Patent US3824422A successfully refreshed from Google Patents.
US3824422A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Smoke detectors
Assignee: Crucible SA
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Filing: 1973-06-25
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Granted: 1974-07-16
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Expires: 1993-06-25
Abstract
Abstract A smoke detector for use in detecting the early outbreak of a fire and including a housing defining a smoke chamber, a housing defining a reference chamber, a grid in each of the chambers and an electrostatic shield surrounding each of the grids. The shields are made of an electrically-conductive plastic material thereby eliminating the possibility of corrosion.
Inventors
- 👤 Der Walt N Van
- 👤 B Bout
- 👤 T Newington
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:32
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11; G08B17/113; G01; G01N; G01N27/00; G01N27/62; G01N27/64; G01N27/66
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
48 words
A smoke detector of the type including a housing defining a smoke chamber, a housing defining a reference chamber, a grid in each of the chambers and an electrostatic shield surrounding each of the grids, characterised in that the electrostatic shields are made of an electrically-conductive plastic material.
Claim 2
Dependent Claim
48 words
A smoke detector of the type including a housing defining a smoke chamber, a housing defining a reference chamber, a grid in each of the chambers and an electrostatic shield surrounding each of the grids, characterised in that the electrostatic shields are made of an electrically-conductive plastic material.
Claim 3
Dependent Claim
41 words
A smoke detector as claimed in claim 1 characterised in that the smoke chamber housing itself constitutes the electrostatic shield for the grid in the smoke chamber and in that the smoke chamber housing is made of an electrically-conductive plastic material.
Claim 4
Dependent Claim
41 words
A smoke detector as claimed in claim 1 characterised in that the reference chamber housing itself constitutes the electrostatic shield for the grid in the reference chamber and in that the reference chamber housing is made of an electrically-conductive plastic material.
Claim 5
Dependent Claim
20 words
A smoke detector as claimed in claim 1 characterised in that the grids are made of an electrically-conductive plastic material.
References Cited (Backward Citations)
US3769917A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-07-15 | 1978-01-14 | 1978-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-15 | 1982-01-14 | 1982-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-15 | 1986-01-14 | 1986-07-16 | $7700.00 | Window Closed / Lapsed |