. In some situations, these panels are provided by the opposite ends of a wrapper blank which are brought together in overlapping relationship and interlocked. Background of the Invention Locking tabs which are struck from one end of the carton wrapper and which are arranged to be forced through corresponding apertures defined by retaining tabs, struck from an opposite end of a wrapper are well known. An example of such a lock is shown in Figure 1 and corresponds substantially to GB 1 598 367. A problem associated with locking tabs of this type is that when they are forced through the aperture, the shoulder portion 1, illustrated in Figure 1, is forcibly folded out of alignment with the remainder of the tab in order to pass through the aperture. This is undesirable as it weakens the locking tab. A further example is illustrated in GB 2 156 785 and owned by the applicant of this invention. This document illustrates a wraparound carton with panel interlocking means comprising a locking tab which is required to be driven through an aperture. It is apparent from the drawings that the outer portions of the tab are forcibly folded out of alignment with the remainder of the tab during the locking procedure. The locking tab is propped up by a retaining tab and the base portion of the locking tab is disposed in second engagement with the locking edge of a locking aperture. Unfortunately, known panel interlocking means when applied to lower caliper board can weaken the panel interlocking means further which may cause the male and female parts not to engage properly. The present invention seeks to provide an improved panel interlocking means which overcomes or at least mitigates the problems of the prior art. Summary of the Invention According to a first aspect of the invention, panel interlocking means for securing together a first and a second panel in overlapping relationship, the panel interlocking means comprising a locking tab struck from said first panel, and a retaining tab defining a locking aperture struck from the second panel. The retaining tab is displaced out of the plane of the second panel to receive the locking tab through the locking aperture to be engaged therewith. The second panel further comprises flexural means to receive the locking tab and to enable an edge of the locking aperture to be displaced out of the plane of the second panel thereby to enable the locking tab to move readily through said locking aperture. The term 'move readily' used in the present application means to move more easily with the flexural means present than if no flexural means is provided. Advantageously, the panel interlocking means of the first aspect of the invention may result in the locking tab not being deformed or torn during locking and which can be incorporated in low caliper board or recycled paper board (often referred to as grey board). Further the panel interlocking means can continue to be interengaged when the panel interlocking means is subjected to tensile or compressive forces. A second aspect of the invention provides a carton blank incorporating panel interlocking means having a first panel and a second panel, the panel interlocking means comprising a locking tab struck from the first panel, and a retaining tab defining a locking aperture struck from the second panel, wherein the retaining tab can be displaced out of the plane of the second panel to receive the locking tab through the locking aperture to be engaged therewith. The second panel further comprises flexural means that can receive a shoulder portion of the locking tab and enable an edge of the locking aperture to be displaced out of the plane of the second panel to cause the locking tab to move readily through the locking aperture. According to an optional feature of the first or second aspects of the invention the flexural means may be a tab struck from the second panel adjacent the locking aperture. Preferably, the flexural tab is positioned adjacent a side edge of the locking aperture. According to another optional feature of the first or second aspects of the invention the flexural means is provided by a portion of the second panel adjacent the locking aperture, which portion includes a cut line with opposite ends struck from the second panel, wherein one end intersects the side edge of the locking aperture, which cut line defines two parts of the second panel portion that is capable of flexing. According to another optional feature of the first or second aspects of the invention, the intersection between the cut line and the edge of the locking aperture may be substantially perpendicular. According to another optional feature of the second aspect of the invention, the cut line may be non-linear, and diverge from its perpendicular intersection with the edge of the locking aperture. According to a further optional feature of the first or second aspects of the invention, a second flexural means may be provided to receive the locking tab and to enable an opposed edge of the locking aperture to be moved out of alignment with the second panel thereby to enable the locking tab to move through the locking aperture. According to a further optional feature of the first or second aspects of the invention the intersection may be intermediate the ends of the side edge. According to another optional feature of the first or second aspects of the invention the locking tab may comprise a neck portion hinged at a base thereof to the first panel, and a shoulder portion contiguous therewith. According to a still further optional feature of the first or second aspects of the invention the locking tab may comprise at least one recessed portion. Preferably, the at least one recessed portion may be defined by a serrated edge of the locking tab. According to yet another optional feature of the first or second aspects of the invention the displaced edge of the locking aperture may define an acute angle with the edge connecting the retaining tab. Brief Description of the Drawings Exemplary embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 shows a locking means substantially corresponding to patent number GB 1 598 368; FIGURE 2 illustrates a wraparound carton blank incorporating panel interlocking means according to a first embodiment of the invention; FIGURE 3 shows a part of a pair of panels in close proximity, incorporating panel interlocking means according to one aspect of the invention; FIGURE 4 is a perspective view of the panel interlocking means illustrated in Figure 3 with the locking tab being inserted into the locking aperture; FIGURE 5 is a perspective view of the panel interlocking means illustrated in Figure 3 with the panels secured together; FIGURE 6 is a plan view of a second embodiment of the panel interlocking means illustrating the aperture. FIGURES 7a, b and c show three examples of panel interlocking means formed from a pair of panels which can be the opposite ends of a wraparound carton blank, in close proximity, according to third, fourth and fifth embodiments of the invention; FIGURE 8a is a perspective view of the underside part of the panels held in overlapping relationship by the panel interlocking means illustrated in Figure 7a; and FIGURE 8b is a perspective view from the opposite side of the overlapping panels illustrated in Figure 8a. Detailed Description of the Preferred Embodiments Referring to Figures 2 and 3 of the drawings, a pair of panels 10, 12 respectively are adapted to be interlocked and are formed from paperboard or similar foldable sheet material. The panels 10, 12 may, for example, be disposed at the opposite ends of one and the same wraparound carton blank which is to be formed into a carton sleeve including opposed side walls 14, 16 and a top panel 18, in which panels 10, 12 then provide bottom panels of the carton, as shown in Figure 2. The carton is used for packaging a plurality of articles, for example, yoghurt cartons, cans or bottles. Referring in particular to Figure 3, first and second panels 10, 12 include panel interlocking means 20 for securing together the panels in overlapping relationship. Panel interlocking means 20 comprises locking tab 22 struck from first panel 10 and is hingably connected thereto by fold line 24. The fold line 24 is preferably substantially parallel to and spaced from the end edge 26 of panel 10 and optionally, fold line 24 is separated by a cut line 25 to make folding the locking tab 22 easier. In this embodiment, the locking tab 22 comprises a neck portion 28 and a main portion 30, including a shoulder portion 32 contiguous therewith. A pair of oppositely disposed cut lines 34. 36 define the side edges of the neck portion 28. Main portion 30 extends beyond neck portion 28 towards free edge 26 and is separated from first panel 10 by a cut line 38 which connects cut lines 34 and 36 and to define the shape of the main portion which is preferably an "arrow head" shape. Neck portion 28 should be narrower in width than the adjacent part of shoulder portion 32 to define at least one locking edge 40 formed along the lower part of the shoulder portion. As shown in Figures 3, a retention tab 42 is struck from second panel 12 which extends into a locking aperture 43, spaced from end edge of panel 12. Preferably, retention tab 42 comprises an elongate portion 44 which is separated from panel 12 by a pair of oppositely disposed cut lines 46, 48 defining the side edges of the elongate portion 44. A cut line 50 defines a distal edge of elongate portion 44. In this embodiment, cut lines 46, 48, 50 define three edges of locking aperture 43, shown in Figure 4. The second panel further comprises flexural means 52 to receive a shoulder portion 32 of the locking tab 22 to enable an edge of the locking aperture 43 to be moved out of alignment with the second panel 12 thereby to cause the locking tab 22 to move readily through the locking aperture 43. Preferably, the flexural means is provided by a portion of the second panel 12 which portion includes a cut line 54 that is struck from the second panel. One end of the cut line 54 intersects the side edge of locking aperture 43 to allow the portion to flex. Optionally, the cut line 54 defines a tab 56. Tab 56 is preferably aligned with the shoulder portion 32 to allow it to pass through the aperture 43 without being impeded or forcibly folded out of alignment shown in Figure 4. Preferably, a second cut line 60, is provided struck from the opposite side edge of the retaining tab 44 to define a second tab 62, thereby enabling the second shoulder portion of the locking tab to pass through the aperture without being impeded or forcibly folded out of alignment. Two suitable shapes of cut lines 54, 60 are illustrated in Figures 3 and 6 respectively. It is envisaged that a carton may be provided with a number of locking tabs and retention tabs that are substantially identical to locking tab 22, retention tab 42 and flexural means 52 in order to lock together two panels and are not therefore described in any greater detail. Further, it is envisaged that the panel interlocking means can comprise a "half lock": the locking tab, retaining tab, the flexural means and locking aperture being formed to one side of a notional centre line D only, shown in Figure 3. The general principle of applying an invention of panel interlocking means to a half lock is well known in the art. Thus it will be apparent to a person skilled in the art that the present invention includes half locks incorporating those relevant features of the present invention. In order to lock together first and second panels 10 and 12, they are brought into an overlapping relationship with each other, and locking tab 22 is folded out of alignment with panel 10, shown in Figures 4 and 5. Retention tab 42 is folded out of alignment with panel 12 and locking tab 22 is punched through the aperture 43, which in this embodiment is defined by the retention tab 42. Beneficially, the base of shoulder portion 32 does not need to be substantially deformed to pass through aperture 43 because the flexural means 52, and/or tab 56 is flexed during the punching action to allow the shoulder portion to pass through it with relative ease. As locking tab 22 passes through the aperture 43 shown in Figure 4, it continues to be folded about fold line 24 and into a substantially perpendicular relationship with panels 10, 12 such that locking tab 22 is pushed beyond the distal edge 50 of retention tab 42 shown in Figure 5. Thus, locking tab 22 is held in position because retention tab 42 abuts one side of shoulder portion 32 to prevent it from springing back to its original position and the corresponding edge of aperture 43 may abut thereby retaining locking tab 22 in a substantially perpendicular relationship. As illustrated in Figure 5, the base of shoulder portion 32 is held in place by abutment between the locking edge 40 and the panel portions of the second panel, as the shoulder portions are broader than the locking aperture in vertical or oblique positions. Tension is applied to the first and second panels 10, 12 in opposition to the locking direction; i.e. in a direction tending to move the panels apart. Thus, the butt engagement between the locking tab 22 and retention tab 42 maintain the locking tab 22 in its locked condition. First and second panels 10, 12 remain interlocked because the front edge of aperture 43 is in butt engagement with fold line 24 of panel 10 and, as explained above, the locking edges of locking tab are supported by the panel portions of second panel 12. Furthermore, the arrangement illustrated above can retain the locking tabs when the carton is subjected to compressive forces, for example when the bottom of the pack is squeezed due to a gap between cartons, because of the position of cut lines 54, 60 which allow the shoulder to be supported on portions 70 of second panel, shown in Figure 5. The second embodiment of Figure 6 is substantially the same as the first embodiment, but the profile of the cut line 54, 60 differs. Indeed it is envisaged that other shapes of cut line could be employed in the flexural means 52 without departing from the scope of invention. Referring to Figure 7a, there is shown a third embodiment of the invention in which a pair of panels 110, 112 respectively are adapted to be interlocked and are formed from paperboard or similar foldable sheet material. As in the first embodiment, the panels 110, 112 may. for example, be disposed at the opposite ends of one and the same wraparound carton blank which is to be formed into a carton sleeve including opposed side walls and a top panel, in which panels 110, 112 then provide bottom panels of the carton. The carton is used for packaging a plurality of articles, for example, yoghurt cartons, cans or bottles. First and second panels 110, 112 include panel interlocking means 120 for securing together the panels in overlapping relationship. Panel interlocking 120 means comprises locking tab 122 which is struck from first panel 1 10 and is hingably connected thereto. In this embodiment, the locking tab 122 is defined by a pair of oppositely disposed cut lines 134, 136 to define the side edges of the main portion 130. Tab 122 terminates at an end edge 126 and is separated from first panel 110 by a cut line which connects cut lines 134 and 136 and to define the shape of the main portion. Preferably, the tab 122 is generally elongate in shape. In this embodiment, the cut lines 134, 136 are non-linear to define at least one recess 129. More preferably, the cut lines 134. 136 are serrated, with the or each recess 129 being defined between adjacent teeth. 128. Thus, the tab 122 can be engaged in a number of positions depending upon how much the panels are required to be overlapped. As shown in Figure 7a, a retention tab 142 is struck from second panel 112 which extends into a locking aperture 143. Preferably, retention tab 142 comprises an elongate portion 144 and is separated from panel 1 12 by a pair of cut lines 146, 148 which also define side edges of the aperture 143. A cut line 150 defines an end edge of elongate portion 144. In this embodiment, cut lines 146, 148, 150 define three edges of locking aperture 143, shown in Figure 8a and 8b. It will be seen from Figure 7a that cut lines 146, 148 diverge towards the base of the retention tab 142 to define a part of the aperture 143 in which the locking tab 122 can pass through. The cut lines 146, 148 further define a narrower part 144 of the aperture which is shaped to engage and retain the locking tab 122. Optionally, cut line 125 is provided at the base of retaining tab 142 to make folding the tab 142 easier. In the embodiment illustrated in Figure 7a, the second panel further comprises flexural means 152 to receive a portion of the locking tab 122 and to cause an edge of the locking aperture 143 to be moved out of alignment with the second panel 112 thereby to enable the locking tab 122 to move readily through the locking aperture 143. Preferably, the flexural means 152 is provided by a portion of the second panel 112, which portion includes a cut line 154 struck from second panel. Optionally, the cut line 154 defines a tab 156, adjacent the side edges of aperture 143. More preferably. the cut line 154 extends away from the divergent parts of cut line 146, 148 in a substantially perpendicular relationship thereto. In use, the or each cut line 154 causes the edges of the aperture to flex without tearing thereby to allow the tab 122 to pass through the aperture 143 without being impeded or, in some embodiments, forcibly folded out of alignment. Preferably, a second cut line 154, is struck from the opposite side edge of aperture 143 to define a second flexural means 152, thereby enabling the opposing side edge of the locking tab 122 to pass through the aperture 143 without being impeded or forcibly folded out of alignment. It will be appreciated by those skilled in the art that a carton may be provided with a number of locking tabs and retention tabs which are substantially identical to locking tab 122, retention tab 142 and flexural means 152 in order to lock together two panels and are not therefore described in any greater detail. For example, Figure 7b illustrates a similar lock arrangement to the embodiment shown in Figure 7a with like features designated by the same reference numeral with the addition of letter 'a'. In this embodiment, the serrated edges of cut lines 134a and 136a have been reconfigured so that the teeth of cut line 134a are advanced with respect to the teeth of cut line 136a. The embodiments shown in Figures 7a and 7b are commonly used together in adjacent positions. Further, it is envisaged that the panel interlocking means can comprise a "half lock" shown in Figure 7c. It is evident that the half lock incorporates those relevant features of the present invention to one side of the lock only. The other side of the locking tab 134b comprises a linear cut line 134b and the aperture and retaining tab 142b is defined in part along one side edge by linear cut line 146b . The process for locking together the first and second panels 110 and 112 is substantially identical to the locking together of panels 10 and 12 of the first embodiment, and will not, therefore, be discussed in further detail. Referring to Figures 8a and 8b, once panels 1 10 and 1 12 have been locked together, and locking tab 122 has been folded into a substantially perpendicular relationship with panels 110, 112, it is held in position because retention tab 142 abuts one of it's faces to prevent it from springing back to its original position, and the corresponding edges of aperture 143 engage the opposed recesses 129 of locking tab 122. In those embodiments in which the teeth 128 of the opposing side edges are offset, the locking tab 122 may tend to twist to retain it. As illustrated in Figure 8b, the locking tab 122 is held in place by abutment of the teeth 128 with the second panel, as the teeth are broader than the narrow part of locking aperture 143 in vertical or oblique positions. Again, the arrangement illustrated above can retain the locking tabs when the carton is subjected to compressive forces, for example when the bottom of the pack is squeezed due to a gap between cartons, due to the position of cut lines 154 which allow the shoulder to be supported on tab portions 156 of second panel, and the teeth 128 on each side of the engaged recess 129 of locking tab prevent its movement. The panel interlocking means of the third and fourth embodiments are formed by a similar method to that described above and are not therefore described in any more detail. One advantage of the present invention is that the locking process adopts an interference type fit but with reduced strength requirement of the shoulders of a locking tab during the punching motion: thereby enabling a lower caliper paperboard or greyboard to be used. The present invention and its preferred embodiments relates to a means of locking two adjacent panels in a carton and is shaped to provide satisfactory strength in a locked position but with a degree of flexibility so that the load transferred to the panels is absorbed by the carrier. The carrier can be formed by hand or machinery. It is anticipated that the invention can be applied to a variety of carriers not limited to those of the wraparound type.

Claims: CLAIMS 1. Panel interlocking means for securing together a first and a second panel in overlapping relationship, said panel interlocking means comprising a locking tab struck from said first panel, and a retaining tab defining a locking aperture struck from said second panel, wherein the retaining tab is displaced out of the plane of said second panel to receive said locking tab through the locking aperture to be engaged therewith, characterised in that the second panel further comprises flexural means to receive the locking tab and to enable an edge of the locking aperture to be displaced out of the plane of the second panel thereby to enable the locking tab to move readily through said locking aperture. 2. Panel interlocking means as claimed in claim 1, wherein the flexural means is a tab struck from the second panel adjacent the locking aperture. 3. Panel interlocking means as claimed in claim 2 wherein the flexural tab is positioned adjacent a side edge of the locking aperture. 4. Panel interlocking means as claimed in claim 1 wherein the flexural means is provided by a portion of the second panel adjacent the locking aperture, which portion includes a cut line with opposite ends struck from the second panel, and one end thereof intersects the side edge of the locking aperture, which cut line defines two parts of the second panel portion that is capable of flexing. 5. Panel interlocking means as claimed in claim 1 wherein the intersection between the cut line and the edge of the locking aperture is substantially perpendicular. 6. Panel interlocking means as claimed in claim 5 wherein the cut line is nonlinear, and diverges from its perpendicular intersection with the edge of the locking aperture. 7. Panel interlocking means as claimed in claim 1 wherein second flexural means is provided to receive the locking tab and to enable an opposed edge of the locking aperture to be moved out of alignment with the second panel thereby to enable the locking tab to move through the locking aperture. 8. Panel interlocking means as claimed in claim 4 wherein the intersection is intermediate the ends of the side edge. 9. Panel interlocking means as claimed in claim 1 wherein the locking tab comprises a neck portion hinged at a base thereof to the first panel, and a shoulder portion contiguous therewith. 10. Panel interlocking means as claimed in claim 1 wherein said locking tab comprises at least one recessed portion. 11. Panel interlocking means as claimed in claim 10 wherein the at least one recessed portion is defined by a serrated edge of the locking tab. 12. Panel interlocking means as claimed in claim 10 or claim 11 wherein the displaced edge of the locking aperture defines an acute angle with the edge connecting the retaining tab. 13. A carton blank incorporating panel interlocking means having a first panel and a second panel, said panel interlocking means comprising a locking tab struck from said first panel, and a retaining tab defining a locking aperture struck from said second panel, wherein the retaining tab can be displaced out of the plane of said second panel to receive said locking tab through the locking aperture to be engaged therewith, characterised in that the second panel further comprises flexural means that can receive the locking tab and enable an edge of the locking aperture to be displaced out of the plane of the second panel to cause the locking tab to move readily through said locking aperture. 14. A carton blank as claimed in claim 13, wherein the flexural means is a tab struck from the second panel adjacent the locking aperture. 15. A carton blank as claimed in claim 14 wherein the flexural tab is positioned adjacent a side edge of the locking aperture. 16. A carton blank as claimed in claim 13 wherein the flexural means is provided by a portion of the second panel adjacent the locking aperture, which portion includes a cut line with opposite ends struck from the second panel, wherein one end intersects the side edge of the locking aperture, which cut line defines two parts of the second panel portion that is capable of flexing. 17. A carton blank as claimed in claim 13 wherein the intersection between the cut line and the edge of the locking aperture is substantially perpendicular. 18. A carton blank as claimed in claim 17 wherein the cut line is non-linear, and diverges from its perpendicular intersection with the edge of the locking aperture. 19. A carton blank as claimed in claim 13 wherein a second flexural means is provided to receive the locking tab and to enable an opposed edge of the locking aperture to be moved out of alignment with the second panel thereby to enable the locking tab to move through the locking aperture. 20. A carton blank as claimed in claim 13 wherein the intersection is intermediate the ends of the side edge. 21. A carton blank as claimed in claim 13 wherein the locking tab comprises a neck portion hinged at a base thereof to the first panel, and a shoulder portion contiguous therewith. 22. A carton blank as claimed in claim 13 wherein said locking tab comprises at least one recessed portion. 23. A carton blank as claimed in claim 22 wherein the at least one recessed portion is defined by a serrated edge of the locking tab. 24. Panel interlocking means as claimed in claim 22 or claim 23 wherein the displaced edge of the locking aperture defines an acute angle with the edge connecting the retaining tab.

Inventors: LE BRAS PHILIPPE, LE BRAS, PHILIPPE
Applicants: LE BRAS PHILIPPE, MEAD CORP, LE BRAS, PHILIPPE, THE MEAD CORPORATION
Application year: 1999
Main classification: B65D71
IPC codes: B65D71