U.S. patent application number 11/995462 was filed with the patent office on 2008-09-11 for safety valve for a compressed gas container.
This patent application is currently assigned to JOB LIZENZ GMBH & CO. KG. Invention is credited to Eduard J. Job.
Application Number | 20080217572 11/995462 |
Document ID | / |
Family ID | 35058732 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080217572 |
Kind Code |
A1 |
Job; Eduard J. |
September 11, 2008 |
Safety Valve for a Compressed Gas Container
Abstract
A safety valve for a compressed gas container having an overflow
duct (2) connected to the compressed gas container and having an
outlet duct (3) and having a thermal triggering unit which
comprises a closure body (15; 20) that is displaceable out of a
standby position in which it holds the overflow duct tightly sealed
with respect to the outlet duct in cooperation with a sealing
element (9), into a release position in which the overflow duct (2)
is connected to the outlet duct and also comprises a burst body (8)
which is arranged between an abutment and a closure body (15; 20)
to hold the latter in the standby position, such that the thermal
triggering unit comprises a spring element (10; 11; 21) which
exerts a spring force directed in the direction of the abutment on
the burst body (8), characterized in that the closure body (15; 20)
is an element having an essentially wedge-shaped cross section and
having rotational symmetry about a central axis, said element
engaging in the inside diameter of the O ring and pressing it at
least radially against a wall of the overflow duct (2) with its
sealing surface (28) which is designed in a wedge shape, being
broader at its wider diameter than the inside diameter of the O
ring as the sealing element (9).
Inventors: |
Job; Eduard J.; (Ahrensburg,
DE) |
Correspondence
Address: |
SAND & SEBOLT
AEGIS TOWER, SUITE 1100, 4940 MUNSON STREET, NW
CANTON
OH
44718-3615
US
|
Assignee: |
JOB LIZENZ GMBH & CO.
KG
Ahrensburg
DE
|
Family ID: |
35058732 |
Appl. No.: |
11/995462 |
Filed: |
July 10, 2006 |
PCT Filed: |
July 10, 2006 |
PCT NO: |
PCT/EP06/06721 |
371 Date: |
January 11, 2008 |
Current U.S.
Class: |
251/337 |
Current CPC
Class: |
F16K 17/38 20130101 |
Class at
Publication: |
251/337 |
International
Class: |
F01L 3/10 20060101
F01L003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2005 |
EP |
05015968.0 |
Claims
1. A safety valve for a compressed gas container having an overflow
duct connected to the compressed gas container and an outlet duct
and having a thermal triggering unit, which comprises a closure
body that is displaceable out of a standby position in which it
holds the overflow duct tightly sealed with respect to the outlet
duct in cooperation with a sealing element, into a release position
in which the overflow duct is connected to the outlet duct and also
comprises a burst body, which is arranged between an abutment and a
closure body to hold the latter in the standby position, such that
the thermal triggering unit comprises a spring element which exerts
a spring force directed in the direction of the abutment on the
burst body, wherein the closure body is an element having an
essentially wedge-shaped cross section and having rotational
symmetry about a central axis, said element engaging in the inside
diameter of the O ring and pressing it at least radially against a
wall of the overflow duct with its sealing surface which is
designed in a wedge shape, being broader at its wider diameter than
the inside diameter of the O ring as the sealing element.
2. The safety valve according to claim 1 wherein the sealing
surface has a concave curvature.
3. The safety valve according to claim 2 wherein the curvature of
the sealing surface having a concave curvature corresponds in its
curvature to the curvature of a sealing surface of the O ring in at
least one section.
4. The safety valve according to claim 1 wherein a first shoulder
is provided in the overflow duct, a first plate spring resting on
said shoulder, the O ring resting on said first plate spring and
supported thereon and on the wall of the overflow duct in a sealing
manner, such that the closure body is in contact with the O ring on
the side opposite the first plate spring and a second plate spring
is arranged on the side of the closure body opposite the O ring,
resting on a second shoulder formed in the overflow duct and the
burst element being supported on the side thereof opposite the
closure body.
5. The safety valve according to claim 1 wherein the spring element
is arranged on the side of the burst body opposite the
abutment.
6. The safety valve according to claim 1 wherein the spring element
is a plate spring placed on a shoulder in the overflow duct.
7. The safety valve according to claim 1 wherein the burst body is
a fluid-filled glass ampoule clamped axially between the closure
body and the abutment.
Description
[0001] The invention relates to a safety valve for a compressed gas
container according to the preamble of Claim 1.
[0002] Such a safety valve is disclosed in EP 0 960 634 A2, namely
in the exemplary embodiment according to FIG. 4 there. Another
safety valve designed differently from the preamble of Claim 1 is
disclosed in the patent DE 199 11 530 C2.
[0003] According to the industrial standards for compressed gases,
e.g., TTRG381, compressed gas containers must be equipped with a
cut-out fuse or a similar acting fuse to reliably prevent excess
pressure in the event of a fire, which could lead to rupture of the
container.
[0004] This is also true, for example, of compressed gas containers
in motor vehicles to hold, e.g., natural gas, hydrogen or other
combustible gases for use as a fuel.
[0005] The variant of such a safety valve known previously from DE
199 11 530 C3, which was cited above, contains a closure body,
which is supported in a standby position directly on the metal of a
housing in which an overflow duct is formed. Then the burst body,
which in this example is a glass ampoule, is then in turn supported
directly on the closure body itself. According to the teaching
disclosed in the aforementioned publication, the glass ampoule is
ultimately clamped between two rigidly connected supports. With
this arrangement, the differences between the thermal expansion
coefficients of the metal of which the closure body and the housing
are made and the glass material of the burst body result in the
risk that the burst body may rupture during cooling and/or heating,
e.g., because the metal of the closure body and the housing expands
or contracts to a greater extent than the glass material of the
burst body and therefore compresses it, especially during cooling.
The problem of different temperatures and thus different expansions
of the aforementioned materials occurs in particular with
compressed gas containers accommodated in vehicles and/or safety
valves provided on them. Especially when a motor vehicle is parked
outdoors, it is exposed to temperatures ranging from -50.degree. C.
in the winter up to 50.degree. C. or more (if in direct sun) in the
summer, and temperature may even fall far below the aforementioned
ambient temperatures during the operation of filling the pressure
vessel. Because of this wide temperature range of 100.degree. C. or
more, the different thermal expansion coefficients of metal and
glass are definitely manifested. In other words, there may be
unintentional triggering of the safety valve, resulting in an
outflow of the gas contained in the compressed gas container.
However, the same considerations with regard to the thermal
expansion coefficients also apply to other compressed gas
containers and/or the safety valves arranged in them, which are
exposed to high temperature fluctuations.
[0006] FIG. 4 in DE 199 11 530 C2 shows another variant of a safety
valve which deviates in its features from the preamble of Claim 1.
In this case, a film forms the closure for the overflow duct, this
film being punctured by a plunger that is under spring tension when
the burst body ruptures, thereby connecting the overflow duct to
the outlet duct. One problem with this approach is that the film
can be damaged during installation of the safety valve and can thus
become permeable, resulting in unintentional leakage of the
contents of the pressure vessel through the safety valve without
rupturing the burst body due to high temperatures and without
triggering the safety valve. Furthermore, gases under high
pressures (often several hundred bar) are stored in the compressed
gas containers for which the safety valves are to be used, so that
a simple film is often inadequate to reliably withstand such
pressures.
[0007] In the EP 0 960 634 A2 cited in the introductory part, a
remedy is given for the disadvantages of the safety valves
according to DE 199 11 530 C3. However, a burst disk that might
trigger the safety valve is required here.
[0008] The object of the present invention is therefore to improve
upon a safety valve for compressed gas containers of the type
defined in the introductory part so that the advantages of the
buffering of different thermal expansions as described in EP 0 960
634 A2 can be utilized without the requirement of a burst disk as
an additional safety-relevant part.
[0009] This object is achieved by a safety valve having the
features of Patent Claim 1.
[0010] Advantageous further embodiments of the invention are
characterized in the dependent Claims 2 through 7.
[0011] The inventive safety valve is characterized in that it
comprises a sealing element with which the closure body cooperates
to seal the overflow duct, in addition to having such a closure
body as in some of the variants disclosed in DE 199 11 530 C2.
Unlike sprinkler systems, for example, in which a line under
pressure is usually sealed directly by a closing body held in
position by a burst body without another sealing element, this is
impossible with compressed gas containers filled with gases under
high pressure. The pressure in water lines of sprinkler systems is
usually max. 12 bar. In the compressed gas containers equipped with
the inventive safety valves, gases with pressures of several
hundred bar, e.g., 300 bar, are stored. At these pressures,
reliable sealing of the overflow line is possible with the help of
a sealing element in the form of an O ring. This design variant is
also described in one of the embodiments of a previously known
safety valve described in DE 199 11 530 C2 which was cited
above.
[0012] O rings are commercially available parts which can be
acquired easily and inexpensively and offer a good seal with
respect to the particular sealing surfaces. The material of the O
ring should be selected so that it is suitable for the
corresponding temperature ranges and does not tend to stick on the
sealing surfaces, for example, which might lead to delayed
triggering of the safety valve, or in the worst case might even
prevent triggering of the safety valve if the O ring holds the
closure body cooperating with it in sealing contact with the
sealing surfaces even if the burst body has already ruptured.
[0013] In addition to the features known from DE 199 11 530 C2, the
inventive safety valve, as shown in FIG. 4 of EP 0 960 634 A2
comprises a spring element which exerts a spring force on the burst
body acting in the direction of the abutment. This spring element
serves specifically to absorb the stresses, i.e., forces occurring
due to different thermal expansion coefficients of the housing and
the safety valve and/or the closing body and/or the abutment and
the burst body and thus serves to prevent the burst body from
rupturing inadvertently before reaching a triggering temperature
and thereby inadvertently triggering the safety valve.
[0014] To compensate for loads acting on the burst body due to
different thermal expansion coefficients, it would essentially also
be possible to provide a spring element which prestresses the burst
body in the opposite direction. However, such an approach would
have the significant disadvantage that the spring element that
prestresses the burst element in the direction of the closing body
which closes the outlet duct must counteract a maximum pressure to
be expected. In other words, the spring element would have to apply
a force to the burst body which can withstand, e.g., a maximum
pressure of 300 bar and test pressures of up to 1000 bar or even
more. The burst body would thus be exposed to a high force over the
entire lifetime of the safety valve which could alter the burst
body over a long period of time. In particular a burst body made of
glass (e.g., a glass ampoule) would have a tendency to "yield,"
under such conditions, i.e., the glass would change its shape. This
could ultimately result in leakage and malfunction of the safety
valve, with all the safety-relevant consequences thereof.
[0015] However, the selected direction of the spring force allows
only a comparatively low prestress of the burst body because the
spring force in this direction acts like the force due to the
pressure in the pressure vessel. In the normal case, only pressure
loads amounting to a fraction of the maximum load are then acting
on the burst body, which leads to a definite increase in the
lifetime of the burst body and thus also the safety valve.
[0016] The closure body shaped as indicated in Claim 1 is
ultimately especially suitable for applying a sufficiently high
pressing force to the O ring and thus achieving a reliable seal of
the overflow duct in the standby position and thus making the burst
disk provided in EP 0 960 634 A2 superfluous.
[0017] An especially good seal can be achieved if the sealing
surface of the sealing element is designed with a concave curvature
(Claim 2) in particular when the concave curvature of the sealing
surface corresponds to the curvature of a sealing surface of the O
ring in at least one section (Claim 3).
[0018] The variant of this preferred embodiment characterized in
Claim 4 offers especially good spring support for changes in length
due to different thermal expansions and thus a safety valve, which
is especially stable at temperatures below the triggering
temperature, and does so through a total of two plate springs
arranged in the overflow duct.
[0019] In a preferred variant of the invention, the spring element
is a spring placed on a shoulder in the overflow duct, in
particular such a plate spring. This then acts on an end of the
burst body opposite the abutment to act on it with a spring force
in the direction of the abutment. A plate spring is a small
effective component that does not prevent reliable triggering of
the safety valve.
[0020] A fluid-filled glass ampoule clamped between the closure
body and the abutment is preferred as the burst body. Through an
appropriate choice of the thickness of the glass and the type of
fluid, a defined triggering temperature in a comparatively narrow
window can be preselected for such a burst body so that safety
valves can be implemented with a wide variety of triggering
temperatures through the choice of a concrete glass ampoule and/or
a corresponding fluid filling.
[0021] Other advantages and features of the inventive safety valve
are derived from the following description of the exemplary
embodiments depicted in the accompanying figures, in which
[0022] FIG. 1 shows a view of an inventive safety valve
[0023] FIG. 2a shows a sectional view along line A-A in FIG. 1 of
the safety valve in a first variant in an enlarged diagram;
[0024] FIG. 2b shows a detail according to the area labeled as B in
FIG. 2a on an enlarged scale
[0025] FIG. 3a shows a sectional diagram of the second variant of
an inventive safety valve shown along line A-A in FIG. 1
[0026] FIG. 3b shows in an enlarged diagram the area of the safety
valve labeled as B in FIG. 3a according to this embodiment
[0027] FIG. 4a shows a sectional diagram of a third embodiment of
an inventive safety valve along line A-A in FIG. 1 and
[0028] FIG. 4b shows an enlarged diagram of the area of the safety
valve according to this embodiment, labeled as B in FIG. 4a.
[0029] The figures are drawn schematically and not true to scale.
The same or similar element are provided with the same or similar
reference numerals in the figures.
[0030] FIG. 1 shows an inventive safety valve 100 in one possible
embodiment. The inventive valve 100 is formed in a housing 1. In
the interior of the housing the safety valve 100 has an overflow
duct 2 in the area shown at the bottom of FIG. 1, said overflow
duct being optionally connected to a corresponding tapping duct of
a compressed gas container. To do so, the housing 1 is provided
with an outside thread 6 in the area of the overflow duct with
which it can be screwed into a corresponding inside thread of a
connection of a compressed gas container and/or a compressed gas
valve. For screw mounting, a hex-head screw 5 on which a commercial
wrench may be used is provided on the housing 1 of the safety valve
100. On its end opposite the outside thread 6 the housing 1 is
sealed with a screwed in abutment 7. In a middle section, the
housing 1 has outflow openings 4 in the form of boreholes leading
radially into the housing.
[0031] FIGS. 2a and 2b, 3a and 3b show two different possible
embodiment variants of an inventive safety valve in sectional
diagrams according to sectional line A-A in FIG. 1. The embodiment
variants shown here differ only in the internal design of the
safety valve 100 but not from the outside, so the diagram in FIG. 1
is equally valid for both variants.
[0032] First the variant shown in FIGS. 2a and 2b will be described
with reference to these figures. These figures show again clearly
the overflow duct 2, as formed in the interior of the housing 1 of
the safety valve 100. A closure body 20 is provided in the overflow
duct 2. The closure body 20 is wedge shaped in cross section,
namely V-shaped in this example and is rotationally symmetrical
about a longitudinal axis. The closure body 20 abuts on the one
hand against a plate spring 11 which is supported on a shoulder 14
in the overflow duct 2.
[0033] On its side facing away from the plate spring 11, the
closure body 20 has a sealing surface 28 with a concave shape,
having a larger diameter at its widest than the O ring 9. The
smallest diameter of the sealing surface is smaller than the
diameter of the O ring 9 so the closure body with its sealing
surface 28 extends into the O ring 9 in a wedge shape. The concave
shape of the sealing surface 28 is adapted in its curvature to the
curvature of the sealing surfaces of the O ring 9 at least in some
areas so that an optimal seal can be achieved between the sealing
surface 28 of the closure body and the O ring 9. The O ring 9 rests
on a second plate spring 21 which is in turn supported on a
shoulder 24 in the overflow duct 2.
[0034] On the side of the plate spring 11 opposite the closure body
20, the under side of a fluid-filled glass ampoule 8 is in contact
with the plate spring. The fluid-filled glass ampoule 8 is
supported at its other end in a blind hole in the abutment 7
axially opposite the closure body 20.
[0035] The diagram in FIGS. 2a and 2b shows the standby position of
the closure body 20 in which it reliably seals the overflow duct 2
with respect to an outlet duct 3 in cooperation with the O ring 9,
which opens into the outflow openings 4. The shape of the closure
body 20 shown in this exemplary embodiment produces an especially
good seal of the overflow duct 2 in the standby position of the
closure body 20.
[0036] The plate spring 11 situated between the closure body 20 and
the glass ampoule 8 on the shoulder 14 in the overflow duct 2
exerts a spring force on the glass ampoule 8 in the axial
direction, directed at the abutment 7.
[0037] The plate spring 11 can in particular absorb through
deformation a stress occurring due to the difference in thermal
expansion of the metal parts of the housing 1, closure body 20,
abutment 7 and glass ampoule 8 [sic; 8] thereby preventing
premature rupture of the glass ampoule 8 occurring due to such
difference in thermal expansion, and thus premature triggering of
the safety valve 100.
[0038] Due to the arrangement of the plate spring 11 on the side
opposite the abutment 7, no forces resulting from the gas pressure
need be absorbed by the glass ampule 8. In addition, stresses
created due to differences in thermal expansion can be absorbed by
the plate spring 21, thus resulting in a further improvement in the
compensation of such forces and/or stresses and thus ensuring even
more reliably that the safety valve 100 will not cause mechanical
stresses due to differences in thermal expansion coefficient of the
glass material of the glass ampoule 8 and the material of the
housing 1 of the abutment 7 and/or the closure body 20.
[0039] In assembling this variant of the inventive safety valve
100, the glass ampoule 8 is clamped between the plate spring 11 and
the abutment 7 with a defined force in that the abutment 7 is
bolted to the housing 1 of the safety valve 11 at a predetermined
torque with the glass ampule 8 inserted.
[0040] FIGS. 3a and 3b show a sectional of a second exemplary
embodiment of an inventive safety valve 100 which is again shown in
its outside view in FIG. 1.
[0041] This exemplary embodiment corresponds in essential design
details to the exemplary embodiment shown in FIGS. 2a and 2b so
that reference can be made to the discussion of FIGS. 2a and 2b
with regard to the description of this exemplary embodiment.
[0042] In contrast with the exemplary embodiment described
previously, the variant shown here has only one plate spring 21,
which is arranged on the side of the closure body 20 facing the
overflow duct 2. A plate spring 14 arranged on the side of the
closure body 20 facing the glass ampoule 8 as provided in the
exemplary embodiment according to FIGS. 2a and 2b is omitted in the
present exemplary embodiment.
[0043] Another particular detail of the exemplary embodiment
illustrates in FIGS. 3a and 3b is that in addition to the closure
body 20 an intermediate body 29 is arranged between the former and
the glass ampoule 8. The exemplary embodiment illustrated in FIGS.
3a and 3b may of course also be modified in the sense that the
intermediate body 29 is omitted and/or becomes part of the closure
body 20.
[0044] Finally, FIGS. 4a and 4b illustrate a third embodiment
variant of an inventive safety valve 100. In this variant, the
closure body 15 introduced into the overflow duct 2 is shaped
somewhat differently in comparison with the closure bodies 20 in
the previous embodiment variants. This closure body 15 also has
essentially a wedge shape with an inclined sealing surface 28 with
which it presses the O ring 9 radially against the wall of the
overflow duct 2, forming a seal. Instead of the plate springs 21
arranged on the side of the closure body 20 opposite the glass
ampoule 8 in the preceding exemplary embodiments, the O ring 9 in
this exemplary embodiment is supported on an essentially rigid disk
12 which the closure body 15 protrudes with a protrusion 17 through
in a central opening. The O ring 9 is also secured by a ring 13,
which is in contact with the closure body 15 and O ring 9.
[0045] The spring action on the glass ampoule 8 in the direction of
the abutment 7 is exerted in this exemplary embodiment exclusively
by the plate spring 10 which rests on a shoulder 16 formed in the
overflow duct 2 and abuts against the glass ampoule 8 on one side
and the closure body 15 on the other side.
[0046] In the function of prestressing the glass ampoule 8 and
triggering of the safety element 100, this variant also operates as
described above with regard to the exemplary embodiment according
to the FIGS. 2a and 2b so that reference can be made to this
description in this regard.
[0047] It is clear from the exemplary embodiments illustrated here
that the spring element (as at least one plate spring in the
exemplary embodiments) can be arranged on the side of the closure
body facing the burst body as well as on the side of the closure
body facing the overflow duct as well as on both sides at the same
time.
[0048] In the embodiment variant show in FIGS. 2a-2b the plate
spring 11 which is in direct contact with the side of the glass
ampoule 8 opposite the abutment 7 offers another advantage. Namely
it additionally serve as another "sealing element" that prevents
soiling of the overflow duct 2 whish is on the other side of same
due to particle, foreign substances, gases or the like penetrating
through the outflow openings 4. This "seal" also prevents corrosion
in the area on the side of the plate spring 11 opposite the glass
ampoule 8 in that it also prevents corrosive media from penetrating
into this area. The same thing is also true of the exemplary
embodiment according to FIGS. 4a and 4b. Again here, the plate
spring 10 has the additional effect described above.
[0049] All the embodiment variants of the safety valve 100 shown
here are triggered at a predetermined temperature (at which
expansion of the fluid in the glass ampoule 8 causes the latter to
rupture). At the triggering temperature, the glass ampoule 8
ruptures, so that the closure body 15 and/or 20 is displaced in the
direction of the outlet duct 3 due to the pressure of the
compressed gas applied to the overflow duct 2 and thus a connection
is created between the overflow duct 2, the outlet duct 3 and/or
the outflow openings 4.
[0050] In the exemplary embodiments, the thermal triggering unit is
additionally formed by the abutment 7, the glass ampoule 8, the O
ring 9, the closure body 15 and/or 20 and the plate spring(s) 10,
11 and/or 21 and in the case of the exemplary embodiment
illustrated in FIGS. 3a and 3b, it is additionally formed by the
intermediate body 29 and in the case of the exemplary embodiment
illustrated in FIGS. 4a through 4b it is additionally formed by the
ring 13 and the disk 12.
[0051] The preceding description of the exemplary embodiments has
shown clearly again the advantages of the inventive insertion of a
spring element, in particular a plate spring into a safety valve
100. In addition, the advantages of the inventive form of the
closure body are apparent.
LIST OF REFERENCE NUMERALS
[0052] 1 Housing [0053] 2 Overflow duct [0054] 3 Outlet duct [0055]
4 Outflow openings [0056] 5 Hex-head screw [0057] 6 Outside thread
[0058] 7 Abutment [0059] 8 Glass ampoule [0060] 9 O ring [0061] 10
Plate spring [0062] 11 Plate spring [0063] 12 Disk [0064] 13 Ring
[0065] 14 Shoulder [0066] 15 Closure body [0067] 16 Shoulder [0068]
17 Protrusion [0069] 20 Closure body [0070] 21 Plate spring [0071]
24 Shoulder [0072] 28 Sealing surface [0073] 29 Intermediate body
[0074] 100 Safety valve
* * * * *