Abstract:
A pierceable, induction sealable seal for a container opening, the seal comprising a plurality of layers at least one of which is metallic and at least one of which is non-metallic, at least one of the non-metallic layers is complete and in use extends across a container opening to seal it. The area over which the at least one of the metallic layers extends is restricted to the region of the periphery of the seal whereby to facilitate induction sealing to the opening but to remain isolated from product in a container upon piercing of the seal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/GB2011/000643 filed Apr. 26, 2011, which claims priority to British Patent Application No. 1007023.3 filed on Apr. 27, 2010. The entire disclosure contents of these applications are herewith incorporated by reference into the present application. 
     FIELD OF THE INVENTION 
     The present invention relates generally to a seal for a container and particularly to a seal which is intended to be pierced in order to allow access to product in a container. 
     BACKGROUND 
     It is known to provide container seals for preserving the contents of the container prior to opening. In many cases the seal is pierced to gain access to the product. When the seal is pierced, the material of the seal may come into direct contact with the product. Depending on the type of seal there may be certain layers which must be present in order to provide it with certain properties, such as the ability to be sealed to the rim of the container and the ability to prevent ingress and/or egress of material to and from the product. These requirements may conflict with the desire to avoid contact of certain materials in the seal with the product. 
     SUMMARY 
     The present invention seeks to address the problems with known container seals. 
     According to a first aspect of the present invention there is provided a pierceable, induction sealable seal for a container opening, the seal comprising a plurality of layers at least one of which is metallic and at least one of which is non-metallic, at least one of the non-metallic layers is complete and in use extends across a container opening to seal it, in which the area over which the at least one of the metallic layers extends is restricted to the region of the periphery of the seal whereby to facilitate induction sealing to the opening but to remain isolated from product in a container upon piercing of the seal. 
     By having one or more layers with incomplete coverage, the material from the seal which is torn and pushed down during piercing can be controlled. Therefore material which may be incompatible with a product in a container can be present but isolated from the product following piercing. One of the layers is complete. In other words, the layer may extend over substantially the entire area of the seal when viewed in plan or at least over the entire area of a container opening. 
     The restricted layer(s) may be restricted to the region of the periphery of the liner. This is particularly useful where the layer(s) are involved in fixing the seal to a container rim and/or sealing because they may only be required at the periphery. 
     The restricted layer(s) may be formed as an annulus. The annulus may therefore define a piercing zone at its centre which does not include any material from the restricted layer(s). 
     The seal may include a layer of polyethylene terephthalate (PET). The layer of PET may be complete. 
     The liner may include a layer of aluminium. Aluminium or a similar conductive material may be required for certain applications, such as when the seal will be induction welded to the container rim. The layer of aluminium may be incomplete. 
     The seal may include a layer of foam such as foamed polyethylene or polypropylene. The layer of foam may be incomplete. 
     The layers may be secured to each other by adhesive, wax or the like. In use one or more of the layers may separate from each other. For example, some layers may remain on a container and others may be retained in an associated closure. 
     The seal may be formed as a liner for a container closure. The closure may be a self-piercing closure, with a mechanism for piercing through the seal. 
     The seal may be formed as an induction seal liner, for example a heat induction sealed liner. 
     According to a further aspect there is provided a seal as described herein in combination with a container. 
     According to a further aspect there is provided a seal as described herein in combination with a closure. The closure may be a self-piecing closure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a section of a seal formed according to an embodiment of the present invention; 
         FIG. 2  is a bottom perspective view showing the underside of the seal of  FIG. 1 ; 
         FIG. 3  is a section of the seal of  FIGS. 1 and 2  shown fitted into a closure as a liner; 
         FIG. 4  is a section of the closure/seal of  FIG. 3  shown attached to a container neck; 
         FIG. 5  is a section of the closure/seal/container of  FIG. 4  following first removal of the closure; 
         FIG. 6  is a section of the container/seal of  FIG. 6  following piercing of the seal; 
         FIG. 7  is a side elevation of a seal formed according to an alternative embodiment of the present invention; 
         FIG. 8  is a top perspective view of the seal of  FIG. 7 ; 
         FIG. 9  is a side view of the seal of  FIGS. 7 and 8  shown attached to a container neck rim; 
         FIG. 10  is a partial section of the seal of  FIG. 9  shown following piercing; 
         FIG. 11  is a partial section of a closure incorporating a liner formed according to the present invention; 
         FIG. 12  is a perspective section of the closure of  FIG. 11 ; 
         FIG. 13  is a further section of the closure of  FIG. 12 ; 
         FIG. 14  is a section of a body part of the closure of  FIG. 11  shown in an unactivation position; and 
         FIG. 15  is a section of the part of  FIG. 14  shown in an activated position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1  there is shown a disc-shape seal generally indicated  10 . The seal  10  comprises a layer of polyethylene terephthalate (PET)  20  and a layer of foam  30  secured to each other by a layer of adhesive  40 . 
     The PET layer  20  is complete, in other words it extends completely over the area of the seal in plan. The foam layer  30  is formed as an annulus secured to the underside of the PET layer. Accordingly the layer  30  is incomplete and defines a central region  22  of the PET layer over which the foam layer  30  does not extend. 
     Referring now to  FIG. 3 , the seal  10  is shown to be formed as a liner and  10  is secured into the top of a closure generally indicated  50 . The closure  50  comprises a disc-shape top plate  60  with a cylindrical skirt  70  depending from the periphery thereof. The skirt  70  includes screw thread formations  80 . The seal  10  is weakly adhered to the underside of the top plate  60  by an adhesive layer  15  on top of the PET layer  20 . 
     In  FIG. 4  the closure  50  is shown applied to a container neck  90 . The closure is applied using screw thread formations  95  on the neck corresponding to the formations  80  on the closure. 
     To secure the seal  10  to the container rim  97 , heat curable adhesive  25  is applied to the rim before application of the closure. Subsequently heat is applied to the top plate  60  to cure the adhesive which bonds the foam layer  30  to the rim  97 . 
     With the closure fully applied to the liner, in particular the foamed layer  30 , is compressed and forms a seal around the container neck  90 . The heating process also weakens/removes the adhesion between the PET layer  20  and the top plate  60  by at least partly melting the adhesive layer  15 . 
       FIG. 5  shows the closure and container neck following first removal of the closure. Because the adhesive layer  15  is weakened/removed, when the closure  50  is unscrewed the seal  10  remains on the container neck  90 . 
     When access to the contents of the container  90  is required the seal must be pierced. In this embodiment, the seal is pierced by a separate tool  95  as shown in  FIG. 6 . It will be seen that as the central region of the seal is torn by the tool it will be pushed into the mouth of the container. 
     Because the foam layer  30  is restricted to the periphery of the seal, this layer will not be pushed into the container mouth and will not potentially come into contact with the product. Therefore only the PET layer  20  will potentially contact the product  85 . 
     Referring now to  FIGS. 7 and 8  there is shown a seal  110  formed according to an alternative embodiment. The seal comprises a layer of PET  120 , a layer of aluminium foil  125  and a layer of foamed polyethylene  127 . The layer of PET  120  is formed as a complete disc, whereas the aluminium and foam layers  125 ,  127  are formed as rings which extend around the peripheral region of the PET layer. 
     The PET layer is present as a barrier layer, to prevent ingress of gases which are deleterious to the container product. 
     The foam layer is present to form a physical seal around the container rim when a closure is applied. 
     The aluminium layer is required to attach the seal to a container rim. 
     The seal is formed as a heat induction sealed liner therefore in the first instance is fitted into a closure, which in this embodiment is a self-piercing closure (not shown). In use the closure is fitted onto a container neck so that the PET layer  120  abuts and fits around the top of the container neck rim  195  as shown in  FIG. 9 . Thereafter the seal is secured to the container rim by a heat induction process. The induction process requires the aluminium layer to facilitate bonding of the PET layer to the container rim. 
     Subsequently, when the self-piercing closure is activated the seal will be pierced. However, because the aluminium and foam layers  125 ,  127  are restricted to the periphery of the seal, only the PET layer is in fact pierced and pushed down into the mouth of the container as shown in  FIG. 10 . Therefore, only the PET layer  120  will come into contact with product in the container. 
     Referring now to  FIGS. 11 to 13  there is shown a closure generally indicated  210 . The closure  210  comprises a generally cylindrical base  220 . 
     The closure  210  is intended to be fitted to a container neck (not shown) which at its open end is sealed by a laminar disc-shape liner  260  which in this embodiment will be induction heat sealed into position. 
     The base  220  comprises a cylindrical sidewall  221  which includes internal screwthread formations  222  for engaging corresponding external screwthread formations on the container neck. 
     At the closed end of the sidewall, a platform  229  extends radially inwardly. From the inner edge of the platform  229  an upstanding collar  223  is provided. At the opposite end of the collar  223  to the platform  229  a sealing portion  224  extends radially inwardly and defines at its centre an aperture  225 . Approximately half way along the portion  224  an annular sealing leg  226  depends and terminates with a sealing bead  227 . The arm  224  terminates with a wedge-shape portion  228  which includes a downwardly depending section. 
     A self-closing valve  270  is provided. The valve  270  is of standard construction and briefly comprises a generally triangular section support ring  271 , a J-shape connecting wall  272  and a generally disc-shape concave valve head  273 . 
     The valve  270  is fitted into the base  220  so that the segment  271  abuts against the portion  228  and the opposingly inclined surfaces allow for a stable interaction. 
     A piercing member  280  is provided. The member  280  is generally annular and comprises a retention band  281  from which depends a cutting region comprising a plurality of teeth  282 . At the end of the collar  281  opposite the teeth  282  a bead  284  projects radially inwardly. Extending parallel to the collar  281  on the opposite side of the teeth  282  is a retention jaw  285 . In use, with the self-closing valve assembled into the base, the member  280  is snap fitted on to the base so that the bead  284  clips over the bead  227 . At the same time, the jaw  285  engages the segment  271  so that it is held firmly between the portion  228  and the jaw  285 . For this purpose the jaw  285  includes an inclined surface oppositely inclined to that side of the segment  271 . 
     A liner  260  is provided and fits into the closure under the platform  229 . The liner includes: an annular layer of foamed polyethylene  207  which seals against the platform; an annular layer of aluminium foil  205  attached to the layer  207 ; and a disc-shape layer of PET  202  attached to the layer  205 . 
     In use the closure  210  is applied to a container neck so that the liner  260  contacts the neck rim. The liner  260  can then be induction sealed onto the neck rim. 
     The neck  223  is formed as a flexible membrane so that it can be pushed down from the position shown in  FIG. 14  to the position shown in  FIG. 15 . In doing so, the piercing member  280  is pushed down to contact the panel  260 . This pierces only the PET layer  202  of the panel because the layers  207 ,  205  are confirmed to the peripheral region not contacted by the piercing member. Subsequently product can flow from the container under the control of the self-closing valve  270 .