A FOLDING BOX

Abstract: A package of the folding box type comprising side wall panels of cardboard or similar material and end closure panels at each end of the side wall panels. A first set of creasing lines (51) in the longitudinal direction of the folding box define a polygonal folding box cross section. Perpendicular to said first creasing lines there is arranged a second set of creasing lines (53, 53a; 63, 63a) for defining transitions between the sleeve and a respective one of the end closure panels. Adjacent end closure panels (54, 55; 64, 65) are separated by a punch line or a punched out portion (56; 66) which is defined as a punch line (58). The section of this punch line (58) adjacent to a real or an imaginary crossing point between said set of creasing lines is formed as a contiuous panel outer edge line (57), the purpose of which is to uniformly distribute the strain of the plastics layer when folding out the panels (54, 55) in connection with the heat sealing of a membrane to the folding box end.

Description: The present invention relates to a folding box of cardboard or similar material according to the preamble of claim 1, and more particularly to a folding box of the type where a so called membrane is used for sealing and closing at least one end of the folding box. Such membranes have been used for a long time within the present technical field. One example of the basic technique is described in applicant's own UK patent number 729284. The tightness obtained by means of an internal thermoplastic coating and in the actual case, by means of fibre wads at the corners, is fully acceptable for providing a good powder tightness and sufficient tightness for, for instance, deep frozen products such as fruit juice. The said basic technique within the field according tos aid UK patent has been developed by the applicant from time to time. Thus, for instance instead of having fibre wads, "plastics fins" at the corners have been proposed which are obtained by the combination of punching out the cardboard material and extruding a coating. In other folding box applications, for instance, according to US patent number 3040958, the folding box corner problems have been illustrated in connection with a discussion of providing sufficient counter pressure when folding the folding box end flaps inwards. A number of corner arrangements have been suggested, one of which resembles the fibre wad corner mentioned and one using a specific creasing for creating reinforced, counter pressure resisting corner portions especially at the folding box end which is the last to be closed, i.e. after the product has been inserted into the box. However, the other end is not critical according to said patent because then a support placed inside the folding box is used. The object of the present invention is to develop the said corner structure further, so that with a minimum of modifications of existing production equipment and packing lines, respectively, it will be possible to accomplish even better sealing conditions at the corners of the folding box, at one or both ends thereof. Especially the object is to provide better sealing possibilities when using a membrane of the type mentioned in the introduction. The present invention provides a package comprising a sleeve of cardboard or corresponding material formed by side wall panels and end closure panels integral therewith at each end of the sleeve for forming a package of the folding box type, where first creasing lines extending in the longitudinal direction of the folding box define a polygonal cross section of the folding box and second creasing lines perpendicular to said first creasing lines define transitions between the sleeve and a respective one of the end closure panels, the end closure panels being partially separated by a punched-out portion distanced from a real or imaginary straight line joining adjacent said second creasing lines, the said punched-out portion defining a panel outer edge line between each pair of adjacent end closure panel. Such a package is known e.g. from US-A-3040958. The package is characterised in that the said panel outer edge line is a continuously curved and unbroken line which is arranged such that the point of the curve nearest the real or imaginary straight line joining adjacent said second creasing lines is substantially in line with a said first creasing line. In one embodiment a pair of said second creasing lines and the respective one of said first creasing lines belonging thereto start out from substantially one and the same point, which defines one corner at either folding box end. In order to provide rational conditions for sealing, at least the internal side of the folding box is coated by a thermoplastics material, and a closure membrane is sealed to the folding box by being attached to the plastics coating in a region between said panel outer edge lines at either folding box corner, and by being attached in a manner known per se to at least portions of the end closure panels. Preferably, the minimum distance between the point of the curve nearest the real or imaginary straight line joining adjacent said second creasing lines to said line is of the magnitude 1,5 to 4 mm. The invention will now be exemplified by reference to the accompanying drawings, in which Fig. 1 in a partial section shows a corner region of a conventional folding box having the fibre wads mentioned at the introduction, Fig. 2 is a corresponding partial section of another type of conventional fibre wad folding box, Fig. 3 is a corresponding partial section of a folding box, according to the US patent number 3040958 mentioned at the introduction, Fig. 4 shows another embodiment according to the same patent, Fig. 5 shows a first embodiment of the arrangement according to the invention, Fig. 6 shows another embodiment of a corner arrangement according to the invention, Fig. 7 in a perspective view shows a filled folding box closed by a membrane and having folded out end closure flaps. The reference numeral 10 in Fig. 1 denotes a side wall of a folding box blank of cardboard or similar material. The blank is coated by thermoplastics material at least at the side thereof which is to form the inside of the folding box. The numeral 11 denotes a portion of an adjacent side wall or side wall panel. Said panels are separated from each other by a creasing line 12 or a corresponding folding denotation. This folding denotation starts from a point 13, from which a second set of creasing lines 15, 15a also starts out. Such creasing lines 15, 15a, define the boundary line between the side wall panels 10, 11 and the end closure panels 16, 17. In the embodiment according to Fig. 1 there is a punched out region 18 between the panels 16, 17. The punch line 19 continues with a portion 19a below the lowest point of the punch line 20. Between the point 13 and the lowest point of the punch line 19a there is formed a not broken-through material bridge 21, which, when folding out flaps as will be explained later on, forms said "fiber wads" when the tension in the bridge portion 21 exceeds the tension strength or elongation strength. In Fig. 2 there is shown another type of known corner structure. The numerals 22, 23 denote adjacent side wall panels, whilst the numerals 24, 25 and 25a denote creasing lines or corresponding folding denotations. The numeral 26 denotes a punch line, which separates the end closure flaps 27 and 28. In a corresponding manner as in Fig. 1 there is formed a not broken-through material portion 29 the purpose of which is to form the said fiber wad. In the corner structure according to Fig. 3 which represents a known structure, (US 3040958), there are used double creasing lines 29, 30 between adjacent side wall panels 31, 32. A creasing denotation 33, 33a separates the side walls panels 31, 32 from adjacent end closures 34, 35 and a punch line 36 separates the end closures 34, 35. Also in this case, there is formed a not broken through material portion 37 between the lowest point of the punch line and the level defined by a line 33, 33a. In Fig. 4 there is shown a further embodiment according to US patent number 3040958 where side wall panels 38, 39 are separated by double creasing lines 40, 41. The creasing lines 40, 42 define the transition line between the end closure flaps 43, 44 and the side walls 38, 39. A punch line 45 extends down to a point 46, where short creasing lines 47, 48 connect said point to the end points of the double creasing lines 40, 41. In Fig. 5 there is shown a first embodiment of the corner structure according to the invention. Parts of the side wall panels 49, 50 are separated from each other by a creasing line 51, which is terminated upwards in a point 52, which falls on a straight line or even finds the border point between two further creasing lines 53, 53a forming part of the second set of the creasing lines for defining the transition between side walls and end closure panels. In Fig. 5, adjacent end closure panels have been denoted 54, 55. In the actual case a relatively wide punched out region 56 is formed between the panels. The essential point in the present context, however, is that the region 57 of the end closure and panel outer boundary line cut out 56 defines a continuous section into said region 57. This means that the strain, elongation of the plastics coating, at the end closure panels in the region between the point 52 and the section 57 of the outer bondery line, is distributed uniformly, so that the plastics coating or plastics layer actually will be expanded or enlarged when the end closure panels 54, 55 are folded out to a horizontal position when sealing a membrane. The tensioning obtained will be distributed uniformly because the deformation takes place along a continuous line 57 instead of taking place abruptly as in Fig. 1, 2 and 3, where frequently the plastics coating is torn up along a tear up line meaning insufficient sealing along the line and the formation of penetration or leaking channels. The force when folding out the end closure panels 54, 55 is transferred uniformly to the plastics layer in the region between the section 57 and the point 52, meaning that an unbroken sealing area comprising heat sealable thermoplastics is obtained and which area will also be the subject of an enlarging effect due to the folding out and the tensioning following thereafter, however, without any rupture of the plastics coatings. The embodiment in Fig. 6, shows adjacent folding box side wall panels separated by a creasing line 61 which in a point 62 joins an integral creasing line 63, 63a, forming part of a second set of creasing lines. The end closure 64 and 65 are here separated by a somewhat narrower punched out region 66 which, however at the outer part thereof is terminated by a continuous section 67 coresponding to the section 57 in Fig. 5. The so called end closure panel outer boundary line has been identified by the numeral 68. In Fig. 7, there is shown a folding box 69 manufactured from the blank in Fig. 5. The folding box is filled and closed at the top by a sealing membrane 70 of for instance polyethylene coated thin paper. The membrane is sealed against portions of the end closure wall panels according to the invention, in the specific corner regions formed between continuous punched out sections 57 and adjacent crossing points 52 of crease lines 51 and 53, 53a respectively. Although the invention has been exemplified in connection with specific embodiments, it is to be realised that modifications and variants are possible within the scope of the accompanying claims.

Claims: 1. A package comprising a sleeve of cardboard or corresponding material formed by side wall panels (49, 50; 59, 60) and end closure panels (54, 55; 64, 65) integral therewith at each end of the sleeve for forming a package (69) of the folding box type, where first creasing lines (51, 61) extending in the longitudinal direction of the folding box define a polygonal cross section of the folding box and second creasing lines (53, 53a; 63, 63a) perpendicular to said first creasing lines define transitions between the sleeve and a respective one of the end closure panels, the end closure panels (54, 55; 64, 65) being partially separated by a punched-out portion (56, 66) distanced from a real or imaginary straight line joining adjacent said second creasing lines (53, 53a; 63, 63a), the said punched-out portion defining a panel outer edge line between each pair of adjacent end closure panels, characterised in in that the said panel outer edge line is a continuously curved and unbroken line (57, 67) which is arranged such that the point of the curve nearest the real or imaginary straight line joining adjacent said second creasing lines (53, 53a; 63, 63a) is substantially in line with a said first creasing line (51, 61). 2. Package as in claim 1, characterised in that a pair of said second creasing lines (53, 53a; 63, 63a) and a first creasing line (51; 61) belonging thereto originate from one and the same point (52; 63), which defines a corner at either folding box end. 3. Package as in claim 2, where the package is coated by thermoplastics material at least at the inside thereof, characterised in that a closure membrane is sealed to the folding box by being attached to the plastic coating in a region between said panel outer edge lines (57; 67) at either folding box corner (52; 63) and by being attached to at least portions of the end closure panels in a manner known per se. 4. Package as in claim 4, characterised in that the minimum distance between the point of the curve nearest the real or imaginary straight line joining adjacent said second creasing lines (53, 53a; 63, 63a) to said line is of the magnitude 1,5 to 4 mm.

Inventors: BJOERKLUND, BENGT, JOHANSSON, FRANS, STROEM, GOERAN, Björklund, Bengt , Ström, Göran 
Applicants: AB AKERLUND & RAUSING
Application year: 1988
Main classification: B65D5
IPC codes: B65D5