EP0061980B1 - Easily openable can with pull tab and score line - Google Patents

Abstract

1. An easy-opening lid which is circular or elongate for a circular or elongate can, comprising a pull-off tab (4) and an incision line (2) defining an opening panel (3), the opening panel (3) and the lid having a common axis of symmetry (XX'), the panel (3) comprising a stiffening rib (8) which forms a boundary to the incision line (2) inside the panel (3), and which comprises two arms, the respective front ends (13, 13') of which are positioned on both sides of the axis (ZZ') of the tab (4) and slightly to the rear of the straight line (AB) of the initial fold of the panel (2), said straight line (AB) of the initial fold being perpendicular to the axis (ZZ') of the tab (4) and substantially tangential to a rivet (5) for attaching the tab (4) at the rear of this rivet (5), characterised in that each of the two arms of the stiffening rib (8) has at least one local discontinuity (9-12, 9'-12') in the shape of its cross-section, and at least some of these local discontinuities are positioned asymmetrically with respect to the axis of symmetry (XX') of the panel (3) and of the lid.

Description

For a long time, manufacturers of cans have endeavored to produce metal cans which are strong enough to withstand pressure without failure during sterilization operations, impacts during handling and crushing during storage, and which are, however, easy for the consumer to open.

As shown, for example, in patents FR-A Nos 407604, 2000528 and in patent US-A No 2085200, it has been a long time since we had the idea, on the one hand, of engraving on the wall a incision line which facilitates, when the time comes, the tearing of the wall around an opening panel, on the other hand, to fix to the wall a tear-off and gripping tab which first facilitates the perforation initial of the wall, then the tearing of the panel. As can be seen in patent FR-A No 407604, it is known to stiffen the surface of the panel by a raised rib, or a hollow rib, which borders the panel along the line of incision in order to provide the panel good mechanical resistance in all phases of its life: production, crimping, sterilization, various handling before final use. The rib (or groove) is largely interrupted at the location of the tongue.

For the sake of clarity, we will denote, below, by the front part of the panel, the part which is located near the tongue and, by the rear part, the one which is the farthest from it and which detaches last. of the cover when opening. The axis of the panel will be designated its greatest axis of symmetry. It will also be considered that the line of incision and the peripheral rib consist of two branches originating on either side of the tongue and joining at the rear end of the panel.

• 1. Le consommateur passe le doigt entre l'arrière de la languette et la paroi. La languette, fixée à la paroi par un moyen de fixation tel qu'un rivet, situé en son milieu, bascule vers l'avant. Elle appuie fortement par son nez avant rigide sur la paroi au niveau de la ligne d'incision. Le moyen de fixation doit résister et le nez rigide de la languette perforer la paroi à l'aplomb de l'incision.

However, we know that the opening of a can using a tab such as those represented in the patents FR-A Nos 2 ₀₀₅₂₈ or FR-A 2074598 is an operation which is carried out in several stages:

• 1. The consumer passes his finger between the back of the tab and the wall. The tongue, fixed to the wall by a fixing means such as a rivet, located in the middle, swings forward. She presses strongly with her rigid front nose on the wall at the level of the incision line. The fixing means must resist and the rigid nose of the tongue perforate the wall directly above the incision.

The nose of the tongue penetrates slightly inside the container.

Under the pressure of the front part of the tongue, the wall folds under said tongue towards the inside of the box along a line perpendicular to the axis of the tongue and very close to the means of fixing the tongue to the wall. This first fold line is thus adjacent and substantially parallel to the line of incision at the level of the perforation.

2. The consumer then pulls strongly on the tab in a direction perpendicular to the wall. The perforation of the wall must continue in a tear which deviates on either side by following the line of incision in opposite directions substantially perpendicular to the axis of the tongue.

3. The consumer continuing his action generally pulls the tongue outwards obliquely towards the rear of the opening panel. The tearing continues on both sides along two branches substantially parallel to the axis of the panel.

The tear must be gradual. Indeed, the block opening of the panel would require excessive effort on the part of the consumer, and also no less excessive tear resistance of the means for fixing the tongue to the panel. A carefully studied rigidification of the panel is required. The covers are often in the form of trays arranged in concentric stairs. They are often still stiffened by ribs or grooves.

4. Finally, the consumer often wants to completely tear off the opening panel. The tearing then continues well away from the tongue, in particular for covers with total opening of long shape, that is to say those whose length to width ratio is of the order of 2 or greater.

For long covers with full opening, the panel which has bent regularly towards the rear tends to turn over at the rear of the box. It has become very flexible, like a spring. The consumer has difficulty exerting a backward force in a direction substantially tangential to the cover. In addition, if the consumer awkwardly releases the tab, the panel can deploy suddenly and, by spring effect, may come to close abruptly splashing the consumer. To avoid these inconveniences, it is advantageous to stiffen the rear of the panel.

At the end of opening, the consumer must also be able to exert shearing by a back-and-forth movement, without producing a spring effect when the panel is completely detached from the box.

Thus, the lids with easy opening must satisfy contradictory requirements: good resistance before opening and, however, a puncture then an easy tear according to a well defined course during opening. In particular, the opening panel for long-shaped covers must be able to be torn off completely without difficulty, even for covers of large dimensions, that is to say with a length of the order of 120 mm or more, greater length. hand-width.

It turns out that the covers with a continuous peripheral stiffening rib according to patent FR-A No. 407604 have had little success. In fact, this rib extending around the opening panel contributes to effectively guiding the tearing of the wall along the incision rod which is clamped between the rib and the edge of the cover. This rib gives a good overall rigidity to the panel, mainly in the axial direction, but, as a result, the consumer's effort on the tongue is transmitted, in a way, to the entire panel. The effort required of the consumer is very important, often prohibitive. Too often, this effort causes the fastening means of the tongue to yield to the wall before complete opening.

As we can. to see it by the patents US-A No 3698590 and FR-A No 2158505, we thought of using this type of cover stiffened by a peripheral rib but by dividing by interruptions this rib. In a way, the panel is divided into successive elements individually stiffened by rib elements symmetrical with respect to the axis of the panel. Thus, in patent US-A No. 3698590, the easy-opening cover is provided with ribs of limited dimensions intermittently stiffening the opening panel and defining between them, thanks to their symmetrical discontinuities, fold lines of this panel when opened. These folds are made in flexible areas of the panel and, although splashing by the spring effect of the cover is avoided, the mode of tearing and folding remains practically unchanged, which may explain that the covers of this type have not until no more successful than the lid according to patent FR-A _No. 407604.

Despite the failures or inadequacies of the attempts made so far to avoid both the opening difficulties and the incidents due to the spring effect of the panel being torn off, the applicant has found that, with relatively modifications simple, we could make covers with opening panel stiffened by a peripheral rib which give remarkable results: very good resistance before use, easy opening, low cost of realization, this thanks to the simplicity of the drawing.

The cover, object of the invention, has a shape reminiscent of that of the cover according to patent FR-A No 407604. It however responds in a particularly happy manner to the various and even contradictory constraints imposed on easy-opening covers.

This cover, preferably of long shape, with easy opening, with tearing tab and incision line defining an opening panel which has a stiffening rib (or groove) which borders the incision line at the inside the panel, this cover has the particularity that each of the branches of its rib has at least one slight very localized discontinuity of the shape of its cross section, this discontinuity consisting of a partial and local flattening, or rather a primer of transverse fold on its ridge line. In addition, the discontinuities of one and the other branch are asymmetrical with respect to the major axis of the panel. If the tab is not in the axis of the cover, the discontinuities will be arranged asymmetrically both with respect to the axis of the panel and with respect to the axis of the tab.

These discontinuities, even partial and localized, create points of weakness on the rib. They facilitate transverse folds of the rib, and consequently of the panel. Their asymmetry means that the rib, and consequently the panel, bends according to the discontinuities found alternately on one then on the other branch. The consumer's effort is concentrated alternately on one and then the other branch of the incision line bordering the rib. Conversely, this reduces the minimum force exerted on the tongue fixing means. At the start of the opening, this concentration of the force on one of the branches is further accentuated when the tongue is arranged in a corner of the cover.

With the exception of small aluminum covers, it is useful to make several discontinuities on each of the branches of the rib. Thus, in panels where one of the branches is longer than the other, such as panels with an offset tongue, at least two discontinuities are required on the longest branch.

• Après la perforation initiale par le nez de la languette et la première pliure de la paroi vers l'intérieur de la boîte, sous la languette, le consommateur peut, sans effort exagéré, déchirer le couvercle le long de la ligne d'incision jusqu'aux extrémités avant des deux branches de la nervure, cela comme avec les couvercles de l'art antérieur.

With covers according to the invention, the opening is carried out as follows:

• After the initial perforation by the nose of the tongue and the first folding of the wall towards the inside of the box, under the tongue, the consumer can, without exaggerated effort, tear the lid along the line of incision until at the front ends of the two branches of the rib, as with the covers of the prior art.

The tearing of the wall then continues alternately along one branch of the incision line and then the other. This splits the effort required from the consumer, who is concentrated successively on one and then on the other branch.

The rib folds successively according to the discontinuities located on one then on the other branch. The panel itself folds in a succession of zigzag lines which join the discontinuities arranged on both branches of the rib. It is gradually divided into planar elements of small area which gradually rise from the cover and somehow form leverage for the consumer. The panel is stiffened during opening by the zigzag folds and cannot be closed suddenly in the manner of a spring if, by mistake, the consumer releases the tab before tearing off said panel completely.

The phenomenon of tearing off the panel is thus well divided and controlled, both by the rib and its discontinuities.

For easy opening, the maximum distance between two discontinuities on the same rib will preferably be of the order of 40 mm.

• a) grâce à la nervure périphérique de forte épaisseur, une bonne résistance du couvercle lors des diverses phases d'utilisation avant ouverture: fabrication, sertissage, stérilisation du contenu de la boîte;
• b) une ouverture facile grâce aux discontinuités dissymétriques, qui permettent un arrachage progressif du panneau et, de ce fait, limitent l'effort demandé à l'utilisateur, effort que doit supporter la languette et surtout son moyen de fixation au panneau;
• c) un bon guidage de la ligne de déchirure le long de la ligne d'incision par une nervure de forte épaisseur. Le phénomène de déchirure de la paroi et d'arrachage du panneau est bien contrôlé à la fois par la nervure et ses discontinuités transversales;
• d) une rigidification progressive du panneau en cours d'ouverture par des plis obliques qui interdisent sa fermeture brutale par effet ressort si le consommateur lâche prématurément la languette d'arrachage.

We thus have:

• a) thanks to the very thick peripheral rib, good resistance of the cover during the various phases of use before opening: manufacture, crimping, sterilization of the contents of the box;
• b) easy opening thanks to asymmetrical discontinuities, which allow tearing progressive of the panel and, therefore, limit the effort required of the user, effort that must support the tongue and especially its means of attachment to the panel;
• c) good guidance of the tear line along the incision line by a very thick rib. The phenomenon of tearing of the wall and tearing of the panel is well controlled both by the rib and its transverse discontinuities;
• d) progressive stiffening of the panel during opening by oblique folds which prohibit its abrupt closure by spring effect if the consumer prematurely releases the tear-off tab.

The invention will be better understood from the following description of two particular examples of covers corresponding to the attached figures.

Fig. 1 shows, seen in plan, from above, a cover according to the invention.

Fig. 2 shows a cross section of the same cover.

Fig. 3 shows, in plan view, a second variant of the cover according to the invention.

Fig. 4 shows a cross section of the cover according to FIG. 3.

Fig. 5 shows, in section, on a large scale, the discontinuities of the reinforcing rib.

In these drawings, similar elements have the same references.

In fig. 1, 2, 3 and 4 are shown two types of cover with easy opening, according to the invention. These covers are both bordered by a rim 1 intended to be folded and crimped on the edge of a box not shown here. Along this rim has been engraved an incision line 2 defining an opening panel 3. A tongue 4 is fixed to the panel by an integrated rivet (5); this tongue 4 comprises a gripping ring 6 at the rear and a perforation spout 7 the front end of which is disposed substantially in line with the incision line 2.

The two covers shown have a rib 8 of relief reinforcement disposed at the edge of the panel 3 along the line of incision 2. However, in both cases, this rib 8 is not continuous like that the FR-A patent? 407604, but has slight discontinuities 9, 10, 11, 12, 9 ', 10', 11 ', 12' distributed along the rib 8 on either side of the large axis of symmetry (XX ') of the cover . These discontinuities are, preferably, simple transverse gradations 9, 10, 11, 12, 9 ', 10', 11 ', 12' interrupting the crest line of the rib 8, as shown in fig. 1, 3 and 5.

Note that the cover of Figs. 1 and 2 is substantially symmetrical with a tongue 4 arranged in the longitudinal axis of the cover (XX '). The cover of fig. 3 and 4 is clearly asymmetrical with its tongue 4 oriented along the axis (ZZ ') oblique to the axis (XX') of the cover.

In the two cases shown, the rear discontinuities 9, 9 'are arranged symmetrically with respect to the axis (XX') of the cover. But, more generally, their location is determined experimentally according to the type of cover so that the continuous portion of rib 8 which connects them stiffens the panel transversely and longitudinally in this area. Thus, at the end of the opening, the user can easily complete the tearing off of the panel 3 by back and forth movement.

The other discontinuities, at least partial, 10,10 ', 11,11', 12,12 'must be asymmetrical with respect to the axis (XX'), as shown here. The lines joining two homologous discontinuities 9-10 ', 10'-10, 10-11', 11'-11, 11-12 ', 12'-12 form with this axis an angle (a) between 60 and 80 ° . We can notice that the rib 8 is interrupted under the tongue 4 fixed directly on the plane of the periphery of the panel 3.

With this type of tab 4 used in the two examples of covers shown, immediately after the initial perforation by the nose 7, the front end of the panel 3 folds in a known manner towards the inside of the box. The initial folding of the panel takes place along a straight line (AB) perpendicular to the axis (ZZ ') of the tongue and substantially tangent to the rivet 5 at the rear of this rivet. For other types of tongues connected to the rivet 5 by a flexible tab, the fold line (AB) is tangent to the rivet 5 at the front of this rivet. The rib 8 is interrupted under the tongue 4, the front ends 13, 13 ′ of each of the branches of the rib 8 are arranged, relative to the nose 7 of the tongue, slightly behind the fold line (AB).

The opening of the boxes according to fig. 1 or 3 is carried out very easily: as in the prior art, after the initial perforation by the rigid nose 7, the tearing of the wall continues following the line of incision 2 according to two symmetrical branches on both sides other of the tongue 4. As in the prior art, the panel 3 is stiffened transversely by its initial fold according to (AB), which contributes to preventing the bulging of the panel according to a longitudinal fold very harmful for the rest of the opening.

In the case of the two covers shown, the transverse rigidity of the panel at the start of opening is reinforced by the two branches of the rib 8 which extend substantially in line with the straight line (AB). The two branches of the rib 8 also help guide the initial tearing of the wall along the two branches of the incision line 2, on either side of the tongue 4.

As regards the generally symmetrical cover of FIGS. 1 and 2, the asymmetry of the discontinuities 12 and 12 ′ with respect to the axis (XX ′) of the cover results in an asymmetry of the rigidity of the two branches of the rib 8 and, consequently, of the panel 3 itself, by report to said axis (XX ').

After the initial perforation, the pulling force transmitted by the tongue 4 is concentrated on one then the other side of the cover until the discontinuities 12 and 12 '. The wall gives way on one side then on the other. The panel 3, torn along a portion of the incision line 2 limited by a cord substantially corresponding to the discontinuities before 12,12 ', folds along this line 12, 12'. The force transmitted by the rivet 5 then concentrates on the nearest non-torn part 11, 12 which in turn tears by creating a new transverse fold 11, 12 '. The tear continues alternately along one branch and then the other of the incision line 2, without the consumer having to exert significant effort. The tear line is well guided by both the incision line 2 and the rib 8 which borders it. At the end of opening, the panel 3 is stiffened by the folds joining in a zigzag the discontinuities located alternately on the two branches of the rib 8 as well as by the rear transverse part of the rib 8 which extends without interruption between the discontinuities 9 , 9 '. The zigzag folds are shown in dotted lines in fig. 1.

For the asymmetrical cover of fig. 3 and 4, the eccentricity of the tongue 4 relative to the axis (XX ') alone would be enough to initiate an asymmetrical tear. This asymmetrical tear continues thanks to the asymmetrical position of the discontinuities. After the initial folding of the panel 3 towards the inside of the box 12 along the line (AB), the consumer pulls the panel towards the outside of the box in a vertical plane passing substantially through (XX '). The front part of the most stressed incision line 2 yields first to the level of the discontinuity 12. The tearing of the cover then continues on the other side towards the discontinuity 12 ′ and, thus, alternately towards the discontinuities rear 9.9 '. This alternative tear on the one then on the other side of the cover requires only a reduced effort from the consumer and, consequently, a relatively low resistance of the rivet 5. As in the example of FIGS. 1 and 2, the angle (a) between the axis (XX ') and the lines shown here in dotted lines, which connect two homologous discontinuities (10'-10, 10-11', 11'-11, 11-12 ', 12'-12,12-13, is most often between 60 and 80 ° C. It is moreover not essential to have an even number of discontinuities on the rib. 3 and 4, with a tab 4 in a corner of the cover, is particularly recommended.

The maximum distance (L) between two successive discontinuities such as 10, 11 is of the order of 40 mm. For an aluminum foil cover 0.25 mm thick, 55 mm wide and 150 mm long along (XX '), good results have been obtained with a rib of width e = 7 mm and height h = 0.7 mm.

The discontinuities shown in fig. 1,3 and 5 are simple, partial and localized flattenings of the rib 8, leaving it with a residual height of the order of ta% to% of its height (h). They are more simple transverse weakenings than real discontinuities. They are sufficient to locally reduce the moment of inertia of the rib and, consequently, that of the panel in a vertical plane.

The width (e) and height (h) of the ribs 8, the size and spacing (L) of the discontinuities obviously vary with the dimensions of the covers, the thickness of the wall and the characteristics of the metal used. Tests are necessary to determine the best solution in each particular case according to the thickness and dimensions of the cover, as well as the quality of the material.

Although the two lids shown here are lids for elongated boxes, the rib stiffening device with ribs with discontinuities can also be successfully used on lids for large circular boxes. The axis of symmetry of the cover is then that passing through the center of the panel and the axis of the tongue fixing rivet.

When opened, the surface of the panel is divided into asymmetrical curvilinear asymmetrical triangles or quadrilaterals by the folds joining the discontinuities of the rib, on either side of the axis.

A peripheral rib 8 comprising discontinuities can just as easily be used on panels 3 whose incision 2 is not completely closed but is interrupted over a certain length, for example at the rear of the panel. This provision encourages the consumer not to tear the cover panel completely and to leave it attached to the box by the connecting tab which remains at the site of the interruption of the incision.

Claims (7)

1. An easy-opening lid which is circular or elongate for a circular or elongate can, comprising a putt-off tab (4) and an incision line (2) defining an opening panel (3), the opening panel (3) and the lid having a common axis of symmetry (XX'), the panel (3) comprising a stiffening rib (8) which forms a boundary to the incision line (2) inside the panel (3), and which comprises two arms, the respective front ends (13, 13') of which are positioned on both sides of the axis (ZZ') of the tab (4) and slightly to the rear of the straight line (AB) of the initial fold of the panel (2), said straight line (AB) of the initial fold being perpendicular to the axis (ZZ') of the tab (4) and substantially tangential to a rivet (5) for attaching thetab (4) atthe rear of this rivet (5), characterised in that each of the two arms of the stiffening rib (8) has at least one local discontinuity (9-12, 9'-12') in the shape of its cross-section, and at least some of these local discontinuities are positioned asymmetrically with respect to the axis of symmetry (XX') of the panel (3) and of the lid.

2. A lid according to Claim 1, characterised in that even if the pull-off tab (4) has an oblique axis of symmetry (ZZ') with respect to the axis of symmetry (XX') of the opening panel (3) and of the lid, at least some of the local discontinuities of the stiffening rib (8) are positioned asymmetrically both with respect to the axis (ZZ') of the tab (4) and with respect to the axis of symmetry (XX') of the panel (3) and of the lid.

3. A lid according to either of Claims 1 and 2, characterised in that if the arms of the rib (8) differ in length, the longer arm has at least two local discontinuities (10,11).

4. A lid according to any one of Claims 1 to 3, characterised in that the discontinuities of the rib (8) are simple local flattenings leaving the rib (8) with a residual height which is between half and two thirds of its height (h).

5. A lid according to any one of Claims 1 to 4, characterised in that the rib (8) has at least two discontinuities (9,10, 9', 10') per arm, and the rear discontinuities (9, 9') may be positioned symmetrically with respect to the axis (XX'), and the other discontinuities such as (10, 10') are positioned asymmetrically with respect to this axis (XX').

6. A lid according to Claim 5, characterised in that the maximum distance (L) between two successive discontinuities such as (10, 11 ) of the rib (8) is about 40 mm.

7. A lid according to any one of Claims 1 to 6, characterised in that the stiffening rib (8) is interrupted under the tab (4), the front ends (13, 13') of the two arms of the rib (8) being positioned, with respect to the nose (7) of the tab (4), slightly to the rear of the straight line (AB) of the initial fold of the opening panel (3).

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