Abstract: An ionization smoke detector of the present invention has an annular engaging flange portion formed integrally on the periphery of an insulating board and an engaging groove formed on a cover, so that a circuitry-accommodating portion may be moisture- and gas-tightly sealed merely by inserting the flange portion into the groove, without using special sealing members such as ruber packing members.In an intermediate electrode mounting structure of the present invention, support legs are formed integrally on the periphery of the intermediate electrode which may be simply inserted into an opening of the insulating board to fix and support the intermediate electrode, without using screws etc. Thus, a space needed to mount the intermediate electrode can be minimized. An electrode lead is connected to a lead of an FET insulatedly potted at an appropriate place on the backside of the insulating board with a hot melt synthetic resin.

Abstract: 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.

Abstract: Disclosed herein is an improved composite-type heat-system fire sensing device consisting essentially of a differential sensing element and constant-temperature sensing element, capable respectively of actuating a pair of electric contacts. These two type of sensing elements used in customary devices are difficult to assemble and to adjust. There are also serious problems for production and wider utilization of the sensing device. Further, the elements lack practical utilizability as well as reliability. The sensing device of this invention overcomes the abovementioned problems of the customary devices by effecting sensitivity matching of different operation characteristics of the two sensing elements, and makes it possible to optionally and freely adjust the sensitivity of the sensing device as required in accordance with the conditions of the place of installation of the sensing device so as to ensure a higher reliability and wider application of the sensing device.