Field of application
[0001] The present invention refers to a safety device for a pressurized gas tank and to
a method for operating such safety device, according to the preamble of the respective
independent claims.
[0002] The present safety device is intended to be installed at the containment wall (also
known with the technical term skirt) of a tank containing pressurized gas, and in
particular fuel gas for motor vehicles, in order to evacuate a gas flow in the presence
of breakdowns, accidents or critical environmental conditions, i.e. when the pressure
and/or the temperature of the gas contained inside the tank exceed pre-established
threshold values.
[0003] The safety device and its operating method, object of the present invention, are
therefore situated in the field of production of safety devices for pressurized gas
tanks installed in plants for feeding fuel into motor vehicles and in particular in
the industrial field of production of safety devices for over-pressure and over-temperature.
State of the art
[0004] As is known, the plants for feeding fuel gas into motor vehicles (such as cars or
trucks) comprise a tank for storing fuel gas, normally liquefied petroleum gas (LPG),
normally fixed to the support chassis of the motor vehicle.
[0005] Normally, the tank for storing fuel gas is hydraulically connected to the feed manifold
of the internal combustion engine of the motor vehicle and therefore its filling and
the physical characteristics of the gas contained therein are subjected to numerous
laws in order to ensure the safety of the people on board the motor vehicle itself
and of the people located in the vicinity thereof.
[0006] More in detail, one of the applicable laws provides that the tank be filled at most
up to 80% of its maximum capacity, in order to prevent an excessive increase of the
pressure of the gas contained therein.
[0007] LPG physical behavior generally or at least in first approximation follows the known
laws of the state of ideal gases. The equation of state of the ideal gases provides
that pV = nRT, in which
p is the internal pressure of the gas,
V is the volume occupied by the gas at the pressure
p, n is the substance quantity,
R is the gas constant and
T is the gas temperature. By applying such general formula to the LPG contained in
a tank, in first approximation, it is understood that with the increase of the temperature
of the gas contained in the tank, also the internal pressure thereof increases proportionally
(with proportionality constant equal to
nR/
V)
.
[0008] Therefore, in the case of prolonged exposure of the tank to a heat source, the latter
can increase its temperature until it makes the gas contained therein reach critical
pressure values, which could compromise the structural integrity of the tank itself.
In particular, the currently applicable law provides that the maximum internal pressure
of the LPG in a tank does not exceed 27 bar.
[0009] For the purpose of evacuating the gas contained in a tank following the attainment
of the threshold value of its internal pressure, it has for some time been known in
the field of production of safety devices to provide for a valve for the over-pressure,
adapted to make the gas evacuate when the latter reaches the pressure threshold value.
Such valve is normally positioned at an opening made on the skirt of the tank and
is provided with a shutter placed to close the opening. This valve of known type is
also provided with a containment jacket within which a spring is positioned, placed
in abutment on one side against the shutter which is forced to close the opening,
and on the other side against the internal wall of the containment jacket, which therefore
acts as abutment against the elastic stress exerted by the spring.
[0010] With the increase of the pressure inside the tank, the gas pushes the shutter of
the valve with always-greater force, such valve shutter forced to be moved away from
the opening made on the skirt of the tank, overcoming the elastic force exerted by
the spring. Once the shutter is moved from the opening, the gas is free to evacuate
from the tank, and therefore the pressure within the latter decreases. A valve for
the over-pressure of known type, considered in brief herein, is described in the patent
US 1,686,875.
[0011] A further safety device is known from
EP1521022A1.
[0012] The same currently applicable law provides that the evacuation of the gas contained
inside the tank be provided even in the case of only over-temperature. Indeed, if
the tank is only partially filled, e.g. for a small part of the volume thereof, it
can happen that - in the case of a fire or a prolonged exposure to a heat source -
the thermal agitation of the gas molecules due to the heating is not sufficient for
increasing the pressure inside the tank until it is brought above the aforesaid threshold
value of 27 bar. Nevertheless, for example in the presence of a fire, it is still
important to evacuate the gas contained in the tank regardless of its internal pressure,
since it could explode. In particular, the law provides that upon reaching the threshold
temperature of 120°C, the gas must be quickly released to the atmosphere.
[0013] For the purpose of evacuating the gas contained in a tank following the attainment
of the threshold value of its temperature, an over-temperature valve has for some
time been known in the field of production of safety devices, such valve for the over-temperature
positioned at an opening made on the skirt of the tank and provided with a shutter
placed to close such opening. The valve for over-temperature of known type is provided
with a containment jacket within which an element made of fusible material is positioned,
substantially placed to block the shutter which is therefore forced to maintain the
opening made on the skirt closed. More in detail, the fusible material element is
composed of an eutectic metal alloy that melts at low temperatures and is selected
so that it fluidifies at the aforesaid threshold temperature.
[0014] With the increase of the temperature of the skirt of the tank, the temperature melts
the fusible element which keeps the valve shutter blocked, and such shutter is forced
to be moved away from the opening made on the valve body fixed to the skirt of the
tank, by means of the action of the gas, which is at a greater pressure than the atmospheric
pressure and therefore is able to exert a force on the shutter in order to exit from
the tank. An example of a valve for the over-temperature of known type, considered
in brief herein, is described in the patent
US 2,859,758.
[0015] Normally, both the valves for over-pressure and over-temperature of known type discussed
herein up to now are mounted in parallel on the skirt of the tanks for the storage
of liquefied petroleum gas, in order to ensure the safety required by the current
applicable law in all situations.
[0016] Currently, several types of safety devices are present on the market, which are provided
with a single support body on which the aforesaid over-pressure and over-temperature
valves are mounted; such valves affect the same opening made on the skirt of the tank
and are in the technical jargon of the field termed "multi-valves".
[0017] One example of a safety device provided with both the over-pressure and over-temperature
valves is described in the patent
IT 1315578 on behalf of the same applicant.
[0018] The safety device of known type and termed "multi-valve", described briefly above,
has in practice proven that it does not lack drawbacks.
[0019] A first drawback lies in the fact that such known safety device is bulky, since each
of the valves is provided with an autonomous gas discharge channel and therefore two
separate internal ramifications of the device itself must be provided.
[0020] A further drawback of such known safety device lies in the fact that the mounting
thereof at the skirt of the tank is long and arduous and therefore requires long operating
times which translates into high mounting costs.
[0021] A further drawback of such known safety device lies in the fact that for its production,
it is necessary to make a metallic support body of considerable mass in order to be
able to obtain the provided seats of the various members and the provided passages
for the gas. This involves the use of a considerable quantity of metallic material,
in particular brass, whose cost is high and such to negatively affect the overall
cost of production of the safety device.
[0022] The patent
EP 1521022 describes a safety valve of known type which comprises a spring shutter in order
to prevent over-pressures within the container, and a fusible element which is interposed
between the spring of the shutter and a fixed cover of the valve, and is susceptible
of melting (above a specific temperature) in a manner such to completely unload the
spring, leaving the shutter free to be moved, such that it can be brought into open
position by the gas inside the tank in order to allow the exit thereof in case of
over-temperature.
[0023] Also the latter finding of known type has reliability and efficiency optimization
limits, since it is in particular necessary that the spring of the shutter be completely
unloaded in order to allow the latter to be opened in over-temperature conditions.
Presentation of the invention
[0024] The main object of the present invention is therefore that of overcoming the drawbacks
manifested by the above-described prior art solutions by providing a safety device
for a pressurized gas tank, which ensures optimal safety according to the current
applicable laws.
[0025] Another object of the present invention is to provide a safety device for a pressurized
gas tank, which is easy and quick to install.
[0026] Further object of the present invention is to provide a safety device for a pressurized
gas tank, which maintains its mechanical characteristics unchanged over time and ensures
constant and optimal safety.
[0027] Further object of the present invention is to provide a safety device for a pressurized
gas tank, which is inexpensive and easy to make.
[0028] Further object of the present invention is to provide a method for operating a safety
device for a pressurized gas tank, which allows obtaining high safety and reliability.
Brief description of the drawings
[0029] The technical characteristics of the finding, according to the aforesaid objects,
can be clearly seen in the contents of the below-reported claims and the advantages
thereof will be more evident in the following detailed description, made with reference
to the enclosed drawings which represent a merely exemplifying and non-limiting embodiment
of the invention, in which:
- figure 1 shows a top axonometric view of the safety device, object of the present
invention;
- figure 2 shows a top plan view of the safety device, object of the present invention;
- figure 3 shows a sectional view, made along the trace A-A of figure 2, of the safety
device, object of the present invention, in the closed configuration thereof;
- figure 4 shows a sectional view, made along the trace A-A of figure 2, of the safety
device, object of the present invention, in a first open configuration thereof, due
to the over-pressure;
- figure 5 shows a sectional view, made along the trace A-A of figure 2, of the safety
device, object of the present invention, in a second open configuration thereof, due
to the over-temperature;
- figure 6 shows a top plan view of a shutter of the safety device, object of the present
invention;
- figure 7 shows a sectional view, made along the trace B-B of figure 6, of the shutter
of the safety device, object of the present invention;
- figure 8 shows an exploded axonometric view of the shutter of the safety device, object
of the present invention.
Detailed description of a preferred embodiment
[0030] With reference to the set of drawings, reference number 1 overall indicates the safety
device for a pressurized gas tank, object of the present invention.
[0031] The safety device 1 for a pressurized gas tank, object of the present invention,
is intended to be installed on a containment wall of a tank, for example a fuel gas
tank, not illustrated since it is well known to the man skilled in the art. Such containment
wall defines the internal volume of the tank itself, in which the gas is intended
to be stored.
[0032] Advantageously, the device 1 is intended to be installed on a tank containing liquefied
petroleum gas (LPG) on board a motor vehicle, such as the tank of a car or truck in
order to ensure a protection against over-pressure and/or over-temperature of the
gas which can be encountered in case of irregularities, such as accidents or breakdowns.
[0033] More in detail, the safety device 1, object of the present invention, is intended
to make the gas evacuate quickly from the tank if the pressure and/or the temperature
reach predetermined threshold values, in order to prevent structural yielding of the
containment wall of the tank with consequent explosion.
[0034] The safety device 1 for a pressurized gas tank comprises a support body 2 adapted
to be fixed to the containment wall of a tank intended to contain pressurized gas.
For such purpose, the support body 2 preferably comprises a perimeter flange 3 intended
to be fixed to the wall of the tank by means of fixing means such as screws. The support
body 2 internally delimits an evacuation channel 4, which is intended to place the
internal volume of the tank in flow connection with the external environment, in order
to allow the quick evacuation of the gas in case of over-pressure and/or over-temperature,
as described in detail hereinbelow.
[0035] Preferably, the support body 2 is made of metallic material, e.g. hot-molded brass.
[0036] The safety device 1 also comprises a shutter 7 placed to intercept the evacuation
channel 4 and extended along a main extension axis Y thereof.
[0037] Advantageously, the main extension axis Y is substantially orthogonal to the containment
wall of the pressurized gas tank, once the device is installed on the tank.
[0038] The shutter 7 is movable between a closed position (illustrated in the enclosed figure
3), in which it is placed to close the evacuation channel 4 by hydraulically separating
the interior of the tank from the external environment, and an open position (illustrated
in the enclosed figure 4 in the case of over-pressure and in the enclosed figure 5
in the case of over-temperature), in which the shutter 7 at least partially frees
the evacuation channel 4, allowing the pressurized gas contained in the tank to exit
towards the external environment.
[0039] The shutter 7 of the safety device 1, object of the present invention, is provided
with a shaft 10, which is extended along the main extension axis Y and is at least
partially inserted within the evacuation channel 4. The shutter 7 is also provided
with a closure head 8 placed at a first end 27 of the shaft 10 directed towards the
external environment and with a spring 9 wound around the shaft 10 and interposed
between the support body 2 and a contrast element 11 fixed to a second end 23 of the
shaft 10 directed inside the tank. The spring 9 is adapted to force the closure head
8 of the shutter 7 into the closed position.
[0040] In particular, the spring 9 is compressed between the contrast element 11 (preferably
placed outside the evacuation channel 4) and an abutment portion of the support body
2 arranged on an inner face thereof intended, during use, to be directed towards the
interior of the tank.
[0041] Advantageously, the contrast element 11 of the safety device 1, object of the present
invention, is provided with a threaded through hole 24 associated by means of coupling
of screw-nut screw type to the second end 23 of the shaft 10, which has at least one
threaded portion.
[0042] Preferably, the shaft 10 of the shutter 7 is placed to traverse the evacuation channel
4 with its first end 27 positioned outside the evacuation channel 4 (in particular
on an external side of the support body 2 intended, during use, to be directed towards
the external environment) and with its second end also placed outside the evacuation
channel 4 (in particular on an internal side of the support body 2 intended, during
use, to be directed towards the interior of the tank).
[0043] The safety device 1 also comprises a fusible element 14 susceptible of melting in
case of over-temperature, i.e. upon reaching a predetermined threshold value, in particular
equal to 120°C in accordance with the currently applicable laws, in order to allow
the quick evacuation of the gas contained in the tank and prevent the possibility
of tank explosion.
[0044] Advantageously, the fusible element 14 is made of a eutectic alloy (i.e. a metal
alloy whose melting temperature is lower than the melting temperature of the single
components that form such alloy), and in particular it is preferably made of a lead
and bismuth alloy, whose melting temperature is about 120°C.
[0045] Otherwise, the fusible element 14 can for example be made of an eutectic alloy of
indium and tin, which nevertheless is well-known to be more costly than the aforesaid
lead and bismuth alloy.
[0046] Of course, the material that composes the fusible element 14 can be of any type,
selected based on the desired melting temperature, without departing from the protective
scope of the present patent.
[0047] According to the idea underlying the present invention, the closure head 8 of the
shutter 7 of the safety device 1 comprises a hollow sleeve 17 provided with a through
hole 16 slidably traversed by the shaft 10, and internally delimits a housing space
15 in which the fusible element 14 is housed.
[0048] The shutter 7 also comprises a retention element 21 fixed to the shaft 10 at its
first end 27 directed towards the external environment. Such retention element 21
is pulled by the spring 9 against the fusible element 14, in order to force the closure
head 8 (and in particular the hollow sleeve 17) to obstruct the evacuation channel
4.
[0049] More in detail, the spring 9 - by abutting against the support body 2 - acts on the
contrast element 11 fixed to the shaft 10 at its second end 23, forcing the same contrast
element 11 and the entire shaft 10 therewith towards the internal volume of the tank
along the main extension axis Y.
[0050] In this manner, the retention element 21, fixed to the first end 27 of the shaft
10, is also pulled along the axis Y (of the evacuation channel 4 and also of the shaft
10) towards the interior of the tank (i.e. downward with reference to the enclosed
figures 3-5), forcing the same retention element 21 of the shutter 7 against the fusible
element 14. In this manner, the shutter 7 (and in particular the hollow sleeve 17)
is forced into the aforesaid closed position, obstructing the evacuation channel 4.
[0051] Advantageously, the fusible element 14 is arranged between a bottom wall 28 of the
housing space 15 of the hollow sleeve 17 and the retention element 21 fixed to the
shaft 10 of the shutter 7, in a manner such that, in particular, the retention element
21 (following the above-described action of the spring 9) abuts against the fusible
element 14 which in turn is in abutment against the bottom wall 28 of the hollow sleeve
17.
[0052] Advantageously, the force exerted by the spring 9 is such to maintain the shutter
7 in the closed position during the normal operation of the pressurized gas tank and
such to compress and move the shutter 7 into the open position if the pressure of
the gas inside the tank itself exceeds a predetermined threshold pressure value, e.g.
27 bar, as prescribed by the currently applicable laws.
[0053] In accordance with the preferred embodiment illustrated in the enclosed figures,
the closure head 8 of the shutter 7 comprises a first annular gasket 25 mechanically
associated with the hollow sleeve 17.
[0054] More in detail, the hollow sleeve 17 is provided with an annular seat 31 in which
the first annular gasket 25 directed towards the evacuation channel 4 is engaged and
housed and preferably retained by means of a shaped washer 32 housed within the annular
seat 31.
[0055] Preferably, the evacuation channel 4 has an annular extension around the shaft 10
and is delimited by an evacuation mouth 18 on which the annular gasket 25 of the closure
head 8 is sealingly placed with the shutter 7 in the closed position, pulled by the
elastic force of the spring 9.
[0056] Advantageously, the support body 2 comprises a cup-shaped portion 26 with at least
one window, preferably transversely open with respect to the main extension axis Y,
in order to allow the passage of the gas from the tank towards the evacuation channel
4 when the shutter 7 is in open position.
[0057] Advantageously, the closure head 8 of the shutter 7 comprises a second annular gasket
12 mechanically associated with the shaft 10, housed within the housing space 15 of
the hollow sleeve 17 and preferably mounted interposed between the fusible element
14 and an internal mouth 13 which at least partially delimits the through hole 16
in which the shaft 10 of the shutter 7 is slidably inserted.
[0058] Preferably, between the second gasket 12 and the fusible element 14, a metallic annular
portion 5 is interposed that is adapted to protect the gasket 12 following the melting
of the fusible element 14 itself, in case of over-temperature. Such second annular
gasket 12 is sealingly placed on the internal mouth 13 of the hollow sleeve 17 made
along the through hole 16.
[0059] Such metallic annular portion 5 can be obtained in a single body with the hollow
sleeve 17 via turning or with a separate metal washer.
[0060] Preferably, the first annular gasket 25 and the second annular gasket 12 are made
of rubber.
[0061] In accordance with the preferred embodiment illustrated in the enclosed figures,
the shaft 10 is provided with an end stop element 19, which interacts with an abutment
portion 20 of the support body 2, with the shutter 7 in the open position.
[0062] In operation, when the fusible element 14 collapses, melting due to the exceeding
of the threshold temperature, the shaft 10 is free to slide for an operating travel
29 (figure 3) with respect to the support body 2 until it abuts against the abutment
portion 20 (figure 5) thereof.
[0063] More in detail, the operating travel 29 is equal to the distance measured along the
main extension axis Y when the shutter 7 is in the closed position, between the end
stop element 19 of the shaft 10 and the abutment portion 20 of the support body 2.
[0064] Advantageously, the end stop element 19 of the shaft 10 comprises a radially projecting
annular shoulder, which is susceptible of abutting against a step of the abutment
portion 20 of the support body 2, placed to intercept the end stop element 19 when
the shutter 7 is moved from the closed position to the open position.
[0065] Advantageously, the height of the fusible element 14 along the main extension axis
Y is greater than the operating travel 29, i.e. than the distance between the end
stop element 19 and the abutment portion 20 when the shutter 7 is in closed position
(and the fusible element 14 is not melted), in order to allow the exit of the gas
from the tank even in the case of only over-temperature, as described in detail hereinbelow.
[0066] The gas that is located inside the tank is always at a pressure higher than that
of the external environment but it can have a pressure lower than the threshold pressure.
In practice, if the tank is nearly empty, following a prolonged exposure of the latter
to a heat source, the internal pressure of the gas might not reach the threshold value
for compressing the spring 9 in order to move the shutter 7 from the closed position
to the open position; nevertheless, the provided temperature threshold might be exceeded,
such that there is the risk of tank explosion in this situation.
[0067] When the fusible element 14 is collapsed, being melted due to the exceeding of the
threshold temperature, the shaft 10 is maintained by the action of the spring 9 with
its end stop element 19 in abutment against the abutment portion 20 of the support
body 2.
[0068] The gas nevertheless continues to push - from inside the tank towards the external
environment - the closure head 8 (and in particular its hollow sleeve 17), which is
slidably mounted on the shaft 10, freeing a passage between the same closure head
8 and the evacuation mouth 18 of the evacuation channel 4.
[0069] More clearly, the pressure of the gas forces the closure head 8 (and in particular
the hollow sleeve 17) to slide with respect to the shaft 10, for a height equal to
the difference between the height of the fusible element 14 and the operating travel
29 of the shaft 10, until the retention element 21 receives in abutment the bottom
wall 28 of the hollow sleeve 17. In particular, in accordance with the example illustrated
in the enclosed figures, the retention element 21 receives in abutment the metallic
annular portion 5 (as illustrated in the enclosed figure 5).
[0070] Advantageously, the through hole 16 of the hollow sleeve 17 is provided with a cross
section with respect to the main extension axis Y such to allow the passage of the
retention element 21 during the movement of the closure head 8 (and in particular
of the hollow sleeve 17) between the closed position and the open position (with the
fusible element 14 collapsed).
[0071] Therefore, in the case of only over-temperature, for the purpose of moving the shutter
7 from the closed position to the open position, an evacuation slit 30 (figure 5)
is defined between the closure head 8 and the evacuation channel 4, and in particular
between the first gasket 25 and the evacuation mouth 18. Such evacuation slit 30 remains
open even if the pressure of the gas inside the tank is lower than the threshold value,
and the gas is free to quickly exit, ensuring the quick emptying of the tank even
in the case of only over-temperature.
[0072] Preferably, the fusible element 14 has substantially annular form and is placed inside
the housing space 15 and in particular is placed around the shaft 10 of the shutter
7.
[0073] Advantageously, the closure head 8 is provided with passage openings 22 (illustrated
in figure 6) which are defined between the retention element 21 and the hollow sleeve
17 of the closure head 8 of the shutter 7.
[0074] In operation, the passage openings 22 are susceptible of being traversed by the liquefied
fusible element 14 once the threshold temperature has been reached. The material which
composes the fusible element 14 is forced to exit through the passage openings 22
from the hollow sleeve 17 towards the external environment due to the action of the
spring 9 which pushes the retention element towards the bottom wall 28 and by action
of the pressure exerted by the gas that pushes the hollow sleeve 17 towards the external
environment.
[0075] Preferably, the retention element 21 comprises a nut screwed on the shaft 10 at its
first end 27, which is provided with at least one externally threaded portion.
[0076] In this manner, the passage openings 22 are defined between the external perimeter
walls of the nut of the retention element 21 and the internal face of the hollow sleeve
17, which is preferably of tubular form.
[0077] Also forming the object of the present invention is a method for operating the safety
device 1 described up to now; for the sake of simplicity, the already-indicated reference
numbers will be maintained hereinbelow.
[0078] The method for operating the device alternately or sequentially provides for a step
of inoperative operation, i.e. when the shutter 7 is placed to intercept and close
the evacuation channel 4 without over-pressure and over-temperature events being verified;
a step of intervention for over-pressure, in which as reported above the pressure
of the gas overcomes the contrast force of the spring 9, causing the exit of the gas,
and a step of intervention for over-temperature in which - in the presence or absence
of over-pressure - the melting of the fusible element 14 takes place.
[0079] The claimed method described hereinbelow refers to a step of intervention for over-temperature
in the absence of over-pressure.
[0080] The method for operating the safety device for a pressurized gas tank, object of
the present invention, therefore comprises in case of over-temperature and in the
absence of over-pressure, initially a step of melting the fusible element 14, which
is housed in the housing space 15 of the closure head 8. Such step is intended to
be verified upon reaching a corresponding threshold value for the temperature of the
fusible element 14.
[0081] Following the melting step, the fusible element 14 is found in liquid form or at
least semi-liquid form and therefore is no longer able to act as a mechanical abutment
for the retention element 21 pulled by the elastic action of the spring 9 and pushed
by the pressure of the gas.
[0082] An emptying step then follows, in which the fusible element 14 exits from the hollow
sleeve 17 of the closure head 8, by means of the force imparted by said spring 9 against
the fusible element 14 imparted through the retention element 21, at least partially
freeing the housing space 15.
[0083] Advantageously, the material which composes the fusible element 14 exits from the
hollow sleeve 17, traversing the passage openings 22 which are defined between the
retention element 21 and the hollow sleeve 17 itself.
[0084] The method for operating the safety device 1, object of the present invention, also
comprises a consequent and successive step of releasing the spring 9, in which the
spring 9 is expanded, forcing the shaft 10 to slide with respect to the hollow sleeve
17 until the end stop element 19 of the shaft 10 abuts against the abutment portion
20 of the support body 2.
[0085] Advantageously, following the step of releasing the spring 9, the shaft 10 of the
shutter 7 is blocked with its end stop element 19 in abutment against the abutment
portion 20 of the support body 2.
[0086] The operating method also comprises an opening step in which the shutter 7 reaches
the open position, by means of the movement of the closure head 8. Such movement is
susceptible of being actuated by the pressure of the gas contained inside the tank,
which is adapted to move the closure head 8 itself towards the external environment,
sliding on the shaft 10, at least partially freeing the evacuation channel 4 in order
to allow the pressurized gas to exit from the tank.
[0087] More in detail, following the opening step, the first annular gasket 25 is released
from the abutment against the evacuation mouth 18, between which a substantially annular
evacuation slit 30 is defined that remains open even in the case of only over-temperature
with pressure inside the tank lower than the threshold value.
[0088] Advantageously, in the step of releasing the spring 9, the shaft 10 slides with respect
to the closure head 8 along the operating travel 29 equal to the distance along the
main extension axis Y between the end stop element 19 and the abutment portion 20
with the shutter 7 in closed position.
[0089] The operating travel 29 traveled by the shaft 10 during such release step is smaller
than the height of the fusible element 14 and therefore the retention element 21 is
not yet abutted against the bottom wall 28 of the hollow sleeve 17, and in the particular
case illustrated in the enclosed figures the retention element 21 is not yet abutted
against the metallic annular portion 5 housed within the housing space 15, when the
end stop element 19 abuts against the abutment portion 20.
[0090] Advantageously, in the opening step, the closure head 8 (and in particular the hollow
sleeve 17) slides with respect to the shaft 10 by a length equal to the difference
between the height of the fusible element 14 along the main extension axis Y and the
operating travel 29, until the bottom wall 28 of the hollow sleeve 17 abuts against
the retention element 21.
[0091] More in detail, the sum of the lengths traveled respectively by the shaft 10 in the
step of releasing the spring 9 and by the closure head 8 during the opening step is
equal to the height of the fusible element 14 along the main extension axis Y.
[0092] The safety device 1 and its operating method, both the object of the present invention,
therefore ensure a quick evacuation of the gas contained inside the tank in case of
over-pressure and in case of over-temperature. In particular, following the opening
step, the evacuation slit 30 is defined between the evacuation mouth 18 of the support
body 2 and the closure head 8 of the shutter 7 which allows the evacuation of the
gas from the tank even in the case of only over-temperature with an internal pressure
of the tank lower than the threshold value.
[0093] In particular, the claimed configuration of the spring 19, of the shaft 10, of the
hollow sleeve 17 and of the fusible element 14 allows, in case of over-temperature,
releasing the hollow sleeve 17 from the shaft 10 (in particular also without completely
unloading the spring 19), in a manner such that it is sufficient to lift only the
hollow sleeve 17 in order to allow the opening of the shutter 7.
[0094] The invention thus conceived therefore attains the pre-established objects.
1. Safety device (1) for a pressurized gas tank, comprising:
- a support body (2) intended to be fixed to the containment wall of a tank, and internally
delimiting an evacuation channel (4), which is intended to place the internal volume
of the tank in flow connection with the external environment;
- a shutter (7) placed to intercept said evacuation channel (4), extended along a
main extension axis (Y) and movable between:
- a closed position, in which said shutter (7) is placed to close said evacuation
channel (4) in order to hydraulically separate the interior of the tank from the external
environment;
- an open position, in which said shutter (7) at least partially frees said evacuation
channel (4), in order to allow the pressurized gas contained in the tank to exit towards
the external environment;
said shutter (7) being provided with:
- a shaft (10) extended along said main extension axis (Y) and at least partially
inserted within said evacuation channel (4);
- a closure head (8) placed at a first end (27) of said shaft (10) intended to be
directed towards the external environment;
- a spring (9) wound around said shaft (10) and interposed between said support body
(2) and a contrast element (11) fixed to a second end (23) of said shaft (10) intended
to be directed inside the tank, said spring (9) being adapted to force the closure
head (8) of said shutter (7) into said closed position;
- a fusible element (14);
said safety device (1) being
characterized in that:
- said closure head (8) comprises a hollow sleeve (17) provided with a through hole
(16) slidably traversed by said shaft (10) and delimiting a housing space (15) in
which said fusible element (14) is housed;
- said shutter (7) comprises a retention element (21), which is fixed to said shaft
(10) at said first end (27), and is pulled by said spring (9) against said fusible
element (14).
2. Safety device (1) for a pressurized gas tank according to claim 1, characterized in that said shaft (10) is provided with an end stop element (19), which is adapted to interact
with an abutment portion (20) of said support body (2), with said fusible element
(14) fused.
3. Safety device (1) for a pressurized gas tank according to claim 2, characterized in that the height of said fusible element (14) along said main extension axis (Y) is greater
than the distance between said end stop element (19) and said abutment portion (20)
with said shutter (7) in closed position.
4. Safety device (1) for a pressurized gas tank according to any one of the preceding
claims, characterized in that said closure head (8) of said shutter (7) comprises a first annular gasket (25) mechanically
associated with said hollow sleeve (17); said evacuation channel (4) having an annular
extension around said shaft (10) and being delimited by an evacuation mouth (18) on
which said annular gasket (25) of said closure head (8) is sealingly placed, with
said shutter (7) in closed position.
5. Safety device (1) for a pressurized gas tank according to any one of the preceding
claims, characterized in that said closure head (8) of said shutter (7) comprises a second annular gasket (12)
mechanically associated with said shaft (10); said second annular gasket (12) being
sealingly placed on an internal mouth (13) of said hollow sleeve (17) made along said
through hole (16).
6. Safety device (1) for a pressurized gas tank according to any one of the preceding
claims, characterized in that said fusible element (14) has substantially annular form and is placed inside said
housing space (15) and around said shaft (10) of said shutter (7).
7. Safety device (1) for a pressurized gas tank according to any one of the preceding
claims, characterized in that said closure head (8) is provided with passage openings (22) which are defined between
said retention element (21) and said hollow sleeve (17) of said closure head (8).
8. Method for operating a safety device (1) for a pressurized gas tank according to claim
1, comprising the following operating steps:
- a step of melting said fusible element (14) housed in the housing space (15) of
said closure head (8), once the threshold temperature value for the temperature of
said fusible element (14) has been reached;
- an emptying step, in which said fusible element (14) exits from said hollow sleeve
(17) of said closure head (8), by means of the force exerted by said spring (9) and
by the pressure of the gas against said fusible element (14) through said retention
element (21), at least partially freeing said housing space (15);
- a step of releasing said spring (9), in which said spring (9) is expanded, forcing
said shaft (10) to slide with respect to said hollow sleeve (17) until an end stop
element (19) of said shaft (10) abuts against an abutment portion (20) of said support
body (2);
- a consequent opening step, in which said shutter (7) reaches said open position,
by means of the movement of said closure head (8) due to the pressure of the gas contained
inside the tank, which moves said closure head (8) towards the external environment,
sliding on said shaft (10), at least partially freeing said evacuation channel (4)
in order to allow the pressurized gas to exit from the tank.
9. Method for operating a safety device for a pressurized gas tank according to claim
8, characterized in that in said release step, said shaft (10) slides with respect to said closure head (8)
for an operating travel (29) equal to the distance along said main extension axis
(Y) between said end stop element (19) and said abutment portion (20) with said shutter
(7) in closed position;
in said opening step, said closure head (8) sliding with respect to said shaft (10)
by a length equal to the difference between the height of said fusible element (14)
along said main extension axis (Y) and said operating travel (29).
10. Method for operating a safety device for a pressurized gas tank according to one of
the claims 8 or 9, characterized in that following said opening step, an evacuation slit (30) is defined between said evacuation
mouth (18) and said closure head (8) which allows the evacuation of the gas from the
tank in case of over-temperature and at pressure lower than a threshold pressure value.
1. Sicherheitsvorrichtung (1) für einen Druckgastank, der Folgendes umfasst:
- einen Trägerkörper (2), der dazu bestimmt ist, an der Umgebungswand eines Tanks
befestigt zu werden und in seinem Inneren einen Abführkanal (4) umfasst, der dazu
bestimmt ist, das Innenvolumen des Tanks strömungstechnisch mit der Außenumgebung
in Verbindung zu setzen;
- einen zum Absperren des genannten Abführkanals (4) positionierten, entlang einer
vorherrschenden Verlaufsachse (Y) verlaufenden Verschluss (7), der bewegt werden kann
zwischen:
- einer Schließposition, in der der genannte Verschluss (7) als Absperrung des genannten
Abführkanals (4) positioniert ist, um das Innere des Tanks hydraulisch von der Außenumgebung
zu trennen;
- einer Öffnungsposition, in der der genannte Verschluss (7) den genannten Abführkanal
(4) zumindest teilweise freigibt, um es dem in dem Tank enthaltenen unter Druck stehenden
Gas zu gestatten, in die Außenumgebung zu entweichen;
wobei der genannte Verschluss (7) mit Folgenden ausgestattet ist:
- mit einer entlang der genannten vorherrschenden Verlaufsachse (Y) verlaufenden und
mindestens teilweise in das Innere des genannten Abführkanals (4) eingesetzten Welle
(10);
- mit einem auf einem ersten Ende (27) der genannten Welle (10) positionierten Verschlusskopf
(8), der dazu bestimmt ist, in Richtung Außenumgebung gerichtet zu sein;
- eine um die genannte Welle (10) gewickelte und zwischen dem genannten Trägerkörper
(2) und einem an einem zweiten Ende (23) der genannten Welle (10) befestigtem Kontrastelement
(11) eingesetzte Feder (9), die dazu bestimmt ist, im Inneren des Tanks gedreht zu
werden, wobei die genannte Feder (9) geeignet ist, den Verschlusskopf (8) des genannten
Verschlusses (7) in die genannte Schließposition zu bringen;
- mit einem Schmelzsicherungselement (14);
wobei die genannte Sicherheitsvorrichtung (1)
dadurch gekennzeichnet ist, dass:
- der genannte Verschlusskopf (8) eine mit einer durchgehenden Öffnung (16) versehene
hohle Muffe (17) umfasst, die gleitend von der genannten Welle (10) überquert wird
und einen Unterbringungsraum (15) begrenzt, in dem das genannte Schmelzsicherungselement
(14) untergebracht ist;
- der genannte Verschluss (7) ein Rückhalteelement (21) umfasst, das an der genannten
Welle (10) auf dem genannten ersten Ende (27) befestigt und von der genannten Feder
(9) gegen das genannte Schmelzsicherungselement (14) gezogen wird.
2. Sicherheitsvorrichtung (1) für einen Druckgastank nach Anspruch 1, dadurch gekennzeichnet, dass die genannte Welle (10) mit einem Endschalterelement (19) ausgestattet ist, das geeignet
ist, bei durchgebranntem Schmelzsicherungselement (14) mit einem Anschlagabschnitt
(20) des genannten Trägerkörpers (2) zu interagieren.
3. Sicherheitsvorrichtung (1) für einen Druckgastank nach Anspruch 2, dadurch gekennzeichnet, dass die Höhe des genannten Schmelzsicherungselements (14) entlang der genannten vorherrschenden
Verlaufsachse (Y) bei genanntem Verschluss (7) in Schließposition größer ist als der
Abstand zwischen dem genannten Endschalterelement (19) und dem genannten Anschlagsabschnitt
(20).
4. Sicherheitsvorrichtung (1) für einen Druckgastank nach einem beliebigen der vorangegangenen
Ansprüche, dadurch gekennzeichnet, dass der genannte Verschlusskopf (8) des genannten Verschlusses (7) eine mechanisch mit
der hohlen Muffe (17) verbundene erste ringförmige Dichtung (25) umfasst; wobei der
genannte Abführkanal (4) einen ringförmigen Verlauf um die genannte Welle (10) aufweist
und von einer Abführöffnung (18) begrenzt wird, auf der die genannte ringförmige Dichtung
(25) des genannten Verschlusskopfes (8) bei genanntem Verschluss (7) in Schließposition
abdichtend positioniert ist.
5. Sicherheitsvorrichtung (1) für einen Druckgastank nach einem beliebigen der vorangegangenen
Ansprüche, dadurch gekennzeichnet, dass der genannte Verschlusskopf (8) des genannten Verschlusses (7) eine mechanisch mit
der genannten Welle (10) verbundene zweite ringförmige Dichtung (12) umfasst. wobei
die genannte zweite ringförmige Dichtung (12) abdichtend auf einer entlang der genannten
durchgehenden Öffnung (16) befindlichen inneren Mündung (13) der genannten hohlen
Muffe (17) positioniert ist.
6. Sicherheitsvorrichtung (1) für einen Druckgastank nach einem beliebigen der vorangegangenen
Ansprüche, dadurch gekennzeichnet, dass das genannte Schmelzsicherungselement (14) im Wesentlichen ringförmig ist und im
Inneren des genannten Unterbringungsraums (15) und um die genannte Welle (10) des
genannten Verschlusses (7) angeordnet ist.
7. Sicherheitsvorrichtung (1) für einen Druckgastank nach einem beliebigen der vorangegangenen
Ansprüche, dadurch gekennzeichnet, dass der genannte Verschlusskopf (8) mit Durchgangszwischenräumen (22) ausgestattet, die
zwischen dem genannten Rückhalteelement (21) und der genannten hohlen Muffe (17) des
genannten Verschlusskopfes (8) definiert bleiben.
8. Verfahren zum Betreiben einer Sicherheitsvorrichtung (1) für einen Druckgastank nach
Anspruch 1, das die folgenden Arbeitsschritte umfasst:
- einen Schritt des Abschmelzens des in dem Unterbringungsraum (15) des genannten
Verschlusskopfes (8) untergebrachten genannten Schmelzsicherungselements (14), sobald
der Temperaturschwellenwert für die Temperatur des genannten Schmelzsicherungselements
(14) erreicht wird;
- einen Schritt des Abführens, in dem das genannte Schmelzsicherungselement (14) aus
der genannten hohlen Muffe (17) des genannten Verschlusskopfes (8) durch die von der
genannten Feder (9) ausgeübte Kraft und den Druck des Gases gegen das genannte Schmelzsicherungselement
(14) über das genannte Rückhalteelement (21) austritt und so den genannten Unterbringungsraum
(15) mindestens teilweise freigibt;
- einen Schritt des Lösens der genannten Feder (9), bei dem die genannte Feder (9)
sich ausdehnt und so die genannte Welle (10) dazu bringt, sich im Verhältnis zu der
genannten hohlen Muffe (17) zu verschieben, bis ein Endschalterelement (19) der genannten
Welle (10) gegen einen Anschlagabschnitt (20) des genannten Trägerkörpers (2) anschlägt;
- einen nachfolgenden Öffnungsschritt, bei dem der genannte Verschluss (7) die genannte
Öffnungsposition durch Bewegen des genannten Verschlusskopfes (8) durch den Druck
des im Inneren des Tanks enthaltenen Gases erreicht, der den genannten Verschlusskopf
(8) in Richtung Außenumgebung bewegt, indem er auf der genannten Welle (10) verschoben
wird und den genannten Abführkanal (4) mindestens teilweise freigibt, um es dem unter
Druck stehenden Gas zu gestatten, aus dem Tank zu entweichen.
9. Verfahren zum Betreiben einer Sicherheitsvorrichtung für einen Druckgastank nach Anspruch
8, dadurch gekennzeichnet, dass bei dem genannten Schritt des Lösens die genannte Welle (10) im Verhältnis zu dem
genannten Verschlusskopf (8) um einen Arbeitshub (29) verschoben wird, der dem Abstand
entlang der genannten vorherrschenden Verlaufsachse (Y) zwischen dem genannten Endschalterelement
(19) und dem genannten Anschlagsabschnitt (20) bei genanntem Verschluss (7) in Schließposition
entspricht;
wobei bei dem genannten Öffnungsschritt der Verschlusskopf (8) im Verhältnis zu der
genannten Welle (10) um eine Länge verschoben wird, die der Differenz zwischen der
Höhe des genannten Schmelzsicherungselements (14) entlang der genannten vorherrschenden
Verlaufsachse (Y) und dem genannten Arbeitshub (29) entspricht.
10. Verfahren zum Betreiben einer Sicherheitsvorrichtung für einen Druckgastank nach einem
der Ansprüche 8 oder 9, dadurch gekennzeichnet, dass im Anschluss an den genannten Öffnungsschritt ein Abführschlitz (30) zwischen der
genannten Abführmündung (18) und dem genannten Verschlusskopf (8) verbleibt, der das
Abführen des Gases aus dem Tank im Fall von Übertemperatur und bei einem Druck unter
einem Schwellenwert des Drucks gestattet.
1. Dispositif de sécurité (1) pour un réservoir de gaz sous pression comprenant :
- un corps de support (2) destiné à être fixé à la paroi de confinement d'un réservoir
et délimitant intérieurement un chemin d'évacuation (4) qui est destiné à établir
un raccord entre le flux provenant de l'espace interne du réservoir et l'environnement
externe ;
- un obturateur (7) placé en position d'interception par rapport audit canal d'évacuation
(4) et s'étendant le long d'un axe de développement prévalent (Y) pouvant se déplacer
entre :
- une position de fermeture dans laquelle ledit obturateur (7) vient à fermer ledit
canal d'évacuation (4) afin de séparer hydrauliquement l'intérieur du réservoir de
l'environnement externe ;
- une position d'ouverture dans laquelle l'obturateur (7) libère au moins partiellement
le canal d'évacuation (4) afin de permettre au gaz sous pression contenu dans le réservoir
de sortir vers l'environnement externe ;
ledit obturateur (7) étant équipé de :
- un arbre (10) s'étendant le long dudit axe de développement prévalent (Y) et au
moins partiellement inséré à l'intérieur dudit canal d'évacuation (4) ;
- une tête de fermeture (8) disposée à une première extrémité (27) dudit arbre (10)
et destinée à être tournée vers l'environnement externe ;
- un ressort (9) enroulé autour de l'arbre (10) et s'interposant entre ledit corps
de support (2) et un élément de contraste (11) fixé à une deuxième extrémité (23)
dudit arbre (10) destinée à être tournée vers l'intérieur du réservoir, ledit ressort
(9) étant à même de forcer la tête de fermeture (8) dudit obturateur (7) en position
de fermeture ;
- un élément fusible (14) ;
ledit dispositif de sécurité (1) étant
caractérisé en ce que :
- ladite tête de fermeture (8) comporte un manchon creux (17) avec un trou passant
(16) traversé par coulissement par l'arbre (10) et délimitant un espace de logement
(15) dans lequel ledit élément fusible (14) vient se loger ;
- ledit obturateur (7) comporte un élément de retenue (21) qui est fixé audit arbre
(10) au niveau de ladite première extrémité (27) et qui est tiré contre ledit élément
fusible (14) par ledit ressort (9).
2. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon la revendication
1, caractérisé en ce que ledit arbre (10) est doté d'un élément de fin de course (19) qui est en capacité
d'interagir avec une partie de butée (20) du corps de support (2) avec le fusible
(14) fondu.
3. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon la revendication
2, caractérisé en ce que la hauteur de l'élément fusible (14) le long de l'axe de développement prévalent
(Y) est supérieure à la distance entre l'élément de fin de course (19) et la partie
de butée (20) avec l'obturateur (7) en position de fermeture.
4. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon l'une quelconque
des revendications précédentes, caractérisé en ce que la tête de fermeture (8) de l'obturateur (7) contient une première garniture annulaire
(25) associée mécaniquement au manchon creux (17) ; le canal d'évacuation (4) présentant
un développement annulaire autour de l'arbre (10) et étant délimité par une bouche
d'évacuation (18) sur laquelle la garniture annulaire (25) est étanchéisée par rapport
à la tête de fermeture (8) avec l'obturateur (7) en position de fermeture.
5. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon l'une quelconque
des revendications précédentes, caractérisé en ce que ladite tête de fermeture (8) dudit obturateur (7) comporte une deuxième garniture
annulaire (12) associée mécaniquement audit arbre (10) ; ladite deuxième garniture
annulaire (12) étant disposée de façon étanche sur une bouche interne (13) dudit manchon
creux (17) réalisée le long dudit trou passant (16).
6. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon l'une quelconque
des revendications précédentes, caractérisé en ce que ledit élément fusible (14) est de forme essentiellement annulaire et est placé à
l'intérieur dudit espace de logement (15) et autour dudit arbre (10) dudit obturateur
(7).
7. Dispositif de sécurité (1) pour un réservoir de gaz sous pression selon l'une quelconque
des revendications précédentes, caractérisé en ce que ladite tête de fermeture (8) est dotée de lumières de passage (22) qui sont définies
entre ledit élément de retenue (21) et ledit manchon creux (17) de ladite tête de
fermeture (8).
8. Procédé de fonctionnement d'un dispositif de sécurité (1) pour un réservoir de gaz
sous pression selon la revendication 1, comprenant les phases opérationnelles suivantes
:
- une phase de fusion dudit élément fusible (14) disposé dans l'espace de logement
(15) de ladite tête de fermeture (8) lorsque la valeur limite de température a été
atteinte pour la température dudit élément fusible (14) ;
- une phase de vidange durant laquelle ledit élément fusible (14) sort dudit manchon
creux (17) de ladite tête de fermeture (8) grâce à une force imprimée par ledit ressort
(9) et par la pression du gaz contre ledit élément fusible (14) à travers ledit élément
de retenue (21), en libérant au moins partiellement ledit espace de logement (15)
;
- une phase de desserrage dudit ressort (9) durant laquelle ledit ressort (9) se détend
en forçant ledit arbre (10) à glisser par rapport audit manchon creux (17) jusqu'à
ce qu'un élément de fin de course (19) dudit arbre (10) vienne en butée contre une
partie de butée (20) dudit corps de support (2) ;
- une phase d'ouverture consécutive, dans laquelle ledit obturateur (7) atteint ladite
position d'ouverture par déplacement de ladite tête de fermeture (8) sous la pression
du gaz contenu dans le réservoir, pression qui déplace ladite tête de fermeture (8)
en direction de l'environnement externe en glissant le long dudit arbre (10) en libérant
au moins partiellement ledit canal d'évacuation (4) afin de permettre au gaz sous
pression de sortir du réservoir.
9. Procédé de fonctionnement d'un dispositif de sécurité pour un réservoir de gaz sous
pression selon la revendication 8, caractérisé en ce que, dans ladite phase de desserrage, ledit arbre (10) glisse par rapport à ladite tête
de fermeture (8) sur une course opérationnelle (29) égale à la distance le long dudit
axe de développement prévalent (Y) entre ledit élément de fin de course (19) et ladite
portion de butée (20) avec ledit obturateur (7) en position de fermeture ;
lors de ladite phase d'ouverture, ladite tête de fermeture (8) glissant par rapport
audit arbre (10) sur une longueur égale à la différence entre la hauteur dudit élément
fusible (14) le long dudit axe de développement prévalent (Y) et ladite course opérationnelle
(29).
10. Procédé de fonctionnement d'un dispositif de sécurité pour un réservoir de gaz sous
pression selon l'une des revendications 8 ou 9, caractérisé en ce que suite à la phase d'ouverture une fissure d'évacuation (30) est définie entre ladite
bouche d'évacuation (18) et ladite tête de fermeture (8) qui permet au gaz de s'échapper
du réservoir en cas de surtempérature et d'une pression plus basse qu'une certaine
valeur limite de pression.