Closure having an improved liner

A closure (2) having a metal shell (4) and a synthetic resin liner (10) having a first annular projection (12) and a concentric second annular projection (14). The second annular projection is adapted to engage and seal with an upper surface (24b) of the mouth (18) of a container with an inner peripheral surface (12a) of the second annular projection is adapted to engage the outer peripheral surface (24a) of the mouth (18) of the container.

TECHNICAL FIELD 
The present invention relates to a closure for a container and more 
particularly, to a closure of a type that has (a), a metal shell including 
a circular top surface and a substantially cylindrical skirt depending 
from the circular top surface, and (b), a synthetic resin liner that has 
been press formed inside the top of the shell. 
BACKGROUND ART 
In closures having a metal shell and depending skirt, it is very important 
that the shape of the synthetic resin liner installed inside the top of 
the shell have good sealing properties when applied to a container. In 
Japanese Patent Early Disclosure Number 53-65184, there is disclosed a 
liner having (a), an outer annular projection that provides an outer 
peripheral surface that is adapted to contact the outer peripheral surface 
of a mouth of a container to be sealed, and (b), an inner annular 
projection that provides an outer peripheral surface that contacts the 
inner peripheral surface of the mouth. Closures provided with liners of 
this type have sealing properties that are improved as compared to 
closures provided with liners of the types heretofore offered. 
Experiments performed by the present inventors, however, have indicated 
that there is a problem in that the closures as described above have 
decreased sealing properties when they undergo impacts of considerable 
size. 
It is therefore an object of the present invention to improve the shape of 
liners in closures of the type described above so that sufficient sealing 
properties will be retained even when these closures are subjected to 
considerable impact forces. 
GENERAL DESCRIPTION OF THE INVENTION 
We have found that a closure of the type described above may have its 
impact resistance considerably improved if, after the closure is applied 
to the mouth of a container, the liner has a shape so that the inner 
peripheral surface of a first annular projection engages the outer 
peripheral surface of the mouth and so that a second annular projection is 
positioned against the top surface of the mouth. 
Broadly described, a closure constructed according to the present invention 
has (a), a metal shell having a circular upper surface and a substantially 
cylindrical skirt depending from the outer edge of the circular upper 
surface, and (b), a synthetic resin liner press formed on the inside of 
the upper surface of the shell. The liner has a first annular projection 
concentric with and radially outward of a second annular projection. The 
first annular projection provides an inner peripheral surface that is 
adapted to contact the outer peripheral surface of the mouth of a vessel 
that is to be sealed. The closure is characterized in that the second 
annular projection is positioned so that it is adapted to lie against the 
upper surface of the mouth and to seal with the upper surface of the 
mouth. 
Preferably, the projected height of the second annular projection is less 
than the projected height of the first annular projection, and the second 
annular projection gradually decreases in thickness toward the projected 
end. The second annular projection preferably has its outer peripheral 
surface inclined in a radial direction toward the projected end, and 
should be formed so that it bends in the radial direction when it is 
sealed to the upper surface of the mouth. It is also possible to form the 
liner, as may be required, so that it has a third annular projection 
inside the said second annular projection where this third annular 
projection has an outer surface adapted to be positioned against the inner 
peripheral surface of a mouth of a container. 
A closure of the present invention is adapted for use as a so-called 
roll-on type of closure where screw threads are formed on the outer 
peripheral surface at the mouth of the container that is to be sealed, and 
where the closure is sealed to the mouth part by applying deformation 
forces along the screw threads in the skirt portion of the shell so that a 
shoulder of the shell is deformed inward in the radial direction where it 
mounts and seals the mouth. However, the present invention is not 
restricted to closures of this specific type, and the invention can also 
be applied to closures of the ordinary roll-on type where no deformation 
is applied to a shoulder of the shell and to closures of various sorts 
such as the so-called screw type closures where screw threads are 
previously formed in the skirt before mounting of the closure on the 
container.

BEST MODES FOR CARRYING OUT THE INVENTION 
Referring to FIG. 1, there is illustrated a closure 2 including a metal 
shell 4 having a circular upper surface 6 and a substantially cylindrical 
skirt 8 depending from the outer edge of the circular upper surface. A 
synthetic resin liner 10 is press formed on the inside of upper surface 6 
of shell 4. Metal shell 4 can be formed by a suitable method known to 
those skilled in the art from suitable metal elements that are easily 
deformable and may also be press formed using sheets of aluminum based 
alloys, tin plate or chromium plated sheet, and particular aluminum based 
alloy sheet. Synthetic resin liner 10 is made by press forming synthetic 
resins such as polyolefin resins including polyethylene and polyvinyl 
chloride, following known methods (for example methods as disclosed in 
Japanese Patent Publication 40-13156, Japanese Patent Publication 41-5588, 
Japanese Patent Publication 48-5706 Japanese Patent Publication 48-19886, 
Japanese Patent Early Disclosure 49-105689, U.S. Pat. Nos. 3,135,019, 
3,212,131 and 3,278,985). 
The liner 10 according to the present invention has, as shown in FIG. 2, 
two concentric annular projections 12 and 14. The outer first annular 
projection 12 is formed so that it will furnish an inner peripheral 
surface 12a that is adapted to contact the outer peripheral surface of the 
end of a mouth of a container when the closure is mounted and sealed onto 
the mouth of the container as will be explained later. The first annular 
projection 12 should be positioned at a considerable interval from the 
inner surface of a skirt 8 of shell 4 and should be installed 
substantially perpendicular to top surface 6 of shell 4, and inner 
peripheral surface 12a and outer peripheral surface 12b should both be 
substantially perpendicular to top surface 6 of shell 4. It is also 
desirable that the tip 12c of the inner surface be inclined outwardly 
toward the radial direction from the standpoint of ease of engagement with 
the mouth of a container. It is also desirable that base 12d of the inner 
peripheral surface form a footing that is inclined inwardly in the radial 
direction with the object of reinforcing first annular projection 12 and 
for ease of press forming. 
When there is considerable likelihood of fairly large impact forces acting 
on the shoulder of shell 4 (that is, at the boundary between top surface 6 
and skirt 8), it is desirable to form outer peripheral surface 12b of 
first annular projection 12 so that it contacts the inner surface of skirt 
8 of shell 4 as shown in FIG. 3, or to form a projecting cuff 16 between 
first annular projection 12 and skirt 8 of shell 4 as shown in FIG. 4 in 
order to increase the resistance to such impact forces. 
Second annular projection 14 is positioned on the inside of the first 
annular projection 12 and is arranged so as to be adapted to be positioned 
against the top surface of the mouth of a container to be sealed as will 
be explained further below. It is important that the second annular 
projection closely contact the upper surface of the mouth of the container 
when closure 2 is mounted and sealed on the mouth of the container. To the 
extent that these conditions are satisfied, second annular projection 14 
can be of any desired shape, but from the standpoints of adhesion strength 
against the top surface of the mouth of the container (this has an effect 
on sealing properties), ease of press forming and other various elements, 
the form illustrated in detail in FIG. 2 is the preferred form. In the 
preferred form of FIG. 2 it is seen that: 
(1) the projected height H2 of the second annular projection is smaller 
than the projected height H1 of the first annular projection 12, 
(2) the thickness of the second annular projection gradually decreases 
toward the projected end, and 
(3) the inner peripheral surface 14a is substantially perpendicular to the 
upper surface of shell 4 while the outer peripheral surface 14b is 
inclined inwardly in the radial direction toward the end of the 
projection, so that it bends inwardly in the radial direction when 
fastened to the upper surface of the mouth of the container as will be 
explained hereinafter. 
The dimensions of liner 10 following the mode described can be based on the 
dimensions of each part of the mouth of a container to be sealed. Table 1 
illustrates the dimensions of each part of a liner 10 relative to the 
outer diameter D1 and the inner diameter D2 of the mouth of a container as 
shown in FIG. 5 having the dimensions as set out in Table 1. 
TABLE 1 
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Particularly 
Suitable Ranges 
Suitable Ranges 
______________________________________ 
Outer diameter d1 of first 
1.03 D1-1.10 D1 
1.05 D1-1.08 D1 
annular projection 12 
Inner diameter d2 of first 
0.96 D1-1.02 D1 
0.98 D1-1.01 D1 
annular projection 12 
Outer diameter d3 of 
0.90 D1-0.97 D1 
0.92 D1-0.94 D1 
second annular 
projection 14 
Inner diameter d4 of 
1.02 D2-1.15 D2 
1.05 D2-1.12 D2 
second annular 
projection 14 
Projection height H1 of 
0.5 mm-1.6 mm 
0.85 mm-1.2 mm 
first annular projection 12 
Projection height H2 of 
0.4 mm-1.0 mm 
0.6 mm-0.8 mm 
second annular 
projection 14 
Thickness H0 of the base 
0.5 mm-1.8 mm 
1.0 mm-1.6 mm 
between first annular 
projection 12 and second 
annular projection 14 
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The mounting and sealing of a closure 2 on the mouth 18 of a container is 
illustrated in FIGS. 5 and 6. As is well known to persons skilled in the 
art, closure 2 is placed over the mouth 18 after which it is pressed down 
on mouth 18 by applying pressure to the outer surface of upper surface 6 
of shell 4. Under these conditions, skirt 8 of shell 4 deforms along screw 
thread 22 formed by the outer peripheral surface of mouth 18 to form screw 
thread 22 on skirt 8 (roll-on process), while the shoulder of shell 4 
deforms inwardly in the radial direction. When this is done, closure 2 is 
firmly retained against mouth 18 by the engagement between screw thread 20 
of mouth 18 and screw thread 22 formed by skirt 18, thus sealing mouth 18. 
When the closure 2 is thus mounted and sealed on mouth 18 of the container, 
first annular projection 12 of liner 10 deforms elastically to the shape 
illustrated in FIG. 6, based on the fact that closure 2 is compressed 
downward in FIGS. 5 and 6 and on the fact that the shoulder of shell 4 is 
deformed inwardly in the radial direction. The inner peripheral surface 
12a will contact outer peripheral surface 24a of mouth end 24 of mouth 18 
of the container. The second annular projection 14 of liner 10 will be in 
direct contact with top surface 24b of mouth end 24, based on the fact 
that closure 2 is compressed downward in FIG. 5 and 6, and by the means as 
shown in FIG. 6, the second annular projection bends elastically inwards 
in the radial direction, and contacts the upper surface 24b of mouth end 
24. The sealing of mouth 18 of the container is accomplished and 
maintained by the fact that inner peripheral surface 12a of first annular 
projection 12 contacts the outer peripheral surface 24a of mouth end 24 
while second annular projection 14 contacts the top surfce 24b of mouth 
end 24. 
FIG. 7 illustrates an example of deformation of a liner that includes a 
third annular projection. As shown, liner 110 has a first annular 
projection 112 and second annular projection 114 the same as first annular 
projection 12 and second annular projection 14 provided on liner 10 
described above, and in addition has a third annular projection 126 
positioned inside second annular projection 114. This third annular 
projection 126, as illustrated in detail in FIG. 8, furnishes outer 
peripheral surface 126a positioned against inner peripheral edge 124d of 
the upper surface of the container and inner peripheral surface 124c of 
the mouth end 124 of the container. 
When closure 102 containing liner 110 is placed over mouth 118 of a 
container and pressed downward as shown in FIG. 8, the inner peripheral 
surface 126a of third annular projection 126 will contact inner peripheral 
edge 124d of the upper surface and outer peripheral surface 124c of mouth 
end 124 of the container. By these means closure 102 is guided exactly 
into the required position and is positioned against mouth 118. 
Consequently, it is possible to have the so-called inclined pullover, with 
nearly total absence of mounting defects such as top cracking and wringing 
defects. 
When closure 102 is sufficiently pressed against mouth 118 of the container 
and mounted and sealed as required, third annular projection 126 is 
elastically deformed as shown in FIG. 9, and parts from mouth end 124 of 
the container. Of course, it is also possible to emplace third annular 
projection 126 so that when closure 102 is mounted and sealed as required 
to mouth 118 of the container, outer peripheral surface 126a of third 
annular projection 126 will seal onto inner peripheral edge 124d of the 
top surface and inner peripheral surface 124c of mouth end 124 of the 
container. However, when this is done, a part of the contact and sealing 
pressures between liner 110 and container mouth 124 will be borne by the 
sealing between outer peripheral surface 126a of third annular projection 
126 and inner peripheral edge 124d and inner peripheral surface 124c of 
mouth 124. This alone will decrease the sealing pressure between inner 
peripheral surface 112a of first annular projection 112 and outer 
peripheral surface 124a of mouth end 124, and the sealing pressure between 
second annular projection 114 and upper surface 124b of mouth end 124. 
Based on this, the sealing properties are considerably reduced when 
closures 102 are subjected to impact forces. 
EXAMPLES AND COMATIVE EXAMPLES 
Printing and a vinyl protective lacquer were painted onto one surface of a 
piece of aluminum base alloy sheet 0.25 mm thick, and the other surface 
was painted with an epoxy paint containing polyethylene oxide. The sheet 
was then pressed formed into shells so that the surfaces painted with 
epoxy paint containing polyethylene oxide became the inside surface of 
metal shells in the shape shown in FIG. 1. High pressure polyethylene 
(density=0.92 melt index=4.0) heated at 220.degree. C. was inserted into 
the shells which had been preheated to about 180.degree. C., was then 
press formed to form liners of the shape shown in FIGS. 1 and 2, to make 
sample closures of the present invention. The measurements of each part of 
the liners were as follows: 
Outer diameter d1 of first annular projection: 35.9 mm 
Inner diameter d2 of first annular projection: 33.8 mm 
Outer diameter d3 of second annular projection: 31.6 mm 
Inner diameter d4 of second annular projection: 30.5 mm 
Projection height H1 of first annular projection: 1.2 mm 
Projection height H2 of second annular projection: 0.7 mm 
Thickness HO of the base between the first annular projection and the 
second angular projection: 1.55 mm 
For purposes of comparison, comparative closures identical to the examples 
of the present invention described above were made except that the liner 
shape was like that illustrated in FIG. 4 of Japanese Early Disclosure 
53-65184. 
Then the closures comprising examples of the present invention and 
comprising the comparative examples were applied to the mouths of 
containers whose mouth ends had an outer diameter D1=33.83 mm and an inner 
diameter D2=2.70 mm. Impact tests were then conducted as described below. 
Impact Test 1 
As shown in FIG. 10, sulfuric acid and sodium hydrocarbon were packed in 
amounts of 1,000 ml into 1,000 ml containers after which the containers 
were sealed with sample closures. The containers were then left to stand 
in an upright position for one day in an isothermal chamber at 40.degree. 
C. The containers were then placed with their mouths pointing downwardly 
on a stand inclined at an angle .theta.=30.degree. and which had a high 
density polyethylene surface pasted thereon having a coefficient of 
friction of 0.08. The containers were placed on the stands at starting 
positions so as to give a total travel of 1=100, 200 and 300 mm. The 
containers were then allowed to fall naturally onto plastic and concrete 
masses emplaced at the lower end respectively. The number of containers 
tested for each test condition was n=10. The containers were left on their 
sides for one day after impact at ordinary temperatures, were further 
stood upright for one day, and then the number of containers with leakage 
was investigated. The results are shown below in Table 2. 
Impact Test 2 
As shown in FIG. 11, sample containers identical to those used in impact 
test 1 were placed with their mouths facing downward inside a 
perpendicular cylinder respectively at points where the drop distances 
were 1=30, 50, 70 and 100 mm. The samples were then dropped onto a steel 
mass having an angle of incline of .theta.=10.degree. emplaced in the 
cylinder bottom. The number of containers tested for each test condition 
was n=10. After impact the containers were treated in the same manner as 
in impact test 1, and then the number of containers suffering leakage was 
investigated. These results are shown below in Table 3. 
Impact Test 3 
As shown in FIG. 12, containers identical to those used in impact test 1 
and impact test 2 were placed on their sides and secured in place. Steel 
cylinders 45 mm in diameter, 50.8 mm high and 625 g in weight were then 
released toward the mouth ends on an inclined stand having an angle of 
incline of .theta.=30.degree.. The number of containers was n=10. Each 
cylinder was released from a point where the falling motion distance 1 was 
200 mm, and after impact frequencies respectively of 3, 5 and 7 times 
each, the containers were treated in the same manner as in impact tests 1 
and 2, and the number of containers with occurrence of leakage was 
investigated. The results are in Table 4 below. 
In the several impact tests described above, those containers where the 
initial gas volume setting of 4 Vol decreased to below 3.7 Vol in measured 
values were taken as having undergone leakage (also, 1 vol is the 
condition where the amount of carbonic acid gas dissolved in 1 cc of water 
at 15.5.degree. C. under 1 atmosphere of pressure is 1 cc). 
TABLE 2 
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Dropping 
Distance Comparative 
(mm) Examples Examples 
______________________________________ 
Plastic mass 
100 0 0 
200 0 3 
300 6 10 
Concrete mass 
100 0 3 
200 2 9 
300 3 9 
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(The numerical values shown in Tables 1 and 2 above and Table 3 below 
depict the number of bottles incurring leakage among 10 samples.) 
TABLE 3 
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Dropping 
Distance Comparative 
(mm) Examples Examples 
______________________________________ 
30 0 9 
50 0 10 
70 0 10 
100 1 10 
______________________________________ 
TABLE 4 
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Dropping Comparative 
Frequency Examples Examples 
______________________________________ 
3 0 0 
5 0 7 
7 9 9 
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