The invention relates to vacuum closures for packaging containers, containers intended to be closed by such closures, and combinations of such closures with such containers. In particular, but not exclusively, the invention concerns containers of tinplate or other metal material, and closures which are substantially of metal or which have individually formed metal and plastics components assembled together.

Vacuum closures are so-called because they are required to hold and withstand a partial vacuum which is formed in the headspace of a container onto which the closure is fitted. The partial vacuum is typically generated when the closed container is cooled to ambient temperatures after a product sterilising, pasteurising or hot-filling operation. A primary use of vacuum closures is for food products for human consumption.

In some applications of vacuum closures the partial vacuum may have a sufficient intensity to make first closure removal by the consumer difficult or impossible to achieve, even by use of a special implement such as a coin. Proposals have therefore been made to enable the vacuum to be destroyed, by providing the closure with a vacuum release facility which can be operated before the closure is removed. One such proposal is featured in British patent specification No. 1393875 published 14th May 1975 and granted to the present Applicants in a former name. Figure 13 of that specification is reproduced as Figure 1 of the present Application, from which it will be seen

that a metal closure A of the kind commonly referred to as a "slip lid" is used to close a metal container B for a tobacco product C onto a partial vacuum. In order to facilitate the first opening of the container by the user the closure is formed with two adjacent holes which are closed in an airtight manner by rivets D, E. The rivets are integrally formed on the back of a plastics tab F and have their projecting free ends upset or reformed after insertion. Removal of the rivet D from its respective hole by pulling action on the tab allows air to enter the headspace of the container so as to destroy any partial vacuum, after which the closure can be removed from the container by continued pulling on the tab which is held captive by continued engagement of its rivet E in the second hole.

Another proposal for a vacuum closure having a vacuum release facility is made in US Patent Specification No. 5275679 assigned to Metalgrafica Rojek Ltda. In that specification a metal vacuum closure for a glass container has a vacuum release hole formed in a central recess of the closure. A resin-like material such as a plastisol is flowed into the recess in liquid form and bonds intimately over the area of the hole to a central portion of a thin film of a compatible material which has previously been formed on the underside of the closure. After the resin has hardened, it and the central portion of the thin film together form a removable plug by which the hole may be opened to leave the required air passage for air to enter the container. French Patent Specification No. 2718115 shows an easy-opening facility which is similar to that of US 5275679 (above) but applied to a vacuum closure for a

container which is of metal rather than of glass. Again, Specification 5275679 stands in the name of Metalgrafica Rojek Ltda as assignee.

From the foregoing it will be seen that proposals have been made in the patent literature for providing vacuum release facilities for vacuum closures adapted for both glass containers and metal containers. Moreover the vacuum release facilities themselves have been of differing forms. The present invention provides further vacuum closures having advantageous forms of vacuum release facility and container-engaging formations. It also provides containers adapted to be fitted with such vacuum closures.

Accordingly there is provided a vacuum closure for sealing a container body, the closure including a circular metal panel, the panel having an area of sealing compound for forming a seal between the panel and the container body, the upper surface of the closure having a concave depression with at least one vacuum release hole extending through the metal panel in the region of the depression, and a removable sealing plug located within the depression adapted to close the vacuum release hole until the plug is removed in order to release a vacuum, characterised in that the vacuum release hole is formed with an upturned edge so as to form a convergent chimney around the hole.

Preferably the metal panel is coated on at least a part of its upper surface with a first lacquer coating, and at least a part of its lower surface with a second lacquer coating, the material of the removable plug and the first and second lacquer coatings being such that the

plug material is adherent to the second lacquer coating but non-adherent to the first lacquer coating.

Conveniently the concave depression is a kidney- shaped depression, offset from the centre of the metal panel. This allows a conventional tamper indicating button to be retained in the centre of the metal panel. The concave depression conceivably includes at least first and second holes, the first for anchoring the sealing plug within the depression and the second constituting the vacuum release hole. Conveniently both first and second holes are each formed with an upturned edge so as to form a convergent chimney around each hole.

The invention further resides in a method of manufacturing a vacuum closure including the steps of:- i) stamping out a circular metal panel, ii) forming a concave depression in the panel, having at least one vacuum release hole, iii) applying a resinous compound to the concave depression to seal the vacuum release hole, such that at least some of the resinous compound extends through the hole to appear on the opposite side of the metal panel, and iv) pressing the metal panel with a forming tool in the region of the underside of the vacuum release hole so as to spread the resinous compound around the underside of the hole to ensure a gas tight seal until the compound is removed from the concave depression.

The forming tool may be conveniently be a heated forming tool. The invention further resides in the combination of a metal container body and a vacuum closure for sealing the container body, the container body including a curl

portion at its open end, the closure comprising a moulded plastics ring having an annular cover portion, a downwardly dependent skirt portion, a peripheral portion coupling together said cover portion and said skirt portion, and inwardly projecting means on the said skirt portion for engaging the curl portion of the container body, said cover portion, peripheral portion, skirt portion and inwardly projecting means cooperating to form an inwardly facing channel, a circular metal panel positioned within the plastics ring and having its periphery received within the said channel, the panel having an area of sealing compound for forming a seal between the panel and the container body, the upper surface of the closure having a concave depression with at least one vacuum release hole extending through the metal panel in the region of the depression, and a removable sealing plug located within the depression adapted to close the vacuum release hole until the plug is removed in order to release the vacuum from the container.

Conveniently, the periphery of the circular metal panel is provided with a curl, preferably an outwardly facing curl, adapted to be received in the inwardly facing channel . Preferred embodiments of the invention will now be described, by way of example and with reference to Figs. 2 to 11 of the accompanying drawings. Of those Figures :- Fig.2 shows, on an axially directed cross-section, a first package employing a closure/container combination in accordance with the invention, the closure having a vacuum release facility;

Fig.3 shows detail of the closure/container engagement to a larger scale than Fig.2;

Fig.4 likewise shows the vacuum release facility of Fig.2 to an enlarged scale; Fig.4A shows the coated metal sheet of the closure;

Fig.5 shows another form of vacuum release facility;

Fig.6 shows a further form of vacuum release facility;

Fig.7 shows yet another form of vacuum release facility;

Figs.8 and 9 are views corresponding to Fig.3 of the closure/container engagements of respective further packages in accordance with the invention but employing essentially all-metal closures rather than the composite metal/plastics closure of Fig.2;

Fig.10 shows a further form of vacuum release facility, shown in plan view; and

Fig.11 is a cross section through the line A-A in Fig.10. Referring firstly to Figs. 2 to 4 and Fig.4A, a package of a food product (not shown) has a metal container 10 with a tubular side wall 12 extending upwardly from a closure (not shown) at its bottom end. The base closure may be formed integrally with the side wall, or it may be separately attached at a peripheral seam.

The free top end of the container 10 defines the container mouth, and is necked inwardly at an inwardly and upwardly inclined shoulder 14. Above the shoulder the container mouth is formed by a reduced diameter, generally cylindrical portion 16 which carries an outturned peripheral curl 18 of elongate form.

As is clearly shown in Fig.3, the top of the curl 18 is generally semicircular in cross-section and forms a rounded free edge or rim 20 for the container 10. Below this rim the curl tapers downwardly and inwardly at an angle of approximately 15° to the vertical, that is to say, to the central axis XX of the container and closure. This tapering, generally frustoconical, portion 22 in turn carries the base 24 of the curl, which extends inwardly substantially as far as the cylindrical portion 16 of the container neck. The base is curled inwardly so as to form a substantially semi-circular (in cross- section) lower annular termination of the curl 18.

The container free edge 26 may, as shown, be located substantially at the innermost point of the base. Alternatively, and as shown in broken lines, the base may be continued generally upwardly and outwardly on a generally circular locus to the free edge. The latter arrangement may be preferred because the free edge, which is liable to corrosion, is hidden from view within the interior of the curl 18. As a further modification, illustrated by dash-dotted lines, the free edge may be provided by the bottom end of the frustoconical portion 22, there being no base 24 as such.

The vacuum closure 30 by which the container 10 is closed onto a product is of composite construction, having a central, generally metal closure disc 32 and a moulded band 34 of a suitable plastics material into which the disc is fitted. The band has a generally cylindrical body portion 36 and an inturned annular flange 38 formed at one end of the body portion, the top end as shown.

An inwardly projecting snap-engagement bead 40 is formed around the interior of the band 34 intermediate the ends of the body portion 36. With the flange 38 the bead forms an inwardly facing channel 120. At the periphery of the disc 32 is a short, downturned, cylindrical flange 42 terminating in a curl 121 at the end of which is the free edge 43. The curl 121 is received and held captive in the channel 120.

The disc 32 is pressed from tinplate, TFS (tin free steel), blackplate, aluminium or other suitable metal sheet. As shown in Fig.4A, it is lacquered on both its surfaces. In that Figure the metal substrate is denoted 44, the upper and lower lacquer layers being denoted 45, 46 respectively. The two lacquers may be the same, or they may differ.

A vacuum release facility generally denoted 48 is formed in the centre of the disc. As shown in detail in Fig.4, a shallow circular depression 50 having a flat base 52 and a sloping side wall 54 is formed in the disc 32, and a central hole 56 is formed through the disc in the centre of the base 52. The hole is formed by piercing with an upward direction of movement (in relation to the disc as shown) with the result that an upstanding and convergent chimney 58 is formed around the hole.

A quantity of a polymeric material 60 such as a plastisol is located in the depression 50 as shown. The material 60 is deposited into the depression 50 when in flowable form, and subsequently caused or allowed to harden. Before it hardens some of the material penetrates the hole 56 and forms a mushroom head 62 in free space on the underside of the disc.

Fig.4 shows the material 60 after it has hardened. It will be seen that the mushroom head 62 is joined through the hole 56 with the bulk of the material, which is received in, and fills, the depression 50. The material accordingly forms a plug which closes the hole and is held releasably captive on the disc by the mushroom head beneath. The plug is generally denoted by the reference numeral 64 in Figs. 2 and 4.

The material 60 and the lacquers 45, 46 are selected so that the plug 64 adheres with a predetermined peel strength to the upper and lower lacquers 45, 46 where it is in contact with them. The adhesion is sufficient to ensure that in the closed package the plug seals the hole hermetically in a reliable manner, so that a partial vacuum can be retained within the package as required. The adhesion is sufficiently weak, however, to enable a consumer wishing to open the package to separate it entirely from the disc, leaving the hole 56 open for air to pass into the package headspace. The chimney 58 presents a smoothly curving constriction which progressively compresses the mushroom head 62 until it can pass through the hole in the upward direction.

The plug 64 is removed by the user by inserting a finger nail or sharp implement under its free edge, and levering the plug upwardly. For that purpose it may be preferred for the material 60 to be adherent to the lower lacquer 46, but non-adherent to the upper lacquer 45.

Fig.4 illustrates a modification of the formation of the plug 64 in which the mushroom head 62 is shaped by a forming tool 66 which is held in contact with the underside of the disc 32 while the material 60 is being located in position. As shown, the tool 66 may have a

recess 68 which is shaped to form the mushroom head as required; alternatively, it may have a flat upper surface so as to form the material 60 with a lower surface which is generally flush with the lower surface of the disc. It may be heated if required.

In a further modification of the formation of the plug 64, which also is illustrated in Fig.4, the plug is formed by compression-moulding a slug of a suitable molten polymeric material which is placed in the depression 50. A compression-moulding tool 70 capable of making a peripheral seal with the disc around the depression is brought down against the slug and redistributes the material 60 as required to form the plug. If desired, the compression-moulding tool may be used in conjunction with a forming tool 66 as described in the last paragraph.

Fig.5 shows a further vacuum release facility which is similar in general arrangement to that of Fig.4 but which employs a different mode of vacuum release operation.

As with the facility of Fig.4, the vacuum release facility of Fig.5 has a unitary plug of plastisol material 60 disposed in a shallow, generally frustoconical depression 50 which is formed in the closure disc 32, and an upstanding chimney 58 is formed through the closure disc within the depression. It is to be understood that the material 60 is non-adherent to the upper surface of the disc, but adherent to its lower surface (including the inside of the chimney) . Within the chimney 58 the material 60 has a lower surface 106 which is generally flush with the surrounding lower surface 107 presented by the disc. A hot forming

tool similar to the forming tool 66 of Fig.4 and possibly having a flat upper surface may be used for this purpose. The tool may be already in position against the disc surface 107 when the material 60 is flowed into the depression 50, although for more viscous materials it may be appropriate to move the tool against the disc surface some time after the material has been applied.

The height H and internal width W of the chimney 58 are selected in relation to the physical characteristics of the material 60, in particular its tensile strength. As illustrated in Fig.5, when the user exerts an upward force on the plug of material for the purpose of releasing the container headspace vacuum, the material 60 ruptures internally along a generally conical break line indicated by broken line 108, leaving an annular part 109 which remains attached to the disc by adhesion with the inside surface of the chimney 58.

The relationship of the dimensions of the chimney 58 and the characteristics of the material 60 is such that the break line 108 extends to and intersects the lower surface 106 of the material. Accordingly, when the plug is removed with the exception of its annular part 109, a substantially circular hole of accurately predictable size is left within the chimney for vacuum release. Another form of vacuum release facility in accordance with the invention employs an injection- moulded plastics bung 64 (Fig.6) which is integrally formed with a rivet 72 on one side, the underside as shown. The rivet is forced through a hole 56 formed in the disc 32, and its projecting end is upset as shown so as to hold the bung releasably captive until opening is required. If desired, the bung may have an integral

finger ring 74 to assist grasping by the user; alternatively the bung may be designed for removal using an implement. In the closure 30 the bung preferably projects no higher than the annular top edge of the plastics band 34 - see Fig.3.

Fig.7 shows a further vacuum release facility which may be used in a container/closure combination in accordance with the invention and is as disclosed in US patent specification No. 5275679 previously mentioned. As in the arrangements of Figs.4 and 5, a plastisol or similar material is again received in a shallow depression 50 which is formed in the closure disc 32 and has a central hole 56. In Fig.6 a thin film 80 with which the plastisol material is compatible is formed over the hole on the underside of the disc before the plastisol material is deposited. Within the area of the hole the plastisol and thin film materials unite intimately with one another with the result that, when the plastisol material is removed in order to destroy the vacuum in the package, the part 82 of the film where it underlies the hole is torn away at the same time, thereby leaving a desired passage for air to flow. The film 80 and the material 60 are formed in successive and essentially separate stages of operation, and a one-stage operation such as involved in the formation of the vacuum release plugs of the embodiments of Figs. 1 to 5 is preferred. In Fig.7 the metal of the disc 32 is formed with upper and lower lacquers 45, 46 the upper lacquer of which is nonadherent to the plastisol material 60, but the lower lacquer of which is adherent to the material of the film 80.

Reverting now to Figs. 2 and 3, the closure 30 is assembled by forcing the disc 32 past the snap-engagement bead 40 until it, in particular the flange 42 and curl 121, adopt the position shown in relation to the band 34. In that position the lid is firmly held against relative axial movement between the flange 38 and the bead 40. The disc has an annular liner 84 of a flowed-in plastisol sealing material formed, as shown, on its underside in the corner formed by its flange 42. The closure is fitted onto the container 10 by downward movement at a time when the product in the container is hot or when steam exists in its headspace. The downward movement of the closure forces the closure bead 40 resiliently over the curl 18 of the container, so that the closure comes to rest in approximately the relative position shown, with its liner 84 making sealing engagement with the container curl. The package is thereafter cooled, possibly after pasteurisation or sterilisation, with the result that condensation of water vapour and thermal contraction of the food product generate a partial vacuum in the container headspace. Some further downward movement of the closure on the container may occur in response to this partial vacuum. Also, contraction of the body portion 36 of the closure will usually occur as the package cools, again tending to cause further settling of the closure on the container. In this condition the package is marketed for retail sale.

In order to remove the closure the consumer first operates the vacuum release facility as previously described, so destroying the vacuum in the consumer headspace. The free edge 86 of the band 34 is spaced

above the container shoulder 14 as shown, and an implement such as a coin or the handle of a spoon may then be inserted in the space and used to lever the closure over the curl 18 of the container. During this movement the closure bead 40 rides up the curl 18, the small taper angle of the frustoconical portion 22 causing progressive expansion of the bead 40 and of the body portion 36 of the band 34 until the bead can move clear of the curl. In order to reduce the resistance presented by the band to this movement the bead may, if desired, be interrupted by one or more slits or gaps spaced around its periphery, as illustrated by the broken line 88 which indicates the outer end or face of one such interruption. A feature of the closed package which is evident from Figure 3 is that the closure 30 lies wholly within the cylindrical vertical envelope of the container side wall 12. This assists handling and distribution by ensuring that adjacent packages will not snag against one another and possibly dislodge their closures or break their headspace vacuums.

Fig.8 illustrates the application of the invention to a package the closure of which is substantially of metal, rather than the composite metal/plastics closure 30 shown in Figs. 2 and 3. The closure should be understood as having a vacuum release facility (not shown) formed in its closure panel 90. The facility may be as described above with reference to any of Figs .4 to 7, although other arrangements are possible. In one such arrangement a flexible strip is adhered over a hole formed through the closure panel, and can be peeled away when it is required to destroy the vacuum in the package headspace.

Referring now to Fig.8, the closure 30 is shown in relation to a metal container 10 which is similar to the container of Figs. 2 and 3 and likewise has a cylindrical side wall 12 which is inwardly necked at its open top end. As before, the necked region has a shoulder 14, reduced diameter cylindrical portion 16, and outturned curl 18 extending to the free edge 26 of the container. The closure has a closure panel 90 (as previously mentioned) and a downturned cylindrical flange 92 terminating at an outturned curl 94. The curl lies wholly within the cylindrical envelope of the container side wall 12, for the purpose mentioned above. The closure material may be tinplate, TFS, blackplate, aluminium or other metal, lacquered on one or both its sides.

An annular liner 84 of a plastisol material is formed around the closure 30 at the corner between the closure panel 90 and flange 92. When the closure is fitted to the container (as shown) this liner makes sealing engagement with the container curl both above and to the side of the curl. The liner may be of a foamed material which sets itself to the form of the container curl during thermal processing of the package. As with the other embodiments, opening of the closure by the consumer is achieved after the vacuum release facility has been operated, and may require use of an implement inserted in the space provided between the closure curl 94 and the container shoulder 14.

Fig.9 illustrates the invention as applied to a glass container 10. The closure 30 is essentially of metal and has a downwardly facing, shallow annular channel 95 formed around its closure panel 90. The

channel merges at a radius 96 with a cylindrical flange 97 having an outwardly flared bottom free end at which it is formed with an inturned curl 98. The free edge 99 of the closure as a whole is formed within the curl. A sealing liner 84 is located in the peripheral corner of the closure 30 including its channel 95. The liner is formed by compression-moulding a foamable plastisol compound using a heated punch, in the manner well known for PT (Press-on, Twist-off) closures. By virtue of its foam structure the liner is able to conform itself to the finish of the container to which the closure is applied. In this case the container finish includes an annular top face 100 joined by a radius 101 to a cylindrical bore 102, and a bulbous outer rim 103 joining the top face with a cylindrical outer face 104. It will be seen from Fig.9 that the liner 84 is extended far enough down the flange 97 of the closure to form a latching projection 105 beneath the container rim 103. This projection assists vacuum in the container headspace to hold the closure on the container up to first use, and thereafter provides positive retention for the closure on reclosure after use.

The closure of Fig.9 should be understood as having a vacuum release facility formed in its closure panel 90. The facility may be as described above with reference to any of Figs.4 to 7, but another suitable arrangement may be used if desired. Fitting and use of the closure is generally as described in relation to the previous embodiments. Figs.10 and 11 show an alternative vacuum release design, including a kidney-shaped depression shown generally at 110, comprising a flat base 111 surrounded

by a sloping side wall 112. The base 111 has a first hole 113, having an annular raised side wall defining a chimney 114, the height H of the chimney being approximately 0.5mm and the width W of the chimney being approximately 2.1mm. The chimney 114 and hole 113 are designed to provide an anchor for the plug of plastisol material (not shown) . A second hole 115, also having an annular raised side wall 116, acts as a vacuum release hole. The height H of the side wall 116 is typically 0.2mm and the width W of the hole is typically 1.9mm.

As the vacuum release facility of a vacuum closure in accordance with this embodiment of the invention may be located off-centre on the closure, it may be used in conjunction with a conventional tamper-indicating button,