JPS609916Y2 - ionization smoke detector - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an ionization smoke detector.

Conventionally, in this type of ionization type smoke detector, radioactive isotopes such as Ra22' and Am'' are loaded as a radiation source 3' as shown in Figure 3 in order to ionize the air. It was necessary to reduce the intensity of radioactivity to increase safety.

At this time, simply reducing the radioactivity intensity will reduce the amount of ionization of the air, so it is necessary to apply a high voltage between the electrodes 1' and 2' to ensure the ion current I' given to the detection circuit 8'. It was necessary.

However, since the voltage of the DC power supply 7' is normally determined to be 24 V or less, a complicated step-up circuit is required to generate the high voltage, resulting in drawbacks such as high cost and reduced reliability.

The present invention seeks to provide an ionization type smoke detector that eliminates the above-mentioned drawbacks.

The ionization type smoke detector of the present invention will be explained below with reference to the drawings.

In FIGS. 1 and 2, numerals 1 and 2 are flat first and second outer electrodes placed in the ion chamber, which are opposed to each other. The first outer electrode 1 has Ra226. Am
A radiation source 3 made of a radioactive isotope of the ``1'' class is arranged.

Reference numerals 4, 5.6 denote first to third intermediate electrodes in which a plurality of parallel slits are formed in the center of a metal plate, and both sides of the slits are raised in opposite directions to form a fin shape. The two outer electrodes 1 and 2 are sequentially arranged with an appropriate interval between them.

7 is a DC power source, the anode of which is connected to the first. second outer electrode 1,
2 and the second intermediate electrode 5, and its cathode is connected to the first and third intermediate electrodes 5 via a detection circuit 8.

Furthermore, the operation of the ionization type smoke detector of the present invention will be explained in detail.

The first and second outer electrodes 1 and 2 and the second intermediate electrode 5 are connected to the anode of a DC power source 7, and the first and third outer electrodes 4 and 6 are connected to the anode of a DC power source 7.
is connected to the cathode of the DC power supply 7, so that the first
between the outer electrode 1 and the first intermediate electrode 4;
between the intermediate electrode 4 and the second intermediate electrode 5;
A substantially inter-electrode voltage of a DC power source 7 is applied between the intermediate electrode 5 and the third intermediate electrode 6 and between the third intermediate electrode 6 and the second outer electrode 2, respectively. There is.

At this time, the radiation emitted from the radiation source 3 ionizes the air in the ion chamber near the first and second outer electrodes 1.2 and the first to third intermediate electrodes 4, 5.6. Then, each ion is moved as shown in FIG.

As a result, an ionic current ■ is flowing through the circuit.

Now, when aerosol such as smoke enters between the electrodes in the ion chamber, ionized ions adhere to fine particles of the aerosol.

However, since the fine particles of the aerosol have low mobility, the current I decreases.

This decrease is detected by the detection circuit 8 and the abnormality is indicated on a subsequent display or the like.

As described above, in the ionization type smoke detector of the present invention, an intermediate electrode having a fin-shaped portion is inserted between the first and second outer electrodes of the ion chamber, and the first outer electrode and the intermediate electrode are connected to each other. Since the second outer electrodes are sequentially and alternately connected to the anode and cathode of the DC power source 7, (a) a high electric field can be formed in the ion chamber without increasing the voltage of the DC power source (1) Loading This has the effect of reducing the radioactivity of the radiation source used in the intermediate electrode, (c) ensuring safety, (e) ensuring reliability, and (e) reducing costs. Since parallel slits are made in the metal plate and both sides of the slit are pulled in opposite directions to form a fin shape, (f) mechanical strength can be increased (g) machining can be made easier, etc. .

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the ionization type smoke detector of the present invention, FIG. 2 shows a partial perspective view of the same, and FIG. 3 shows a conventional example. 1.2...Outer electrode, 3...Radiation source, 4゜5.6...Intermediate electrode, 7...DC power supply, inversion/detection circuit.

Claims (1)

[Scope of utility model registration request] An ionization type smoke detector comprising: an ionization chamber having a radiation source; a DC power supply connected to the ionization chamber to form an electric field; and a detection circuit connected in series to the ionization chamber and the DC power supply. , a first and a second in the ion chamber.
An intermediate electrode having a fin-shaped portion in the center is arranged between the first and second outer electrodes, and the electrodes consisting of the first and second outer electrodes and the intermediate electrode are placed opposite each other. An ionization type smoke detector characterized in that the electrodes are connected to the DC power source so that adjacent electrodes are connected to different electrodes of the DC power source.