DE69506464T2 - Box made from a blank, corresponding blank and method for producing the box - Google Patents

Abstract

The bottom of a paperboard carton has flat panels, with overlapping edge portions, in which respective corresponding flaps are provided. Either one or other of the flaps is folded down so that the other flap overlies the folded flap before the carton bottom is hermetically sealed. The advantage of the invention is that a common carton blank can be used to avoid problems of carton orientation, the folded flap avoiding problems due to cut edges of paperboard coming into contact with the carton contents. <IMAGE>

Description

This invention relates to a box blank, a box formed from the blank and a method for producing a box.

Boxes are usually made from a cardboard coated on both sides with a thermoplastic film, such as polyethylene. A blank of this material is formed into a sleeve, for example of square cross-section, and then walls at respective ends of the sleeve are folded inwards to form the box top and bottom. Overlapping edge regions of these walls are heated and subjected to pressure to weld the seam edges together and seal the box top and bottom.

Cartons typically contain liquid foods such as milk, fruit juice and non-alcoholic beverages. Some foods are manufactured in a form intended to have a very long shelf life. The carton manufacturer is therefore expected to provide cartons that are relatively free of microbial contamination such as fungicidal spores and bacteria. These could otherwise initiate decomposition of the food, thereby reducing the potential shelf life. Microbes can be inherent in the cardboard and are trapped between the thermoplastic films when the cardboard is coated. If the coated cardboard is then cut and folded so that a "raw edge" of the cardboard can come into direct contact with the contents of the carton, microbial contamination can occur.

Another problem facing carton manufacturers and the food industry is how to create reliable hermetic seals so that cartons filled with product do not leak as a result of subsequent handling. In a typical carton, top and bottom walls are hemmed and folded to form a gable top and a flat base. This is accomplished by equipment that receives sleeves formed from blanks which are then conveyed one at a time between several work stations at which respective operations are performed. For example, an operation sequence may include (a) initial sleeve formation, then within the equipment (b) forming the carton bottom and making a hermetic seal, (c) attaching a pouring spout to one of the walls which will form a gable top, (d) filling the carton, and (e) forming the carton top and making the final hermetic seal. Each step in the sequence must be carried out in a repeatable and reliable manner to produce hermetic seals. The food industry, for example, is very competitive and there is a need for equipment that can operate at ever-increasing speeds to fill and seal a greater number of boxes within a given time. High-speed equipment is carefully designed and to ensure that hermetic seals can be produced in a repeatable and accurate manner. However, sometimes wear and tear or some other factor can create conditions where folds and seams are not as complete as they should be and minor variations can affect the integrity of the hermetic seals. Accordingly, any simplification in the design or handling of the boxes is of great benefit to the manufacturers.

Equipment is designed to form, fill and seal boxes, but the boxes are also designed to suit the characteristics of the machines. Certain features of the boxes, such as the size and position of the folds, the manner in which the walls are folded, the arrangement of the fittings (such as pouring spouts) and the manner in which information is printed on the box, will vary in accordance with differences in automated form and fill techniques. For example, a box top fold seal may be either parallel or normal to the seal that seals the box bottom. It may be necessary to attach a fitting to one of the sloped side walls in a box top. In either or both cases, it is important to note the orientation of the box as it progresses from one work station to another to ensure that the box is correctly presented or offered to a tool performing a particular task. In addition, the carton can be designed to avoid as far as possible the need for a device that rotates the carton to a different orientation prior to performing the operation on a work station. In the case of twin lane systems, which can be used to double the production speed, carton blanks that are mirror images of each other are required so that "right-handed" cartons are fed on one lane while "left-handed" cartons are fed on the other lane. (The abbreviations are RH and LH and are used hereinafter to indicate such orientations.) However, there is then the disadvantage of having to produce both RH and LH cartons. There is also the problem of misfeeding and/or loss of phase if RH and LH cartons are not fed alternately on the transport path. If the operator refills an LH lane with RH cartons, this will stop and/or jam the machine. It will then have to be shut down and serviced to remove the damaged carton, interrupting work and causing a loss in production. This will also occur if, for any reason, two LH or RH cartons are accidentally fed one after the other.

The bottom of a typical cardboard box comprises opposing flat walls and inwardly folded walls. The folded walls allow the flat walls to be folded towards each other so that an edge portion of one flat wall overlaps a corresponding edge portion of the other flat wall to form a flat bottom. Heat and pressure are applied to the overlapping areas to form a seam. To avoid the problem of a "raw edge", a so-called "J-fold" can be applied in a narrow flap in the edge areas of one of the planar walls, as disclosed in EP-A-0 112 553 (this will be explained in more detail below). However, at least in the twin-lane system, for example, the J-fold must be oriented with respect to other features of the box and it is necessary to reverse the order in which the planar walls overlap each other in the twin-lanes and both RH and LH boxes are then required.

The invention seeks to avoid the aforementioned problems, particularly when a box bottom is formed and sealed, and to provide a box which can be manufactured from a common blank, at least in most cases.

According to one embodiment of the invention we provide a box formed from a blank, which blank is formed into a sleeve having respective walls formed into a box top and a box bottom, the box bottom being formed by opposed planar walls and opposed inwardly folded walls, the folded walls enabling the planar walls to be folded onto one another so that an edge region of one planar wall overlaps the corresponding edge region of the other planar wall, regions of the walls including the overlapping edge regions being capable of being welded together to hermetically seal the box bottom, characterised in that slots are made at substantially corresponding positions in the edge regions of both opposed planar walls to define respective tabs; the tabs being arranged so that when the edge regions are caused to overlap, any one of the tabs is folded downwards and the other tab covers the folded tab; wherein the flap to be folded downwards is selected taking into account the intended orientation of the box prior to sealing the box bottom and forming the folded edge on the inside of the box extending between the folded walls.

The invention also extends to a method of forming a box and to the box blank as mainly claimed in claims 4 and 8.

Although the invention is not limited to use in twin web machines, a particular advantage of these flaps is that a common design of the box blank can be used to provide cuffs to serve both RH and LH webs of a twin web machine. Although the flat walls are made to overlap differently in the RH and LH webs, any of the flaps can be folded down to provide a "raw edge" on the inner surface of the box bottom (normally bridged by the tips of the triangular areas formed by the inwardly folded and creased Since a common box blank design can be used, there will be no need to print two different orientations of the design on the box blanks for use in the RH and LH lanes.

A further advantage occurs when fittings such as screw cap spouts are applied to the boxes. In a single lane system it is possible to provide a mechanism on each side of the lane to apply fittings.

In twin track systems, space is a limiting factor between the tracks and equipment to be mounted on the outside of each track. This requires the use of both RH and LH boxes. However, the flaps of the invention avoid the need for such mirror image boxes. Although a box in one track is rotated through 180º with respect to a box in the other track, any of the flaps can be folded down so that the other flap covers it before the bottom walls are subjected to heat and pressure to effect the seal.

Preferably, one of the flaps is slightly smaller than the other so that the opposite edges of the smaller flap are spaced inwardly from the corresponding side edges of the larger flap. This ensures that a better seal is made when the box bottom is welded. There is no need to space the top edge of one flap inwardly from the top edge of the other flap because the top edge of the folded flap will effectively retract due to folding, e.g. one flap is folded and the other is not in the sealed box bottom. However, one top edge could be spaced inwardly from the other if desired.

The invention can be applied to boxes of various designs as long as the bottom is formed by opposing flat walls and opposing folded walls or their equivalent.

The tabs allow a very simple solution but a surprisingly good result. It is not obvious to create slots in the edge areas of both opposing, flat walls because this would obviously increase the risk of leakage. In the "single J" design of the box known from the prior art, the tab of the edge area of one wall is clamped under the edge area of the opposite wall and almost completely covered by it. The single pair of slots is therefore completely covered by the edge area of the "top" wall. This complete coverage is obviously lost by providing pairs of slots in the edge areas of both opposing tab walls.

According to the invention the slots are located in substantially corresponding positions in the opposing flat walls and this would obviously increase the risk of leakage. Surprisingly this has not occurred in practice and the integrity of the seal is good. The seal durability is further improved by making one flap slightly smaller than the other because with a box made of plastic coated cardboard for example the molten plastic can flow over the edges of the smaller flap and onto the edge areas of the larger flap which is not covered by the smaller flap when the box bottom is welded.

Carton and machine manufacturers have made several attempts in the past to solve the type of orientation problem mentioned above, but despite the long-term existence of the well-known single "J-folds", no solution has been proposed in the industry that depends on using a double-contacting tab design such as that taught by this invention.

The above problems will be better understood with reference to the following description of certain prior art boxes. This and a description of a preferred embodiment of the invention is given with reference to the accompanying drawings in which

Fig. 1 is a perspective view of a typical prior art paperboard box;

Figures 2 and 3 are perspective views of the bottom of the carton shown in Figure 1, showing early and late closure states respectively;

Figures 4, 5 and 6, 7 are various pairs of perspective views of the prior art box bottom with a single J-fold and a box bottom of an embodiment of the invention;

Figures 8, 9 and 10 are a plan view looking downwards from the inside and a plan view from the underside and a section along the line X-X of the prior art floor shown in Figure 3, respectively;

Figs. 11, 12 and 13 are similar views of the box bottom shown in Figs. 4, 5;

Figures 14, 15 and 16 are also a similar view of the box bottom according to an embodiment of the invention shown in Figures 6, 7, Figure 17 being a section along the line BB, the tabs being folded in one way;

Fig. 18, 19 and 20 are similar views of the box bottom shown in Fig. 6, 7, Fig. 21 being a section along the line BB, the flaps being folded in the other way;

Fig. 22 shows the tabs superimposed to show their relative sizes; and

Fig. 23 shows the bottom of the box with embossed post markings.

Referring to Figures 1-3, a paperboard box 1 is made from a square cross-section blank formed into a collar 2. The box has a gable made of opposed sloping flat walls 3a, 3b and opposed inwardly folded walls 4a, 4b (4b not visible). Upper edge portions of these walls meet at a vertical spine 5 which is welded by the application of heat and pressure to close the top of the box after it has been filled. Features such as tear-off tabs and screw-top pouring spouts can be applied to boxes. Box 1 has a pouring spout 6 located in a hole in wall 3a. The grommet 6, which has a screw thread, has a flange welded to the wall 3a and a screw cover 7 as a removable closure.

The box bottom 8 is flat and its basic method of construction is shown schematically in Figs. 2 and 3. Opposing flat walls 9a, 9b can be folded towards each other due to the "concertina" cooperation of opposing folded walls 10a, 10b. Folds shown in the drawings and known from the prior art facilitate the folding. The folding is carried out by a machine (not shown or described) also known from the prior art. Fig. 3 shows a state in which the folding is almost completed and in which edge regions 9c, 9d of the walls 9a and 9b respectively overlap each other so that they can be welded together. A central part of this overlap covers triangular parts of the folded folds in the walls 10a, 10b. Since the welding technique is generally known from the prior art, it will not be described in detail. It is noted, however, that the folds, folds, shape and position of the walls is such that the paperboard is deformed and welded so that the cut edges of the paperboard are sealed as far as possible (except as described with reference to Figs. 8-10) so that any liquid in the box does not come into contact with such edges.

Referring to Figure 8, which is a plan view of the prior art cutaway box bottom 8, the triangular areas 11 can be seen looking down into the interior of the box. One of the overlapping edges 12, e.g. of the wall 9b, can also be seen and is slightly offset from an axis passing through each triangular apex. Since the board is coated on both of its major surfaces with a plastic film 13, the board 14 is sandwiched between the sheets 13. Therefore, a cut or "raw" edge of the board remains when the sheet is cut. Due to the way in which the box bottom is formed, a raw edge 12 extends between the triangular shaped areas 11, although other raw edges (hidden behind triangular shaped areas 11) can be sealed due to their positions and the deformability of the board when the box bottom is sealed. Since the edge 12 of the wall 9b is a raw edge, it can contaminate the contents of the box (as is also shown in section XX of Fig. 10). Fig. 9 is a plan view of the underside of the prior art box bottom 8 showing the other raw edge 15 of the wall 9a, but this is of no importance because it is outside the box. Fig. 9 also shows a crimp pattern 16 (which varies from one design of box to another) which assists in creating a hermetic seal when the box bottom is welded. In the section shown in Fig. 10, the walls are shown before welding to show more clearly how the edge regions 9c, 9d overlap. The "gaps" would be closed by welding.

Figs. 4, 5 and 11-13 are similar perspective, plan and sectional views of the bottom of another prior art box having a so-called "J-fold". This J-fold is defined by a small flap 17 which is folded back after parallel slits are made in the edge portions 9d of the wall 9b. The flap 17 is tucked under the edge portion 9c of the wall 9b when closed, as shown in Fig. 5. Since the flap 17 forms a folded edge or J-fold 17c, it is this folded edge and not the raw edge 12 that is visible in the interior sectioned plan of Fig. 11. This "J" fold is made by folding back the flap 17 as can be seen in section YY of Fig. 13. The folded edge 17c is closer to the tips of the triangular regions 11 than shown in Fig. 11. The leading edge of the tab 17 is intentionally shown slightly protruding beyond the overlapping region 9c shown in Fig. 12 to facilitate description. When the overlap is welded, a U-shaped bulge 18 tends to be formed in the wall 9a due to the presence of the folded tab, as shown in Fig. 12. A pile or crimp pattern (not shown) may also be used to improve the integrity of the seal.

J-folds have been known for many years in the carton industry as a means of solving the "raw edge" problem. However, the industry has applied the flap 17 only to the lower edge areas (9d) of the overlap and this design is susceptible to the "orientation" problem described above, which creates the need for RH and LH cartons because a common carton blank cannot be used to serve (e.g.) a twin track system. Various previous attempts to solve this problem have not been successful.

A box bottom according to the preferred embodiment of the invention is shown in Figs. 6, 7 and 14-22.

As shown in Fig. 6, the tabs 17a, 17b are provided in both edge regions 9c, 9d of the walls 9a, 9b. These tabs 17a, 17b are formed by making substantially corresponding pairs of parallel slots in the edge regions 9c, 9d. For the purpose of explanation, these tabs are shown in Fig. 6 as being bent outwardly from corresponding folds 17c which run parallel to the edges of the walls 9a, 9b.

In the closed condition shown in Fig. 7, one of the flaps 17a is folded back and the other flap 17b covers the folded flap 17a so that their inner surfaces are brought into contact with each other when the edge regions 9c, 9d are overlapped. In the box orientation shown in Fig. 7, the folded flap 17a is in the underlying edge region of the wall 9b. The unfolded flap 17b in the edge region of the wall 9a merely covers the flap 17a. The box bottom is then welded to create a hermetic seal.

While the tabs 17 may have corresponding shapes and dimensions, it is preferred to make one tab slightly smaller than the other to improve the seal around the raw edges of the tabs. In this case, one tab slightly overlaps the other so that when heat is applied, the plastic coating melts and runs over the edges of the smaller tab and onto the overlapping remainder of the larger tab. Figure 22 shows the relative shapes of the larger tab 17a and a smaller tab 17b (behind the larger tab and shown in dashed lines). The side edges of the tab 17a are spaced from the side edges of the tab 17b by narrow edge regions 20; the length of the slots 21 in each edge region 9c, 9d is the same. When one or the other flap 17a, 17b is folded, its upper edge will retract from the upper edge of the unfolded flap.

Fig. 23 shows embossed stake marks 25, 26 on the bottom of the box to ensure that possible leak paths are interrupted. These stake marks are made by conventional machines known in the art.

Although one tab is preferably larger than the other, it is not large enough to prevent its passage through the smaller cut of the smaller tab when folded over the smaller tab, rather than in the other direction. A typical "overlap" between larger and smaller tabs would leave a margin of approximately 0.5-1.0 mm around each side edge. Rectangular tabs are preferred, but they may be square or other shaped (e.g. trapezoidal).

Fig. 14-17 show different views of a box bottom with the tabs 17a, 17b folded in one direction (e.g. to accommodate a box with a shape of LH or RH orientation). Fig. 18-21 show different views of the same box bottom with tabs 17a, 17b folded in the opposite direction.

Fig. 14 is a plan view looking downwardly inside the box and showing the flap sides 9a, 9b and triangular regions 11 formed by the inwardly folded sides 10a, 10b. The fold 17c is above the center line bisecting the tips of the triangular regions 11. The edge region 9c of the wall 9a is above the edge region 9d of the side 9b (noting also the position of the overlap 23 used in forming the blank into a sleeve) as shown in the bottom view of Fig. 15. The sections along lines AA and BB, respectively, in Figs. 16 and 17 show the relative positions of the flaps 17a, 17b and the overlapping walls 9a, 9b. The side areas of these flaps are sealed against the triangular area 11, as can be seen from Fig. 14. The leading edge area 17d of the larger (upper) flap 17a also overlaps the raw edge 17e of the smaller (lower) flap 17b. This has been exaggerated for clarity. Since the cardboard is deformable, the flaps 17a, 17b (shown in Fig. 16) conceal the overlapping edge areas 9c, 9d, which can be seen from Fig. 17.

Fig. 18-22 are similar to those in Fig. 14-17, except that the small flap 17b has been folded over the larger flap 17a and the edge area 9d of the side 9b covers the edge area 9c of the flap 9a. The box bottom is also rotated 180º (see position of the overlap 23).

As the box blank is fed through the machine to form the box, in the state where the box bottom is being formed, one or other of the flaps 17a, 17b is bent back to form a fold, while the other flap is then inserted over the folded flap prior to sealing. The manner in which the flaps are folded may vary to suit different machines.

A box according to an embodiment of the invention can be made from a common appearance of the blank because the box bottom can arrive at a work station in either a forward or reverse orientation and one of the flaps 17a, 17b can be folded before the various sections are welded.

Claims (8)

1. A box formed from a blank, which blank is formed into a sleeve (2) having respective walls formed into a box top and a box bottom (8), the box bottom (8) being formed by opposing flat walls (9a, 9b) and opposing inwardly folded walls (11), the folded walls (11) enabling the flat walls (9a, 9b) to be folded onto one another so that an edge region of one flat wall (9b) overlaps the corresponding edge region of the other flat wall (9a), regions of the walls comprising the overlapping edge regions being able to be welded together to hermetically seal the box bottom, characterized in that slots (21) are made at substantially corresponding positions in the edge regions of both opposing flat walls (9a, 9b) to accommodate respective tabs (17a, 17b); wherein the tabs (17a, 17b) are arranged such that when the edge regions are made to overlap, any one of the tabs (17a, 17b) is folded downwards and the other tab (17b or 17a) covers the folded tab (17a or 17b); and wherein the tab to be folded downwards is selected taking into account the intended orientation of the box prior to sealing the box bottom (8) and forming the folded edge (17c) on the inside of the box extending between the folded walls (11). 2. A box according to claim 1, wherein the tabs (17a, 17b) have identical shapes and dimensions. 3. A carton according to claim 1, wherein one of the tabs (17a, 17b) is slightly smaller than the other so that at least opposite side edge regions of the smaller tab are spaced inwardly from the side edge regions of the larger tab. 4. A method for producing a box (1) comprising the steps: (a) Making a blank from a flat material, (b) forming the blank into a cuff (2), (c) forming one end of the sleeve (2) with opposing flat walls (9a, 9b) and opposing inwardly folded walls (11) into a box bottom (8), the folded walls (11) allowing the flat walls (9a, 9b) to be pushed towards each other fold so that one edge area of one flat wall overlaps the corresponding edge area of the other flat wall, (d) welding the overlapping edge areas together to hermetically seal the box base (8), characterized by making slots (21) in the edge regions of the two flat walls (9b, 9b) so as to define the flaps (17a, 17b), causing the edge regions to overlap after folding either one or the other of the flaps (17a, 17b) under the other flap (17b, 17a) prior to welding which welds the box bottom (8) such that a folded edge (17c) extends on the inside of the box between the folded walls (11). 5. A method according to claim 4, wherein any one of the tabs is folded over approximately 180° to underlie the other tab. 6. A method according to claim 4, wherein prior to welding the box bottom, any of the tabs forms a fold and the other tab is inserted above the folded tab. 7. A method according to any one of claims 4-6, using a twin web machine for forming, filling and sealing boxes and wherein the machine is supplied with box sleeves held in a common design which are thereafter formed into boxes according to claim 1. 8. A cardboard formed box blank which is cut and folded to form a box (1) according to claim 1, 2 or 3, the blank having walls for forming four side walls of the box and an overlapping connecting flap, a box top and a box bottom (8), the box bottom (8) being formed from two folded walls (11) and two flat walls (9a, 9b) foldably connected to bottom edges of respective side walls, characterized in that each of the two flat walls (9a, 9b) has spaced slots (21) formed in respective positions in edge regions thereof to define respective flaps (17a, 17b) in the flat walls (9a, 9b), which flaps (17a, 17b) are further defined by fold lines (17c), which connect the tabs to their corresponding flat wall edge regions, whereby in the box formed from the blank, any one of the flat walls (9a, 9b) can form the inner wall of the box bottom, which will be folded back outwards with its respective tab (17a or 17b) to define a folded edge (17c) extending inside the box between the folded walls, and the other tab (17a or 17b) will cover the folded back tab (17a or 17b).