US4099165A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fire detection apparatus in a preheater
Assignee: Svenska Rotor Maskiner AB
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Filing: 1976-12-16
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Granted: 1978-07-04
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Expires: 1996-12-16
Abstract
Abstract A fire detection apparatus in a rotary regenerative air preheater comprises a plurality of temperature sensitive detectors which produce an electrical signal, and means for differentiating the electrical signals from the detectors. The differentiated signals are passed through a low pass filter having a large time constant and are then fed to a comparator which actuates a signalling device when the low pass filter output signal exceeds a predetermined value.
Inventors
- 👤 Trygve Botnen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:34
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/06; F; F28; F28F; F28F27/00; F28F27/006; G01; G01K; G01K3/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
245 words
Fire detection apparatus in a preheater comprising: a preheater housing (18) having an air duct (20) and an exhaust duct (22); a mass of heat absorbent material in said housing; means for imparting a relative rotation between the mass of material and the ducts; a plurality of temperature sensitive detectors (30) for sensing the temperature of radially adjacent sections (16) of the material in said housing (18), each of said detectors producing a signal proportional to the temperature in its respective section (16); and at least one indicating means coupled to said detectors and actuated by said detector signals for indicating when a rate of change of the temperature in any of said sections is in excess of a predetermined rate of change, said indicating means comprising: a differentiating means (44) connected to said detectors for producing an output signal proportional to the derivative or rate of change of the input signal thereto; a low-pass filter means (50) coupled to receive said output signal of said differentiating means, said low-pass filter means having a large time constant as compared with the time constant of said detectors for producing a low-pass filter output signal; comparator means (53) coupled to receive said low-pass filter output signal and for producing a further signal at its output (56) when said low-pass filter output signal exceeds a predetermined value; and a signalling device coupled to said comparator means for signalling when said low-pass filter output signal exceeds said predetermined value.
Claim 2
Dependent Claim
245 words
Fire detection apparatus in a preheater comprising: a preheater housing (18) having an air duct (20) and an exhaust duct (22); a mass of heat absorbent material in said housing; means for imparting a relative rotation between the mass of material and the ducts; a plurality of temperature sensitive detectors (30) for sensing the temperature of radially adjacent sections (16) of the material in said housing (18), each of said detectors producing a signal proportional to the temperature in its respective section (16); and at least one indicating means coupled to said detectors and actuated by said detector signals for indicating when a rate of change of the temperature in any of said sections is in excess of a predetermined rate of change, said indicating means comprising: a differentiating means (44) connected to said detectors for producing an output signal proportional to the derivative or rate of change of the input signal thereto; a low-pass filter means (50) coupled to receive said output signal of said differentiating means, said low-pass filter means having a large time constant as compared with the time constant of said detectors for producing a low-pass filter output signal; comparator means (53) coupled to receive said low-pass filter output signal and for producing a further signal at its output (56) when said low-pass filter output signal exceeds a predetermined value; and a signalling device coupled to said comparator means for signalling when said low-pass filter output signal exceeds said predetermined value.
Claim 3
Dependent Claim
63 words
Apparatus as defined in claim 1, wherein said indicating means further includes: a second comparator means (47) having an input connected to the output of said differentiating means (44), and an output (50'); and an OR-gate (40) having respective inputs (43;42) coupled to the outputs (56;50') of said first and second comparator means, the output (57) of said OR-gate feeding said signalling device.
Claim 4
Dependent Claim
48 words
Apparatus as defined in claim 2, wherein: said OR-gate (40) has a further input (41); and said indicating means further includes a third comparator means (36) coupled to said temperature sensitive detectors, the output (38) of said third comparator means feeding said further input terminal of said OR-gate.
Claim 5
Dependent Claim
40 words
Apparatus as defined in claim 3, wherein said indicating means further includes: a further comparator means (80) coupled to said temperature sensitive detectors; and means (84-86) coupled to said further comparator means for indicating normal conditions in said air preheater.
Claim 6
Dependent Claim
40 words
Apparatus as defined in claim 2, wherein said indicating means further includes: a further comparator means (80) coupled to said temperature sensitive detectors; and means (84-86) coupled to said further comparator means for indicating normal conditions in said air preheater.
Claim 7
Dependent Claim
40 words
Apparatus as defined in claim 1, wherein said indicating means further includes: a further comparator means (80) coupled to said temperature sensitive detectors; and means (84-86) coupled to said further comparator means for indicating normal conditions in said air preheater.
Claim 8
Dependent Claim
53 words
Apparatus as defined in claim 1, wherein said indicating means further includes: another comparator means (36) coupled to said temperature sensitive detectors; and an OR-gate (40) having respective inputs (43;41) coupled to the outputs (56;38) of said first and said another comparator means, the output (57) of said OR-gate feeding said signalling device.
Claim 9
Dependent Claim
13 words
Apparatus as defined in claim 1, wherein said preheater is an air preheater.
Claim 10
Dependent Claim
15 words
Apparatus as defined in claim 1, wherein said preheater is a rotary regenerative air preheater.
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) | 1981-07-03 | 1982-01-02 | 1982-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-07-03 | 1986-01-02 | 1986-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-07-03 | 1990-01-02 | 1990-07-04 | $7700.00 | Window Closed / Lapsed |