GB2328201A - Carton with locking tear-open flap - Google Patents

Abstract

A carton for flowable material, such as rice, has a hinged tear-open closure flap 16 with a hinged lift-tab 10 which can be inserted into a dispensing aperture 20 of the carton so that the closure flap can reseal the aperture after use. In this condition, a locking tongue 21 projecting from an edge of the aperture projects into an opening formed by a cut line 13 in the lift-tab and engages behind the closure flap 16 to prevent accidental spillage if the carton is knocked over. The lift-tab cut line defines a reopening tab 19 which projects from the closure flap and can be grasped by a user for repeated opening and closing of the closure flap. Additional cut lines 22 are formed either side of the locking tongue to facilitate repeated usage, and may converge towards the projecting end of the locking tongue which may be provided with a transverse bending line. The carton may also have at least one inspection window (7, fig 4). The lift-tab 10 may initially be secured to a side wall 6 of the carton solely by tear-lines (11, fig 1). Alternatively, varnish may be used to reduce the adhesion of glue applied between the lift-tab and the side wall.

Description

CARTON FOR FLOWABLE MATERIAL This invention relates to a carton for flowable material, for example rice, flour or sugar, with a resealable tear-open closure flap. In this specification, the term "carton is used as a generic term that embraces boxes, containers, packets and the like.

Such cartons are well known in the art and many designs are in common usage. According to one such design, the closure flap has a hinged lift-tab which, for resealing the carton after flowable material has been dispensed from it, is inserted into the pour opening of the carton alongside one side edge thereof and forms a tight interference fit with opposite -side edges of the opening adjacent the firstmentioned side edge. If the carton is accidentally knocked over or turned upside down, reliance is placed on the tightness of the interference fit to prevent the weight of flowable material in the carton from opening the closure flap, but avoiding spillage cannot be guaranteed.

A solution to this problem is disclosed in US Patent 3 971 506 which discloses a cardboard carton having a tearopen closure flap in its top wall. A locking projection projecting from an edge of the pour opening enters a cut out formed in a lift-tab hingedly connected to the closure flap as the latter is closed and engages behind the closure flap.

This locking arrangement is effective for avoiding accidental spillage. However, the locking projection, which is an integral part of a cardboard inner flap of the carton defining the aforesaid edge of the pour opening, projects only a short distance from that edge but is relatively wide in the region of its root, the side edges (which are curved) of the locking projection sharply converging along its length to meet at the remote end of the projection. As a result of its geometry, the locking projection is of relatively high stiffness or reluctance to flex. This gives rise to a number of difficulties. Firstly, the locking projection causes the lift-tab to bend inwardly to a more significant extent about its hinged connection as it is inserted into the pour opening, until the locking projection can enter into the cut-out. This makes the carton less convenient to use. Furthermore, any slight inaccuracy in alignment of the carton flaps and panels during assembly can adversely affect the correct operation of the closure flap locking arrangement. This is particularly the case where, as in US patent 3 971 506, the closure flap and its locking arrangement are provided in the top wall of the carton, which is the last one to be assembled after the carton is charged with flowable material during packaging.

Thirdly, owing to the relative stiffness of the locking projection, there is a risk of the user applying additional force when resealing the carton which could bend the locking projection inwardly or crease it such that it can no longer function as intended. Making the locking projection much narrower in its root region would improve its ability to flex but also increase the likelihood of causing it to bend or crease. In addition, the so-called cutting rule which would be used for cutting the locking projection when forming the carton blank and which would be correspondingly shaped, would then not have enough strength to withstand the applied pressures during cutting, due to the short dimensions of the side edges of the locking projection.

According to the invention there is provided on carton for flowable material, comprising a tear-open closure flap which closes an aperture in the carton in an initial unopened position, exposes said aperture in an open position to allow said material to be poured through said aperture, and is arranged for re-openably closing the aperture in a closed position, said tear-open closure flap being hingedly attached at a near end to the carton and having a lift-tab hingedly attached to the closure flap at its remote end to enable the closure flap to be torn open initially and to be subsequently inserted into the aperture for re-closing the carton, said closure flap having a projecting re-open tab at its remote end defined as a cut-out from the lift-tab and said carton having a locking-tongue projecting from an edge of the aperture so that when the lift-tab is inserted into the aperture to reclose the carton, the locking tongue passes into the cut-out in the lift-tab and engages behind the closure flap, there being cut lines in the carton forming respective extensions of the projecting side edges of the locking tongue so that the effective length (X) of the locking tongue is greater than the amount (Y) by which the locking tongue projects from said edge of the aperture.

Owing to the greater effective length of the locking tongue, it can be accorded a given degree of flexibility even though the distance by which it projects from the edge of the aperture is relatively small. Furthermore, this enhanced resilience minimises of the risk of the locking tongue being bent or creased due to excessive force being applied by the user. In addition, slight misalignment of the carton flaps and panels during assembly is unlikely to affect the correct operation of the locking arrangement due to the resilience of the locking tongue. This is particularly the case where the pour opening is provided in an end wall of the carton because that end wall is formed before the top and bottom walls are formed and the carton-filled with flowable material, and the assembly process for gluing the end wall can generally be achieved with greater accuracy than the subsequent top and bottom wall gluing process. Still further, due to the use of the cut lines extending the side edges of the locking tongue, the required cutting rule shape will not compromise its ability to withstand the cutting pressure.

Preferably, the projecting side edges of the locking tongue converge slightly in the direction towards the projecting end of said tongue. In this way, insertion of the locking tongue into the cut-out in the lift-tab is facilitated.

In one arrangement, the locking tongue is connected to the carton by a transverse bending line, affording limited hinged articulation of the locking tongue. With this arrangement, a given degree of flexure of the locking tongue can be provided without lines of shorter-length extending the side edges of the locking tongue.

Suitably, the width of the locking tongue at the location where it passes through the cut-out in the lift tab in the closed position of the closure flap is substantially the same as the corresponding dimension of the cut-out. This helps to ensure a positive locking action. In addition, the lift-tab may have a width substantially the same as the corresponding dimension of said edge of said aperture. This helps to guarantee correct alignment between the locking projection and the cut-out in the lift-tab.

In a preferred embodiment, the lift-tab is secured to the carton, before it is opened initially, solely along weakening lines. Alternatively, the lift-tab is secured to the carton, before it is opened initially along weakening lines and an area of an inner end flap of the carton, underlying the lifttab, is covered with a varnish so as to minimise the adhesion of a glue, applied along the length of said flap to bond in overlapping relationship the flap and an end wall of the carton in which the closure flap, lift-tab and re-open tab are provided, -to said area of said inner end flap. In both cases, the effort required by the user to raise the lift-tab for tearing open the closure flap is minimised.

According to a preferred arrangement, at least one window is formed in an end wall of the carton and a translucent sheet extending across the window is secured to the inside surface of said end wall. In this way, a visual indication be provided of the quantity of flowable material remaining in the carton when the level falls below the top of the (uppermost) window. Two windows may be formed in said end wall of the carton, one being located close to a bottom wall of the carton and the other being located between said one window and a top wall of the carton.

The invention also provides a carton blank that is stamped to provide weakening and cut lines to enable it to be assembled into the carton described above. Suitably, the closure flap, lift tab and re-open tab are provided in one end wall and the locking tongue is provided in an end flap, which is to be glued to the inside surface of the end wall in which the closure flap, lift tab and re-open tab are provided for assembling the carton.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a perspective view of an upper corner of a carton for flowable material showing a tear-open closure flap in its initial, unopened, position; Figure 2 is a corresponding view showing the closure flap in an open position revealing an aperture through which the flowable material may be poured; Figure 3 is a corresponding view showing the closure flap just prior to locating it in its closed position in which it re-openably closes the aperture; Figure 4 is a view of a carton blank ready to assembled into a finished carton; Figure 5 is a detail of the carton at the location of the tear-open closure flap; Figure 6 is a detailed view of a locking tongue used for securing the closure flap in its closed position; and Figure 7 is a corresponding view of a modified arrangement for the locking tongue.

Referring to Figure 1, there is shown an upper corner of a carton for flowable material such as rice, flour, sugar, or the like, showing a tear-open closure flap 16, near the top of an end wall 5 of the carton, in its initial unopened position in which the flowable material is contained within the carton.

This Figure shows the carton in the condition in which it is purchased, initially.

Referring now to Figure 4, there is shown a carton blank of sheet material such as cardboard, which is to be erected and glued to form the carton shown in Figure 1. The blank has the configuration shown and is formed with a number of weakening lines and bend lines that are to be described in detail below. The weakening lines typically take the form of continuous cuts which pass through only part of the thickness of the sheet material, such as cardboard, or which take the form of perforations. In either case, pressure applied in the vicinity of the weakening lines will cause the sheet to sever along the weakening lines. The bend lines are merely lines formed by indentation or the like such that the sheet-like areas on opposite sides of the bend lines are hingedly connected to one another for pivoting about the bend line.

The carton blank is formed with a number of bend lines (not specifically referenced) which define first and second side walls 2, 3, end walls 4, 5, an inner end flap 6, and top flaps 2a, 3a, 4a, 5a and bottom flaps 2b, 3b, 4b, 5b, respectively connected to the upper and lower edges of the side walls 2, 3 and end walls 4, 5. In order to form the carton blank into a generally rectangular carton, the carton is folded through 900 along the four bend lines separating the inner end flap 6, side wall 2, end wall 4, side wall 3 and end wall 5 with the end wall 5 overlapping and being adhesively secured by glue to the inner end flap 6. Typically, these steps are performed by the carton manufacturer. Then, the top and bottom flaps 4a, 5a and 4b, 5b are bent inwardly, followed by the top flaps 2a, 3a and bottom flaps 2b, 3b, and at least the overlapping top flaps 2a, 3a secured together adhesively and correspondingly for the bottom flaps 2b, 3b. Normally, these latter steps are performed by the packager of the flowable material.

Formed in the end wall 4 are two vertically aligned cutouts 7, one arranged in a central location and the other arranged in a bottom location, and a transparent sheet 8 of C Perspex or similar material is secured adhesively, such as by a glue bead, to the inner surface of the end wall 4 so as to extend across both cut-outs. In this way, a pair of windows is provided in the end wall 4 to give a visual indication of the amount of flowable material remaining in the carton as the level falls below the top of the upper window 7.

As best shown in Figure 5, the end wall 5 is formed in its outer surface with upper and lower convex weakening lines 14, upper and lower horizontal weakening lines 11 and upper and lower vertical weakening lines 15 each connecting the adjacent ends of the associated convex and horizontal weakening lines 14, 11. In addition, upper and lower convex weakening lines 18 that are offset inwardly from the convex weakening lines 14 by a distance corresponding to the length of the vertical weakening lines 15 are formed in the inside surface of the carton blank.

Figure 5 also shows that upper and lower vertical bending lines 12 are formed in the blank in alignment with, and inwardly of, the vertical weakening lines 15. A semicircular (or other appropriately shaped) cut-out line 13 connects the inner ends of the two bend lines 12.

The weakening lines 14, 18 and 15 take the form of continuous cuts extending through part only of the thickness of the sheet material, whereas the weakening lines 11 can be either continuous partial cuts or perforations. The weakening lines 14 (and 18), 15 and 11 together with the cut line 13 and the bend line 17 along which the side wall 3 and end wall 5 are hingedly connected serve together to define a closure flap 16 hingedly connected to the side wall 3, a re-open tab 19 forming a projection at the remote edge of the closure flap 16, and a lift-tab 10 hingedly connected to the closure flap remote edge.

As shown in Figure 6, the carton blank has a locking tongue 21 formed in the sheet material as a projection from the far edge of the inner end flap 6. Cut lines 22 formed in the carton blank serve as respective extensions of the projecting side edges of the locking tongue. By forming the locking tongue in this way, the effective length of the locking tongue 21 is greater than the amount by which the locking tongue projects from the far edge of the end flap 6.

As is clearly shown in Figure 6, the projecting side edges of the locking tongue converge slightly in a direction towards its projecting end. The width of the projecting end of the tongue is slightly less than the corresponding largest width (diameter) of the opening defined in the lift-tab 10 by the semicircular cut-out line 13 when the lift-tab 10 is hinged out of the plane of the closure flap 16, to facilitate insertion of the locking tongue into the semicircular opening.

The locking tongue is located such that, when the end wall 5 and inner end flap are glued together in overlapping relationship, the locking tongue is located centrally, immediately behind the re-open open tab 19. Preferably, glue unites the outer surface of the end flap 6 and the inner surface of the end wall 5 along their lengths, except in the region immediately beneath the lift-tab 10 and re-open tab 19.

Therefore and with reference to Figure 1, all that holds the lift-tab 10 in place is a connection provided through the weakening lines 11 to the adjacent areas of the end wall 5.

With this arrangement, the advantage is achieved that the user effort required to separate the lift-tab 10 from the inner end flap 6 is simply that required to break the connections provided by the weakening lines 11. This effort can be made to be less than would be needed if the lift-tab 10 were to be glued to the inner end flap 6. In addition, the risk of tearing or otherwise damaging the lift-tab 10 and re-open tab 19, by inadvertently applying excessive effort is reduced.

According to a modification, during the manufacture of the carton, a film of varnish is applied to the region of the inner flap 6 immediately beneath the lift-tab 10 and re-open tab 19 and then glue is applied along the entire length of the inner end flap, before the end wall 5 is applied to the inner end flap 6 in overlapping relationship. In this way, the carton manufacturing process can be simplified. Since the varnish film is chosen so as to reduce the adhesion of the glue, a weak bond is formed between the glue and varnish and the lift-tab 10 is held in position, in the initial unopened condition of the carton, principally by the connections to the surrounding sheet material of the end wall 5 provided by the weakening lines 11. The same result can also be obtained by applying the varnish film instead to the underside of the lift-tab 10 before the glue is applied along the whole length of the inner end flap, during assembly of the carton.

As shown in Figures 1 and 2, the far edge of the lifttab 10 preferably extends fractionally beyond the corner edge between the end wall 5 and the side wall 2. This is to facilitate the start of the tearing action by the user to open the closure flap 16 on first use.

The manner in which the carton is to be used will now be described. Initially, when the user starts pulling on the lift-tab 10 to open the carton for the first time, it separates from the end wall 5 along the weakening lines 11 while pivoting about the bend line 12. Due to the cut line 13 extending through the thickness of the sheet material, the reopen tab 19 remains in the plane of the end flap 16, and therefore in the plane of the end wall 5. In the modification where a film of varnish is applied to the region of the inner flap immediately beneath the lift-tab 10 and re-open tab 19 before the glue is applied, the glue will remain adhered to the underside of the lift-tab 10 but will separate from the underlying inner flap 6 with minimal effort as the lift-tab is pulled back, owing to the varnished film.

Now that the lift-tab 10 has been bent back, it can be gripped more firmly by the user who, on applying increased pulling effort will cause the sheet material to tear between the outer and inner, outwardly curved, weakening lines 14, 18 at the top and bottom of the closure flap 16 and separate in a plane located at roughly half the thickness of the sheet material. The outer thickness of the sheet material between the outer-and inner curved weakening lines 14, 18 forms outer marginal areas 24 of the closure flap while the remaining, inner, thickness forms inner marginal areas 25 of end wall 5, as best shown in Figure 2. As a result, the closure flap 16 separates from the end wall 5 to reveal a pour opening 20 in the carton end wall 5 whose shape and size are determined by the upper and lower inner curved weakening lines 18, the bend line 17 about which the closure flap 16 pivots and the far edge of the inner end flap 6. The concave lower edge of the aperture 30 resulting from separation along the lower weakening line 18 enables the user to have better control over the pouring of flowable material from the carton. Figure 2 shows the end flap hinged to one side to reveal the opening 20, through which flowable material in the carton may then be poured by tipping the carton forwardly.

In order to close the carton again after use, the closure flap 16 is pushed back, pivoting about its bend line 17, and the lift-tab 10 is also pivoted back about its bend line 12 so that its remote end can be inserted into the aperture 20, pressing against the projecting end of the locking tongue 21.

This condition is depicted in Figure 3. As the user pushes the closure flap 16 back into its fully closed position in which it is substantially in the plane of the end wall 5, the reopen tab 19 comes into abutment with the locking tongue 21 and the locking tongue enters into the semicircular opening defined by the cut line 13 and engages behind the closure flap 16 adjacent the re-open tab 19. It is to be noted that the width of the lift-tab 10 is preferably substantially the same as the corresponding dimension of the aperture, in order to ensure-correct alignment between the locking projection 21 and the cut out (13) in the lift-tab 10. Due to some resilience in the hinged connection between lift-tab 10 and the closure flap 16, the lift tab 10 will tend to spring back to some degree thereby ensuring adequate projection of the locking tongue 21 into the semi-circular opening in the lifttab 10 and positive securement of the closure flap 16 in its closed position.

Any tendency due to continued pressure applied by the user to force the closure flap 16 inside the aperture is resisted by the overlap between the top and bottom marginal edges of the closure flap and the edge regions of the end wall 5 adjacent the top and bottom edges of the aperture 20.

Additional support is provided by the re-open flap 19 pressing against the locking tongue 21 and the adjacent regions of the end flap 6.

If the user should accidentally knock the carton over or turn it upside down when the carton is in its resealed condition, the weight of the flowable material in the carton will tend to bend the lift-tab 10 against the inner surface of the end flap. Furthermore, the engagement of the locking tongue 21 behind the closure flap 16 will tend to act increasingly positively as the weight of flowable material tends to push the closure flap 16 open. By adopting these measures, the unwanted escape of materials from the carton through the aperture when the carton is accidentally knocked over or inverted can be avoided.

The described arrangement for locking the closure flap 16 in place is found to work positively and reliably throughout the expected working life of the carton, which typically involves re-openably resealing the carton some six to ten times before all the flowable material has been dispensed.

The reliable positive locking action is attributable to a significant extent to an appropriate degree of resilience of the locking tongue 21. That is, it must not be too flexible, because then it might be deflected back or bent back to such a degree, as the lift-tab 10 is inserted into the opening 20, that even when the closure flap 16 is in its fully closed position substantially in the plane of the end wall 5 the locking tongue is unable to enter into the semi-circular opening in the lift-tab 10. On other hand, the locking tongue 21 should not be too stiff, because more pressure would then be required to close the closure flap sufficiently for the locking tongue to be able to enter the semi-circular opening in the lift-tab 10. Furthermore, if the locking tongue is too stiff, there is potentially a risk of bending or creasing the locking tongue due to the application of excessive pressure, resulting in the locking tongue no longer being able to perform its locking function.

The required degree of resilience is obtained due to the provision of the cut lines 22, which determine the effective length X of the locking tongue 21 from its root to its projecting edge. Even though the locking tongue projects only a short distance Y beyond the edge of the inner end flap 6 and aperture 20, it exhibits a degree of resilience determined by its effective length X. By careful choice of the length X at the design stage such as by trial and error, taking account also of factors such as the thickness of the sheet material and its resilience, the locking tongue can be given a desired resilience that is neither too weak nor too strong, as discussed above. Therefore, the locking arrangement can be made to have a positive and reliable locking action.

There is the further advantage that, from a carton manufacturing standpoint, it is perfectly practical to form the projecting tongue with a corresponding shaped (U-shaped) cutting rule without compromising the ability of the cutting rule to sustain the necessary cutting pressure. If the cut lines 22 were not provided, the required U-shaped cutting rule would not be strong enough to withstand the cutting pressure because the side limits of the U would be too short.

According to the modification shown in Figure 7, the locking tongue 21 may be formed with a transverse bend line 23 at its root. This bend line affords a limited degree of hinged movement of the locking tongue relative to the inner end flap 6 which, coupled with the resilience of the locking tongue itself, provides the required degree of flexure of the projecting end of the locking tongue. Owing to the bend line 23, the effective length of the locking tongue will be shorter, for any given degree of flexure of its remote end, than for the locking tongue when without such a bend line.

However, the cut lines 22 will still need to be long enough that the necessary U-shaped cutting rule has enough cutting strength to sustain the cutting pressure.

Claims (13)

1. A carton for flowable material, comprising a tear-open closure flap (16) which closes an aperture (20) in the carton in an initial unopened position, exposes said aperture (20) in an open position to allow said material to be poured through said aperture, and is arranged for re-openably closing the aperture in a closed position, said tear-open closure flap (16) being hingedly attached at a near end to the carton and having a lift-tab (10) hingedly attached to the closure flap (16) at its remote end to enable the closure flap to be torn open initially and to be subsequently inserted into the aperture (20) for re-closing the carton, said closure flap (16) having a projecting re-open tab (19) at its remote end defined as a cut-out (13) from the lift-tab (10) and said carton having a locking tongue (21) projecting from an edge of the aperture (20) so that when the lift-tab (10) is inserted into the aperture to re-close the carton, the locking tongue (21) passes into the cut-out (13) in the lift-tab (10) and engages behind the closure flap (16), there being cut lines (22) in the carton forming respective extensions of the projecting side edges of the locking tongue (21) so that the effective length (X) of the locking tongue (21) is greater than the amount (Y) by which the locking tongue projects from said edge of the aperture (20).

2. A carton according to claim 1, wherein the projecting side edges of the locking tongue (21) converge slightly in the direction towards the projecting end of said tongue.

3. A carton according to claim 1 or 2, wherein the locking tongue (21) is connected to the carton by a transverse bending line (23), affording limited hinged articulation of the locking tongue (21).

4. A carton according to any preceding claim, wherein the width of the locking tongue at the location where it passes through the cut-out (13) in the lift tab in the closed position 6f the closure flap (16) is substantially the same as the corresponding dimension of the cut-out (13).

5. A carton according to any preceding claim, wherein the lift tab (10) has a width substantially the same as the corresponding dimension of said edge of said aperture (20).

6. A carton according to any preceding claim, wherein the lift tab (10) is secured to the carton before it is opened initially, solely along weakening lines (11).

7. A carton according to any one of claims 1 to 5, wherein the lift-tab (10) is secured to the carton, before it is opened initially, along weakening lines and an area of an inner end flap (6) of the carton, underlying the lift-tab (10), is covered with a varnish so as to minimise the adhesion of a glue, applied along the length of said flap to bond in overlapping relationship the flap and an end wall (5) of the carton in which the closure flap (16), lift-tab (10) and reopen tab (19) are provided, to said area of said inner end flap.

8. A carton according to any preceding claim, wherein at least one window (7) is formed in an end wall (4) of the carton and a translucent sheet (8) extending across the window is secured to the inside surface of said end wall (4).

9. A carton according to claim 8, wherein two windows (7) are formed in said end wall (4) of the carton, one being located close to a bottom wall of the carton and the other being located between said one window and a top wall of the carton.

10. A carton blank that is stamped to provide weakening and cut lines to enable it to be assembled into a carton according to any preceding claim.

11. A carton blank according to claim 10, wherein said closure flap (16), lift tab (10) and re-open tab (19) are provided in one end wall (5) and the locking tongue (21) is provided in an end flap (6), which is to be glued to the inside surface of the end wall (5) in which the closure flap, lift tab and re-open tab are provided for assembling the carton.

12. A carton substantially as hereinbefore described with reference to the accompanying drawings.

13. A carton blank substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.