JPS6132480Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to a scattered light type smoke detector in which a light receiver detects the light scattered by smoke emitted from a light source installed in a dark box. It is particularly suitable for use in fire alarm equipment.

[Conventional technology]

Traditionally, in scattered light type smoke detectors, smoke can flow in to prevent light from the outside world that is not caused by the scattering of smoke particles from entering the receiver as noise light, but A dark box is provided with a structure that prevents light from entering.

However, as noise light, in addition to the above-mentioned light from the outside world, there is also noise light caused by the actual light source, where the light from the light source is reflected on the inner surface of the dark box and enters the light receiver.

Therefore, conventional methods have been used to reduce reflections on the inside of the dark box by applying a matte black coating to the inside of the dark box, or to create a conical shape inside the dark box facing the light source as shown in Japanese Patent Application Laid-Open No. 51-53889. A scattered light type smoke detector has been proposed in which a light trap having a shaped surface is provided to absorb direct light irradiated onto the inner surface of a dark box from a light source and reduce noise light.

[Problem that the invention attempts to solve]

However, in any case, the noise light reflected from the inside of the dark box has not been sufficiently reduced, and in order to obtain a scattered light type smoke detector with higher sensitivity, it is necessary to develop a new and unprecedented smoke detector. It was hoped that a dark box with a structure would appear.

[Means for solving problems]

The scattered light sensor according to this invention includes a dark box formed by a cylindrical side wall closed at both ends by end walls, a light source that irradiates light into the dark box, and a light source that irradiates the light directly into the dark box. and a light receiver arranged to receive light scattered by smoke particles in a dark box, the light source and the light receiver being provided on the end wall side. , the cylindrical side wall is formed by arranging a plurality of thin plates at intervals between both ends in a spiral shape, and at least the light source is arranged so that its optical axis is directed toward the thin plates to solve the above problem. Settled.

[Effect]

The scattered light smoke detector according to this invention is constructed as described above, so that part of the light emitted from the light source is absorbed by the thin plate surface, and even after being emitted, it does not travel to the light receiver. Almost gone;
Therefore, noise light is sufficiently reduced, resulting in a highly sensitive scattered light type smoke detector.

〔Example〕

1 and 2 are a cross-sectional view and a cross-sectional view taken along the line A-A' of an embodiment of the scattered light smoke detector according to this invention,
The dark box 1 is formed of a cylindrical main body 4 closed at both ends by lids 2 and 3. One of the lids 2 and 3 is provided with a support 7 that integrally supports a light source 5 and a light receiver 6, and the other lid 3 has a conical protrusion 8. It is provided. It goes without saying that a light shield is placed between the light receivers 6 and 5 so that the light receiver 6 does not receive direct light from the light source 5. The periphery of the dark box 1 is covered with a cover body 10 having a ventilation hole 9.

As is clear from the cross-sectional view of FIG. 2, the main body 4 of the dark box 1 has an arcuate or planar surface 41 along the circumferential direction and a plane 42 that intersects at an obtuse angle at the end of this surface 41. It is formed by arranging a plurality of thin plates 11 having a chevron-shaped cross-section in a spiral shape at intervals. This results in
The gaps 13 formed between the thin plates 11 serve as smoke inflow paths that block light from the outside world but allow smoke to flow in. Further, the end edge of each thin plate 11 on the dark box center side forms a ridgeline portion 12 when viewed from the dark box center, and forms only an extremely small linear diffuse reflection surface for the light from the light source 5. The optical axis of the light source 5 is arranged to point toward the thin plate 11.

As described above, the scattered light type smoke detector according to this invention is constructed, so that the surface 14 inside the dark box 1 of each thin plate 11 is connected to the light source 5, as shown by the optical path l.
This is a surface that reflects light from the light receiver 6 in a direction other than the light receiver 6. Therefore, the light from the light source 5 is transmitted to the thin plate 11.
While repeatedly being absorbed and reflected by hitting the inner surface of the conical projection 8 or the conical protrusion 8, almost no light finally reaches the light receiver 6.

[Effect of idea]

As explained above, in the scattered light type smoke detector according to this invention, the entire main body 4 of the dark box 1 is configured as a reflecting surface that reflects the light from the light source 5 in a direction other than the light receiver 6. There is no need to apply matte black paint. In fact, it was confirmed that when the dark box of this invention was painted matte black, the amount of noise light increased. This not only makes it possible to use resin molding with a glossy surface to manufacture the dark box, but also
A painting process can be omitted in the manufacturing process, and when cleaning the sensor during maintenance and inspection, there is no need to take care of the painted surface, etc., and the dark box can be easily cleaned with water, alcohol, etc. Furthermore, the structure of the dark box is centered around the center, and the surrounding walls and smoke inflow paths are arranged axially symmetrically, so there is no need to consider the direction of smoke inflow. It has excellent effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the scattered light type smoke detector according to this invention, and FIG. 1 shows a longitudinal cross-sectional view thereof, and FIG. 2 shows a cross-sectional view taken along the line A-A' in FIG. Identical parts are designated by the same reference numerals throughout the figures. 2, 3... Lid body, 4... Main body of dark box, 1... Dark box, 5... Light source, 6... Light receiver, 11... Thin plate,
12... Ridge line portion, 8... Conical protrusion, l... Optical path of light source, 41... Surface along circumferential direction, 42...
intersecting planes.

Claims (1)

[Scope of utility model registration request] A dark box formed by a cylindrical side wall closed at both ends by end walls; a light source that irradiates light into the dark box; and a light receiver arranged to receive light scattered by the light source, and the light source and the light receiver are provided on the end wall side, wherein the cylindrical side wall is located at both ends of the smoke detector. 1. A scattering smoke detector comprising a plurality of thin plates arranged in a spiral shape at intervals between walls, wherein at least the light source is arranged so that its optical axis is directed toward the thin plates.