U.S. patent application number 11/160194 was filed with the patent office on 2006-12-14 for system and method for increased removal torque values for rationally engaging polymeric members.
Invention is credited to Rickie Althouse, David Bowers.
Application Number | 20060278602 11/160194 |
Document ID | / |
Family ID | 37523199 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060278602 |
Kind Code |
A1 |
Bowers; David ; et
al. |
December 14, 2006 |
SYSTEM AND METHOD FOR INCREASED REMOVAL TORQUE VALUES FOR
RATIONALLY ENGAGING POLYMERIC MEMBERS
Abstract
A torque retention apparatus and method for use with
container-closure combinations including selection of retainer or
other component materials such that variations in material
properties of the materials and/or dimensional changes in the
components over time contribute to substantially increased torque
retention. Selection of container contents and the configuration of
supplemental sealing and/or attachment features may further
contribute to the substantial increase in torque retention. A
fitment having an annular well and tubular wick retainer is
interposed between the container and the closure.
Inventors: |
Bowers; David; (Phoenix,
AZ) ; Althouse; Rickie; (Scottsdale, AZ) |
Correspondence
Address: |
SNELL & WILMER, LLP
ONE ARIZONA CENTER
400 E. VAN BUREN
PHOENIZ
AZ
85004-2202
US
|
Family ID: |
37523199 |
Appl. No.: |
11/160194 |
Filed: |
June 13, 2005 |
Current U.S.
Class: |
215/276 ;
215/344; 220/319 |
Current CPC
Class: |
B65D 41/0485 20130101;
B65D 47/123 20130101 |
Class at
Publication: |
215/276 ;
220/319; 215/344 |
International
Class: |
B65D 45/00 20060101
B65D045/00; B65D 45/32 20060101 B65D045/32; B65D 53/00 20060101
B65D053/00 |
Claims
1. A torque retention apparatus for use with a container and
closure combination, the apparatus comprising: a first retainer
formed on the container, said first retainer comprised of a first
polymer; a second retainer formed on the closure and configured to
engage said first retainer through application of a set torque
during installation of the closure on the container, said second
retainer comprised of a second polymer, said first and second
polymers selected such that a removal torque applied to disengage
said first and second retainers following an extended period of
engagement is substantially greater than fifty percent of said set
torque.
2. The apparatus of claim 1, wherein said removal torque is at
least equal to said set torque.
3. The apparatus of claim 1, wherein said first and second polymers
are selected from the group consisting of polypropylene,
polyethylene, polyvinyl chloride, and copolymers of the same.
4. The apparatus of claim 1, wherein said first and second
retainers comprise complimentary threads.
5. The apparatus of claim 1, wherein a substance contained by the
container is selected to interact with at least one of said first
and second polymers to contribute to said removal torque.
6. The apparatus of claim 1, further comprising a fitment
interposed between the container and the closure, said fitment
configured to attach to at least one of the container and the
closure, said fitment at least one of configured to and comprised
of a material selected to contribute to said removal torque.
7. The apparatus of claim 6, wherein said fitment is a wick holder
comprising: a tubular portion for receiving a wick; at least a
first sealing feature for sealingly engaging the closure; and at
least a second sealing feature for sealingly engaging the
container.
8. The apparatus of claim 7, wherein at least one of said first and
second sealing features contributes to said removal torque.
9. The apparatus of claim 8, wherein relative material properties
of said first and second polymers, interaction between container
contents and at least one of said first polymer, said second
polymer and said fitment, and friction generated by at least one of
said first and second sealing features cooperate to contribute to
said removal torque.
10. The apparatus of claim 7, wherein said fitment includes at
least one of a circumferential skirt for engaging the neck of the
container and an annular well surrounding said tubular portion.
11. The apparatus of claim 10, wherein said first sealing feature
is an annular projection contacting an outer sidewall of said well,
and said second sealing feature is an annular projection on the
closure contacting a complimentary annular grove in a top surface
of said fitment.
12. The apparatus of claim 1, wherein a first said removal torque
is between 100 percent and 250 percent of a first said set torque,
a second said removal torque is between 100 percent and 150 percent
of a second said set torque of twice said first said set torque,
and a third said removal torque is between 75 percent and 100
percent of a third said set torque of three times said first said
set torque.
13. A torque retention apparatus for use with a container and
closure combination, the apparatus comprising: a fitment interposed
between the container and the closure and attachable to at least
one of the container and the closure; a first retainer formed on
one of the container and said fitment, said first retainer
comprised of a first polymer; a second retainer formed on one of
the closure and said fitment and configured to engage said first
retainer through application of a set torque during installation of
one of the closure and said fitment on the container, said second
retainer comprised of a second polymer, said first and second
polymers selected such that a removal torque applied to disengage
said first and second retainers following an extended period of
engagement is substantially greater than fifty percent of said set
torque.
14. The apparatus of claim 13, wherein the closure is retained by
at least one of the container and said fitment.
15. The apparatus of claim 13, further comprising a friction
generating feature in addition to said first and second retainers
contributing to said removal torque.
16. The apparatus of claim 13, wherein at least two of a sealing
feature formed on one of the container, the closure, and said
fitment, a frictional feature formed on one of the container, the
closure, and said fitment, and a substance contained in the
container contribute to said removal torque.
17. An improved container-closure combination, the improvement
comprising: a first retainer of a first polymer formed on the
container; a second retainer of a second polymer formed on the
closure for rotational engagement of said first retainer by
application of a set torque, said first and second polymers
selected such that a removal torque required to disengage said
first and second retainers following an extended period of
engagement is substantially greater than fifty percent of said set
torque.
18. A method of increasing torque retention in rotationally engaged
combinations, the method comprising: selecting a first polymer;
forming a first retainer on a first component, said first retainer
comprised of said first polymer; selecting a second polymer;
forming a second retainer from said second polymer on a second
component for rotational engagement with said first retainer, and
applying a set torque between said first and second components to
engage said first and second retainers with frictional interference
between said first and second retainers, a relative difference in a
material property of said first and second polymers contributing to
a reduced degree of loss of the frictional interference over time
such that a removal torque required to overcome the frictional
interference following at least one of an extended period of
engagement at ambient temperature and a shortened period of
engagement at an elevated temperature is substantially greater than
fifty percent of said set torque.
19. The method of claim 18, wherein at least one of said forming
steps comprises forming at least one of said first and second
retainers from at least one of polypropylene, and polyethylene.
20. The method of claim 18, further comprising selecting a liquid
for interaction with at least one of said first and second polymers
to further reduce said degree of loss of said frictional
interference.
21. The method of claim 18, wherein said first forming step
comprises forming threads on a container, said second forming step
comprises forming complimentary threads on a closure, the method
further comprising forming a fitment configured to attach to at
least one of the container and the closure from at least one of
said first polymer, said second polymer, and a third polymer.
22. The method of claim 18, wherein said steps of selecting said
first and second polymers contribute to said removal torque being
in excess of said set torque.
Description
FIELD OF INVENTION
[0001] The invention relates generally to methods of increasing
torque retention in container-closure combinations including
resilient polymeric retaining features.
BACKGROUND OF INVENTION
[0002] Containers are commonly fitted with a removable cap or other
closure. Common container-closure combinations require application
of a set torque to the closure during assembly, generating friction
between complimentary retainers formed on the container and
closure. For example, a common closure includes internal features
such as threads or lugs for engaging external features such as
complimentary threads formed on the container exterior. Additional
closure and/or container features are commonly employed to form
various seals when advanced into sealing engagement by rotational
engagement of the threads. For example, an o-ring may be sealingly
compressed between the closure and container by application of
sufficient torque to the closure. Similarly, additionally container
fitments such as, for example, pour spouts or wick holders, may be
interposed between the container and closure.
[0003] In containers using resilient plastic threaded members, the
plastic material may exhibit creep, relaxation, or cold flow due to
the forces caused during application of the set torque during
installation or by expansion of materials within the container.
This creep or cold flow often causes a gradual loosening of the
threaded connection. In addition, plastic materials typically have
a low coefficient of friction, causing gradual movement and
loosening referred to as "backoff slippage" of the threaded
connection. It is a concern that excessive creep or backoff
slippage may compromise a seal or even result in separation of a
fitment or closure from a container.
[0004] Application of insufficient set torque during installation
of the closure on the container may affect performance of sealing
features during storage, shipping, and handling. Application of too
much toque may result in stripping of the threads or may render the
connection too tight for removal by hand. A concern with known
systems employing resilient polymeric components is that plastic
creep, material flexure, or backoff slippage may lead to a
reduction in the sealing forces initially generated by the set
torque. "Torque retention" or "torque reduction," as used in the
art, refer to relative degrees of variation between the set torque
and the removal torque. In laboratory and quality control testing,
the removal torque is often measured after an extended period at
ambient temperatures or after a shortened period at high
temperatures to simulate an expected shelf or storage life of the
product. The elevated temperature accelerates the creep, material
flexure, or backoff slippage of the plastic components.
[0005] Typically, set torques of two to four times the desired
removal torque are used to allow for expected torque reduction.
Thus, conventional configurations typically exhibit torque
retention of fifty percent or less. For example, a plastic cap
installed on a plastic container at a set torque of fifteen inch
pounds may require a removal torque of only three to eight inch
pounds.
[0006] In an attempt to enhance torque retention capabilities,
earlier systems have proposed increased thread depth, supplemental
thread elements, lugs, sealing rings, gaskets, and the like to
provide additional friction between the threads. Such systems have
achieved but modest increases in torque retention. Increased torque
retention serves to reduce the amount of initial set torque
required to obtain a desired removal torque. In some instances, it
may even be desirable that the removal torque exceed the applied
set torque, allowing for greatly reduced set torques during
production.
[0007] Accordingly, it is desirable to provide an apparatus and
method for significantly enhanced torque retention in
container-closure configurations. In particular, there is a need
for such configurations exhibiting retention of substantially more
than half of an applied set torque. Indeed, there is further a need
for configurations exhibiting removal torque values in excess of an
applied set torque value.
SUMMARY OF INVENTION
[0008] In accordance with various exemplary embodiments of the
present invention, selected combinations of polymeric materials,
retainer configurations, and/or interaction of polymeric materials
and container contents provide increased torque retention.
Increased torque retention serves to improve closure and fitment
seal performance and to reduce the amount of set torque required
during installation.
[0009] Increased torque retention may be accomplished through
selection of different polymeric materials for the container,
closure, and/or fitment such that relative material properties of
different components result in a significant increase in torque
retention over an extended period. The invention may also provide
friction in excess of that generated by the set torque during
installation, resulting in a removal torque greater than the set
torque.
[0010] Increased torque retention may also be accomplished by
selection of the composition of the container contents to obtain a
desired physical or chemical interaction with any of the materials
of the container, fitment, and/or closure. Sealing features and/or
friction generating features may also contribute to an increase in
torque retention.
[0011] These and other aspects of the invention shall become more
apparent when read in conjunction with the accompanying drawing
figures and the attached detailed description of exemplary
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The features and advantages of the present invention are
hereinafter described in the following detailed description of
exemplary embodiments to be read in conjunction with the
accompanying drawing figures, wherein like reference numerals are
used to identify the same or similar parts in the similar views,
and:
[0013] FIG. 1A is a plot showing torque retention of prior art
systems;
[0014] FIG. 1B is a plot comparing torque retention according to an
embodiment of the present invention with that of prior art
systems;
[0015] FIG. 1C is a plot comparing torque retention according to
another embodiment with that of prior art systems; and
[0016] FIG. 2 shows an exemplary threaded container, threaded
closure and interposed wick fitment having multiple sealing
features according to one embodiment of the present invention.
DETAILED DESCRIPTION
[0017] The following description is of exemplary embodiments of the
invention only, and is not intended to limit the scope,
applicability or configuration of the invention in any way. Rather,
the following description is intended to provide a convenient
illustration for implementing various embodiments of the invention.
As will become apparent, various changes may be made in the
function and arrangement of the elements described in these
embodiments without departing from the scope of the invention as
set forth herein.
[0018] That said, in the context of the present invention, methods
and apparatus described herein may find particular use in
connection with air freshener refill combinations including a
reservoir, fitment and cap. However, generally speaking, any
container and closure combination or other rotationally engaging
retainer combination may benefit from the present invention.
Accordingly, the terms "container," "refill," "reservoir", and
"bottle" as used herein are intended to interchangeably refer to
any first member having a retainer formed thereon. The terms
"closure," "cap," and "fitment" may be used interchangeably herein
and refer to any second member retained by a second retainer formed
thereon or retained between the first member and a second member
having a second retainer formed thereon.
[0019] Various embodiments of the present invention may be
described herein in conjunction with specific devices or products
and it should be appreciated that the scope of the present
invention should not be considered limited to those specifically
mentioned herein. As used herein "torque retention" refers to the
relative degree of variation between the set torque and the removal
torque for a given retainer combination. Increased torque retention
may also be described in terms of the ratio of removal torque to an
applied set torque, including ratios greater than one, i.e., where
the removal torque exceeds the applied set torque.
[0020] In accordance with the present invention, a container is any
reservoir, bottle, or repository and generally includes a hollow
body with a neck portion defining an opening therein. A closure is
any cap, cover, plug, or the like that is configured to cover or
seal the opening in the container, for example by threadably
engaging the neck of the container. A fitment is any plug, pour
spout, or dispensing mechanism configured to engage the container
opening in cooperation with a closure or independent of a closure.
The container, closure and/or fitment engage or cooperate with one
another by any number of cooperating retainer mechanisms such as
mating threads, lugs, skirts, ledges, projections, flanges, and the
like.
[0021] Container, closure, or fitment components may be injection
molded, blow molded, or thermoformed of any suitable plastic
material such as polypropylene, polyethylene, polyvinyl chloride,
copolymers of the same, or other suitable polymers. Alternatively,
components may be formed by machining of a bulk material or by any
other known manufacturing process. Various embodiments are
described herein in terms of polymers, but it should be understood
that any other suitable material such as glass, metal, and the like
may be used in accordance with the present invention. Increased
torque retention may be accomplished in cooperating retainer
mechanisms by any means that serves to increase the removal torque
required to disengage a closure from a container after an extended
period of engagement following application of a set torque.
[0022] Various torque retention properties of various embodiments
of the present invention will now be described with reference to
FIGS. 1A-1C. FIG. 1A illustrates an exemplary plot of torque
retention exhibited by prior art configurations. As illustrated, a
set torque is initially applied to the configuration of retainers.
Over time, the torque required to disengage the retainers settles
around or below one half of the initial set torque. As explained
above, this torque reduction is due to material creep, cold flow,
or other phenomenon.
[0023] FIG. 1B illustrates a plot of torque retention exhibited by
an embodiment in accordance with the present invention versus that
of the prior art shown in FIG. 1A. This figure illustrates the
significant increase in torque retention of substantially greater
than half of the applied set torque. Modest increases in torque
retention provided by the prior art still yielded only retention
values around or well below fifty percent. Thus, retention values
of substantially more than fifty percent are a significant
invention over the prior art.
[0024] FIG. 1C illustrates a plot of torque retention exhibited by
another embodiment in accordance with the present invention versus
that of the prior art shown in FIG. 1A. This figure illustrates a
torque retention ratio greater than one, i.e., a removal torque in
excess of the applied set torque.
[0025] In various embodiments, increased torque retention may be
attributed to an increase in friction due to a selection of
differing material properties, e.g., such as shrink rates,
coefficients of thermal expansion, elastic moduli, tensile
strengths, tensile moduli, flexural strengths, flexural moduli,
compressive strengths, compressive moduli or other properties of
the closure and the container. For example, increased shrink rates
of the closure relative to the container may serve to increase
friction between threaded interfaces as well as between
interference sealing interfaces. Materials may be selected based on
any material property or combination of material properties to
achieve the desired degree of torque retention.
[0026] As shown in FIG. 2, an exemplary container-fitment-closure
combination 2 includes a container 4 composed of polypropylene, a
wick fitment 6 composed of a linear low density polyethylene, and a
closure 8 composed of polypropylene. The polypropylene of container
4, polyethylene of fitment 6, and polypropylene of closure 8 are
selected such that the relative material properties lead to a
reduction in the loss of friction caused by creep or other
phenomenon over time. For example, dimensional changes of one
component relative to another may contribute to increased torque
retention. Exemplary material properties of the various selected
polymers include shrink rates, coefficients of thermal expansion,
elastic moduli, tensile strengths, tensile moduli, flexural
strengths, flexural moduli, compressive strengths, and compressive
moduli.
[0027] In various other embodiments, increased torque retention may
be accomplished through interaction of polymeric apparatus
components and the contents of container 4. This interaction may be
chemical or physical. For example, a chemical reaction between a
scented oil held by container 4 and the polymer or other material
of any of the apparatus components may increase the coefficient of
friction of the material and thus the torque retention of the
combination. Alternatively, the contents of container 4 may serve
to facilitate a reaction between two materials composing two or
more components of container-closure combination 2.
[0028] In accordance with various embodiments of the present
invention, various combinations of multiple engaging features
contribute to increased torque retention. With continued reference
to FIG. 2, an air freshener refill container 4 holds scented oil
that is drawn from container 4 by a wick (not shown). The wick is
retained by a wick fitment 6 attached to the neck of refill
container 4. Wick fitment 6 is a cylindrical disk having a central
tubular formation 10 for positioning the wick and including an
annular well 12, annular sealing groove 14, and a peripheral skirt
16 configured to engage a ledge 18 on the neck of container 4.
Closure 8 includes screw threads 20 to engage mating threads 22 on
container 4 and covers the wick and wick fitment 6 to prevent
evaporation of the scented oil during storage. Closure 8 further
includes an annular dam 24 on the underside of closure 8 for
sealing against the side of fitment well 12 when assembled. An
annular ridge 26 on the underside of closure 8 forms an additional
seal with annular groove 14 in fitment 6.
[0029] Rotational engagement of threads 20 and 22 advances closure
8 onto container 4, compressing fitment 6 therebetween. Advancement
of closure 8 onto container 4 also causes an interference fit
between closure dam 24 and the sidewall of fitment well 12 as well
as between closure sealing ridge 26 and fitment annular groove 14.
Shrinkage of fitment well 12 in excess of that of closure dam 24
may serve to increase the sealing frictional interference between
those features, resulting in an overall increase in the removal
torque required to separate closure 8 from container 4. Additional
gaskets, sealing rings, flanges, ribs, skirts, and the like may be
used to provide additional sealing mechanisms between container 4
and closure 8, fitment 6 and container 4, and/or fitment 6 and
closure 8. For example, multiple seals may be used to create a
series of sealed zones such that failure of one seal does not
result in leakage from the assembly as a whole.
[0030] Similarly, various attachment mechanisms such as, for
example, attachment lugs, secondary thread sets, or thread
variations (e.g., variations in thread depth, thread thickness, or
other thread irregularities towards the end or beginning of
engagement or along the full thread length), or any number of other
features may serve to provide increased friction or other
resistance to relative rotation of closure 8, container 4, and/or
fitment 6. Thus, it is understood that any number or type of
attachment or sealing mechanisms may be used in accordance with the
present invention to achieve an increase in torque retention,
including removal torques in excess of the applied set torque. It
is further understood that any combination of any of the above
described mechanisms (e.g., materials selection, interaction with
contained liquids, and additional sealing or frictional features)
or methods may be used to achieve increased torque retention or
removal torques in excess of an applied set torque.
[0031] In an exemplary method of assembly of the apparatus, fitment
6 is snap-fitted to container 4 and mating threads 20 and 22 are
then engaged by rotation of closure 8 relative to container 4.
Continued rotational engagement and axial advancement brings
various projections and recesses into sealing engagement as
described above. Finally, application of a set torque as shown in
FIGS. 2-3 generates residual forces including compression of and
friction between mating threads 20-22. Alternatively, fitment 6 may
be attached first to closure 8, with the combination then being
attached to container 4 by engagement of any suitable complimentary
features. Thus, closure 6 may be retained by container 4 or may be
retained by fitment 6 which may in turn be retained by container 4.
Any sequence or method of assembly or attachment of container 4,
fitment 6, and/or closure 8 may be suitably employed in accordance
with the present invention.
[0032] Tests were conducted with various container-fitment-closure
assemblies 2 according to the present invention. Test containers 4
were injection molded from polypropylene, wick fitments 6 of linear
low density polyethylene, and closures 8 of polypropylene. 120 test
assemblies 2 were configured essentially as shown in FIG. 2 and
described above. Containers 4 were filled with scented oil. Wick
fitments 6, with wicks mounted therein, were then snap-fitted to
test containers 4. Closures 8 were then threadably assembled to
containers 4 with set torques of between 3 and 10 inch pounds per
set. Test assemblies 2 were then heated to 120.degree. F., vacuum
tested to 12,000 ft. and placed back in the 120.degree. F. oven for
period of between twenty-four hours and one week to simulate the
effects of creep and aging associated with the expected storage
life.
[0033] Closures 8 were then removed and the removal torque values
were recorded as shown in Table 1. These results are summarized in
Table 1 below. TABLE-US-00001 TABLE 1 Test Torque Period 3-lbs
4-lbs 5-lbs 6-lbs 7-lbs 8-lbs 9-lbs 10-lbs 24-Hours 7.7 4.9 5.1 6.0
7.1 7.0 6.7 9.3 24-Hours 5.7 6.5 5.1 7.2 8.3 7.3 9.4 7.7 24-Hours
4.3 4.1 5.2 6.2 6.7 7.2 7.7 6.6 24-Hours 5.3 4.5 5.6 6.8 7.8 7.2
6.2 7.8 24-Hours 6.1 6.5 4.6 5.5 7.7 7.4 6.6 9.5 Average = 5.82
5.30 5.12 6.34 7.52 7.22 7.32 8.18 144-Hours 4.7 6.0 7.0 6.4 6.7
6.6 6.1 6.7 144-Hours 6.5 5.6 6.4 6.6 5.5 7.6 4.4 8.5 144-Hours 6.5
6.5 5.8 6.5 6.2 5.6 7.0 7.8 144-Hours 7.6 8.4 4.7 5.9 6.2 5.5 7.0
7.8 144-Hours 5.0 5.7 6.0 5.5 6.0 6.5 8.2 6.4 Average = 6.06 6.44
5.98 6.18 6.12 6.36 6.40 7.96 1-Week 5.8 6.3 6.1 6.0 5.5 5.8 7.0
8.7 1-Week 6.2 6.0 6.6 7.8 6.6 6.9 9.5 6.6 1-Week 6.1 7.8 8.5 6.3
7.2 7.6 7.3 7.5 1-Week 6.5 6.5 6.2 6.3 9.5 6.3 7.7 9.0 1-Week 7.0
9.0 5.6 7.2 6.9 8.2 8.5 6.4 Average = 6.32 7.12 6.60 6.72 7.14 6.96
8.00 7.64
[0034] As can be seen from Table 1, at the conclusion of the tests,
it was found that the present invention provides torque retention
of substantially greater than fifty percent. The removal torque
does not linearly correspond with the set torque. For example, a
set torque of between 8 and 10 inch pounds resulted in torque
retentions in excess of seventy-five percent while a set torque of
between 3 and 7 inch pounds resulted in removal torques well in
excess of the applied set torque, or, in other words, exhibiting
torque retention of greater than one-hundred percent.
[0035] For the sake of brevity, conventional mechanical and
industrial design techniques used in developing various devices
(and the various components thereof) are not described in detail
herein. Accordingly, devices disclosed herein may be readily
modified to create equivalent embodiments through application of
general mechanical, industrial and/or manufacturing principles. The
particular implementations shown and described herein are examples
of the invention and are not intended to otherwise limit the scope
of the invention in any way. In this context, the corresponding
structures, materials, acts and equivalents of all elements
described herein, are intended to include any structure, material
or acts for performing the functions described herein and include
those now known or hereafter devised.
* * * * *