U.S. patent number 3,664,430 [Application Number 05/078,440] was granted by the patent office on 1972-05-23 for electrical monitor for fire extinguisher.
This patent grant is currently assigned to HTL Industries, Inc.. Invention is credited to Abdul N. Sitabkhan.
United States Patent |
3,664,430 |
Sitabkhan |
May 23, 1972 |
ELECTRICAL MONITOR FOR FIRE EXTINGUISHER
Abstract
Covers a fire extinguisher for use on aircraft. The fire
extinguisher includes a container equipped with mechanism for
signalling the pilot in the cockpit in the event that the fire
extinguishing fluid has been discharged through the safety relief
valve of the container. The fire extinguisher is equipped with a
thermally responsive material, which is positioned on or adjacent
to the surface of the container and is electrically conductive. The
material melts when its temperature reaches a predetermined value.
The material is wired to the cockpit of the aircraft and the
circuitry includes an indicating device, such as a lamp, to
indicate instantly to the pilot that the fire extinguisher has been
discharged and that, therefore, the fire extinguisher is not
suitable for extinguishing a fire.
Inventors: |
Sitabkhan; Abdul N. (El Monte,
CA) |
Assignee: |
HTL Industries, Inc. (Monrovia,
CA)
|
Family
ID: |
22144039 |
Appl.
No.: |
05/078,440 |
Filed: |
October 6, 1970 |
Current U.S.
Class: |
169/23;
169/42 |
Current CPC
Class: |
A62C
37/50 (20130101) |
Current International
Class: |
A62C
37/50 (20060101); A62C 37/00 (20060101); A62c
039/02 (); A62c 037/30 () |
Field of
Search: |
;169/23,42,2,26
;340/227.1 ;116/5,106 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Grant; Edwin D.
Claims
What is claimed is:
1. The combination of a sealed container housing a fire
extinguishing fluid, a thermally responsive, electrically
conductive material positioned at or adjacent to the periphery of
the container, said material being responsive to the ambient
temperature and being melted upon reaching a predetermined
temperature to release the fire extinguishing fluid, and indicating
means electrically connected to said material to promptly respond
to the melting of said material.
2. The combination of claim 1 in which the thermally responsive
material is conductively connected to the indicating means over a
continuous circuit which is opened upon the melting of said
material.
3. The combination of claim 1 which includes a visual indicator
electrically connected to the thermally responsive material and
electrically disconnected from said material when the material is
melted.
4. The combination of a sealed container housing a fire
extinguishing fluid, a thermally responsive, electrically
conductive material positioned at or adjacent to the periphery of
the container, said material, when melted, releasing said fluid, a
transistor having base, emitter and collector electrodes, said
material being conductively connected between the base and emitter
electrodes, a source or voltage, an indicator connected in series
between the collector electrode and the source of voltage, and a
resistor connected between the base electrode and the terminal
common to the indicator and the source of voltage, the indicator
monitoring the electrical continuity of said material, whereby the
status of the fluid within the housing is observable.
5. The combination of claim 4 in which the thermally responsive
material will be melted either in response to a rise in the
pressure within the sealed container to a predetermined value or a
rise in the ambient temperature to a different predetermined
value.
6. Apparatus for continually monitoring the condition of a fire
extinguisher having a container housing a fire extinguishing fluid,
comprising a safety valve on the surface of the container, a
thermally responsive, electrically conductive material inserted in
said safety valve, and an indicating mechanism wired to two
separated points of said material so that said material provides
continuity in the circuit to the indicating mechanism, whereby said
mechanism will indicate the continuity of said material, said
material having a melting point at which the fire extinguishing
fluid will be discharged from the container through said safety
valve.
7. Apparatus according to claim 6 in which the thermally responsive
material will melt at a temperature which corresponds to a maximum
allowable pressure within the container.
8. The combination of a sealed container using a fire extinguishing
fluid, a safety valve positioned adjacent to the surface of said
container, a conductive material positioned in said safety valve,
said material being normally continuous electrically but being
severed and rendered discontinuous in response to pressure within
the container exceeding a predetermined value or when the ambient
temperature exceeds a predetermined value, and electrical circuitry
connected in series with said material and indicating the severance
of said material, the fire extinguishing fluid being released from
said container upon the severance of said material.
9. The combination of claim 8 in which the conductive material is
in the form of a thermally responsive, electrically conductive
substance which is severed upon the ambient tempera-ture reaching a
predetermined value.
10. The combination of claim 8 in which the conductive material is
in the form of a conductive tape which is severed in response to an
abnormal pressure within the container.
11. The combination of a sealed container housing a fire
extinguishing fluid, a safety valve adjacent to the surface of said
container, a pressure sensitive disc made of conductive material
and positioned within said safety valve, and an electrical circuit
connected to said disc so that said disc forms a serial element of
said circuit, said disc being punctured in response to a rise in
the pressure of said container above a predetermined value, so that
the fire extinguishing fluid may be discharged through the opening
provided by said punctured disc, whereby the electrical circuit
will continuously monitor the condition of the fire extinguishing
fluid within said container.
Description
This invention relates to fire extinguishers, especially those
which are provided for use on aircraft, and to apparatus for
instantly determining whether or not the fire extinguisher has
discharged its fire extinguishing fluid through its safety relief
valve so that the fire extinguisher is no longer capable of
extinguishing a fire.
Presently available fire extinguishers suitable for use on aircraft
may employ a safety discharge valve equipped with a so-called
"burst" disc or with a material set to melt at a predetermined
temperature, the disc or the material to be located at or near the
periphery of the container of the fire extinguisher. Any increase
in the ambient temperature causes a corresponding increase in the
pressure of the fire extinguishing fluid within the container. When
the pressure within the fire extinguisher should exceed a
predetermined value, the disc will be ruptured or severed by the
increased pressure to allow the extinguisher to discharge the fire
extinguishing fluid or other contents of the container. Likewise,
when the temperature of the fire extinguisher becomes abnormally
high due, for example, to exposure to the sun or to any other high
temperature medium, the rise in temperature of the contents of the
extinguisher will melt the thermally responsive material to allow
the container to discharge the fire extinguishing fluid therefrom.
In either case, should the internal conditions within the
extinguisher exceed the predetermined values at which the disc will
be ruptured or severed, or at which the thermally responsive
material will melt, the contents of the container of the
extinguisher will, therefore, be discharged. However, the loss of
the fluid contents may occur at a relatively slow rate and be
hardly perceptible. Unless this condition is promptly detected and
corrected, the leaky extinguisher may have no useful protective
purpose aboard the craft. This, naturally, presents a hazardous
condition, both for the passengers and crew as well as for the
aircraft and is especially hazardous during flight.
A presently available fire extinguisher for use on aircraft
embodies an "overboard discharge line" for observing whether or not
the fire extinguisher has been discharged. Such equipment usually
includes a pipe line interconnection to the relief fitting of the
fire extinguisher with a colored disc mounted on the "skin" of the
aircraft. Upon an abnormal rise in temperature, the contents of the
fire extinguisher will undergo a corresponding rise in the pressure
within the extinguisher, so that the contents of the extinguisher
will be released through the safety valve and freely transmitted
through the discharge line to cause the colored disc to be
expelled. Unfortunately, the colored disc is remote from the
cockpit and is therefore not visible to the pilot of the aircraft.
It would be undesirable and indeed dangerous to have the contents
of the fire extinguisher discharged into the cockpit if the
discharge line were instead connected between the fire extinguisher
and the cockpit. The only way presently available to detect the
discharged condition of the fire extinguisher is by having an
officer walk around the craft after it has landed at its assigned
airport, and spot the absence of the discharge disc. If the colored
discharge disc is found in its normal position on the skin of the
aircraft where it is readily observable because of its color, the
officer will be satisfied that the fire extinguisher remains in
good working condition. If there should be a leak in the discharge
line extending to the colored disc, then the inoperativeness of the
fire extinguisher would not be detected because the colored disc
will remain in its normal condition in its normal place. On the
other hand, if the discharge port is open because the colored disc
is absent, the officer may observe the absence and then alert the
ground maintenance staff that the specified fire extinguisher needs
repair or replacement. This will delay the operation of an aircraft
on its next leg of the trip. The inoperativeness of the fire
extinguisher may have occurred near the beginning of the prior trip
and unfortunately was unknown to the crew. Such situations should
be avoided and can be minimized or avoided by the present
invention.
In order to overcome the present unsatisfactory condition created
by having an overboard discharge line extending to a colored disc
which is observable only from a grounded position, the present
invention is provided to make available simple and inexpensive
mechanism whereby the condition of the fire extinguisher may be
automatically and promptly indicated to the pilot in the cockpit
while the craft remains in flight and even verified before the
flight is initiated. This may be accomplished, for example, by
employing a thermally responsive material or a blowout disc in or
near the safety relief valve of the fire extinguisher. The thermal
device may be any suitable thermally responsive material provided
either in the safety valve of the container or on or in an
additional fitting mounted on the safety valve, the thermal
material serving as a sensing device. The blowout disc may be any
suitable burst disc provided for the safety valve of the container
or an additional disc designed to blow at a predetermined pressure.
Obviously, the burst disc may be ruptured by the exiting fluids as
the pressure rises due to sufficiently elevated ambient
temperatures. Likewise, the thermally responsive material may be so
arranged that it will melt sufficiently at a predetermined
temperature to allow the contents of the fire extinguisher to be
discharged upon a predetermined rise in the ambient temperature.
Obviously, the blowout disc is to be ruptured or severed when the
fluid is discharged through the safety valve. The thermally
responsive material or the the blowout disc, whichever is employed,
should preferably be electrically conductive and be connected
through an electrical circuit extending into the cockpit, the
interconnected circuit including an indicating device, such as a
lamp. When the thermally responsive material has been partially or
fully melted and hence the contents of the fire extinguisher
discharged through the gap provided by the melted material, or when
the blown disc has been ruptured and the fluid contents discharged
through the safety valve, the indicating device located in the
cockpit will promptly indicate to the pilot that the fire
extinguisher is not in operative condition and requires attention.
If there are ten or more fire extinguishers in an aircraft, such as
a 747 Boeing aircraft, there may be 10 different indicating devices
positioned in the cockpit, each associated with a selected one of
the fire extinguishers, so that the pilot may at all times observe
the conditions of all the fire extinguishers on the aircraft. Such
an arrangement will obviate any requirement for observing from the
ground the physical condition of the several discs that may be
associated with the skin of the aircraft. Inspection of all fire
extinguishers is available to all members of the crew at all times
while in the cockpit. Should a failure develop in any of the fire
extinguishers, the pilot may relay a message to the next landing
point to have the fire extinguisher repaired or refilled or
replaced and this can be accomplished promptly upon the landing of
the aircraft and save much valuable time.
Accordingly, it is one of the principal objects of this invention
to provide mechanism for promptly determining the operative
condition of any or all of the fire extinguishers associated with
an aircraft or other vehicles while it remains in motion.
Another of the objects of this invention is to provide indicating
apparatus for a fire extinguisher, the indicating apparatus to
include a temperature responsive fusible material or a blowout disc
mounted on or near or in the safety discharge valve of the fire
extinguisher container and conductively connected to an indicating
device, such as a lamp, so that, upon the partial or complete
melting of the fusible material or the rupture of the blowout disc,
the indicating device will be operated or rendered operative and
will indicate instantly and continuously that the fire extinguisher
is not suitable for rendering fire extinguishing service.
This invention together with its other objects and features will be
better and more clearly understood from the following more complete
description and explanation when read in connection with the
accompanying drawing in which:
FIG. 1 illustrates a cross-sectional view of one form of
extinguisher assembly that may be used in the practice of this
invention, this figure illustrating a container which utilizes a
thermally responsive material for its safety relief.
FIG. 2 shows a circuit diagram for a single fire extinguisher.
FIG. 3 shows a schematic wiring diagram for two fire extinguishers
equipped according to this invention where a single cockpit
indication is desired.
FIG. 4 illustrates a schematic circuit drawing for three or a
plurality of fire extinguishers arranged according to this
invention.
FIG. 5 illustrates a fitting for a fire extinguisher's container
suitable for the practice of the invention, the fitting providing
for the employment of an overboard discharge line if such line is
necessary or desirable to prevent over-pressurization of the
compartment in which the extinguisher is mounted.
FIG. 6 schematically illustrates a cross-sectional view of a
portion of a safety relief valve employing a blowout disc which may
be wired to the cockpit or other indicating point.
FIG. 7 schematically illustrates a cross-sectional view of a
segment of a safety relief valve having therein a blowout disc to
which a thermally responsive material is affixed.
The same or similar reference characters will be employed
throughout the drawing, wherever they may occur, to designate the
same or similar parts.
Referring to the drawing, and referring especially to FIG. 1 of the
drawing, there is shown, for illustration, a metallic or plastic
container CN constituting a housing for receiving and encasing fire
extinguishing and other materials, usually in the form of liquids
or gases or both. The container CN may embody a plurality of
mounting or supporting brackets, each designated U, along with
appropriate hardware, such as bolts and nuts (not shown) for
retaining and holding the container CN on appropriately shaped
stationary brackets (not shown) within an airplane or within a
compartment of an airplane or other vehicle. A plurality of like
containers, such as CN, may be affixed to different segments of an
airplane and, if desired, one container may be located adjacent to
and associated with an engine of the airplane and, if there is more
than one engine, a separate container may be associated with each
engine.
The container CN may have two main valves, one a filler valve FV
which includes a thermally responsive material for its safety
relief and the other a discharge valve DV. The filler valve may be
employed to receive, through an opening therein, the liquids or
gases or both to be inserted into the container CN and maintained
at a suitable pressure, perhaps between 600 and 2,700 psi. The
discharge valve DV may be employed for discharging the contents of
container CN upon the breakage of a disc therein; or the discharge
valve DV may enclose a housing which mechanically holds a sealing
pug in position. Breakage may be accomplished by a cartridge type
of device (not shown).
Another form of container suitable for fire extinguishing service,
to which the features of the present invention may be applied, is
shown and described in an application of J.R. Fiero, Ser. No.
735,093, filed June 6, 1968, now U.S. Pat. No. 3,552,495 and
assigned to the assignee of the present application. The container
CN may be hermetically sealed, and its valves FV and DV may also be
hermetically sealed, to prevent the leakage of the pressurized
contents of container CN. When sealed, the nozzle of the discharge
valve DV should preferably be pointed at the object, i.e., the
engine, to be protected against fire. The valve DV may be equipped
with a cartridge of appropriate explosive material and wired to the
central point or to the cockpit where a switch may be operated by a
member of the crew to initiate a shock wave, or a plurality of
shock waves, to rupture the enclosed disc or the sealing lug so
that the contents of the container CN may be discharged to suppress
or extinguish a fire. As described and explained in the above
specified patent application, the materials to be inserted into the
container CN may include freon 1301, nitrogen gas to charge or
super-charge the freon, and an inert gas, such as helium, to serve
as a non-odorous tracer to be detectable by, for example, a mass
spectograph.
The filler valve FV includes a frangible disc (not shown) for
functioning as a relief valve. The valve FV may include or house
additionally, in accordance with this invention, a blowout disc,
which is electrically conductive, into which two separate insulated
conductors W1 and W2 are inserted. The ends of the conductors W1
and W2 are spaced from each other so that the conductive disc alone
provides the operative conductive path between the two conductors.
For an alternative additional illustration, FIG. 1 shows, instead
of a blowout disc, a thermally responsive conductive material TH
into which the two conductors W1 and W2 are inserted for connection
to indicating equipment to be described.
FIG. 2 shows an alarm circuit which may be interconnected between
the terminals of the thermally responsive material TH of FIG. 1,
shown also in FIG. 2, and the cockpit of the aircraft (or to the
conductive blowout disc described with respect to FIG. 1). The
device TH may or may not be part of the container CN, being
positioned at or near or in the safety valve of the container,
while a lamp LP or other indicator may be located in the cockpit.
The device TH may be connected between the base b and the emitter e
of a transistor TR, while the lamp LP may be connected between the
collector c and the negative or grounded terminal of a battery BT
or other source of dc voltage. A resistor RZ may be connected
between the base b and the positive terminal of battery BT.
The device TH allows a small current to flow in the path
established via resistor RZ to battery BT. This continuous loop
holds transistor TR in a non-conductive state. However, when the
device the TH partially or completely melted or ruptured, due to a
rise in the ambient temperature, the transistor TR will become
conductive. A substantial current will then flow from battery BT
through the emitter and collector electrodes e and c and lamp LP,
illuminating lamp LP. This lamp LP, when lighted, will be readily
visible to the pilot and other members of the crew. The lamp LP
will remain lighted until the affected (or discharged) container is
replaced or refilled and a new sensor element TH is attached.
The device TH may be any appropriate fusible material which is
normally conductive electrically, such as cerrobend. Such a
material may yield and begin melting at a temperature of about
205.degree.-220.degree. F. Such a temperature will melt the
material sufficiently so as to break open the circuit between
conductors W1 and W2.
The pressure of the fluids within container CN, although maintained
at an assigned value when the container is filled and sealed, rises
as the ambient temperature increases. In order to protect the fire
extinguisher against inordinate internal pressure increases due to
inordinate ambient temperature rises, the safety valve on the
container CN relieves the inordinate pressure by discharging the
contents of the container. The thermally responsive material TH or
the blow-out disc, will be melted or ruptured at or above a
predetermined pressure reaching the safety valve. This breaks the
previously established loop between conductors W1 and W2. The break
in the loop allows the transistor to become conductive and lamp LP
will be lighted. These two events will occur substantially
simultaneously, and the crew will be instantly apprised of the
unavailability of the particular fire extinguisher. The pilot may
then radio the next landing field to inform its maintenance crew
that the fire extinguisher needs repair or replacement.
Although the lamp LP is a visible indicator, it will be apparent
that a buzzer or other audible indicator may be substituted
therefor or, if desired, connected in series with the visible
indicator LP. In any case, the audible indicator, such as a buzzer,
will indicate audibly to the pilot that a non-operative condition
associated with the corresponding container has developed and that
container CN cannot be relied upon for fire extinguishing
service.
In the arrangement of FIG. 2 the transistor TR may be an RCA 40361
transistor and the source may be a 28 volt DC power supply. The
resister RZ may be a 47 Kohm, 1/2 watt device.
FIG. 3 schematically illustrates a circuit arrangement shown for
the use of the invention in connection with a pair of fire
extinguishers. The devices TH1 and TH2, whether they be thermally
responsive and conductive devices or conductive blowout discs,
would be associated with independent fire extinguisher containers,
such as container CN of FIG. 1. In the FIG. 3 arrangement, however,
the two devices TH1 and TH2 are connected in series with each other
in a path which includes the base b and the emitter e of the
transistor TR. The lamp LP is connected between the collector c of
the transistor TR and the point common to the resistors RZ1 and
RZ2. The latter resistors are also connected in series with each
other between the base b of transistor TR and the positive terminal
of the source of direct voltage BT, the negative terminal of which
is grounded. A Zener diode is bridged across the circuit of
resistor RZ.
The two elements TH1 and TH2 together provide a continuous loop to
maintain transistor TR in a non-conductive state, but this state is
maintained only as long as both devices TH1 and TH2 remain intact,
i.e. neither device has been melted or ruptured by the exiting
fluid. Under these conditions, the flow of current from the source
BT will be minimal and insufficient to illuminate lamp LP. On the
other hand, when either of the containers, with which the devices
TH1 and TH2 are associated, become subject to rather high
temperature, i.e. temperatures exceeding a predetermined magnitude,
the thermal device which is subjected to the extraordinary
temperature will be melted or ruptured. Upon the removal of the
disabled device TH the lamp LP will be fed sufficient current to
illuminate it, thereby apprising the pilot in the cockpit that one
of the two containers with which the devices TH1 and TH2 are
associated has failed and therefore lost its fire extinguishing
ability. The Zener diode ZD will serve to restrict the voltage that
may be applied to the path between the base b and emitter e of
transistor TR.
The FIG. 3 arrangement employs a single indicating device, i.e.,
lamp LP, the signify a loss of fire extinguishing fluid from one
two supplemental containers. These containers may be located
adjacent to each other near a single engine, for example.
FIG. 4 schematically illustrates another modification in which
individual lamps LP1, LP2 and LP3 will correspond to individual
fire extinguishers which have the devices TH1, TH2 and TH3
associated with them. Each element, such as TH1, is associated with
its individual transistor, such as TR1. Each element TH1 maintains
the corresponding transistor in a non-conductive state. Thus, if
the element TH1 is melted by the excessive temperature or ruptured
by the pressurized exiting fluids so that the associated container
is disabled, the transistor TR1 will become conductive, thereby
causing lamp LP1 to become illuminated. Likewise, lamps LP2 and LP3
will become illuminated when these elements TH2 and TH3 become
melted or ruptured due to excessive thermal conditions in the
vicinity of the respective fire extinguisher containers. Obviously,
additional parallel circuits, each including a device such as TH1,
a transistor such as TR1, and a lamp such as LP1 may be joined to
the overall arrangement to increase the scope of coverage available
to the pilot in observing the condition of the fire extinguishers
throughout the aircraft. Each lamp will signify to the observer the
particular fire extinguisher that happens to be rendered
useless.
This invention will eliminate the so-called overboard discharge
lines now conventionally used in connection with aircraft fire
extinguishers. Consequently, there will be no requirement for
blow-out discs at the terminal end of the overboard discharge
lines. Furthermore, it will be unnecessary to have an officer
inspect the various blow-out discs upon reaching an airport to
observe, from the ground, the condition of the several fire
extinguishers on board. Instead, the cockpit service people can
observe and monitor the condition of all of the fire extinguisher
equipments throughout the craft while the craft remains aloft.
A key feature of the circuit involves the close, proportional
relation between the ambient temperature in the region of the
container CN and the pressure of the gas within the container. As
the temperature of the ambient air rises, the pressure within the
container will rise proportionately, especially if the gas is
freon. A suitable alloy material will respond as indicated when
properly proportioned and arranged so that it will melt as the
temperature reaches a predetermined value.
FIG. 5 illustrates a fitting for a container suitable for the
practice of this invention. The fitting includes a threaded base TB
in which the thermal responsive material or blow-out disc, as the
case may be, may be mounted. The threaded base TB may be meshed
with a corresponding projection PG on the surface of the container
CN. Insulated conductors or any other forms of insulation are
utilized to insulate conductors W1 and W2 from the fitting. The
only conductive path between conductors W1 and W2 is provided
either by the material TH or by the blow-out disc. It will be
observed, as in the other figures of the drawing, that the device
TH may be connected by conductors W1 and W2 to electrical circuitry
of the kinds shown in FIGS. 2, 3 and 4 to indicate whether or not
the device TH has been melted or ruptured.
FIG. 6 shows a segment of a safety relief valve FV of a container
such as CN. This arrangement shows a blowout disc FD, preferably
made of a conductive material, and the disc FD may be wired by
conductors W1 and W2 as a continuous element extending to the
indicator of the indicating equipment of the kinds shown in FIGS.
2, 3 and 4 of the drawing. The indicator will indicate whether or
not the disc FD has been severed from valve FV and the fluid within
the container CN is discharging or has discharged.
On the other hand, FIG. 7 illustrates schematically a safety relief
valve FV which includes a blowout disc FD as well as a thermally
responsive material TH superimposed upon the disc FD and arranged
as a unitary combined structure. The thermally responsive material
TH may be wired, by spaced conductors W1 and W2, to indicating
circuits of the kinds shown in FIGS. 2, 3 and 4. In this case, the
disc FD may be made of plastic or metallic materials, preferably
non-conductive materials, but the thermally responsive element TH
is bonded or otherwise affixed to the disc FD by any well known
process or by any suitable adhesive.
In the FIG. 7 arrangement, the disc FD may be severed from the
valve FV whenever the internal pressure within the container CN
exceeds a predetermined value. When this happens, the contents of
the container will be discharged. On the other hand, as the ambient
temperature reaches a predetermined value--which is dependent upon
the particular thermally responsive material of which the element
TH is made and its dimensions--the disc FD will remain affixed to
the valve FV but the thermal element TH will be melted to break the
continuity of the path between the conductors W1 and W2. Thus, the
indicator in the cockpit of the aircraft will be operated to
indicate that a dangerous condition is about to develop aboard the
craft.
If desired, the melting temperature of the element TH may be
predetermined to be below the temperature corresponding to the
internal pressure of the fluids within the container CN for
severing the disc FD. Hence, a signal will be delivered to the
cockpit before the contents of the container CN are discharged.
This arrangement provides an early warning signal of a condition
that requires careful attention for fire protection.
As will be apparent, the thermal material TH will begin melting
when its melting point is reached and very soon provide an aperture
through which the fire extinguishing fluid contents of the
container CN will be discharged. When the blowout disc TH is
ruptured by the exiting fluids, the lamp LP corresponding to the
container CN will register that the fire extinguisher is
discharging its protective fluid. Hence, the pilot will be alerted
promptly upon the elevation of the ambient temperature that a
condition requiring correction is under development and he may take
the appropriate steps for the protection of the personnel and
craft.
Although the thermal material, such as TH may be a Cerro alloy, any
appropriate fusible material or device may be employed in the
practice of this invention. The blow-out disc may be made of metal
or of any other electrically conductive tape, such as Scotch
X-1181, which will burst at relatively low pressure.
While this invention has been shown and described in certain
arrangements for illustration and explanation, it will be apparent
that the invention may be arranged in widely diverse organizations
suitable for carrying out the objectives of this invention.
* * * * *