Panel interlocking means for cartons

Panel interlocking means secures together first and second panels in overlapping relationship. The first panel comprises a locking tab struck therefrom adjacent the free edge thereof The locking tab extends away from the free edge of the first panel and defines a first aperture in the first panel. The locking tab has a neck portion hinged at its base to the first panel and terminates in its shoulder portion. The second panel includes a second aperture struck therefrom adjacent the free edge thereof. The second aperture receives the locking tab such that when the panels are locked together, the free edge of the second panel is located along the locking tab between the base of the neck portion and the shoulder portion, and the locking tab is engaged with an edge of the first aperture.

This invention relates to panel interlocking means 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.
 Locking tabs which are struck from one end of the carton wrapper and which
 are arranged to be driven through corresponding apertures defined by
 retaining tabs, struck from an opposite end of a wrapper are well known.
 However, in the present invention, the interlocking of panels is effected
 by causing a locking tab to be engaged through an aperture. In the present
 invention, locking tabs are directed away from the free end of their
 respective panel, such configurations are known, for example, U.S. Pat.
 No. 3,351,263 (Wood). This application shows a locking arrangement in
 which a first panel includes a locking tab which is directed away from
 free end of the first panel. A second panel includes a first aperture
 through which the tab is passed and then passed over a portion of the
 panel located beyond the aperture and is inserted through a second
 aperture in select combination.
 A problem associated with known locking arrangements is that the forming of
 such locking arrangements is complicated and requires additional features,
 for example, additional retaining means or apertures. The more complicated
 arrangements also require precise registration of the two panels that are
 to be interlocked.
 The present invention seeks to mitigate the problems outlined above by
 providing a simplified but secure locking arrangement.
 One aspect of the present invention provides panel interlocking means for
 securing together a first and a second panel in overlapping relationship,
 the first panel comprising a locking tab struck from the first panel
 adjacent a free edge thereof and extending away from the free edge of the
 first panel. The locking tab has a neck portion hinged at a base thereof
 to the first panel and terminating in a shoulder portion and wherein the
 second panel includes an aperture struck from the second panel adjacent a
 free edge thereof and wherein the aperture is adapted to receive the
 locking tab such that when the panels are locked together the free edge of
 the second panel, outboard of the aperture, is located along the locking
 tab between the base of the neck portion and the shoulder portion.
 According to an optional feature of this aspect of the invention the neck
 portion may include a transverse fold line so that the shoulder portion is
 hinged relative to the neck portion.
 According to another optional feature of this aspect of the invention a
 locking edge may be formed between the underside of the shoulder portion
 and the neck portion. Preferably, the locking edge is adapted to
 interengage with a complementary edge of an aperture of the first panel
 which was created by the formation of the locking tab
 Another aspect of the present invention provides panel interlocking means
 for securing together a first panel and a second panel in overlapping
 relationship, the first panel comprising a locking tab struck from the fit
 panel adjacent to the free edge thereof and extending away from the free
 edge of the first panel, the locking tab having a neck portion hinged at a
 base thereof to the first panel and terminating in a shoulder portion, and
 wherein the second panel includes an aperture struck from the second panel
 adjacent the free edge thereof, and wherein the aperture is adapted to
 receive the locking tab such that the locking tab overlaps part of the
 second panel between the aperture and the free edge, and wherein a locking
 edge of the locking tab is provided at each of the opposed side edges of
 the locking tab at the transition between the neck portion and the
 shoulder portion to interengage with complementary edges of an aperture
 created by formation of the locking tab to maintain the first panel and
 the second panel in a locked overlapped relationship.
 According to an optional feature of this aspect of the invention, the neck
 portion may include a transverse fold line so that the shoulder portion is
 hinged relative to the neck portion adjacent the locking edges.
 According to another optional feature of this aspect of the invention, the
 locking edges of and the complementary edges may be curvilinear.
 Another aspect of the invention provides a method of securing together a
 first panel and a second panel in overlapping relationship, the first
 panel comprising a locking tab struck from the first panel adjacent a free
 edge thereof and extending away from the free edge of the first panel, the
 locking tab having a neck portion hinged at the base thereof to the first
 panel adjacent the free edge and terminating in a shoulder portion, and
 wherein the second panel includes an aperture struck from the second panel
 adjacent a free edge thereof, which method comprises the following steps:
 (i) folding the locking tab out of the plane of the first panel and
 towards the free edge thereof; (ii) bringing the first and second panels
 into overlapping relationship so that the aperture and locking tab are
 brought into registry; (iii) inserting the locking tab through the
 aperture; and (iv) folding the locking tab into overlapping relationship
 with the second panel between the aperture and free edge thereof towards
 its original position and inserting it through the aperture from which the
 locking tab was struck such that the locking tab is interengaged with an
 edge portion of the tab aperture such that the first and second panels are
 locked together in overlapping relationship. Preferably, the free edge of
 the second panel outboard of the aperture is located along the locking tab
 between the base of the neck portion and the shoulder portion.
 Another aspect of the invention provides a carton blank incorporating panel
 interlocking means having a first panel and a second panel, the first
 panel comprising a locking tab struck therefrom including a neck portion
 and a shoulder portion, the neck portion being positioned adjacent to the
 free edge of the first panel and hinged to the first panel by a fold line
 at the base of the neck portion and wherein opposed side edges of the
 locking tab at the transition between the neck portion and shoulder
 portion are each shaped to define a locking edge extending from the tab to
 cooperate with an adjacent locking edge formed in the first panel and
 wherein a locking aperture is struck from the second panel spaced from its
 free edge to receive the locking tab.
 According to an optional feature of this aspect of the invention, said neck
 portion may include a transverse fold line so that said shoulder portion
 is hinged relative to the neck portion.
 According to another optional feature of this aspect of the invention,
 there may further comprise a locking edge formed between the underside of
 said shoulder portion and said neck portion, said locking edge being
 adapted to internegage with a complementary edge of an aperture of the
 first panel which was created by the formation of said locking tab.
 Preferably, said locking edges and said complementary edges are
 curvilinear.

Referring to the drawings, a pair of panels 10, 12 respectively are adapted
 to be placed in an overlapping relationship and 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 carton
 blank which is to be formed into a carton sleeve in which panels 10, 12
 then provide bottom panels of die carton. The carton is used for packaging
 a plurality of articles, for example, cans. It is envisaged that the panel
 interlocking means for securing together a first and second panel can be
 incorporated into a variety of carton types, for example wraparound,
 basket or fully enclosed without departing from the scope of invention.
 Locking tab 14 is struck from panel 10 and is hingeably coated thereto by
 fold line 16 with the locking tab extending away from the free edge. In
 this embodiment, the fold line 16 is substantially parallel to and spaced
 from the end edge 18 of panel 10. The locking tab 14 comprises a neck
 portion 20 and a "shoulder" or main portion 22. The neck portion 20 is
 hingeably connected to first panel 10 along fold line 16. As shown in FIG.
 1, a pair of oppositely disposed cut lines 24, 26 define the side edges of
 the neck portion 20 and the main portion 22 is hingeably connected to neck
 portion 20 along a transverse fold line 28 which is substantially parallel
 to fold line 16. Optionally, fold line 28 is separated by a cut line 30 to
 make folding the shoulder portion 22 easier.
 The shoulder portion 22 is separated from panel 10 by a cut line 32 which
 in this embodiment is substantially "D shaped": the cut line 32 can also
 define a pair of interlocking parts 34, 36 positioned along the opposing
 side edges of shoulder portion 22. Preferably, the cut lines 24, 26 are
 curvilinear to define a pair of oppositely disposed an anchor tabs 38, 40
 connected to first panel 10 and positioned adjacent to side edges of neck
 portion 20. Thus, at the intersection of cut lines 24 and 30 and cut lines
 26 and 30, a locking edge 42, 44 which in this embodiment is substantially
 hook shaped is formed for interlocking parts 24, 26 respectively.
 As shown in FIG. 1, an aperture 46 which is preferably elongate in shape,
 is struck from panel 12, being substantially parallel to the free edge 48
 of second panel 12 and comprising a front edge 50 and a rear edge 52, the
 front edge 50 being nearer to the free edge 48 of panel 12. Preferably,
 the front edge 50 of aperture 46 is spaced from the free edge 48 of panel
 12 by a distance d which corresponds approximately to the length of neck
 portion 20 (shown in FIG. 3). In this embodiment, the free edge 48 is
 formed with an indentation 49 so that the distance is reduced to the
 correct dimensions outlined above. In this embodiment, there are two
 further locking tabs 60 and apertures 62 which are substantially identical
 to locking tabs 14 and aperture 46 and are not therefore described in any
 greater detail.
 Turning to the construction of the panel interlocking means, illustrated in
 FIGS. 2 to 4, the blank requires a series of sequential folding
 operations. The folding process is not limited to that described below and
 can be altered according to the particular manufacturing requirements.
 One method of locking together panels 10 and 12 is first fold the locking
 tab 14 about fold line 16 into a substantially face contacting overlapping
 relationship with portion of first panel 10. The panels 10 and 12 are
 brought into an overlapping relationship with each other, and locking tab
 14 can then be folded out of alignment with panel 10 and through aperture
 46, as illustrated in FIG. 2. It will be appreciated by those skilled in
 the art that the locking tab may be an interference fit with the locking
 aperture. One advantage of the present invention is that the locking
 process does not require precise registration of the two panels 10 and 12,
 because locking tab 14 is self locking in its own aperture.
 The natural resilience of the paperboard material then allows the locking
 tab to automatically spring back in the direction F into its original
 position as shown in FIG. 3. Optionally, guide means is used if
 manufacturing requirements or the carton design means that the locking tab
 14 needs to be guided back to its original position. Optionally, the
 shoulder portion 22 of locking tab 14 is folded out of alignment with neck
 portion 20 along fold line 24. In this embodiment, locking tab 14 is
 pushed in the direction G through the aperture 54 created by the formation
 of locking tab 14 such that the interlocking parts 34, 36 and the anchor
 tab 38, 40 may interengage, as shown in FIG. 4.
 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 butt
 engagement between the interlocking parts 34, 36 and the anchoring tabs
 38, 40 maintain the locking tab 14 in its locked condition. Panels 10, 12
 remain interlocked because the front edge of aperture 46 is located along
 the locking tab 14 between the base of the neck portion and the shoulder
 portion 22 and, preferably, in butt engagement with fold line 16 of panel
 10.
 Thus, the free edge of panel 12, outboard of the aperture 48 is located
 along the locking tab between the base of the neck portion and the
 shoulder portion.
 Further, or alternatively, the locking tab overlaps part of the second
 panel between said aperture and said free edge, and wherein a locking edge
 of the locking tab is provided at each of the opposed side edges of the
 locking tab at the transition between the neck portion and the shoulder
 portion to interengage with the free edge of the second panel outboard of
 said aperture located along the locking tab between the base of said neck
 portion and said shoulder portion.
 The present invention and its preferred embodiment relates to a means of
 locking two adjacent panels in a wraparound carton and is shaped to
 provide satisfactory strength to maintain the panels in a locked position
 but with a degree of flexibility so that the load transferred to the
 panels is absorbed by the carrier. The shape of the blank minimises the
 amount of paperboard required. The carrier can be formed by hand or
 automatic machinery. It is anticipated that the invention can be applied
 to a variety of carriers not limited to those of the wraparound type.