Note: Descriptions are shown in the official language in which they were submitted.
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~ Field of the Invention
~ This invention relates to a combustion detection device, and
more particularly relates to an apparatus for detecting the presence
of fire and providing an al,arm,,indicative thereof.
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Back~round of the Invention
Various types of sensing devices have been developed
for monitoring a variety of conditions. One of the more
important conditions often monitored is that of combustion
in an effort to discover and thus minimize loss due to fire,
particularly in buildings or other structures where the
presence of a fire could go unnoticed until far too late to
minimize loss to any appreciable extent.
Combustion detection devices have heretofore been
suggested and/or utilized, but such devices have not proved
to be completely satisfactory for all situations due to such
diverse factors as being subject to mechanical and/or electrical
component failure, vacuum leakage and aging where vacuum tube
structures are utilized, and/or being relatively complex and/
or of expensive construction so as to be impractical for at
least some uses.
A combustion detection device providing pulsed ~ensing
utilizing an ionization detector is shown, for example, in
U. S. Letters Patent Number 3,842,~09, entitled, "Ionization
Detector Apparatus", issued October lS, 1974 to Ronn H.
Mayer and assigned to the assignee of the present invention.
The detector of this invention constitutes an alternative to
the structure shown and claimed in U. 5. Patent Number
3,842,409.
Summary of the Invention
It is an object of this invention to provide an im-
proved combustion detection apparatus.
It is another object of this invention to provide an
improved combustion detection apparatus suitable for-auto-
matically monitoring a location to sense fire conditions.
One aspect of the present invention is defined as acombustion detection apparatus, comprising: ionization
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detection means providing an output indicative of products
of combustion sensed by the detection means; a pair of input
leads adapted to be connected to a power supply; a reference
voltage source providing a reference voltage output; com-
parator means for receiving the output from the ionization `~
detection means and the reference voltage output, the
comparator means having an inhibit input and drive and sink
outputs with the comparator means providing an output if
the output from the ionization detection means exceeds the
reference voltage received from the reference voltage source;trigger means including first and second normally non-conductive
semi-conductor means one of which is connected with the com-
parator means to receive the drive output therefrom and the
other of which is connected with the inhibit input of the
comparator means whereby the semi-conductor means are caused
to become conductive upon receiving an output from the com-
parator means; and connecting means for connecting the semi-
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conductor means between the two input leads to essentiallyshort the same upon receipt of a signal from the comparator
means to thereby achieve sensing of a fire by the apparatus
whereby the sensed fire can be indicated by an alarm indicating
device when so connected with the two input leads.
Another aspect of the present invention is defined as
a combustion detection apparatus, comprising: ioni~ation
detection means including first and second americium 241
chambers, one of which is open to the atmosphere and the
other of which is substantially closed, the chambers being
connected so that the ionization detection means provides
an output voltage that varies depending upon sensed products
; 30 of combustion in the atmosphere surrounding the open chamber;
a reference voltage source providiny a reference voltage
output; comparator means for receiving the ouput from the
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ionization detection means and the reference voltage output,
the comparator means having an inhibit input, a drive output
and a sink output and providing an output if the output from -
the ionization detection means exceeds the reference voltage
output from the reference voltage source; trigger means in-
cluding first and second interconnected normally nonconductive
transistors one of which is connected with the comparator
means to receive the drive output therefrom and the other of ,,
which is connected with the inhibit input of the comparator
means whereby the transistors are caused to become conductive
upon receiving an output from the comparator means; alarm
indicating means connected with the trigger means and, re-
sponsive to the transistors becoming conductive, causing and
maintaining an alarm condition; and means for receiving the
alarm indication from the alarm indicating means and indicating
an alarm condition.
. With these and other objects in view, which will become
apparent to one skilled in the art as the description proceeds,
this invention resides in the novel construction, combination,
and arrangement of parts substantial ~ as hereinafter des-
cribed and more particularly defined by the appended claims,
it being understood that such changes in the precise embodiment
of the hereindisclosed invention are meant to be included as ~,
come within the scope of the claims.
Brief Description of the Drawin~
The accompanying drawings illustrate two complete
embodiments of the invention according to the best mode so
far devised for the practica~ application of the principles
thereof and in which:
FIGURE 1 is an electrical schematic diagram of the
combustion detection apparatus of this invention with the
; trigg~ring circuit shown to include a silicon controlled
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rectifier; and
FIGURE 2 is an electrical schematic diagram of the
prererred embodiment of the combustion detection apparatus
of this invention with the triggering circuit shown to in-
clude a pair of transistors.
Detailed Description of the Invention
Referring now to the drawin~s, the numeral 5 indicates
the combustion detection apparatus for the embodiment illus-
trated in FIGURE 1. A pair of leads 7 and 8 are provided,
which leads are adapted to be connected with a conventional
power supply (not shown) with lead 7 providing +24 volts
and lead 3 being a return lead. A diode 10 is connected
between the +24-volt power supply (not shown) and lead 7,
with lead 7 also being connected with lead 8 through series
connected resistors 11 and 12 and capacitor 14.
Ionization detector 16 is connected between leads 7
and 8,and, as indicated in FIGURE 1, includes a pair of
americium 241 chambers 18 and 19 (radium 226 could be utilized,
if desired). Ionization detector 16 senses the products of
combustion present in the atmosphere surrounding the detector
and provides an output voltage indicative thereof. Americium
241 chamber 18 is preferably substantially closed and, thus,
serves as a reference detector while americium 241 chamber 19
is preferably open to sample or monitor the atmosphere
surrounding the detector. The output from the detector is
taken from the junction 21 between the chambers with the
output coupled to the input of field effect transistor (FET)
23. In the absence of a sensed fire condition, i.e., under
normal operating conditions, the voltage at junction 21 is
about 6 volts.
Field effect transistor 23, which preferably is a ~FET
type, serves as an amplifier and has the drain electrode
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connected with lead 7 and the sou~ce electrode connected
with lead 8 throu~h resistor 25. The output of the field
effect transistor 23 is coupled from the source electrode
to the positive input of operational amplifier, or com-
parator 27, which operational amplifier receives a reference
volta~e supply 2~. Reference voltage supply 29 includes
resistor 31, potentiometer 32 and resistor 33 connected in
. series between leads 7 and 8, with the center tap 35 of the
potentiometer being connected to the negative input of :~
operational amplifier 27.
Pins 7 and 8 of operational amplifier 27 are directly
connected to leads 7, while pin 5 is connected thereto through
resistor 36. In addition, pin 4 of operational amplifier 27
i8 directly connected to lead 8 while pin 1 is connected to
lead 8 through capacitor 38, and pin 8 is connected to lead
8 through capacitor 40.
j The output from operational amplifier 27 is coupled
from pin 6 to the gate electrode of si.licon controlled
rectifier 43, with pin 6 also being.connected to lead 8
through resistor 44. Silicon controlled rectifier 43 has its
cathode connected to lead 8 while the anode is connected
through resistor 46 (a 10 ohm resistor) and light-emitting
, diode (LED) 47 to lead 7. In addition, a bypass capacitor
'~ 49 i8 connected between the anode of silicon controlled rec-
tifier 43 and lead 8, and a lead to an external indïcator
(not shown) is cannected to the junction of resistor 46 and
LE~ 47 through diode 50.
Callbration leads 52 and 53 are also p~ovided to
, facilitate calibration of the apparatus~ Lead 52 is
connected to lead 7 and to lead 8 through parallel connected
capacitor 55 and zener diode 56, while the lead 53 is dir-
ectly connected to americium 241 chamber 18 of ionization
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detector 16.
The following is a listing of components that have
been utilized in a working embodiment of the invention as
shown in FIGURE 1, it being understood that such listing
is for illustrative purposes only and the in~ention is not
meant to be limited thereto:
Diodes 10 and 50 - lN4004
Zener Diode 56 - 2N759B (12v)
LED 47 - Red Lite 4
JFET 23 - 2N4117A
Comparator 27 - CA 3094
SCR 43 - 2N 5061
Resistors ~ohms) 11, 12
and 25, - 47K
36 - lM
31 - 2.2M
33 - 2.7M
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46 - 10
Potentiometer 32 - 0-lM ohms
Capacitors (~ Fd) 14,
38, 49 and 55 - 0.1
-47
In operation, the apparatus is preferably initially
calibrated by connection of leads 52 and 53 to an external
calibration means and then setting potentiometer 32 to the
particular threshold desired, normally about 7.2 volts, for
example. The apparatus is theo placed
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in any convenient position where continuous monitoring is desired
for products of combustion, i.e., to sense the presence of a ~ire.
When no fire is sensed, the output from the ionization detector
will be such that the field effect transistor is maintained in a
conductive state, but the outp~ voltage is maintained below the
setting of the reference voltage supplied to the negative input to
the comparator (operational amplifier 27) so that the comaprator
will therefore provide no output to the silicon controlled rectifier
and, hence, no alarm will be energized.
When a fire is sensed by the apparatus, however, the output
from the ionization detector will increase to the extent that the
field effect transistor supplies a sufficient voltage so that an
output will be coupled from comparator 27, such a voltage, of course,
exceeds the reference voltage supplied from potentiometer 32 to the
comparator negative input. When the output thus e~ceeds the refer-
ence voltage supplied to the comparator, comparator 27 will then
provide an output to silicon controlled rectifier 43 to trigger the
rectifier. When the SCR 43 fires, a short will be essentially
developed across the power supply leads 7 and 8 through resistor 46
and LED 47 to indicate an alarm condition, and the light-emitting
Z diode 47 will be energized. Silicon controlled rectifler 43 will
remain eneryized to thus continuously indicate an alarm condition
until the power is removed and later reapplied after ionization
detector 16 no longer senses a product of combustion indicative of
a fire. A virtual short across the power supply leads 7 and 8 can
be reflected in remote equipment, for example, or at a control point,
to give an alarm condition in conventional ~ashion to an operator.
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FIGURE 2 shows the preferred embodiment 105 o~ the
invention. The two disclosed embodiments utilize similar
components, and where utilized, have been identified by the
same reference numerals. For example, leads 7 and 8 have
ionization detector 16 connected therebetween with the
junction 21 between americium chambers 18 and 19 being
connected to the input of field effect transistor 23. In
like manner, the output of the field effect transistor 23
is coupled from the source electrode to the positive input
of operational amplifier 27, which amplifier receives a
negative input from a reference voltage supply (identified
as 129).
The values of resistors 112 (connected with line 7),
resistor 125 (connected to the source electrode of FET 23),
and resistors 131 and 133 (in the reference voltage supply)
are, however, unlike the values of resistors 12, 25, 31 and 33,
and accordingly, have been given new numerals as shown in
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FIGURE 2.
As also shown in FIGURE 2, operational amplifier 27 is
connected to a triggering circuit which includes a pair of
transistors 160 and 161 with transistor 160 having its base
connected to the drive output (pin 6) and its collector con-
nected to the sink output (pin 8) of operational amplifier 27.
As also shown in FIGURE 2, the base of transistor 161 is con-
nected to the sink output tpin 8) of operational amplifier 27
through resistor 163 and the collector of transistor 161 is
connected to the inhibit input (pin 1) of operational amplifier
27 through resistor 164. The emitter of transistor 160 is
directly connected to return lead 8, while the base of trans-
istor 160 is connected with power supply lead 7 throughresistor 165. In addition, pin 1 o~ operational amplifier 27
is connected with return lead 8 through capacitor 138 and pin 5
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of operatlonal amplifier 27 is connected with power supply
lead 7 through resistor 136.
The following is a listing of components (in addition ~ -
to like identified components in FIGURE 1 as identified
hereinabove) that have been utilized in a working embodiment
of the preferred form of this invention, it being understood
that such listing is for illustrative purposes only and the
invention is not meant to be limited thereto:
Resistors (ohms) 112, 144
and 165, - 10
10125 and 133, - 1.2M
131 - 470K
136 - lOM
163 - 360
164 - lM
Capacitor (~ Fd) 138 - 1
Transistors 160 - 2N2222
161 - 2N2907
The operation of the invention as shown in FIGURE 2
is similar to that of FIGURE 1 except that the triggering
circuit includes transistors 160 and 161 connected to the
; outputs of operational amplifi~r 27 with the collector of
transistor 161 being coupled to pin 1 (of the operational
amplifier) through a Darlington output (that includes pins
1, 6 and 8).
With no fire sensed, the output from the ionization
detector will be such as to maintain the field effect trans-
istor in a conductive state while providing an output voltage
to operational amplifier 27 less than that of the reference
voltage output so that transistor 160 is maintained in a non-
conductive state which results in a no alarm condition.
When a fire is sensed, however, the output from the
ionization detector increases as does the output from the
field effect transistor. When the output from the field
effect transistor exceeds the reference voltage at the
operation~l amplifier, an output is providad by the
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operational amplifier to cause transistor 160 to conduct
and this essentially shorts the leads 7 and 8 through LED
47 and transistor 160 connected in series across leads 7
and 8. When transistor 160 conducts, transistor 161 starts
to conduct and transistor 161 is connected to operational
amplifier 27 so that transistors 160 and 161 will remain
eonduetive until power to the apparatus is diseontinued. After
the eondition eausing the alarm has been eorreeted, the
apparatus will produee no output when power is reapplied
until a eondition again exists causing an output to be
produeed by the operational amplifier.
In view of the foregoing, it is to be realized that
the combustion detector apparatus of this invention provides
an improved device that is particularly well suited for con-
tinuous monitoring to sense products of combustion indica-
tive of the presenee of a fire.
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