US3750123A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Smoke sensing circuit with battery standby
Assignee: T J CONNELLY CONSTR CO Inc
•
Filing: 1971-11-01
•
Granted: 1973-07-31
•
Expires: 1991-11-01
Abstract
Abstract A fire and gas alarm system utilizing a four-terminal sensing device positioned in the environmental region to be monitored. The sensing device includes a pair of resistance heating wires spaced apart by a conducting core and encompassed by an outer metallic shell. A transformer powers a pair of rectifiers which supply current to both a normally operated standby relay and the four-terminal smoke and gas sensing device. When hydrocarbon vapors or smoke impinges upon the metallic shell of the sensing device, the resistance between the pair of heater wires drops to operate a relay and produce an alarm indication. Upon failure of a.c. power, the standby relay is released to connect battery power to the circuit and insure continued operation in response to an alarm condition.
Inventors
- 👤 L Caillouet
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:53
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/117
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
302 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer metallic shell, the resistance between said wires being decreased when vaporous hydrocarbons or smoke are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said first secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; a pair of rectifiers connected to the second of said transformer secondary windings, the output of the first rectifier being connected to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay, actuated by the output of the second rectifier of said pair and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing unit; an alarm relay having a set of normally open contacts; a transistor connected in a common emitter configuration having its base electrode coupled to the first of said resistance heating wires and its collector electrode connected through the winding of said alarm relay to the output of said second rectifier; an alarm buzzer connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at the base electrode of said transistor sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm buzzer signal.
Claim 2
Dependent Claim
302 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer metallic shell, the resistance between said wires being decreased when vaporous hydrocarbons or smoke are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said first secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; a pair of rectifiers connected to the second of said transformer secondary windings, the output of the first rectifier being connected to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay, actuated by the output of the second rectifier of said pair and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing unit; an alarm relay having a set of normally open contacts; a transistor connected in a common emitter configuration having its base electrode coupled to the first of said resistance heating wires and its collector electrode connected through the winding of said alarm relay to the output of said second rectifier; an alarm buzzer connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at the base electrode of said transistor sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm buzzer signal.
Claim 3
Dependent Claim
297 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer metallic shell, the resistance between at least one of said wires being decreased when vaporous hydrocarbons or smoke Are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said first secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; a pair of rectifiers connected to the second of said transformer secondary windings, the output of the first rectifier being connected to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay, actuated by the output of the second rectifier of said pair and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing device; an alarm relay having a set of normally open contacts; transistor switch means having an electrode coupled to the first of said resistance heating wires and a second electrode coupled through the winding of said alarm relay to the output of said second rectifier; and an alarm connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at said transistor switch means sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm signal.
Claim 4
Dependent Claim
297 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer metallic shell, the resistance between at least one of said wires being decreased when vaporous hydrocarbons or smoke Are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said first secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; a pair of rectifiers connected to the second of said transformer secondary windings, the output of the first rectifier being connected to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay, actuated by the output of the second rectifier of said pair and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing device; an alarm relay having a set of normally open contacts; transistor switch means having an electrode coupled to the first of said resistance heating wires and a second electrode coupled through the winding of said alarm relay to the output of said second rectifier; and an alarm connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at said transistor switch means sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm signal.
Claim 5
Dependent Claim
288 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer shell, the resistance between at least one of said wires being decreased when vaporous hydrocarbons or smoke are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; rectifier circuitry connected to the second of said transformer secondary windings and to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay connected to said rectifier circuitry and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing device; an alarm relay having a set of normally open contacts; a transistor connected in a common emitter configuration having its base electrode coupled to the first of said resistance heating wires and its collector electrode connected through the winding of said alarm relay to the output of said rectifier circuitry; and an alarm connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at the base electrode of said transistor sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm signal.
Claim 6
Dependent Claim
288 words
A fire and gas alarm system comprising: a four-terminal sensing device adapted to be positioned in an environmental region to be monitored, said sensing device including first and second resistance heating wires spaced apart by a conducting core and encompassed by an outer shell, the resistance between at least one of said wires being decreased when vaporous hydrocarbons or smoke are present in said environmental region; a transformer having a primary winding adapted for connection to an a.c. voltage source, said transformer having first and second secondary windings, said secondary winding being connected to a first of said resistance heating wires of said sensing device to provide current flow therethrough when a.c. power is supplied to said transformer; rectifier circuitry connected to the second of said transformer secondary windings and to the second of said resistance heating wires of said sensor to provide a bias voltage thereto; a standby power relay connected to said rectifier circuitry and having normally open terminals connected to a source of battery power and to one of the resistance heating wires of said sensing device; an alarm relay having a set of normally open contacts; a transistor connected in a common emitter configuration having its base electrode coupled to the first of said resistance heating wires and its collector electrode connected through the winding of said alarm relay to the output of said rectifier circuitry; and an alarm connected to contacts of said alarm relay whereby the presence of smoke or gas within the region of said sensor decreases the resistance between the heating wires to produce a voltage at the base electrode of said transistor sufficient to bias said transistor into conduction and actuate said alarm relay to produce an alarm signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-30 | 1977-01-29 | 1977-07-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-30 | 1981-01-29 | 1981-07-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-30 | 1985-01-29 | 1985-07-31 | $7700.00 | Window Closed / Lapsed |