GB2152913A

GB2152913A - Lids for containers

Info

Publication number: GB2152913A
Application number: GB08500701A
Authority: GB
Inventors: Keith Ernest Wiles
Original assignee: Nacanco Ltd
Current assignee: Ball Beverage Packaging UK Ltd
Priority date: 1984-01-21
Filing date: 1985-01-11
Publication date: 1985-08-14
Also published as: GB8401629D0; GB8500701D0; GB2152913B

Abstract

A container lid (11), preferably moulded from polypropylene, has a dependent side wall portion at the periphery of its circular centre panel (12), with one or more deformable annular fins (18,28) on its outer surface, which form an interference fit with a corresponding portion of a container fitted with the lid, by deforming and so producing an air-tight and liquid-tight seal. Struts or webs (21) preferably brace the side wall portion relative to the lid panel (12). <IMAGE>

Description

SPECIFICATION Lids for containers This invention relates to lids for containers and is especially, but not exclusively, concerned with lids for paint cans and other such containers of the kind provided with lever rings. The lids of the invention can conveniently comprise one-piece plastics mouldings and can be used with many kinds of container, including plastics moulded containers, tin plate containers and others.

In accordance with the invention, a lid is provided, preferably of a plastics material, having a portion or sealingly engaging with a corresponding portion of a container to which the lid is to be fitted, wherein the lid portion comprises at least one flexible annular fin which extends generally radially outwardly of and circumferentially around the lid and which is arranged to be deformed when the lid is fitted to the container so as to provide sealing engagement between the lid portion and the container portion.

Preferably, two or more of such fins are provided on the lid portion, a particularly preferred arrangement involving the provision of four or five fins.

Preferably, the one or more annular fins are deformed by flexing away from the container as the lid is fitted thereto. The lowermost fin, that is to say, the fin nearest to or even located at the nose of the lid, and therefore comprising the fin which first contacts the container portion as the lid is being fitted on to the container, can be arranged so as to be situated beneath the lever ring of the container portion to which the lid is fitted, when the container is closed by means of the lid. Also, the shape and number of fins can be varied according to the shape and size of the particular container to which the lid is to be fitted. The lid portion carrying the one or more fins is preferably a side wall portion dependent from the periphery of a circular centre panel of the lid.

In order to allow for pressure changes within the container when the lid has been applied thereto, a central part of the lid, such as the central panel in the case of a conventional paint can lid, may also be made somewhat flexible so that, to a certain extent, it can flex axially inwardly and/or outwardly relative to the container.

In accordance with a particularly preferred embodiment of the invention, however, the central panel of the lid is made with a sufficient stiffness, which in practice can be based upon it having a sufficient thickness especially when made as a one-piece plastics moulding, so that undue flexing is avoided and the top surface of the panel and therefore of substantially the whole lid remains essentially flat. According to another preferred embodiment of the invention, a plurality of supporting struts or webs are provided between the lid portion and the peripheral region of the underside of the lid.

Preferred embodiments of the lid in accordance with the invention are described below, by way of example only with reference to the accompanying drawings in which: Figure 1 shows a first embodiment of a finned paint can lid according to the invention, in radial cross-sectional view; Figure 2 shows a second embodiment of a lid according to the invention, also in radial cross-sectional view; Figure 3 shows the lid of Figure 2, also in radial cross-sectional view, when fitted into the upper opening of a lever ring can.

Referring to Figure 1 of the drawing, a lid 1 for a paint can with a conventional lever ring is made of a suitable plastics material, for instance, polypropylene, and comprises a generally flat circular central panel 2, having an annular recess 3, typically of rectangular radial cross-section, extending around its periphery. The lid 1 includes a dependent lid portion in the form of a side wall portion 6, located at the periphery of the central panel 2, and also a radial flange 7, which extends radially outwardly of the annular recess 4 and above the lever ring of the can, when the lid 1 is secured thereto.

In Figure 1 of the drawing, the container portion with which the lid 1 primarily engages when the lid and the container are fitted together, namely the lever ring, is not shown and its radial inner surface is represented by a chain-dotted line L. The lower rim of the side wall 6 comprises a nose, shown generally at 4, which has a radial cross-section 5 which corresponds generally to that of the annular recess 3. A large number of the lids 1 can thus be stacked conveniently upon one another, because the recess 3 of one lid 1 receives the nose 4 of the next higher lid 1 in the stack.

Extending radially outwardly from the lid portion, i.e from the outer surface of the side wall portion 6, are five flexible annular fins 8, which preferably are mutually spaced at regular intervals.

As can be seen from the position of the chain-dotted line L, the fins 8 extend radially outwardly beyond the corresponding part of the container portion formed by the inner surface of the lever ring. When the lid 1 is applied to the can or other container, the shape and construction of the flexible fins 8 ensures that they are deformed upwardly with respect to the side wall portion 6, namely in a direction away from the container per se, so that air-tight and liquid-tight sealing engagement between the lid 1 and lever ring of the container is given. All of the fins 8 or, at least, the lowermost fin 8, namely, that immediately adjacent the nose 4 of the lid 1, is or are formed with an upwardly-directed lower surface, shown at 8a in Figure 1. This assists in leading the side wall 6 into the aperture of the container which is being closed by the lid.

Also, the lowermost fin 8 is so positioned that it passes below the lowest part of the lever ring, when the lid is fully seated in the container aperture, and so prevents inadvertent removal of the lid 1.

The detailed construction of the rim of the lid 1, described above enables it to form an interference fit with the can lever ring and this also acts as a resistance to removal of the lid from the can. In practice, this resistance depends upon the dimen sions of the fins 8, the material from which the fins 8 and therefore the whole lid are made, the lever ring material and other physical parameters.

Therefore, it will be understood that many factors, such as the dimensions and material of the fins 8, can be altered according to particuiar requirements. Furthermore, as regards the material forming the lid 1 and thus the fins 8, they are preferably capable of recovering to their original configuration, as shown in Figure 1 of the drawing, as soon as possible after removal of the lid from the can.

This is a relatively important, although not a critical, feature of the preferred forms of lid of this invention. A preferred constructional material for the lid shown in Figure 1, giving all the preferred features and advantages mentioned, is polypropylene, although any other suitable plastics material may be used.

The lid 1 shown in Figure 1 has a centre panel 2 which, as can be seen, is thinner than the peripheral flange 7. Also, in order to provide the periphery of the lid 1 with adequate strength and stiffness, particularly in the side wall portion 6 which has to cooperate properly with the container or can in order to give the desired sealed closure of the container or can, the side wall portion 6 has a tapered radial cross-section, being of greatest thickness at the top where it is attached to the lid panel 2 and progressively narrowing toward the nose 4. The outer surface of this portion 6, on which the fins are formed, is essentially cylindrical.

Paint can lids made of plastics materials sometimes have a tendency to bow upwardly, which is undesirable because it spoils the appearance of the cans and may also lead to inefficient sealing and even leakage of the paint or other can contents.

This bowing can be caused by the internal pressure being higher than the external atmospheric pressure, for instant, because of excess air trapped in the cans as their lids are applied to close them or because of exposure to a higher temperature. It is generally undesirable to combat this bowing tendency simply by increasing the thickness of the lid panels, because this would have the attendant disadvantages of raising the volume of plastics moulding powder in each lid and therefore increasing their cost and the manufacturing time. All successful designs of lid therefore have to be a compromise between these and other relevant and somewhat competing requirements.A particularly successful and preferred form of lid of the present invention is shown in Figures 2 and 3, in which parts equivalent to those shown in Figure 1 are identified by the same reference numbers increased by 10.

The lid 11 consists of a one-piece moulding, preferably of polypropylene, and has a circular central panel 12, surrounded on its upper side by a wide and very shallow annular recess 13 and, radially outside the latter, a flange 17. The underside of the flange 17 can be provided at spaced points with recesses, one of which is shown at 20, for receiving a lever, such as the blade of a screw-driver, to facilitate damage-free removal of the lid 11 from the container closed by it. At the region of the junction between the flange 17 and the recess 13, the lid 11 includes a dependent side wall portion 16, which has a plurality of outwardly-directed circumferential fins 18 at spaced locations upon its outer surface.A lowermost fin 28, which may be positioned below the lowest fin 18 by a greater distance than the regular spacing between adjacent ones of the fins 18, is also provided on the side wall portion 16. The wall portion 16 can have a uniform radial thickness throughout the part carrying the fins 18 and can have a greater radial thickness and therefore a somewhat greater stiffness in the nose portion 25, i.e. the part below the lowermost fin 28 extending to the lower rim 14 of the wall portion 16.

Each of the regularly-spaced sealing fins 18 and also the lowermost fin 28 preferably has a generally horizontal and planar upper surface, as shown at 18a, and an upwardly curved or coned lower surface, as shown at 18b, to assist fitting the lid 11 into the aperture of a container when the latter is being closed. In order to ensure that the wall portion 16 properly cooperates with the corresponding container portion, shown as a container lever ring 22 with a rolled lower edge 23 in Figure 3, it is desirable to provide inner support for the wall portion 16. This can take the form of a plurality of triangular supporting struts or webs 21 located at spaced intervals around the periphery of the lid 11.

Each strut or web 21 preferably is moulded with the rest of the lid 11 so as to extend as shown, viz.

over that part of the inner surface of the wall portion 16 which corresponds to the sealing fins 18 on the outer surface and over that part of the under surface of the central panel 12 which corresponds to the wide shallow recess 13. The increased thickness of the panel 12 per se ensures that the entire top part of the lid 11 within the flange 17 has generally equivalent stiffness characteristics, by reason of this arrangement. The struts or webs 21 provide additional stiffness so that the thin part of the lid 11 below the recess 13 has the same general characteristics as the panel 12 per se.

Figure 3 shows what happens to the fins 18 when the lid 11 is fitted into the aperture of a corresponding can or other container, having a lever ring with a portion 22 designed to cooperate with the side wall portion 16 of the lid 11. The fins 18 are forced upwardly as the lid 11 is fitted into place and their shape ensures that they then tend to press outwardly against the inner surface of the container portion 22 and so form a good seal. The lowermost fin 28 is placed so that it passes below the rolled edge 23 being the rim of the container portion 22 and it can then regain its usual configuration relative to the wall portion 16, with the flange 17 in contact with the upper portion 24 of the lower ring of the can. This helps to retain the lid 11 in place on the can, even if there is some excess pressure inside due, for instance, to elevated temperature conditions and this also overcomes any tendency for the elastic memory in the plastics material to cause the lid to rise in the container aperture and eventually break the seal. Polypropylene lids according to this invention are cheaper to make and at least as reliable and satisfactory in use as tinplate and other metal lids.

Claims

1. A container lid, having a portion for sealingly engaging with a corresponding portion of a container to which the lid is to be fitted, wherein the lid portion comprises at least one flexible annular fin which extends generally radially outwardly of and circumferentially around the lid and which is arranged to be deformed when the lid is fitted to the container so as to provide sealing engagement between the lid portion and the container portion.

2. A lid according to claim 1, wherein two or more of the annular fins are provided.

3. A lid according to claim 2, wherein the one or more annular fins are deformed by flexing away from the container as the lid is fitted thereto.

4. A lid according to any preceding claim, wherein the lowermost fin is positioned upon the lid portion so as to be situated beneath the container portion when the lid is fitted to the container and is thus allowed to resume its normal position relative to the lid portion.

5. A lid according to any preceding claim, wherein the lid portion comprises a side wall portion dependent form the periphery of a circular centre panel of the lid.

6. A lid according to claim 5, wherein the underside of the or each fin or of at least the lowermost one of a plurality of such fins is upwardly curved or coned.

7. A lid according to any preceding claim, wherein a plurality of supporting struts or webs are provided between the lid portion and the peripheral region of the underside of the lid.

8. A lid according to any preceding claim, wherein the lid portion with the one or more fins depends from the periphery of a generally flat circular central panel, an annular recess is provided in the upper surface around the periphery of the lid and a radial flange extends radially outwardly of the annular recess.

9. A lid according to any preceding claim, comprising a one-piece plastics moulding.

10. A lid according to any preceding claim, which is made of polypropylene.

11. A container lid according to any preceding claim, substantially as described with reference to Figure 1 or Figures 2 and 3 of the accompanying drawings.

12. A container having a lid as defined in any preceding claim.