Note: Descriptions are shown in the official language in which they were submitted.
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A CLOSURE
FIELD OF INVENTION
The present invention relates to closures for pails and more particularly plastic pails that include a
gasket material to seal a closure relative to the pail to prevent egress of material.
5 BACKGROUND ART
Some prior art closures for plastic or polymer pails contained no gasket material and were often not
able to be properly sealed. The sealing difficulties were evident when pail and closure had sealing
surface imperfections caused by sink marks and warpage, resulting from the injection moulding
process, tool wear and mechanical damage in transport of the empty pails.
10 Other prior art attempted to solve this diff1culty by providing a relatively soft foam or cellular
gasket material to help the seal between the closure and the rim of the pail. These solutions have
been unsatisfactory to date in that, even with gasket material, prior art pails having closures with
gasket materials leaked after removal of long term top loads, when immediately inverted or tipped
to their side.
15 SUMMARY OF THE INVENTION
The invention provides a closure to engage the rim of a pail, said pail being of the type generally
constructed with a cylindrical side wall and a rim which extends radially outwardly from the top of
the cylindrical side wall, said closure including a gasket receiving portion to receive a gasket
therein, and at least one load bearing means adapted to limit transferral of compressive forces to
20 said gasket.
It is preferred that the gasket is given an initial compression produced by the securing of the closure
onto said pail thereby sealing said closure relative to said pail. The words "compressive forces"
includes forces which are reasonably expected and in excess of those reasonably expected during
transportation and other top load conditions.
25 The invention also provided a closure to engage the rim of a pail, said pail being of the type
generally constructed with a cylindrical side wall and a rim which extends radially outwardly from
the top of the cylindrical wall, the closure including a gasket receiving portion to receive a gasket
therein, and at least one load bearing means adapted to limit the travel of said closure toward said
pail, after said closure is releaseably attached to said pail.
30 Preferably the load bearing means is located adjacent to the gasket receiving portion. It is further
preferable that the load bearing means can be on either side of the gasket receiving portion or on
both sides. It is preferable that the load bearing means is an annular or part annular formation
however the load bearing means can also be a discontinuous or intermittent formation. When the
2 2161198
load bearing means is located adjacent to the gasket receiving portion it helps to retain the gasket
when the gasket and closure are being assembled.
Preferably the load bearing means engages a surface of the pail, such that compressive load, being a
force which would otherwise tend to compromise the integrity of the seal, is transferred to the pail
S by the load bearing means.
Preferably the gasket is made from a material capable of resuming its original profile immediately
after any loading has been removed. It is further preferable that the gasket material shall suffer
substantially no compression-set. By this it is meant that the ability of the gasket material to effect a
seal is not compromised under conditions of changing compression. Preferably the material chosen
for the seal is an olefinic thermoplastic vulc~ni7~te [O-TPV].
The invention further provides a method of sealing a closure relative to a pail, said method
comprising the steps of placing a gasket material to be captured by a gasket groove in said gasket
groove on said closure, and providing a load bearing means to control the amount of deformation or
compression applied to the gasket, or to limit the relative movement of the pail towards the closure,
once assembled.
The invention also further provides amethod of sealing a closure relative to a pail, said method
comprising the steps of:
providing a groove in a pail to receive a gasket
providing a load bearing means to control the amount of deformation or compression applied
to the gasket, or to limit the relative movement of the pail towards the closure, once
assembled
placing a gasket material in said gasket groove in said pail.
placing said closure on a pail
securing and sealing said closure to said pail.
25 The invention also further provides a closure and pail sealing mech~ni~m, said mechanism includes
a gasket receiving portion to hold a gasket made of a gasket material to seal the closure relative to
the pail, said gasket material being selected from a type of material known as an olefinic
thermoplastic vulcani7~te.
Preferably said gasket receiving portion is located on said closure.
30 Alternatively preferable is for the gasket receiving portion to be located on said pail.
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_ I 3
This inventive feature gives the advantage of providing a gasket material which has relatively low
compression set and a hardness which is generally not considered suitable for use with pails and
closures.
The invention also provides a closure to engage the rim of a pail, said pail being of the type
S generally constructed with a cylindrical side wall and a rim which extends radially outwardly from
the top of the cylindrical side wall, said closure including a gasket receiving portion to receive a
gasket therein, said gasket receiving portion having at least two sides constructed such that the
thickness in cross section of those two sides is at least 25% greater than the generally circular
central portion of the closure .
10 The generally circular portion of the closure is that surface area of the closure which covers the
circular opening of the pail.
It is preferable that a load bearing means is also provided to transfer compressive loads or to limit
travel between the pail and the closure.
It is further preferable that up to a maximum of some 400% greater thickness (than that of the
15 generally circular portion) is utilised in the above mentioned at least two sides.
It is further preferable that the material of the closure is a polyolefin and most preferably a high
density polyethylene or polypropylene.
The invention further provides a pail and a closure in combination, said closure of the type to
engage a rim of a pail, said pail being of the type generally constructed with a cylindrical side wall
20 and a rim which extends radially outwardly from the top of the cylindrical side wall, said closure or
said pail including a gasket receiving portion to receive a gasket therein, said closure or said pail
including at least one load bearing means adapted to limit transferral of compressive forces to said
gasket.
The invention further provides a pail and a closure in combination, said closure of the type to
25 engage a rim of a pail, said pail being of the type generally constructed with a cylindrical side wall
and a rim which extends radially outwardly from the top of the cylindrical side wall, said closure or
said pail including a gasket receiving portion to receive a gasket therein, said closure or said pail
including at least one load bearing means adapted to limit the travel of said closure toward said pail,
after said closure is releaseably attached to said pail.
30 Even if the thickness feature is used independently and not in association with the feature of a load
bearing means, the closure portion in contact with the pail will have improved contact thereby
providing a usefully improved sealing connection with the pail. This will improve leakage
prevention under usual and some unusual compressive load conditions. However, the load bearing
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means used in association with the thickness feature further advantageously limits the effect on the
gasket of more extreme compressive load conditions.
By itself, the load bearing means redistributes load which would result in excessive compression of
the gasket in situations where compressive forces are applied to the closure, when the closed pails
5 are in storage or transportation. A further advantage of the load bearing means when it is located
adjacent the gasket receiving portion, is that it helps to keep the gasket in place when it is assembled
into the closure, before the lid is attached to the pail.
Whilst these inventive features will provide an improvement over the prior art, pails and closures
embodying the invention(s) are still capable of destruction and damage if grossly overloaded.
10 BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present invention will now be described, by way of example only, with respect
to the accompanying drawings in which:
figure 1 is the side elevation of a pail and a closure;
figure 2 is a part cross-section through the rim of the pail and closure of figure 1;
15 figure 3 is a part cross-section through an alternative arrangement to that of figure 2;
figure 4 is a part cross-section through an alternative arrangement to that of figure 2;
figure 5 is a part cross-section through an alternative arrangement to that of figure 2;
figure 6 is a part cross-section through an alternative arrangement to that of figure 2; and
figure 7 is a part cross-section through an alternative arrangement to that of figure 2.
DETAILED DESCRIPTION OF DRAWINGS
In figure 1, a pail 2 and an attached closure 4 is illustrated. The pail 2 has a substantially cylindrical
side wall 10 which is (slightly tapered) to allow nesting of unlidded pails 2 with each other. Also the
base 6' [phantom outline in figure 2] of an adjacent pail 2 sits inside the cavity 8 in closure 4, and
rests on top of the circular portion 14, in a stack of closed pails 2. Generally the pail 2 is injection
moulded, as is the closure 4.
In figure 2, the substantially cylindrical side wall 10 of the pail 2 terminates in a radially outwardly
directed rim 12. The rim 12 has its uppermost surface designated by the numeral 44 and the radially
outermost portion 42. The closure 4 includes a vertical annular wall 16 formed with a horizontal
wall 18. The horizontal wall 18 is formed with a securing rim profile, generally designated 20. The
securing rim profile 20 includes walls 22, 24 and 26. The walls 22, 24 and 26 are annular in shape
and are formed integrally with each other. Below wall 22 is an internal annular vertical skirt 28. The
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skirt 28 in association with wall 22 help to provide extra sealing surface against the side wall 10 of
pail 2. Optional strengthening radial ribs 30 connect central portion 14 to the skirt 28. The
strengthening ribs 30, if used, help transfer stacking loads from a pail 2 above, through circular
portion 14 to securing rim profile 20, and hence to the side wall 10 of the pail 2 below.
5 Situated on outside wall 26 is a laterally (or inwardly radially or inwardly circumferentially)
projecting load bearing means 32. The outside wall 26 continues away from the wall 24 to undercut
34 that extends to form a levered releasing mechanism and grip 36.
A releasable securing recess 40 between load bearing means 32 and undercut 34 receives portion 42
of rim 12.
Formed with the walls 22, 24 and 26 and load bearing means 32 is a gasket receiving portion or
gasket groove 37, in which is positioned a gasket 38.The preferred gasket material is an olefinic
thermoplastic vulcanizate (O-TPV) and is an EDP~/polypropylene thermoplastic elastomer. Such
an O-TPV is SANTOPRENE [registered trade mark] grade 271-55. This material and grade were
selected despite its relative hardness (relative to its use as a pail gasket 38), because it has a
favourable characteristic of relatively low or no compression-set once compression is removed. This
allows the gasket 38 to resume its original profile immediately after compression or normally
encountered top loading forces have been removed from the closure 4.
When installing the gasket 38 into the closure 4, the gasket 38 is made to sit between walls 22, 24
and 26. Load bearing means 32 helps to hold the gasket 38 in place before the closure 4 is placed
upon the pail 2. The load bearing means 32 acts as a retainer so that once the gasket 38 is pushed
past the load bearing means 32, it will be retained in place partly due to compression and friction
forces and the occlusion of the gasket groove 37 by the load bearing means 32. The gasket 38 can
for example be 5 mm in cross sectional diameter whilst the cross-sectional diameter of the gasket
groove 37 can be approximately 4.5 mm. This 0.5mm difference in size is sufficient to create
compression and thus frictional forces.
In operation, the closure 4 and pail 2 operate as follows.
When a closure 4 is placed upon a pail 2, the movement of the closure 4 towards the pail 2 forces
the release mechanism 36 in an outwardly radial direction, allowing the undercut 34 to pass over
and by the portion 42. Once the portion 42 is in place in recess 40, the gasket 38 will have been
compressed against surface 44 of rim 12, and walls 22, 24 and 26 of the securing rim profile 20.
This is because the relative dimensioning of the gasket 38 and gasket groove 37, will force a part of
the gasket 38 to protrude past the load bearing means 32, allowing engagement with at least surface
44 on the rim 12 of pail 2. The load bearing means 32 rests upon surface 44 and limits further
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-
downward travel of surface 24 towards surface 44. However, whilst load bearing means 32 and
surface 44 are in contact, the gasket 38 is also in contact with the surface 44, to effect a seal
therewith, whilst simultaneously sealing with the gasket groove 37.
The thickness of wall 22 and 24 is at least 25% greater than the thickness of the central portion 14.
5 This extra wall thickness is provided, so that under expected compressive forces, it can limit relative
movement between wall 22 and wall 24. When the closure 4 is constructed from polyolefins such as
polypropylene or high density polyethylene, the characteristics of these materials together with the
relative thickness, will provide sufficient stiffness between the wall 22 and wall 24 to prevent
relative movement between them, under expected compressive forces. The wall 26 in this instance is
10 also thicker than central portion 14. This helps to limit excessive compression of the gasket 38 that
may occur if the closure 4 could move further into the pail 2. The undercut 34, in combination with
the load bearing means 32, keeps the gasket 38 under required compression.
The load bearing means 32 together with the rigidity of walls 22, 24 and 26, relative to each other,
help to prevent relative movement between the surfaces providing the seal.
In the arrangement of figure 3, 4, 5, 6 and 7, like features have been numbered with like reference
numerals.
In the arrangement of figure 3, the load bearing means 32 (of figure 2) has been removed and been
replaced with a lip 33, which does not engage the surface 44 of the rim 12 of the pail 2. The purpose
of the lip 33 is to hold the gasket 38 in the gasket groove 37, when it is assembled into the closure 4.
20 In this arrangement, the load bearing means 32 is a load bearing shoulder 27 which is formed on an
internal surface of side wall 10 of the pail 2. In this instance, the load bearing shoulder 27, is
approximately the same width as the thickness of the skirt 28. The skirt 28 engages the shoulder 27
and transfers compressive load to the pail 2, when the load is exerted on the closure 4. On the
outside of the side wall 10 of the pail 2, is a step 29, which is formed on the pail 2 to prevent a
25 reduction in the thickness of the side wall 10 and thus maintain strength of the pail 2.
In figure 4 the load bearing means 32 is formed from and is an extension of the wall 22, whereas in
figure 2, the load bearing means 32 was formed as an extension of the wall 26. The securing rim
profile 20 and the load bearing means 32 function in the same manner as that of figure 2. The lip 33
serves a similar purpose to the like numbered lip 33 in figure 3.
30 In figure 5, the arrangement illustrated is similar to a combination of figures 2, 3 and 4. The load
bearing means 31 and 32 are located on and are extensions of wall 26 and wall 22 respectively. The
securing rim profile 20 and the load bearing means 31 and 32 functions in the same manner as that
of figures 2 and 4. The shoulder 27 and skirt 28 also acts in the same manner in which the like
features operate in figure 3. Each of these load bearing arrangements performs a load bearing or
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7 2161198
travel limiting function, with the net effect being a cumulative one. Thus the arrangement of figure
5 is capable of carrying greater compressive stress by comparison to those arrangements having
only one load bearing means.
Figure 6 illustrates a further arrangement where the gasket 38 is housed in a gasket groove 37 near
the rim 12 of pail 2. The walls 22, 24, and 26 and undercut 34 serve as the securing rim profile 20.
When excessive load from base 6' is applied to the closure 4, or if a top load is placed on wall 24,
the wall 46 and rim 12, which together form the gasket groove 37, may be forced to move in a
direction towards each other. This will tend to pout gasket 38 forcing it harder against wall 26,
thereby not compromising the seal. The compression of the gasket 38 is limited by means of the
relatively short length of walls 46 and rim 12, thus very little leverage is applied.
Further, in figure 6 as with other arrangements depicted in figures 2, 3, 4 and 5, a load bearing
means made up of the walls 46, and rim 12 and wall 50 carries the compressive load, without
excessive transferral to the gasket 38. Whilst some distortion of the gasket 38 may occur under very
high vertical compressive loads, this distortion's ability to compromise the integrity of the seal is
reduced.
Illustrated in figure 7 is a further arrangement, whereby the gasket material 38 is not utilised against
the rim 12 of the pail 2. In this arrangement, side wall 10 has added to it a gasket groove 37 made
up of walls 52 and 54. The skirt 28 is shortened, and serves the same purpose as in other
arrangements. The walls 22 and 23 connects skirt 28 to wall 24.
The gasket groove 37 is proportioned so that it receives gasket 38. The wall 24 will then form a seal
with the gasket 38 when the closure 4 is positioned and secured to pail 2. In this arrangement, the
gasket 38 can be compressed to a predetermined amount, when the closure 4 is placed on the pail 2.
In this respect, the undercut 34 serves the same purpose as in other arrangements. The wall 52 is
dimensioned so as to bear the compressive load, or to limit the travel of the wall 24 of closure 4
relative to the pail 2. This will occur when the closure 4 is top loaded or another pail 2 is placed in
the cavity 8 of the closure 4. The wall 52 is a load bearing means and is further aided by another
load bearing means, which is the end 56 of side wall 10 on the pail 2. The end 56 of side wall 10
engages the closure 4 via wall 22. By providing two such load bearing means (end 52 and end 56)
greater compressive stress can be borne, with little to no compromising effect on the seal formed by
gasket 38.
Just as the arrangement of figure 5 is a combination of the arrangements of figures 2, 3 and 4, other
combinations of the arrangements of figures 2, 3, 4, 5, 6 and 7 can be made, depending upon the
sealing requirements and other structural needs of the combined closure 4 and pail 2.
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By limiting the compression load on the gasket 38, the integrity of the seal is maintained and the
deformation of the gasket 38 is controlled. This will also allow different types of seal material to be
utilised as the compression load can be controlled. This feature will result in warehousing and
transport situations whereby pallets can be loaded to an improved level by comparison with the
S prior art. Moreover, uncontrolled top loading, as tends to occur in transportation, will not result so
readily in instances where over-compression of a pail gasket leads to compression-set, that enables
leakage when the compressive load is first removed.
The foregoing describes several embodiments of the present invention and modifications by those
skilled in the art can be made thereto without departing from the scope of the present invention.
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