U.S. patent application number 13/718361 was filed with the patent office on 2014-03-06 for venting mechanisms for containers.
This patent application is currently assigned to CORNERSTONE RESEARCH GROUP, INC.. The applicant listed for this patent is CORNERSTONE RESEARCH GROUP, INC.. Invention is credited to Joel J. Everhart, Matthew C. Everhart, Michael J. Fisher, David E. Havens, Brandon C. Kirby, Eric W. Traxler, Jamie B. Vanderhorst.
Application Number | 20140061515 13/718361 |
Document ID | / |
Family ID | 39864288 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140061515 |
Kind Code |
A1 |
Traxler; Eric W. ; et
al. |
March 6, 2014 |
VENTING MECHANISMS FOR CONTAINERS
Abstract
The disclosed device primarily consists of a band, ring, or
other piece of shape memory polymer (SMP) or SMP composite in
various embodiments that allows or disallows containment. When the
SMP reaches its transition temperature (Tg) the SMP provides the
means for releasing containment of the pressurized material so as
to prevent ignition or explosion of hazardous material. At normal
operating temperatures, the SMP is in a deformed shape maintaining
an environmental seal to protect the contents of the container.
When environmental conditions cause the SMP or SMP composite to
exceed its Tg, specified by the operating requirements, the SMP
returns to its memory shape in a controlled geometry, rather than
simply melting. The return of the SMP to its memory shape causes
the venting of the container in different manners depending on
which embodiment is utilized.
Inventors: |
Traxler; Eric W.;
(Beavercreek, OH) ; Vanderhorst; Jamie B.; (West
Chester, OH) ; Havens; David E.; (Bellbrook, OH)
; Kirby; Brandon C.; (Beavercreek, OH) ; Fisher;
Michael J.; (Springboro, OH) ; Everhart; Joel J.;
(Beavercreek, OH) ; Everhart; Matthew C.;
(Fairborn, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNERSTONE RESEARCH GROUP, INC.; |
|
|
US |
|
|
Assignee: |
CORNERSTONE RESEARCH GROUP,
INC.
Dayton
OH
|
Family ID: |
39864288 |
Appl. No.: |
13/718361 |
Filed: |
December 18, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12526360 |
Aug 7, 2009 |
8356727 |
|
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PCT/US08/56031 |
Mar 6, 2008 |
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13718361 |
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60893499 |
Mar 7, 2007 |
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Current U.S.
Class: |
251/11 |
Current CPC
Class: |
F42B 39/20 20130101;
F42D 5/045 20130101; F42B 39/14 20130101; F42D 5/00 20130101 |
Class at
Publication: |
251/11 |
International
Class: |
F42B 39/14 20060101
F42B039/14; F42D 5/00 20060101 F42D005/00 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with U.S. Government support under
Contract No. W9113M-06-C-0078 and Contract No. HQ0006-07-C-7609
awarded by the U.S. Army Space & Missile Defense Command to
Cornerstone Research Group Inc. The U.S. Government has certain
rights in the invention.
Claims
1. A venting device comprising: a container comprising an opening;
an inner containment layer laterally disposed around the container
and comprising at least outer lip disposed at an end proximate the
container opening; an outer containment layer laterally disposed on
the inner containment layer but not disposed over the at least one
outer lip; a metal clamp configured to cover the opening and
comprising at least one end flange, the end flange comprising an
inner surface configured to contact an outer surface of the outer
containment layer, and a recessed section configured to engage the
outer lip of the inner containment layer; and an expandable shape
memory band wrapped around the end flange of the metal clamp, the
end flange being moveable with the expandable shape memory band,
wherein the expandable shape memory band comprises a shape memory
polymer or shape memory polymer composite that diametrically
expands in size at a predetermined critical temperature, wherein
the expansion of the expandable shape memory band upon reaching the
predetermined critical temperature outwardly moves the end flange
of the metal clamp, which separates the inner surface of the end
flange from the outer surface of the outer containment layer and
decouples the recessed section of the end flange from the outer lip
of the inner containment layer, thereby detaching the metal clamp
to vent the container.
2. The venting device of claim 1 wherein said shape memory polymer
or said shape memory polymer composite used in the expandable shape
memory band is selected from the group consisting essentially of
styrene based, epoxy based, cyanate ester based, polyurethane
based, maleimide based, or siloxane based shape memory polymer.
3. The venting device of claim 2 wherein said shape memory polymer
is a thermoset resin.
4. The venting device of claim 1 wherein said shape memory polymer
composite is formed from at least one layer of fibrous material in
combination with said shape memory polymer.
5. The venting device of claim 4 wherein said fibrous material is
embedded in said shape memory polymer.
6. The venting device of claim 4 wherein said fibrous material is
impregnated with said shape memory polymer.
7. The venting device of claim 4 wherein said fibrous material is
carbon nano-fibers, carbon fiber, spandex, chopped fiber, random
fiber mat, fabric of any material, continuous fiber, fiberglass, or
other type of textile fabric.
8. The venting device of claim 4 wherein said fibrous material is
in the form of a flat weave, two dimensional weave, or three
dimensional weave pattern.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is filed as a continuation of U.S.
application Ser. No. 12/526,360 filed on Aug. 7, 2009, which is a
national stage entry of PCT/US2008/56031 filed on Mar. 6, 2008,
which claims priority to U.S. Provisional Application Ser. No.
60/893,499 filed on Mar. 7, 2007.
TECHNICAL FIELD OF THE INVENTION
[0003] Under normal operating conditions, most containment devices
are both effective and relatively safe. These containment devices
provide an essential function in storing items and preventing the
unwanted spread of the various materials stored in them. These
containment devices are especially useful in preventing
environmental contamination of explosive or hazardous material. In
particular these containment devices are used in modern munitions.
In munitions, containment devices provide an essential military
capability and are unlikely to explode or burn spontaneously,
despite the fact that they are composed primarily of hazardous
material.
[0004] However, when munitions, such as solid rocket motors (SRMs),
are placed under unwanted stimuli, like heat and mechanical shock,
dangerous results can occur. SRMs may be triggered to ignition by
fire or by impact with bullets or fragments. As a result there is a
push to develop a class of SRMs that are insensitive munitions
(IM). An IM is one that will not detonate under any conditions
other than its intended mission. If an IM is struck by fragments
from an explosion or hit by a bullet, it will not detonate.
Additionally, IMs will not detonate if it is in close proximity to
a target that is hit. In extreme temperatures, the SRMs will only
burn (without detonation or explosion). This increased safety
allows greater numbers of missiles to be packaged, handled, stored,
and transported in smaller containers. These requirements demand
higher levels of safety performance: the system will be safer to
operate in any environment while maintaining its lethal
performance. It also allows for cost saving opportunities for the
government because more SRM will be able to be stored in a smaller
area, safely.
[0005] As a result of a number of well publicized accidents in
recent years involving premature and inadvertent activation of
munitions with resultant loss of life among service personnel as
well as other damage, there has been an increased emphasis on
creating IM which are safer to store, handle and use. Specifically,
in October 2006, in Baghdad, Iraq, a fire erupted in a U.S. ammo
dump, setting off a series of blasts due to the detonation of the
ammunition being stored in the facility. This is a prime example of
the need for current and future munitions to be IM compliant.
[0006] As new SRM systems are developed, they will be required to
meet a growing set of specifications for IM compliance. The current
technologies that are used to minimize the effects of unintentional
stimuli on SRMs are insufficient and new IM technologies must be
developed to allow IM compliance in future systems. One of the
first lines of defense in protection of the SRM is the containers
that these munitions are stored in during inactive periods. These
containers can protect the SRM from bullet fragments and can serve
as a containment system in slow and fast cook-off situations.
However, during slow and fast cook-offs of the SRM, the container
must be capable of sufficiently venting the generated gasses.
Current containers are sealed to protect the ammunition from the
outside environment; however, to reach IM compliance, containers
must be capable of venting when a set of predetermined conditions
are met. SRM cases can also be vented to allow for IM-compliant
systems. Additionally, the disclosed device can be used to prevent
over-pressurization of volatile liquid and other hazardous
containers to prevent similar explosions and loss of life.
BACKGROUND ART
[0007] Based on recent incidents with the unintentional detonation
of munitions, there has been increased research into the area of
creating better, more efficient IM. Most of these newer systems
rely on passively activated designs to vent their explosive
material to the environment before environmental conditions can
activate the propellants or munitions.
[0008] Some systems that have been developed use explosive products
to create holes in the munitions or propellant containers to vent
them. The explosive products or the impact of a bullet, fragment,
or shaped charge jet from the systems may result in a temperature
sufficient to ignite the propellants or munitions. Additionally the
explosive products or the impact of a bullet, fragment, or shaped
charge jet may inadvertently initiate the venting system thereby
rendering the munitions ineffective.
[0009] In U.S. Pat. No. 6,360,526 issued to Kunstmann on Mar. 26,
2002 such an passive system is described. A rocket motor having a
desensitizing mechanism for preventing explosion or violent
reaction during slow cook off is disclosed. In Kunstmann the rocket
motor includes a case contained rocket propellant with a
desensitizing assembly attached forward of the propellant charge.
The desensitizing assembly is formed with an enclosure containing a
desensitizing fluid, and connected to the interior of the rocket
motor by a tube which is sealed by a heat sensitive plug. The heat
sensitive plug melts at a temperature below the slow cook off
temperature of the rocket propellant and the melting of the plug
allows the desensitizing fluid to be injected into the interior of
the casing and onto the propellant charges, thereby, desensitizing
the propellant charge.
[0010] In U.S. Pat. No. 6,338,242 issued to Kim et. al on Jan. 15,
2002 a similar passive system is disclosed. In Kim, an ordnance
venting system has an ordnance device having a casing with a vent
opening, a dome plug fitted into the formed vent opening and an
adapter fitted over the dome plug on the outside of the casing. The
adapter connects sufficiently to the casing to retain the dome plug
against the formed vent opening for given pressures. The adapter
melts at high temperatures and releases the dome plug to reduce the
danger of explosion from heat induced over pressurization.
[0011] One system utilizing a charge is described in U.S. patent
application Ser. No. 11/261,184 filed Oct. 28, 2005 by Skinner.
Skinner discloses a device for venting a container housing and
energetic material including an installation portion, a charge
holder disposed in the insulating portion, and an explosive cutting
charge disposed in the cardholder. The device further includes a
thermally activated initiation device, and a transfer line coupling
the thermally activated initiation device and the explosive cutting
charge. When exposed to a temperature at or above a predetermined
temperature heat produced deflagration of the thermally activated
initiation device initiates deflagration in the transfer line which
in turn detonates explosive cutting charges. Upon detonation these
explosive cutting charges perforate the container to relieve
pressure or avoid buildup of pressure within the case.
[0012] Fuses, charges or plugs do allow venting however they are
not as durable and they do not allow as easily for normal operation
as the presently disclosed device. They also do not offer a lot of
venting; therefore many plugs, fuses or charges may be
required.
[0013] For the purposes of this application the term Shape Memory
Polymers as described below is equivalent to Dynamic Modulus
Resins.
[0014] Shape memory materials were first developed about 20 years
ago and have been the subject of commercial development in the last
10 years. Shape memory materials derive their name from their
inherent ability to return to their original "memorized" shape
after undergoing a shape deformation. There are principally two
types of shape memory materials, shape memory alloys (SMAs) and
shape memory polymers (SMPs).
[0015] SMAs and SMPs that have been preformed can be more easily
deformed to a desired shape above their glass transition
temperature (Tg). The SMA and SMP must remain below, or be quenched
to below, the Tg while maintained in the desired shape to "lock" in
the deformation. Once the deformation is locked in, the SMA,
because of its crystalline network, and the SMP, because of its
polymer network, cannot return to a relaxed state due to thermal
barriers. The SMA and SMP will hold its deformed shape indefinitely
until it is heated above its Tg, whereupon the SMA and SMP stored
mechanical strain is released and the SMA and SMP returns to its
preformed state.
[0016] There are principally two types of plastics, thermoset
resins and thermoplastic resins, each with its own set of unique
characteristics. Thermoset resins, for example polyesters, are
liquids that react with a catalyst to form a solid, and cannot be
returned to their liquid state, and therefore, cannot be reshaped
without destroying the polymer networks. Thermoplastics resins, for
example PVC, are also liquids that become solids. But unlike
thermoset resins, thermoplastics are softened by application of
heat or other catalysts. Thermoplastics can be heated, reshaped,
heated, and reshaped over and over.
[0017] SMPs used in the presently disclosed device are unique
thermosetting polymers that, unlike traditional thermosetting
polymers, can be reshaped and formed to a great extent because of
their shape memory nature and will not return to a liquid upon
application of heat. Thus by creating a shape memory polymer that
is also a thermosetting polymer, designers can utilize the
beneficial properties of both thermosetting and thermoplastic
resins while eliminating or reducing the unwanted properties. Such
polymers are described in U.S. Pat. No. 6,759,481 issued to Tong,
on Jul. 6, 2004 which is incorporated herein by reference. Other
thermoset resins are seen in PCT Application No. PCT/US2006/062179,
filed by Tong, et al on Dec. 15, 2006; and PCT Application No.
PCT/US2005/015685 filed by Tong et al, on May 5, 2005 of which both
applications are incorporated herein by reference.
[0018] There are three types of SMP's: 1) A partially cured resin,
2) thermoplastics, and 3) fully cured thermoset systems. There are
limitations and drawbacks to the first two types of SMP. Partially
cured resins continue to cure during operation and change
properties with every cycle. Thermoplastic SMP "creeps," which mean
it gradually "forgets" its memory shape over time. A thorough
understanding of the chemical mechanisms involved will allow those
of skill in the art to tailor the formulations of SMP to meet
specific needs, although generally fully cured thermoset resin
systems are preferred in manufacturing.
[0019] While SMA and SMP appear to operate similarly on the macro
scale, at the molecular scale it is apparent that the method of
operation of each is very different. The difference between SMA and
SMP at the molecular level is in the linkages between molecules.
SMA essentially has fixed length linkages that exist at alternating
angles establishing in a zigzag patterned molecular structure.
Reshaping is achieved by straightening the angled connections from
alternating angles to straight forming a cubic like structure. This
method of reshaping SMA material enables bending while limiting any
local strains within the SMA materials to less than 8% strain, as
the maximum shape memory strain for SMA is 8%. This 8% strain
allows for the expansion or contraction of the SMA by only 8%, a
strain that is not useful for most industrial applications.
Recovery to memory shape is achieved by heating the material above
a certain temperature at which point the molecules return to their
original zigzag molecular configuration with significant force
thereby reestablishing the memory shape. The molecular change in
SMA is considered a metallic phase change from Austensite to
Martensite which is defined by the two different molecular
structures.
[0020] SMP has connections between molecules with some slack. When
heated these links between connections are easily contorted,
stretched and reoriented due to their elastic nature as the SMP
behaves like an elastic material when heated, when cooled, the
shape is fixed to how it was being held. In the cooled state the
material behaves as a typical rigid polymer that was manufactured
in that shape. Once heated the material again returns to the
elastic state and can be reformed or return to the memory shape
with very low force. Unlike SMA which possesses two different
molecular structures, SMP is either a soft elastomer when heated or
a rigid polymer when cool. Both SMA and SMP can be formulated to
adjust the activation temperature for various applications.
Critical to the success of the currently claimed device is
thermoset SMP which provides an order of magnitude higher stiffness
than previous state-of-the-art thermoplastic SMPs. This added
stiffness coupled with high strain capability enables the
development and use of a highly useful composite tooling
technology.
[0021] Shape memory alloys have been used to attempt to solve the
IM issue as disclosed in U.S. Pat. No. 6,321,656 issued to Johnson
on Nov. 27, 2001. In Johnson a thermally responsive material, such
as Nitinol, an SMA, is used to create a latching mechanism which,
upon exposure to temperatures in excess of the Tg of the Nitinol,
the latching mechanism changes shape so as to mechanically unlatch
the rocket casing section holding the propellant. However, as noted
above the shape change is minimal requiring very large mechanisms
to ensure unlatching or thinner SMA as the latching mechanism which
may fail due to a lack of structural strength. Additionally Johnson
does not describe or disclose the use of an SMP or SMP composite
for use in a venting system for IM.
[0022] The term "composite" is commonly used in industry to
identify components produced by impregnating a fibrous material
with a thermoplastic or thermosetting resin to form laminates or
layers. Generally, polymers and polymer composites have the
advantages of weight saving, high specific mechanical properties,
and good corrosion resistance, which make them indispensable
materials in all areas of manufacturing. Nevertheless,
manufacturing costs are sometimes detrimental, since they can
represent a considerable part of the total costs and are made even
more costly by the inability to quickly and easily repair these
materials without requiring a complete, and expensive, total
replacement. Furthermore, the production of complex shaped parts is
still a challenge for the composites industry. Because SMPs are
resins, they can be used to make composites, which are referred to
in this application as SMP composites.
[0023] Unlike SMAs, SMPs exhibit a radical change from a normal
rigid polymer to a flexible elastic and back on command. SMA would
be more difficult to use for thermally activated venting systems
for rocket motors because SMAs do not have the ease in changing the
activation temperature as do SMP's for different propellants. SMAs
would also have issues with galvanic reactions with other metals
which would lead to long term instability. The current supply chain
for SMAs is currently not consistent as well. SMP materials offer
the stability and availability of a plastic and are more inert than
SMAs. Additionally, when made into a composite SMPs offer similar
if not identical mechanical properties to that of traditional
metals and SMAs in particular. Throughout this disclosure SMP and
SMP composites are used interchangeably as each can be replaced by
the other depending on the specific design requirements to be
met.
[0024] Therefore there is a need for a low cost, high strain system
to allow for the easy venting of IM so as to prevent inadvertent or
slow cook off of stored munitions.
DISCLOSURE OF THE INVENTION
[0025] The presently disclosed application provides a method and
means for ensuring that containers of all types and sizes are
vented or purged to atmospheric or environmental conditions upon
the exterior of the container reaching a critical temperature. The
preferred embodiment of this application is in allowing pressurized
fuel containers to vent to the atmosphere before the fuel reaches
temperatures which would cause it to explode. More preferably the
presently disclosed device is used in munitions stored for long
periods of time.
[0026] The most preferred embodiment of the disclosed device
primarily consists of a band, ring, or other piece of shape memory
polymer (SMP) or SMP composite in various embodiments that allow or
disallow containment. When the SMP reaches its transition
temperature (Tg) the SMP provides the means for releasing
containment of the pressurized material so as to prevent ignition
or explosion of hazardous material. At normal operating
temperatures, the SMP is in a deformed shape maintaining an
environmental seal to protect the contents of the container. When
environmental conditions cause the SMP or SMP composite to exceed
its Tg, specified by the operating requirements, the SMP returns to
its memory shape in a controlled geometry, rather than simply
melting. The return of the SMP to its memory shape causes the
venting of the container in different manners depending on which
embodiment is utilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1A shows a perspective view of one embodiment of an IM
compliant mechanism.
[0028] FIG. 1B shows the shape memory polymer ring and metal
latches used in the first embodiment of the IM compliant
mechanism.
[0029] FIG. 2A shows a perspective view of the first embodiment
with the SMP ring partially retracted from the IM.
[0030] FIG. 2B shows the fully retracted SMP ring which has caused
the two parts to the IM compliant mechanism to become
separated.
[0031] FIG. 3A shows a perspective view of a second embodiment of
the venting mechanism.
[0032] FIG. 3B shows a close up of how the latches for the second
embodiment of the venting system can be used to latch onto a
container.
[0033] FIG. 4A shows a perspective view of the second embodiment of
the venting system sealing a container.
[0034] FIG. 4B shows a close up of how the latches for the second
embodiment of the venting system actually latch onto the side of
the container.
[0035] FIG. 5 shows a perspective view of another mechanism for
using shape memory polymer and a clamp to seal a container.
[0036] FIG. 6 shows a perspective view of how the third embodiment
will vent a container by allowing the clamp to come undone.
[0037] FIG. 7 shows a perspective view of a fourth embodiment of
how shape memory polymer and a clamp can be used to seal a
container.
[0038] FIG. 8 shows a perspective view of how the shape memory
polymer can be used to unseal the clamp in the fourth
embodiment.
[0039] FIG. 9 shows a side view of a fifth embodiment of the use of
shape memory polymer and a metal clamp to seal a container.
[0040] FIG. 10 shows a side view of how the shape memory polymer in
the fifth embodiment will allow the venting of the container.
[0041] FIG. 11 shows a side view of the preferred embodiment of the
use of shape memory polymer to seal a container.
[0042] FIG. 12 shows a side view of a close up of the preferred
embodiment.
[0043] FIG. 13 is a graph showing the relationship of the elastic
modulus of shape memory polymer versus the temperature of the shape
memory polymer.
MODES FOR CARRYING OUT THE INVENTION
[0044] The disclosed device primarily consists of a band, ring, or
other piece of shape memory polymer (SMP) or SMP composite in
various embodiments that allows or disallows containment. When the
SMP reaches its transition temperature (Tg) the SMP provides the
means for releasing containment, typically through the release of
an air-tight seal, of the pressurized material so as to prevent
ignition or explosion of hazardous material. At normal operating
temperatures, the SMP is in a deformed shape maintaining an
environmental seal to protect the contents of the container. When
environmental conditions cause the SMP or SMP composite to exceed
its Tg, specified by the operating requirements, the SMP returns to
its memory shape in a controlled geometry, rather than simply
melting. The return of the SMP to its memory shape causes the
venting of the container in different manners depending on which
embodiment is utilized.
[0045] SMP combined with traditional composite materials offer high
strength to weight ratios, similar to other composites. However,
SMP composites offer a unique ability to release stored mechanical
energy at a predetermined temperature range. This unique set of
mechanical properties makes SMPs ideal for implementing
IM-compliant lightweight hybrid-composite ammunition containers.
The disclosed device and designs show various embodiments of an
optimized pressure venting mechanism that utilizes SMP's properties
for actuation.
[0046] The design of the SMP part to be used in the disclosed
mechanism will be apparent to those of skill in the art of creating
such parts and will vary greatly from container to container
depending on which embodiment of the disclosed device is utilized.
However, the formulations and chemical makeup of the SMP to be used
will vary greatly depending on such factors as normal environmental
conditions the mechanism will be exposed to, costs, desired
activation temperature or other activation conditions, and the
strength of the material needed. As noted above, SMPs can be
created to meet the operating specifications needed for various
situations. The Tg of SMPs can be tailored such that the Tg of the
SMP occurs between 0.degree. Celsius and 280.degree. Celsius. The
SMP to be used can be selected from the group consisting of styrene
based, epoxy based, cyanate ester based, polyurethane based,
siloxane based, or other chemicals which can be made into an SMP.
Additionally, while thermal activation of the SMP is the preferred
method, there are other methods besides thermal energy to
transition the SMP between its hard rigid state to a soft pliable
and elastic state and back. Electromagnetic radiation, UV light,
water, and magnetism can be used to transition the SMP between its
hard rigid state to a soft pliable and elastic state and back.
[0047] FIG. 13 is a graph showing the unique properties of SMP. The
graph in FIG. 13 is a plot of the elastic modulus of a typical SMP
versus the temperature of that SMP. In the first band, the Plastic
or Rigid State, the SMP has all the strength of a traditional
plastic. In the third band, the Elastic State, the SMP behaves like
a heated thermoset resin which is pliable and soft. In the fourth
state, the Thermal Degradation State, the SMP decomposes and loses
its structural integrity. However, the temperatures of the Thermal
Degradation State are typically well above 500 20 C., well above
the temperatures needed for use in industry. The second band,
Transition Band, is the area where the SMP transitions from a hard,
rigid state to a soft, pliable state. The Tg is exactly in the
middle of this band. The size of the band can be tailored such that
the temperature range of the band is 5-10 degrees Celsius.
[0048] SMP composites can use a variety of fibrous material such as
carbon nano-fibers, carbon fiber, spandex, chopped fiber, random
fiber mat, fabric of any material, continuous fiber, fiberglass, or
other type of textile fabric compatible with the SMP resin.
Additionally, the strength of the SMP composite can be influenced
by the weave of the fabric such as a flat weave, two dimensional
weave, or three dimensional weave patterns. The SMP composites may
comprise a composite material formed from at least one layer of
fibrous material in combination with a shape memory polymer. In one
form, the fibrous material may be embedded within the shape memory
polymer or, the fibrous material can be impregnated with the shape
memory polymer.
[0049] The following examples provide formulations of SMP which can
be used in the currently disclosed device. However, these examples
should not be interpreted as limiting the scope of this application
to only those formulations provided.
EXAMPLE 1
[0050] A polymeric reaction mixture was formulated by mixing vinyl
neodecanoate (7%), divinyl benzene (1%), and styrene (90%) in
random order to yield a clear solution. Benzoyl peroxide (2%) was
then added to the resulting solution (all composition % are by
weight). The resulting solution was kept cold in a refrigerator
before use.
EXAMPLE 2
[0051] A polymeric reaction mixture was formulated by mixing vinyl
neodecanoate (7%), divinyl benzene (1%), and styrene (60%) in
random order to form a colorless solution. Polystyrene granules
(30%) were then added to the resulting solution. The resulting
mixture was then allowed to sit at room temperature with occasional
stirring until all the polystyrene granules were dissolved to give
a clear, viscous solution. Benzoyl peroxide (2%) was then added to
the resulting solution (all composition % are by weight). The
resulting mixture was ultrasonicated at room temperature for 15
minutes to yield a clear solution. The resulting solution was kept
cold in a refrigerator before use.
EXAMPLE 3
[0052] As an example, 1.08 g aniline (amine reagent) was mixed with
0.066 g of methylenedianline (crosslinking diamine). The resulting
solution was mixed with 4.17 g of bisphenol A diglycidyl ether to
form an homogeneous solution.
EXAMPLE 4
[0053] For a resin system with a Tg of 1030C, Bisphenol A
diglycidyl ether at 78.94% weight is mixed with aniline at 19.88%
weight and DETDA (major isomers: 3,5-diethyltoluene-2,4-diamine and
3,5-diethyltoluene-2,6-diamine) at 1.19% weight.
EXAMPLE 5
[0054] For a resin system with a Tg of 600 C, diglycidyl ether of
Bisphenol A at 45.32% weight and 1,4-butanediol diglycidyl ether at
31.38% weight are mixed with aniline at 21.99%-weight and DETDA
(major isomers: 3,5-diethyltoluene-2,4-diamine and
3,5-diethyltoluene-2,6-diamine) at 1.31% weight. All components are
miscible liquids and are easily combined through mechanical
mixing.
[0055] To prepare the SMP for use in an IM device, the reaction
mixtures formulated above are injected into a mold fabricated into
the shape of the SMP ring to be used in the IM device. The SMP and
mold is then heated in an oven maintained at atmospheric pressure
and a temperature of 75.degree. C. fa 24 hours to cure the SMP.
After the SMP is cured it is removed from the oven and immediately
transferred to a warm water bath. The temperature of water used was
about 60.degree. C. The SMP is demolded under the warm water by
applying a slight prying force at the edges of the mold. The SMP
ring is then allowed to dry and cool down to room temperature,
resulting in a ring of SMP to be used in the IM device. Of the
above examples, Example 3 is particularly preferred for use in the
disclosed device.
[0056] In addition to using pure resin as the mechanism for the
venting of a container, the SMP resin can be combined with fibers
to create a composite. This is accomplished by curing the resin, in
the mold, with the fibers within the resin matrix. Alternatively, a
filament winding system or other composite manufacturing process
can be used
[0057] Any type of SMP with a sufficiently tailorable and narrow
transition band could be used based on the requirements of the
actual Tg needed. Some SMPs which can be used are styrene based,
epoxy based, cyanate ester based, polyurethane based, or siloxane
based SMPs. Of the above, epoxy based SMPs are particularly
preferred for their ease of use, manufacture, and low environmental
danger posed.
[0058] FIG. 1A shows one embodiment that is a simplified mechanism
that is a failsafe SMP-actuated pressure venting system that
provides IM compliance. The SMP or SMP composite band, 2, depicted
in FIG. 1A, vents pressure when a specific threshold temperature is
reached and the end section, 4, is able to detach from the main
body, 6. The mechanism, as shown in FIG. 1B, primarily consists of
a ring or band of SMP or SMP composite band, 2, attached to metal
latches, 8, that allows or disallow containment.
[0059] As seen in FIG. 2A, when the SMP or SMP composite band, 10,
reaches its transition temperature (Tg) the SMP returns to its
memory shape which is smaller than its deformed shape and this
provides the means for releasing containment of the pressurized
material so as to prevent ignition or explosion of hazardous
material by retracting the metal latches, 8. At normal operating
temperatures, the tension of the SMP or SMP composite band keeps
the metal latches of the mechanism in contact with the lip, 14, of
the body of the main body 6, maintaining an environmental seal to
protect the contents. In case of fire, or other condition, wherein
the SMP exceeds its Tg specified by the operating requirements, the
band actuates in a controlled geometry, rather than simply melting.
As shown in FIG. 2B, the return of the SMP or SMP composite band,
12, to its memory shape causes the metal latches, 8, to retract
from the lip, 14, of the main body, 6, and unseal the end section,
4, from the body of the container, thereby venting the container.
The main body, 6, has a hole, 20, through which the end section, 4,
has a second lip, 16, wherein the second lip, 16, has a diameter
slightly less than the diameter of the hole, 20. The ring shown in
FIG. 1B is used to ensure the seal between the end section, 4, and
main body, 6.
[0060] Metal is the primary structural element in this embodiment,
with the SMP or SMP composites used to keep the metal latches, 8,
in contact with the main body, 6, throughout normal operation. In
this embodiment, if the SMP is damaged, the pressure is released.
In other words, the mechanism is not reliant on the SMP to apply a
force for activation, but directly the converse.
[0061] One of the major benefits in this embodiment is the fact
that the SMP does not bear a lot of load. The three metal latches,
8, fits into a groove between the lip, 14, and second lip, 16, that
holds the end section, 4, in place with the enlarged SMP or SMP
composite band, 2. Another advantage of this embodiment using SMP
is the ability to tailor the activation temperature to enable the
use of the mechanism with a variety of propellants. A rocket motor
manufacturer can specify a propellant, and a manufacturer can
determine an SMP formulation to meet the transition temperature
requirements.
[0062] FIGS. 3A and 3B show a second embodiment. In FIG. 3A a piece
of SMP or SMP composite, 44, is constructed in a geometric shape
consistent with that of the outer part, 54, to hold in place such
that the SMP or SMP composite, 44, can fit within the outer part,
54. The SMP or SMP composite, 44, has additional SMP or SMP
composite tabs, 46, which are initially smaller than similarly
shaped holes, 52, in the outer part 54. In FIG. 3B, it can be seen
that the SMP or SMP composite tabs, 46, have a distance between one
side point, 42, and a second side point, 40, wherein this distance
is smaller than the distance between a third side point, 48, and a
fourth side point, 50, of a hole, 52, such that the SMP or SMP
composite tabs, 46, can be inserted into hole, 52.
[0063] The SMP or SMP composite, 44, once inside the outer part,
54, can be expanded either by activating and deforming the SMP or
SMP composite or by activating the SMP or SMP composite and
allowing it to return to its memory shape which shape shown in FIG.
4A, 56, wherein the tabs, 58, have filled in the holes of the outer
part, 54. Once the SMP or SMP composite is cooled, FIG. 4B shows
how the distance between the first end point, 64, and second end
point, 66, of the tab, 58, is now larger than the distance between
the third end point, 62, and fourth end point, 60, of the hole such
that the SMP or SMP composite prevents the outer part, 54, from
moving.
[0064] A third embodiment is shown in FIGS. 5 and 6. In FIG. 5 a
clamp, 70, is held together by a piece of SMP or SMP composite, 72.
The clamp, 70, has a first end piece, 78, and a second end piece,
74, which are held closely together at a joint, 76, by the SMP or
SMP composite, 72. As shown in FIG. 6, this is accomplished by the
SMP or SMP composite, 72, as shown in FIG. 5, having a larger
diameter than the hole, 80, as shown in FIG. 6, through which the
SMP or SMP composite passes. When the SMP or SMP composite is
reduced in size, 82, as shown in FIG. 6, the first end piece, 78,
and second end piece, 74, are no longer held together and come
apart, releasing the contents of the container.
[0065] A fourth embodiment is shown in FIGS. 7 and 8. In this
embodiment a SMP or SMP composite plate, 90, as shown in FIG. 7, is
formed over the end pieces, 92, of a clamp, 94, creating a lip, 86,
of SMP or SMP composite against a second lip, 84, of the end
pieces, 92, and a side, 88, of SMP or SMP composite on both end
pieces, 92, so as to hold the end pieces, 92, together. As shown in
FIG. 8, when the SMP or SMP composite plate, 96, returns to its
memory shape the end pieces, 92, are free to separate creating the
gap, 98, between them and forcing the SMP or SMP composite plate,
96 to create a gap, 91, between the clamp, 94, and the SMP or SMP
composite plate, 96. This loosening of the clamp and gaps allow the
pressure within the container to vent.
[0066] Another embodiment is shown in FIGS. 9 and 10. In FIG. 9, a
band of SMP or SMP composite with an upper portion, 112, and a
lower portion, 113, is wrapped around a metal clamp, 120, which
holds an outer containment layer, 100, and an inner containment
layer, 102, around a central core, 104. The upper portion, 112, has
an inner surface, 108, which is pressed against the outer surface,
106, of the metal clamp, 120. A second inner surface, 114, of the
metal clamp, 120, is pressed against the outer containment layer,
100, and the inner containment layer, 102, along a third inner
surface, 116, and the outer surface, 118, of the inner containment
layer, 102. The lower portion shown in FIG. 9, 113, works identical
to the upper portion with an inner surface, 109, which is pressed
against the outer surface, 107, of the metal clamp, 120. A second
inner surface, 115, of the metal clamp, 120, is pressed against the
outer containment layer, 100, and the inner containment layer, 102,
along a third inner surface, 117, and the outer surface, 119, of
the inner containment layer, 102. At normal operating temperatures,
the tension of the SMP or SMP composite band, 112 and 113, keeps
the surfaces, 114 and 115, and edges, 116 and 117, of the metal
clamp, 120, in contact with the outer surface of the outer
containment layer, 100, and the lips, 118 and 119, of the inner
containment layer, 102, maintaining an environmental seal to
protect the contents.
[0067] When the SMP's activation temperature is exceeded, the band,
112 and 113, actuates, returning to its expanded memory shape, as
shown in FIG. 10. The SMP or SMP composite band will expand
creating a larger portion of SMP or SMP composite, 124 and 125, all
around the metal clamp, 120. The inner surfaces, 108 and 109, of
the SMP or SMP composite band, 112 and 113, will retract from the
outer surfaces, 122 and 123, of the metal clamp, 120. As the SMP or
SMP composite bands retract, the metal clamp, 120, will be able to
return to a normal, non-stressed state. In returning to this
non-stressed state, the inner surfaces, 114 and 115, of the metal
clamp, 120, will retract from the inner and outer containment
layers, 100 and 102, so as to release the contents of the central
core, 104. The metal clamp, 120, and SMP or SMP composite band, 112
and 113, must be designed so that after the SMP or SMP composite
band has fully expanded, the metal clamp has sufficient room to
expand so that the upper corner, 130, and lower corner, 131, of the
metal clamp, have sufficient clearance room over the outer upper
corner, 128, and outer lower corner, 129, of the inner containment
layer, 102, so that the metal clamp will fall away from the central
core, 104, to allow the inner core to vent. As before, the metal
clamp is the primary structural element in the system, with the SMP
composite band solely used to keep the metal latches in contact
with the body of the container throughout normal operation.
[0068] In the final, preferred embodiment, a system of metal
springs encased in SMP or SMP composite is used as shown in FIGS.
11 and 12. In FIG. 11. the existing aft closure design of IM
currently used in the field is used and merely replaces the bolts
used to attach the aft closure, 150, to the rocket motor case, 154,
with retracting bolts, 143, 146, 147 and 149. The retracting bolts
are attached to SMP or SMP composite encased springs, 144 and 145,
which hold the retracting bolts within the holes, 152, in the
holding ring, 153, located within the aft closure, 150. The rocket,
142, is attached to the aft closure, 150, by a connecting piece,
140.
[0069] FIG. 12 shows a close up of the locking both mechanism. The
SMP or SMP Composite, 162, encases a high tension spring, 160. The
SMP or SMP composite does not act on the upper retracting bolt,
166, or the lower retracting bolt, 164; the purpose of the SMP or
SMP composite is to prevent the high tension spring, 160, from
moving while the SMP or SMP composite is in its hard, rigid state.
The inner holding ring, 151, aft closure, 150, and rocket motor
case, 154, are merely shown for reference. The retracting bolts,
164 and 166, along with the SMP or SMP composite, 162,high tension
spring, 160, are designed such that a small gap, 148, is left on
either side of the retracting bolts so that the retracting bolts
are not seized up by contact with the aft closure, inner holding
ring, or rocket casing. The retracting bolt ends attach to the
rocket casing and aft closure through existing threads and also
attaches to the SMP or SMP Composite encapsulated spring. When an
external thermal stimulus heats the SMP or SMP composite
encapsulated spring, the spring retracts, releasing the aft closure
from the case. Upon initial pressurization, the aft closure would
be ejected from the aft end of the rocket motor, increasing the
venting diameter by 700% with respect to the throat size on the aft
closure.
[0070] In all of the disclosed embodiments these SMPs or SMP
composites may have an integrated heating mechanism to provide for
the manual venting of a container. Preferably the heating mechanism
consists of wires embedded into the SMP or SMP composite, which
provide resistance heating when a current is passed through them.
As mentioned above, heating the SMP above its Tg will cause the SMP
to become soft and pliable or return to its memory shape depending
on the level of strain in the SMP prior to reaching its Tg;
however, other methods are available for activating the SMP
including light, UV radiation, other electromagnetic radiation,
water, and magnetic fields. Application of these stimuli will also
cause the SMP to transition between a soft pliable state to a hard
rigid state depending on the chemistry used in the manufacture of
the SMP resin. It will be apparent to one of skill in this art that
there are many different ways, besides resistance heating, to heat
the SMP or SMP composites, such as convective and radiation
heating, which are hereby included within the scope of the present
device.
[0071] In general, the preferred SMP is either a styrene copolymer
based SMP as disclosed in U.S. Pat. No. 6,759,481, an epoxy based
SMP as disclosed in PCT Application No. PCT/US2006/062179, and a
cyanate ester based SMP as disclosed in PCT Application No.
PCT/US2005/015685. However, other types of SMPs such as cyanate
ester, polyurethane, polyethylene homopolymer, styrene-butadiene,
polyisoprene, copolymers of stearyl acrylate and acrylic acid or
methyl acrylate, norbornene or dimethaneoctahydronapthalene
homopolymers or copolymers, malemide and other shape memory
polymers are within the scope of the present device.
[0072] The SMP or SMP composite, as discussed above, may include a
thermal energy generation means embedded therein. Such thermal
energy generation means may comprise, for example, thermally
conductive fibers or electrical conductors.
INDUSTRIAL APPLICABILITY
[0073] The lack of cheap, effective means for ensuring IM
compliance has been known in the art. The disclosed device
satisfies both the IM compliance requirements and does so in a
cheap and effective manner.
[0074] However, the applicability of this device is not limited to
IM or military uses. This device can be used to automatically vent
any container of hazardous or explosive material when environmental
conditions make the potential for damage or loss of life
unacceptable. The oil and chemical industry, gas stations,
refineries, storage facilities, and others can use this mechanism
without a massive redesign or remodel of the current systems used.
The ability to integrate this device into currently used systems
will be apparent to those of skill in the art.
[0075] Although this device has been described with respect to
certain preferred embodiments, it will be appreciated that a wide
variety of equivalents may be substituted for those specific
elements shown and described herein, all without departing from the
spirit and scope of the invention as defined in the appended
claims.
* * * * *