Hochiki Kabushiki Kaisha

Kanji Ishii

Sadataka Yuchi

Akira Furuyama

Atsushi Nagai

Yasaburo Adachi

The present invention relates to an improvement of an ionizing smoke sensor having one radiation source and a two chambered structure consisting of an internal ionization chamber housing an internal electrode having a radiation source and defined by an intermediate electrode, and an external chamber where smoke can flow in, defined by an external electrode and irradiated from the radiation source through an opening in the intermediate electrode. Hitherto, in an ionizing smoke sensor having one radiation source and a two chambered structure, there has been a problem in that the giving of misinformation and noinformation occur when a little amount of thread, moisture or dust invades or a current of air flows an internal ionization chamber through an opening and an external ionization chamber. In addition, the electric field in the internal ionization chamber loses its homogeneity because of the opening, hence V-I characteristics preferable for the internal ionization chamber can not be obtained. Furthermore, stable V-I characteristics can not be obtained since hardly any smoke can hardly flow into the internal ionization chamber because of the mesh structure. In the ionizing smoke sensor of the present invention, the above described problems are solved by forming the opening part in the intermediate electrode with a mesh structure having a rate of porosity more than or equal to 50%.

Ionizing smoke sensor

An ionization-type smoke sensor having a 2-chamber 1-radiation source structure including an inner electrode having a radiation source, an intermediate electrode having an opening through which radiation from the radiation source passes, an outer electrode through which smoke may flow inside from outside, and an insulator supporting and insulating the inner electrode, the intermediate electrode and the outer electrode. In the sensor, a fence portion made of an insulating material is formed on and projecting from a surface of the insulator which faces the outer electrode, the fence portion surrounding the periphery of the opening of the intermediate electrode. By virtue of this arrangement, even when the sensor is subjected to flow of air heading from outside toward the opening of the intermediate electrode, the fence serves to reduce the flow of air heading toward the opening, thereby enabling the characteristics of the sensor chambers to remain stable against flow of air. Since the fence portion made of an insulating material is formed to project from the surface of the insulator, the creepage distance between the intermediate electrode and the outer electrode is long, thereby enabling an improved level of insulation for the electrodes.

Ionization type smoke sensor

A fire detector and a fire alarm system wherein a plurality of fire detectors are connected across a pair of lines leading to a signal station and which is capable of detecting, at the signal station, removal of a detector head or heads from an associated socket or sockets of any one or more detectors and yet capable of keeping the succeeding fire detectors operative to send a possible fire alarm signal even after removal of the head or heads. Each of said fire detectors comprises a means for disconnecting the line connected therethrough to the succeeding detector, temporarily in the course of removal of the detector head or heads from the associated socket or sockets or periodically after the detector or detectors has or have been removed from the associated socket or sockets. The signal station comprises a means for detecting the temporary or periodical disconnection of the line.

Growing community of inventors

Yokohama, Japan

Kanji Ishii