GB2277734A

GB2277734A - Container sealing arrangements

Info

Publication number: GB2277734A
Application number: GB9309065A
Authority: GB
Inventors: Qamar Uddin Ahmed
Original assignee: Harcostar Ltd
Current assignee: Bulk Number Four Ltd
Priority date: 1993-05-01
Filing date: 1993-05-01
Publication date: 1994-11-09
Also published as: GB9309065D0

Abstract

A sealing arrangement for sealing a cover 10 to an opening in a container has a recess 15 extending around the cover and in which is located a resilient sealing member 16. The base of the recess 19 is of an essentially curved profile and the sealing member 16, in an uncompressed state, contacts the side walls 12 and 13 defining the recess and also the base wall 19 of the recess but is spaced from the recess walls between the points of contact therewith. A rim surrounding the opening of the container is received in the recess, so as to contact the sealing member 16 and to compress that member as the cover is fitted to the container and is drawn down for example by a clamping band. <IMAGE>

Description

CONTAINER SEALING ARRANGEMENTS This invention relates to a sealing arrangement for use in sealing a cover to an opening in a container, and also to a container and cover combination whenever incorporating such a sealing arrangement.

The chemical industry - inter alia - utilises drums for the storage and transportation of chemicals in a dry (and usually powder) form. A known form of such a drum is blow-moulded from a suitable grade of plastics material and is of a circular cross-sectional shape. One end of the drum defines an opening which may be closed by a moulded plastics material cover clamped to that opening by means of a metallic band which is tightened around adjacent flanges projecting outwardly respectively from the drum and the cover.

In a conventional and very widely used form of such a drum, the drum defines a rim which projects in the axial direction all around the opening, and the cover has a peripheral recess in which is located that rim. It is the usual practice to locate a simple resilient seal member in the recess, for example of circular cross-sectional shape and so similar to an O- ring, to effect a seal between the cover and the drum, when the cover is clamped in position.

The seal between the cover and the drum is quite adequate for the storage and transportation of materials in powder or similar dry form. However, it is found that the seal is inadequate for the storage and transport of materials in liquid form, and that it is very difficult to achieve a seal which performs sufficiently well in order to pass certain standard tests, when liquids are contained within the drum.

Experience shows that seepage is likely to occur between the rim of the drum and the sealing member located in the recess of the cover, so allowing leakage of liquid from the drum.

Experiments have shown that if the sealing member is replaced by another, for example of a larger size (when relaxed) or of a different grade of material, the consequent compression of the sealing member on clamping the cover to the drum is likely to deform the sealing member to such an extent that it will take a "set" after having been compressed for an extended period of time. Then, if the cover is removed to allow some liquid to be drawn from the drum and an attempt is made to replace the cover, it is almost impossible to obtain a liquid-tight seal, in view of the set of the sealing member.

A further difficulty associated with obtaining a liquid-tight seal arises from the flexible nature of the moulded plastics cover. If all leakage of liquid past the seal between the cover and drum is to be prevented, that seal must also be substantially gastight. If a gas-tight seal is achieved, the internal pressure within the drum is likely to change with temperature and may well not be equal to the external ambient air pressure. As such, the cover will to some extent be deformed by the differential pressure and this deformation of the cover will affect the sealing characteristics of the sealing member located in the recess of the cover.When the internal pressure is above the external ambient pressure, the major surface of the cover will tend to bow outwardly, and if the liquid in the drum is then allowed to wash against the inner surface of the cover - as may happen for example if the drum is dropped - the further deformation of the cover coupled with the presence of the liquid in the immediate vicinity of the seal will allow significant leakage to occur.

This invention stems from experiments conducted in an attempt to obtain a liquid-tight seal between a drum and a cover of the kind described above, with a view to obtaining an adequate seal which is able to meet internationally-agreed standards proposed by the relevant industries. As a consequence of those experiments, we have determined that by appropriately configuring the shape of the sealing member and the interaction of the same with the recess in which the sealing member is located, it is possible to obtain a reliable liquid-tight seal which meets the defined sealing standards for the storage and transport of liquid chemicals.

According to one aspect of the present invention, there is provided a sealing arrangement for use in sealing a cover to an opening in a container, the container having an upstanding rim around said opening, the lid having a recess in which the rim is located when the cover is fitted to the container, and there being closing means to draw the cover down to engage the rim deeper into the recess, in which arrangement the recess is bound by inner and outer peripheral walls defining the mouth to the recess, the spacing between said walls being less than the depth of the recess and the base wall of the recess being of an essentially curved profile, and there being a resilient sealing member located in the base region of the recess which sealing member when uncompressed by the container rim simultaneously contacts the inner peripheral wall, the outer peripheral wall and the base wall of the recess but is spaced from the recess walls between the points of contact therewith, and which sealing member is contacted and compressed by the upstanding rim when the cover is fitted to the container and is drawn down be said closing means.

It will be appreciated that in the sealing arrangement of this invention, the relaxed cross sectional shape of the sealing member is such that it contacts the walls of the cover defining the recess at three spaced-apart points but that there is clearance between those walls and the sealing member between said points. These regions of clearance allow the sealing member to be resiliently deformed by the rim of the container as the cover is drawn down over the opening, without giving rise to over-compression of the sealing member.In turn, this reduces the likelihood of the sealing member taking a "set"; instead, the sealing member may recover much of its original shape upon removal of the cover in view of the resilient deformation of the sealing member during clamping of the cover, and this allows an adequate seal to be achieved if the cover is replaced and clamped down for a second time.

A further consequence of the particular configuration of the sealing member defined in the present invention is that it is possible to use a sealing member of a less resilient grade of material than is conventionally employed when the container is to be used for the storage and transportation of dry materials. This serves to minimise the likelihood of seepage past the seal, even if the seal is subjected to shock-loading by the liquid within the container, for example if the sealed container is dropped.

In a preferred arrangement, the sealing member has a concave curved surface facing the mouth of the recess and which surface is contacted by the rim of the container opening. The sealing member may be of a substantially triangular cross-sectional shape, but with rounded corner regions and in this case, the sealing member may further have inner and outer side surfaces which may be substantially linear or concavely curved to a small extent. With such a sealing member, the contact between the member and the inner and outer peripheral walls of the recess will be in the regions of the junctions between said concave curved surface and the inner and outer side walls of the recess, respectively.

The material of the sealing member must be inert to the liquid to be carried within the container, but generally the sealing member may be made of a natural or synthetic elastomeric material. In the case of a chemical storage and transportation drum of the kind described hereinbefore, it is envisaged that the hardness of the material of the sealing member should be of a hardness of up to 100 on the Shore 00 scale and up to 80 on the Shore 'A' scale.

According to a second aspect of the present invention, there is provided a container having an opening with an upstanding rim therearound, in combination with a cover for the opening, and a sealing arrangement of this invention as described above being provided to effect a liquid-tight seal between the cover and the container.

The sealing effect of the sealing arrangement may be enhanced by providing a sealing portion around the free edge of the rim of the container, which sealing portion engages and effects a seal against the sealing member located in the recess of the cover. Such a sealing portion may comprise an enlarged head of an increased width as compared to the greater part of the rim and that enlarged head may have a bead of a substantially semi-circular cross-sectional shape extending around the surface of that sealing portion which faces the sealing member, when in use.

Various means could be devised to draw the cover down on to the rim of the container to effect a liquidtight seal therebetween, though it is possible that should there be relative rotation between the cover and the container, the sealing member may be damaged during such rotation. It is therefore preferred for said closing means to include a pair of outwardly-projecting flanges formed one on each of the container and cover respectively so that when the cover is fitted to the container the flanges lie adjacent one another, the distance between the surfaces of the two flanges respectively facing away from the other flange reducing outwardly, and to provide a clamping band arranged to encircle the flanges and engage said surfaces whereby tightening the band circumferentially draws the cover down on to the rim of the container.For reasons of security, the clamping band may incorporate a tamperevident seal.

By way of example only, one specific embodiment of sealing arrangement constructed and arranged in accordance the present invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is a cross-sectional view through the peripheral region of a cover for a moulded plastics drum, which cover has a sealing member located therewithin; Figure 2 is a view similar to that of Figure 1, but showing the cover fitted and clamped to a drum; and Figure 3 is a view similar to that of Figure 2, showing the deformation of the cover when there is an increased pressure within the drum.

Referring initially to Figure 1, there is shown a portion of the periphery of an injection moulded plastics cover suitable for use on a blow-moulded plastics drum, intended for the storage and transport of liquids. The cover comprises a main cover portion 10 of a generally circular shape when viewed in plan and around the periphery of which extends a sealing portion 11. This sealing portion comprises an inner peripheral wall 12 from which the main cover portion 10 extends, an outer peripheral wall 13 and a base wall 14 interconnecting the inner and outer peripheral walls.

A recess 15 is defined between the inner and outer peripheral walls 12 and 13, the confronting surfaces of those walls being substantially parallel though for ease of manufacture, there may be a slight taper between those walls, towards the base wall 14. The surface of the base wall 14 facing the mouth of the recess 15 is concavely arcuate.

Located within the recess 15 is a sealing member 16 of a resiliently-deformable elastomeric material and which has, when relaxed, a generally triangular crosssectional shape but with rounded corner regions.

Typically, the material of this sealing member may have a hardness of up to 100 on the Shore 00 scale and up to 80 on the Shore 'A' scale.

As fitted into the recess 15, the sealing member 16 makes contact at 17 with the inner peripheral wall 12, at 18 with the outer peripheral wall 13 and at 19 with the base wall 14. Between the contact points, there is clearance between the sealing member and the walls defining the recess 15. The surface 20 of the sealing member which faces the mouth of the recess 15 is concavely arcuate. In the illustrated embodiment, the walls of the sealing member between the contact points 17 and 19 and 18 and 19 are substantially linear.

At the free edge of the outer peripheral wall 13, there is provided an outwardly-projecting closure flange 21, having an clamping surface 22 lying at an acute angle to the general plane of the cover.

Reinforcing ribs 23, 24 are formed on the peripheral wall and further reinforcing ribs (not shown) may be formed on the main cover portion 10, if required.

Figure 2 shows the cover of Figure 1 fitted to a container, shown in part at 25. Around the opening to the container there is formed an upstanding rim 26 which, when the cover is fitted to the container, is received in the recess 15 and engages the sealing member 16. The rim 26 has a sealing portion 27 around its free edge, which sealing portion has a greater width than the width of the main part of the rim 26, and there is formed a semi-circular bead 28 on the outwardly-facing part of that sealing portion 27.

The container is also formed with a closure flange 29 of a similar shape to the closure flange 21 of the cover and arranged so that the two closure flanges lie closely adjacent one another when the cover is fitted to the container. This closure flange 29 also has a clamping surface 30, lying at an acute angle to the general plane of the opening to the container.

After the cover has been placed over the mouth of the container and the rim 26 is received in the recess 15, a metal clamping band 31 is fitted over the two closure flanges 21 and 29 of the cover and container respectively and the band is tightened circumferentially. This draws the cover down on to the container and drives the sealing portion 27 of the rim 26 into engagement with the sealing member 16 located within the recess 15. As shown in Figure 2, this causes resilient deformation of the sealing member 16 which deformation is accommodated in part by the member being deformed into close engagement with the walls of the recess. Also, the sealing member is deformed around the sealing portion 27 whereby the upper region of the sealing portion 27 is substantially completely engaged by the sealing member 16. In this way, a particularly effective liquid-tight seal can be achieved between the rim 26 and the cover.

Figure 3 is similar to that of Figure 2, but showing the deformation of the cover when the internal pressure within the container is significantly higher than the external ambient air pressure. As can be seen, the main cover portion 10 has been bowed outwardly by the internal pressure within the drum, so reducing the contact between the sealing member 16 and the sealing portion 27 of the rim 26, on the inner peripheral wall side of the rim. However, the sealing member 16 still makes an effective sealing contact with the rim, in the regions of the base wall 14 and the outer peripheral wall 13. Experiments have shown that even if the pressure within the container is raised, so deforming the cover as shown in Figure 3, liquid will not leak from the container, past the sealing member 16, in accordance with tests for containers for the storage and transport of liquids, as defined by international agreement.

Claims

1. A sealing arrangement for use in sealing a cover to an opening in a container, the container having an upstanding rim around said opening, the lid having a recess in which the rim is located when the cover is fitted to the container, and there being closing means to draw the cover down to engage the rim deeper into the recess, in which arrangement the recess is bound by inner and outer peripheral walls defining the mouth to the recess, the spacing between said walls being less than the depth of the recess and the base wall of the recess being of an essentially curved profile, and there being a resilient sealing member located in the base region of the recess which sealing member when uncompressed by the container rim simultaneously contacts the inner peripheral wall, the outer peripheral wall and the base wall of the recess but is spaced from the recess walls between the points of contact therewith, and which sealing member is contacted and compressed by the upstanding rim when the cover is fitted to the container and is drawn down be said closing means.

2. A sealing arrangement as claimed in Claim 1, wherein the sealing member has a concave curved surface facing the mouth of the recess and for contacting the rim of the container opening.

3. A sealing arrangement as claimed in Claim 2, wherein the sealing member is of a substantially triangular cross-sectional shape, but with rounded corner regions.

4. A sealing arrangement as claimed in Claim 3, wherein the sealing member has inner and outer side surfaces and contacts the inner and outer peripheral walls of the recess in the region of the junctions between said curved surface and the inner and outer side walls, respectively.

5. A sealing arrangement as claimed in any of the preceding Claims, wherein the base wall of the recess has a concavely-arcuate profile.

6. A sealing arrangement as claimed in any of the preceding Claims, wherein the sealing member is of a natural or synthetic elastomeric material.

7. A sealing arrangement as claimed in Claim 6, wherein the sealing member has a hardness in the range of ** to **.

8. A sealing arrangement substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

9. A container having an opening and a cover therefor, there being a sealing arrangement as claimed in any of Claims 1 to 7 arranged to effect a seal between the cover and the container.

10. A container as claimed in Claim 9, wherein the free edge of the rim has a sealing portion formed therearound which portion engages and effects a seal to the sealing member.

11. A container as claimed in Claim 10, wherein the sealing portion comprises an enlarged head of an increased width as compared to the greater part of the rim, and the surface of the sealing portion facing the sealing member is at least partially rounded.

12. A container as claimed in Claim 11, wherein said surface of the sealing portion carries a bead of substantially semi-circular cross-sectional shape.

13. A container as claimed in Claims 9 to 12, wherein said closing means includes a pair of outwardly-projecting flanges formed one on each of the container and cover respectively so that when the cover is fitted to the container the flanges lie adjacent one another, the distance between the surfaces of the two flanges respectively facing away from the other flange reducing outwardly and there being a clamping band arranged to encircle the flanges and engage said surfaces whereby tightening the band circumferentially draws the cover down on to the rim of the container.

14. A container having an opening and a cover therefor whenever incorporating a sealing arrangement substantially as hereinbefore described and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A sealing arrangement for use in sealing a cover to an opening in a container, the container having an upstanding rim around said opening, the lid having a recess in which the rim is located when the cover is fitted to the container, and there being closing means to draw the cover down to engage the rim deeper into the recess, in which arrangement the recess is bound by inner and outer peripheral walls defining the mouth to the recess, the spacing between said walls being less than the depth of the recess and the base wall of the recess being of an essentially curved profile, and there being a resilient sealing member located in the base region of the recess which sealing member when uncompressed by the container rim simultaneously contacts the inner peripheral wall, the outer peripheral wall and the base wall of the recess but is spaced from the recess walls between the points of contact therewith, and which sealing member is contacted and compressed by the upstanding rim when the cover is fitted to the container and is drawn down be said closing means.

7. A sealing arrangement as claimed in Claim 6, wherein the sealing member has a hardness of up to 100 on the Shore 00 scale and up to 80 on the Shore 'A' scale.