Patent US3723746A successfully refreshed from Google Patents.
US3723746A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fire detecting apparatus sensitive to refraction
Assignee: National Research Development Corp UK
•
Filing: 1971-01-07
•
Granted: 1973-03-27
•
Expires: 1991-01-07
Abstract
Abstract Fire detecting apparatus comprises an emitter for generating a beam of electromagnetic radiation and a detector for producing an output signal dependent upon the amount of radiation incident thereon. The apparatus is arranged to be responsive to a fluctuating component in the output of a detector to operate an alarm or fire control means.
Inventors
- 👤 D Lawson
- 👤 Sullivan E O
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:16
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/103
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
80 words
Fire detecting apparatus comprising: emitter means for generating a constant and stationary beam of electro-magnetic radiation, photodetector means sensitive to said radiation and producing an output signal dependent upon the position of the beam of radiation incident thereon from said emitter means, and control means responsive to an alternating component having a first predetermined frequency range and non-responsive to an alternating component having a second predetermined frequency range in the output of the photodetector means for producing a control signal.
Claim 2
Dependent Claim
80 words
Fire detecting apparatus comprising: emitter means for generating a constant and stationary beam of electro-magnetic radiation, photodetector means sensitive to said radiation and producing an output signal dependent upon the position of the beam of radiation incident thereon from said emitter means, and control means responsive to an alternating component having a first predetermined frequency range and non-responsive to an alternating component having a second predetermined frequency range in the output of the photodetector means for producing a control signal.
Claim 3
Dependent Claim
18 words
Fire detecting apparatus as claimed in claim 1, in which the predetermined range is 40 to 70 Hz.
Claim 4
Dependent Claim
20 words
Fire detecting apparatus as claimed in claim 1, including an alarm arranged to operate in response to said control signal.
Claim 5
Dependent Claim
21 words
Fire detecting apparatus as claimed in claim 1, including fire control means arranged to operate in response to said control signal.
Claim 6
Dependent Claim
83 words
Fire detecting apparatus as claimed in claim 1, in which the photodetector means comprises: a photocell and a mask disposed between the emitter means and said photocell, said mask having transmitting and absorbing portions which respectively allow and prevent said beam illuminating said detector means and which are arranged in a checker board configuration, whereby fluctuations in the position of said beam cause the beam to alternately illuminate the respective portions of the mask thereby causing the output from the photocell to fluctuate.
Claim 7
Dependent Claim
19 words
Fire detecting apparatus as claimed in claim 5, in which each transmitting portion of the mask comprises collimator means.
Claim 8
Dependent Claim
57 words
Fire detecting apparatus as claimed in claim 1, in which the photodetector means comprises a plurality of discrete detectors arranged in an array with spaces between adjacent detectors of substantially the same area as the area of each detector and means for adding the outputs of the detectors to form a single output for the detector means.
Claim 9
Dependent Claim
87 words
Fire detecting apparatus as claimed in claim 1, in which the phOtoconductor means comprises a single detector of substantially the same area as the area of cross-section of the beam of radiation at the detector, the emitter means being arranged to detect the beam on to the edge of the detector in such a manner that occurrence of a fire in the space through which a beam passes between the emitter means and the photodetector means causes the beam to oscillate over a boundary of the detector.
Claim 10
Dependent Claim
46 words
Fire detecting apparatus as claimed in claim 1, in which the photodetector means is disposed adjacent to the emitter means, reflector means comprising three adjacent mirrors disposed at right angles to one another, being arranged to reflect the beam of radiation on to the photodetector means.
Claim 11
Dependent Claim
45 words
Fire detecting apparatus as claimed in claim 1, in which a half-silvered mirror is disposed in front of the emitting means to divert a portion of the beam, said portion being directed on to subsidiary detector means which is arranged to operate an intruder alarm.
Claim 12
Dependent Claim
22 words
Fire detecting apparatus as claimed in claim 1, in which the emitter means is arranged to generate radiation in the visible range.
Claim 13
Dependent Claim
16 words
Fire detecting apparatus as claimed in claim 11 in which the emitter means is a laser.
References Cited (Backward Citations)
US2404147A
Cited
US3566385A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |