Patent Publication Number: US-4322011-A

Title: Side seal closure

Description:
BACKGROUND OF THE INVENTION 
     Plastic closures have become economically desirable in the beverage bottling industry. However, standard glass bottles have reliable dimensional tolerances for outside diameter of finish only, and do not have reliable tolerances for inside diameters or for the top surface of the finish. When closures are designed to seal on the inside or top of the bottle, the bottles cannot be made with the degree of precision required for a durable, high pressure plastic-to-glass seal. Also, closures employing only a top seal are subject to failure caused by internal pressure lifting the cap and breaking the seal. A final consideration is that the cap, while it must seal high pressures reliably during storage and handling, must be easily removable by the consumer. 
     SUMMARY OF THE INVENTION 
     The invention comprises a threaded plastic closure for containers of high pressure fluid, such as carbonated beverage bottles. The closure has a top panel section from which depends a downwardly extending annular skirt section. The inside of the skirt is threaded to engage the threaded bottle finish. The panel is provided with a depending annular rib which forms a secondary seal on the top surface of the bottle neck. The skirt defines an internal side sealing rib which makes a primary seal on an outside cylindrical surface portion of the bottle finish, directly above the threaded portion of such finish. 
     A flexible annular section between the side sealing rib and the top seal rib of the panel is contoured so that upward pressure on the top panel increases the radial compressing force on the side sealing rib. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an elevational view of a closure embodying this invention. 
     FIG. 2 is a plan view of FIG. 1. 
     FIG. 3 shows an enlarged scale sectional view taken on the plane 3--3 of FIG. 2 with the closure threaded on a glass bottle. 
     FIG. 4 is a view similar to FIG. 3 but illustrating another embodiment of the invention suitable for sealing a plastic bottle. 
     FIG. 5 is an enlarged scale vertical sectional view of a modified closure configuration embodying this invention shown in assembled relation to a container. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-3 of the drawings, there is shown a cap or closure 1, integrally molded from a thermoplastic or thermosetting material having some degree of elasticity, such as polypropylene. Cap 1 has a top panel section 2 from the periphery of which depends an annular skirt section 4. The inside of skirt section 4 has threads 6 formed thereon to engage the threaded finish 7 of a glass bottle. If desired, the bottom portion of the skirt section 4 may be extended downwardly to define a conventional tamper-proof ring 8, having an internally projecting rib 9 engaging beneath a shoulder 7c provided on the bottle finish, plus a removal tab 8a and score lines 8b. 
     The panel 2 of the closure 1 has an integral, downwardly projecting annular seal member 10, which abuts the top 7a of a bottle finish, forming a top seal when the cap threads 6 are fully engaged with the threads of the bottle. On the inside of the skirt section 4, below the top panel 2 but above the threaded portion 6, there is provided an integral, inwardly projecting annular rib 12, which is dimensioned to engage an outside cylindrical surface 7b of the bottle finish 7 with an interference fit and thereby form a primary seal with the bottle finish. The top seal rib 10 is obviously of smaller diameter than side seal rib 12. 
     The regions of the closure 1 in the vicinity of the top sealing rib 10 and the side sealing rib 12 are necessarily relatively rigid. Interconnecting these relatively rigid regions is an integral annular connecting portion 14 which is outwardly and upwardly bulged relative to the panel portion 2 and incorporates a relatively thin-walled vertical portion 14b immediately adjacent to the side sealing rib portion of the closure 1. Thin-walled portion 14b obviously has a greater degree of flexibility than any of the remaining portions of the closure. Thus the interference fit of side sealing rib 12 on the side seal surface 7a of the container finish 7 produces an outward pre-stress on the flexible connecting section 14b. 
     After the closure 1 is applied to the container, and the internal container pressure increases, the top panel section 2 of cap 1 will tend to assume a domed configuration and then may lift the depending top seal rib 10 from the top surface 7a of the bottle finish 7. The result of these displacements of the panel portion is to produce an upward and inward deformation of the flexible annular area 14b and hence to increase the radially compressing force exerted by the side sealing rib 12 on the adjacent cylindrical container wall surface 7b, thereby increasing the effectiveness of the side seal. 
     The flexible annular wall 14b may be manufactured in various thicknesses to adapt the cap to applications requiring specified relations of side seal pressure requirements to removing force requirements. 
     FIG. 4 shows a further embodiment of the invention suitable for sealing a plastic bottle 18 which has a more flexible bottle finish. In this embodiment, the closure 15 is constructed with integral annular plug member 16 depending from the top inside of the panel 2&#39; within the circumference of the top seal member 10&#39;. This annular plug 16 abuts the inside of the plastic bottle finish 18 to provide support against the side sealing force of the side annular seal rib 12&#39; All other portions of the closure 15 are the same as previously described, and the closure functions to maintain a side seal formed by rib 12&#39; in the same manner. 
     In FIG. 5 there is disclosed a modified configuration of a closure embodying this invention which utilizes an essentially flat planar surface for the panel portion of the closure to permit the convenient application of decoration on such surface. As is the case in the other modifications, panel 102 of the closure 101 has an integral, downwardly projecting annular seal member 110, which abuts the top 7a of the bottle finish, forming a top seal when the cap threads 106 are fully engaged with the threads of the bottle. On the inside of the skirt section 104, below the top panel 102, but above the threaded portion 106, there is provided an integral, inwardly projecting, annular rib 112 which is dimensioned to engage outside cylindrical surface 7b of the bottle finish 7 with an interference fit, to thereby form a primary side seal with the bottle finish. The top seal rib 110 is obviously of small diameter than the side seal rib 112. 
     The regions of the closure 101 in the vicinity of the top sealing rib 110 and the side sealing rib 112 are necessarily relatively rigid. Interconnecting these relatively rigid regions is an integral annular connecting portion 114 which includes a portion 115 of reduced thickness relative to the thickness of the panel portion overlying the top sealing rib 110 and the side wall portion adjacent to the side sealing rib 112. Such thin walled portion 115 obviously has a greater degree of flexibility than the adjacent portions of the closure. Thus the interference fit of side sealing rib 112 on the side seal surface 7a of the container finish 7, produces an outward prestress on the flexible connection 115. 
     The operation of the closure 101 shown in FIG. 5 is identical to that heretofore described. After the closure 101 is applied to the container, and the internal container pressure increases, the top panel section 102 of closure 101 will tend to assume a domed configuration and then may lift the depending top seal rib 110 from the top surface 7a of the bottle finish 7. The result of these displacements of the panel portion is to produce an inward deformation of the flexible annular connecting area 114 and, hence, to increase the radially compressing force exerted by the side sealing rib 112 on the adjacent cylindrical inner wall surface 7b of the container, thereby increasing the effectiveness of the side seal. 
     If desired, an integral pilfer-proof band 108 may be provided on the bottom end of skirt 104, having an internal shoulder 109 engaging container shoulder 7c and a score line 111. 
     Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.