Container and pressure sealing closure combination
BACKGROUND OF THE INVENTION 
     The present invention relates to closure and container combinations, and more particularly, to closures which utilize the internal pressure of the container contents to effect a seal. 
     Due to cost and safety considerations, it is desirable to fabricate carbonated beverage containers from polyethylene terephthalate (PET). Containers for carbonated beverages made from PET are blow molded in mass quantities from preforms. An advantage of using PET is that it is easily recyclable. However, with present designs, the carbonated beverage container itself is made of PET and includes a threaded mouth which receives a cap made of aluminum. The aluminum closure or cap includes a ring of perforations which forms a line of separation so that, when removed from the container, the cap leaves behind a thin aluminum ring. 
     Accordingly, at some point in the recycling process, it is necessary to separate the aluminum ring from the PET material. This separation step would be eliminated if the entire container-closure combination could be made of PET. Since PET has a different strength than aluminum, it is necessary to design a different closure shape. One example of such a closure and container is disclosed in Wiedmer U.S. Pat. No. 3,825,144. That patent discloses a container closure for sealing bottles having pressurized contents and includes a sealing member having a deformable disk portion with an outwardly concave shape. The disk portion deforms in response to the internal pressure of the container contents. However, such a flexible closure is unsuitable for fabrication of PET, since the internal pressure of a typical carbonated beverage container is not sufficiently great to deform the entire surface of such a closure. 
     Accordingly, there is a need for a container and closure design suitable for a carbonated beverage in which the closure can be made of a flexible plastic material such as PET. Further, a disadvantage with such closures is that they lack means for the gradual release of pressure within the container. As a result, there is a risk that, when opening such a prior art closure, the closure is propelled from the container by the pressure from the contents within the container; or that the gaseous contents of the container. Accordingly, there is a need for a container and closure mechanism in which the internal pressure generated by the contents of the container effects a seal and in which means are provided for the gradual equalization of pressure within the container during opening of the closure. 
     SUMMARY OF THE INVENTION 
     The present invention is a container and pressure sealing closure combination which can be made entirely of PET and in which the closure utilizes the pressure generated by the contents of the container to effect a seal. The closure is shaped to cover the annular mouth of the container and includes a rim portion engaging the mouth, a substantially rigid central portion and an annular toggle portion interconnecting the rim and central portions. Upward movement of the central portion in response to internal pressure from the contents of the container pivots the toggle portion to urge the rim portion substantially radially outwardly against the mouth, thereby effecting a seal. In addition, the mouth of the container includes an outer, annular recess and the rim portion of the closure includes ribs which engage the recess and thereby provide an additional mechanism of attachment of the closure to the container. 
     The mouth of the container includes an inner periphery of axially extending channels which are positioned at the interface between the rim portion and mouth. When the closure is deformed during removal from the container, the pressurized gas within the container is permitted to escape to the ambient through these channels, which regulate the egress of gases from the container and prevent an explosive burst of gas during the opening procedure. 
     In order to facilitate the removal of the closure from the container, a tab is included which projects radially from the rim of the closure. Accordingly, removal of the closure is effected by pivoting the tab relative to the closure which deforms the closure and allows the pressurized gases within the container to escape and thereby eliminates the sealing mechanism created by the toggle portion against the rim portion. In a preferred embodiment, the closure includes sets of radially extending slots which fracture when the closure is deformed during the opening procedure. This fracturing facilitates the further deformation of the closure and its removal from the container. In addition, the fracture lines resulting from the fractured slots provide a readily visible indicator that the container has been opened, and further, prevents the resealing of the container with that particular closure. 
     Also in a preferred embodiment, the container includes a pedestal or base which comprises an annular ring. The ring is shaped to receive the closure within its inner periphery in a slight interference fit. Consequently, when removed from the retainer, the closure can be stored in the base and the container and closure disposed of as a unit. 
     In an alternate embodiment, the toggle portion is modified to include a wedge component which extends radially outwardly and upwardly. When the central portion is deflected by the pressurized contents of the container, the wedge portion is pivoted into contact with the rim portion to effect the seal. 
     Accordingly, it is an object of the present invention to provide a container and closure combination which can accommodate pressurized contents of a container, such as a carbonated beverage; a combination which can safely hold pressurized contents and be made entirely of PET; a combination in which the internal pressure generated by the container contents is used to effect the seal between the container and closure; a combination in which the closure engages the container so that release of pressurized gases from the container is safely regulated during opening; a combination in which the closure includes slots that provide fracture lines during opening to facilitate opening and evidence that the closure has been removed from the container; a combination in which the container includes a base adapted to receive the closure so that the closure may be stored safely in the base after removal from the container; and a combination in which the container and closure are relatively easy to fabricate and assemble. 
     Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of a preferred embodiment of the container and pressure-sealing closure combination of the present invention; 
     FIG. 2 is a perspective view of the closure of the combination of FIG. 1 which is partially broken away to reveal the shape of the container mouth; 
     FIG. 3 is a detail showing the attachment of the closure to the container of FIG. 1; 
     FIG. 4 is a detail side elevation taken at line 4--4 of FIG. 1; 
     FIG. 5 is a bottom plan view of the closure of FIG. 1; 
     FIG. 6 is a detail side elevation in section taken at line 6--6 of FIG. 5; 
     FIG. 7 is a detail side elevation in section of the closure of FIG. 1 showing the closure attached to the mouth of the container; 
     FIG. 8 is the side elevation of FIG. 7 in which the tab is pivoted to release gases from the interior of the container; 
     FIG. 9 is the section of FIG. 7 in which the tab has been pivoted so that the closure rim is separated from the container mouth; 
     FIG. 10 is a detail side elevation of an alternate embodiment of the invention; 
     FIG. 11 is a side elevation in section of the embodiment of FIG. 10; 
     FIG. 12 is a side elevation in section of a second alternate embodiment of the invention; 
     FIG. 13 is a perspective view of the bottom of the container of the present invention in which the closure is exploded away from the base; and 
     FIG. 14 is a perspective view in which the closure is received within the base of the container of FIG. 17. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, 2 and 3, the container and pressure sealing closure combination of the present invention includes a generally cylindrically shaped container 20 having a mouth 22 which is sealed by a closure 24. Both the container 20 and closure 24 are made of a recyclable material, preferably polyethylene terephthalate (PET). 
     The closure 24 includes a raised rim portion 26, a circular central portion 28 and a toggle portion 30 which interconnects the rim portion and central portion. The rim portion 26 includes a vertically-extending, radially outer wall 32, a vertically-extending, radially inner wall 34 and a substantially horizontally-extending top wall 36 which interconnects the inner and outer walls. A tab 38 is formed integrally with and extends radially outwardly from the outer wall 32. 
     The container 20 includes an upper frustoconical portion 40, a central cylindrical portion 42 and a lower frustoconical portion 44, which terminates in an annular base 46. The upper frustoconical portion 40 terminates upwardly in the mouth 22 (see FIG. 4). 
     As shown in FIGS. 4 and 5, the central portion 28 includes a thickened peripheral rim 48 which is connected to the toggle portion 30 by a relatively thin hinge 50. Similarly, the toggle portion 30 is connected to the inner wall 34 by a second relatively thin hinge portion 52. Consequently, the toggle portion pivots relative to the central portion 28 and inner wall 34. Further, the toggle portion 30 is angled upwardly relative to the central portion 28, so that the central portion and toggle portion together form a substantially dished shape. 
     The inner wall 34 of the rim portion 26 is thickened at its lower edge 54 (see also FIG. 6), and the outer face 56 of the inner wall 34 tapers radially inwardly away from the mouth 22. The junction 58 of the inner wall 34 and top wall 36 is relatively thin to facilitate flexing during removal of the closure 24 from the mouth 22. Conversely, the radially inner face 60 of the mouth 22 tapers inwardly and corresponds generally in the angle of taper with the outer face 56 of the inner wall 34. Further, the inner face 60 includes a plurality of axially extending slots 62, substantially equally spaced about the inner periphery of the mouth 22 (see also FIG. 2). The presence of the slots provides channels for the egress of the pressurized gas within the container 20. The slots 62 are formed between a series of spaced ribs 64 formed on the inner face 60 of the mouth 22. 
     As shown in FIG. 4, the mouth 22 includes an undercut forming an annular recess 66 which extends about the periphery of the outer face 68 of the mouth 22. The outer wall 32 of the rim portion 26 includes a radially inwardly projecting rib 70 which is shaped to engage the recess 66. As shown in FIG. 5, the rib 70 extends substantially continuously about the inner periphery of the outer wall 32, being interrupted only by four fracture portions, generally designated 72. The fracture portions 72 coincide with the tab 38, at a position on the rim portion 26 diametrically opposite the tab, and two intermediate locations which are positioned at angles of approximately 77&#39; along the periphery of the rim portion 26 from the fracture portion opposite the tab 38. Each fracture portion 72 includes a pair of spaced slots 74, 76 formed in the undersides of the outer wall 32 and top wall 36. The portion of the outer wall 32 extending between the slots 74, 76 lacks the rib 70, except for the fracture portion 72 associated with the tab 38. 
     As shown in FIG. 4, the closure 24 is sealed against the mouth 22 of the container 20 in part by pressure exerted upon the closure 24 by the pressurized contents (not shown) of the container. The internal pressure of the container 20, which is above atmospheric, exerts an outward force on the central portion 28 of the closure 24 in the direction of arrows A. The slight upward movement of the central portion 28 in response to the force causes the central portion to pivot the toggle portion 30 outwardly against the inner wall 34 of the rim portion 26. This, in turn, urges the outer face 56 of the inner wall 34 against the inner face 60 of the mouth 22. The inherent hoop strength of the mouth 22 will prevent deformation sufficient to allow the internal contents to force the closure 24 off of the mouth 22. 
     Such movement is further restricted by the reverse taper engagement between the outer face 56 of the inner wall 34 and the inner face 60 of the mouth 22. The thickened portion 54 of the inner wall 34 contacts the inner face 60 of the mouth 22 at a seal area 78 (See also FIG. 7). The seal area 78 prevents the egress of the pressurized contents of the container 20 (see FIG. 1) from escaping. 
     The removal of the closure 24 from the mouth 22 is shown sequentially in FIGS. 7-9. As shown in FIG. 7, the closure 24 is securely mounted on the mouth 22 of the container 20 (see FIG. 1), in which the inner wall 34 of the rim portion 26 is urged against the inner face 60 of the mouth 22. Further, the ribs 70 of the outer wall 32 are in locking engagement with the recess 66 on the mouth 22. 
     As shown in FIG. 8, when the tab 38 is pivoted in the direction of arrow B, the rib 70 immediately adjacent to the tab 38 is disengaged from the recess 66 as the outer wall 32 and top wall 36 pivot at junction 58. The top wall 36 and inner wall 34 are, at the same time deflected away from the mouth 22 by this pivoting action. This also causes the thickened portion 54 to be displaced upwardly from the seal area 78 to the ribs 64 on the inner face 60 of the mouth 22. When in this position, the contents of the container 20 are permitted to escape through the slots 62 (see FIG. 2). 
     As shown in FIG. 9, further deflection of the tab 38 causes the area of the outer wall 32 to fracture along the slots 74, 76 on either side of the tab (see also FIG. 5). In removing the closure 24 from the container 22, the other fracture portions 72 will also split along their respective slots 74, 76. This partial destruction of the closure 24 prevents the reattachment of the closure and the resealing of the closure to the container 20. 
     An alternate embodiment of the container is shown in FIGS. 10 and 11. The closure 24&#39; is similar in construction to the closure 24 shown in FIGS. 1-9. However, the outer wall 32&#39; is somewhat thinner than the inner wall 34&#39;, and is strengthened by an outer rib 80, which extends substantially around the outer periphery of the closure 24&#39;. The closure 24&#39; also includes a central portion 28&#39;, toggle portion 30&#39; and tab 38&#39;. 
     Another embodiment of the invention is shown in FIG. 12. In that embodiment, a closure 24&#34; includes a disk-shaped central portion 28&#34; and a toggle portion 30&#34; having a raised, annular rib 82 which is wedge-shaped in cross section. When the central portion 28&#39; is deflected upwardly by internal pressure within the container 20&#34;, the wedge portion 82 pivots radially outwardly to contact the inner wall 34&#34; of the rim portion 26&#34; and effect a seal. 
     As shown in FIGS. 13 and 14, the base 46 is annular in shape and is sized to receive a closure 24&#34;&#39; therein. The closure 24&#34;&#39; shown in FIGS. 13 and 14 lacks a tab. However, a tab could be provided and the base 46 notched to receive it. Accordingly, when removed from the mouth of the container 20, the closure 24&#34;&#39; can be inserted into the base 36 and retained so that the combination can be disposed of properly. The base 46 includes a plurality of ribs 84 which extend radially inwardly slightly, and provide a slight interference fit with the closure 24&#34;&#39;. 
     While the forms of apparatus herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention.