QPENING DEVICE

The present invention relates to an opening device which is used for opening containers, more particularly a pull tab device for a container, typically on a container lid or can end.

Sealed metal containers in the form of cans and tins are used for many purposes, most commonly food and drink. It is known to have a pull tab (sometimes referred to as a "ring pull") mounted on the lid of the container, which allows the container to be opened easily without the need for a tin opener or other tool. Pull tabs come in many forms but in general they share a common mode of operation in that they provide a lever for the user to break and/or deflect a weakened area of a container to gain access to the contents. Usually this action starts a tear along a weakened line of material which encircles a removable tab or lid. The pull tab may then function as a handle which can be pulled in order to tear off the removable portion. The levering element of the pull tab can be various shapes and sizes depending on its intended purpose. It will have a grip portion at one end for pulling by the user. This is typically in the form of a ring for the user to hook their finger or thumb through, though in some cases it may be closed off to provide a tab for the user to pinch. The other end of the levering element may be formed into a pointed nose, for example, for food cans where it is necessary for the nose portion to exert a concentrated force on a small area, or it may be more rounded, for example on drinks cans, where the nose portion deflects a weakened tab off to one side.

The pull tab typically has a levering element with a roughly ring-like form, in as much as it is normally stamped from thin sheet metal and has been rolled at its edge to create an encircling bead around the perimeter which provides the levering element with the necessary rigidity. The strengthened ring-like edge of the levering element may define an elongate shape, for example, an oval, tear-drop, plectrum or other more angular shape.

Typically, the levering element is attached to a container by a rivet or rivet-like fixing extending through an attachment portion of the pull tab. A connection then extends between the levering element and the attachment portion, and this may be one of various forms from a narrow, resilient web extending to the nose portion of the pull tab, through to a much wider web that may encompass the attachment portion on all sides, extending all the way from one

side of the levering element across to the other. The exact form of this connecting web will depend on the intended operation of the pull tab and its preferred levering characteristics.

Often this web will allow the levering element of the pull tab to hinge slightly with respect to the attachment portion, to allow the user to flick up the grip portion of the pull tab slightly easier and gain room for a finger or thumb underneath. In these arrangements the connecting web may be cut away at the rear and sides of the attachment portion. This type of pull tab is particularly common on drinks cans at the moment where the pull tab remains on the container. In other arrangements, the connection to the attachment portion may be less forgiving, for example, where the attachment portion is joined all the way round by a web of material extending across to the levering element. With such an arrangement, any pivoting movement of the levering element is provided through twisting of the material of the can (for example, along a hinge axis passing substantially through the attachment portion), which can require considerable force.

For the majority of pull tabs, during opening of the container there is a combination of the two levering actions taking place; initially the levering element hinges about a region of the connecting web as the user inserts a finger or thumb under the grip portion of the pull tab, and then it hinges through the twisting of the material of the container adjacent the attachment portion as the container is pierced and a tear is created.

A problem with known pull tabs is that they can often be difficult to lift up from the surface of the container so that the user can insert a finger or thumb under the grip portion. This is because they tend to be quite stiff as they must be able to transmit the levering forces to the surface of the container, and also because the pull tabs are usually held flat against the surface by the attachment to the container, particularly the ones discussed above which do not pivot with respect to the attachment. This difficulty with 'starting' the pull tab is particularly a problem for older people and people with reduced strength in their fingertips. It can also be a problem for disabled people and people with medical conditions like arthritis. There may also be situations where it is desirable to open such containers in environments where there is extreme cold, for example, whilst pursuing outdoor or extreme pursuits or for army personnel. In such environments, the user may be wearing gloves or have numb hands, making the lifting up and pulling of a conventional pull tab difficult or impossible.

From a broad aspect, the present invention can be seen as offering a solution to these problems by providing an opening device, which preferably is in the form of a pull tab (ring

pull), having a grip portion that is moved from a storage configuration to a use configuration by a bistable device.

From one aspect, the present invention can be seen to provide an opening device in the form of a pull tab, comprising a levering element for a user to operate and an attachment portion which can be fastened to a container, the levering element having a grip portion at one end to be gripped by the user and a nose portion at the other end to be levered against an area of the container, the levering element being joined to the attachment portion at a location between the grip portion and the nose portion in order to allow the levering element, once attached to the container, to be levered about the attachment portion and in that way urge the nose portion against the container, wherein the levering element comprises a bistable device providing the levering element with curvature in a longitudinal direction between the nose portion and the grip portion such that the levering element has a substantially convex storage configuration, in which the levering element arches away from and extends over the attachment portion with the grip portion in a lowered position in proximity to the container, and a substantially concave use configuration for opening the container, in which the levering element adopts an opposite curvature with the grip portion spaced further from the surface of the container to allow the user to access the grip portion.

This arrangement has the advantage that the levering element can be actuated to switch from the convex storage configuration to the concave use configuration, and in this way, raise the grip portion from the surface of the container to allow the user to grip the grip portion more easily without any of the problems mentioned previously.

Preferably the whole of the levering element is a bistable device so that the levering element is curved for its whole length, from the nose portion to the grip portion. In this way the levering element can still be made relatively stiff but at the same time can be actuated without requiring undue pressure to be exerted through the user's finger or thumb.

In another embodiment, only a part of the levering element is formed as a bistable device. The bistable device may represent two thirds or less of the levering element. In another embodiment, the bistable device constitutes less than half of the length of the levering element in order to provide stiffness in other regions of the levering element. The bistable device is preferably arranged so that it extends directly over the attachment portion when viewed from the side. In such embodiments, it is preferable if the grip portion end of • the levering element is inclined upwardly with respect to the rest of the levering element, so that in a storage configuration it lies substantially against the surface of the container, and in

the use configuration it is more steeply inclined than the rest of the levering element to allow a user to insert a finger or thumb more easily under the grip portion.

Preferably the bistable device comprises two members which form part of the levering element. Preferably the two members extend on either side around the attachment portion, joining the grip portion to the nose portion and the connection of the levering element with the attachment portion.

Preferably a bar extends from one member to the other member at the apex of the convex curvature. The bar can be pressed to trigger the bistable device so that it snaps into the opposite curvature, from its storage configuration to its use configuration. In one embodiment, the pull tab is in the form of an oval-shaped ring, where a portion of the ring forms a hinge section at the nose portion, a diametrically opposed portion forms the grip portion, and regions of the ring between form each of the two members of the bistable device, wherein a bar extends across the bistable device from one region of the ring to the other for actuating the bistable device. The bar may define an edge of a ring-like hole which the user can insert a finger through to operate the opening device.

Preferably the amounts of curvature in the convex and opposite concave forms are equal, but in some embodiments the curvature may be greater in the concave form in order to hold the grip portion at a larger separation from the surface of the container, whilst offering a low profile or compact arrangement in the convex storage configuration. In one embodiment the difference in curvature results in more than 5mm extra displacement at the grip portion end in the concave use configuration beyond a straight line (unstable) 'midway' position compared to the convex storage configuration.

The curvature may be more pronounced in certain regions, for example, it may be provided in such a way that a more curved profile is provided extending over the attachment portion and a less curved profile, possibly even a planar profile, extends to the grip portion end.

Preferably the curvature induced in the bistable device part of the levering element extends in the transverse direction as well as the longitudinal direction. This three dimensional form helps to improve the stiffness of the levering element. Viewed from another aspect, the present invention can be seen to provide an opening device in the form of a pull tab comprising a levering element and an attachment portion which can be fastened to a container, the levering element having a grip portion at one end to be gripped by the user and a nose portion at the other to be levered against an area of the

container, wherein the levering element is connected to the attachment portion via a region which is formed as a bistable device.

When the pull tab is attached to the container, the bistable member has a first, storage configuration where the end of the levering element with the grip portion is positioned adjacent to a surface of the container and a second, use configuration where the end of the levering element with the grip portion is spaced further away from the surface of the container.

Thus in this aspect, a significant advantage is that the pull tab can be made with a substantially rigid levering element, enabling the user to apply a strong levering force against the container. Also the more flexible part of the pull tab that connects the levering element to the attachment portion and which may also allow the levering element to hinge, now provides the bistable device, which lifts the grip portion off the surface of the container enabling the user to hook a finger or thumb underneath easily. This is of particular benefit with food tins, where the lid is of a greater thickness compared to the usual construction of beverage cans, and thus a greater force is required to open the container.

The present invention encompasses containers of any form and also portions of containers, such as can ends, to which a pull tab, as described above, has been fastened at its attachment portion. The pull tab may be fastened to a lid or end of a container, or a side of a container. It may be fastened to a removable portion of the container or may remain in place on the container when accessing the contents.

Preferably the levering element of the pull tab is substantially planar when viewed from the side, though it may also include a bend along its length in order to raise the grip portion further from the surface of the container. The pull tab may be formed from thin sheet material with edge portions rolled to provide the requisite strength and rigidity. In this way the pull tab can be made cheaply from thin material, which might be a metal such as an aluminium alloy, or might be made of plastics or a composite material.

The attachment portion can also be integral with and encircled by the sheet material forming the levering element. Preferably the rolled edges broadly define a ring shape as described above, preferably a substantially oval ring shape or other elongate or angular shape having the nose portion and grip portions arranged at opposite ends of a longitudinal axis.

In one embodiment, the bistable device is formed by stamping the material of the pull tab to induce the curvature into the region connecting the levering element to the attachment portion. Thus this region might be plastically deformed to provide a curved or domed

surface, which can be switched from a convex to a concave profile to provide the storage and use configurations.

Preferably the region connecting the levering element to the attachment portion is of a shape which allows the levering element to hinge with respect to the attachment portion. The hinge axis is preferably located in this region, between the nose portion and the attachment portion. Preferably the connection between the attachment portion and the levering element is only present between the rivet fixing and the nose portion, in order that any hinging can take place ahead of the rivet fixing.

Preferably the region connecting the levering element to the attachment portion comprises two, preferably elongate, members which are biased together to form a bistable device. In one embodiment, the two members are urged together at one end against their natural resilience, to induce curvature in longitudinal and lateral directions of the pull tab.

This curvature enables the region to adopt either a concave or a convex profile in its function as a bistable device. In adopting this form, the attachment portion and the nose portion may become twisted from the pre-biased state and form part of the bistable device.

The two members of the bistable device preferably extend from the attachment portion as arms towards the nose portion of the pull tab. In one embodiment they may extend away from the attachment portion and towards the nose portion at between 30 and 60 degrees to a longitudinal axis, preferably at around 45 degrees. The members are preferably curved when viewed in plan, for example, the member may resemble an arc of a circle as it extends from the attachment portion towards the nose portion of the pull tab.

Preferably the pull tab is substantially symmetrical about a longitudinal axis and there is an aperture between the attachment portion and the nose portion of the pull tab along the longitudinal axis. This aperture provides one edge of each of the two members forming the bistable device. In conventional pull tabs, there is no aperture in this region. The other edge of the members may be provided by a cut away region. The cut away may be in the form of an arcuate cut or other shape.

The two members may be urged together at one end through a pinched v-section incorporated into the design of the nose portion. The forming of the pinched v-section draws the ends of the members together. This induces tension in the members, causing them to bow, both in the longitudinal and lateral directions, to define part of a convex or concave surface. The two members drawn together at one end in this way, form the bistable device.

Additional tension may be induced through drawing together the ends at the attachment

portion as well. It may be possible to induce tension in the two members in other ways, for example, by providing a fold, pinch or join in the attachment portion. However, the pinched v-section in the nose portion is preferred because it has the advantage of strengthening the nose portion through work hardening and also providing an improved profile for transferring load to the container.

Preferably the switch between the two modes of the bistable device causes a change in the angle of inclination of the levering element with respect to the surface of the container. In the first, storage configuration, the end of the grip portion may rest against the surface of the container or be positioned close to it. This has the advantage of preventing items from catching underneath the grip portion prematurely. The nose portion of the levering element may be raised slightly to compensate. In the second, use configuration, the nose portion may be lowered so that it can engage the surface of the container and the end of the grip portion is held in a raised position above the surface of the container to allow the user to grip it.

The end of the grip portion is preferably held a distance of 3mm or more away from the surface of the container in the use configuration, more preferably 5mm or more. In one preferred embodiment, the bistable device lifts the grip portion to provide a gap of 10mm or more. Thus in this way it may be possible to provide a larger gap under the grip portion of the pull tab than with the known pull tabs.

A shallow recess may be stamped into the surface of the container under the grip portion, or the container may have a deflectable recess, possibly formed as a further bistable element, to further improve access for the user's fingers.

An advantage of locating the bistable device in the region of the pull tab that connects the levering element to the attachment portion, is that just a small deflection in the bistable device can result in a much larger deflection in the grip portion because the displacement effect is amplified by the length of the levering element.

In another embodiment, the bistable device is arranged to lift the pull tab away from the surface of the container without substantially changing the inclination of the levering element. In this embodiment, the bistable device may be formed by two members extending substantially laterally from the attachment portion of the pull tab. Other arrangements are envisaged where the bistable device is arranged between the attachment portion and the levering element, but extending from the side of the attachment portion which is closest to the grip portion, hi one possible arrangement, the shape of this

region may allow the levering element to pivot with respect to the attachment portion, providing a hinge axis between the attachment portion and the grip portion.

The surface of the container may also be profiled to help activation of the bistable device. For example, the surface of the container may be formed with a raised portion, for example, in the form of a dome, a cylindrical element, a truncated cone, etc., to which the attachment portion of the pull tab is fastened. In the first, storage configuration, the levering element would sit relatively close to the raised portion and certainly below the level of the rim of the container. To activate the bistable device into the second, use configuration, the user presses on this raised portion of the container, possibly by pushing down on the top of the pull tab, to depress the raised portion into the container. The levering element, may then engage the surface of the container and trigger the bistable device to switch into the second, use configuration. This raised portion of the container is preferably sufficiently springy to return to its original position when the pressing force is withdrawn. This and the triggering of the bistable device will cause the levering element to be raised clear of the surface of the container for use. In the use configuration, with the bistable device flicked around into the opposite curvature, the levering element would be spaced further from the raised portion of the container, possibly even extending above the rim of the container, to provide plenty of access for the user to insert a finger or thumb under the grip portion.

This arrangement of a raised portion in the container lid also has an advantage when it comes to processing the contents of the food container. Typically this involves heating the contents to a high temperature to cook or sterilise them, usually causing the end of the container to bow out under the increased internal pressure. With the raised portion it is unlikely that the processing will trigger activation of the bistable device because the raised portion will simply be pushed out further from the surface of the container. Contact from a roller or another container may also help to maintain the pull tab in the storage configuration. Indeed it is envisaged that such processing may help to ensure that the bistable device is in its storage configuration if, for any reason, it was not already.

In the above embodiments the pull tab is in the form of a ring pull where the perimeter of the levering element encircles the attachment portion, which in turn enables the pull tab to be formed from a single sheet of material, usually at the canning stage. Thus the present invention can be seen to provide, at least in the preferred embodiments of the invention, a container (or container end) having an opening device in the form of a pull tab, the opening device being attached to the container at an attachment portion

and having a levering element for transmitting levering forces about the attachment portion against a weakened area of the container. In this particular aspect, the opening device is characterised in that the region of the opening device connecting the levering element to the attachment portion, through the resilience of the material of this connecting region, has a stable configuration which supports an end of the levering element in a displaced position which is spaced from the container, to allow a user to exert levering forces on the levering element easily.

Viewed from another aspect, the present invention can be seen to provide an opening device in the form of a pull tab for a container, wherein the opening device comprises a bistable device which is adapted to hold a grip portion of the opening device in a position adjacent to a surface of the container in a first, storage configuration, and be switched to a second, use configuration where the grip portion is held spaced from the surface of the container to allow it to be gripped by a user, wherein the bistable device is arranged so that when the opening device is levered up from its second, use configuration during opening of the container, the levering induces tensile forces in the bistable device. Preferably the majority of forces being transmitted from the levering element through the connection to the attachment portion are tensile forces.

An advantage of the embodiments discussed above where the bistable device is provided in the connecting region between the attachment portion and the levering element, is that the bistable device acts as a cord connecting the levering element to the attachment portion, and in this way the substantially rigid levering element, which is adapted to resist bending forces and is preferably planar, is able to transmit properly the levering forces which are applied by the user, and the more flexible bistable device can then act in tension.

According to a further aspect, the present invention provides an opening device in the form of a pull tab having a bistable device, the opening device having an attachment portion at one end for attaching to a container and a grip portion at the other for gripping by a user, wherein the bistable device comprises two elongate, resilient members that are held urged together against their resilience, whereby the two members exhibit curvature in the longitudinal and lateral directions of the opening device to provide either a convex or a concave profile.

According to a variation on this aspect, the present invention provides an opening device in the form of a pull tab having a bistable device, the opening device having a nose portion at one end for engaging a surface of the container and a grip portion at the other for

gripping by a user, the opening device having an attachment portion located between the nose portion and the grip portion for attachment to a container, the attachment portion being joined to the bistable device by a connecting web which allows the bistable device to be levered about the attachment portion in order to lever the nose portion against the surface of the container, wherein the bistable device comprises two elongate, resilient members that are held urged together against their resilience, whereby the two members exhibit curvature in the longitudinal and lateral directions of the opening device to provide either a convex or a concave profile.

The resilient members are preferably strip like elements formed from sheet material. The resilient members preferably extend between the attachment portion and the grip portion, preferably extending for more than half of the overall length of the opening device, most preferably more than 70% of the overall length.

Preferably the two members forming the bistable device converge towards the attachment portion. A grip portion for the user may be provided by a continuation of sheet material bridging the gap between one member and the other. In this way the bistable device can be made simply by stamping a U-shaped piece from a sheet of material (or two J-shaped pieces which are joined together at a bridging section) and drawing the ends together, against the resilience of the members, at the attachment portion, hi this way the bridging section joining one member to the other will hold the grip portion ends in a predetermined configuration, while the drawing together of the attachment portion ends will induce the requisite curvature in the bistable device. The rivet or rivet-like fixing, which fastens the opening device to the container, may also double up to hold the attachment portion ends together. Even with such a simple arrangement it has been found that this provides a bistable device with sufficient rigidity to enable containers to be opened. Such an arrangement has been found to provide significant leverage because the curvature provides three dimensional form. It also provides a grip portion that can be gripped easily, where the user can hook a finger or thumb through to exert a strong pulling force. The amount of material required is also minimal because two interlocking bistable devices can be stamped from roughly the same area of sheet material as a normal pull tab At the attachment portion of the first variant, the elongate members of the bistable device may be folded over to increase rigidity of the pull tab in this region. In this way it may be possible to enhance the levering effect of the nose portion.

In another embodiment, the elongate members may converge the other way, namely towards the grip portion. The fixing to a separate grip portion, for example, with a spot weld or rivet, may double up to hold the ends of the resilient members urged together and induce the curvature to form the bistable device. In embodiments having a separately formed grip portion, it can provide the advantage of allowing more access for the user's finger or thumb than the previous embodiment. It may also be possible to make this part from a different material. One embodiment is envisaged with a T-shaped or bar like grip portion for the pull tab. Such a separately formed grip portion may also be used with the previous embodiment if so desired. Preferably the bistable device is provided with an actuating member to trigger the switch from one curvature to the other. Preferably this is in the form of a raised bar that the user can push against which levers against the bistable device to activate it. A ridge may be provided in the surface of the container under the actuating member to aid activation of the bistable device. In one embodiment, the actuating member is provided by a continuation of one of the members, which has been folded over at the attachment portion and formed into a raised bar. In another embodiment, the actuating member is provided by a raised bar formed on the grip portion which has been attached to the bistable device.

Preferably the pull tab or surface of the container is provided with some form of locking device to prevent unwanted activation of the bistable device, which might otherwise occur during the processing of the contents or transport of the container to point of consumption. Preferably the locking device is in the form of a latch.

In other embodiments, the two elongate members may extend substantially parallel to one another. In such an arrangement, the two members would be held in a divergent arrangement at one of their ends when unstressed, but drawn together into a more parallel arrangement by the fixing of their other ends.

The bistable device may extend substantially the whole distance between the attachment portion and the grip portion, in order to make activation of the bistable device easier. However in some cases it may extend only a small portion of the distance, for example, less than half the distance, so that the pull tab can be made more rigid in the none bistable region to improve the levering ability of the pull tab.

In one example, the bistable device is provided within the third of the levering element which is located closest to the nose portion. In this arrangement, the deflection created by the bistable device is amplified most.

Viewed from another aspect, the present invention provides an opening device in the form of a pull tab having a bistable device arranged to engage a protrusion in a surface of a container, the bistable device having a convex form to accommodate the protrusion in a storage configuration, so that the opening device may lie adjacent to the surface of the container, and a concave form in a use configuration where the bistable device urges against the protrusion to raise a grip portion of the opening device from the surface of the container. In this arrangement, the pull tab can be made relatively rigid to enhance the levering action. The bistable device, which is preferably in the form of an arcuate strip, serves to assist with flicking the grip portion (i.e., the tail end of the pull tab) away from the surface of the container. By providing the protrusion, the levering element of the opening device can be lifted by a height twice that of the protrusion, at a point along the opening device where the lift may be amplified by two to four times because of the length of the levering element. Preferably the bistable device extends laterally with respect to the opening device. If desired, the bistable device may include an actuating member to assist the activation of the bistable device.

Viewed from another aspect, the present invention may be seen to provide a pull tab arrangement where the grip portion of a pull tab is deflected from a storage configuration to a use configuration through the activation of a bistable device which is arranged so that it may urge against the underside of the pull tab. Preferably one end of the bistable device is fixed to a surface of the container spaced from an attachment portion of the pull tab, and the other end of the bistable device is arranged to urge against the underside of the pull tab once activated. In another arrangement a central region of the bistable device engages the pull tab. The bistable device may be arranged longitudinally with respect to the pull tab or laterally. The concept of the bistable device may also be applicable to other opening devices. For example, it could be used in connection with the plastic opening devices on fruit juice cartons to provide a lid that stays open more easily for pouring of the contents or as an opening device on a box having a strip that is torn away from around at least three sides to allow the top to hinge open and shut. In the context of these containers, the opening device may provide more of a marketing tool than a solution to an existing technical problem. Certain preferred embodiments of the invention will now be described in greater detail by way of example only and with reference to the accompanying figures in which:

Figure 1 is a plan view of a conventional pull tab on a can end, in particular a can end for tinned food;

Figure 2 is a perspective view of a preferred pull tab with a bistable device in accordance with the present invention, the pull tab being shown in a storage configuration;

Figure 3 is a cross-sectional side elevation showing a pull tab with a bistable device in a use configuration, where the pull tab has pierced the container; Figures 4a, 4b and 4c each show a plan view of a preferred embodiment of the pull tab of the present invention;

Figure 5a is a perspective view showing a preferred embodiment of the pull tab of the present invention in the storage configuration and Figure 5b shows the pull tab with the bistable device activated to switch the pull tab into the use configuration; Figures 6a is a perspective view of another preferred embodiment of the pull tab of the present invention, and Figures 6b, 6c and 6d show a plan, sectioned perspective and side views of the pull tab;

Figure 7 shows a perspective view of an alternative preferred embodiment of the pull tab; Figure 8a is a side elevation of a further preferred embodiment of the pull tab of the present invention, Figure 8b is the pull tab in plan, Figure 8 c is the pull tab during an intermediate stage of production, Figures 8d and 8e show a side elevation and plan view respectively of a slightly modified embodiment of the pull tab of Figure 8a;

Figure 9a shows an alternative embodiment of a pull tab in plan, Figure 9b is a side elevation of yet a further preferred embodiment of the pull tab of the present invention, Figure 9c is the pull tab of Figure 9b in plan, and Figure 9d shows a slightly modified embodiment of the pull tab of Figure 9b;

Figure 10a is a side elevation of another preferred embodiment of the pull tab of the present invention and Figure 10b shows the pull tab in plan; Figure 1 Ia is a side view of a slightly modified embodiment of the pull tab in Figure

10a and Figure 1 Ib shows the pull tab in plan;

Figures 12a to 12c, 12e and 12f are side views of further preferred embodiments of the pull tab of the present invention, with Figure 12d showing a cross-sectional elevation of Figure 12c along line A-A; Figures 13a and 13b are plan views of yet further preferred embodiments of the pull tab of the present invention;

Figure 14a is a side view of another preferred embodiment of the pull tab of the present invention and Figure 14b is a plan view;

Figure 15a is a side view of a slightly modified version of the pull tab shown in Figure 15a,and Figure 15b is a plan view of that pull tab;

Figure 16a is a side view of another preferred embodiment of the pull tab of the present invention, Figure 16b shows a side elevation, and Figures 16c to 16e are side elevations of preferred pull tabs showing slight modifications;

Figure 17a is a side view of another preferred embodiment of the pull tab of the present invention with Figure 17b showing the pull tab in plan, Figure 17c shows the pull tab during an intermediate stage of production, and Figures 17d and 17e are plan views of preferred pull tabs showing slight modifications; Figure 18a is a perspective view of yet a further preferred embodiment of the pull tab of the present invention, with Figure 18b showing the pull tab in plan, and Figures 18c and 18d illustrating the pull tab in perspective and side cross-sectional elevations respectively;

Figure 19a is a side view of another preferred embodiment of the pull tab of the present invention, with Figure 19b showing the pull tab in plan; Figure 20a is a side view of yet another preferred embodiment of the pull tab of the present invention, with Figure 20b showing the pull tab in plan;

Figure 21a is a perspective view of a further preferred embodiment of the pull tab of the present invention, with Figure 21b showing the pull tab in position mounted on a can end, Figure 21c illustrates a perspective view of the pull tab from above at an intermediate stage of construction, and Figure 21d illustrates an underside perspective view;

Figure 22a illustrates a perspective view from above of an alternative pull tab at an intermediate stage of construction and Figure 22b shows the pull tab from underneath; and

Figure 23 a illustrates a perspective view from above of yet another embodiment of the pull tab, Figure 23b illustrates the pull tab from underneath and Figure 23c illustrates the pull tab at an intermediate stage of construction.

Figure 1 shows a conventional pull tab 1 provided on a can end 2. This is typical of current arrangements for food cans.

The pull tab 1 is attached to the can end 2 by a fastening in the form of a rivet 3 passing through an attachment portion 4 of the pull tab 1. The attachment portion 4 is joined to a levering element 5 by a connecting region 6. A cut-out 7 encircling the back and sides of the attachment portion 4 allows the levering element 5 to hinge at the connecting region 6, enabling a small amount of lift at a grip portion end 8 of the levering element 5. A nose

portion 9 is provided at the other end of the levering element 5 and formed into a point which is arranged immediately above a line of weakened material 10.

As the grip portion 8 is levered up, the nose portion 9 will be pushed down against the surface of the can end 2. The levering element 5 will initially pivot about the hinge in connecting region 6, and then once the nose portion 9 has started to engage the surface of the container, the levering element 5 will continue to pivot as a result of the can end 2 twisting from the torsion applied by the user. In so doing, a tear will be created as the nose portion 9 pierces the can end 2. Pulling on the pull tab 1 further enlarges the tear as a region of the can end 2 is deflected into the container. Once the tear has been enlarged to a certain size, it is then possible for the user to remove the lid of the container by pulling the pull tab 1 in the opposite direction, thereby extending the tear around the weakened line 10 until the lid has been removed from the can.

As shown in Figure 1, a hollow 11 may be provided in the surface of the can end 2, to provide more room for the user to insert a finger or thumb underneath the grip portion 8. However even with this hollow 11 , because of the rigidity of the levering element 5 and because the rivet 3 usually holds the pull tab 1 tight against the surface of the can end 2, there can still be considerable difficulty in prizing a finger or thumb underneath the grip portion 8. According to the present invention, an opening device is provided which is preferably in the form of a pull tab having a grip portion 8 that is lifted away from the surface of the container by a bistable device. The present invention can take a number of forms.

Figure 2 illustrates the top of a drinks can which has been provided with a pull tab 1 that includes such a bistable device. The pull tab 1 comprises a grip portion 8 arranged at the opposite end of a levering element 5 to a nose portion 9. The nose portion 9 is arranged to break and deflect a weakened tab of material 10 from the surface of the container. The pull tab 1 is connected to the container by a rivet 3 extending through an attachment portion 4, in the same way as a conventional pull tab. The rivet fastening may be formed from the material of the can end or using a consumable. A connecting region 6 hinges the attachment portion 4 to the levering element 5. The hinge axis is located between the nose portion 9 and the rivet 3. The back and sides of the attachment portion 4 are cut-away 7 allowing the levering element 5 to adopt a convex form.

In the embodiment of Figure 2, a portion of the levering element 5 is formed as a bistable device 12. In a first, storage configuration as shown in Figure 2, the bistable device 12 adopts a convex profile, and hence there is a small gap between the arched underside of

the pull tab 1 and the surface of the can end 2. The grip portion 8 may engage the surface of the container or be spaced just above it. In one embodiment (not shown) a small ledge may be provided in the surface of the container for the grip portion 8 to rest upon.

To open the container, the user presses the bistable device 12, triggering it to switch from the storage configuration to a second, use configuration where the grip portion 8 is lifted away from the surface of the can end as shown, for example, in Figure 3. A region of the levering element 5 close to the rivet 3 or middle of the levering element 5 may now engage the surface of the can end 2. hi this use configuration, the bistable device 12 adopts the opposite curvature, giving the pull tab 1 a concave profile. With the grip portion 8 raised off the surface of the can end 2, the user may insert a finger or thumb underneath the grip portion 8, enabling the user to pull on the levering element 5 to open the container in the normal way.

Figures 4a to 4c illustrate three examples of preferred pull tabs 1 in accordance with another aspect of the present invention having a bistable device 12 provided in the connecting region 6 that joins the attachment portion 4 to the levering element 5. The pull tab 1 comprises a grip portion 8 and a nose portion 9 arranged at opposite ends of a levering element 5. The levering element 5 is connected to an attachment portion 4 by the connecting region 6, and may be fixed to a can end 2 by a rivet 3 (shown in dashed lines) extending through the attachment portion 4.

The nose portion 9 is shown in each of these figures with three dashed lines 13 marking bend lines in the formed pull tab 1. An aperture 14 is provided between the attachment portion 4 and the nose portion 9 which divides the connecting region 6 into two. During forming of the pull tab 1, the nose portion 9 is pinched into a V-section, drawing the ends of the two connecting regions 6 together.

In Figure 4a the two connecting regions 6 are comparatively wide and extend from the nose portion 9 to the grip portion 8. In Figure 4b the cut-away 7 reduces the extent of this web so that the connecting regions 6 extend only from the nose portion 9 up to around half way along the levering element 5. In Figure 4c, the cut-away 7 is larger still and the connecting region 6 extends only between the nose portion 9 and a point about a quarter of the way along the levering element 5. hi this embodiment, the connecting regions 6 are joined only to a tapering section of the pull tab 1 located between the rivet 3 and the nose portion 9. These relatively narrow arms are of a substantially actuate form and join the levering element 5 at an angle of about 45° (angle α illustrated in figure 4c which is the angle

extending between the longitudinal axis and a line from the rivet 3 axis to the mid-way point of the connecting region 6 where it joins the levering element 5).

The attachment portion 4 locks the ends of the connecting regions 6 which are closest to the rivet 3 in a fixed orientation with respect to each other. The pull tab 1 is made from sheet material, for example, of metal or plastic, and will have a certain degree of resilience. During the pinching of the V-section nose portion 9, the other ends of the connecting regions 6 which are adjacent to the nose portion 9, are drawn together, against the natural bias from the resilience of the sheet material, to induce curvature in the connecting regions 6. The curvature extends in both the longitudinal and lateral directions of the pull tab 1 to give a convex profile or a concave profile. These two stable forms of the connecting regions 6 creates the bistable device 12.

Figure 5a shows the pull tab 1 in a storage configuration, with the levering element 5 lying substantially flat against the surface of a can end 2. The pull tab 1 is mounted on a raised portion 15 in the form of a cylinder or button. The nose portion 9 is located above a line of weakened material 10 and may be spaced slightly away from the surface as shown in the figure. The raised portion 15 of the can end 2 is deflectable and may be pushed into the container by the user pressing down on rivet 3. In so doing, the levering element 5 is urged against the surface of the can end 2, causing the connecting regions 6 of the bistable member 12 to switch from a convex profile to a concave profile, preferably in a snap action. This action might be accompanied by an audible "click" as the bistable member 12 snaps between the two modes. The user then releases the downwards pressure on rivet 3, allowing the raised portion 15 to spring back-into its original form. With the bistable device 12 now adopting a concave profile and the raised portion 15 returned to its original position, the grip portion 8 of the pull tab 1 is raised clear of the surface of the can end 2. This distance should be sufficient for the user to insert a finger or thumb easily underneath the grip portion 8 of the pull tab 1 prior to initiating a tear along the weakened line of material 10. In this use configuration, the nose portion 9 may be lowered into contact with the can end 2 and a hollow 11 may be provided under the grip portion 8, to improve further the access for the user. The levering element 5 may also include a bend (not shown) to hold the grip portion 8 higher still. With this arrangement of the present invention, only a small amount of deflection in the bistable device 12 is required to provide a significant amount of deflection in the grip portion 8 because the length of the levering element 5 will amplify the displacement of the grip portion end.

The main advantage for locating the bistable device 12 in this region, is that it allows the levering element 5 to be made as a substantially rigid item that will not bend untowardly as the user applies the levering force to create the initial tear. Instead, once the bistable device 12 has served its purpose of raising the grip portion 8 for the user to grip easily, it then acts as a cord connecting the levering element 5 to the attachment portion 4, and acts in tension. Therefore it does not matter that this part is not rigid and indeed the flexibility of the bistable device 12 may provide a small degree of pivoting movement. The levering element

5 can be stiffened by forming rolls of the sheet material along the longitudinal edges of the levering element 5. Figure 6a shows a perspective view of an alternative embodiment, which might be suitable for a drinks can. The pull tab 1 has a much more oval, ring-like form with a rounded nose portion 9. In this embodiment, the bistable device 12 is provided by connecting regions

6 extending laterally from the attachment portion 4. A cut-away 7 defines the back edges of the connecting regions 6 with front edges created by aperture 14. Curvature is introduced into the bistable device 12 during the forming operation, for example, by stamping. The curvature in the embodiment shown extends out of the plane of the pull tab 1 and only in the lateral direction. Figures 6a-6d show the pull tab 1 in its storage configuration. The pull tab 1 may be fastened to a raised portion 15 of the container in the same way as the embodiment of Figures 5a- 5b. Figure 7 illustrates a similar embodiment to that of Figures 6a-6d, the difference being that the bistable device 12 makes up only a portion of the connecting regions 6. The junction of a connecting region 6 to the remainder of the pull tab 1 is located in a web 16 extending across the nose portion 9 of the pull tab 1. This may provide a region which can hinge, allowing the pull tab 1 to pivot with respect to the attachment portion 4. In accordance with another aspect of the invention, the bistable device 12 is arranged to connect the attachment portion 4 with the grip portion 8. In the embodiment of Figures 8 a and 8b, the pull tab 1 is stamped from a sheet of material as a U-shaped item. The nose portion 9 of the pull tab 1 is made by folding over the bottom of the "U" of the U-shape and holding it in this form by the rivet 3 which joins the pull tab 1 to the container 2. The profile of the stamped article is shown in Figure 8c. The bistable device 12 is provided by two elongate members 5 a and 5b which form the two edges of the levering element 5. In its unformed state, the elongate members 5a and 5b diverge from the attachment portion 4. During the forming of the pull tab 1, the grip portion ends of the elongate members 5 a and 5b

are drawn towards one another, against their natural resilience, and are joined together, for example, with a rivet 17 to form the grip portion 8. The drawing together of the ends of the elongate members 5a and 5b, induces curvature and creates the bistable device 12.

In order to flick up the grip portion 8 from the surface of the container 2, the user may press against an actuating member 18 which is located at the nose portion end of the bistable member 12. As shown, the actuating member 18 may take the form of a raised bar or button that deflects the bistable member 12 when it is pushed. A step 19 is provided under the actuating member 18 to make it easier to trigger the bistable device 12 from the storage configuration shown in Figure 8a. A recess 20 may be provided to accommodate the material of rivet 17.

The actuating member 18 makes it easier for the user to trigger the bistable device 12 than by simply pushing down on the bistable device 12. This allows the bistable device to be made even more rigid while still allowing the user to trigger the bistable device 12. The stiffer bistable device 12 and nose portion 9 may provide better transmission of levering forces than with the pull tab of Figure 2.

Figure 8d shows an alterative embodiment where instead of having a separate actuating member 18 which must be attached to the pull tab 1 , the actuating member 18 is stamped from the sheet material and is integral with the pull tab 1. As shown in Figure 8d, the step 19 may be provided by a ridge in the container 2. Figure 8e shows the embodiment in plan.

In the embodiments of Figures 8a to 8e, the bistable device 12 is made up of two elongate members 5a and 5b which are joined together by a region of material forming the attachment portion 4. This arrangement is preferred as the diverging elongate members -5a and 5b can be joined together after the pull tab has been attached to the top of a can. This keeps the pull tab in a planar configuration whilst the rivet 3 is inserted, making attachment of the pull tab to the top of a can easier. Once in place, the diverging elongate members 5 a and 5b can be drawn together, against the resistance of the material, and joined together to induce the longitudinal and lateral curvature which gives rise to the bistable characteristics in the pull tab. In an alternative arrangement illustrated in Figure 9a, the joining material between the elongate members 5a and 5b is turned through 180° in order to form the grip portion 8 and the other ends of the elongate members 5a and 5b are held together by the rivet 3, which also joins the pull tab to the top of the can. In this way, the rivet 3 performs the dual

function of attaching the pull tab to the top of the can and retaining the elongate members 5 a and 5b in their biased configuration to induce the curvature in the pull tab.

Figures 9b and 9c illustrate another preferred pull tab where the actuating member 18 is provided at the grip portion end of the pull tab 1. In Figure 9b the actuating member 18 is formed from the sheet material of the pull tab 1. In Figure 9c, a separate actuating member

18 is shown attached to the grip portion 8 of the pull tab 1. To activate the bistable device 12, the user presses against the actuating member 18, pushing towards the nose portion 9. This triggers the bistable device 12 to adopt the opposite, concave curvature, lifting the grip portion 8 out of the hollow 11 in the container 2, for the user to grip. Figure 9d shows a similar embodiment with additional material in the nose portion 9 to improve the rigidity of this region.

Figures 10a and 10b show side and plan elevations of a further embodiment having a first rivet 21 to hold the material of the nose portion 9 together and a second rivet 3 which secures the pull tab 1 to the container 2. Figures 11a and 1 Ib illustrate a further embodiment where the container 2 is provided with a latch element 22 which holds onto the grip portion 8 of the pull tab 1 prior to use. The latch element reduces the risk of the bistable device 12 from triggering accidentally during processing of the container 2.

Figures 12a- 12f illustrate a number of different arrangements for improving the rigidity of the pull tab 1. hi Figure 12a, the folded sheet material forming the nose portion 9 extends to urge against the bistable device at a location 23, thereby increasing the rigidity of the attachment portion 4 and the levering element 5. Figure 12b illustrates a variation where the pull tab 1 is made from thicker material to improve the rigidity. Figure 12c shows an alternative where the elongate members 5a and 5b of the bistable device 12 are formed as a channel section to improve the rigidity. The embodiment of Figure 12e is similar with the channel section extending around the nose portion 9 to improve the rigidity of this region as well. Alternatively, the pull tab 1 may comprise two layers of sheet material, hi Figure 12f, the actuating member 18 is modified to provide additional strengthening.

In Figure 13 a, a first variation of the pull tab 1 is illustrated in this embodiment, the group portion 8 is integral with the elongate members 5a and 5b. The nose portion ends of the elongate members 5 a and 5b are drawn towards one another, against their natural resilience, to induce the curvature to form the bistable device 12. The ends are fixed together using the rivet 3 which fastens the attachment portion 4 of the pull tab 1 to the container 2.

The pull tab may include an actuating member 18 to help trigger the bistable device 12. Figure 13b shows a variation having wider elongate members 5a and 5b forming the bistable device 12, in order to improve the rigidity of the pull tab 1.

Figure 14a illustrates a further embodiment where the elongate members 5 a and 5b of the bistable device 12 converge and a separate grip portion 8 is provided attached to the bistable device 12.

Figures 15a and 15b show a variation on this, in which the actuating member 18 is integrally formed with the bistable device 12, rather than being a separate component which is attached. Figure 16a illustrates a pull tab in accordance with a further aspect of the present invention. The pull tab incorporates a bistable device 12 which is arranged to deflect the grip portion 8 from a storage configuration to a use configuration. As shown, the pull tab 1 comprises an attachment portion 4 which is fixed to the container 2 by a rivet 3. The sheet material in this region is folded over and held by the rivet 3 to increase the rigidity of the nose portion 9. A grip portion 8 is provided at the opposite end of the levering element 5, and in the storage configuration is arranged to lie adjacent or close to the surface of the container 2. A bistable device 12 is provided part way along the levering element 5, for example, mid- way, and is arranged to engage a ridge 24 or other protrusion provided in the container 2. Preferably there is a small gap between the grip portion 8 and the surface of the container 2, possibly through the grip portion including a bend 25 as shown in Figure 16a. In this way, the user can press down with their thumb or finger against the bistable member 12 and flick up under grip portion 8 with the other of their finger or thumb in order to activate the bistable device 12. The bistable device 12 then holds the grip portion 8 in a raised use configuration, enabling the user to insert easily a finger or thumb underneath the grip portion 8.

Figure 16b shows such a pull tab in plan. Figure 16c shows the pull tab with reduced material forming the grip portion 8. In this embodiment, \the transverse bistable device 12 extends beyond both sides of the grip portion 8. Figure 16d is a further embodiment incorporating an actuating member 18 which has been attached to the bistable device 12.

Figure 16e shows a similar arrangement where the actuating member 18 is formed integrally with the remainder of the pull tab 1.

Figures 17a to 17d illustrate further examples of pull tabs having a bistable device 12 that can be activated to support the grip portion 8 in a raised configuration for use. Again the pull tab 1 may include a bend 25 in the levering element 5 in order to provide additional room under the grip portion 8 for the user's finger or thumb. In the embodiments of Figures 17a to 17d, the ends of the levering element 26, 27 are drawn together, against the natural resilience of the device and are then held urged together by the rivet 3, which also fastens the attachment portion 4 to the container 2. This induces curvature in the bistable device 12, allowing it to adopt a convex storage configuration or a concave use configuration. Figure 17c illustrates the pull tab in its "as stamped" configuration before the ends 26, 27 of the levering element 5 have been drawn together and riveted. Figure 17d and 17e illustrate pull tabs with alternative profiles.

Figures 18a-18d illustrate an alternative pull tab 1 having a bistable device 12 extending from one side of the levering element 5 to the other.

Figures 19a and 19b illustrate an alternative embodiment where the bistable device 12 is provided as a separate component which is arranged to lever up the grip portion 8 of the pull tab 1. In Figure 19b, the bistable device 12 is shown extending substantially at right angles to the longitudinal axis of the pull tab 1. In Figures 20a and 20b, a similar arrangement is shown where the bistable device 12 extends in the same direction as the pull tab 1. hi both embodiments, the bistable device 12 may also include an actuating member 18 (not shown) in order to trigger the snap action of the bistable device 12.

Another variant of the pull tab is illustrated in Figures 21a to 2 Id. The pull tab blank 1 is stamped from a sheet of resilient material having a U-shape form substantially as shown in Figure 21c. A tab forming actuating member 18 is folded over the top of elongate members 5a and 5b of the bistable device 12 at a position close to where the rivet 3 is inserted through the attachment portion 4 to hold the pull tab 1 on a can end 2. Edge portions 28 of the grip portion 8 and the nose portion 9 are rolled over in order to increase the rigidity of the pull tab in these areas. To induce the longitudinal and lateral curvature into the pull tab, the ends 26 and 27 of the elongate members 5a and 5b are drawn together against their natural bias and secured by a rivet 17 passing through the two apertures 29 in the respective halves of the grip portion 8. Pressing the actuating member 18 causes the pull tab to switch from a convex form to a concave form where the grip portion 8 of the pull tab is held raised above the surface of the can end 2 (Figure 21b illustrates the convex form).

Figure 21c shows a perspective view of the pull tab 1 from above prior to introducing the rivet 17. Figure 21d illustrates the pull tab 1 in the same condition from underneath. Figure 21a shows the curvature that has been induced in the pull tab 1 by riveting the ends 26, 27 of the elongate members 5a, 5b together to create the bistable device 12 for the pull tab. Figure 21b shows how the pull tab 1 might be arranged on a can end, by passing a rivet 3 through the aperture 30 in the attachment portion 4. A sharp nose portion 9 is shown for rupturing a line of weakened material 10 on the can end. A ridge 31 is shown provided in the can end extending perpendicularly beneath the levering element 5. The ridge 31 helps the bistable device 12 to spring from a convex to a concave form when the actuating member is pressed, and also to hold the grip portion 8 in a raised configuration.

Figures 22a and 22b show perspective views from above and below of an alternative embodiment which includes cut-outs 32 within the lobs 33 forming the grip portion 8. These cut-outs 32 facilitate grip of the pull tab and also provide additional rolled edge portions 28 to increase the rigidity of this section. Figures 23 a and 23b show perspective views from above and below of another embodiment where a separate grip portion 8, in the form of a ring with rolled edge portions 28, has been attached to the ends 26, 27 of the elongate members 5a, 5b by a rivet 17. The outline form of this pull tab 1 echoes that of conventional ring pulls. Figure 23c illustrates an embodiment where the blank has an integral ring-shaped grip portion 8. In this arrangement, the end 27 of the elongate member 5b without the ring is drawn towards and attached to the end 26 of the elongate member 5 a with the ring by passing a rivet through the two apertures 30.

In the arrangements of Figures 21a to 23c, it may be easier to attach the pull tab 1 to the can end 2 first, whilst the pull tab 1 is in a planar configuration, and then to create the curvature in the bistable device 12 by securing the ends 26, 27 of the elongate members 5a, 5b together during a subsequent processing step.

Thus there has been disclosed a number of preferred arrangements for a pull tab for a container, for example, a drinks can or a food can. It would be clear that these opening devices can be used in other contexts, for example, as a pull tab which is used to open a box or carton where a strip of material is torn from the perimeter of the container.