Closure with plastisol liner defining a retaining bead

This relates to a closure utilizing a liner which is formed of plastisol or like material which puffs or expands upon curing after the liner has been applied. By providing the liner with a skirt portion and by increasing the radial thickness of a lower part of the liner skirt portion through a shaping of the skirt of the closure shell, the cured liner skirt portion will expand differentially and form, on the inner surface of the liner skirt portion, a bead which will snap over and lock beneath a bead on a container neck finish to lock the closure in a container sealing position. The closure may be removed and reapplied to reseal the container.

This invention relates in general to new and useful improvements in 
closures for containers wherein the closure is provided with a plastisol 
liner for forming 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 primarily 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 expansion 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 contoured 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 axially adjacent 
portions of the liner skirt portion. This bead, integrally formed on the 
liner skirt portion, is engageable 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 inwardly 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 in 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 utilization of a plastisol for 
forming the liner wherein the percentage of puffing increases, within 
limits, as the thickness of the plastisol increases. 
With the above and other objects in view that will hereinafter appear, 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.

Referring now to the drawings in detail, it will be seen that there is 
illustrated in FIG. 1 a conventional container 10 which includes a body 12 
terminating at its upper end in a neck finish 14. The neck finish 14 
carried a closure formed in accordance with this invention and generally 
indentified by the numeral 16. 
Referring now to FIG. 2, it will be seen that the illustrated container 10 
if 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 includes an external locking bead 20 which is integrally formed on 
the outer surface of the neck finish 14 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 provided with a plastisol liner, generally 
identified by the numeral 24. The shell 22 may be provided with a radially 
inwardly directed locking bead or other means for direct locking 
engagement with the container neck finish. Normally, the liner 24 is of an 
extent only to assure sealing with the surface 18. 
The shell 22, for the most part, is of a conventional construction and 
includes an end panel 26 surrounded by an axially inwardly opening channel 
portion 28. The 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 28 and does not materially 
extend axially down the skirt. 
In accordance with this invention, instead of the skirt 30 being 
cylindrical the full height thereof, the skirt 30 has an upper cylindrical 
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 FIG. 3, it will be seen that the liner 24 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. Because 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 have, in the 
skirt portion thereof, an internal surface which, in cross section, is a 
straight line. This internal surface is identified by the numeral 44 and 
preferably 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 that upon being heated 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 enlarging the shell skirt 30 and thereby 
providing for an increased thickness in the lower part of the liner skirt 
portion 40, as at 46, it will be apparent that when the liner material 
puffs upon being curved 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 liner 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 directed bead identified by the numeral 48. 
Referring now to the graph of FIG. 5 it has been found that with certain 
plastisols, particularly plasticized polyvinyl chloride that contains 
additives such as pigments, lubricants, stabilizers, 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 puff rate of such plastisols in accordance with an 
increase in thickness. It will be seen that when the thickness varies 
between 0.010" and 0.031", 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 0.050". 
With particular reference to FIG. 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: 
______________________________________ 
DIFFERENTIAL PUFF 
FINAL 
POSITION 
INITIAL THICKNESS 
THICKNESS (ACTUAL) 
______________________________________ 
A .013 .026 
B .012 .024 
C .013 .025 
D .016 .030 
E .020 .040 
F .025 .046 
G .031 .052 
H .036 .059 
I .041 .064 
J .041 .060 
K .040 .058 
L .042 .059 
M .036 .060 
N .029 .058 
O .021 .054 
P .013 .045 
Q .007 .032 
______________________________________ 
Inasmuch as the thickness of the plastisol of the uncured liner 24 may fall 
within this increased puff rate for the particular plastisol, this can be 
advantageously 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 controlling the radial outward enlargement of the skirt 
30 of the shell, the contour of the bead 48 may be specifically 
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 container neck finish, wedges 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. After 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 resealed. 
Although only a preferred embodiment of the closure has been specifically 
illustrated and described herein, it is to be understood that minor 
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, without 
departing from the spirit and scope of the invention as defined by the 
appended claims.