The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 14, 1980
Filed:
Dec. 11, 1978
Keishin Tsuchiya, Higashi-Yamato, JP;
Ichiro Yoshihara, Funabashi, JP;
Kazuhito Saito, Kawasaki, JP;
Takeshi Abe, Yokohama, JP;
Kiyoshi Abe, Yokohama, JP;
Kiyoshi Sone, Tokyo, JP;
Ricoh Company, Ltd., Tokyo, JP;
Abstract
An alarm system for detecting a dangerous condition such as the increase in content of or the presence of toxic or inflammable gas in the air and giving a warning signal. The alarm system comprises an AC power supply, a full-wave rectifier connected to the AC power supply and rectifying alternating current from the AC power source into direct current. An AC bridge circuit connected to the AC power supply and includes a sensor element at least in one branch. An AC operational amplifier is supplied with power from the full-wave rectifier and receives an input signal which is the output signal delivered from the bridge circuit through a DC blocking capacitor. A thyristor is connected in parallel with the AC power supply, with its control gate connected to the output of the operational amplifier, and its main electrodes in series with an alarm indicator actuable when the thyristor is triggered into the conduction state. Such triggering occurs when the output signal voltage from the operational amplifier reverses its phase by 180.degree., i.e., when the resistance of the sensor element varies when a dangerous condition exists.