Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02803173 2013-01-16
MULTIPLE DISCHARGE FIRE EXTINGUISHING SYSTEM
BACKGROUND OF THE INVENTION
This application relates to a fire extinguishing system which is received in a
space in a vehicle to extinguish fires and prevent explosions within the
space.
Vehicles are often provided with fire extinguishing systems, and in particular
with systems which are structured to quickly extinguish flames under any
number of
conditions. Often aircraft are provided with elaborate extinguishing systems
that
include long passageways to provide extinguishing materials from a distant
source to
any number of locations on the aircraft. Aircraft fire extinguishing systems
may
include a first dispensing cycle which is intended to extinguish a fire, and
then an
inert gas dispensing mode which occurs for a period of time, until the
aircraft can
land.
In general, the aircraft extinguishing systems are intended to control a fire
until an aircraft can land. Thus, they are provided with long-term dispensing
over
many minutes, and even hours.
Ground based vehicles have typically been provided with less elaborate fire
extinguishing systems. However, and in particular with ground based military
vehicles, systems must be provided which are quickly actuated to extinguish a
flame.
Thus, it is known to provide a cylinder in a vehicle space, such as a crew
compartment, which has automatic fire extinguishing systems deployed after an
event is detected. Typically, sensors identify a fire or explosion threat, and
include a
fast acting release mechanism and nozzle which enables rapid and efficient
deployment of an agent throughout the crew compartment.
SUMMARY OF THE INVENTION
A fire extinguishing system for use in a crew compartment of a ground-based
vehicle includes at least two cylinders. The cylinders dispense a fire
extinguishing
agent through a release mechanism. A control for the overall system is
operable to
actuate the two cylinders. A nozzle is positioned downstream of the release
mechanism to distinguish the extinguishing agent into the crew compartment.
The
majority of the dispensing from at least a first of the two cylinders occurs
in less than
five seconds.
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These and other features of the invention would be better understood from the
following specifications and drawings, the following of which is a brief
description.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a prior art system.
Figure 2 shows a first inventive system.
Figure 3 shows a second inventive system.
Figure 4 illustrates a third embodiment.
Figure 5 shows yet another embodiment.
Figure 6 shows another embodiment.
DETAILED DESCRIPTION
Figure 1 shows a known system 20 incorporating a cylinder 22 which is
received within a crew compartment 23 in a ground based vehicle. A nozzle 24
is
associated with a fast acting release mechanism 27. Sensors 28, shown
schematically, sense the presence of a fire or explosive risk in the crew
compartment
23, and actuate the release mechanism 27 to dispense an agent into the crew
compartment. The sensors may be infrared or ultraviolet, as examples.
The dispensing can occur within 30 milliseconds of the detection occurring.
The discharge can occur for 50 milliseconds to 1 second, as an example.
The agent will typically suppress or knock down the explosive threat.
However, at times, it may be desirable or necessary to have the ability to
react to a
second event. As an example, and in particular with military vehicles, a crew
compartment could be hit a subsequent time. Also, fuel leakage, etc., could re-
establish a previously extinguished fire threat.
Thus, as shown in Figure 2, an inventive system 120 incorporates at least two
cylinders 124 and 126 associated with a nozzle 24. A line 180 communicates
cylinders 124 and 126 to the nozzle 24. As shown to the right hand side of
Figure 2,
it is possible for a third, and even further cylinders to be associated with
the system
120.
A control 122 is set to actuate the fast acting release mechanism 123 as
necessary. A sensor 121 provides signals to the control 122. The dispensing
occurs
very rapidly. This is true for all of the embodiments in this application. At
least the
initial cylinder has the majority of its dispensing occur in less than five
seconds, and
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typically less than 1.5 seconds, and even more typically less than one second.
The
dispensing can occur much more rapidly, and can be on the order of 50
millisecond.
There may be a time delay between actuation of the cylinders 124 and 126, or
the cylinder 126 may be kept in reserve for a subsequent restrike, or the
flame
restarting. As an example, a military crew compartment could be subject to
multiple
strikes, such as shells. Also, a flame that had previously been extinguished
could
increase in magnitude. The reserve cylinder may be actuated in those events.
Both
subsequent events may be sensed by the sensor 121.
In the Figure 2 embodiment, both cylinders 124 and 126 are provided
generally with the same extinguishing agent. Examples may include but not be
limited to potassium bicarbonate (KHCO3) and sodium bicarbonate (NaHCO3)or BC
powder Water based agents such as potassium lactate, potassium acetate and
plain
water may be utilized along with an inert gas or water vapor as optional
additions. It
can be appreciated that there are many conventional gaseous fire suppression
agents
are contemplated including but not limited to 1,1,1,2,3,3,3-heptafluoropropane
(i.e.,
HFC-227ea (e.g., FM200 )), and 1,1,1,2,2,4,5,5,5-nonafluoro-4-
(trifluoromethyl)-3-
pentanone (i.e., FK-5.1.12 (e.g., Novec 1230 )). In certain cases it may also
be
advantageous to mix extinguishing agents within the same canister. One such
example is the addition of a small mass of BC powder (typically 5 -10 wt%)
within
HFC-227ea.
Figure 3 shows an embodiment which is very similar to Figure 2, however, in
the Figure 3 embodiment 220, the cylinder 226 is provided with a distinct
extinguishing material from that in the cylinder 124. As an example, the
cylinder
226 may be provided with a higher percentage of inert gas or water vapor,
however,
it would also typically be provided with an extinguishing agent such as BC
powder.
The higher percentage of inert gas or water vapor makes this arrangement
better
suited to a system wherein the second cylinder is actuated to maintain an
inert
environment after the flame has been extinguished. The Figure 2 embodiment
might
be better suited to systems wherein the second cylinder is only actuated when
a
subsequent signal is received, such as a restrike or a restarting of the
flame.
The Figure 3 embodiment may be set such that the actuation of the release
mechanisms 123 would be simultaneous, but wherein the discharge
characteristics
would be distinct such that the cylinder 226 would tend to discharger later.
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However, the control as utilized in the Figure 2 embodiment may also be
incorporated into this embodiment, wherein there is a time delay, or there may
be a
requirement for a restrike for actuation of the secondary cylinder.
Figure 4 shows an embodiment 320 wherein a single body incorporates the
cylinders 124 and 326. The control 322 still controls the single release
mechanism
325 based upon signals from a sensor 121. The release mechanism 325
distributes
the material from both cylinders 124 and 326 through the common nozzle 24.
This
embodiment may have a passage closed by a seal or membrane 324 which may be
pierced in some manner to allow the fire extinguishing material from the
cylinder
326 to pass through the release mechanism 325. The actuation of the membrane
or
other seal at 324 can be time delayed relative to the distribution from the
cylinder
124, or may be utilized with the requirement of a restrike or restart of the
flame.
Figure 5 shows an embodiment 410 having a control 420. The system may be
otherwise as shown in Figure 4, with a membrane or other seal 424 between the
cylinders 426 and 124. The Figure 5 embodiment differs from the Figure 4
embodiment in much the same way as the Figures 2 and 3 embodiments differ,
namely with regard to the extinguishing materials in the cylinders 326 and
426.
Figure 6 shows another embodiment wherein each cylinder 200, 202 is
provided with its own nozzle 206 associated with the release mechanism 204. It
should be understood that this arrangement can be used with any of the
embodiments
shown in Figures 2-5. In addition, some small conduit can be placed between
the
nozzle 206 and the release mechanism 204.
Across all of the embodiments, it is expected and preferred that the nozzles
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(or 206) be positioned to be within three meters of the cylinders. More
preferably,
the nozzle should be within one meter of these cylinders.
While some fire suppressant agents and inert materials have been disclosed
above, any combination of agents and materials which are acceptable under
current
environmental regulations may be utilized. As an example, insert gases such as
nitrogen or Argon, or CO2 up to 3 vol% may be used. Water-based agents may be
in
liquid and/or vapor form. Additives such as alkali salts (e.g., potassium
bicarbonate,
potassium acetate, potassium lactate, etc.) or foams (e.g., AFFF), and finally
dry
chemicals (e.g., sodium bicarbonate, potassium bicarbonate, MonnexTM) may be
utilized.
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In addition, if a delay is desired between the actuation of the second
cylinder
and the first, the initiation time may be controlled. A fast
electronic/pyrotechnic
initiator can be utilized for the main cylinder, followed by a slower
electronic or
pyrotechnic initiator, or a gas generator which would take a longer period of
time to
actuate to initiate the secondary cylinder. Again, the amount of the delay
would be
controlled as desired. A difference in mass flow and discharge time can also
be
achieved between the two cylinders by varying the outlet diameter, and the
volume of
the cylinders, respectively.
In summary, the embodiments of this invention disclose systems where in a
single system placed in a crew compartment is capable of multiple dispensing
of fire
extinguishing materials. A worker of ordinary skill in the art would recognize
that
modifications will come within the scope of this invention. For that reason,
the
following claims should be studied to determine the true scope and content of
this
invention.
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