A device has been developed for generating a rapid response signal upon the radiation-emitting combustion reaction of certain gases in order to provide a means for the detection and identification of such reaction and concurrently discriminate against spurious signals. This combustion might be the first stage of a coal mine explosion process, and thereby this device could provide a warning of the impending explosion in time to initiate quenching action. This device has the capability of distinguishing between the light emitted from a combustion reaction and the light emitted by miners' lamps, electric lamps, welding sparks or other spurious events so that the quenching mechanism is triggered only when an explosion-initiating combustion occurs

Grose, W. L.

Nealy, J. E.

Trimpi, R. L.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMINIStRATJ0N /
WASHINGTON. D.C. 20546
-10739-1) COMBDSTION
DETECTOR Patent (NASA) 4 p CSCL 14B
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Copy of patent cited above
https://ntrs.nasa.gov/search.jsp?R=19730007757 2020-03-17T08:04:51+00:00Z
PATENTEOJAH 21973 3.708.674
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INVENTORS
ROBERT L. TRIMPI
JOHN E. NEALY
BY WILLIAM UJRROSE
ATTORNEYS
United States Patent
Trimpietal.
[in 3,708,674
[45] Jan. 2,1973
{54] COMBUSTION DETECTOR
[75] Inventors: Robert L. Trimpi; John E. Nealy,
both of Newport News; William L.
Grose, Williamsburg, all of Va.
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration
[22] Filed: April 16,1971
[21] Appl. No.: 134,567
[52] U.S. Cl 250/217 F, 340/228 S, 340/418
[51 ] InL Cl G08b 17/00
[58] Field of Search 340/418, 228 S; 250/217 F,
250/83.3 UV; 356/45, 74
[56] References Cited
UNITED STATES PATENTS
3,609,364 2/1970
3,476,945 11/1969
2,652,743 9/1953
Paine 250/83.3 UV
Golden et al 250/217 F
Morrow 356/45
3,543,260 11/1970
3,513,311 5/1970
3,139,143 6/1964
Engh 250/83.3 UV
McAlister et al 250/83.3 UV
Renda 340/418
Primary Examiner—Ronald L. Wibert
Assistant Examiner—V. P. McGraw
Attorney—Howard J. Osborn
[57] ABSTRACT
A device for generating a rapid response signal upon
the radiation-emitting combustion reaction of certain
gases (or other materials) in order to provide a means
for the detection and identification of such reaction
and concurrently discriminate against spurious signals.
This combustion might be the first stage of a coal
mine explosion process, and thereby this device could
provide a warning of the impending explosion in time
to initiate quenching action. This device has the capa-
bility of distinguishing between the light emitted from
a combustion reaction and the light emitted by miners'
lamps, electric lamps, welding sparks or other spurious
events so that the quenching mechanism is triggered
only when an explosion-initiating combustion occurs.
6 Claims, 2 Drawing Figures '~
12
I
16
-^ PHOTOMULTIPLIER |
•r" . • _
-- ~ - iH PHOTOMULTIPLIER]
^18
19'
SUBTRACTOR
3,708,674
1 2
COMBUSTION DETECTOR BRIEF DESCRIPTION THE DRAWINGS
ORIGIN OF THE INVENTION FIG- 1 is a block diagram of one embodiment of the
invention;-and
The invention described herein was made by em-
 F,G 2 is a Wock diagram of another embodiment of
ployees of the National Aeronautics and Space Ad- 3
 tne invention
ministration and may be manufactured and used by or
for the Government for governmental purposes without DETAILED DESCRIPTION OF THE INVENTION
the payment of any royalties thereon or therefor. _. ... . ,„, . ... .. . .. .J
 ' The embodiments of the invention, as it might be ap-
* BACKGROUND OF THE INVENTION 10 plied in a coal mine, are selected for illustration in the
I drawings. The number 11 in FIG. 1 designates a lens
The invention relates generally to a device for
 which couects iight from a selected area 12 in a coal
^ generating an electrical signal in response to a flash of
 mme. This collected light is separated by a prism 13
light attributable to a combustion process and more jnto a flrst wavelength region around 3,064A and a
specifically concerns a device for generating an electri- 15
 second wavelength region around 3.000A. Light in the
cal signal in response to the light of the combustion flrst wave length region passes through an opening 14
preceding an explosion in a coal mine.
 of a mask 15 to a photomultiplier 16 which produces a
One of the safety devices used in coal mines is a f,rst signal proportional to the amplitude of the intensi-
device for generating an electrical signal in response to
 ty of the emitted light in the first wavelength region,
the combustion which precedes an explosion. This Light in the second wave length region passes through
signal is used to trigger a quenching mechanism which an opening 17 in mask 15 to a photomultiplier 18
discharges quenching agents to arrest the combustion which produces a second signal proportional to the am-
and contain the explosion. plitude of the intensity of the emitted light in the
In the past, devices for the detection and quenching 25 second wavelength region. The second signal is sub-
of coal mine explosions suffered from their inability to tracted from the first signal by a subtracter 19. The
discriminate between the light emitted from hydrocar- resulting difference signal is applied to a quenchant
bon combustion and that emitted by electric lights, mechanism 20 which discharges a quenchant material
electrical sparks, miners' cap lamps, etc. Since the over area 12 when the amplitude of the difference
quenchant mechanism is activated by an internal explo- 30 signal exceeds a predetermined value,
sive charge, the possibility of serious injury to nearby In describing the operation of the embodiment of the
personnel demands a detector which can reject false invention disclosed in FIG. 1, it will be assumed that
signals. It is therefore the primary purpose of this in- there is a source of light emission in region 21 in the
vention to provide a device for the detection of the in- selected area 12. It will further be assumed that light
itiating combustion and for the subsequent quenching 35 emitted in region 21 is not due to a hydrocarbon-air
of coal mine explosions, said device also having the mixture reaction. Then the light from region 21 is coi-
ability to reject false signals. This device could also be lected by lens n and aPPlied to Prism 13 The resulting
applicable to the detection and rejection of, as well as li&hl beams 22 and 23 in wavelength regions around
discrimination between, other pairs of light emitting
 40
 3
'
064A and 3
'
OOOA
' respectively, are applied to
processes upon suitable wave length selection. photomultipliers 16 and 18. Inasmuch as the light
emitted in region 21 is not due to a hydrocarbon-air
SUMMARY OF THE INVENTION mixture reaction the signal produced at the output of
,, . , . n .u , <• photomultiplier 16 is not significantly greater than thatCoal mine explosions are usually the result of com- •; - . , . , . , „ u « •«•
. . . . . . . . . . . .
 A* from photomultiplier 18, hence a very small, if any,bustion of methane-air mixtures which are the first step 45 . . . .. .' . • . . -« _,
. . • i.- i. • • i. • • signal is applied to quenchant mechanism 20. Con-,
of the process which terminates in the explosion.
 sequently, quenchant mechanism 20 is not activated.
Through experimentation it has been proven that dur-
 NQW Mguine a methane.air mixture combustion
ing the transient stages of the combustion initiation of
 reaction occurs in region 21. The signal produced at
methane, a strong emission from a methane flame oc-
 5Q the output of the photonluitipUer 16 is appreciably
curs at 3,064 A, and it was also discovered that a region
 greater than ^ signal produced at the output of
of relatively low emission simultaneously exists nearby photomultiplier 18. Hence a relatively large signal is
at 3.000A. This same differential in emission does not
 appHed to quenchant mechanism 20 causing it to
exist for other sources such as an electric light, an elec- discharge quenchant material over area 12.
trical spark and miners' cap lamps. This discovery of 55 The embodiment of the invention shown in FIG. 2 is
the relative emission levels was used to design the the same as that shown in FIG. 1, except that filters 24
device that constitutes this invention.
 and 25 are used in place or prism 13 and mask 15; and
The component parts of this invention are: an optical divider 26 is used in place of subtracter 19. Filter 24
system to collect the emitted light from the combustion passes light in the wave length region around 3.064A
process; means to spectrally separate this light into two 60
 and fl|ter 25 passes light in the wave length region
separate wave length regions; detectors to measure the around 3,000A.
intensity in these two regions; and associated electronic The advantage of this invention over the prior art is
equipment to functionally operate upon the output its ability to differentiate between combustion light
signals of the detectors to produce a quotient or dif- emission and that emitted by miners' lamps, welding
ference of said signals. The output from the electric sparks, electric lights, etc. Since the quenchant
equipment is employed to activate a quenchant mechanisms for mines must respond very rapidly and
mechanism. are often a cylinder of quenchant which is explosively
3,708,674
\
discharged by an internal charge, the activation of
these quenchant mechanisms is very violent and can
result in injury to nearby personnel. Consequently, the
avoidance of "false alarms" is vital, and prior devices
have not had this avoidance capability.
It is to be understood that the forms of the invention
herewith shown and described are to be taken as
preferred embodiments. Various changes may be made
in the shape, size and arrangement of parts. For exam-
ple, equivalent elements may be substituted for those il-
lustrated and described herein; parts may be reversed
•and certain features of the invention may be utilized in-
dependently of the use of other features, all without de-
parting from the spirit or scope of the invention as
defined in the subjoined claims. A mirror could be used
instead of the lens 11. A diffraction grating could be
used in place of prism 13. Subtracter 19 could be
replaced with a divider and divider 26 could be
replaced with a subtracter. "Light pipes" could be used
to transmit the emitted light in both the external re-
gions from the combustion to the detector and also in
the internal detector system itself. Solid state photode-
tectors could be used.in place of photomultipliers 16
and 18. The invention could be used distinguishing any
one light source iiom all other light sources if the one
light source has sufficiently different spectral charac-
teristics.
What is claimed as new and desired to be secured by
Letters Patent of the United States is:
1. Apparatus for indicating that a radiation emitting
combustion reaction of a predetermined type has oc-
curred in a selected area comprising: optical means for
collecting light for all combustions that occur in said
selected area; means for spectrally separating said col-
lected light into first and second separate narrow wave
length regions with the center of said first wavelength
region being at X and with the center of said second
wavelength region being in the range of 0.9 X to 1.1 X,
said first wavelength region being one of relatively high
emission for said predetermined type of combustion,
reaction and concurrently for all spurious light sources
the emission from the first wave length region being ap-
proximately equal to or less than the emission in the
second wavelength region; means for producing a first
signal whose amplitude is proportional to the emission
in said first wavelength region and a second signal
whose amplitude is proportional to the emission in said
second wavelength region; and a subtracter receiving
said first and second signals for producing an electrical
signal whose amplitude is proportional to the dif-
ference in amplitudes of said first and second signals
whereby whenever the amplitude of said electrical
signal exceeds a predetermined value there is an indica-
tion that a combustion reaction of said predetermined
type has occurred in said selected area.
2. Apparatus according to claim 1 wherein said
5 predetermined type of combustion reaction is a
methane-air mixture type; said selected area is an area
in a coal mine; said first wavelength region is a narrow
region around 3,064A; and said second wavelength re-
gion is a narrow region around 3,000A.
10 3. Apparatus according to claim 1 wherein a divider
is substituted for said subtracter.
4. A method for indicating that a radiation emitting
Combustion reaction of a predetermined type has oc-
curred in a selected area comprising the steps of: col-
15 lecting light from all combustions that occur in said
selected area; spectrally separating said collected light
into first and second separate narrow wavelength re-
gions with the center of said first wavelength region
. . being at X and with the center of said second
20 wavelength region being in the range of 0.9 X to 1.1 X,
said first wavelength region being one of relatively high
emission for said predetermined type of combustion
reaction and said second wavelength region being one
of relatively low emission for said predetermined type
2s of combustion reaction and concurrently for all spuri-
ous light sources the emission from the first wavelength
region being approximately equal to or less than the
emission in the second wavelength region; producing a
first signal whose amplitude is proportional to the emis-
30 sion in said first wavelength region; producing a second
signal whose amplitude is proportional to the emission
in said second wavelength region; and producing an
electrical signal whose amplitude is proportional to the
difference in the amplitudes of said first and second
35 signals whereby whenever the amplitude of said electri-
cal signal exceeds a predetermined value there is an in-
dication that a combustion reaction of said predeter-
mined type has occurred in said selected area.
5. A method according to claim 4 wherein the step of
40 producing an electrical signal whose amplitude is pro-
portional to the ratio of the amplitudes of said first and
second signals is substituted for the step of producing
an electrical signal whose amplitude is proportional to
the difference in the amplitudes of said first and second
45 signals.
6. A method according to claim 4 -wherein said
predetermined type of combustion reaction is a
methane-air mixture type; said selected area is an area
in a coal mine; said first wavelength region is a narrow
50 region around 3,064A; and said second wavelength re-
gion is a narrow region around 3,000A.
55
60
65


Combustion detector

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