A FOLDING BOX

Abstract: A folding box of cardboard or similar material, comprising a casing having a longitudinal joint (19) and top and bottom end closures and preferably sealing membranes attached to flaps of said end closures. The longitudinal joint (19) of the folding box is formed as an abutting edge joint which at least partially (22, 24, resp.) along a substantial length of the total folding box length has an extension which is not parallel to the side edges of the folding box. Especially in that case where sealing membranes exist, the joint extends the whole way out to the free cut edges of each end flap of the top and bottom end closure, re­ spectively, and the cross section of the folding box is covered by a sealing membrane attached against flaps at each end of the folding box. The longitudinal joint is covered by a strip, placed externally or internally or on both sides of the wall. The strip is of a thin material, preferably of a thickness around 20 - 50 µm and covers the joint at both sides thereof. Preferably the strip has a grip portion (21′) which, when grip­ ped results in tearing up of the folding box side along per­ forations (22) placed outside or inside, preferably inside, the longitudinal edges of the strip (21).

Description: The present invention relates to a folding box of cardboard or similar material according to the preamble of claim 1. Traditionally, folding boxes, i.e. sleeve shaped bodies having end flaps, are glued or assembled such that they get a longitudinal joint which according to the established folding box technique has an overlap. Theoretically, however, the prior art does also disclose a folding box having a non-overlapping joint as shown in US Patent No. 981 993 from 1911. Within another field of the packaging technique, i.e. the technique where sleeves are used, i.e. folding box structures without end flaps, an assembling technique using abutting edge joints is previously known for sleeve blanks. Such packaging sleeves are closed by separate end closures, for instance of metal or plastics. Thus, abutting edge technique has previously been used when manufacturing folding boxes and sleeves, but as far as applicants know, such technique has not been transferred to the field of modern or present day folding boxes. Instead, within such technical field, there has been used an overlap joint of the shearing force joint type, overlap flap joint or any similar arrangement. A folding box of the type mentioned in the preamble of claim 1 is known from, for example, US-A-3 692 226. With this type of package, an overlapping joint extends throughout the length of the container side wall and end flap. A sealing membrane is then applied to the inner surface of the end flaps to provide a membrane-sealed container. However, in the overlap region of the joint where the membrane covers the end flap, a sharp discontinuous transition is presented at which a leakage channel can be formed. Thus, it is an object of the present invention to provide a membrane-sealed folding box in which the risk of leakage is greatly reduced. This object is achieved by a folding box according to claim 1. Preferred embodiments of the present invention are given in the dependent claims. The invention will now be exemplified by reference to the accompanying drawings, where Fig. 1 in a planar view shows a blank of a folding box according to the present invention, Fig. 2 shows the folding box as assembled and flattened; two different types of joints have been shown, Fig. 3 shows the folding box somewhat expanded, Fig. 4 shows the box seen from either one of the ends and with folded out flaps, Fig. 5 in a planar view shows a further embodiment of a folding box blank for a folding box according to the present invention, Fig. 6 shows the folding box blank or blanks in Fig. 5 in an intermediate stage where a sleeve is formed and where in the embodiment shown, the strip securing the joint is extended by a grip portion, Fig. 7 shows the folding box blank in Fig. 6 erected and end closed or sealed by a membrane. The folding box blank in Fig. 1 comprises broad side wall panels 11, 12 and a panel 13 forming a complete narrow side wall and panels 14a, 14b which together are intended to form the second narrow side wall. End flaps 15-17, 18a, 18b and 15'-17', 18a', 18b', respectively, are arranged for forming end closures of the folding box. The blank consists of traditional type of cardboard material or similar. Each partial flap or sub-flap 14a, 14b has a truncated trapezoid extension 14c and 14d, respectively. Said extensions are complementary shaped relative the cut outs 14c' and 14d', respectively, in a corresponding second sub-flap. The end sub-flaps 18a, 18a' have rounded extensions 14e, the shape of each of which is complementary to cut outs 14e' in the end flaps 18b, 18b'. Abutting edge assembling of the sub-panels 14a and 14b gives the discontinuous joint line 19 in Fig. 2 having straight sub-sections 22 which are not parallel to the folding box side edges 20, 21, and subsections 23 parallel to the folding box edges 20, 21 in the narrow side wall forming the assembling side. Instead of straight sub-sections, it is also possible to have curved sections 31, as indicated in Fig. 2, or another type of not rectilinear geometry. In the abutting edge joint assembled sub-section end flaps 18a, 18b and 18a', 18b' there are domed joint sub-sections 24, 25. The fibre direction of the cardboard material is indicated by the double arrow 26. The strength of the folding box crosswise the extension of the line 19 is therefore determined by the fibre breaking strength. In the longitudinal direction of the folding box the grip between the extensions and the cut outs along the line 19 provide a locking effect and a shearing type of joint in the longitudinal direction. In order to guarantee that this shearing joint will not break up because the locking engagement between the extensions and the cut outs is lost due to handling, such elements are anchored by means of a thin strip 27 placed internally and attached to the sub-flaps and the sub-panels such that it covers the entire length of the joint line 19. If required there may also be a strip at the outside of the folding box. As the material of the actual folding box usually is a cardboard material coated by a thermoplastic material, generally polyethylene, the strip may be a thin, say 20-50 µm thick thermoplastic film strip which is sealed against the plastic coated cardboard material. It is also possible to attach a strip also against a non-plastic coated cardboard and of course also against other material than cardboard. Such a strip thickness provides a very safe assembling of the discontinuous joint, and at the same time the assembling technique gives just an unnoticeable thickening or discontinuity 28, 29 in the plane of the end flaps 18a, 18b and 18a', 18b', respectively. This discontinuity is so uncritical that a sealing membrane 30, for instance of a thermoplastic coated paper, is attachable to the folded out end flaps in Fig. 4 without giving penetration susceptible channels along the edges of the strip, which is the one and only area where thickness variations exist on the flap consisting of the strip and the sub-flaps, as the abutting edge joint 19 does not give any addition of material thickness. The folding box blank 10'' in Fig. 5 comprises, in the traditional manner, sub panels 11'', 12'', 13'', 14'' and 11a'' forming the casing part or "sleeve" of the folding box. In the traditional way such sub panels have end flaps 11b'', 11c'', 12b'', 12c'', 13b'', 13c'', 14b'', 14c'' and 11b'', 11c''. In the embodiment shown by solid lines in Fig. 5 the cut edges 15'', 15''' are parallel to the creasing lines 16'', 17'', 18'', 19''. Thus, this embodiment does not form a part of the present invention, but is shown for the sake of clarity only. By the dotted lines 20'', 20''', however, there is shown an embodiment according to the present invention where the cut edges form a joint (abutting edge joint) extending generally in a diagonal direction in the sub flap 11a'' when the folding box is erected. In Fig. 6 the folding box blank in Fig. 5 is arranged as an intermediate product. The joint 15'', 15''' (the solid line version) extends parallel to the long side wall edges of the folding box and on both sides of the joint there is a strip 21'' securing the joint and forming a grip portion by an extended portion 21''' acting as an easy opening arrangement. The strip is of a thin material, within the range from 20 - 50 µm, and for instance it may be a polyethylene strip, which is to be heat sealed against the thermoplastic coated side of the folding box. As "side" the inside of the folding box may be used, which is shown in Fig. 2, but it is here also possible to arrange the strip on both sides of the folding box. Thus, the strip is thin and thereby it does not noticeably increase the thickness of the material in the assembled folding box wall 11'', 11a'', neither at the flaps 11b'', 11b''' nor at the flaps 11c'', 11c'''. When the extension direction of the joint 15'', 15''' is a direction generally perpendicular to the fibre orientation of the cardboard material of the folding box, the general object of the strip 21'' or strips 21'' is to provide a shearing force resisting joint in the plane of the side 11'', 11a''. In certain applications such a joint may be obtained by one single strip at one side of the folding box, in other applications it may be suitable to have double strips. In the embodiment where the joint has a "diagonal" extension 20'', 20''' it may for instance be sufficient to have a single strip, while with a parallel extension 15'', 15''', it may be necessary to have double strips. In preferably all embodiments, arrangements are made for providing a grip portion 21''' for opening the folding box or breaking up of the folding box side 11, 11a. In order to facilitate this breaking up operation there is a longitudinal weakening 22'' (shown by phantom lines) arranged just outside or inside (both alternatives have been shown) the two outer longitudinal edges of the strip. Said weakening denotations form breaking through denotations in the folding box wall as soon as the strip is gripped by the grip portion 21''' and a force is applied along the joint 15'', 15''' or 20'', 20'''. Such a tearing up is of course especially desirable since the folding box has end closures, at one or both ends, obtained by a sealing or closure membrane 23, for instance of a thin paper coated by plastics, aluminum foil or similar. The folding box cross section is efficiently sealed by a membrane which is attached, for instance heat sealed, against horizontally folded out end flaps 12b'', 13b'', 14b'', 11b''. Since the strip 21'' is placed internally in the folding box, this just means a very insignificant thickening of the material of the edge abutting joint formed in the end flap 11b'', 11b''', meaning that the sealing of the membrane 23 is carried out against a generally plane surface. Although a few embodiments have been described and illustrated it is realized that modifications and alternatives are possible within the scope of the accompanying claims.

Claims: A folding box of cardboard or similar material, comprising: a casing having side walls (11, 12, 13, 14; 11'', 12'', 13'', 14'') to define an exterior and an interior and a longitudinal axis, longitudinally extending end flaps (15, 16, 17, 18a, 18b; 11b'', 11b''', 12b'', 13b'', 14b'') integrally connected to said side walls, each said end flap having an interior surface and an exterior surface, a longitudinal joint (19; 20'', 20''') on one side wall (14; 11''), said longitudinal joint extending from said side wall through at least one end flap (18a, 18b; 11b'', 11b'''), and a sealing membrane (30; 23) of a flexible material attached to said interior surface of said end flaps, characterized in that said longitudinal joint (19; 20'', 20''') is an abutting edge joint having along a substantial length thereof at least one portion which is not parallel to said longitudinal axis of said casing, and in that a thin strip (27; 21'') is sealed to the interior of said casing to cover said longitudinal joint, said thin strip (27; 21'') providing only a minimal discontinuity on the interior surface of said end flap so that said sealing membrane (30; 23) provides a hermetic seal even in the area of said thin strip on the interior surface of the end flap with the longitudinal joint. A folding box according to claim 1, characterized in that said abutting edge joint (19) comprises a discontinuous line. A folding box according to claim 1 or 2, characterized in that said abutting edge joint (19) comprises straight portions which are not parallel to the longitudinal axis of said casing and straight portions which are parallel to the longitudinal axis of said casing. A folding box according to claim 3, characterized in that said abutting edge joint (19) is formed by truncated trapezoid extensions (14c, 14d) and complementary cut-outs (14c', 14d'). A folding box according to any of the preceding claims, characterized in that said abutting edge joint (19) comprises portions (31) which are of non-rectilinear geometry. A folding box according to any of the preceding claims, characterized in that said box is provided with a longitudinal weakening (22'') of the cardboard material and that a grip portion (21''') extending from said thin strip (21'') such that said weakenings (22'') are broken when said grip portion is pulled in the longitudinal direction of said weakening. A folding box according to claim 6, characterized in that said longitudinal weakening (22'') is a perforation located in the portion of the casing on which said thin strip (21'') is sealed. A folding box according to claim 7, characterized in that a second thin strip is arranged on the outside of said folding box. A folding box according to claim 1, characterized in that said abutting edge joint (20'', 20''') is generally diagonal across said side wall having said longitudinal joint. A folding box according to any of the preceding claims, characterized in that said thin strip (27; 21'') has a total thickness for about 20-50 µm and that said strip preferably consists of plastic coated paper. A folding box according to any of the preceding claims, characterized in that the casing includes fibre extending in a direction transverse to said longitudinal axis of said casing so as to provide additional strength.

Inventors: AXELSSON, OWE, BIRKENBEUL, HEINZ, HOLMGREN, HARRY
Applicants: AB AKERLUND & RAUSING
Application year: 1987
Main classification: B65D5
IPC codes: B65D5