JPS6227439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in photoelectric smoke detectors.

In the conventional photoelectric smoke detector, as shown in FIG. 1, the smoke inlet 3 has a labyrinth structure with first and second light shielding walls 2a and 2b arranged in a double cylindrical shape. It had a structure in which a porous dust-proofing and insect-proofing filter 5 was disposed between the second light-shielding walls 2a and 2b. Therefore, in such a conventional example, the light emitting chamber 6
In order to prevent the light emitted from the light shielding walls 2b and the like from being reflected by the light receiving chamber 7 and reducing the S/N, it is necessary to apply black coating to the inner surfaces of the light shielding walls 2a and 2b. In addition, in order to sufficiently attenuate unnecessary reflected light, the light emitting and light receiving chambers 6 and 7 and the light shielding walls 2a and 2
b) There was a problem in that it was necessary to increase the distance from the wall surface, making it unavoidable to increase the size of the vessel.

The present invention has been provided in view of the above-mentioned points, and an object of the present invention is to provide a photoelectric smoke detector whose body can be downsized without reducing smoke inflow property or S/N. The purpose is to

An embodiment of the present invention will be described in detail below with reference to the drawings.
FIG. 2 shows an embodiment of the present invention, in which a light-shielding wall 2 having smoke inlets 3 having a labyrinth structure is formed around the periphery of the vessel 1, and the back surface of each of the smoke inlets 3 is arranged opposite to the inner surface of the light-shielding wall 2. The light emitting and light receiving chambers 6 and 7 are arranged in the vessel body 1 in such a way that the light from the light emitting chamber 6 does not directly enter the light receiving chamber 7, and the light emitting beam from the light emitting chamber 6 and the light receiving from the light receiving chamber 7 are separated. The beams intersect at the center of the vessel body 1, and this intersection area is defined as a smoke sensing area 4.
5 is a porous filter provided for the purpose of preventing insects and dust, and is placed on the inner surface of the smoke inlet 3 so as to surround the smoke sensing area 4;
Usually, this filter 5 is made of a black material to prevent light reflection. However, this filter 5
In addition to preventing insects and dust from entering the smoke sensing area 4 and allowing only smoke to enter the smoke sensing area, the filter 5 blocks light from the light emitting chamber 6 and prevents reflection. This is intended to prevent the resulting S/N reduction. That is, even if the light that has passed through the small holes 5a of the filter 5 is diffusely reflected on the inner surface of the light-shielding wall 2, as shown in the action diagram of FIG. The proportion of light incident on the inside of the filter 5 is sufficiently low, and it is possible to sufficiently prevent a drop in S/N due to reflection, especially without applying black coating to the inner surface of the light shielding wall 2. The peripheral surface is roughened or textured to sufficiently reduce reflectance. As the material for the filter 5, a filter with low reflectance and good filter properties can be obtained by molding plastic into a fibrous form to form a so-called non-woven fabric.

Since the present invention is configured as described above, it becomes possible to reduce internal reflection light from a light-shielding wall, etc. using a filter, and therefore it becomes possible to eliminate the need for conventional black painting. In addition, it has the effect of narrowing the facing distance between the light emitting and light receiving chambers and the light shielding wall, thereby achieving miniaturization of the device body without causing a decrease in S/N.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional example, Fig. 2 is a sectional view of an embodiment of the present invention, and Fig. 3 is an explanatory diagram of the same operation. 1 is a vessel body, 2 is a light shielding wall, and 3 is a smoke inlet , 4 is a smoke sensing area, and 5 is a filter.

Claims (1)

[Claims] 1. Form an appropriate number of smoke inlets with a labyrinth structure on the light-shielding wall around the outer periphery of the vessel to prevent direct light from entering the vessel, and install smoke inlets on the inner surface of the smoke inlet so as to surround the smoke sensing area formed in the center of the vessel. A photoelectric smoke detector comprising a porous filter.