Panel interlocking means

Abstract: An arrangement for securing together a pair of panels (10,12) comprising a locking tab (14) projecting from an end edge (16) of one of the panels (10) and a locking slit (28) provided adjacent an end edge (12a) of the other of the panels (12) the locking tab and the locking slit are interengaged by relative sliding movement. The locking tab includes an anchoring tab (20) hinged to one side edge of a main portion (18) of the locking tab and the locking tab is sized for insertion into the locking slit when the anchoring tab has been folded into overlapping relationship with the main portion of the tab and the locking slit is opened by displacing a foldable edge strip into an upright position. This upright face of the edge strip is engaged by a trailing edge (24) of the anchoring tab when anchoring tab unfolds into an upright position after the locking tab has been inserted into the locking slit.

Description: This invention relates to panel interlocking means for securing together a pair of panels, for example, adjacent overlapping panels of a paper-board carton. In some situations, these panels are provided by the opposite ends of a wrapper blank which are brought together and interlocked. Locking tabs which are struck from one end of a carton wrapper and which are arranged to be driven through corresponding apertures, defined by retaining tabs, struck from an opposite end of the wrapper are well known e.g. from US Patent No 4,093,116. In the present invention however, the interlocking of panels is effected by causing a locking tab to be engaged by a relative sliding movement into a locking aperture. Known panel interlocking arrangements in which a locking tab is caused to be engaged by relative sliding movement into a locking aperture and in which the locking tab has a hinged "anchoring tab" include FR-A-2 447 863 and US-A-3 191 845. However, neither of these disclosures relates to a blank for forming a wrap-around article carrier as in the present invention. In FR-A-2 447 863 an "anchoring tab" (D) of a locking tab unfolds following engagement in a locking aperture so that a main portion (99) of the locking tab and its anchoring tab are co-planar and it is only when in this co-planar relationship that the anchoring tab is able to engage a panel adjacent the locking slit to prevent disengagement of the locking tab. In US-A-3 191 845 an "anchoring tab" also unfolds somewhat after engagement but does not engage with a foldable edge strip of the panel having the locking slit. Moreover, EP-A-0 150 117 discloses a panel interlocking means in which a series of locking tabs are located on one end panel of a carton blank and a complementary series of locking slits are provided in an opposite end panel of the blank. Both the opposed end panels form overlapping base panels in the completed package. The blank is applied to a group of articles to be packaged in a packaging machine as the articles and blank are conveyed together, through the machine by folding the blank around the article group. Each anchoring tab is folded into overlapping relationship with the main part of the locking tab to facilitate insertion into a locking slit during the folding operation of the blank. The locking slit is formed in a fold line of its associated panel the fold line being spaced inwardly from the end edges of that panel to define a foldable edge strip. The anchoring tab remains in its folded overlapping relationship and has a trailing edge which lies substantially parallel to an abutment edge of the locking slit. The trailing edge and the abutment edge cooperate when the locking tab is engaged, to hold the locking tab engaged in the locking slit. One aspect of the present invention provides a wraparound type carton blank which may have a pair of panels in which a locking tab projects from an end edge of one of said panels said locking tab having a leading main portion and an anchoring tab provided with a trailing edge which tab is hinged to one side of said main portion, and a locking slit provided adjacent an end edge of the other of said panels said locking slit being disposed along a fold line spaced inwardly from, and extending substantially parallel to the end edge of said other panel to define a foldable edge strip wherein said anchoring tab is adapted to be folded into overlapping relationship with said main portion in order to size the locking tab for insertion into said locking slit said locking slit being adapted to accept the folded arrangement of said locking tab in a relative sliding movement of said pair of panels in substantially coplanar relationship with respect to each other only when said edge strip is folded into an upright position relative to said other one of said panels, said other panel having a guide projection wherein the width of said projection is less than the length of the locking slit which projection is deployed to project outwardly of said fold line when the edge strip is folded into said upright position and wherein a leading nose of the locking tab is adapted to cooperate with said projection to aid in the alignment of the locking tab into the locking slit during locking, the width of said locking slit corresponding to the width of said locking tab, whereafter the anchoring tab is free to move out of overlapping relationship with said main portion and adopt an abutting relationship with said edge strip. According to a feature of this aspect of the invention, said locking slit may be disposed essentially entirely along said fold line. According to another feature of this aspect of the invention, the side edge of the locking tab opposite the edge to which the anchoring tab is hinged may be curvilinear. According to yet another feature of this aspect of the invention, said locking slit may be in the form of a shallow "V" which extends into said edge strip and interrupts said fold line. According to a further feature of this aspect of the invention, said locking slit may be asymmetrical so that the legs of said "V" are of different lengths. According to another feature of this aspect of the invention, said locking slit may comprise a first part extending towards the end edge of said other panel at an acute angle with respect to said fold line, a return part extending back to meet said fold line at an acute angle with respect thereto and an end part extending substantially along said fold line. In the present invention the arrangement is similar except that the foldable edge strip and anchoring tab cooperate when in an upstanding position relative to their associated carton panels in order to hold the locking tab engaged in the locking slit. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- FIGURE 1 shows a pair of panels, which are opposite ends of a wrap-around carton blank, in close proximity, one of which includes a locking tab and the other of which includes a locking slit; FIGURE 2 is a perspective view of the panels of FIGURE 1 immediately prior to being interlocked and where the anchoring tab is in an intermediate folded position; and FIGURE 3 shows the panels rotated through 180 degrees and inverted from the position shown in FIGURE 2 and in which the panels are interlocked with both the anchoring tab and edge strip in an upright position. Referring to the drawings, a pair of panels 10 and 12 respectively, are adapted to be interlocked and are formed from paperboard or similar foldable sheet material. The panels 10 and 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 in which panels 10 and 12 then provide bottom panels of the carton. Panel 10 includes a locking tab 14 projecting outwardly in the plane of the panel from the end edge 16. The locking tab 14 comprises a main portion 18 and an integral anchoring tab 20 which is hinged to one side edge of the main portion 18 along a fold line 22. The fold line is substantially perpendicular to the end edge 16 of panel 10. The trailing edge 24 of the anchoring tab is spaced from end edge 16 and, in use, provides a locking edge for cooperation with an abutment face of a foldable edge strip 32 of panel 12. The main portion 18 is formed to include a nose 26 which projects beyond the foldable anchoring tab to lead insertion of the locking tab in a locking slit of panel 12. Panel 12 includes a locking slit 28 in the form of a shallow "V" which is struck from panel 12 along a fold line 30 extending parallel to the end edge 12a of panel 12. Thus, the foldable front edge strip 32 is provided. The slit is formed by a continuous cut line comprising a first part 34 extending along strip 32 towards the end edge of the panel at an acute angle with respect to fold line 30; a return part 36 extending back to meet fold line 30 at an acute angle with respect thereto; and an end part 38 extending along fold line 30. When front edge strip 32 is folded out of the plane of the blank the slit is opened and the first and return parts 34 and 36 define a guide projection 40 extending outwardly from fold line 30. In order to lock together panels 10 and 12, first the anchoring tab 20 is folded 180 degrees about fold line 22 into face contacting overlapping relationship with the underside of the main portion 18. Also the foldable edge strip 32 is folded about fold line 30 out of the plane of the blank (Figure 2) into an upright position relative to panel 12 to open the slit 28. Once the anchoring tab has been folded thus, the maximum transverse dimension (corresponding to the maximum width of the main portion) from fold line 22 to the opposite edge of the tab is sized so that the locking tab can be slidingly engaged in the locking slit 28. The locking tab may be an interference fit in the locking slit. Hence, locking tab 14 can be inserted into the slit until the trailing edge 24 of the anchoring tab has moved past, that is to say, cleared the locking slit. The natural resilience of the paperboard material then allows the folded anchoring tab automatically to spring back into a more upright position, unless otherwise constrained, whereby the trailing edge 24 at or adjacent fold line 22 is brought into a position in which it will abut against the upright face of the edge strip 32 when tension is applied to the panels in opposition to the locking direction i.e. in a direction tending to move the panels apart. Thus, the abutting engagement between trailing edge 24 and the edge strip 32 maintains the panel locked together. The projection 40 and the nose 26 of the locking tab 14 cooperate to aid in the alignment of the locking tab into the slit during locking.

Claims: A wraparound type carton blank having a pair of panels (10,12) in which a locking tab (14) projects from an end edge of one of said panels (10) said locking tab (14) having a leading main portion (18) and an anchoring tab (20) provided with a trailing edge (24) which tab (20) is hinged to one side of said main portion (18), and a locking slit (28) provided adjacent an end edge (12a) of the other (12) of said panels said locking slit (28) being disposed along a fold line (30) spaced inwardly from, and extending substantially parallel to the end edge (12a) of said other panel (12) to define a foldable edge strip (32) wherein said anchoring tab (20) is adapted to be folded into overlapping relationship with said main portion (18) in order to size the locking tab (14) for insertion into said locking slit (28) said locking slit (28) being adapted to accept the folded arrangement of said locking tab (14) in a relative sliding movement of said pair of panels (10, 12) in substantially coplanar relationship with respect to each other only when said edge strip (32) is folded into an upright position relative to said other one of said panels (12), said other panel (12) having a guide projection (40) wherein the width of said projection (40) is less than the length of the locking slit (28) which projection (40) is deployed to project outwardly of said fold line (30) when the edge strip (32) is folded into said upright position and wherein a leading nose (26) of the locking tab (14) is adapted to cooperate with said projection (40) to aid in the alignment of the locking tab (14) into the locking slit (28) during locking, the width of said locking slit (28) corresponding to the width of the folded arrangement of said locking tab (14), whereafter the anchoring tab (20) is free to move out of overlapping relationship with said main portion (18) and adopt an abutting relationship with said edge strip (32). An arrangement according to claim 1, wherein said locking slit (28) is disposed essentially entirely along said fold line (30). The arrangement according to any of the preceding claims, wherein the side edge of the locking tab (14) opposite the edge to which the anchoring tab (20) is hinged is curvilinear. The arrangement according to any of the preceding claims, wherein said locking slit (28) is generally in the form of a shallow "V" which extends into said edge strip (32) and interrupts said fold line (30). The arrangement according to claim 4 wherein said locking slit (28) is asymmetrical so that the legs (34, 36) of said "V" are of different lengths. The arrangement according to any preceding claim wherein said locking slit (28) comprises a first part (34) extending towards the end edge (12a) of said other panel (12) at an acute angle with respect to said fold line, a return part (36) extending back to meet said fold line at an acute angle with respect thereto and an end part (38) extending substantially along said fold line.

Inventors: CHAUSSADAS JEAN, CHAUSSADAS, JEAN
Applicants: MEAD CORP, THE MEAD CORPORATION
Application year: 1985
Main classification: B65D71
IPC codes: B65D71