FIELD OF THE INVENTION THIS INVENTION relates to closures for containers such as bottles and jars.

BACKGROUND TO THE INVENTION

Glass and plastic containers for beverages, sauces, jams, pickles etc are usually considered to fall into two categories. These are narrow mouthed containers meaning bottles with mouth diameters of, for example, 20 to 40mm and wide mouth containers meaning jars with mouth diameters of, for example, 40 to 100mm.

Wide mouth containers are usually closed by screw-on closures in the form of lids. Less frequently snap-on closures of polyethylene (high or low density) are used.

The present invention provides an improved form of closure which is specifically intended for wide mouth containers but is also suitable for narrow mouth containers.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided a screw-on closure for a container which is of PET (polyethylenetetraphthalate) or a PET copolymer or a mixture of PET and a PET copolymer and which comprises a cylindrical skirt having screw threading on the inside surface thereof and a disc-like end wall. The screw threading can be continuous or can comprise a number of discrete thread sections spaced around the inside surface of the skirt.

The skirt can be thicker along the free edge portion thereof than it is between the free edge portion and the disc-like end wall. There can be a circular rib on the underside of the disc-like end wall, the rib being inwardly of the skirt and defining, between itself and the skirt, an annular recess for receiving a seal.

To enable containers with the closures fitted to them to be stacked, the surface of the disc-like end wall can be of roughened form to inhibit slippage between the closure of a lower container and the base of an upper container stacked on the lower container. Alternatively, or additionally, there can be a rim around the periphery of the disc-like end wall, the rim standing proud of that surface of the disc-like end wall that is remote from the sleeve. The rim can be circumferentially continuous, or can consist of a series of discrete sections with gaps between them. The closure is preferably injection moulded but it can be compression moulded.

The closure can be stabilised by screwing it onto an externally threaded container the temperature of which has been raised by filling it with produce at an elevated

temperature whereby the closure is heated to a temperature of between 75 and 1 10 degrees centigrade, preferably between 90 and 1 10 degrees centigrade.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the

accompanying drawings in which:-

Figure 1 is a pictorial view of the underside of a closure in accordance with the present invention; Figure 2 is a pictorial view similar to that of Figure 1 and showing a closure with a tamper band;

Figure 3 is a side elevation of the closure of Figure 2; and

Figure 4 is a section illustrating the closure of Figure 1 screwed onto a jar.

DETAILED DESCRIPTION OF THE DRAWINGS

The closure illustrated in Figure 1 is designated 10 and comprises a cylindrical skirt 12 and a disc-like end wall 14. On the inside of the skirt 12 there are discrete thread sections 16 which are compatible with a continuous screw thread T on the outside of the jar J (Figure 4) and adjacent its open mouth. The closure can be of PET or a PET copolymer or a mixture of PET and a PET copolymer.

The closure can be injection moulded or compression moulded. It is preferred that the closure include not less than 30% of the copolymer. It is further preferred that the copolymer be present in amounts exceeding 50% or 75% and in some circumstances it is preferred that the closure be injection moulded using only the copolymer. On the outside of the skirt 12 there are circumferentially spaced, rectangular raised areas 18 which facilitate gripping of the closure when it is to be screwed onto, or unscrewed from, the jar J. The provision of these areas has the result that, considered circumferentially, the skirt has alternating thicker and thinner wall portions. The top surface of the closure can be moulded with a roughened surface. This facilitates stacking as it reduces the ability of the base of an upper container in a stack to slip with respect to the closure of the lower container on which it is stacked.

Alternatively, or additionally, a rim can extend around the periphery of the upper surface of the closure, the rim standing proud of that surface of the disc-like end wall that is remote from the sleeve. The rim can be circumferentially continuous or it can comprise a series of discrete sections with gaps between them. These sections are preferably upward extensions of the raised areas 18.

At its rim the skirt is thicker than it is over the remainder of its height. This is achieved by moulding the skirt with a bead 20 (see Figure 4) of rectangular cross-section. The thickened rim portion of the skirt 12 prevents flaring of the skirt. A circular rib 22 is moulded onto the underside of the disc-like end wall 14 of the closure. The rib 22 is inwardly of the skirt 12 and defines therewith a recess 24, which, in use, faces downwards and which receives a seal 26. The seal 26 presses onto the edge of the jar which bounds the mouth of the jar J (see Figure 4). The closure of Figures 2 and 3 differs from that of Figure 1 in that it has a tamper band

28 secured to the rim of the skirt 12 by bridges 30. The band 28, after the closure has been fitted to the jar, is heated so that it shrinks and is under the bead B. The band can be shrunk by the heat of a heat shrink tunnel through which the jar and container pass, by moving past infrared heaters or by the application of an ultrasonic horn the vibrations of which heat the band 28.

Should an attempt subsequently be made to soften the band 28 by heating it, the PET constituting the band discolours thereby revealing tampering.

The bridges 30 fail when the closure is first unscrewed from the jar.