GB2264286A - End closure of cartons - Google Patents

Abstract

The end closure flaps (22, 24, 26, 28) of a rectangular carton body (20) are adhesively secured in a closure position by means of first lines (33) of adhesive material applied to at least the outermost closure flap (24) adjacent to opposed free edges thereof, preferably during manufacture of a flat blank whilst the blank is advanced in a direction longitudinally relative to said lines, and by means of a second line (34) of adhesive material applied to at least the outermost closure flap (24) so as to extend substantially across the entire width thereof in a second direction transverse to said first direction, preferably whilst the carton is advanced in a direction (B) longitudinally relative to said second line during an end-flap-closing operation, such that after closure a seal is formed to extend continuously around the free edges of the outermost closure flap (24). <IMAGE>

Description

TITLE: "End Closure of Cartons' Description of the invention This invention concerns the end closure of cartons and more particularly relates to an end closure for a carton of the kind comprising a pair of opposed first wall panels connected by a pair of opposed second wall panels to form a body of rectangular shape in transverse cross-section, wherein the end closure is formed by pairs of first and second closure flaps foldably and integrally connected along one edge ("the fold edge") thereof to said pairs of first and second wall panels respectively, the remaining edges of said closure flaps comprising free edges, and wherein one of said first closure flaps is disposed outermost relative to the remaining closure flaps. Such cartons are hereinafter for convenience referred to as being of the kind specified.

The end closure arrangement in a carton of the kind specified is particularly simple to manufacture, and economical of material, but there are serious practical difficulties in ensuring that such an end closure is effectively sealed so as to prevent leakage of the carton contents, particularly where such contents are in the nature of a powder. The problem of "sifting", as it is known, has given rise to many attempts to design improved end closures, often of quite complex design, and often making use of partial or complete internal liners or external wrapping. However, all such approaches have one or more drawbacks, particularly increased cost of manufacture relative to the basic design of cartons of the kind specified.

Accordingly, it is an object of the present invention to provide an improved end closure for a carton of the kind specified, and in particular to provide a design which can be manufactured economically and yet offer a secure seal which is effective to combat sifting.

With this object in view, the present invention firstly provides a carton of the kind specified wherein said end closure is sealed in a manner such as to prevent leakage of the contents of the carton by means of a first adhesive bond which extends continuously along the entire length of each of the second closure flaps and acts between a marginal portion of each second closure flap adjacent to its fold edge and a corresponding marginal free edge of those of the remaining closure flaps which overlie said marginal portion of the respective second closure flap, and a second adhesive bond which extends continuously along the entire length of the outermost closure flap between opposed free edges thereof and acts between said outermost closure flap and the other of said first closure flaps.

Preferably the adhesive bonds are each formed by means of a thermoplastic adhesive, or hot-seal adhesive, which softens when heated and spreads under pressure. The adhesive material for said first bond may be applied to marginal portions of the outermost closure flap adjacent to lateral free edges thereof, whilst the adhesive material for said second bond may be applied to said outermost closure flap along a line extending between said marginal portions.

In accordance with a particularly preferred feature of the invention the adhesive material for one of said bonds is applied to a flat blank, from which the carton is subsequently assembled, during the manufacture of such flat blank, and the adhesive material for the other of said bonds is applied subsequently during a filling and sealing operation.

This feature of the invention is particularly applicable to cartons which are initially manufactured in a flat-folded and adhesively secured condition in which they are despatched to a user who subsequently erects the cartons prior to filling and sealing. Conventional filling and sealing machines are equipped to apply one or more lines or patches of suitable adhesive, including thermo-plastic adhesive materials, to selected portions of the end closure flaps. Generally, this is achieved by the application of adhesive from a stationary nozzle as the carton is moved past it. Thus, the adhesive can only be applied conveniently to the end closure flaps in the direction of travel.

However, during manufacture, the flat blanks normally travel in a direction in which the closure flaps move transversely relative to the direction in which they normally move during the filling and sealing operation, and accordingly it is easily possible during manufacture of the blank to apply adhesive material along a line transverse to that in which it is applied during the filling and sealing operation.

Generally, it is most convenient for the adhesive material for said first bond to be applied during the manufacture of the flat blank, and the adhesive material for the second adhesive bond to be applied during the filling and sealing operation, although the opposite sequence may be utilised if required, and indeed the material for both bonds may be applied either to the flat blank during the manufacturing stage, or to the erected carton during the filling and sealing operation where appropriate machinery is available for altering the direction of advancement of the blank or the carton, or where machinery is available for applying an appropriately shaped adhesive patch in a single operation.

The invention also resides in a flat blank for assembly into a carton of the kind specified having adhesive material applied thereto in first marginal areas which extend along substantially the entire length of the opposed free edges of each of said first closure flaps and/or in a second area which extend along substantially the entire length of the outermost closure flap between its opposed free edges.

The invention also resides in such a blank in a flat-folded and adhesively secured condition.

The invention further resides in a method of forming a sealed carton of the kind specified characterised by the steps of applying at least one line of adhesive during the manufacture of a carton-forming blank, to at least said outermost closure flap so as to extend in a first direction substantially entirely across said outermost closure flap forming said blank into a flat-folded and adhesively secured condition, erecting said carton to form an open ended body, applying at least one further line of adhesive material to at least said outermost closure flap so as to extend substantially entirely across same in a second direction transverse to said first direction, and thereafter closing the ends of the carton and sealing the end closures thus formed by means of said lines of adhesive material.

These and other features of the invention will now be described by way of example with reference to the accompanying drawings wherein: FIGURE 1 shows a flat blank for forming a first embodiment of carton in accordance with the invention; FIGURE 2 shows one end of an erected carton formed from the blank of Figure 1 after a first stage of an end closing operation; FIGURE 3 shows an end view of the carton of Figure 2 after a second stage of the closing operation; FIGURE 4 shows an end view thereof after completion of the closing operation; FIGURES 5 to 8 are views similar to Figures 1 to 4 respectively illustrating a second embodiment of carton in accordance with the invention; and FIGURES 9 to 11 are views similar to Figures 1, 3 and 4 illustrating a third embodiment of carton in accordance with the invention.

Referring firstly to Figure 1, a basic blank is shown for the construction of a simple rectangular carton. Except as hereinafter described, the blank 10 is entirely conventional and comprises a pair of first wall panels 12,14 to form opposed front and rear walls of the assembled carton, a pair of second wall panels 16,18 to form side walls, and a flap 19 whereby rear wall panel 12 may be secured to side wall panel 18 to form an open ended body 20 as illustrated in Figure 2.

The first wall panels 12 and 14 carry foldably and integrally thereto at their upper and lower edges respective first closure flaps 22 and 24, and likewise the second wall panels 16 and 18 carry respective second closure flaps 26 and 28.

The open end of the body 20 is closed using these closure flaps, in a three-stage operation as illustrated in Figures 2 to 4. Firstly, the second closure flaps 26 and 28 are folded inwardly into the plane of open end of the carton body 20 as illustrated in Figure 2. One of the first closure flaps, namely flap 22, is then folded inwardly onto the two flaps 26, 28 which are innermost, to form an intermediate part of the end closure, as illustrated in Figure 3. Finally, the remaining closure flap 24 is folded over onto the intermediate flap 22 to form the outermost part of the end closure, as illustrated in Figure 4.

The design of the blank and the folding operations thus far described are entirely conventional. However, in accordance with the invention as the blank 10 is advanced on a conventional folding and gluing machine in the direction of arrow A, lines of an appropriate thermo-plastic adhesive are applied to the first closure panels 22 and 24 in marginal areas immediately adjacent to, and extending substantially along the entire length of, the opposed free edges 23,25 thereof, as indicated by the areas 31,33.

Subsequently, the panel 12 is folded about the fold line 11 to bring it, and the flap 19 which has adhesive applied to the reverse face thereof, into faceto-face relationship with the panel 14, and the panel 18 is then folded about the line 15 to bring panel 18 into engagement with the adhesive coated face of the flap 19, in order to form a flat-folded and adhesively secured blank which may then be stacked with other similar blanks and transported to the user.

In order to ensure that the lines of adhesive 31, 33 applied to the blank 10 do not adhere to opposing flaps when brought into face-to-face relation therewith in the flat-folded condition, the adhesive should be formulated so as to set rapidly, and this may be assisted by cooling, for example by jets of cold air.

Additionally, or alternatively, those areas which come into register with, and may thus come into contact with, the adhesive material 31,33 after folding may be protected by a previously applied coating formulated to inhibit adhesion.

Alternatively, a two-component adhesive system may be used, wherein each component individually is substantially non-adhesive, one component being applied as indicated at 31,33 in figure 1, and the other component being applied to the corresponding areas of the blank (as hereinafter described) to which adhesion is required to seal the end closure.

On receipt by the user, the flat-folded blank is erected to form an open ended body 20 as illustrated in Figure 2. One end of the body is then closed prior to a filling operation, subsequent to which the remaining end of the body is closed, and Figures 2 to 4 illustrated the steps of the closing operation applicable to both ends of the body.

During this operation the carton is advanced in the direction of arrow B and before closure of the ends of the body further lines of adhesive material are applied to the closure flaps 22 and 24 as indicated at 32 and 34. As can be seen, the lines of adhesive 32 and 34 extend substantially along the entire length of the respective flaps 22 and 24. between their opposed free edges 23,25 respectively. In the illustrated embodiment, the line of adhesive 34 is disposed generally centrally along the length of the flap 22, whilst the line of adhesive 34 is disposed adjacent to the outermost free edge of the flap 24.

As can be seen from Figure 2, the closure flaps 26 and 28 carried by the side walls 16 and 18 are first folded inwardly, whilst the closure flaps 22 and 24 carried by the front and rear walls are folded outwardly. After application of the lines of adhesive material, the flap 22 is then folded inwardly so as to bring the lines of adhesive 31 into contact with marginal areas of the inner flaps 26 and 28 at positions immediately adjacent to the fold edges 27,29 thereof whereby they are carried by the side wall panels 16 and 18 respectively.The line of adhesive 32 also contacts the flaps 26 and 28 centrally and serves to increase the area of adhesive bonding between the inner flaps 26 and 28 and the intermediate flap 22, but since it does contribute to the formation of a seal which prevents the escape of the contents from the carton, in some cases, it may be omitted.

Finally, the outermost flap 24 is folded inwardly to bring the lines of adhesive 33 into contact with marginal portions of the outermost face of the intermediate flap 22 immediately adjacent to the opposed free edges 23 thereof, and to bring the line of adhesive 34 into contact with a marginal portion of the intermediate flap 22 adjacent to the fold edge 21 by which it is connected to wall panel 12.

Such a closure operation can be performed on the closure flaps at the end of the body which is to be the base of the carton immediately after the application of the adhesive. Normally it is difficult to form an effective seal at this stage because it is not possible to apply significant pressure to the closure flaps to cause them to adhere securely, but where a hot-melt adhesive is used sufficient adherence can be obtained to maintain the base of the carton closed during the filling operation.

After the filling operation, the remaining upper end of the carton is closed in a similar manner, but to create a good seal it is desirable to re-activate the adhesive, for example by the application of heat. Such heating can be applied to both the top and base of the carton and, since the carton has been filled, pressure can then be applied more effectively to both ends of the carton to effect a good seal by re-melting and spreading of all the lines of adhesive. Even when adhesives other than hot melt types are employed the application of pressure (and heat if appropriate) at both ends of the carton can significantly improve the effectiveness of the seal.

It can be seen that in this embodiment the adhesive 31 forms a seal between the outermost face of the inner flaps 26 and 28 and the innermost face of the intermediate flap 22 along the entire length of the fold edges 27,29 of the inner flaps 26 and 28 where they are carried by the side walls 16 and 18.

Likewise, the adhesive 33 forms a similar seal at the same edges between the outermost face of the intermediate flap 22 and the innermost face of the outermost flap 24. Thus, no material from the interior of the carton body can escape between the inner and intermediate flaps or between the intermediate and outer flaps at the ends of the side walls 16 and 18.

Similarly, because the outer free edge of the outermost flap 24 is effectively sealed along its entire length to the underlying intermediate flap by the adhesive 34, any material which escapes into the space between the intermediate and outermost flaps, by migrating around the free longitudinal edge of the intermediate flap 22, is trapped by the continuous seal which is formed around the free edges of the outermost flap 24 by the adhesive 31, 33.

Whilst the line of adhesive 33 is illustrated as being disposed adjacent to the outer free edge of the outermost closure flap 24, it will be appreciated that, providing it extends continuously between the end lines of adhesive 31, it can be disposed at any position between the fold edge of the flap 24 by which it is connected to wall panel 14 and the outer free edge thereof. It is nevertheless preferred to arrange the line of adhesive 33 at or adjacent to the outer free edge in order to reduce the risk of inadvertent separation of the outermost closure flap 24 from the intermediate closure flap 22 by insertion of an object inadvertently into the space which would otherwise be available between the outermost closure flap 24 and the intermediate closure flap 22.

In the embodiment illustrated in Figures 1 to 4, the intermediate and outermost closure flaps 22 and 24 are shown as extending across the full width of the end of the carton body, as measured between the front and rear walls 12 and 14. However, providing these two flaps overlap to a sufficient extent, neither need extend fully up to the opposing wall panel, since where the intermediate flap 22 does not overlie the inner flap, the outermost flap 24 will be adhesively secured directly to the inner flap.

It will be appreciated that in the above-described embodiment, it is necessary to apply lines of adhesive 31 and 33 to both the intermediate and outer flaps 22 and 24, giving rise to a double thickness of adhesive along the end edges of these flaps. Figures 5 to 8 illustrate a second embodiment of carton which is generally similar to that described above, except that such double layer of adhesive is eliminated, and adhesive material is applied only to the outermost closure flap. This is achieved by cutting away end portions of the intermediate closure flap as illustrated. In Figures 5 to 8 the same reference numerals as used in Figures 1 to 4 are employed to denote similar parts. As can be seen, the marginal areas of the closure flaps 22, which in the first embodiment are coated with adhesive 21, are instead in this embodiment cut away as indicated at 21a.

As a result, the intermediate flap 22 is not secured to the inner flaps 26 and 28 during the first and second stages of the closure operation as illustrated in Figures 6 and 7. However, because of the cut away end portions 21a of the intermediate flap 22, when the outermost closure flap 24 is folded inwardly as illustrated in Figure 8, the lines of adhesive 33 come into direct contact with the inner closure flaps 26 and 28 along the fold edges 27 29 thereof whereby they are connected to the side walls 16 and 18 respectively, whilst the line of adhesive 34 comes into contact, as previously described, with the intermediate flap 22; in this way the end closure is effectively sealed along all three free edges of the outermost closure member 24.

A further embodiment as illustrated in Figures 9 to 11 is designed for a different folding sequence, and again the same reference numerals are used to denote similar parts, and the following description will be confined to features of difference.

As can be seen, the closure flaps 2628 carried by the side walls 16,18 are of generally triangular form, and no adhesive material is applied to the closure flap 22 carried by wall panel 12.

During the closure operation, closure flap 22 is first folded inwardly as illustrated in Figure 10, followed by closures flaps 26a and 28a. The outermost closure flap 24 is finally folded inwardly to bring the lines of adhesive 33 into contact with the closure flaps 26a and 28a at positions adjacent to the fold lines 27,29 whereby they are connected to the side walls 16 and 18, and to bring the line of adhesive 34 into contact with the innermost flap 22 along the fold edge 21 whereby it is connected to the wall panel 12. In this case, also, the adhesive 33, 34 forms a continuous seal around the free edges of the outermost closure flap 24.

It is preferred to use a thermo-plastic adhesive firstly because such material can simply be re-activated by the application of heat when it is required to seal the end closure, and secondly because when heated the material becomes flowable and any slight imperfections in the line of adhesive applied to the blank will be eliminated as the heat-softened adhesive material flows under the application of pressure during the sealing operation. However, -other types of sealing material could be employed.

Whilst in the illustrated embodiments, the adhesive material is applied to the outermost closure flap 24 on the face thereof which is presented inwardly when the end closure is completed, it will be understood that alternatively the adhesive could be applied to the corresponding areas of the other flaps, for example to the outwardly presented face of the flaps 26,28 adjacent to the fold edges 27,29 in the embodiment of Figures 5 to 8 instead of as shown at 33 and/or to the outwardly presented face of the intermediate flap 22 adjacent to the fold edge 21 instead of as indicated at 34.

In the embodiments described and illustrated above, the carton is shown in a simple, basic design and it will be appreciated that the design may be varied in many ways. In particular, the carton may be provided with some form of openable dispenser, such as a tear-open portion which may extend over adjacent parts of the top closure and one of the side walls. In such a case it may be necessary or desirable to adjust the position of the lines of adhesive in the region of such dispenser portion and/or provide additional lines of adhesive in such region.

Claims (14)

CLAIMS:

1. A carton of the kind specified wherein said end closure is sealed in a manner such as to prevent leakage of the contents of the carton by means of a first adhesive bond which extends continuously along the entire length of each of the second closure flaps and acts between a marginal portion of each second closure flap adjacent to its fold edge and a corresponding marginal free edge of those of the remaining closure flaps which overlie said marginal portion of the respective second closure flap, and a second adhesive bond which extends continuously along the entire length of the outermost closure flap between opposed free edges thereof and acts between said outermost closure flap and the other of said first closure flaps.

2. A carton according to Claim 1 wherein the adhesive bonds are each formed by means of a thermo-plastic adhesive, or hot-seal adhesive, which softens when heated and spreads under pressure.

3. A carton according to Claim 1 or Claim 2 wherein the adhesive material for said first bond is applied to marginal portions of the outermost closure flap adjacent to lateral free edges thereof, whilst the adhesive material for said second bond is applied to said outermost closure flap along a line extending between said marginal portions.

4. A carton according to any one of the preceding claims wherein the adhesive material for one of said bonds is applied to a flat blank, from which the carton is subsequently assembled, during the manufacture of such flat blank, and the adhesive material for the other of said bonds is applied subsequently during a filling and sealing operation.

5. A flat blank for assembly into a carton of the kind specified having adhesive material applied thereto in first marginal areas which extend along substantially the entire length of the opposed free edges of each of said first closure flaps and/or in a second area which extend along substantially the entire length of the outermost closure flap between its opposed free edges.

6. A blank according to Claim 5 and in a flat-folded and adhesively secured condition.

7. A method of forming a sealed carton of the kind specified characterised by the steps of applying at least one line of adhesive during the manufacture of a carton-forming blank, to at least said outermost closure flap so as to extend in a first direction substantially entirely across said outermost closure flap, forming said blank into a flat-folded and adhesively secured condition, erecting said carton to form an open ended body, applying at least one further line of adhesive material to at least said outermost closure flap so as to extend substantially entirely across same in a second direction transverse to said first direction, and thereafter closing the ends of the carton and sealing the end closures thus formed by means of said lines of adhesive material.

8. A carton-forming blank substantially as hereinbefore described with reference to and as shown in Figure 1 of the accompanying drawings.

9. A carton-forming blank substantially as hereinbefore described with reference to and as shown in Figure 5 of the accompanying drawings.

10. A carton-forming blank substantially as hereinbefore described with reference to and as shown in Figure 9 of the accompanying drawings.

11. A flat-folded and adhesively secured blank formed from a blank according to any one of Claims 8 to 10.

12. A method of closing the end of a carton of the kind specified substantially as hereinbefore described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.

13. A method of closing the end of a carton of the kind specified substantially as hereinbefore described with reference to and as shown in Figures 6 and 7 of the accompanying drawings.

14. A method of closing the end of a carton of the kind specified substantially as hereinbefore described with reference to and as shown in Figures 10 and 11 of the accompanying drawings.