CA1237505A - Detector apparatus of inflammable gas - Google Patents
Detector apparatus of inflammable gasInfo
- Publication number
- CA1237505A CA1237505A CA000402237A CA402237A CA1237505A CA 1237505 A CA1237505 A CA 1237505A CA 000402237 A CA000402237 A CA 000402237A CA 402237 A CA402237 A CA 402237A CA 1237505 A CA1237505 A CA 1237505A
- Authority
- CA
- Canada
- Prior art keywords
- detector element
- bridge circuit
- inflammable gas
- gas
- detector
- 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
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
- G08B17/117—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means by using a detection device for specific gases, e.g. combustion products, produced by the fire
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Emergency Alarm Devices (AREA)
- Control Of Combustion (AREA)
Abstract
ABSTRACT
In order to detect the presence of inflammable gas, a detector element is utilized consisting of a coil made with a thin wire of a platinum alloy, enclosed in a Davy cage, the detector is inserted in a resistor bridge circuit and the resistance of the detector changes according to the concen-tration of the inflammable gas so that above a predetermined concentration the bridge becomes unbalanced to such a degree as to give rise to an electric vol-tage signal having an amplitude proportional to the density (per cent) of gas present. This signal is utilized to electronically control an alarm and/or telesignaling and/or intervention device. A potentiometer resistor R3 inserted in the bridge circuit, permits the intervention threshold of detector element to be changed.
In order to detect the presence of inflammable gas, a detector element is utilized consisting of a coil made with a thin wire of a platinum alloy, enclosed in a Davy cage, the detector is inserted in a resistor bridge circuit and the resistance of the detector changes according to the concen-tration of the inflammable gas so that above a predetermined concentration the bridge becomes unbalanced to such a degree as to give rise to an electric vol-tage signal having an amplitude proportional to the density (per cent) of gas present. This signal is utilized to electronically control an alarm and/or telesignaling and/or intervention device. A potentiometer resistor R3 inserted in the bridge circuit, permits the intervention threshold of detector element to be changed.
Description
1~3750~i The invention relates to an apparatus for detecting inflammable gas.
It is known in both industrial and domestic use of combustible gases that the high degree of safety needed in the operating of plants is a technical problem of primary importance since it is necessary to minimize the possibility of a spill and consequent fires or injury to people and damage to property due to the toxicity of such inflammable gases.
Accordingly, prevention devices which are able to detect the pre-sence of dangerous concentrations of gas and, thus, control the operating of warning means or more complex emergency apparatus, are of particular importance especially when equipment using inflammable gas is operated in closed rooms.
It is clear that a high degree of sensitivity and operation reliability are the basic, constant characteristics that the detector device must present.
The detector apparatus of the present invention meets these requirements to a high standard; in addition, its electronic operation provides a quick and reliable response and great flexibility in use.
The sensing element used is essentially made up of a platinum alloy wire wound to form a closed coil which is able to change its electrical resis-tance as a function of the density (%) of inflammable gas surrounding the coil.
This sensing element, once inserted in a branch of the bridge circuit made up of resistors having constant resistance is able to derive control signals from the resistance variations which are due to the presence of traces of gas, for the control of electronic circuits which are provided to obtain an alarm or intervention.
The invention will now be described in greater detail with refer-ence to the accompanying drawing in which:
~3'7~
Figure 1 is a block diagram of an inflammable gas detector apparatus according to the invention; and Figure 2 is a circuit diagram of the detector apparatus of Figure 1.
Reduced to its basic structure and with reference to ~igure 1 of the accompanying drawings, the detector includes a power supply section including a mains feeder A provided with a rectification bridge transformer (shown in Figure 2) suitably stabilized by means of known electronic circuits.
The detector also includes a bridge circuit having resistors PM, a branch of which is made up of a detector element R for picking off the gas; the detector element is shaped as a coil consisting of a thin wire of platinum alloy enclosedin a cage of metallic net (~avy type) in order to prevent flame propagation in case of gas ignition around the coil.
Sucking and conveying means As for the ambient air to be controlled, including a sucking pump and canalization ducts for increasing the sensitivity of said detector element R are also provided.
A tone oscillator G and an electroacoustic transducer cascade connected are also provided.
More particularly, and according to a preferred embodiment of the invention as shown in ~igure 2, the mains feeder A is provided in order to obtain greater stability, with a transistor Tl, a Zener diode Zl and an inte-grated circuit ICl.
The bridge circuit PM is made up of two resistors R2 and R4 having constant resistance, a resistor R3 having a variable resistance and the above mentioned detector R. As can be seen R2 and R3 are connected in series to form one arm of the bridge and R4 and R are connected in series to form the other arm of the bridge. The junctions of R2 and R3 and of R4 and R are connected to the input terminals 2-3 of a differential amplifier Ad whose output 6 is ~237505 brought to the terminal ~ of an integrated circuit IC2 of the oscillator G
which operates as a generator of low frequency oscillations. The output 3 of integrated circuit IC2 is connected, through a capacitor C8 and a resistor R7 in series, to the above-mentioned electroacoustic device TA.
In order to avoid a possible fault in the apparatus operation owing to a power drop, an ancillary supply section Al (Figure 1) is provided includ-ing: a battery, buffer connected to the relevant automatic recharge circuit, a warning device for warning of mains power drop and battery break down and a timer circuit Tp providing for the activation of the ancillary supply section after a predetermined interruption the length of which may be adjusted to suit.
The operation of the device is as follows. In case of an increase of inflammable gas concentration around the sensor R, which brings about a resistance variation of sensor R, an electric voltage unbalance takes place between the terminàls 2 and 3 of the amplifier Ad; and this signal, suitably amplified, triggers the working of the oscillator G which, in turn, activates the transducer TA.
Such operating condition will be maintained throughout the time the sensor detects a gas percentage greater than the predetermined one. The predetermined percentage is set up as desired by adjusting variable resistors R3 to vary the intervention threshold i.e. the balance condition of the bridge.
Typical values of the essential components which are used in an embodiment of the invention are as follows:
Cl = 2000 ~P R5 = 10 Kohm C = C3 = C6 = C7 = 10 ~F R6 = 100 Kohm C4 = 0.1 ~F R7 = 22 Ohm 1/2 W
C8 = 100 ~F Tl = BC 140 ~7~37505 Rl = 470 Oh~ Zl = Zener 12 V/0.4 W
R2 = 220 Ohm Ad = llA741 R3 = 100 ~ 470 Ohm ICl = LM 340T5.0 R4 = 6. 8 Ohm IC2 = NE555
It is known in both industrial and domestic use of combustible gases that the high degree of safety needed in the operating of plants is a technical problem of primary importance since it is necessary to minimize the possibility of a spill and consequent fires or injury to people and damage to property due to the toxicity of such inflammable gases.
Accordingly, prevention devices which are able to detect the pre-sence of dangerous concentrations of gas and, thus, control the operating of warning means or more complex emergency apparatus, are of particular importance especially when equipment using inflammable gas is operated in closed rooms.
It is clear that a high degree of sensitivity and operation reliability are the basic, constant characteristics that the detector device must present.
The detector apparatus of the present invention meets these requirements to a high standard; in addition, its electronic operation provides a quick and reliable response and great flexibility in use.
The sensing element used is essentially made up of a platinum alloy wire wound to form a closed coil which is able to change its electrical resis-tance as a function of the density (%) of inflammable gas surrounding the coil.
This sensing element, once inserted in a branch of the bridge circuit made up of resistors having constant resistance is able to derive control signals from the resistance variations which are due to the presence of traces of gas, for the control of electronic circuits which are provided to obtain an alarm or intervention.
The invention will now be described in greater detail with refer-ence to the accompanying drawing in which:
~3'7~
Figure 1 is a block diagram of an inflammable gas detector apparatus according to the invention; and Figure 2 is a circuit diagram of the detector apparatus of Figure 1.
Reduced to its basic structure and with reference to ~igure 1 of the accompanying drawings, the detector includes a power supply section including a mains feeder A provided with a rectification bridge transformer (shown in Figure 2) suitably stabilized by means of known electronic circuits.
The detector also includes a bridge circuit having resistors PM, a branch of which is made up of a detector element R for picking off the gas; the detector element is shaped as a coil consisting of a thin wire of platinum alloy enclosedin a cage of metallic net (~avy type) in order to prevent flame propagation in case of gas ignition around the coil.
Sucking and conveying means As for the ambient air to be controlled, including a sucking pump and canalization ducts for increasing the sensitivity of said detector element R are also provided.
A tone oscillator G and an electroacoustic transducer cascade connected are also provided.
More particularly, and according to a preferred embodiment of the invention as shown in ~igure 2, the mains feeder A is provided in order to obtain greater stability, with a transistor Tl, a Zener diode Zl and an inte-grated circuit ICl.
The bridge circuit PM is made up of two resistors R2 and R4 having constant resistance, a resistor R3 having a variable resistance and the above mentioned detector R. As can be seen R2 and R3 are connected in series to form one arm of the bridge and R4 and R are connected in series to form the other arm of the bridge. The junctions of R2 and R3 and of R4 and R are connected to the input terminals 2-3 of a differential amplifier Ad whose output 6 is ~237505 brought to the terminal ~ of an integrated circuit IC2 of the oscillator G
which operates as a generator of low frequency oscillations. The output 3 of integrated circuit IC2 is connected, through a capacitor C8 and a resistor R7 in series, to the above-mentioned electroacoustic device TA.
In order to avoid a possible fault in the apparatus operation owing to a power drop, an ancillary supply section Al (Figure 1) is provided includ-ing: a battery, buffer connected to the relevant automatic recharge circuit, a warning device for warning of mains power drop and battery break down and a timer circuit Tp providing for the activation of the ancillary supply section after a predetermined interruption the length of which may be adjusted to suit.
The operation of the device is as follows. In case of an increase of inflammable gas concentration around the sensor R, which brings about a resistance variation of sensor R, an electric voltage unbalance takes place between the terminàls 2 and 3 of the amplifier Ad; and this signal, suitably amplified, triggers the working of the oscillator G which, in turn, activates the transducer TA.
Such operating condition will be maintained throughout the time the sensor detects a gas percentage greater than the predetermined one. The predetermined percentage is set up as desired by adjusting variable resistors R3 to vary the intervention threshold i.e. the balance condition of the bridge.
Typical values of the essential components which are used in an embodiment of the invention are as follows:
Cl = 2000 ~P R5 = 10 Kohm C = C3 = C6 = C7 = 10 ~F R6 = 100 Kohm C4 = 0.1 ~F R7 = 22 Ohm 1/2 W
C8 = 100 ~F Tl = BC 140 ~7~37505 Rl = 470 Oh~ Zl = Zener 12 V/0.4 W
R2 = 220 Ohm Ad = llA741 R3 = 100 ~ 470 Ohm ICl = LM 340T5.0 R4 = 6. 8 Ohm IC2 = NE555
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for detecting inflammable gas comprising in combination: a power supply section, a resistor bridge circuit, which includes a single gas detector element formed by a coil of platinum alloy wire the resistance of which varies according to the concentration of the inflammable gas, comparator means con-nected across the bridge circuit and arranged to provide a trig-ger signal when the bridge circuit becomes unbalanced due to the concentration of the inflammable gas in the vicinity of the gas detector element exceeding a predetermined threshold, a tone oscillator connected to the comparator means for actuation by the trigger signal and an electroacoustic transducer connected to the tone oscillator for actuation thereby.
2. Apparatus according to claim 1 wherein said coil of platinum alloy wire is enclosed in a Davy cage.
3. Apparatus according to claim 1 wherein said bridge cir-cuit includes a variable resistor for adjusting the balance condition of the bridge circuit, thereby to change the predeter-mined threshold of the detector element.
4. Apparatus according to claim 1 including means to convey ambient air onto the detector element.
5. Apparatus according to claim 1 wherein the power supply section comprises a primary supply section and an ancillary sup-ply section including a battery buffer connected to an automatic recharge circuit and a signaling device of mains drop and battery break down and a timer circuit to permit the intermittent opera-tion of the apparatus.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT09399/81A IT1167878B (en) | 1981-05-05 | 1981-05-05 | FLAMMABLE GAS DETECTOR |
| IT9399-A/81 | 1981-05-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1237505A true CA1237505A (en) | 1988-05-31 |
Family
ID=11129547
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402237A Expired CA1237505A (en) | 1981-05-05 | 1982-05-04 | Detector apparatus of inflammable gas |
Country Status (21)
| Country | Link |
|---|---|
| EP (1) | EP0065497B1 (en) |
| JP (2) | JPS57186160A (en) |
| AR (1) | AR228973A1 (en) |
| AT (1) | ATE15562T1 (en) |
| AU (2) | AU8322682A (en) |
| BR (1) | BR8202411A (en) |
| CA (1) | CA1237505A (en) |
| DE (1) | DE3266133D1 (en) |
| DK (1) | DK159167C (en) |
| ES (1) | ES8304343A1 (en) |
| FI (1) | FI75430C (en) |
| GR (1) | GR75842B (en) |
| IE (1) | IE52445B1 (en) |
| IL (1) | IL65497A0 (en) |
| IT (1) | IT1167878B (en) |
| MX (1) | MX151271A (en) |
| NO (1) | NO153236C (en) |
| NZ (1) | NZ200307A (en) |
| PT (1) | PT74843B (en) |
| YU (1) | YU44342B (en) |
| ZA (1) | ZA823039B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1198606B (en) * | 1983-05-17 | 1988-12-21 | Controfugas Srl | FLAMMABLE GAS DETECTOR APPARATUS WITH PRECONDITIONED INTERVENTION |
| JPS6071999U (en) * | 1983-10-21 | 1985-05-21 | 矢崎総業株式会社 | gas alarm |
| NO317999B3 (en) | 2002-06-28 | 2010-07-05 | Sts Gruppen As | Device for securing the operation of a habitat |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3221320A (en) * | 1961-04-13 | 1965-11-30 | Komyo Rikagaku Kogyo Kabushiki | Gas alarm circuit |
| US3482233A (en) * | 1967-04-13 | 1969-12-02 | Eastern Co | Gas detector system |
| BE788001A (en) * | 1971-11-01 | 1973-02-26 | T J Connelly Construction Cy I | SMOKE SENSITIVE CIRCUIT, WITH BACKUP BATTERY |
| IT951304B (en) * | 1972-04-11 | 1973-06-30 | Rimoldi V E C Spa | OCN SEWING MACHINE UPPER ROTEL WORK CONVEYOR THE ADJUSTABLE INDEPENDENTLY FROM THE LOWER JAW CONVEYOR |
| US3950739A (en) * | 1974-10-30 | 1976-04-13 | Campman James P | Detector for detecting and locating the source of a contaminating gas or smoke in the atmosphere |
| GB1474700A (en) * | 1974-12-16 | 1977-05-25 | Neotronics Ltd | Device for detecting and indicating the presence in a fluid environment of a potentially dangerous constituent |
| JPS51106674A (en) * | 1975-03-16 | 1976-09-21 | Masanori Mochizuki | BENDEINGUROORUKI |
| JPS5216987U (en) * | 1975-07-24 | 1977-02-05 | ||
| JPS5511496Y2 (en) * | 1975-11-17 | 1980-03-12 | ||
| JPS5433185U (en) * | 1977-08-09 | 1979-03-05 |
-
1981
- 1981-05-05 IT IT09399/81A patent/IT1167878B/en active
-
1982
- 1982-04-13 IL IL65497A patent/IL65497A0/en not_active IP Right Cessation
- 1982-04-15 NZ NZ200307A patent/NZ200307A/en unknown
- 1982-04-16 AR AR289119A patent/AR228973A1/en active
- 1982-04-26 AT AT82830111T patent/ATE15562T1/en not_active IP Right Cessation
- 1982-04-26 DK DK185582A patent/DK159167C/en not_active IP Right Cessation
- 1982-04-26 EP EP82830111A patent/EP0065497B1/en not_active Expired
- 1982-04-26 DE DE8282830111T patent/DE3266133D1/en not_active Expired
- 1982-04-27 BR BR8202411A patent/BR8202411A/en unknown
- 1982-04-28 JP JP57070574A patent/JPS57186160A/en active Pending
- 1982-04-28 ES ES511787A patent/ES8304343A1/en not_active Expired
- 1982-04-29 IE IE1010/82A patent/IE52445B1/en not_active IP Right Cessation
- 1982-05-03 MX MX192553A patent/MX151271A/en unknown
- 1982-05-03 AU AU83226/82A patent/AU8322682A/en not_active Abandoned
- 1982-05-03 NO NO821461A patent/NO153236C/en unknown
- 1982-05-04 CA CA000402237A patent/CA1237505A/en not_active Expired
- 1982-05-04 GR GR68058A patent/GR75842B/el unknown
- 1982-05-04 PT PT74843A patent/PT74843B/en not_active IP Right Cessation
- 1982-05-04 ZA ZA823039A patent/ZA823039B/en unknown
- 1982-05-04 YU YU945/82A patent/YU44342B/en unknown
- 1982-05-05 FI FI821569A patent/FI75430C/en not_active IP Right Cessation
-
1988
- 1988-06-27 AU AU18433/88A patent/AU1843388A/en not_active Abandoned
-
1990
- 1990-10-19 JP JP1990109076U patent/JPH0424439Y2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0065497B1 (en) | 1985-09-11 |
| IT8109399A0 (en) | 1981-05-05 |
| FI75430B (en) | 1988-02-29 |
| FI75430C (en) | 1988-06-09 |
| NZ200307A (en) | 1985-05-31 |
| MX151271A (en) | 1984-10-29 |
| JPH0424439Y2 (en) | 1992-06-09 |
| AU1843388A (en) | 1988-09-22 |
| IE52445B1 (en) | 1987-10-28 |
| FI821569A0 (en) | 1982-05-05 |
| AR228973A1 (en) | 1983-05-13 |
| ZA823039B (en) | 1983-03-30 |
| NO153236B (en) | 1985-10-28 |
| DK159167B (en) | 1990-09-10 |
| ES511787A0 (en) | 1983-02-16 |
| EP0065497A1 (en) | 1982-11-24 |
| PT74843B (en) | 1983-12-02 |
| DK159167C (en) | 1991-02-11 |
| IL65497A0 (en) | 1982-07-30 |
| DK185582A (en) | 1982-11-06 |
| IT1167878B (en) | 1987-05-20 |
| FI821569L (en) | 1982-11-06 |
| IE821010L (en) | 1982-11-05 |
| YU44342B (en) | 1990-06-30 |
| JPH0374352U (en) | 1991-07-25 |
| DE3266133D1 (en) | 1985-10-17 |
| JPS57186160A (en) | 1982-11-16 |
| NO821461L (en) | 1982-11-08 |
| PT74843A (en) | 1982-06-01 |
| NO153236C (en) | 1986-02-05 |
| AU8322682A (en) | 1982-11-11 |
| GR75842B (en) | 1984-08-02 |
| ES8304343A1 (en) | 1983-02-16 |
| ATE15562T1 (en) | 1985-09-15 |
| YU94582A (en) | 1985-03-20 |
| BR8202411A (en) | 1983-04-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |