Note: Descriptions are shown in the official language in which they were submitted.
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PRESSURE RELIEF DEVICE
Field of the Invention
The present invention relates to a relief device which may be either thermally
or
pressure actuated to relieve pressure in pressurized containers when a pre-
determined
temperature or pressure in or around the container is exceeded.
Background of the Invention
Most vehicles or containers containing a gas or liquid under pressure are
equipped
with relief valves to prevent catastrophic rupture of the vessels in the case
of excessive
pressures or temperatures. For example, vehicles using alternative fuels such
as
compressed natural gas require the presence of one or more fuel cylinders
onboard
containing such gas under pressure. Federally mandated regulations require
that such
cylinders be equipped with relief valuing mechanism which, in the event of a
fire, will
allow the gas to escape from the cylinder before reaching an unacceptably high
pressure.
This reduces the potential for an explosion.
Several approaches have been used to produce acceptable thermally-actuated
pressure relief valves. For example, one approach has been to incorporate the
fusible
plug of an eutectic metal that blocks and seals an outlet passage in the
pressure vessel.
An example of such an approach is taught in US Patent Nos. 4,744,382 and
4,744,383.
In another approach, a fusible plug of a eutectic material is provided to
interfere with
movement of a valve member. Upon melting of the plug member, the valve member
is
released, unsealing a flow path to vent pressurized gases from a pressurized
container.
An example of such an approach is described in US Patent No. 5;632,297.
However, these known devices typically require relatively large amounts of
eutectic material. Further, the fusible plugs of these devices are typically
enclosed in a
metal housing, thereby insulating the fusible plug from the surrounding
environment, and
delaying its desired response.
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Summary~of the Invention
Apressure relief device comprising abodyincluding an exterior surface, a
cavity,
an inlet, an outlet, and an aperture, each of the inlet, the outlet, and the
aperture opening
into the cavity, a temperature sensitive bonding element, and a valve,
disposed within the
cavity and extending through the aperture, including a sealing member and a
cap, the cap
being joined to the exterior ofthe bodybythe temperature sensitive bonding
element, and
the sealing member being configured to seal the inlet when the cap is joined
to the
exterior surface of the body.
A pressure relief device comprising a body including an exterior surface, a
cavity,
an inlet, an outlet, and an aperture, each of the inlet, the outlet, and the
aperture opening
into the cavity, and a valve, disposed within the cavity and extending through
the
aperture, including a sealing member and a temperature sensitive cap, the
temperature
sensitive cap being joined to the exterior of the body and configured to
separate from the
body above a predetermined temperature, and the sealing member being
configured to
seal the inlet when the temperature sensitive cap is joined to the exterior
surface of the
body.
A pressure relief device comprising a body including a cavity, an inlet, and
an
outlet, each of the inlet and the outlet opening into the cavity, a first
temperature sensitive
bonding element, and a valve, disposed within the cavity, including a sealing
member,
shaft, and a valve bonding element, the shaft including a longitudinal axis
and j oining the
valve bonding element to the sealing member, the valve bonding element
extending
laterally outwards from the shaft and including a first valve bonding surface
presenting
a first planar surface, wherein the axis of the shaft is transverse to the
first planar surface,
and wherein the first valve bonding surface is joined to a first opposing
surface of the
body by the first temperature sensitive bonding element, wherein the first
opposing
surface is interposed between the first valve bonding surface and the valve
seat, and
wherein the sealing member is configured to seal the inlet when the valve is j
pined to the
body.
A pressure relief device comprising a body including an exterior surface, a
cavity,
an inlet, and an outlet, each of the inlet and the outlet opening into the
cavity, a
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temperature sensitive bonding element, a valve, disposed within the cavity,
including a
valve retainer and a sealing member, the valve retainer being coupled to the
sealing
member, the valve retainer being j oined to the body by the temperature
sensitive bonding
element, and the sealing member being biassed into a sealing relationship with
the inlet.
Brief Description of the Drawings
The embodiments of the present invention are described below with reference to
> the accompanying drawings in which:
Fig. 1 is a sectional elevation view of a first embodiment of a pressure
relief
device of the present invention, in an unactuated condition;
Fig. 2 is a sectional elevation view of a first embodiment of a pressure
relief
device of the present invention, in an actuated condition;
Fig. 3 is a sectional elevation view of a second embodiment of a pressure
relief
device of the present invention, in an unactuated condition;
Fig. 4 is a third embodiment of a pressure relief device of the present
invention,
in an unactuated condition;
Fig. 5 is a detailed sectional elevation view of a cap of the embodiment of
the
pressure relief device illustrated in Fig. 4;
Fig. 6 is a sectional elevation view of a fourth embodiment of a pressure
relief
device of the present invention, in an unactuated condition;
Fig. 7 is a fourth embodiment of a pressure relief device of the present
invention,
in a temperature actuated condition;
Fig. 8 is a sectional elevation view of a fourth embodiment of a pressure
relief
device of the present invention, in a pressure actuated condition;
Fig. 9 is a sectional elevation view of a fifth embodiment of a pressure
relief
device of the present invention, in an unactuated condition;
Fig. 10 is a fifth embodiment of a pressure relief device of the present
invention,
in a temperature actuated condition; and
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Fig. 11 is a sectional elevation view of a fifth embodiment of a pressure
relief
device of the present invention in a pressure actuated condition.
Detailed Description
The present invention provides a pressure relief device for venting of gases
from
a vessel or other container in the event of unacceptably high temperature
conditions in
the environment immediate to the vessel.
Referring to Figure 1, in one embodiment, the present invention provides a
~ pressure relief device 10 comprising a body 12, a temperature sensitive
bonding element
14, and a valve 16. The body 12 includes an exterior surface 18, a cavity 20,
an inlet 22,
an outlet 24, and an aperture 26. Each of the inlet 22, outlet 24, and
aperture 26 open into
the cavity. The valve 16 is disposed within the cavity 20 and extends through
the
aperture 26 and is joined to the exterior surface 18 of the body 12 by the
temperature
sensitive bonding element 14. The valve 16 includes a sealing member 28
configured to
seal the inlet 22 from the outlet 24 by sealingly engaging a valve seat 30
provided at and
defining the inlet 32, thereby preventing communication between the inlet 22
and the
outlet 24, when the valve 16 is joined to the exterior surface 18 of the body
12.
The valve 16 includes a cap 32. The cap 32 is joined to the exterior surface
18
of the body 12 by the temperature sensitive bonding element 14. The cap 32
includes a
valve bonding surface 34, and the valve bonding surface 34 is joined to an
opposing
exterior surface 36 of the body 12 by the temperature sensitive bonding
element 14. The
temperature sensitive element 14 is interposed between the valve bonding
surface 34 and
the opposing exterior surface 36 of the body 12 to thereby bond the cap 32,
and therefore
the valve 16, to the exterior surface 18 of the body 12. In this respect, the
combination
of the cap 32 and the temperature sensitive bonding element 14 functions as a
temperature sensitive cap 38 which becomes unsecured relative to, or
disengages from
the exterior surface 18 of the body 12 above a predetermined temperature.
It is understood that the valve bonding surface 34 of the pressure relief
device 10
embodiment illustrated in Figs. 1 and 2 need not necessarily be planar.
Optionally, the
valve bonding surface 34 can be curved.
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The temperature sensitive bonding element 14 comprises any material which
forms a bond with each of the cap 32 and the body 12 below a predetermined
temperature, and which undergoes physical and/or chemical changes above the
predetermined temperature to cause weakening of the previously formed bonds.
For
example, the temperature-sensitive bonding element 14 comprises a low melt
alloy or a
fusible metal with characteristics to effect bonding with the surfaces of each
of the cap
32 and the body 12. As an example, and in this respect, the temperature
sensitive
bonding element 14 can be a solder. The temperature sensitive bonding element
14 can
also comprise a polymer. The temperature sensitive bonding element 14 is
provided to
j oin the cap 32 to the body 12. In this respect, the temperature sensitive
bonding element
14 includes a first surface bonded to the cap 32, and a second suxface bonded
to the body.
Such bonding occurs under lower temperature conditions, such as ambient
temperature
conditions. At higher temperatures, the bonding between the temperature
sensitive
bonding element and each of, or either of, the cap 32 and the body 12 becomes
weakened,
thereby permitting the cap 32 to move away from the body 12, remotely from the
inlet
22, upon application of external forces to the valve 16.
The valve 16 includes an annular groove 40 carrying the sealing member 28
including an o-ring 42 and a back-up o-ring 44. The sealing member 28 is
configured to
engage the valve seat 30 at the inlet 22, and thereby effect sealing of the
inlet 22, and
prevent communication between the inlet 22 and the outlet 24, except under
abnormal
operating conditions (i. e., undesirably high temperature conditions, when j
oinder between
the cap 32 and the body 12 by the temperature sensitive bonding element 14 is
weakened,
and subsequently severed).
A resilient member 43 such as a spring, can be provided and configured to bias
the valve 16 and its sealing member 28 away from the valve seat 30 (i.e., the
resilient
member 43 biases the valve 16 towards an unseated position in relation to the
valve seat
30). In this respect, the resilient member 43 assists unseating of the valve
16 from the
valve seat 30 when the cap 32 has become disengaged from the body 12, which is
particularly helpful in the event of low pressure conditions in the associated
vessel or
container.
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The valve 16 is disposed within the cavity 20 and moveable within the cavity
20
upon disengagement of the cap 32 from the exterior surface 18 of the body 12.
Preferably, the valve 16 is sealingly disposed within the cavity 20 to prevent
communication between the aperture 26 and either of the inlet 22 or the outlet
24. In this
respect, the valve I6 is sealingly disposed within the cavity 20 between (i)
the inlet 22
and the outlet 24, and (ii) the aperture 26. To effect this, the valve 16
includes a sealing
member 46 disposed between (i) the inlet 22 and the outlet 24, and (ii) the
aperture 26.
Such sealing disposition of the valve 16 within the cavity 20 ensures venting
of gases
from the inlet 22 to the outlet 24 and then to a controlled location.
Preferably, the body 12 includes a retainer 48 or abutment configured to
prevent
the valve 16 from separating from the body 12, once the cap 32 disengages from
the
exterior surface 18 of the body 12. Without such a retainer 48 or abutment,
the valve 46
is free to be expelled from the aperture 26 by combined pressure and spring
forces, and
become a potentially dangerous projectile.
As an example, the retainer 48 is disposed within the cavity 20 and functions
as
an abutment to physically engage the valve 16 and thereby limit movement of
the valve
16 away from the valve seat 30. In this respect, the valve 16 includes a shaft
50 including
a longitudinal axis 52. The valve 16 is substantially moveable along the
longitudinal axis
52 (the valve is either closely spaced apart from the cavity, or is sealingly
disposed within
the cavity). The shaft 50 is interposed between and joins the sealing member
28 to the
cap 32. The shaft 50 includes a radially enlarged section 54 and first and
second sections
56, 58 extending in opposite directions from the radially enlarged section 54.
The first
section 56 extends from the radially enlarged section to the sealing surface
28. The
second section 58 extends from the radially enlarged section 54 to the cap 32.
The
radially enlarged section 54 includes an operative surface 60 which extends
further
radially outwards from the longitudinal axis 52 relative to the second section
58. The
retainer 48 extends from a cavity wall 62 and presents a retainer abutment
surface 64
including a transverse axis which is transverse to the operative surface 60
and is
configured to interfere with and limit movement of the operative surface 60.
The retainer
48 further includes a passage 66 within which the second section 58 of the
shaft 50 is
. disposed and extends through to join the cap 32. The retainer passage 66 is
configured
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to permit unobstructed movement of the second section 58 of the shaft 50
therethrough.
To effect sealing disposition of the valve 16 within the cavity 20, the
radially
enlarged section 54 includes an annular groove 68 carrying the sealing member
46, such
as an o-ring. The o-ring sealingly engages the cavity wall 62, thereby
preventing
communication between the aperture 26 and each of the inlet 22 and the outlet
24.
Optionally, the resilient member 43 is interposed within the cavity 20 and
supported between the radially enlarged section 54 and the valve seat 30 (a
shoulder
surface provided in the cavity), to thereby urge the valve 16 away from the
valve seat 30.
Figures 1 and 2 illustrate an embodiment of the pressure relief device 10 of
the
present invention in two conditions. Figure 1 illustrates the pressure relief
device 10 in
an unactuated condition. Figure 2 illustrates the pressure relief device 10 in
an actuated
condition.
Referring to Figure 1, in the unactuated condition, the cap 32 is joined to
the
exterior surface 18 of the body 12, and the sealing member 28 engages the
valve seat 30
and thereby seals the inlet 22 from the outlet 24. The second section 58 of
the valve shaft
50 extends through the passage 66 provided in the retainer 48, and the
radially enlarged
section 54 of the valve shaft 50 is spaced from the retainer 48.
When temperature conditions become undesirably high, bonding between the
temperature sensitive bonding element 14 and each of, or either of, the cap 32
and the
exterior surface 18 of the body 12 weakens. As a result, the combined forces
of the
resilient member 43, and those attributable to gaseous pressures at the inlet
22, act upon
the valve I6. These forces are translated to the cap 32, and eventually sever
the bonds
between the temperature sensitive bonding element 14 and each of, or either
of, the cap
32 and the exterior surface 18 of the body I2. Once such bonds are severed,
unseating
of the sealing surface 28 from the valve seat 30 by the same above-described
forces is
made possible.
Referring to Figure 2, the pressure relief device 10 has become actuated upon
unseating of the sealing member 28 from the valve seat 30. Unseating of the
sealing
member 28 from the valve seat 30 unseals the inlet 22, thereby effecting
communication
between the inlet 22 and the outlet 24. Communication between the inlet 22 and
the
outlet 24 facilitates pressure relief from the inlet 22 and any associated
upstream vessel °
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or container. Unseating of the sealing member 28 also necessarily entails
movement of
the sealing member 28, and therefore the valve 16, away from the valve seat
30. In this
respect, upon actuation, the valve 16 moves through the cavity 50 until the
radially
enlarged section 54 becomes physically engaged to the retainer 48. Once
engaged to the
retainer 48, further movement of the sealing member 28, and therefore the
valve 10, away
from the valve seat 30 is prevented.
Figures 3, 4 and 5 illustrate further embodiments 110, 210 of the pressure
relief
device of the present invention, similar to the embodiment illustrated in
Figures 1 and 2.
Like reference numerals refer to like elements. The bonding arrangements
illustrated in
the Figures 3, 4 and 5 embodiments can be optionally applied to the Figure 1
and 2
embodiment.
Referring to Figure 3, the pressure relief device 110 in the Figure 3
embodiment
is similar to the embodiment of the pressure relief device 10 in Figures 1 and
2 with the
exception of the nature of the bonding arrangement of the cap 32 to the body
12. In the
Figure 3 embodiment, the valve bonding surface 134 of the cap 32 presents a
planar
surface such that the longitudinal axis 52 of the shaft 50 is transverse to
the planar
surface. As an example, the longitudinal axis 52 is perpendicular, or
substantially
perpendicular, to the planar surface presented by the valve bonding surface
34. The
planar surface is joined to an opposing surface 112 of the body 12 by the
temperature
sensitive bonding element 14, wherein the opposing surface 112 is interposed
between
the valve bonding surface 134 and the valve seat 30. Such bonding creates a
relatively
strong tensile bond between the cap 32 and the body 12, as opposed to a bond
which is
in shear, as would be the case if the valve 16 was bonded to the body 12 along
.a plane
parallel to the axis 52 of the shaft 50.
Refernng to Figures 4 and 5, the pressure relief device 210 in the Figure 4
embodiment is similar to the pressure relief devices 10, I10 in the Figures 1
and 2
embodiment and the Figure 3 embodiment, with the exception of the nature of
the
bonding arrangement of the cap 32 to the body 12. The pressure relief device
210 of the
Figure 4 embodiment includes a cap 32 with a first valve bonding surface 212
which
presents a planar surface such that the longitudinal axis 52 of the shaft 55
is transverse
to the planar surface. For example, the longitudinal axis 52 is perpendicular,
or
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substantially perpendicular, to~the planar surface presented by the first
valve bonding
surface 212. The planar surface is j oined to an opposing first bonding
surface 214 of the
body 12 by a first temperature sensitive bonding element 216, wherein the
first bonding
surface 214 is interposed between the first valve bonding surface 212 and the
valve seat
30. Further, the shaft 50 of the valve 16 presents a second valve bonding
surface 218
presenting a planax surface j oined to an opposing second bonding surface 220
within the
cavity of the body by a second temperature sensitive bonding element. 222. The
second
valve bonding surface 218 includes a transverse axis which is transverse to
the planar
surface of the first valve bonding surface 212. By joining the shaft 50 to the
body 12,
peeling of the cap 32 from the body 12 is mitigated. Even when unactuated, the
shaft 50
of the valve 16 is subject to pressure and spring forces which act on the cap
16 in a
direction which urges the cap 32 to separate from the body 12. Such forces
could
potentially weaken and compromise the bonding between the temperature
sensitive
element 14 and each of, or either of, the cap 32 and the body 12. The bonding
which
would initially be weakened would be that nearest to the shaft ,50. To
mitigate
weakening, and subsequent peeling of this bonding, the shaft 50 is bonded to
the body
12 to further distribute the forces being applied by the shaft 50.
Figures 6, 7 and 8 illustrate a ftirther embodiment of the pressure relief
device
of the present invention in unactuated (Figure 6) temperature actuated (Figure
7), and
pressure actuated (Figure 8) conditions. The pressure relief device in the
Figures 6, 7 and
8 embodiment is configured for actuation by either high temperature or high
pressure
conditions.
In this respect, referring to Figure 6, a pressure relief device 310 is
provided
comprising a body 312, a temperature sensitive bonding element 314, and a
valve 316.
The body 312 includes a cavity 318, an inlet 320, an outlet 322, wherein each
of the inlet
320 and the outlet 322 opens into the cavity 318. The valve 316 is disposed
within the
cavity 318 and includes a valve retainer 324 and a piston 326. The valve
retainer 324 is
joined to the body 312 by the temperature sensitive bonding element 314. The
piston 326
includes a sealing member 328 configured to engage a valve seat 330 provided
at, and
defining, the inlet 320, thereby sealing the inlet 320 from communication with
the outlet
322, when the retainer 324 is joined to the body 312. The valve 316 also
includes a
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resilient member 332, such as a spring, interposed between, supported by, and
coupled
to each of the piston 326 and the valve retainer 324. In this respect, the
piston 326 is
biassed or urged into sealing engagement with the valve seat 330 while also
being
coupled to the valve retainer 324. The resilient member 332 also biases or
urges the
valve retainer 324 away from the valve seat 322.
The piston 326 carries the sealing member 328. The sealing member 328 is
configured to engage the valve seat 330 at the inlet 320, and thereby effect
sealing of the
inlet 320, and prevent communication between the inlet 320 and the outlet 322,
except
under abnormal operating conditions (ie. undesirablyhigh temperature
conditions, when
joinder between the valve retainer 324 and the body 312 by the temperature
sensitive
bonding element 314 is weakened, and subsequently severed, or high pressure
conditions
which effect unseating of the piston 326 from the valve seat 330).
The temperature sensitive bonding element 314 comprises any material which
forms a bond with each of the cap and the body below a predetermined
temperature, and
which undergoes physical and/or chemical changes above the predetermined
temperature
to cause weakening of the previously-formed bonds. For example, the
temperature-
sensitive bonding element comprises a low melt alloy or a fusible metal with
characteristics to effect bonding with the surfaces of each of the valve
retainer 324 and
the body 312. For example, the temperature-sensitive bonding element 314
comprises
solder. The temperature-sensitive bonding element 314 can also comprise a
polymer.
The temperature sensitive bonding element 314 is provided to join the valve
retainer 324
to the body 312. In this respect, the temperature sensitive bonding element
314 includes
a first surface bonded to the valve retainer 324 , and a second surface bonded
to the body
312. Such bonding occurs under lower temperature conditions, such as ambient
temperature conditions. At higher temperatures, the bonding between the
temperature -
sensitive bonding element and each of, or either of, the valve retainer 324
and the body
312 becomes weakened, therebypermitting the valve retainer 324 to move away
from the
body 312, remotely from the inlet, upon application of external forces to the
valve 324.
The valve 316 is disposed within the cavity 318. Particularly, the valve
retainer
324 is joined to. the wall 334 of the cavity 318. The cavity 318is configured
with
sufficient space to receive and retain the valve 316 once actuated in the
manner described
CA 02436210 2003-07-16
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below. As one example, the valve retainer 324 comprises an axially extending
collar,
which is joined along its length to the wall 334 of the cavity 318 by the
temperature
sensitive bonding element 314 interposed therebetween.
Referring to Figure 7, when the temperature exceeds a predetermined maximum
value, bonding between the temperature sensitive bonding element 314 and each
of, or
either of, the retainer 324 and the body 312 weakens. As a result, the
combined forces
of the resilient member 332, and those attributable to gaseous pressure at the
inlet 320,
act upon the retainer 324 through the piston 326 and the resilient member 332,
and
eventually sever the bonds between the temperature sensitive bonding element
314 and
each of, or either of, the retainer 324 and the body 312. Once such bonds are
severed,
support of the resilient member 332 by the valve retainer 324 is substantially
compromised such that forces biasing the piston 326 and its sealing surface
328 to remain
seated against the valve seat 330 are significantly, if not substantially,
removed.
Gaseous forces are permitted to act substantially unopposed against the
sealing surface
328, thereby cause unseating of the sealing surface 328 from the valve seat
330. As a
result, communication between the inlet 320 and outlet 322 is effected,
facilitating
pressure relief from the inlet 320and associated vessel or container.
Similarly, when pressure at the inlet 320 exceeds a predetermined maximum
value, the pressure relief device 310 can also be actuated (see Figure 8). At
the
predetermined maximum value, the pre-set compressive forces exerted by the
resilient
member 332 will be exceeded by the pressure at the inlet 320. The increased
pressure
will unseat the piston 326 and cause opening of the inlet 320., As a result,
communication between the inlet 320 and outlet 322 will be effected, thereby
facilitating
pressure relief from the inlet 320 (and associated vessel or container).
25' Unlike the case of actuation of the pressure relief device 310 in response
to
undesirablyhigh temperature conditions, the removal of the abnormal pressure
conditions
at the inlet 320 will permit the piston 324 to return to a seated position
against the valve
seat 330, thereby permitting re-use of the pressure relief device 310. When
the pressure
relief device 310 is actuated by undesirably high pressure conditions, gases
will flow
from the inlet 320 to the outlet 322, and gas pressure will be reduced at the
inlet 320 as
gaseous inventory in the associated vessel or container becomes depleted. Once
the gas
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pressure at the inlet 320 is reduced, below the predetermined maximum
pressure, the
compressive forces of the resilient member 332 will again be sufficient to
cause the
piston 326 and its sealing member 328 to sealingly engage the valve seat 330
and seal the
inlet 320.
Figures 9,10, and 11 illustrate a further embodiment of the pressure relief
device
of the present invention, similar to the embodiment illustrated in Figures 6,
7, and 8.
Like reference numerals refer to like elements.
The pressure relief device 410 in the Figures 9,10, and 11 embodiment is
similar
to the embodiment of the pressure relief device in Figures 6, 7, and 8 with
the exception
of the nature of the bonding arrangement of the retainer 324 to the body 312.
In the
Figures 9, 10 and 11 embodiment, the valve 316 includes a valve retainer 324
which is
joined to the exterior surface 340 of the body 312. In this respect, the valve
retainer 324
includes a cap 342. The cap 342 is joined to the exterior surface 340 of the
body 312
with a temperature sensitive bonding element 314. The bonding arrangement
illustrated
in the Figures 3 and 4 embodiments can be optionally applied to the Figures 9,
10, and
11 embodiment.
Referring to Figure 9, the body 312 further includes an aperture 344 defined
by
the exterior surface 340 of the body 312. The valve 316 extends through the
aperture 344
such that the cap 342 is joined to the exterior surface 340 by the temperature
sensitive
bonding element 314. In this respect, the cap 342 includes a valve bonding
surface 346,
and the valve bonding surface 346 is joined to an opposing exterior surface
348 of the
body 312 by the temperature sensitive bonding element 314. The temperature
sensitive
element 314 is interposed between the valve bonding surface 346 and the
opposing
exterior surface 348 of the body 312 to thereby bond the cap 342, and
therefore the valve
316, to the exterior surface 340 of the body 312.
The valve 316 is disposed within the cavity 318 and moveable within the cavity
318 upon disengagement of the cap 342 from the exterior surface 340 of the
body 312.
Preferably, the valve 316 is sealingly disposed within the cavity 318 .to
prevent
communication between the aperture 344 and either of the inlet 320 or the
outlet 322.
In this respect, the valve 316 is sealingly disposed within the cavity 318
between (i) the
inlet 320 and the outlet 322, and (ii) the aperture 326. To effect this, the
valve 316
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includes a sealing member 328 disposed between (i) the inlet 320 and the
outlet 322, and
(ii) the aperture 326. Such sealing disposition of the valve 316 within the
cavity 318
ensures venting of gases from the inlet 320 to the outlet 322 and then to a
controlled
location.
The body 312 includes a body abutment 350 configured to prevent the valve 316,
and particularly the valve retainer 324, from separating from the body 312,
once the cap
342 disengages from the exterior surface 340 of the body 312. Without such an
abutment
350, the valve 316, or at least the valve retainer 324, is free to be expelled
from the
opening by combined pressure and spring forces, and become a potentially
dangerous
projectile.
For example, the body abutment 350 is disposed within the cavity 318 and
functions to physically engage the valve 316 and thereby limit movement of the
valve
316 away from the valve seat 330. In this respect, the valve retainer 324
includes a
radially enlarged section 352 and a shaft 354. The shaft 354 extends from the
radially
enlarged section 352 and joins the cap 342 to the radially enlarged section
352. The shaft
354 includes a longitudinal axis 356. The valve 316 is substantially moveable
along the
longitudinal axis 356 (the valve 316 is either closely spaced apart from the
wall 334 of
the cavity 318, or is sealingly disposed within the cavity 318, throughout its
distance of
travel). The radially enlarged section 352 includes an operative surface 358
which
extends further radially outwards from the longitudinal axis 356 relative to
the shaft
section 354. The abutment 350 extends from the cavity wall 334 and presents an
abutment surface 360 including a transverse axis which is transverse to the
operative
surface 358 and is configured to interfere with and limit movement of the
operative
surface 358. The abutment 350 further includes apassage 362 withinwhich the
shaft 354
of the valve retainer 324 is disposed and extends through to join the cap 342.
The
passage 362 is configured to permit unobstructed movement of the shaft 354 of
the valve
retainer 324 therethrough.
To effect sealing disposition of the valve 316 within the cavity 318, the
radially
enlarged section 352 includes an annular groove 364 carrying a sealing member
366, such
as an o-ring. The o-ring sealingly engages the cavity wall 334, thereby
preventing
communication between the aperture 344 and each of the inlet 320 and the
outlet 322.
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Optionally, the resilient member 332 is interposed between, coupled to, and
supported by each of the radially enlarged section 352 of the valve retainer
324 and the
piston 326.
The valve retainer also includes a recess 368 for receiving the piston 326
when
the piston 326 becomes unseated from the valve seat 330 during high pressure
conditions,
as described below. The recess 368 is axially aligned with the piston 324. In
the
embodiment illustrated, the recess 368 is provided in the radially enlarged
section 352
of the valve retainer 324.
Under normal operating conditions, that is when temperature conditions in the
immediate environment to that of the relief device 410 do not exceed a maximum
predetermined value, and the pressure conditions at the inlet 320 (and,
therefore, in the
associated vessel or container) do not exceed a maximum predetermined value,
the
temperature sensitive bonding element 314 remains bonded to each of the cap
342 and
the exterior surface 340 of the body 312. Forces exerted by the resilient
member 332
upon the piston 326 are sufficient to overcome any opposing forces exerted by
the gas
pressure at the inlet 320. As a result, the sealing surface 328 of the piston
326 remains
seated against the valve seat 330, thereby sealing the inlet 320 and
preventing any
communication between the inlet 320 (i.e., from the vessel or storage
container) and the
outlet 322.
If, however, temperature conditions exceed a maximum predetermined value (see
Figure 10), bonding between the temperature sensitive bonding element 314 and
each
of, or either of, the exterior surface 340 of the body 312 and the cap 342
weakens. As a
result, the combined forces of the resilient member 332, and those
attributable to gaseous
pressures at the inlet 320, act upon the cap 342 and eventually sever the
bonds between
the temperature sensitive element 314 and each of, or either of, the cap 342
and the
exterior surface 340 of the body 312. Once such bonds are severed, the piston
326 is
forced away from the valve seat 330, thereby unsealing the inlet 320 and
effecting
communication between the inlet 320 and the outlet 322, and facilitating
pressure relief
from the inlet 320 (and corresponding vessel or container).
Likewise, if the pressure at the inlet 320 (and in the associated vessel or
storage
container) exceeds a predetermined maximum value, the relief device 410 will
also be
14
CA 02436210 2003-07-16
WO 02/075191 PCT/CA02/00372
actuated (Figure 10). At the predetermined maximum value, the pre-set
compressive
forces exerted by the resilient member 332 will be exceeded by the pressure at
the inlet
320. The increased pressure will unseat the piston 326 and cause the piston
326 to move
into the annular recess 368 of the valve retainer 324. As a result,
communication
between the inlet 320 and outlet 322 will be effected, thereby facilitating
pressure relief
from the inlet 320 (and corresponding vessel or container).
Unlike the case of actuation of the pressure relief device 410 in response to
undesirably high temperature conditions, the removal of the abnormal pressure
conditions
at the inlet 320 will permit the piston 326 to return to a seated position
against the valve
seat 330, thereby permitting reuse of the pressure relief device 410. When the
pressure
relief device 410 is actuated by undesirably high temperature conditions,
gases will flow
from the inlet 320 to the outlet 322, and gas pressure will be reduced at the
inlet 320 as
gaseous inventory in the associated vessel or container becomes depleted. Once
the gas
pressure at the inlet 320 is sufficientlyreduced, below predetermined maximum
pressure,
the compressive forces of the resilient member 332 will again be sufficient to
cause the
piston 326 and its sealing member 328 to sealingly engage the valve seat 330
and seal
the inlet 320.
Although the disclosure describes and illustrates preferred embodiments of the
invention, it is to be understood that the invention is not limited to these
particular
embodiments. Many variations and modifications will now occur to those skilled
in.the
art. For definition of the invention, reference is to be made to the appended
claims.
