GB2237259A

GB2237259A - Container closure

Info

Publication number: GB2237259A
Application number: GB8915787A
Authority: GB
Inventors: Keith Longstaff; John Stanley Simmons; Keith West
Original assignee: CMB Foodcan PLC; CMB Packaging UK Ltd; Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1989-07-10
Filing date: 1989-07-10
Publication date: 1991-05-01
Anticipated expiration: 2009-07-10
Also published as: AP9000191A0; ATE100405T1; DE69006124T2; ZA905378B; EP0408268B1; DE69006124D1; GB2237259B; AP168A; EP0408268A2; EP0408268A3; GB8915787D0

Description

1 CONTAINER CLOSURE This invention relates to closures for cans or like

containers, and more particularly to closures of a kind comprising a ring portion adapted for attachment to a container body and having a diaphragm sealingly fixed to the ring to complete the closure.

British Patent No. 1274542 (Sandherr) describes containers having closures comprising a ring and a diaphragm adhered to the ring by an adhesive that permits peeling of the diaphragm from the ring to give access to the contents of the container. In one embodiment Sandherr provides a ring having a peripheral portion adapted for attachment to a container body, an annular plug portion extending from the peripheral portion to enter the container body, a flat annulus extending radially inwards from the plug portion and a frustoconical annulus depending from the interior of the flat annulus to terminate at the container body. The diaphragm is peripherally adhered to the flat annulus and spans the ring to serve as a closure removable by a peeling action. Whilst the frustoconical annulus serves to guide powder products out of the container, its terminal edge is inside the container and therefore at risk of corrosion by any aggressive substance packed in the container.

In a second embodiment Sandherr describes a ring having a peripheral portion, an annular plug portion depending from the peripheral portion, a frustoconical annulus extending upwardly and inwardly from the annular plug portion and a flat annulus extending radially outwards from the frustoconical annulus.

The diaphragm is adhered to the flat annulus, the free edge of which is at risk of atmospheric corrosion.

British Patent No. 2022474B describes a process for making peripheral rings for the end of cans. These rings are cut from a lacquered sheet and formed with an inwardly extending portion whose inner part is turned back on itself away from the interior of the can to form an annular level flange overlying the outer part of the inwardly extending portion. A diaphragm with a tearback tab is bonded to this flange. In this case too, the cut edge of the ring is open to the atmosphere and thus at risk from atmospheric corrosion.

According to one aspect of the present invention there is provided a closure for a can or like container comprising a ring for attachment to a container body and a diaphragm bonded to the ring and extending across the opening of the ring, the ring comprising a peripheral formation adapted for engagement with a container body, and an annular flange portion extending radially inwardly from the peripheral formation to support the. diaphragm bonded to the ring, wherein the annular flange portion comprises a level annular region and an annular curl extending inwardly from the level annular region and turned back on itself to define the opening of the ring and to overlie the level annular region and to present a bonding zone for the diaphragm, characterised in that the said level annular region is spaced radially from the peripheral formation by a second, outer annular region which is axially spaced from the inner annular region by a step portion so as to present an outer bonding zone for the diaphragm concentric with the first-mentioned, inner, bonding zone.

Preferably the inner and outer bonding zones are both level and are coplanar.

1 1 A closure in accordance with the invention has the significant advantage over the closure described in British Patent Specification No. 2022474B in that the cut raw edge of the ring overlying the inner level annular region is protected both from the contents of the container and from the atmosphere since it is contained in an annular space sealed by the diaphragm (secured to bonding zones which occur on either side of the cut edge) on one side and the inner level flange portion on the other. It is thus protected from atmospheric corrosion and from aggressive contents of the container. Further the cut edge presents no risk to a user of the container since it is protected by the step portion.

If desired, the diaphragm has a pull lug extending from its periphery and the bond at the bonding zones between the diaphragm and the ring permits removal of the diaphragm by a peeling action. The diaphragm may be bonded to the ring by adhesive. Alternatively, the diaphragm may be cut from a laminate of common metal and a polymeric film bonded by application of heat and pressure to the diaphragm to seal the diaphragm to the ring at the bonding zone.

In another case, the ring may be stamped from a laminate of common metal and a polymeric film, or prelacqueredcommon metal, and the diaphragm is bonded to said film or lacquered surfaces at the bonding zones. Preferably, the diaphragm is cut from a laminate of aluminium and a polymeric film that will adhere to a receptive surface coating on a ring stamped from precoated tinplate or electrochrome coated steel (called TFS).

According to another aspect of the present invention there is provided a container comprising a container body and secured to its peripheral rim a ring for supporting a diaphragm for closing the container, the ring comprising a peripheral formation engaging the container body, and an annular flange portion extending radially inwardly from the peripheral formation to support a diaphragm bonded to the ring, wherein the annular flange portion comprises a level annular region and an annular curl extending inwardly from the level annular region and turned back on itself to define the opening of the ring and to overlie the level annular region and to present a bonding zone for the diaphragm, characterised in that the said level annular region is spaced radially from the peripheral formation by a second, outer, annular region which is axially spaced from the inner annular region by a step portion so as to present an outer bonding zone for the diaphragm concentric with the first-mentioned, inner, bonding zone.

According to a further aspect of the present invention there is provided a method of manufacturing a supporting ring for a container closure, the method comprising cutting an annular blank having a central opening from sheet metal, then stamping the annular blank to form therein a peripheral formation and extending radially inwardly therefrom a stepped annular ledge having inner and outer parts and terminating in an annular trough and an upstanding annular wall, and then folding the upstanding annular wall so as to cause the free edge thereof to overlie the inner part of the stepped annular ledge.

A method of manufacturing a closure comprises the additional step of bonding a diaphragm to the ring at concentric bonding zones presented by the outer part of the stepped annular ledge and the portion of the upstanding annular wall which has been folded to overlie the inner part of the stepped annular ledge.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:- Figure 1 is a plan view of a closure comprising a ring and a diaphragm; Figure 2 is a sectional view of the closure of Figure 1 on line II-II in Figure 1; Figure 3 is an enlarged fragmentary section through the closure of Figures 1 and 2; Figure 4 is an enlarged fragmentary section through a second embodiment of the closure, also showing heat sealing tools; Figure 5 is an enlarged fragmentary section through the ring of Figures 1 to 3 after double seaming to a metal container body; Figure 6 is an enlarged fragmentary section through a third embodiment of the ring after attachment to a container body of spirally wound paperboard; Figure 7 is an enlarged fragmentary section through a fourth embodiment of the ring when double seamed to a container and closed by a diaphragm inside the container and covered by a replaceable plug lid; Figures 8a to 8f show apparatus for manufacturing closures; Figure 9 is an enlarged fragmentary section of the annular flange portion of the ring during manufacture of the closure; and Figure 10 is a cross section through a closure in which the diaphragm is reinforced.

Referring to Figure 1, a closure 1 comprises a ring 2 and a diaphragm 3 secured to the ring 2. The ring 2 is stamped from a common sheet metal such as tin plate or electrochrome coated steel (called TFS in the trade), typically of about 0.26mm thickness, or aluminium alloy sheet. Preferably, the ring surfaces to which the diaphragm is adhered are coated with a protective coating such as an epoxy phenolic lacquer or other polymeric film.

The diaphragm 3 has been cut from a thin sheet material such as an aluminium foil or laminate of aluminium foil/polymeric film or a laminate of polymeric films for suitable barrier properties. A printed paper layer may be included in the laminates to permit presentation of useful indicia.

The following combinations of materials are appropriate:

Rina Coatina Internal External PP laminate g@ PP laminate 09 Epoxy phenolic Epoxy phenolic It with PP with PP Diaphraq Substrate Coatinq (film) Aluminium 99 EVA HDPE EVA dispersion dispersion PP Copolymer PP dispersion PP dispersion of lacquer lacquer Any of above Any of above H Polybutylene PP is polypropylene; EVA is Ethylene vinylacetate; HDPE is high density polyethylene.

Figure 2 serves to show that the diaphragm 3 spans the ring 2 to which it is peripherally attached. As shown in Figures 1 and 2 the diaphragm has a pull tab 4 joining the periphery of the diaphragm at a fold line 4a. The pull tab is used to apply a peeling mode of force to remove the diaphragm 3 from the ring 2.

Figure 3 shows the ring 2 and its connection with the diaphragm 3 in more detail. The ring 2 comprises a peripheral. formation adapted for engagement with a container body and including a flange 6, sometimes called a "cover hook", adapted for double seaming to a can body, an annular wall 7 depending from the inner periphery of the peripheral flange 6, and an annular flange portion extending radially inwards from the wall 7 to support the diaphragm 3. The annular flange portion comprises a first flat annulus 8 extending inwards from the chuck wall 7 and providing an outer annular region, a second flat annulus 9 surrounded by the first flat annulus 8 to provide an inner annular region and offset from said first flat annulus 8 by a step portion 10, and an annular curl 11 extending inwardly from the inner periphery of the second flat annulus 9 to turn back on itself to define the mouth of the ring and thereafter terminating as a third flat annulus 12 which lies over the second flat annulus 9. The diaphragm 3 is sealingly bonded by adhesive at an outer bond zone 5A to the upper surface of the first annulus 8 and by adhesive at an inner bond zone 5B to the upper surface of the third,annulus 12 so that the free edge 112 of the third annulus 12 is totally enclosed from atmospheric or product attack.

In Figure 3 it can be seen that the step portion 10 holds the second annulus 12 at a distance, measured at the central axis of the ring, of about one metal thickness so that the top surfaces of the first annulus 8 and third annulus 12 are 1 substantially flush. Therefore, no bending of the diaphragm material is required to achieve a seal with both annulii.

Various adhesives may be used at the bond zones 5A and 5B. For example, if a strong bond is required, a maleic anhydride modified polypropylene adhesive may be used. If however, a peel bond is required, an adhesive such as polymers of acrylic resin could be used. The outer bond zone 5A is typically lmm wide and the inner bond zone 5B is typically 2mm wide but these dimensions are not critical relative to each other.

Figure 4 shows a second embodiment of the closure 13 in which a ring 14 has been stamped from a laminate of common sheet metal and a polymeric film on both major surfaces of thesheet metal. For example, a laminate comprising an outer layer 15 of polypropylene a middle layer 16 of electrochrome coated steel and an inner layer 17 of polypropylene may be used. The diaphragm 3 could then be made of a laminate of polypropylene 18 and aluminium foil 19 which may be decorated or printed on the outside. Heat sealing of the layer 18 of the diaphragm and to the layer 15 of the ring is achieved by supporting the ring in a lower tool 20 and applying a heated tool 21 to the top surface of the diaphragm. It will be noticed that the metal of the flat annulii 8, 9 and 12 is firmly supported to prevent any distortion of the diaphragm material. Alternative laminates include for example metal sheet and a film of polybutylene or polyethylene terephthalate.

Figure 5 shows the closure 1 of Figures 1, 2 and 3 after attachment to a can body 22 by means of a double seam 23. The second embodiment of the closure, denoted 13 in Figure 4, can also be attached to a can body in like manner.

- 9 However, as shown in Figure 6 the closure may be modified by provision of a modified peripheral flange to permit attachment to a container body 25, having a fibrous wall 27 made of spirally wound paperboard. Figure 6 shows such a modified closure 24 having a peripheral flange 26 crimped onto the fibrous wall 27.

it is intended that the embodiment described in Figures 1 to 5 will be used primarily on containers used for packing aseptically packed products or thermally processed paste-like substances such as pate or dog food. The diaphragm serves as a primary hermetic seal to the container.

However, it is traditional in the packing of dry goods, such as gravy granules or milk powders to use closures comprising a ring closed by a lever plug lid spanned by a diaphragm inside the container - usually held in place by the double seam. To this end, another embodiment of the invention provides, as shown in Figure 7, a closure 28 having a ring 29, a diaphragm 30 inside the container 31, and a plug lid 32 to serve as a useful reclosure after the diaphragm 30 has been cut open. In Figure 7 the ring comprises a first flat annulus 8A, a second flat annulus 9A which is held outwardly offset from the first flat annulus 8A, and a third flat annulus 12A produced by an annular curl 11A as described above. The first annulus 8A is offset from the second annulus 9A so that the third flat annulus 12A and first flat annulus presept flush surfaces to the diaphragm 30 for adhesion or fusion as discussed above. This embodiment differs from those described above in that the annular curl 11A is upstanding above the diaphragm 30 which is then secured to the underside of the annuli 8A, 12A.

Figure 8a shows a tool set 40 comprising upper and lower dies 42, 44 for manufacturing a ring as described above. The upper die 42 comprises a component providing an annular cutting punch 60, a stamping punch 64 and a central cutting punch 66. A holding ring 62 is moveable relative to this component and is located between the cutting punch 60 and stamping punch 64. The lower die 44 comprises an outer cutting ring 68, an annular trough 70, a draw die 72, a stamping die 74 and an inner cutting ring 76.

Reference will now be made to Figures 8a to 8f to describe a process for manufacturing a closure as described above. Figure Sa shows the first tool set 40 comprising upper and lower dies 42, 44. The lower die supports on its outer and inner cutting rings 68, 76 a metal sheet 46 which is to form the ring of the closure. As the upper die is lowered the annular cutting punch 60 cooperates with the outer cutting ring 68 to cut the outer edge of the blank which is to form the ring. The inner edge of the cutting punch draws the outer edge of the blank over the draw die 72 to form the peripheral flange 6. The stamping punch 74 has an inner annular portion 64 which bears against the metal sheet 46 as the inner cutting ring 76 cooperates with the central punch 66 to cut an annular blank from the metal sheet (Figure 8b). The central part 48 is discarded. The upper die 42 is lowered further as shown in Figure 8c until the holding ring 62 holds the metal sheet 46 against the draw die 72. The annular cutting punch 60 and stamping punch 66 are lowered further relative to the holding ring 62 so that the stamping punch forms with the stamping die 74 by stamping from the annular blank a component having a peripheral channel (which will form the peripheral flange 6 of the ring), an annular wall 7 depending from the peripheral flange 6, a stepped annular ledge providing the first and second annuli 8, 9 and the step portion 10 and a i 1 11 trough portion 11 which supports an upstanding central annular wall 12. The first tool set applies initially no holding restraint for the annular blank. Peripheral restraint arises at the bend radii of the peripheral face of the draw die 72 and of the cutting ring 76 which cuts the blank. Also, in contrast to known ring manufacturing methods, the blank is cut prior to any shape forming steps. The upper die component providing the annular cutting punch 60 and the stamping punch 64 is then removed to release the shaped annular blank from the first tool set. As shown in Figure 8e, the peripheral flange portion 6 is then held between the holding ring 62 and the draw die 72. A central punch 56 enters the annular wall 12 to fold that wall to form an outwardly directed curl 11 of which the raw edge terminates at the step portion 10.

Figure 9 illustrates how the curl 11 may terminate in a portion at a slight angle A to the surface of the step portion 10. In this case the material for the diaphragm is chosen to tolerate stretch to drape over the angled portion of the curl.

Finally, Figure 10 shows how the diaphragm 3 may be reinforced against abuse by bonding thereto the central part48 cut during manufacture of the ring 2 with its periphery having been curled.

Claims

1. A closure for a can or like container comprising a ring for attachment to a container body and a diaphragm bonded to the ring and extending across the opening of the ring, the ring comprising a peripheral formation adapted for engagement with a container body, and an annular flange portion extending radially inwardly from the peripheral formation to support the diaphragm bonded to the ring, wherein the annular flange portion comprises a level annular region and an annular curl extending inwardly from the level annular region and turned back on itself to define the opening of the ring and to overlie the level annular region and to present a bonding zone for the diaphragm, characterised in that the said level annular region is spaced radially from the peripheral formation by a second, outer annular region which is axially spaced from the inner annular region by a step portion so as -to present an outer bonding zone for the diaphragm concentric with the first-mentioned, inner, bonding zone.

2. A closure as claimed in claim 1 in which the inner and outer bonding zones are both level and are coplanar.

3. A closure according to claim 1 or 2 in which the diaphragm has a pull lug extending from its periphery and the bond between the diaphragm and the ring permits removal of the diaphragm by a peeling action.

4. A closure according to any preceding claim wherein the diaphragm is bonded by adhesive at the bonding zones.

i 1 1

5. A closure according to any preceding claim wherein the diaphragm is formed from a laminate of common metal and a polymeric film and is bonded by application of heat and pressure to the ring to seal the diaphragm at the bohding zones.

6. A closure according to any of claim 1 to 4 wherein the ring is stamped from a laminate of common metal and a polymeric film or a prelacquered common metal and the diaphragm is bonded to the film or lacquered surfaces.

7. A closure substantially as hereinbefore described with reference to or as shown in the accompanying drawings.

8. A container comprising a container body and secured to its peripheral rim a ring for supporting a diaphragm for closing the container, the ring comprising a peripheral formation engaging the container body, and an annular flange portion extending radially inwardly from the peripheral formation to support a diaphragm bonded to the ring, wherein the annular flange portion comprises a level annular region and an annular curl extending inwardly from the level annular region and turned back on itself to define the opening of the ring and to overlie the level annular region and to present a bonding zone for the diaphragm, characterised in that the said level annular region is spaced radially from the peripheral formation by a second, outer annular region which is axially spaced from the inner annular region by a step portion so as to present an outer bonding zone for the diaphragm concentric with the first-mentioned, inner, bonding zone.

9. A method of manufacturing a supp orting ring for a container closure, the method comprising cutting an annular blank having a central opening from sheet metal, then stamping the annular blank to form therein a peripheral formation and p extending radially inwardly therefrom a stepped annular ledge having inner and outer parts terminating in an annular trough and an upstanding annular wall, and then folding the upstanding annular wall so as to cause the free edge thereof to overlie the inner part of the stepped annular ledge.

10. A method of manufacturing a closure for a container comprising manufacturing a ring in accordance with the method of claim 9 and then bonding a diaphragm to the ring at concentric bonding zones presented by the outer part of the stepped annular ledge and the portion of the upstanding annular wall which has been folded to overlie the inner part of the stepped annular ledge.

11. A method of manufacturing a closure substantially as hereinbefore described with reference to or as shown in the accompanying drawings.

12. Apparatus for manufacturing a supporting ring for a container closure comprising circular upper and lower dies having two sets of cooperating cutting edges, the sets being spaced apart radially so as to cut an annular blank from sheet metal supported by the lower die, and between said sets of cutting edges a set of cooperating stamping surfaces for stamping the annular blank to form a stepped annular ledge terminating in an upstanding annular wall and the lower die having a draw portion over which can be drawn the annular blank to form a peripheral formation.

13. Apparatus as claimed in claim 12 comprising an upper tool to replace said upper die after formation of the stepped annular ledge and peripheral formation in the annular blank and having means for folding back the upstanding annular wall to overlie an inner part of the stepped annular ledge.

-7.

0 - 15

14. Apparatus for manufacturing a supporting ring substantially as hereinbefore described with reference to or as shown in Figures 8a to 8e of the accompanying drawings.

Published 1991 at Tbe Patent 0111ce. State House. 66/71 High Holborn, London WCJR47P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cvnnfelinfach. Cross Kevs. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Marv Crav. Kent.