Title:
AUTOMATIC IONIC FIRE ALARM SYSTEM
United States Patent 3500368


Abstract:
1,163,121. Smoke detectors. NITTAN CO. Ltd. Aug.16, 1966 [March 30, 1966], No.36662/66. Heading G1N. [Also in Division H1] A smoke detector for a fire alarm system comprises a closed ionisation chamber 5, Fig.2, surrounded by a second ionisation chamber 8 open to the atmosphere through a wire mesh 6. A cupshaped electrode 1, forming part of the walls of the inner chamber, is common to both chambers and carries, on both sides, radio-active sources 2, 3, e.g. of radium. The second electrode of the inner chamber is provided by a disc 9 carried on an insulating support 5', e.g. of acrylic resin. Cylindrical members 7 together with the wire mesh 6 form the second electrode of the outer chamber. The common electrode 1 is connected to the gate electrode of an FET, Fig.3, normally arranged to be non-conducting. In the presence of smoke in the open ionisation chamber the voltage between the gate and source electrodes of the FET increases causing it to conduct. This in turn causes Zener diode D to conduct to trigger an SCR thereby producing a signal in receiver R which is used to energize an alarm. Reference has been directed by the Comptroller to Specification 1, 009, 271.



Inventors:
Abe, Nagao
Application Number:
US3500368DA
Publication Date:
03/10/1970
Filing Date:
08/18/1966
Assignee:
NITTAN CO LTD
Primary Class:
Other Classes:
327/399, 327/421, 327/428, 327/465, 327/509, 340/629
International Classes:
G01N27/64; G08B23/00; G01T7/12; G08B17/10; G08B17/11; G08B17/113; G08B25/14; (IPC1-7): G08B17/10
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