Combustion products alarm
United States Patent 3906474
A combustion products detector of the ionization chamber type comprises a reference ionization chamber and a signal chamber arranged in series for connection across a direct current source such as a dry battery. An insulated gate field effect transistor is arranged with its drain electrode for connection to the high side of the source, and with its source electrode to the law side; its gate is connected to the common junction of the chambers; a high resistance is connected across the chambers in parallel. A control amplifier supplies the signal to a circuit for producing a preliminary alarm or proximity signal upon a predetermined increase in combustion product density in the signal chamber and a full alarm upon an additional increase. The alarm may be produced as a throbbing or undulating sound.
US Patent References:
Electrotechnique
Failla - February 1939 - 2145866
METHOD AND APPARATUS FOR DETECTING AEROSOLS
Suchomel et al. - May 1972 - 3665441
IONIZATION FIRE ALARM WITH INSULATION MONITORING SYSTEM
Scheidweiler et al. - July 1972 - 3676680
FLASHING CIRCUIT
Zeewy - June 1973 - 3737731
FIRE ALARM WITH IONIZATION CHAMBER
Beyersdorf et al. - March 1974 - 3795904
Electrotechnique
Failla - February 1939 - 2145866
METHOD AND APPARATUS FOR DETECTING AEROSOLS
Suchomel et al. - May 1972 - 3665441
IONIZATION FIRE ALARM WITH INSULATION MONITORING SYSTEM
Scheidweiler et al. - July 1972 - 3676680
FLASHING CIRCUIT
Zeewy - June 1973 - 3737731
FIRE ALARM WITH IONIZATION CHAMBER
Beyersdorf et al. - March 1974 - 3795904
Application Number:
05/358111
Publication Date:
09/16/1975
Filing Date:
05/07/1973
View Patent Images:
Export Citation:
Assignee:
Fire Alert Company (Wheat Ridge, CO)
Primary Class:
Other Classes:
250/384
International Classes:
G08B17/11; G08B17/10; G08B17/10
Field of Search:
340/237S 250/381,382,384,385,389
US Patent References:
| 3801972 | GAS ANALYZER CIRCUITRY | April 1974 | Kim et al. |
Primary Examiner:
Caldwell, John W.
Assistant Examiner:
Myer, Daniel
Attorney, Agent or Firm:
Edwards, Wm Griffith
Claims:
What is claimed is
1. A combustion product detector of the ionization chamber type comprising:
2. In a combustion product detector of the ionization chamber type including a sampling chamber and a reference chamber, means for producing an output signal proportional to the density of combustion product in the sampling chamber, means for producing an amplified voltage proportional to said output signal, and means dependent upon a predetermined amplified voltage for actuating an alarm indicator, the method of calibrating the detector for determination of the density of combustion product in said sampling chamber which comprises:
3. The method of calibrating a plurality of like combustion product detectors each of the ionization chamber type including a sampling chamber and a reference chamber, means for producing an output signal proportional to the density of combustion product in the sampling chamber, means for producing an amplified voltage proportional to said output signal and means dependent upon a predetermined amplified voltage for actuating an alarm indicator, comprising the steps of:
1. A combustion product detector of the ionization chamber type comprising:
2. In a combustion product detector of the ionization chamber type including a sampling chamber and a reference chamber, means for producing an output signal proportional to the density of combustion product in the sampling chamber, means for producing an amplified voltage proportional to said output signal, and means dependent upon a predetermined amplified voltage for actuating an alarm indicator, the method of calibrating the detector for determination of the density of combustion product in said sampling chamber which comprises:
3. The method of calibrating a plurality of like combustion product detectors each of the ionization chamber type including a sampling chamber and a reference chamber, means for producing an output signal proportional to the density of combustion product in the sampling chamber, means for producing an amplified voltage proportional to said output signal and means dependent upon a predetermined amplified voltage for actuating an alarm indicator, comprising the steps of:
Description:
This invention relates to combustion product detectors and particularly to an improved detector of the ionization chamber type.
Numerous circuits have been provided heretofore for the purpose of utilizing ionization chamber detectors for actuating fire indicators and alarms. These circuits have proved useful to varying degrees depending upon the conditions prevailing and the nature of the applications of the circuits. Reliability and consistent operation of fire detectors over a wide range of ambient conditions are desired and, accordingly, it is an object of this invention to provide an improved reliable combustion product detector of the ionization chamber type.
It is another object of this invention to provide a combustion product detector of the ion chamber type including an improved circuit for operation from an electric battery as a direct current source.
It is a further object of this invention to provide an improved combustion product detector including an arrangement for providing a preliminary warning before the energization of an alarm.
Briefly, in carrying out the objects of this invention in one embodiment thereof, two ion chambers, one a reference, the other a signal chamber are connected in series with a variable resistance across a D.C. source. An insulated gate field effect transistor is connected across the source with its gate connected to the junction between the chambers. Upon increase in product in the signal chamber a control transistor energizes a unijunction oscillator which actuates a light emitting diode causing it to flash periodically to warn of the proximity of alarm conditions and which upon further increase of product, glows steadily before the circuit activates the alarm.
The features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. The invention itself, however, both as to its organization and its manner of operation, together with further objects and advantages thereof, will best be understood upon reference to the following description taken in connection with the accompanying drawing, the single FIGURE of which is a schematic diagram of a combustion products detector embodying the invention.
Referring now to the drawings, two ionization chambers 10 and 11 are connected in series with a dual potentiometer circuit 13 across a direct current source which has been illustrated as a battery comprising two units 14 and 15. A loading resistor 16 is connected in parallel with the two chambers. The resistance 16 may be of the order of 2 meghohms. The circuit 13 in addition to a resistance 17 includes a fixed resistance 18 and an adjustable resistance 19. The resistance 17 is connected to the junction of the resistances 18 and 19 by an adjustable contact 21 and the resistance 19 is connected as a potentiometer by an adjustable contact 22 which shorts out a selected portion of the resistance toward the high potential end thereof. The test switch 23 is provided which is normally open and when closed shorts out resistances 17, 18 and 19 and places the chambers 10 and 11 directly across the power supply putting the unit into test alarm condition. This alarm condition provides a 100% component test equal to combustion products alarm. Chamber 10 is a reference chamber and the chamber 11 a sampling or signal chamber responsive to changes in the ambient atmosphere about the detector. The junction of the two chambers is connected to the gate of a field effect transistor 24, the gate being indicated at 25. Transistor 24 is of the insulated gate type and is an N-channel depletion mode metal oxide silicon field effect transistor. The transistor is connected across the direct current supply, its drain electrode being connected to the high potential side of the supply and its source electrode being connected to the low side through a resistance 26. When a change in combustion product density occurs in the ionized chamber 11, this change in density of the product decreases the current through the circuit of the chambers and increases the potential at the gate 25; as a result current flows through the transistor 24 and a control transistor 27 which has its base connected to the junction between the source of the transistor 24 and the resistance 26 conducts. The collector of the transistor 27 is connected to a circuit including a unijunction transistor 28 connected as an oscillator having its base-two connected to the high side of the D.C. source and its base-one connected to the collector through resistances 30 and 31 in series. A light emitting diode 32 is connected across the resistor 31. The emitter of the unijunction 28 is connected to the high side of the source by a resistance 33 and to the collector of the transistor 27 by a capacitance 34 thus completing the oscillator circuit. During operation of the oscillator the light emitting diode 32 flashes and indicates that the combustion product density is approaching alarm condition. As a predetermined further increase of the potential difference between the supply and the transistor 27, a Zener diode 35, connected in series with the winding of an alarm relay indicated at 36, conducts and the diode glows steadily. On a further increase of voltage difference, which in the alarm condition, the winding 36 is energized to actuate the relay and move a switch 37 to its upper position thereby connecting an alarm circuit 38 across the battery comprising the units 14 and 15. A unijunction transistor 40 is connected as an oscillator across the direct current source by resistances 41 and 42 and with its emitter connected to the common junction of a resistance 43 and capacitance 44. The base-one terminal of the unijunction 40 is connected through a diode 45 to the base-one terminal of a unijunction 46 which is connected to the high side of the source through a resistance 47, the base-two terminal being connected to the low side through a line 48. A resistance 50 and a capacitance 51 connected in series across the source have their common junction connected to the emitter of the unijunction 46, as indicated at 52, and complete the oscillator circuit. The unijunction transistor 46 is a lower frequency oscillator which acts as a "warbler" modifying the sound effect produced by the oscillation rate of the unijunction oscillator 40. The output of the oscillator 40 is supplied to the base of a transistor amplifier 53 through a resistance 54. The amplifier 53 when conducting energizes a winding 55 of a horn or loudspeaker 56 and the periodic output of the oscillator 40, modified at the lower rate by the oscillator 46, is reproduced as the warning sound by the horn 56.
In order to minimize drain on the battery 14 and 15 a diode 57 is connected in the emitter circuit of the transistor 27 which has been illustrated as connected to the common junction of the two battery sections. The diode 57 prevents reverse flow and drain from the battery 15.
The circuit of this invention makes it possible to calibrate the detectors by means of a simple D.C. voltmeter. When the transistor 27 is not conducting, the voltage between the test points, indicated at 60 and 61, is the same, however, when the transistor conducts the voltage increases with increase in the current through the transistor and hence through the resistances 30, 31 and 33 and the unijunction 28. This voltage varies directly with the density of the combustion product in the chamber 11 and is an indication of that density and may be used to monitor the performance of the detector. The maximum voltage between the test points 60 and 61 immediately prior to energization of the relay winding is an accurate indication of the calibration setting of the detector for alarm operation. This voltage may thus be used for calibrating the detector by adjustment of the potentiometers to obtain alarm operation at a preselected density of product in the chamber 11.
The alarm actuating voltage across the relay winding 36 and the Zener diode 35 in series is the same for all combustion product densities. The density of product at which the voltage is attained is determined by the setting of the potentiometer 17 which is the sensitivity control of the circuit. With no product in the chamber 11 the voltage across the test points is substantially zero. With a selected setting of the sensitivity potentiometer, the voltage between zero and the alarm voltage indicates the product density in the chamber 11. A D.C. voltmeter may thus be employed to determine the state of operation of the detector and also to calibrate the detector.
In initial calibration the potentiometers may be set for a fractional portion of the alarm density by subjecting the chamber 11 to product of such density and setting the potentiometer to the corresponding fractional setting of the voltage across the terminals 60 and 61. The detector will then operate to produce a voltage across the test terminals proportional to whatever density of product is present in the sampling chamber. By following these voltage measuring procedures, a large number of like detectors may be calibrated by calibrating a first detector using product densities in the chamber 11 to obtain the calibrations and corresponding voltages of the first detector, and then setting all other detectors accordingly and using voltages measured at the test terminals for this purpose. Thus, it is not necessary to use the samples of combustion product for calibration of the other detectors of like construction.
As an illustration of a working embodiment of the present invention and for purposes of example and not by way of limitation, a detector having a circuit connected as shown in the drawing and having the component values set forth below, operated successfully over an extended period of time and with a large number of operations due to the presence of combustion product in the test or sampling chamber 11. The chambers 10 and 11 were cylindrical, the chamber reference having a volume of about 0.8 cubic inches and the sampling chamber being about 25 percent larger.
The transistors were as follows: 24 field effect transistor MU-612, the unijunctions 28, 40 and 46 were all type 2N4871, diode 32 was a light emitting diode type NV10B, the control transistor 27 was a type 2N3643, the transistor 53 type 2N6099, the diodes 35 and 57 were type 1N4148, the Zener diode 35 was type 1N746A, the resistances were as follows:
17 and 19 one megohm
16-2 meghoms
18-390,000 ohms
33 and 43 - 10,000 ohms
26-82,000 ohms
31-1,000 ohms
50-12,000 ohms
30-220 ohms
41 and 47 - 180 ohms
42 and 54 - 150 ohms
The capacitors 35 and 51, 50 microfarads
44 - one-tenth microfarad
While the invention has been described in connection with a specific embodiment thereof, various modifications and applications will occur to those skilled in the art. Therefore, it is not desired that the invention be limited to the details illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.
Numerous circuits have been provided heretofore for the purpose of utilizing ionization chamber detectors for actuating fire indicators and alarms. These circuits have proved useful to varying degrees depending upon the conditions prevailing and the nature of the applications of the circuits. Reliability and consistent operation of fire detectors over a wide range of ambient conditions are desired and, accordingly, it is an object of this invention to provide an improved reliable combustion product detector of the ionization chamber type.
It is another object of this invention to provide a combustion product detector of the ion chamber type including an improved circuit for operation from an electric battery as a direct current source.
It is a further object of this invention to provide an improved combustion product detector including an arrangement for providing a preliminary warning before the energization of an alarm.
Briefly, in carrying out the objects of this invention in one embodiment thereof, two ion chambers, one a reference, the other a signal chamber are connected in series with a variable resistance across a D.C. source. An insulated gate field effect transistor is connected across the source with its gate connected to the junction between the chambers. Upon increase in product in the signal chamber a control transistor energizes a unijunction oscillator which actuates a light emitting diode causing it to flash periodically to warn of the proximity of alarm conditions and which upon further increase of product, glows steadily before the circuit activates the alarm.
The features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. The invention itself, however, both as to its organization and its manner of operation, together with further objects and advantages thereof, will best be understood upon reference to the following description taken in connection with the accompanying drawing, the single FIGURE of which is a schematic diagram of a combustion products detector embodying the invention.
Referring now to the drawings, two ionization chambers 10 and 11 are connected in series with a dual potentiometer circuit 13 across a direct current source which has been illustrated as a battery comprising two units 14 and 15. A loading resistor 16 is connected in parallel with the two chambers. The resistance 16 may be of the order of 2 meghohms. The circuit 13 in addition to a resistance 17 includes a fixed resistance 18 and an adjustable resistance 19. The resistance 17 is connected to the junction of the resistances 18 and 19 by an adjustable contact 21 and the resistance 19 is connected as a potentiometer by an adjustable contact 22 which shorts out a selected portion of the resistance toward the high potential end thereof. The test switch 23 is provided which is normally open and when closed shorts out resistances 17, 18 and 19 and places the chambers 10 and 11 directly across the power supply putting the unit into test alarm condition. This alarm condition provides a 100% component test equal to combustion products alarm. Chamber 10 is a reference chamber and the chamber 11 a sampling or signal chamber responsive to changes in the ambient atmosphere about the detector. The junction of the two chambers is connected to the gate of a field effect transistor 24, the gate being indicated at 25. Transistor 24 is of the insulated gate type and is an N-channel depletion mode metal oxide silicon field effect transistor. The transistor is connected across the direct current supply, its drain electrode being connected to the high potential side of the supply and its source electrode being connected to the low side through a resistance 26. When a change in combustion product density occurs in the ionized chamber 11, this change in density of the product decreases the current through the circuit of the chambers and increases the potential at the gate 25; as a result current flows through the transistor 24 and a control transistor 27 which has its base connected to the junction between the source of the transistor 24 and the resistance 26 conducts. The collector of the transistor 27 is connected to a circuit including a unijunction transistor 28 connected as an oscillator having its base-two connected to the high side of the D.C. source and its base-one connected to the collector through resistances 30 and 31 in series. A light emitting diode 32 is connected across the resistor 31. The emitter of the unijunction 28 is connected to the high side of the source by a resistance 33 and to the collector of the transistor 27 by a capacitance 34 thus completing the oscillator circuit. During operation of the oscillator the light emitting diode 32 flashes and indicates that the combustion product density is approaching alarm condition. As a predetermined further increase of the potential difference between the supply and the transistor 27, a Zener diode 35, connected in series with the winding of an alarm relay indicated at 36, conducts and the diode glows steadily. On a further increase of voltage difference, which in the alarm condition, the winding 36 is energized to actuate the relay and move a switch 37 to its upper position thereby connecting an alarm circuit 38 across the battery comprising the units 14 and 15. A unijunction transistor 40 is connected as an oscillator across the direct current source by resistances 41 and 42 and with its emitter connected to the common junction of a resistance 43 and capacitance 44. The base-one terminal of the unijunction 40 is connected through a diode 45 to the base-one terminal of a unijunction 46 which is connected to the high side of the source through a resistance 47, the base-two terminal being connected to the low side through a line 48. A resistance 50 and a capacitance 51 connected in series across the source have their common junction connected to the emitter of the unijunction 46, as indicated at 52, and complete the oscillator circuit. The unijunction transistor 46 is a lower frequency oscillator which acts as a "warbler" modifying the sound effect produced by the oscillation rate of the unijunction oscillator 40. The output of the oscillator 40 is supplied to the base of a transistor amplifier 53 through a resistance 54. The amplifier 53 when conducting energizes a winding 55 of a horn or loudspeaker 56 and the periodic output of the oscillator 40, modified at the lower rate by the oscillator 46, is reproduced as the warning sound by the horn 56.
In order to minimize drain on the battery 14 and 15 a diode 57 is connected in the emitter circuit of the transistor 27 which has been illustrated as connected to the common junction of the two battery sections. The diode 57 prevents reverse flow and drain from the battery 15.
The circuit of this invention makes it possible to calibrate the detectors by means of a simple D.C. voltmeter. When the transistor 27 is not conducting, the voltage between the test points, indicated at 60 and 61, is the same, however, when the transistor conducts the voltage increases with increase in the current through the transistor and hence through the resistances 30, 31 and 33 and the unijunction 28. This voltage varies directly with the density of the combustion product in the chamber 11 and is an indication of that density and may be used to monitor the performance of the detector. The maximum voltage between the test points 60 and 61 immediately prior to energization of the relay winding is an accurate indication of the calibration setting of the detector for alarm operation. This voltage may thus be used for calibrating the detector by adjustment of the potentiometers to obtain alarm operation at a preselected density of product in the chamber 11.
The alarm actuating voltage across the relay winding 36 and the Zener diode 35 in series is the same for all combustion product densities. The density of product at which the voltage is attained is determined by the setting of the potentiometer 17 which is the sensitivity control of the circuit. With no product in the chamber 11 the voltage across the test points is substantially zero. With a selected setting of the sensitivity potentiometer, the voltage between zero and the alarm voltage indicates the product density in the chamber 11. A D.C. voltmeter may thus be employed to determine the state of operation of the detector and also to calibrate the detector.
In initial calibration the potentiometers may be set for a fractional portion of the alarm density by subjecting the chamber 11 to product of such density and setting the potentiometer to the corresponding fractional setting of the voltage across the terminals 60 and 61. The detector will then operate to produce a voltage across the test terminals proportional to whatever density of product is present in the sampling chamber. By following these voltage measuring procedures, a large number of like detectors may be calibrated by calibrating a first detector using product densities in the chamber 11 to obtain the calibrations and corresponding voltages of the first detector, and then setting all other detectors accordingly and using voltages measured at the test terminals for this purpose. Thus, it is not necessary to use the samples of combustion product for calibration of the other detectors of like construction.
As an illustration of a working embodiment of the present invention and for purposes of example and not by way of limitation, a detector having a circuit connected as shown in the drawing and having the component values set forth below, operated successfully over an extended period of time and with a large number of operations due to the presence of combustion product in the test or sampling chamber 11. The chambers 10 and 11 were cylindrical, the chamber reference having a volume of about 0.8 cubic inches and the sampling chamber being about 25 percent larger.
The transistors were as follows: 24 field effect transistor MU-612, the unijunctions 28, 40 and 46 were all type 2N4871, diode 32 was a light emitting diode type NV10B, the control transistor 27 was a type 2N3643, the transistor 53 type 2N6099, the diodes 35 and 57 were type 1N4148, the Zener diode 35 was type 1N746A, the resistances were as follows:
17 and 19 one megohm
16-2 meghoms
18-390,000 ohms
33 and 43 - 10,000 ohms
26-82,000 ohms
31-1,000 ohms
50-12,000 ohms
30-220 ohms
41 and 47 - 180 ohms
42 and 54 - 150 ohms
The capacitors 35 and 51, 50 microfarads
44 - one-tenth microfarad
While the invention has been described in connection with a specific embodiment thereof, various modifications and applications will occur to those skilled in the art. Therefore, it is not desired that the invention be limited to the details illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.