EP0195149A1

EP0195149A1 - Container with closure

Info

Publication number: EP0195149A1
Application number: EP85301931A
Authority: EP
Inventors: James Moore; Catriona Grigg
Original assignee: CURVER PACKAGING Ltd
Current assignee: CURVER PACKAGING Ltd
Priority date: 1985-03-20
Filing date: 1985-03-20
Publication date: 1986-09-24
Anticipated expiration: 2005-03-20
Also published as: EP0195149B1; DE3575546D1

Abstract

Plastics container and closure assembly, the container comprising a bottom and an upright wall (18), which wall widens at least in its upper region toward a rim (19) and first locking means (20) for securing the closure to the container. The closure possesses an inverted U-shaped groove (15) which can receive the rim and part of the container wall (18). The outer skirt (9) is provided with second locking means (12). The closure can be secured to the container, the outside of the inner skirt (3) sealing the container by being tightly wedged against the inside of the container wall, and the second locking means being under the first locking means. In the closed situation there may be still a space between the rim (19) and part (8) of the closure.

Description

The invention relates to a container with a closure, both from plastics, the container comprising a bottom and an upright wall, which wall widens at least in its upper region towards a rim, first locking means for securing the closure to the container having been provided on the outside of the upright wall, and-the closure possessing an inverted U-shaped groove which can receive the rim and part of the wall, which groove is defined by an inner skirt, an annular closure flange and an outer skirt, the latter being provided with second locking means on its inside, and, with the closure secured to the container, the outside of the inner skirt sealing the container by being tightly wedged against the inside of the container wall, and the second locking means being under the first locking means.
Such a container is known from US Patent Specification No. 4,165,020.
The disadvantage of this container-and-closure combination is that the closure is difficult to release because the second locking means engage the first locking means under stress. This is the case especially when the closure has been under a load, causing the centre part to sink into the container to the maximum extend. In such a case, it is usually impossible to remove the cover without tools.
The object of the invention is to improve a container-and-closure of the above-described type, so that the closure is easier to remove, also when the centre part of the closure has sunk into the container to the maximum extent.
The invention is based on the insight that with a closure which, with a sunk centre part, forms a tight seal with the inside of the wall of a container which widens towards the rim, the seal remains intact when the centre^-part.of the closure is moved down into the container along some distance. This is because the wedging and the concomitant sealing start already when the outside of the inner skirt comes into contact with the inside of the container wall when the cover is fitted to the container. When the centre part is inserted further into the container, which is possible on account of the elasticity of the plastic, the wedging force keeps increasing along some distance until by warpage or corrugation the closure is deformed so much that its sealing properties are lost. The vertical distance which the closure can travel from the point where wedging and sealing start to the point where the sealing properties are lost is hereinafter referred to as the wedging distance. This wedging distance depends on the polymer used and on the design details of the container and the closure, for example the extent to which the container and the inner skirt taper, but can be determined empirically, taking into account certain injection moulding tolerances.
The wedging distance defines an annular wedging area on the inside of the container. When the inner skirt enters this area from above, the inner skirt starts to seal against the inner surface of the container wall, and when, upon deeper insertion, the inner skirt leaves this area, the closure loses its sealing properties.
The container-and-closure assembly is characterized in that, when a closure has been fitted to the container, in which situation the first and second locking means lockingly engage and the centre part is already sealingly wedged against the container wall along a height 'a' of the wedging area, between the rim and the underside of the annular closure flange there is still-a space for insertion of the container wall, with a height less than the difference between the height of the wedging area and the height 'a'.
The closure of a container-and-closure assembly designed in this way can always be easily removed. If, by whatever cause, the first and second locking means engage under high stress, making it impossible to move the second locking means outward, then the closure can be pressed down, so that the wall slides further into the U-shaped groove. The first and second locking means will then come apart, and the second locking means can now be moved outward without difficulty, after which the closure can be removed.
Preferably, the container-and-closure assembly is designed in such a way that, via an inwardly downwardly sloping transition member the inner skirt joins a substantially horizontal closure wall, which has been provided with a circumferential vertical flange on its underside, that the angles between the annular closure flange and the skirts that join it are substantially right, that the U-shaped groove has along at least part of its height, from the annular closure flange downwards, a radial width between inner skirt and outer skirt which equals a uniform wall thickness of the portion of the container wall located above the first locking means, and that the distance between the rim of the container and the first locking means is equal to or greater than the height of the inner skirt.
It has been found that a closure as described above can be injection moulded with a much greater dimensional stability than other known closures. By a greater dimensional stability is meant here that the closures ultimately obtained after cooling, have dimensions differing within much narrower limits than usual. This phenomenon could not be predicted, nor can it be explained or calculated. Also, with the above-described design of the top section of the container a much greater dimensional stability can be achieved. It has been found that by making the top section of the container equally thick in all places, and not providing beads, flanges or ribs, the process of cooling the mould can be controlled much better and the shrinkage occuring during cooling can be predicted much better, so that, again, dimensional deviations in the containers produced are within much narrower limits. The higher dimensional stability is advantageous in that it permits better definition of the wedging area of the container-and-closure assembly.
The absence of ribs, beads, flanges and other thickened parts from the upper region of the container wall offers a number of advantages. In the first place, the groove width and hence the width of the annular closure flange can be small, so that a closure is prevented from being drawn into the container under a load.
A wide flange which is drawn into the container exhibits a much higher degree of concave radial flexure, viewed from above, than a narrow flange. This lower degree of flexure of a narrow flange, which is also contributed to by the right angles between the annular cover flange and the two skirts, makes it more difficult for the outer skirt to be drawn over the rim into the container. In the second place, the part of the container wall received into the groove is more flexible, so that it conforms better to the groove, resulting in improved leak-tightness. In the third place, no sink marks occur on the sealing face of the container wall, resulting in improved sealing properties. Sink marks are depressions on plastics surfaces formed by shrinkage during cooling when on the other side of the walls thickened spots have been provided.
Because the first locking means can be located at substantially the same level as where the transition between inner skirt and transition member occurs when a closure has been fitted to the container, the components together provide a unique resistance to radial compression of the container, thereby substantially obviating a source of leakage.
The first locking means may comprise a rib or flange around the container.
The second locking means may comprise a round-going rib on the inside of the outer skirt of the closure.
The container and the closure may be made of the same material suitable for injection moulding or from different materials suitable for injection moulding, such as homopolymers of ethylene and propylene, copolymers of ethylene and/or propylene, and mixtures of these (co)polymers.
On account of its good sealing properties, its good stackabi- lity, its robustness and its easily fittable and removable closure, the container according to the invention is eminently suitable as a nestable, single-service packaging bucket for solids, pastes and liquids.
The invention will hereafter be explained in detail with reference to an embodiment represented in the drawing.
In the drawing,

Fig. 1 shows a closure according to the invention, half in axial cross section and half viewed from the side;
Fig. 2 shows a container according to the invention, half in axial cross section and half viewed from the side;
Fig. 3 shows a container and a.closure according to Fig. 1 and Fig. 2, with the first and second locking means engaging, and
Fig. 4 shows a container and a closure according to Fig. 1 and Fig. 2 with the first and second locking means being apart.

The closure 1 in Fig. 1 has a sunk centre part 2, which is composed of an inner skirt 3, which via an inwardly downwardly sloping transition member 4 joins a substantially horizontal closure wall 5, which on its underside has been provided with a circumferential vertical flange 6. Via a right angle, the inner skirt 3 joins an annular closure flange with underside 8, which in turn via a right angle joins the outer skirt 9, which has a portion 10 parallel with the inner skirt 3 and.a widened portion 11. On the inside of the outer skirt second locking means have been provided in the form of a round-going rib 12 with top 13. The groove 14, in the shape of an inverted U, is formed by the components 3, 7 and 9 and possesses a portion 15, from the underside 8 of the annular closure flange 7 downwards, which has a radial width 'd'.
The container 16 drawn in Fig. 2 has a bottom 17 and an upright wall 18 which gradually widens towards a rim 19 so that the containers can be nested one in the other. On the outside of the container wall are first locking means in the form of a rib 20 around the container with an underside 21. The wall thickness of the upright wall 18 is 'd' and equals the radial width of part 15 of the U-shaped groove 14 between the inner skirt 3 and the outer skirt 9. The portion of the container wall 18 which is located above the rib 20 has a height which virtually equals the height of the inner skirt 3. The distance 'hl' between the underside 21 of the rib 20 and the rim 19 of the container is smaller than the distance 'h2' in Fig. 1, between the top 13 of rib 12 and the underside 8 of the closure flange 7. When the closure has been placed on the container 16 as drawn in Figure 3, with the top 13 of the rib 12 engaging the underside 21 of rib 20, there is a space 22 left between the underside 8 of the annular closure flange 7 and the rim 19 of the container, into which space the upright wall 18 can slide when the closure is lowered. In the position drawn in Fig. 3, the outside of the inner skirt 3'is already wedged against the inner surface of the upright wall 18, so the centre part 2 has already entered the wedging area along, for example, a distance 'a'. For the sake of clarity, in Fig. 3 a line 1 has been drawn on which the wedging height of the wedging area has been indicated as the distance PQ. The distance PR equals 'a'. In the position drawn, the height of the space 22 between the rim 19 and the underside 8 of the annular closure flange is smaller than the wedging height PQ minus PR, so that when the centre part has been pushed so far into the container that the underside 8 of the annular flange 7 rests on the rim 19, the centre part 2 is still in the wedging area. The rib 12 has then also disengaged from the rib 20, as drawn in Fig. 4.
In use, the closure is fitted to the container in the position according to Fig. 3. If on account of tensile stress in the outer skirt the rib 12 is difficult to pull from under the rib 20, by pressing on the closure the rib 12 can be disengaged from rib 20 so that the preliminaries for removal of the closure are easier to perform.
Stacking a large number of containers one on the other does not result in increased stress between the locking means.
The rib 20 can also be provided in a lower position, as indicated by 20' in Fig. 3. The outer skirt 19 will then have to be adapted accordingly, so that the rib 12 also comes in a lower position; see 12' in Fig. 3. The resulting configuration is indicated by dotted lines.

Claims

1. A container with a closure, both from plastics, the container comprising a bottom and an upright wall, which wall widens at least in its upper region toward a rim, first locking means for securing the closure to the container having been provided on the outside of the upright wall, and the closure possessing an inverted U-shaped groove which can receive the rim and part of the wall, which groove is defined by an inner skirt, an annular closure flange and an outer skirt, the latter being provided with second locking means on its inside, and, with the closure secured to the container, the outside of the inner skirt sealing the container by being tightly wedged against the inside of the container wall, and the second locking means being under the first locking means, the container and closure being characterized in that when a closure has been fitted to the container, in which situation the first and second locking means lockingly engage and the centre part is already sealingly wedged against the container wall along a height 'a' of the wedging area, between the rim and the underside of the annular closure flange there is still a space for insertion of the container wall, with a height less than the difference between the height of the wedging area and the height 'a'.

2. A container with a closure according to claim 1, characterized in that via an inwardly downwardly sloping transition member the inner skirt joins a substantially horizontal closure wall, which has been provided with a circumferential vertical flange on its underside, that the angles between the annular closure flange and the inner and outer skirt which join it are substantially right, that the U-shaped groove has along at least part of its height, from the annual closure flange downwards, a radial width between the inner skirt and the outer skirt which equals a uniform wall thickness of the portion of the container wall located above the first'locking means and that the distance between the rim of the container and the first locking means is equal to or greater than the height of the inner skirt.

3. A container with a closure according to Claim 2, characterized in that the first locking means comprise a rib provided around the container.

4. A container with a closure according to Claim 2 or 3, characterized in.that the second locking means comprise a rib provided on the inside of the outer skirt.

5. A container with closure substantially as described herein with reference to the accompanying drawings.