EP0119788A2

EP0119788A2 - Improvements relating to closures

Info

Publication number: EP0119788A2
Application number: EP84301511A
Authority: EP
Inventors: Peter Reginald Haines
Original assignee: Metal Closures Ltd
Current assignee: Arconic Closure Systems International UK Ltd
Priority date: 1983-03-14
Filing date: 1984-03-07
Publication date: 1984-09-26
Also published as: JPS59187553A; AU2555984A; JPS59187554A; EP0119055A2; ZA841800B; ZA841801B; AU2556084A; GB8306937D0; ES278157U; ES278158U

Abstract

A moulded plastics closure for a container having a screw-threaded neck has a top 11 and a depending skirt 12 with an internal screw-thread ridge 13. A sealing rib 14 projects radially inward from the skirt above the ridge 13. The central area of the top 11 is in the form of a well, the bottom wall 25 of which is concavely curved. The side wall 26 of the well and a downward extension 30 thereof provide an outwardly projecting rib 28. The top of the neck of the container is received between ribs 14 and 28 which form seals with the external and internal surfaces of the neck. Additional ribs 20 project into sealing contact with the top end of the neck.

Description

This invention relates to closures for containers having externally screw-threaded necks.
According to this invention there is provided a closure for a container having an externally screw-threaded neck, said closure being moulded in one piece from a resilient plastics material and comprising a top and a depending skirt which has on its internal surface a screw-thread ridge and a first annular sealing rib which is disposed between the ridge and the top and which projects radially inward beyond the crest of said ridge to form a seal with the radially outer face of the neck by outward deformation of the rib, said top having a depressed central portion forming a well the side wall of which, on a downward extension of the side wall of which, has on its radially outer surface a radially outwardly projecting second annular sealing rib for forming a seal with the internal surface of the neck by radially inward deformation of the rib.
The first and second sealing ribs are preferably aligned with each other in a radial direction.
Preferably at least one additional annular sealing rib projects downward from the top of the closure at a location between and spaced from the skirt and said side wall of the well for engagement with the top end of said neck.
The bottom wall of said well may be convexly or concavely curved, viewed from above, in its unstressed condition.
The thickness of said bottom wall preferably increases smoothly towards the centre of said well.
The invention will now be described in more detail with reference to the accompanying drawings in which:

Figure I shows a first embodiment of the invention in axial section, and
Figure 2 shows part of Figure 1 on a larger scale.

Referring to the drawings a closure 10 is moulded in one piece from a resilient plastics material. The closure is designed to provide a seal for a bottle containing a beverage under pressure e.g. a carbonated pressure and to be usable to re-seal the bottle after part of its contents have been removed. The closure has a top 11 and a skirt 12 which is internally screw-threaded, and externally knurled for improved manual grip. Above its screw-thread ridge 13 and adjacent the top of the skirt has an internal radially- inwardly projecting sealing rib 14 the tip 15 of which extends inward to a greater extent than the screw-thread ridge 13. The tip 15 of the rib is in this instance radiussed. The rib is of stiff, broad-based generally triangular form and is designed to achieve sealing in contact with the outer surface of the neck of the bottle by virtue of the sealing pressure deriving from the resulting hoop stresses in the rib, so that instead of the rib buckling or becoming turned back on itself as would be the case if a thin fin were employed, the radiussed tip of the rib tends to become flattened.
The portion 12a of the skirt extending upward from the location of the sealing rib 14 to the top 11 is conically inclined inwardly.
The top has a depressed central area forming a well, the bottom wall 25 of which is concave viewed from above and convex viewed from below. The =thickness of the bottom wall 25 increases gradually towards the centre of the area. The side wall 26 of the well has an extension 30 below the point at which the bottom wall joins it, and the radially outer surface of the extension provides part of a second annular sealing rib 28 disposed opposite the first sealing rib 14 and a chamfered surface 31'forming a lead-in for the end portion of the neck of the bottle into the channel 29 defined between the outer portion 27 of the top of the closure, the portion 12a of the skirt, and the side wall 26 of the well.
Two additional annular sealing ribs 2₀ project downward into the channel 29 from the top 11 of the closure for sealing engagement with the end face of the neck of the bottle. In the illustrated construction the ribs are of triangular cross-section having an apex angle of 60°.
In use of the closure, the end portion of the neck of the bottle is forced into the channel, assisted by the lead-in formed by surface 31 and the curved form of the rib 14 as the closure is screwed home so that the sealing ribs 14 and 18 can engage external and internal surfaces respectively of the neck to form seals and so that the ribs 20 come into sealing engagement with the top end of the neck. The positions of and spacing between the ribs 14 and 28 are preferably determined in accordance with the tolerances on the neck size of the bottle. For example the tolerance on the neck diameter of a glass bottle is based on the outside diameter, and it is arranged that when the neck diameter is on the upper limit the outer rib 14 is in full sealing engagement with the neck and on the lower limit, rib 28 is in light sealing contact with the neck. The internal diameter of the neck is not the subject of tolerance but tends to be a predetermined amount less than the outside diameter and in consequence, the sealing pressure between the inner rib 28 and the internal surface of the neck tends to vary inversely as the pressure of,rib 14 on the neck, so that a lighter sealing pressure by one of ribs 14, 28 is compensated by a heavier pressure by the other rib.
The radially-outer face of the side wall 26 has, viewed in cross-section, a concavely curved shape which extends to the top of rib 28 and which forms a thin section just below the portion 27 of the top, so as to form a pivot point in the event of radial deflection of the side wall 26.
It will be apparent that any gaseous pressure within a container to which the closure is applied tends initially to flatten the curvature of the broken wall 26 and thus to increase its effective diameter, forcing the rib 28 into tighter sealing engagement with the neck of the container. However, in some constructions according to the invention where the contents of the container are under vacuum, the bottom wall 25 is convex viewed from above and concave viewed from below. The thickness of the wall increases progressively towards the centre of the well.
In some constructions the downward extension 30 of the side wall 26 is omitted and the radiussed sealing rib 28 is disposed opposite the point at which the bottom wall 25 joins the side wall 26.
Closures according to the invention can be employed equally well for containers intended to contain still liquids.
In the conventional method of manufacture of glass bottles the mouth of the bottle is formed by mould section which extends so as to form a narrow band of the radially inner and outer surfaces of the neck immediately adjoining the end of the neck. When the present closures are to be employed on bottles, therefore, it is preferred to design the closure so that the ribs 14, 18 respectively engage these same narrow bands of the outer and inner surfaces of the neck.

Claims

1. A closure for a container having an externally screw-threaded neck, said closure being moulded in one piece from a resilient plastics material and comprising a top and a depending skirt which has on its internal surface a screw-thread ridge and a first annular sealing rib which is disposed between the ridge and the top and which projects radially inward beyond the crest of said ridge to form a seal with the radially outer face of the neck by outward deformation of the rib, said top having-a depressed central portion forming a well the side wall of which, on a downward extension of the side wall of which, has on its radially outer surface a radially outwardly projecting second annular sealing rib for forming a seal with the internal surface of the neck by radially inward deformation of the rib.

2. A closure as claimed in claim 1, wherein the bottom wall of said well is concavely curved.

3. A closure as claimed in claim I, wherein the bottom wall of said well is convexly curved.

4. A closure as claimed in any one of the preceding claims, wherein said second sealing rib is located opposite the point at which the bottom wall of the well joins said side wall.

5. A closure as claimed in any one of the preceding claims, wherein said downward extension, where provided, as the radially outer surface thereof chamfered to form a lead-in, below the second sealing rib, for the neck of the bottle.

6. A closure as claimed in any one of the preceding claims, wherein the tip of said first sealing rib is radiussed.

7. A closure as claimed in any one of the preceding claims, wherein at least one additional annular sealing rib projects downward from the top of the ·closure at a location between and spaced from the skirt and said side wall of the well for engagement with the top end of said neck.

8. A closure as claimed in any one of the preceding claims in which the portion of the skirt extending upward from the position of the first sealing rib to the top is conically inclined inward.