CA1070798A - Flame detecting apparatus - Google Patents
Flame detecting apparatusInfo
- Publication number
- CA1070798A CA1070798A CA239,077A CA239077A CA1070798A CA 1070798 A CA1070798 A CA 1070798A CA 239077 A CA239077 A CA 239077A CA 1070798 A CA1070798 A CA 1070798A
- Authority
- CA
- Canada
- Prior art keywords
- flame
- electrode
- detecting
- auxiliary electrode
- detecting apparatus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
- F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
- Control Of Combustion (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE.
A flame detecting apparatus comprises. a flame detecting electrode and an auxiliary electrode both of which are in use disposed in a flame, and means to bias the auxiliary electrode to a DC potential different from that of the detecting electrode.
A flame detecting apparatus comprises. a flame detecting electrode and an auxiliary electrode both of which are in use disposed in a flame, and means to bias the auxiliary electrode to a DC potential different from that of the detecting electrode.
Description
BACKGROUND OF THE INVENTION
. Field of the _invention .
Thi-~ invention relates. to a ~lame detecting apparatu.~, more paraticulary to a novel- flame detecting apparatus in which a flame detecting electrode and an.auxiliary electrode are disposed in a flame.
.
. DESCRIPTION OF THE PRIOR ART
. .
In many application~ domestic, commercial a~d industrial, flame combustion of a fuel is used as a source of heat. It is e~sential, in the intere~ts o~ ~afety, that there should at no time !
1C~7~
.
be an accwnulation of unburnt gases in the combustion chamber (such as will occur on flame failure) which may be accidentally ignited and cause an explosion. Therefore, it is necessary to have some means for detecting and giving an indication of flame failure, the means preferably stopping the supply of fuel to the combustion chamber. Many types of flame detector are available to indicate flame failure and prevent the build-up of this potentially hazardous condition. These flame detectors are usually based on one of the following principles:
.O 1) thermostat e~fect;
. Field of the _invention .
Thi-~ invention relates. to a ~lame detecting apparatu.~, more paraticulary to a novel- flame detecting apparatus in which a flame detecting electrode and an.auxiliary electrode are disposed in a flame.
.
. DESCRIPTION OF THE PRIOR ART
. .
In many application~ domestic, commercial a~d industrial, flame combustion of a fuel is used as a source of heat. It is e~sential, in the intere~ts o~ ~afety, that there should at no time !
1C~7~
.
be an accwnulation of unburnt gases in the combustion chamber (such as will occur on flame failure) which may be accidentally ignited and cause an explosion. Therefore, it is necessary to have some means for detecting and giving an indication of flame failure, the means preferably stopping the supply of fuel to the combustion chamber. Many types of flame detector are available to indicate flame failure and prevent the build-up of this potentially hazardous condition. These flame detectors are usually based on one of the following principles:
.O 1) thermostat e~fect;
2) action of light sensitive thermionic tubes; and
3) electrical properties of flame gases.
The flame detectors based on either of the first principles are subject to fundamental problem~. Th~rmostats hav~ ~ slow response time because of the finite time between flame failure and the detection of cooling which gives an indication of the flame failure.
On the other hand, light sensitive thermionic tubes require delicate and expensive amplifying means. These devices also require accompa-nying fault detection equipment to ensure that they are operating O properly.
The third principle on which flame detectors have been based involves making use of the electrical properties inherent in flame gases, for example elec~rical conductivity or rectification;
A flame detector using the electrical conductivity or rectification action of a flame has a ~oltage of several hundred volts AC applied between a flame detecting electrode and a burner, and a minute current which is caused to flow through the flame between the detecting electrode and the burner is amplified by an amplifier circuit of high input impedance which employs a field-effect tran-0 sistor or the like. Alternatively, a light emitting device, such as a neon tube, is caused to emit light by the use of the minute current, and a photo-conductive device is operated by the emitted light. The applied voltage may, for example be 250 volts AC, with the detected current only being some 4 microamps.
In another type of flame detector using the third prin-ciple, only the detecting electrode inserted into the flame is used. This type uses the fact -that some of the atoms or mole-cules in a flame are thermally ionized by the high temperature, that is, there are many positive ions of H30+ in the top region of the flame and many negative ions of Hor in the bottom region of the flame. Also many electrons produced by the the~mal ioniza-tion are present in the middle region of the flame. I~ may be said, therefore that the flame is an electrical conductor, al-though with a very large impedance. When an electrocle is dis-posed in the flame, the electrons are caught by the electrode one by one, so that a current flows through the flame, the elec-trode being charged to negative potential. This negatlve poten-tial is used as a detecting signal. However, generally, the detecting voltage is very small, for example, 0.6 to 0.8 volts, and the current is also very small, for example 50 to 120 nano-amps.
With the known flame detectors therefore a quick and reliable response cannot be obtained, because the detecting sig-nals are so small.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a flame detecting apparatus which is free from the disadvantages of the known apparatus described above.
Another object of the invention is to provide a flame detecting apparatus in which a detecting and an auxiliary elec-trode are disposed in a flame, and one of electrodes in biased ., .
7~
to a DC potential different from tha-t of the other electrode.
Still another object of the invention is to provide a flame detecting apparatus in which a detecting and an aux~
iliary electrode are disposed in a flame, and a negative biasing means is connected to the auxiliary electrode, whereby certain flame detection and quick response are obtained.
Still anoth~r object of the invention is to provide a flame detecting apparatus in which a detecting andan aux-iliary electrode are disposed in a flame, and a biasing means is provided such that the DC potential of the detecting elec-trode is higher than that of the auxiliary electrode, whereby a relatively large detecting voltage and current is obtained.
More particularly, there is provided: flame detecting apparatus comprising a detecting electrode disposed in a flame position; an auxiliary electrode disposed in said flame position ?
at a spacing from said detecting electrode; first means for biasing said detecting electrode and said auxiliary electrode with different DC potentials; and secand means to derive a signal from said detecting electrode which signal indicates whether a flame is present in said flame position or not, where-in said first means energizes said auxiliary electrode with a positive potential relative to said detecting electrode.
~et another object of the invention is to provide a ; flame detecting apparatus in which two electrodes are disposed , in a flame, and a biasing voltage source is provided, so that the flame detecting apparatus is easily constructed and a stable output is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
.
Further objects, features and advantages of the inven-tion will become apparent from the following description given by way of example, with reference to the accompanying drawings, ; in which: ;;;
X, - ~L - '~ ' " "' . ':, ~, ~' ~ :
1~37(J7~3 Figures 1 and 2 are diagrammatic views respectively of first and second embodimen-ts o~ the invention;
Figures 3 and 4 are graphs of detected voltages and current plotted against gas flow for the first and second embodiments re-spectively; . .
Figures 5 and 6 are diagrammatic views respectively of third and fourth embodiments of the invention; and Figure 7 is a diagrammatic view with a block diagram of a fifth embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENTS
-Referring now to the drawings, Figure 1 shows a Elame detecting apparatus in which a detecting electrode 1 is disposed in a flame 2 from a grounded burner 3. An auxiliary electrode 4 is also disposed in the flame 2, but positioned below the de-tecting electrode 1. The DC potential of the detecting elec-trode 1 is maintained higher than that of the auxiliary elec-; trode 4, the auxiliary electrode 4 being biased to a negative potential by a DC voltage source 5. An indicator such as a volt-meter 6, or an ammeter, is connected between the detecting elec-trode 1 and ground.
Some of the atoms or molecules in the flame 2 are thermally ionized by the high temperature, so there are many positive ions of H30+ which have lost electrons in the top ;~
region of the flame 2 and many negative ions of HO in the bottom region of the flame 2. Also, there are many electr~ns el pro-duced by the thermal ionization in the middle region of the flame : 2. The electrons el are caught by the detecting electrode 1 .
- 4a -. ~ ' , ' 7~7~
so that a current Il flows through the flame 2 :Erom the elec-trode 1 to the burner 3, which means that the detecting elec-trode 1 is charged to a negative potential. Also, since the auxiliary electrode 4 is substantially heated by the flame 2,~
many thermal electrons e2~ are discharged therefrom, and are caught by -the detecting electrode 1. Thus, a second current I2 flows through the flame 2 from the detecting electrode 1 to the axuiliary electrode 4, so -the detecting electrode 1 is still further charged to a negative potential. Thus a large current flows through flame 2 and a large voltage is developed at the detecting electrode 1.
Figure 2 shows a second embodiment. In this case, detecting and auxiliary electrodes 11 and 14 are disposed in a flame 12 as in the first embodiment, but the de:tectlng electrode 11 is positioned under the auxiliary electrode 14, which is biased with a negative potential relati.ve to the detecting electrode 11 by a DC voltage source 15. Numerals 13 and 16 ~:~
designate the burner and an indicator, respectively.
Figure 3 shows graphs of the detected negative volt~
age plotted against the gas flow in litres per minute with a constant air supply for the first and second embodiments shown in Figures 1 and 2. Curves (a), (b) and (c) show changes of detected voltage when the source 5 (Figure 1) has various volt-ages (E), namely; E = -40, -30 and -20 volts. Curves (d), (e), (f), (g) and (h) show changes of detected voltage when the :
; source 15 (Figure 2) has various voltages (E), namely; E = -50, ~ ~.
-40, -30, ~20 and -10 volts. Additionally, a curve (i) shows changes of a detected voltage in a prior art apparatus in which only the detecting electrode is inserted into a flame.
Figure 4 shows graphs of the detected current plotted against the gas flow for the first and second embodiments.
; . . .
. , .
79~3 Curves (b), (d), (e), (f), (g), (h) and (i) correspond to curves (b), (d), (e), (f), (g), (h) and (i) in Figure 3. It can be seen from the curves (b) shown in F:igures 3 and 4, that when -30 volts is applied to the auxiliary electrode 4 in the first embodiment, -16 volts and 17 microamps is detected.
Similarly, curves (d) shown in Figures 3 and 4, show that when -50 volts is applied to the auxiliary electrode 14 of the second embodiment, -15.5 volts and 13.8 microamps is detected.
Thus, the detected voltage and current are very large compared with those shown by the curve (i) for the prior art apparatus.
As shown in Figures 3 and 4, the detected voltage and current with the first embodiment in which the auxiliary electrode 4 is placed under the detecting electrode l are larger than those obtained wi-th the second embodiment. It is thought that, in the first embodiment oE Figure 1, two kinds of electrons el and e2 flow towards the top region of the flame 2. That is, both kinds of electrons el and e2 flow easily towards the positive ions which exist in the top region of the flame 2, and are assisted by the flow of gases from the bot-tom to the top of the flame 2.
Figure 5 shows a third embodiment. Detecting elec-trode 21 and auxiliary electrode 24 are disposed in a flame 22.
The auxiliary electrode 24 is disposed under the detecting electrode 21, but is energized by a positive voltage source 25.
Numerals 23 and 26 designate the burner and an indicator, respectively. In this embodiment, when +30 vol-ts is applied to the auxiliary electrode 24, -~3 volts is detected at and 0.5 microamps flows to the detecting electrode 21 with a gas flow of 13 litres per minute.
Figure 6 shows a fourth embodiment. In this case, an auxiliary electrode 34 is positioned above a de-tecting electrode 7~313 31 and is energized by a positive voltage source 35. An indicator 36 is provided. When the auxiliary electrode 34 is biased with +30 volts, -~4 vol-ts is detected atSand 0.5 microamps flow to the detecting electrode 31~
Thus, in the third and fourth embodiments, a low positive voltage is detected at the respective detecting elec-trodes. It isthought that, in the third embodiment shown in Figure 5, the detecting electrode 21 is charged with negative potential as mentioned above, but orl the other hand, a current I2 flows through the flame 22 from the auxiliary elec-trode 24 to the detecting electrode 21, as indicated, due -to the positive source 25, so that a positive potential is developed at the detecting electrode 21. This positive potent:ial over-comes the above-mentioned negative potential, so that a small positive potential appears at the detecting electrode 21.
A preferred ma-terial for the detecting electrode ;;
comprises 0.1% barium, 0.2% magnesium, 0O1% carbon and the balance nickel. It is possible to use more than one element, having work function less than 3 eV from group IIa of the periodic table, for example, magnesium, calcium, strontium or barium. The work functions of all these elements is less -than 3 eV, so an electrode comprising one or more of these elements can easily gather the electrons el~ produced by thermal ionization, so that a substantial negative potential is developed at the detecting electrode. Other examp].es of materials for a detecting electrode are as follows~
1. Chromium 12 to 15%, silicon less than 0.5%, carbon :,~ .
less than 0.15%, strontium 0.1%, copper 0.1% and the balance nickel.
2. Chromium 23%, aluminium 6%, cobalt 2%, carbon less than 0.1%, strontium 0.1% and the balance iron.
7~37~l3 3. Chromium 18%, nickel 8~, silicon less than 1%, man-ganese less than 2~, carbon less than 0.03%, stronium 1%, calcium 1% and the balance iron. All the above percentages are by weight.
Figure 7 shows a fifth embodiment. In this case, detecting and auxiliary electrodes 41 and 4L4 are disposed in a flame 42 from a burner 43, the auxiliary electrode 44 being biased with a negative potential by a negative DC voltage source 45. In this embodiment, an additional biasing source 47 is connected to the detecting electrode 41 so as to bias ~he detecting electrode 41 with a positlve DC potential. With this embodiment a large detected signal is obtained and is applied to an amplifier 48, the output of which is supplied to a drive circuit 49 which may include a suitable switching element and relay. The outpu-t oE the drive circuit 49 controls a valve 50 in a gas supply pipe 51. If the flame 42 goes out, no output is applied to the valve 50 and no gas is supplied to burner 43.
Although described in relation to a gas flame, the invention can of course be used with flames produced by other ~uels.
Moreover, other modifications and variations will be apparent to those skilled in the art and are included in the scope of the invention which is defined by -the appended claims.
The flame detectors based on either of the first principles are subject to fundamental problem~. Th~rmostats hav~ ~ slow response time because of the finite time between flame failure and the detection of cooling which gives an indication of the flame failure.
On the other hand, light sensitive thermionic tubes require delicate and expensive amplifying means. These devices also require accompa-nying fault detection equipment to ensure that they are operating O properly.
The third principle on which flame detectors have been based involves making use of the electrical properties inherent in flame gases, for example elec~rical conductivity or rectification;
A flame detector using the electrical conductivity or rectification action of a flame has a ~oltage of several hundred volts AC applied between a flame detecting electrode and a burner, and a minute current which is caused to flow through the flame between the detecting electrode and the burner is amplified by an amplifier circuit of high input impedance which employs a field-effect tran-0 sistor or the like. Alternatively, a light emitting device, such as a neon tube, is caused to emit light by the use of the minute current, and a photo-conductive device is operated by the emitted light. The applied voltage may, for example be 250 volts AC, with the detected current only being some 4 microamps.
In another type of flame detector using the third prin-ciple, only the detecting electrode inserted into the flame is used. This type uses the fact -that some of the atoms or mole-cules in a flame are thermally ionized by the high temperature, that is, there are many positive ions of H30+ in the top region of the flame and many negative ions of Hor in the bottom region of the flame. Also many electrons produced by the the~mal ioniza-tion are present in the middle region of the flame. I~ may be said, therefore that the flame is an electrical conductor, al-though with a very large impedance. When an electrocle is dis-posed in the flame, the electrons are caught by the electrode one by one, so that a current flows through the flame, the elec-trode being charged to negative potential. This negatlve poten-tial is used as a detecting signal. However, generally, the detecting voltage is very small, for example, 0.6 to 0.8 volts, and the current is also very small, for example 50 to 120 nano-amps.
With the known flame detectors therefore a quick and reliable response cannot be obtained, because the detecting sig-nals are so small.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a flame detecting apparatus which is free from the disadvantages of the known apparatus described above.
Another object of the invention is to provide a flame detecting apparatus in which a detecting and an auxiliary elec-trode are disposed in a flame, and one of electrodes in biased ., .
7~
to a DC potential different from tha-t of the other electrode.
Still another object of the invention is to provide a flame detecting apparatus in which a detecting and an aux~
iliary electrode are disposed in a flame, and a negative biasing means is connected to the auxiliary electrode, whereby certain flame detection and quick response are obtained.
Still anoth~r object of the invention is to provide a flame detecting apparatus in which a detecting andan aux-iliary electrode are disposed in a flame, and a biasing means is provided such that the DC potential of the detecting elec-trode is higher than that of the auxiliary electrode, whereby a relatively large detecting voltage and current is obtained.
More particularly, there is provided: flame detecting apparatus comprising a detecting electrode disposed in a flame position; an auxiliary electrode disposed in said flame position ?
at a spacing from said detecting electrode; first means for biasing said detecting electrode and said auxiliary electrode with different DC potentials; and secand means to derive a signal from said detecting electrode which signal indicates whether a flame is present in said flame position or not, where-in said first means energizes said auxiliary electrode with a positive potential relative to said detecting electrode.
~et another object of the invention is to provide a ; flame detecting apparatus in which two electrodes are disposed , in a flame, and a biasing voltage source is provided, so that the flame detecting apparatus is easily constructed and a stable output is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
.
Further objects, features and advantages of the inven-tion will become apparent from the following description given by way of example, with reference to the accompanying drawings, ; in which: ;;;
X, - ~L - '~ ' " "' . ':, ~, ~' ~ :
1~37(J7~3 Figures 1 and 2 are diagrammatic views respectively of first and second embodimen-ts o~ the invention;
Figures 3 and 4 are graphs of detected voltages and current plotted against gas flow for the first and second embodiments re-spectively; . .
Figures 5 and 6 are diagrammatic views respectively of third and fourth embodiments of the invention; and Figure 7 is a diagrammatic view with a block diagram of a fifth embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENTS
-Referring now to the drawings, Figure 1 shows a Elame detecting apparatus in which a detecting electrode 1 is disposed in a flame 2 from a grounded burner 3. An auxiliary electrode 4 is also disposed in the flame 2, but positioned below the de-tecting electrode 1. The DC potential of the detecting elec-trode 1 is maintained higher than that of the auxiliary elec-; trode 4, the auxiliary electrode 4 being biased to a negative potential by a DC voltage source 5. An indicator such as a volt-meter 6, or an ammeter, is connected between the detecting elec-trode 1 and ground.
Some of the atoms or molecules in the flame 2 are thermally ionized by the high temperature, so there are many positive ions of H30+ which have lost electrons in the top ;~
region of the flame 2 and many negative ions of HO in the bottom region of the flame 2. Also, there are many electr~ns el pro-duced by the thermal ionization in the middle region of the flame : 2. The electrons el are caught by the detecting electrode 1 .
- 4a -. ~ ' , ' 7~7~
so that a current Il flows through the flame 2 :Erom the elec-trode 1 to the burner 3, which means that the detecting elec-trode 1 is charged to a negative potential. Also, since the auxiliary electrode 4 is substantially heated by the flame 2,~
many thermal electrons e2~ are discharged therefrom, and are caught by -the detecting electrode 1. Thus, a second current I2 flows through the flame 2 from the detecting electrode 1 to the axuiliary electrode 4, so -the detecting electrode 1 is still further charged to a negative potential. Thus a large current flows through flame 2 and a large voltage is developed at the detecting electrode 1.
Figure 2 shows a second embodiment. In this case, detecting and auxiliary electrodes 11 and 14 are disposed in a flame 12 as in the first embodiment, but the de:tectlng electrode 11 is positioned under the auxiliary electrode 14, which is biased with a negative potential relati.ve to the detecting electrode 11 by a DC voltage source 15. Numerals 13 and 16 ~:~
designate the burner and an indicator, respectively.
Figure 3 shows graphs of the detected negative volt~
age plotted against the gas flow in litres per minute with a constant air supply for the first and second embodiments shown in Figures 1 and 2. Curves (a), (b) and (c) show changes of detected voltage when the source 5 (Figure 1) has various volt-ages (E), namely; E = -40, -30 and -20 volts. Curves (d), (e), (f), (g) and (h) show changes of detected voltage when the :
; source 15 (Figure 2) has various voltages (E), namely; E = -50, ~ ~.
-40, -30, ~20 and -10 volts. Additionally, a curve (i) shows changes of a detected voltage in a prior art apparatus in which only the detecting electrode is inserted into a flame.
Figure 4 shows graphs of the detected current plotted against the gas flow for the first and second embodiments.
; . . .
. , .
79~3 Curves (b), (d), (e), (f), (g), (h) and (i) correspond to curves (b), (d), (e), (f), (g), (h) and (i) in Figure 3. It can be seen from the curves (b) shown in F:igures 3 and 4, that when -30 volts is applied to the auxiliary electrode 4 in the first embodiment, -16 volts and 17 microamps is detected.
Similarly, curves (d) shown in Figures 3 and 4, show that when -50 volts is applied to the auxiliary electrode 14 of the second embodiment, -15.5 volts and 13.8 microamps is detected.
Thus, the detected voltage and current are very large compared with those shown by the curve (i) for the prior art apparatus.
As shown in Figures 3 and 4, the detected voltage and current with the first embodiment in which the auxiliary electrode 4 is placed under the detecting electrode l are larger than those obtained wi-th the second embodiment. It is thought that, in the first embodiment oE Figure 1, two kinds of electrons el and e2 flow towards the top region of the flame 2. That is, both kinds of electrons el and e2 flow easily towards the positive ions which exist in the top region of the flame 2, and are assisted by the flow of gases from the bot-tom to the top of the flame 2.
Figure 5 shows a third embodiment. Detecting elec-trode 21 and auxiliary electrode 24 are disposed in a flame 22.
The auxiliary electrode 24 is disposed under the detecting electrode 21, but is energized by a positive voltage source 25.
Numerals 23 and 26 designate the burner and an indicator, respectively. In this embodiment, when +30 vol-ts is applied to the auxiliary electrode 24, -~3 volts is detected at and 0.5 microamps flows to the detecting electrode 21 with a gas flow of 13 litres per minute.
Figure 6 shows a fourth embodiment. In this case, an auxiliary electrode 34 is positioned above a de-tecting electrode 7~313 31 and is energized by a positive voltage source 35. An indicator 36 is provided. When the auxiliary electrode 34 is biased with +30 volts, -~4 vol-ts is detected atSand 0.5 microamps flow to the detecting electrode 31~
Thus, in the third and fourth embodiments, a low positive voltage is detected at the respective detecting elec-trodes. It isthought that, in the third embodiment shown in Figure 5, the detecting electrode 21 is charged with negative potential as mentioned above, but orl the other hand, a current I2 flows through the flame 22 from the auxiliary elec-trode 24 to the detecting electrode 21, as indicated, due -to the positive source 25, so that a positive potential is developed at the detecting electrode 21. This positive potent:ial over-comes the above-mentioned negative potential, so that a small positive potential appears at the detecting electrode 21.
A preferred ma-terial for the detecting electrode ;;
comprises 0.1% barium, 0.2% magnesium, 0O1% carbon and the balance nickel. It is possible to use more than one element, having work function less than 3 eV from group IIa of the periodic table, for example, magnesium, calcium, strontium or barium. The work functions of all these elements is less -than 3 eV, so an electrode comprising one or more of these elements can easily gather the electrons el~ produced by thermal ionization, so that a substantial negative potential is developed at the detecting electrode. Other examp].es of materials for a detecting electrode are as follows~
1. Chromium 12 to 15%, silicon less than 0.5%, carbon :,~ .
less than 0.15%, strontium 0.1%, copper 0.1% and the balance nickel.
2. Chromium 23%, aluminium 6%, cobalt 2%, carbon less than 0.1%, strontium 0.1% and the balance iron.
7~37~l3 3. Chromium 18%, nickel 8~, silicon less than 1%, man-ganese less than 2~, carbon less than 0.03%, stronium 1%, calcium 1% and the balance iron. All the above percentages are by weight.
Figure 7 shows a fifth embodiment. In this case, detecting and auxiliary electrodes 41 and 4L4 are disposed in a flame 42 from a burner 43, the auxiliary electrode 44 being biased with a negative potential by a negative DC voltage source 45. In this embodiment, an additional biasing source 47 is connected to the detecting electrode 41 so as to bias ~he detecting electrode 41 with a positlve DC potential. With this embodiment a large detected signal is obtained and is applied to an amplifier 48, the output of which is supplied to a drive circuit 49 which may include a suitable switching element and relay. The outpu-t oE the drive circuit 49 controls a valve 50 in a gas supply pipe 51. If the flame 42 goes out, no output is applied to the valve 50 and no gas is supplied to burner 43.
Although described in relation to a gas flame, the invention can of course be used with flames produced by other ~uels.
Moreover, other modifications and variations will be apparent to those skilled in the art and are included in the scope of the invention which is defined by -the appended claims.
Claims (4)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Flame detecting apparatus comprising a detecting electrode disposed in a flame position; an auxiliary electrode disposed in said flame position at a spacing from said detecting electrode; first means for biasing said detecting electrode and said auxiliary electrode with different DC potentials; and second means to derive a signal from said detecting electrode which signal indicates whether a flame is present in said flame position or not, wherein said first means energizes said auxil-iary electrode with a positive potential relative to said de-tecting electrode.
2. A flame detecting apparatus according to claim 1, in which said auxiliary electrode is positioned under said de-tecting electrode.
3. A flame detecting apparatus according to claim 2, in which said auxiliary electrode is positioned above said de-tecting electrode.
4. A flame detecting apparatus according to claim 1, in which said detecting electrode comprises a material including at least one element from group IIa of the periodic table, which element has a work function of less than 3 eV.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP49131375A JPS5739381B2 (en) | 1974-11-14 | 1974-11-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070798A true CA1070798A (en) | 1980-01-29 |
Family
ID=15056459
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA239,077A Expired CA1070798A (en) | 1974-11-14 | 1975-11-05 | Flame detecting apparatus |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5739381B2 (en) |
| AU (1) | AU501742B2 (en) |
| CA (1) | CA1070798A (en) |
| DE (1) | DE2550881A1 (en) |
| FR (1) | FR2291494A1 (en) |
| GB (1) | GB1499446A (en) |
| NL (1) | NL7513265A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3979689A (en) | 1975-01-29 | 1976-09-07 | Rca Corporation | Differential amplifier circuit |
| DE2847154A1 (en) * | 1978-10-30 | 1980-05-08 | Rowenta Werke Gmbh | BATTERY LIGHTER WITH AUTOMATIC SWITCHING OFF OF THE IGNITION DEVICE |
| JPS59160791A (en) * | 1983-03-04 | 1984-09-11 | Citizen Watch Co Ltd | Gear train structure of electronic watch |
| DE19932546A1 (en) * | 1999-07-13 | 2001-01-25 | Bosch Gmbh Robert | Gas burner |
-
1974
- 1974-11-14 JP JP49131375A patent/JPS5739381B2/ja not_active Expired
-
1975
- 1975-11-05 CA CA239,077A patent/CA1070798A/en not_active Expired
- 1975-11-11 GB GB4654475A patent/GB1499446A/en not_active Expired
- 1975-11-12 DE DE19752550881 patent/DE2550881A1/en not_active Withdrawn
- 1975-11-12 NL NL7513265A patent/NL7513265A/en not_active Application Discontinuation
- 1975-11-14 FR FR7534857A patent/FR2291494A1/en active Granted
- 1975-11-16 AU AU86598/75A patent/AU501742B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2291494A1 (en) | 1976-06-11 |
| DE2550881A1 (en) | 1976-05-20 |
| GB1499446A (en) | 1978-02-01 |
| JPS5156694A (en) | 1976-05-18 |
| JPS5739381B2 (en) | 1982-08-20 |
| FR2291494B1 (en) | 1981-09-25 |
| NL7513265A (en) | 1976-05-18 |
| AU501742B2 (en) | 1979-06-28 |
| AU8659875A (en) | 1977-05-19 |
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