FORMATION OF A RIGID BOX FROM A FLAT PREF0R11A
FIELD OF THE INVENTION The present invention relates to a flat preform from which a rigid package is formed. BACKGROUND OF THE INVENTION The flat preform in question can be used profitably, although not exclusively, to produce a rigid cigarette box and, normally, comprises a lower cup-shaped or tank-shaped portion and an upper lid connected to each other by means of of a hinge or joint. Known rigid packs of the type described above usually have a rectangular section, although rigid packs for cigars with other sections, for example, octagonal or the like, have also been proposed. It is known that a rigid pack of the type described above is produced from a flat rectangular, almost rectangular preform having several longitudinal and transverse fold or fold segments, along which the preform is folded to form the pack, wherein the longitudinal fold segments normally define, laterally, two main and parallel side walls and two secondary and parallel side walls, perpendicular to the main walls. Frequently, the walls of the finished pack, in particular the main walls, are not perfectly flat, due to the tendency of the preform, when folded along a fold segment, to return elastically to its original flat shape . To reduce the elastic recovery, it has been proposed to equip the packing machines with weakening units to pre-bend and weaken the preforms along the fold segments, although this solution is effective, it has been found to involve a considerable cost, due to the complex mechanical design of the weakening units.
SUMMARY OF THE INVENTION It is an object of the present invention to provide direct and low cost production, enabling a flat preform, of a rigid box designed to eliminate the aforementioned drawbacks, that is, a pack with practically flat walls. In accordance with the present invention, there is provided a flat preform from which a rigid package is produced, the preform comprises several predefined fold segments and is characterized by the fold segments having at least two different degrees of weakness. The fold segments are preferably positioned so as to form the respective defined edges once the preform has been bent to form the box. The tests have shown, unexpectedly, that regardless of the shape of the package, the curved or arched of the walls of the pack due to the elastic recovery of the preform is practically eliminated by weakening some fold segments more than others. The fold segments that will mostly be weakened to achieve the desired effect obviously depend on the shape of the pack and must be established practically by trial and error. However, tests have shown that any type of pack has a particular combination of fold segments, which, if weakened to a greater degree, determine the obtaining of almost perfectly flat walls without impairing the stability of the pack shape. Take the case of, for example, a packet practically of octagonal section, formed from a practically rectangular preform, comprising longitudinal and transverse fold segments and, where the longitudinal fold segments are aligned along at least two internal longitudinal fold lines and two external longitudinal fold lines. This pack is defined by a cup-shaped body and a cap hinged to the cup-shaped body; the cup-shaped body and the lid have respective major side walls and respective secondary side walls and the transverse fold segments divide a portion of the preform that extends between the two internal longitudinal fold lines to a first panel corresponding to a first main side wall of the cup-shaped body a second panel corresponding to a second main side wall of the cup-shaped body. In this particular case, the walls of the package can be flattened, weakening to a greater degree, more than the other fold segments of the preform, the two longitudinal fold segments located on each side of the first panel and each defining a portion of a respective internal longitudinal fold line and the two longitudinal fold segments located on each side of the second panel and each defining a portion of a respective external longitudinal fold line.
BRIEF DECRIPTION OF THE DRAWINGS Several of the non-limiting embodiments of the present invention will be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a preferred embodiment of the preform, in accordance with the present invention; Figure 2 shows a three-quarter view in perspective of a cigar box, formed from the preform of Figure 1; Figure 3 shows the cross-sections on a larger scale of three embodiments of a detail of the preform of Figure 1; Figure 4 shows a plan view of an alternative embodiment of the preform according to the present invention.
DESCRIPTION OF THE PREFERRED MODALITIES The number 1 of Figure 1 indicates a flat cardboard preform or the like, which can be folded in a known manner to form a rigid box 2 for cigars (Figure 2), in particular, a package of octagonal section of the type described in patent EP-B1-204933. The box 2 comprises a lower cup-shaped reservoir 3 having an upper end
open (not shown) and a cup-shaped upper lid 4, hinged to the reservoir 3 along a joint 5 (Figure 1) to rotate, with respect to the reservoir 3, between an open position (not shown) and a position closed (Figure 2) that closes the open top end (not shown). The lid 4, when closed, imparts to the package 2 a shape practically of straight parallelepiped defined by a side surface 6 and by two flat walls of identical upper and lower ends, 7 and 8, defining axially the lateral surface 6 and which are placed in parallel and face to face with each other. The side surface 6 comprises two secondary flat side walls 9, arranged in parallel and facing each other and two main front and rear flat side walls, 10 and 11, arranged in parallel and facing each other and perpendicular to each other. secondary side walls 9. Secondary side walls 9 and main side walls 10 and 11 are connected to each other by four flat connecting walls 12, each of which forms the respective defined edges 13 with the adjacent side walls 9, 10 and 11. As clearly shown in Figure 2, the lid 4 comprises an upper end wall 7 and a
S2 / 13S upper portion of the lateral surface 6 and the reservoir 3 comprises a lower end wall 8 and the rest of the lower portion of the lateral surface 6. For reasons of clarity, whenever possible, the parts of the preform 1 will be indicated in the following using the same reference numbers, with superscripts, for the corresponding parts of the pack 2. The preform 1 practically has the shape of an elongated rectangle having a longitudinal central axis 14 and a transverse central axis 15, perpendicular to the axis 14. The preform 1 comprises several transversal bending segments 16 pre-stabilized, that is to say, parallel to the transverse axis 15 and several longitudinal bending segments 17 predebilitated, that is to say parallel to the longitudinal axis 14, along which the preform 1 is bent to form the package 2. More specifically, the fold segments 16 and 17 are positioned so as to form the respective defined edges. Once the preform 1 was folded to form the pack 2. The longitudinal fold segments 17 are aligned with each other along four longitudinal lines 18 arranged side by side in pairs and the longitudinal lines 18 of each pair are located one outwardly (18e) and one inwardly (18i), with respect to the longitudinal central axis 14 of the preform 1. The internal longitudinal lines 18i divide the preform 1 into a central strip 19 and two side strips 20 on each side of the strip 19. Working upwards from Figure 1, the transverse fold segments 16 divide the central strip 19 into a panel 10 'defined laterally by two fold segments 17a, aligned with the internal longitudinal lines 18i; a panel 8 '; a panel 11 ', defined laterally by two fold segments 17b aligned with the internal longitudinal lines 18i; a panel 7 'and a panel 10", defined laterally by two fold segments 17c aligned with the internal longitudinal lines 18i The panel 11' corresponds to the rear main side wall 11 of the box 2 and, therefore, of the tank 3 and lid 4 and comprises the joint 5 connecting to the reservoir 3 and the lid 4; the panel 10 'corresponds to the reservoir portion 3 of the front main side wall 10 and the panel 10' 1 of the lid portion 4 of the front main side wall 10 and the panel 10"is attached to a reinforcing strip 21, which is bent over the panel 101 1 to increase the rigidity of the main side wall 10 of the lid 4. The preform 1 also it comprises panels 12 'symmetrically located on each side of the panels 10',
52/136 10 '' and 11 ', to define the connection walls 12 of the pack 2. The panels 12' connected to the panel 101 are defined internally by the fold segments 17a and, externally, by the respective fold segments 17d , aligned with the external longitudinal lines 18e; the panels 12 'connected to the panel 11' are defined internally by the folding segments 17b and externally by the respective fold segments 17e aligned with the external longitudinal lines 18e and the panels 12 'connected to the panel 10' 1 are internally defined by the fold segments 17c and externally by the respective fold segments 17f, aligned with the outer longitudinal lines 18e. Finally, the preform 1 also comprises fins 91, which are bent in squares and overlapped to define the secondary side walls 9 of the box 2 and the connecting tabs 22 connected with the wings 9 'and to impart stability to the box 2. In the embodiment of Figure 1, the longitudinal fold segments 17b, 17d and 17f have a first degree of weakness and the other longitudinal fold segments 17a, 17c and 17e and the transverse fold segments 16, a second degree of minor weakness than the first grade. In other words, the longitudinal fold segments
52/136 17b, 17d and 17f are weakened to a greater extent than the other bend segments 16 and 17. As shown in Figure 3a or 3b, each bend segment 16 and 17 is defined by a respective deformation, size and determined form, of the preform 1 and to achieve different degrees of weakness of the various longitudinal segments 17, the longitudinal segments 17 are defined by the respective deformations of different shapes and / or sizes. In an alternative mode, shown in
Figure 3c, each fold segment 16 and 17 is defined by a respective incision, of certain shape and size, of the preform 1 and to achieve the different degrees of weakness of the various longitudinal segments 17, the longitudinal segments 17 are defined by the respective incisions of different shapes and / or sizes. In additional embodiments not shown, the location of the weakening segments 16 and / or 17 may vary. It should be emphasized that the number of fold segments 16 and / or 17 mostly weakened is preferably weakened to maintain the stable shape of the pack 2, even when it is almost empty and does not correspond to stabilize the group of cigars inside.
52/136 The number 23 of Figure 4 indicates, as a whole, a flat preform of card stock or the like, which is folded in a known manner to form a rigid cigarette box (not shown) of the type described in FIG. Patent application IT-A-BO99A000029 in which the main side walls are convex outwards and are connected with the secondary side walls along the respective edges defined perpendicular to the end walls. Being similar to the preform 1 of Figure 1, the parts of the preform 23 will be indicated hereinafter, whenever possible and for reasons of simplicity, using the same reference numbers as for the corresponding parts of the preform 1 In the preform 23, the longitudinal fold segments 17 are aligned along two longitudinal lines 18, which divide the preform 23 into a central strip 19 and two side strips 20 on each side of the strip 19. Working upwards of Figure 4, the transverse fold segments 16 divide the central strip 19 into a panel 10 'defined laterally by two fold segments 17a; a panel 8 '; a panel 11 ', defined laterally by two fold segments 17b; a panel 7 'and a panel 10', defined laterally by two fold segments 17c.
52 / 13S The panels 10 ', 10' 'and 11' comprise longitudinal fold segments 24 located near the longitudinal lines 18, which, in known manner, impart a curved shape to the outer portions of the main side walls 10 and 11. The difference between the fold segments 24 and the fold segments 16 and 17 resides in that the fold segments 16 and 17 are formed and positioned to form the respective defined edges, once the preform 23 has been bent to form the corresponding pack, while the fold segments 24 are formed and positioned so that they locally bend the preform 23 without borders defined once the preform 23 has been folded to form the corresponding pack. The preform 23 also comprises fins 9 ', which are bent in squares and overlapped to define the secondary side walls 9 of the package and connection tabs 22 connected with the fins 91 and to impart stability to the package. In the embodiment of Figure 4, the longitudinal fold segments 17 all have a first degree of weakness and the longitudinal fold segments 24 all have a second degree of weakness less than the first degree. In other words, all longitudinal bending segments 17 are weakened to a greater extent than longitudinal bending segments 24. In a further embodiment not shown (which applies to both the preforms of Figure 1 and that of Figure 4 ), some transverse fold segments and some longitudinal bend segments have a third degree of weakness and all other fold segments have the second degree of weakness less than the first. In a further embodiment not shown (which applies to both the preform of Figure 1 and that of Figure 4) only limited portions of some fold segments have the first degree of weakness, while the remainder of the portions of the same fold segments and the other fold segments have the second degree of weakness less than the first. 1) In an additional embodiment not shown (which applies to both the preform of Figure 1 and that of Figure 4), the fold segments have three or more different degrees of weakness.