Note: Descriptions are shown in the official language in which they were submitted.
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CLOSURE FOR THIN-WALLED CONTAINERS
HAVING A MULTI-LEAD THREADED NECK
James Taber
John Tomala
F. Paul Marshall
The present invention relates generally to
closures for containers and, more particularly, to a
gasketed closure for thin-walled, flexible containers
having a multi-lead threaded neck. In this regard, an
important aspect of the present invention is directed to a
gasketed closure and thin-walled, blow molded bottle
combination, wherein the closure and bottle neck have
multi-lead threaded constructions and the gasket includes
a thermoplastic elastomer and has a profile that resists
mouth-distorting forces produced by the mating engagement
of overlapping end portions of the multi-lead threads on
the closure and bottle neck.
Plastic closures for containers having a thin
wall construction, such as, for example, extrusion blow
molded bottles, desirably must be capable of high speed
application and also of accommodating imperfections in the
shape of the neck finish to provide effective sealing of
the container. Unlike conventional metal caps, these
plastic closures often do not employ a sealing gasket or
liner, but instead rely upon the properties of the plastic
and the interior cap geometry to effect a seal with the
container or bottle to which the closure is applied.
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U.S. Patent No. 3,901,404 describes a typical
linerless plastic closure which utilizes three sealing
surfaces which are integrally formed with the cap shell.
These sealing surfaces engage the neck of a bottle to
which the closure is applied along its inside surface, top
surface and outside surface. The closure and bottle neck
are of a single-lead, threaded construction. During
tightening of the closure onto the bottle neck, the cap
deforms or flexes to cause the sealing surface to move
into flush sealing engagement with a bottle neck at both
its top surface and outside surface. This closure, while
suitable in many applications, suffers from the lower
capping speeds associated with single-lead threaded
constructions and can exhibit a potential for a less than
satisfactory leakage rate particularly where there are
significant imperfections in the neck finish of the blow
molded bottle.
A relatively recently introduced dairy closure
has found success in overcoming some of the problems
associated with the closure of U.S. Patent No. 3,901,404
by employing a thermoplastic elastomer top-seal gasket on
the inside of a single-lead threaded closure. As such,
this dairy closure provides improved sealing, however, it
does not enjoy the higher capping speed rates and other
advantages associated with multi-lead threaded
closures/container neck finished constructions.
The utilization of multi-lead threaded
constructions, however, while affording increased capping
speeds produces mouth-distorting forces on the container
neck. In particular, at locations wherein the ends of the
multiple individual threads on each of the closure and the
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container bottle neck are in axially-spaced, overlapping
relation, increased forces are imparted to the container
neck in comparison to the forces imparted along the
periphery of the neck wherein the individual threads are
in axially-spaced, non-overlapping relation. This causes
the container neck and mouth to ovalize or otherwise
distort by exerting forces thereon which urge the non-
overlapped thread sections outward and thereby creates a
potential for increased leakage sites wherein the out-of-
round container mouth does not seal with the circular,
non-deformed liner or gasket.
The present invention overcomes the above-
mentioned problems and disadvantages by providing a novel
closure/thin-walled container combination wherein both the
closure and neck of the thin-walled container are of
multi-lead threaded construction and the closure includes
a resilient gasket that both forms a top seal with a
generally flat annular sealing surface that surrounds the
open mouth of the container and resists mouth-distorting
forces produced by the mating engagement of overlapping
end portions of a multi-lead threads on the closure and
bottle neck when the closure is applied to the container.
It is, therefore, a general object of the
present invention to provide a new and improved gasketed
closure cap and thin-walled container combination.
Another object of the present invention is to
provide a novel gasketed closure cap which is particularly
suited for use with a blow molded, thin-walled container
or bottle that both accommodate irregularities and
imperfections associated with the end finish of such
container or bottle and also allows for high speed capping
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rates associated with multi-lead threaded constructions on
both the interior of the cap skirt and exterior of the
neck of the container.
Another object of the present invention is to
provide a thermoplastic elastomer gasketed closure which
is especially suitable with use for a blow molded, thin-
walled-container or bottle composed of high density
polyethylene or polyethylene terephthalate wherein both
the closure and neck of the container or bottle have a
multi-lead threaded construction.
These and other objects of the present invention
will be apparent from the following detailed description
taken in conjunction with the accompanying drawings
wherein like reference numerals refer_to like parts and in
which:
Fig. 1 is an exploded perspective view of the
closure and container (partially shown) in accordance with
a preferred embodiment of the present invention with
portions of the closure broken away;
Fig. 2 is a vertical sectional view illustrating
a closure of Fig. 1 applied to the container of Fig. 1;
Fig. 3 is an elevational view of the closure
shown in Fig. 1;
Fig. 4 is a top plan view of the closure shown
in Fig. 1;
Fig. 5 is a bottom plan view of the closure
shown in Fig. 1;
Fig. 6 is a sectional view taken along line 6-6
of Fig. 4;
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Fig. 7 is a 360° thread development view showing
the two-lead thread construction of the closure cap shown
in Fig. 1;
Fig. 8 is a vertical sectional view illustrating
a portion of the container shown in Fig. 1;
Fig. 9 is a 360° thread development view of the
two-lead thread construction of the bottle shown in Fig.
1;
Fig. 10 is a top plan view of the gasket shown
in the closure cap of Fig. 1; and,
Fig. 11 is a sectional view taken along the line
11-11 of Fig. 10.
Description Of The Preferred Embodiment
Referring to the drawings and with particular
reference to Fig. 1, a closure cap embodying the present
invention is generally designated by the reference numeral
10. As shown, closure cap 10 includes a skirt 11, an end
panel 12, a separate gasket 13 adhered or bonded to an
inside surface of the end panel, a tamper-indicating band
14 and a pair of multi-lead threads 15, 16, the end
portions of which are in axially-spaced, overlapping
relation to each other. As shown in the illustrated
embodiment the skirt 11, end panel 12, and tamper
indicating band 14 are integrally formed by molding and
are composed of a thermoplastic polyolefin such as, for
example, polypropylene, polyethylene, and copolymers
thereof.
Closure cap 10 is in overlying relation to a
bottle 17 having a neck portion 18, the exterior surface
of which is provided with a pair of multi-lead threads 19,
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20 which are adapted for mating engagement with the
threads 15, 16 on the cap 10. A retaining bead 21 is
axially-spaced below the threads 19, 20 for cooperative
relation with the tamper-indicating band 14 when the
closure cap 10 is fully seated on the bottle 10. As
shown, the end portions of multi-lead threads 19, 20 are
in axially-spaced, overlapping relation to each other and
the neck 17 terminates in a generally flat annular sealing
surface 22 which surrounds an open mouth 23.
While bottle 17 can be formed by any suitable
method of construction, it is preferably formed by
extrusion blow molding from thermoplastic materials such
as, for example, high density polyethylene, polypropylene
or polyethylene terephthalate. As such, the neck 18 and
annular sealing surface 22 exhibit flexibility and are
subject to minor variations which are characteristic of
and inherent in the extrusion blow molding process.
In accordance with an important aspect of the
present invention, gasket 13 is composed of a
thermoplastic elastomer which possesses easy
processability and rubbery mechanical performance.
Typically, the gasket or liner composition comprises a
thermoplastic component and a torque release modifier
component with the thermoplastic component consisting
essentially of a moldable, saturated A-B-A thermoplastic
elastomer block copolymer. The torque release component
can be selected from a variety of well known suitable
materials such as, for example, fatty acid amides and
mixtures of fatty acid amides.
A particularly suitable thermoplastic elastomer
comprises a saturated A-B-A block copolymer derived from
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styrene and butadiene units such as, for example, a
styrene-butylene-styrene (SBS) block copolymer or a
styrene-ethylene-butylene-styrene (SEBS) type block
copolymer which possesses about twenty to forty percent
styrene and sixty to eighty percent ethylene-butylene co-
monomers. These SEBS polymers have polystyrene endblocks
and ethylene-butylene midblocks. As such, these materials
possess excellent direct bonding performance, as well as
high temperature hermetic sealing characteristics, even
under pasteurization, hot fill, and retort processing
conditions. Additionally, they provide a desirable
balance of mechanical properties combined with odorless
and tasteless performance which is important in food
packaging applications.
As best shown in Fig. 2, the annular sealing
surface 22 of bottle 17 cooperates with a generally flat
annular surface 25 on the outer periphery of liner or
gasket 13 to form a top seal when the closure 11 is fully
seated on bottle 17. Additionally, annular sealing
surface 25 of gasket 13 extends inwardly and downwardly
forming a tapered circular rim 26 having an inwardly and
downwardly inclined surface 27 that engages an inner edge
24 of the annular sealing surface 22 of bottle 17 and
serves to stabilize the container mouth during application
of the closure 11 to containers or bottle 17 and thereby
resist mouth-distorting forces produced by the mating
engagement of the overlapping portions of the multi-lead
thread constructions on the closure cap and container neck
during application of the closure to the container.
Referring to Figs. 3-6, the sidewall or skirt 13
of closure cap 10, is, in a preferred embodiment, provided
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with a plurality of closely-spaced vertically extending
ribs to facilitate rotational application, removal and
reapplication of the closure cap 10 to a container. Skirt
13 extends downwardly into an enlarged cylindrical section
28, the terminal portion of which is connected to tamper-
indicating band 14. In the illustrated embodiment, the
tamper indicating band is of so-called slit construction,
that is it is secured to enlarged cylindrical section 28
by a discontinuous circumferential slit 29 which readily
permits detachment of the tamper indicating band from
enlarged cylindrical section 28 when the closure cap is
initially removed from the container. It will be
appreciated, however, that the tamper indicating band can
also be integrally connected to enlarged cylindrical
section 28 by a plurality of circumferentially disposed
fracturable bridges formed during the molding of the cap
shell itself.
As best shown in Fig. 3, a plurality of drain
holes 30 are provided in tamper indicating band 14 for
facilitating the discharge of liquids during the
processing of a container to which the closure cap has
been applied. Tamper indicating band 14, as best shown in
Fig. 6, includes an upper portion 14a hingedly connected
at 14c to a lower foldable band section 14b. As shown in
Fig. 2, the terminal portion of the foldable portion 14b
of tamper indicating 14 extends radially inwardly and
axially upwardly for engagement with retainer bead 21 so
that, upon removal of the closure cap 10 from container
17, the tamper indicating band 14 will readily separate
and become detached from the remaining portion of the
closure cap 10.
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Fig. 7 is a 360° thread development view of the
multi-lead threads 16 and 17 of closure cap 10. In this
regard, it will be appreciated that while the illustrated
embodiment includes two threads on the closure cap,
additional separate threads are within the scope of the
present invention. For example, the two-lead thread
construction shown in the illustrated embodiment is
particularly suitable for use with closure caps having a
nominal diameter of approximately 43mm. However, multi-
lead threaded constructions including 3,4 or more
individual threads can be suitably used in the practice of
this invention, particularly with larger diameter
closures. Fig. 9 is a 360° thread development view
illustrating the two-lead thread construction of the
container of the illustrated embodiment. As noted above
with respect to the closure cap, the multi-lead thread
construction of the container neck can include 3,4 or more
individual threads.
As shown in both Figs. 7 and 9, the individual
threads 16 and 17 in the closure cap have their respective
end portions in axially-spaced, overlapping relation to
each other and the individual end portions of the multi-
lead threads 19 and 20 in the container neck likewise have
their respective end portions in a similar axially-spaced,
overlapping relation. In the illustrated embodiment, the
respective overlapped portions of these threads are
oppositely disposed from each other along the
circumference of the closure cap and bottle neck. As
such, increased forces are imparted to the container neck
at locations wherein these end portions overlap, causing
the container neck and mouth to distort during application
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of the closure cap to the container. Since the gasket 13
in the closure cap generally retains its circular, as-
formed condition, distortion of the sealing surface on the
container neck can create a potential for increase leakage
wherein the out-of-round container mouth does not seal
with the circular, non-deformed liner or gasket.
In accordance with the present invention, the
inclined surface 27 of rim 26 of liner or gasket 13
engages with the inner edge 24 of the sealing surface 22
of container 17 and imparts a stabilizing force on the
edge 24 which resists distortion of the container mouth
caused by full application of the closure cap to the
container. Additionally, the support provided by inclined
surface 27 of gasket 13 on the edge 24 allows a capping
machine to apply increased torque during application and
allows improved control of the final position of the
closure as well as improved cap application torque
control.
As best shown in Figs. 10 and 11, in the
illustrated embodiment, rim 26 of gasket or liner 13
includes a vertically extending interior facing wall 31
which surrounds a radially interior circular disc-like
portion 32. In this regard, however, it will be
appreciated that portions of the gasket 13 which are
interior of the inclined surface 25 can be varied or
modified without affecting the cooperation of the inclined
surface 27 of gasket 13 on the inner edge 24 of the
container sealing surface 22.
The present invention has been described in the
context of a preferred embodiment with various
modifications thereof. It will be apparent to those
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skilled in this art, however, that modifications and
variations therefrom can be made without departing from
the spirit and scope of this invention. Accordingly, this
invention is to be construed and limited only by the scope
of the appended claims.
