Abstract:
The present invention relates to a closure ( 1 ) for an easy opening container comprising a support and a foil ( 3 ) adhered to the support, which foil is provided with a tab ( 4 ) folded on to the foil, wherein the foil comprises a central concave section ( 5 ) and at least a flat section ( 6 ) beneath the tab, where optionally the tab is adhered to the flat section, and to a container comprising such closure.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a closure for an easy opening container and to a container provided with such closure. 
     Description of Related Art 
     Easy opening closures are used for closing an opening of a container with a foil, such that relatively easy by removing the foil the content of the container will become available to the consumer. The foil is generally relatively vulnerable and is released from its container support by gripping a tab, which is connected to or integral with the foil. Lifting the tap and exerting relatively low force will result in a detachment of the foil from the container support. After filling and closing the container with the easy opening foil, the foil is protected by a cap which overdoses the foil and is connected to the container. In use, the user first removes the protective cap and subsequently the foil by gripping the tap and peeling off the foil. 
     Such easy opening containers are also used for goods, such as food, that are to be subjected to a heat treatment after closing the container. Generally, the tab is adhered to the foil and thereafter the foil is provided with the desired shape and form. This may negatively influence the adherence of the tab to the foil. 
     Over pressure build up in the container during heat treatment, for instance a sterilization process will result in an outward bulging of the easy opening foil, even outside the confinement of the container. This may result in damage of the foil and/or damage to the tap. Eventually, this may result in a failure of the foil or that the tap is no longer available for opening the container by peeling of the foil. 
     This risk for damage to foil and/or tap of an easy opening container is relatively high, when such easy opening containers are subjected to a heating treatment during which the containers are transported through the heat treatment apparatus, such as a retort apparatus, following conveyors and/or guiding rails. 
     SUMMARY OF THE INVENTION 
     The present invention has for its object to provide a closure and a container provided with an easy opening foil which have a substantially reduced risk for damage of the foil and/or the tap during and after a heat treatment. 
     Accordingly, the present invention provides a closure for an easy opening container comprising a support and a foil adhered to the support, which foil is provided with a tab folded on to the foil, wherein the foil comprises a central concave section and at least a flat section beneath the tab. The tab is thus first adhered to the flat foil section underneath. Then the foil is shaped and provided with the concave form leaving undisturbed the flat foil section during the forming process (no shearing of the glue during the forming) In this manner, the tab will stay better attached to the foil and subsequently during all the steps of the use of this end (during heat treatment, conveyors, rails, handling) and the chance to have the tab damaged will be reduced. Obviously, the flat section can have different forms like annular and exocentric flat section. 
     Due to the presence of a central concave section (extending inwardly of the container) and a flat foil section beneath the tab, the foil and the tab will move outwardly to such extent, that it can extend beyond the confinement. Dependant on the diameter of the container, it could bulged out up to about 20 mm on a large diameter. Preferably, the tab and foil substantially do not extend beyond (the confinement of the closure. In other words, foil and tab do not extend outside the confinement of the closure and therefore is the risk of sticking or hooking to parts of the apparatus substantially avoided. The concave section will bulge outwardly and when in contact with the tab, the tab will follow the outward movement of the foil. However, due to the presence of the flat section beneath the tab, this part of the foil will move to a lesser extent outwardly and thereby avoids the tab of projecting beyond the confinement of the closure. 
     According to a preferred embodiment, the tap is folded onto the concave section. This will increase the distance of the tap to the confinement of the closure and therefore further reduces a risk of projecting beyond the confinement of the closure. 
     The outward bulging of the concave section is further reduced, and the making of the foil is further simplified if, according to another preferred embodiment of the invention, the flat section extends over the circumference of the support. The outward movement of the concave section is further reduced at the same relative overpressure when the flat section extends radially inwardly over and beyond the support. That is, the width of the flat section is larger than the support to which the foil is adhered. Practically it is preferred that the flat section extends over a length L of about 1-15 mm, such as 2-12 mm, in particular 3-10 mm over and beyond the support. 
     In order to further reduce undesired lifting and extension of the tab beyond the confinement, it is further preferred that the tab is adhered to the foil via the flat section. According to a preferred embodiment, the tab is adhered to the foil by adhesive. This has the advantage that the adhesive is applied and present on the flat section and the tab will remain at this location undisturbed when thereafter the concave central section is formed in the foil. Adhesive will not be transported to the outside of the space between the flat section and the overlaying tap, because this part of the foil is not disturbed when forming the central concave section. According to another alternative embodiment the tab is adhered to the foil by mechanical structure. This means that the flat section and the tap are entangled which resists separation of the tab from the flat section. Obviously, such mechanical structure is preferably formed and applied in a flat section of an undisturbed part of the foil. 
     Preferably the free end of the tab does not contact the foil thereby providing an elegant finger access. 
     The construction of the closure according to the invention is such that at a pressure build up of about 0.1-2.5 bar the tab and foil remain within the confinement of the support. 
     The present invention is applicable for easy opening foils independent of the form of the support to which the foil is adhered. According to a preferred embodiment this support is part of a ring which is to be connected to a container body. Accordingly, the foil can be adhered to a ring support. Subsequently, the ring with the adhered foil is applied to a container body after filling the container body via the same opening. It is also possible, that the support is not present in a separate ring, but is formed at the free end or in the wall of the container body. It is then possible that the container is first filled and subsequently the foil applied, or that the container after application of the foil is filled from the other open container body end. 
     A foil to be used in relation to the present invention may be made of any suitable material which may be characterized as a foil, because it has a thickness of about 0.02 to 1.0 mm, preferably 0.05 to 0.5 mm. The foil may be provided with a surface structure or be imprinted. The material of the foil may be metal, such as aluminium, or plastic, such as polypropylene, or may have the form of a metal foil provided with a plastic laminate. A further aspect of the present invention relates to a container provided with a closure as defined and characterized herein before. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Mentioned and other features and characteristics of the closure and container of the present invention will be further illustrated with reference to particular embodiments which are given for illustrative purposes without any intention for limitation of the present invention. In that respect reference will be made to drawings, wherein: 
         FIG. 1 : a prospective view of an easy opening closure according to the invention; 
         FIG. 2 : a top view of the closure of  FIG. 1 ; 
         FIG. 3 : a side view of the closure of  FIG. 1 ; 
         FIG. 4 : a cross-section of the closure of  FIG. 1 ; 
         FIG. 4A : the closure in the overpressure status; 
         FIG. 5 : at a larger scale a cross-section over the line V-V in  FIG. 2 ; 
         FIG. 6 : at a larger scale a cross-section over the line IV-IV in  FIG. 2 ; 
         FIG. 7 : a cross-section corresponding to  FIG. 5  showing the bulging or foil and tap due to over pressure; 
         FIG. 8 : another embodiment of the closure according to the present invention; 
         FIG. 8A : a cross-section similar to  FIG. 5  of the closure of  FIG. 8 ; and 
         FIG. 9 : shows a perspective view of another closure according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a closure  1  according to the invention. The closure  1  comprises a ring  2  to which is adhered a foil  3 . The foil  3  comprises a tab  4  which is integral with the foil  3  and is folded over and onto the foil  3 . The foil further comprises a central concave section  5  surrounded by an annular flat section  6 . 
       FIG. 2  shows that the tab  4  has a folded part  7  connected to an intermediate tab part  8  and a free end tab part  9 . The intermediate tab part  8  extends over the annular flat section  6  and the fee end tab part  9  extends over the central concave section and is folded towards this section by a fold line  10 . 
       FIG. 3  shows in side view the closure  1  according to the invention with the central concave section  5  extending beneath the lower confinement  11  of the closure  1 . A similar view is given in the cross-section according to  FIG. 4 . 
       FIG. 5  shows more in detail the closure  1  according to the invention. The ring  2  comprises an outer curl  12  which may be seamed onto a body of a container (not shown). The ring has a flat ring support  13  connected to the curl  12  via a ring wall  14 . The flat ring support  13  ends in a curl  15  of which the curl end  16  faces the ring support  13 . The foil  3  at the flat section  6  is adhered to the ring support  13  using adhesive  17 . In stead of adhesive, heat sealing may be used in the alternative. The tab  4  with its intermediate tab part  8  is adhered to the foil  6  using adhesive  18 . It is noted that the flat section  6  has a very large angle due to the slanted position of the flat ring support  13 . The tab  4  follows the form of the foil  3  because the structuring of the foil  3  takes place after the bending over and adherence with adhesive  18  of the tab  4  to the foil  6 . 
       FIG. 6  shows the adherence of the foil  3  with its flat section  6  to the ring support  13  using adhesive  17 . 
       FIGS. 4A and 7  show the shape of the foil  3  and the tab  4  when pressure build up occurs in a container provided with a closure  1  according to the invention. It is shows that the foil  3  bulges outwardly and transformed the concave section into a convex section and that with this transformation also moved the tab  4 . However, the foil  3  and in particular the free end  9  of the tab  4  remained within the confinement  19  of the closure  1 . At larger diameter the free end  9  and the tab  4  may extend beyond the confinement as well, if so desired. 
       FIGS. 8 and 8A  show another closure  20  according to the invention. A container body  21  is provided with a support  22  ending in a curl  23  which is counter clockwise curled such that the curl end  24  faces the curl  23 . A curl gap  25  is closed off by the foil  26  which is adhered to the curl  23  and to the support  22  by adhesive  27  (heat sealing may also be used). 
     According to the invention, the foil  26  is provided with an annular flat section  28  extending over a length L of about 6 mm beyond the support  22  and the curl  23 . The foil  26  is further provided with a concave central section  29 . The tab  38  which is integral with the foil  26  is folded over the flat section  28  and connected thereto using adhesive  27 . The tab  38  is further comprising a free tab end  30  which is folded along the concave foil section  29 . After having been subjected to a heat treatment and after balancing the internal pressure again by cooling, the free end  30  will have slightly separated from the concave central section  29  thereby providing a finger access  31 . 
       FIG. 9  shows a closure  32  according to the invention. The closure  32  comprises a ring  33 . The foil  34  is adhered to a non-shown ring support using adhesive. The foil  34  comprises an integral tab  35  which is folded over and on the foil  34 . 
     The foil  34  comprises a flat foil section  36  extending beneath and lateral of the tab  35 . This implies that the concave central foil section  37  extends almost over the entire circumference except for the flat foil section  36 . Still, this closure with the foil and tap according to the invention and remain within the confinement of the ring  33  during over pressure build up in the container to which the closure  32  connected to.