Hochiki Corporation

Hochiki Kabushiki Kaisha

Yoshihito Hirai

Tetsuya Nagashima

Junichi Narumiya

Yoshinori Kaminaka

Hiroshi Yashima

Mariko Ishida

Satoru Koizumi

Osami Minowa

Tetsuji Sato

A separate type photoelectric smoke sensor having a light emitting section for emitting a light beam to a reflecting plate disposed at a certain distance from the light emitting section, a light receiving section for receiving reflected light from the reflecting plate, and a judgement section for outputting a sense signal if a received light output from the light receiving section is smaller than a threshold value previously set. The quantity of reflected light from a shielding object is obtained from the difference between or the ratio of the quantity of received light measured during lighting of the light emitting section in a situation where there is no shielding object and the quantity of received light measured during lighting of the light emitting section in a situation where there is the shielding object, and the difference between these quantities of reflected light and the quantity of received light measured during lighting of the light emitting section is compared with the threshold value to determine whether or not there is a fire. It is thereby possible to correctly discriminate the existence of any shielding object other than smoke in an observed region. Even if there is a shielding object, the influence of the shielding object is cancelled to obtain the true quantity of reflected light from the reflecting plate no matter what the reflectivity thereof, thereby ensuring accurate determination as to whether or not there is a fire.

Smoke sensor

An ionization smoke detector of the present invention comprises an outer electrode having a plurality of smoke inlets formed on a side wall thereof, an outer cover and a partition wall having a plurality of smoke inlets disposed between the outer electrode and the outer cover to form a triple wall structure. The smoke inlets formed on the outer cover, the partition wall and the outer electrode are staggered from each other. Air stream hitting against the detector is attenuated by the triple wall structure and generally half of the air flow is allowed to pass between the outer cover and the outer electrode and between the partition wall and the outer electrode, flowing out of the detector and the remaining half of the air flow is led into the detector through the smoke inlets.

Highly sensitive smoke detector

Growing community of inventors

Odawara, Japan

Yoshihito Hirai