Note: Descriptions are shown in the official language in which they were submitted.
CLOSURE WITH PLASTISOL LINE~
DEFINING ~ RETAINING BEAD
This invention relates in general to new and
useful improvements in closures for containers wherein
the closure is provided with a plastisol liner for form-
ing a seal with the container neck finish, and more
particularly to a modified closure wherein the plastisol
liner has an integral bead for locking engagement on a
container neck finish bead.
It is conventional to provide closure caps with
a shell having disposed therein a plastisol liner for
forming a seal with the end finish of a container. Such
liners normally have pximarily only an annular sealing
surface, although the liners may extend slightly down the
skirt of the shell. The plastisol liners are applied in
their uncured state and then are cured, at which time a
certain degree of e~pansion takes place and this improves
the sealing properties of the liner. However, in order
that the liner may be applied at a high production rate,
it is con-toured by means of a molding punch, and thus the
internal surface of the skirt portion of the liner must
be of a straight line configuration in cross section.
Otherwise, there would be a wiping action as the molding
punch is removed.
In accordance with this invention, the skirt
portion of the plastisol liner, in its cured state, has a
lower portion in the form of a locking or retention bead
which projects radially inwardly beyond a~ially ad~acent
portions of the liner skirt portion. This bead, inte-
grally formed on the liner skirt portion, is engageable
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beneath a bead on a container neck finish so as to retain
the closure on the container against accidental removal,
although it may be readily pried from the container.
A principal feature of this invention is the
fact that the plastisol, when cured, expands or puffs.
This characteristic of the liner material is beneficially
utilized by varying the thickness of the liner in the skirt
portion thereof. By making a lower part of the liner skirt
portion of a greater thickness than the axially adjacent
part, when the skirt portion expands radially lnwardly upon
curing, the thinner part expands to a certain degree while
the thicker part expands to a much greater degree even when
the percentage of puffing i`n the two parts is the same.
Thus, by configurating the shell to have the lower part of
the liner skirt portion of a greater thickness, the liner
skirt portion may be provided with an integral bead after
curing while the uncured liner will have a straight line
cross-sectional interior surface.
A further feature of the invention is the utili-
zation of a plastisol for forming the liner wherein thepercentage of puffin~ increases, within limits, as the
thickness of the plastisol increases.
With the above and other objects in view that
will hereinafter appearl the nature of the invention will
be more clearly understood by reference to the following
detailed description, the appended claims, and the several
views illustrated in the accompanying drawings.
IN THE DRAWINGS:
Figure 1 is a top perspective view of a container
closed by a closure formed in accordance with this inven-
tion.
Figure 2 is a transverse vertical sectional view
taken generally along the line 2-2 of Figure 1, and shows
the specific cross section of the shell of the closure and
the liner and the interlocking relationship between the
liner and the container neck f;nish bead in accordance with
this invention.
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Figure 3 is an enlarged sectlonal view taken
through the closure shDwi`ng in solid lines the contour of
the plastisol liner as applied, and in dotted lines the
puffed plastisol liner after curing.
Figure 4 is an enlarged sectional ~iew similar
to Figure 3, but having thereon a number of lines upon
which test dimensions were taken of both the as applied
and puffed plastisol.
Figure 5 is a graph showing puff percentage
plotted against initial liner thickness.
Referring now to the drawings in detail, it will
be seen that there is illustrated in Figure 1 a conven-
tional container 10 which includes a body 12 terminatingat its upper end in a neck finish 14. The neck finish 14
carries a closure formed in accordance with this inven-
tion and generally identified by the numeral 16.
- Referring now to Figure 2, it will be seen that
the il~ustrated container 10 is formed of glass, although
it may be formed of other materials, and the neck finish
14 includes a free end sealing surface 18. The neck finish
14 also incluaes an external locking bead 2D which is
integrally formed on the outer surface of the neck finish
1~ and is axially spaced below the sealing surface 18.
In the normal formation of closures such as the
closure 16, there is a contoured shell 22 which is pro-
vided with a plastisol ]iner, generally identified by the
numeral 2~. The shell 22 may be provided with a radially
3Q inwardly directed locking bead or other means for direct
locking engagemen-t with the container neck fi]lish. Nor-
mally, the liner 24 is of an extent only to assure sealing
with the sealing surface 18.
The shell 22, for the most part, is of a conven-
tional construction and includes an end panel 26 surroundedby an a~ially inwardly opening channel portion 28. ~he
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shell 22 also includes a generally cylindrical skirt 30
which terminates in an integral inwardly directed curl 32.
Normally, the liner 24 is primarily restricted to the
channel 2g and does not materially extend axially down
the skirt.
In accordance with this invention, instead of
the skirt 30 being cylindri`cal the full height thereof, the
skirt 3~ has an upper cyli`ndrical portion 34 and a radially
outwardly and downwardly flared lower portion 36. Further,
the liner 24, in addition to including an annular seal
forming portion 38, also includes a skirt portion 40. It
is this skirt portion 40 to which the invention primarily
relates.
Referring now to Figure 3, it will be seen that
the liner 2~ is contoured by means of a molding punch 42
to the preselected contour with the plastisol which forms
the liner being in its uncured state. secause the molding
punch 42 must be withdrawable, it is obvious that it cannot
have any liner forming projections or recesses in the
peripheral surface thereof. Therefore, the as applied
uncured plastisol liner 24 must ha~e, in the skirt portion
thereof, an internal surface which, in cross section, is
a straiyht line. This i`nternal surface is identified by
the numeral 44 and prefera~ly has a slight slope thereto
so as to facilitate the withdrawal of the molding punch 42~
It will be readily apparent that this slope must be radially
outwardly and axially downwardly.
Considering first the assumption tha-t upon being
hea-ted and cured the plastisol material of the liner 24
will expand or puff and -that the expansion will be of a
uniform rate irrespective of thickness, it will be seen
that the internal contour of the liner 24 will be modified
from the uncured contour in accordance with variation in
thickness of the liner. Thus, by radially outwardly en--
larging the shell skirt 30 and thereby providing for anincreased thickness in the lower part of the liner skirt
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portion 40, as at 46, lt will be apparent that when the
liner material puffs upon being cured this increase in
thickness of the liner material at 46 will result in a
radially inwardly directed greater expansion of the lower
part of the skirt portion as opposed to the radially
inwardly directed expansion of an axially adjacent part of
the lîner skirt portion. Thus, by properly contouring the
skirt of the shell 16, the lower part of the cured plastisol
liner skirt 40 can be expanded to define a radially inwardly
lQ directed bead identified by the numeral 48.
Referring now to the graph of Figure 5, it has
been found that with certain plastisols, particular plasti-
cized polyvinyl chloride that contains additives such as pig-
ments, lubricants, stabili~ers, and puffing agents, the
percentages of which additives vary depending upon the
closure type and package treatment.
The plastisols, upon curing, do not uniformly
puff, but that there is an increase in the pu~f rate of
such plastisols in accordance with an increase in thickness.
It will be seen that when the thickness varies between .010"
and .031", there is a marked increase in puff rate with an
increase in thickness until the puff rate increase drops
off in generally the same manner as it rises, approaching
a puff percentage of 50% when the initial liner thickness
is on the order of .050".
With particular reference to Figure 4, it will be
seen that the actual thicknesses of the lower part of
the liner skirt, both uncured and cured, was taken along
a series of lines with the following results:
DI _ERENTIAL P~FF
POSITIONINITIAL THICKNESS FINAL THICKNESS (ACTUAL)
A .013 .026
B .012 .024
C .013 .025
D .016 .030
E 020 .040
J~2~
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F .025 .046
G Ø31 .052
H .Q36 .059
I .041 .064
J .041 .060
K .040 .058
L .042 .059
M .036 .060
N .029 .058
lQ O .021 O054
P .013 045
Q 007 .032
Inasmuch as the thickness oE the plastisol of
the uncured liner 24 may fall within this increased puff
rate for the particular plastisol, this can be advantage-
ouely utilized to control the puffing in the applied area
46 of the liner to specifically define the bead with a
contour which will interlock beneath the bead 20 of the
container neck finish. It is to be understood that by
2 a controlling the radial outward enlargement of the skirt
30 of the shell, the contour of the bead 48 may be spe-
cifically controlled.
The closure 16, as thus formed, may be applied
to the container 10 by a pressing on of the closure and
the bead 48 will engage over and beneath the bead 20 with
a "snap" action. The bead 48, upon application of the
closure to the containex neck finish, wedyes underneath
the bead 20.
The closure, when..applied as set forth above,
may be readily pried off or thumbed off, depending upon
the contour of the bead 48. AEter removal of the closure,
resealing is simply accomplished by applying the closure
on top the neck finish and pressing down until an audible
snap occurs.. When this occurs, the container has been re-
sealed.
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Although. only a preferred embodiment of the
closure has been specifically illustrated and described
herein, it ;.s to be unde.rstood that mi.nor variations may
be made in the closure,. most particularly the contour of
the skirt of the shell and the contour of the liner skirt
portion, wi`thout depart;ng from the spirit and scope of
the învention as defined by the appended claims.
