US3930247A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Open screen smoke detector and circuit
Assignee: JM Huber Corp
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Filing: 1974-09-06
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Granted: 1975-12-30
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Expires: 1994-09-06
Abstract
Abstract Herein disclosed is a particularly sensitive smoke detector system featuring a solid state sensor having a wide-mesh screen and employing a warning device in circuit with the anode-cathode path of a silicon control rectifier and an alternating current source. A biasing circuit comprising the solid state sensor is utilized to sense the presence of smoke and to cause the rectifier to pass current and to actuate the warning device when the threshold of the silicon control rectifier is exceeded.
Inventors
- 👤 Gordon Hurd
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:48
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/117
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
149 words
In a smoke detector of the variable resistive type the combination of: a variable resistive sensing element, a screen for mechanically protecting that element and having a mesh parameter such as to contain flash fires internally without impairing sensitivity to smoke or restricting the flow of air, said parameter being not more than 20 vertical wires and 20 horizontal wires per flat square inch, a source of energy, a warning device, a silicon control rectifier having a gate and also having an anode-cathode circuit in series with said warning device and said source of energy, and a control circuit including said resistive element, said control circuit having an input coupled to said source and an output coupled to said gate element in such manner that the presence of smoke decreases the resistance of the resistive element and causes the silicon control rectifier to fire, thereby energizing the warning device.
Claim 2
Dependent Claim
149 words
In a smoke detector of the variable resistive type the combination of: a variable resistive sensing element, a screen for mechanically protecting that element and having a mesh parameter such as to contain flash fires internally without impairing sensitivity to smoke or restricting the flow of air, said parameter being not more than 20 vertical wires and 20 horizontal wires per flat square inch, a source of energy, a warning device, a silicon control rectifier having a gate and also having an anode-cathode circuit in series with said warning device and said source of energy, and a control circuit including said resistive element, said control circuit having an input coupled to said source and an output coupled to said gate element in such manner that the presence of smoke decreases the resistance of the resistive element and causes the silicon control rectifier to fire, thereby energizing the warning device.
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) | 1978-12-29 | 1979-06-30 | 1979-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-29 | 1983-06-30 | 1983-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-29 | 1987-06-30 | 1987-12-30 | $7700.00 | Window Closed / Lapsed |