Smoke detector and ionisation apparatus
US8334782B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 11, 2007 |
| Grant date | Dec 18, 2012 |
| Priority date | — |
| Expiry date | Jul 26, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2235/00
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A smoke detector comprises a soft x-ray source (10) and an air space (16) communicating with ambient air (18) and positioned so that soft x-rays produced by the soft x-ray source (10) pass into the air space (16) to ionise air in the air space (16). A detector (14) is positioned for detecting ionised air in the air space (16). Smoke particles entering into the air space (16) mop up ionised air. This leads to a reduction in the number of ions detected which triggers an alarm. The soft x-ray source (10) preferably comprises a substrate (22) on which are provided a plurality of nanometer scale elongate structures (28). The elongate structures (28) are provided in an evacuated chamber (42) formed between the substrate (22), a spacer (30), and a laminated film (36). The laminated film (36) comprises an aluminum foil layer (38) and a supporting nylon layer (40). A voltage converting circuit (44) is powered by a 9 volt DC battery and applies a 1.5 kV DC voltage between the substrate (22) and the aluminum foil layer (38). In use, the electrical voltage induces field emission of electrons from the elongate structures (28). The electrons are accelerated across the chamber (42) to the aluminu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.