WADDED CLOSURE

Abstract: A thermoplastic closure comprising a top wall (3) and in internally threaded skirt (1, 2) and adapted to receive a resilient sealing disc (6) in which an annular flexible protrusion (5) depends from the inner side of the top wall (3) adjacent the intersection of the top wall (3) and skirt (1) but spaced from the skirt (1). As the closure is applied to a container neck the protrusion (5) acts to fold the periphery of the sealing disc (6) over the outer edge of the container neck (8) and onto the outer side surface and radius (9) of the container neck to thereby effect a seal.

Description: The present invention relates to a thermoplastic pre threaded screw closure for an externally threaded bottle neck and of the type utilising soft resilient circular liners or discs to provide a positive hermetic seal thus preventing liquid and gas loss in carbonated beverage containers. " Such screw closures are generally known and used for beverages containing carbon dioxide. A sealing liner, held in place inside such closures between the intersection of the top and downward protruding sidewall is essential for provision of a positive seal after the closure has been first applied and after re-closing. This type of sealing medium also allows easy removal of the cap. Any seal on the top alone of a container neck is not suffic¬ iently positive as when pressure is developed inside the container the circular top wall of the closure lifts due to the flexibility of the thermoplastic material. In lifting, some top seal is lost, thus increasing the chance of pressure and liquid loss. It is therefore necessary to provide a seal either in the bottle bore or preferably on the top sealing surface to outside neck wall radius and down the vertical sidewall. In the case of glass finishes the outside wall tolerances are considerable and the neck top to side- wall intersection radius is subject to manufacturing variations thu making it difficult to design a closure to co-operate with this intersection and provide a side seal. The object of this invention is to ameliorate one or more of the problems of the prior art by providing a pre threaded screw clos ure with an adequate top and side seal. The invention discloses a thermoplastic closure adapted for use with a container having an externally threaded neck opening. Tne closure has a pre formed thread of at least one. radial turn which engages with the exter- nally threaded bottle neck. Inside the closure there is a downward extending protrusion from the top wall which forces a soft resilient circular liner against the top and side of the bottle neck or finish in order to provide a positive seal. It is important that the protrusion is from the top wall as the protrusion is.radially laterally flex¬ ible and will allow for inherent variation in the sealing liner thickness. One embodiment of the present invention is disclosed in figure 1 being a part radial section through a closure in accordance with the present invention in sealing relationship with the bottle neck. Fig 2 depicts the same closure before application to abottle. According to figure 1 the closure is provided with an annular skirt (1) with an internally pre threaded section (2). The circular top wall (3) is integral with the skirt and has a protrusion (5) depending downwardly therefrom. Disc retaining means (4) are shown in the form of an annular flange extending inwardly from the skirt's inner wall. The thread (2) is in engagement with corresponding thread ( 7) on the bottle neck and the protrusion (5) has forced the periphery of the disc (6) down past the top of the bottle neck ( 8) onto the side surface and radius ( 9) of the bottle neck thus effecting a side seal. The downward extending protrusion defines a gap between itself and the closure skirt. Preferably the protrusio (5) is flexible and can therefore move radially thereby allowing for inherent variation in the thickness of disc (6). OMPI

Claims: The claims defining the invention are as follows: 1. A thermoplastic closure with an internally threaded skirt of the type adapted to receive a resilient sealing disc, the closure having an annular flexible protrusion depending from the inside top wall adjacent the top wall/skirt intersection, spaced from the skirt and adapted to fold the periphery of a resilient sealing disc around a closure neck and down its outside side wall thus effecting a seal. 2. A closure as in claim 1 wherein the protrusion is substantially rectangular in radial section. 3. A closure as in either claims 1 or 2 having a disc retaining flange extending radially inwardly from the skirt below the lower extremity of the protrusion. 4. A closure in accordance with any one of the preceding claims made from polypropylene and adapted to be used with a disc manufac¬ tured from ethylene vinyl acetate. 5. A thermoplastic closure substantially as hereinbefore described with reference to the accompanying drawings. OMPI

Inventors: DRUITT RODNEY MALCOLM, DRUITT, RODNEY, MALCOLM
Applicants: BEV CAP PLASTICS PTY LTD, BEV-CAP PLASTICS PTY. LTD.
Application year: 1984
Main classification: B65D41
IPC codes: B65D41