Container having a tamper proof lid

A one-piece plastic can lid 1, for use with a container of the lever ring type, has a periphery 20 which contacts an annular portion of the can wall 15, so as to center the lid 1 accurately relative to the can body. A recess 25 may be provided to enable a lever to be used to pry the lid 1 off the container. The recess 25 desirably includes a membrane 27 which is pierced when a lever is first used to open the container, so that rupture of the membrane 27 makes evident any unauthorized opening of the container. The lid 1 may also include one or more fins which form a seal in conjunction with an annular part 14 of the lever ring 16 of the container.

TECHNICAL FIELD 
This invention relates to containers with lids and is especially, but not 
exclusively, concerned with paint cans and other containers of the known 
kind which are provided with a lever ring, within which the lids fit in 
order to close the container. The lids of the containers of this invention 
can conveniently comprise one-piece plastic moldings, and the containers 
per se can be of many kinds, including plastic molded containers, 
tin-plate containers and others. 
BACKGROUND PRIOR ART 
An improved form of lid, preferably of a plastic material, for use in lever 
ring and other kinds of containers, is described in British Appln. No. 
8500701 (GB-A-2152913) and has 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. The present invention provides a further 
improvement in lids of such kind and a complementary improvement in such 
kinds of containers. 
The machinery used to put lids on containers is generally arranged to hold 
each lid in a generally horizontal position and either lower it into the 
ring of the container by moving it down the vertical axis of the latter or 
move it generally horizontally across the open top of a container in a 
slightly tilted attitude, so that a part of the periphery of the lid is 
abutted against the inside of the lever ring and a downward force is then 
applied at the opposite part of the periphery of the lid. Although the 
finned lids according to the aforementioned application are highly 
effective in sealing the containers to which they are fitted, misalignment 
can occur in a very small percentage of cases, which causes the fins to be 
excessively distorted at one part of the lid periphery, so that proper 
sealing is not achieved, for instance at the opposite part. In other 
words, the lids occasionally are not located in a generally concentric 
relationship with the lever rings of the associated containers and not 
even the natural tendency of the plastic material to achieve a condition 
of minimum stress is sufficient at times to allow a misaligned lid to 
centralize itself within the lever ring of the associated container. 
Misalignment is more likely to occur if the lids are applied by the second 
of the procedures mentioned or if they suffer damage at the periphery 
before or during application to the containers. 
SUMMARY OF THE INVENTION 
The present invention solves this problem in a simple and highly effective 
way, by providing corresponding components on the lid and the container, 
additional to those used to seal the one in relation to the other, which 
ensure at least substantially accurate centralizing of the lid in relation 
to the lever ring of the container. Also, the invention in a preferred 
embodiment couples this feature with tamper-evident means for opening such 
containers. 
According to the present invention, a lid is provided, preferably of a 
plastic material, having a portion for sealingly engaging with a 
corresponding portion of a lever ring of a container to which the lids is 
to be fitted, wherein the container includes an annular surface concentric 
with the container portion and the lid includes an annular surface 
concentric with the lid portion and arranged to contact the annular 
surface of the container and thereby maintain the lid and container 
portions in a concentric, and therefore sealed, relationship. 
Preferably, the annular lid surface is the periphery of a flange projecting 
outwardly from the lid portion, while the annular container surface is an 
inwardly-facing portion of the lever ring or container located radially 
outwardly from the container portion. In a preferred form of the lid, one 
or more recesses are provided in the peripheral part of the flange for 
receiving a lever for assisting in removal of the lid to open the 
container. In accordance with a preferred feature of this form of the lid 
of the invention, each recess includes a membrane which is ruptured or 
otherwise displaced when a lever is first used to assist removal of the 
lid from the associated container, whereby the lid is made tamper-evident. 
The lid is preferably provided with fins of the kind disclosed in 
theaforementioned application, so that the benefits of all these 
improvements are obtained together.

DETAILED DESCRIPTION 
While this invention is susceptible of embodiment in many different forms, 
there is shown in the drawings and will herein be described in detail 
preferred embodiments of the invention with the understanding that the 
present disclosure is to be considered as an exemplification of the 
principles of the invention and is not intended to limit the broad aspect 
of the invention to the embodiments illustrated. 
Referring now to FIG. 1 of the drawings, a lid 1 for a paint can is made of 
a suitable plastic material, for instance, polypropylene. The lid 1 
comprises a flat central circular panel 2, a dependent annular wall 4 and 
a projecting flange 5, extending radially beyond the annular wall 4 and 
effectively constituting an outwardly continuation of the central panel 2. 
The undersides of the panel 2 and of the flange 5 can be generally 
coplanar, while the upper surface 3 of the panel 2 projects somewhat above 
the upper surface 6 of the flange 5. Between these upper surfaces 3 and 6, 
a wide shallow rectangular-section recess 7 is provided in the lid 1. The 
central panel 2 is thus somewhat thicker and therefore more resistant to 
bending than the part of the lid surmounted by the recess 7. On the 
underside, below the recess 7, a plurality of triangular ribs 8 extend 
between the inside surface 9 of the wall 4 and the underside of the lid 
panel 2. 
On the exterior surface 10 of the wall 4, which is essentially cylindrical, 
a plurality of fins 11 are formed, there being five such fins 11, as shown 
in FIG. 1. Each fin 11 has a generally planar upper surface and an 
upwardly-coned or radiused under-surface, as described on the aforesaid 
application. A lowest fin 12 is provided also on the exterior surface 10 
of the wall 4 and its purpose is to spring back into the normal position 
shown in FIG. 1 and engage beneath the rolled lower edge 13 of a 
cylindrical dependent web or annular wall or flange 14 of the lever ring 
of the can body. The wall of the can body is shown at 15 and the lever 
ring at 16. The can wall 15 extends above the lever ring 16 and terminates 
in an outwardly-rolled edge 17, which as shown clearly in FIG. 1 is 
generally located above the upper surfaces 3, 6 of the lid 1, when the 
latter is fitted in place. When the lid 1 is thus fitted in place, the 
fins 11 form a seal in conjunction with the inside annular surface 18 of 
the dependent web 14. In addition, the lowest fin 12 becomes located 
beneath the rolled lower edge 13 of the web 14, when the lid 1 has been 
fully pressed down into the lever ring 16 of the can body. The dependent 
web or flange 14, with its substantial and generally-cylindrical interior 
surface 18, is the radially-inward component of the lever ring 16, which 
typically includes a channel formation, connecting the top of the 
dependent web 14 to the interior of the wall 15 of the can. Between the 
dependent web 14 and the remainder of the lever ring 16, which forms a 
seat or flat annular surface 13 surrounding the dependent flange or wall 
14 limiting further inward movement of the lid 1 into the can body which 
provides a secondary seal with the underside of flange 5. 
In this position, the annular peripheral surface 20 consituted by the outer 
edge of the flange 5 of the lid 1 abutts against the interior surface of 
the can wall 15 located above the lever ring 16. The interaction between 
these confronting annular surfaces therefore assists considerably in 
centralizing the lid 1 in the lever ring 16 and thereby in the can body as 
a whole. Thus, the one or more fins 11 and the lowest fin 12 comprise one 
or more portions of the lid 1 and each of these fins 11 sealingly engages 
a corresponding portion of the lever ring 16, namely, the appropriate part 
of the wall surface 18. In addition, the interior surface of the container 
wall 15, above the lever ring 16 and below the rolled edge 17, is an 
annular surface which is concentric with the lever ring wall surface 18, 
while the lid 1 includes an annular surface, viz. the exterior surface 20 
of the flange 5, which is concentric with the lid 1 per se. As the lid 
surface 20 contacts the interior surface of the container wall 15, this 
tends to maintain the lid fins 11 and the container wall surface 18 in a 
concentric and therefore sealed relationship. Any misalignment which might 
occur, if the rim of the flange 5 did not extend out to and contact the 
container wall, is thus obviated and the lid 1 and the container lever 
ring 15 naturally assume an accurately-coaxial relationship, in which the 
fins 11 exert a full sealing function. 
In order to enable the lid 1 to be removed readily from the body of the 
can, at least one recess is provided, as indicated by an arrow 21, two 
such recesses 21 being shown in FIG. 2 at diametrically-opposite places at 
the periphery of the lid 1. Each recess 21 can be a generally rectangular 
gap in the outer part of the flange 5, having an inner vertical wall 22, 
indicated as a broken line in FIG. 1. Instead of taking the form of a gap 
in the entire thickness of the flange 5, as shown at 21, each recess 21 
can include a membrane 21a which constitutes a thin part of the flange 5, 
as shown at two other diametrically-opposite places at the periphery of 
the lid 1. The membrane 21a (or one of them, if two or more recess 21 are 
provided) has to be pierced and so becomes ruptured, when the can is first 
opened. This form of recess thus gives evidence of opening of the can and 
makes the cap or lid 1 tamper-evident. A prospective purchaser can readily 
see whether any membrane 21a in the lid 1 of a paint can is undamaged and 
that the can has therefore not been opened since manufacture. The one or 
more recesses 21 allow a lever, such as the blade of a screwdriver, to be 
inserted between the lid 1 and the interior of the rolled edge 17 of the 
can body, after rupturing the membrane 21awhere this is provided, so that 
the lid 1 can be easily removed from the can body so as to open the 
latter. When this is done, the lower fin 12 is first displaced relatively 
downwardly, as the wall 4 rises, where the leverage is being applied, 
relative to the dependent web 14. It is found, in practice, that it is 
almost impossible to break the seal or otherwise disturb the position of 
the lid 1 in relation to the can body until the can is to be opened and 
that it is a relatively simple matter to use a simple lever in one or 
other of the recesses 21 to allow removal of the lid 1 to be effected. In 
order to re-close the can, it is a relatively simple matter to press the 
lid into the circular aperture defined by the annular web 14 and to 
maintain this pressure until the fins 11 have been brought into sealing 
engagement again with the interior surface of the web 14, the lower fin 12 
has restored itself into the locking position beneath the rolled edge 13 
and the external surface 20 of the flange 5 of the lid has again come into 
abutting contact with the interior surface of the can body wall 15 in the 
region between the rolled edge 17 and the lever ring 16. 
Referring to FIGS. 3 and 4, like parts to those shown in and described 
above in relation to FIGS. 1 and 2, have the same reference numbers. In 
this embodiment, a single arcuate recess 25 is provided in the lid flange 
5 and is defined between the exterior surface 20 of the lid 1, an arcuate 
surface 26 and the upper surface of a thin membrane 27 which forms the 
base of the recess 25. The periphery of the membrane 27 contacts the can 
wall at its chuck wall diameter. As shown in FIG. 4, an indicator, such as 
an arrow 28, indicating the position of the recess 25 can be printed on, 
molded into or otherwise provided on the upper surface 6 of the flange 5 
and instructions as to how to open the can by prying off the lid 1 can be 
similarly provided, e.g. in the form of suitable wording 29. 
The membrane 27 is much thinner than the lid flange 5 and, as the lid 1 is 
made of a plastic material, a lever, e.g. a screwdriver blade, can easily 
be made to pierce the membrane 27 in order to exert leverage between the 
rolled edge 17 and the underside of the flange 5 inwardly of the recess 
25. This leverage allows the lid 1 to be removed. The lid 1 can then be 
put back upon and removed from the can as often as desired, whereby the 
contents remain in a satisfactory state, as a seal is made by the fins 11 
and 12 and also by contact between the flange 5 and the lever ring portion 
19. Also, as the membrane 27 becomes ruptured by the lever used, when the 
lid 1 is first removed, it provides a clear indication as to whether the 
can has remained closed since manufacture and the first application of the 
lid, after the can has been filled. A ruptured membrane 27 provides clear 
evidence that the lid 1 of a can has been tampered with, so that this 
embodiment of the invention provides tamper-evident lids for containers. 
FIG. 5 illustrates an embodiment in which the tamper-evident means for 
opening the can are provided upon a lid which does not having sealing 
fins. 
The lid 30 shown comprises a one-piece plastic molding, having a central 
circular panel 31, a downwardly- and slightly outwardly-angled first 
annular wall 32, joined at its top to the panel 31 and and its bottom to 
an annular flange 33, an upwardly-directed second annular wall 34, 
preferably incorporating an outwardly-facing sealing bead 35, the wall 34 
being joined at its bottom to the flange 33 and at its top to another 
annular flange 36 incorporating the circular rim 37 of the lid 30. A 
recess 38, similar to the recess 25 shown in FIGS. 3 and 4 and including a 
rear arcuate surface 39 and a lower membrane 40, is provided at the 
periphery of the lid 30. An arrow and other markings, such as those shown 
at 28 and 29 in FIG. 4, can be provided. Again, the first use of a lever 
to pierce the membrane 40 causes it to rupture, so that unauthorized 
opening is made evident, although this does not prevent further use of the 
lid 30 to close the associated can. 
FIG. 6 shows in diagrammatic perspective view of how the membrane, e.g 21a, 
27 or 40, in the lid 1 or 30, appears, after a screwdriver, shown in 
dotted lines at 41, has been used to pry the lid from its container. 
The membrane, such as shown at 27 or 40, need not be provided at the 
underside of the flange 5. If the top surface of the membrane is level 
with that of the lid per se, a shallow groove defining the position of the 
arcuate surface, e.g. 26 or 39, can be incorporated in the top surface of 
the lid 5 or some other means can be provided on the lid 5 to indicate the 
location of the membrane and the underlying recess.