JPS6157835A - Photoelectric smoke detector - Google Patents

Abstract

PURPOSE:To eliminate the need for an optical trap mechanism, and to narrow down a measurement space and to reduce the size by reflecting a radiant light beam from a projection several times by a right and a left wall through a front and a rear wall and preventing the reflected light from striking on a photodetector directly. CONSTITUTION:The radiant light from the projector 1 is reflected at the left side of the front wall 6, reflected by the left wall 4 and right and left walls 5 and 4, and further reflected by a ceiling wall 9, walls 5 and 4, and rear wall 7 to strike the external wall of the photodetector 2. Therefore, the radiant light from the projector 1 becomes weak light through optical trapping operation while reflected by the walls 4 and 5 several times. If smoke enters a darkroom owing to fire occurrence, on the other hand, its scattered light illuminates the photodetecting element of the photodetector 2 to generates an output of fire annunciation. The output of the photodetexting element when the smoke enters the room to specific thickness where fire occurrence is judged is denoted S and an output in a normal state is denoted as N; and when the angle theta between the front and rear walls 6 and 7 is <=140 deg. or >=210 deg., a sufficient S/N is obtained.

Description

[Detailed description of the invention] [Application field of industry-1-] This invention relates to a small photoelectric smoke detector.

[Conventional technology]

The darkroom of conventional photoelectric smoke detectors has a complicated labyrinth structure or a double cover structure to prevent ambient light from entering the darkroom and allow smoke to easily enter.

[Problems with conventional technology]

However, the structure described above is large in size, making it unsuitable for use as a sensor built into equipment such as a computer or installed in an aircraft lavatory.
If the device is reduced in size and made smaller, it has the disadvantage that the signal-to-noise ratio deteriorates.

[Means for solving problems]

This invention 1r is a photoelectric smoke detector equipped with a light projector that emits light into a measurement space and a light receiver that detects scattered light (generated when smoke enters the measurement space), in which the space is formed. A dark room is provided in front of the projector, and has a front wall having a flat or curved surface such that the light from the projector is reflected at a predetermined angle with respect to the optical axis, and a front wall that is substantially parallel to the optical axis of the projector. Left and right (!tll) walls, and a rear wall with a flat or curved surface installed at the rear of the projector so that the reflected light from the left and right side walls does not directly illuminate the receiver. This is a photoelectric smoke detector composed of

[For production]

The photoelectric smoke detector of the present invention has the above-mentioned configuration, so that the dark room itself has a light playing function, and the light rays emitted from the floodlight are sent through the front and rear walls to the left and right side walls many times. By preventing the direct reflected light from entering the light-receiving element r of the light receiver, or by making it extremely weak even if it does enter, the light can be regenerated.
This is a small photoelectric smoke detector that does not require a knob mechanism and has a narrow measurement space.

〔Example〕

An embodiment of the photoelectric smoke detector of the present invention will be described below with reference to FIGS. 1 to 3. In the figure (al) a cross-sectional view of the darkroom of this invention, (bl Lj', in its cross-sectional view, 1
4; 1 is a light emitter that emits a convergent luminous flux that includes a light source such as a light emitting diode and a lens; 2 is a light receiver that includes a light-receiving element such as a solar cell and a lens; 3 is 1 and a light receiver 1.2
The light shielding plates 4 and 5 provided in between are left and right side walls provided substantially parallel to the optical axis of the light beam emitted from the projector 1;
6 is a front wall provided in front of the projector 1 and has a flat or curved surface such that the light from the projector 1 is reflected at a predetermined angle with respect to the optical axis; 7 is a front wall provided in the rear of the projector 1 and includes left and right side walls 4.
8.1) is a bottom wall and a ceiling wall; Smoke inlet holes (not shown) are provided near the center of the wall 8 and both ends of the top wall 9. The walls are painted black and mirror-like. In the diagram, the starting point of Sε91 light li1 is
Arrow C, point where I light #jli reaches to black light, opposite to l side wall 4! 1.1ffiiζ 1 place is a white circle Let side wall 5 - corner is a reflection point with ceiling wall 9
Figure 1 +i, the optical axis is 1', and the 1. -i
i "1st small left 1J' lid t,' and θ-15 (
In the case of B, Fig. 2+, 1. ．． ．． 'l'l', 5° in the force direction (relative to light device 2), 0-15 [1'
(In case C, Fig. 3 shows the use of the projector 1 in Fig. 1 as 1.
-]1t:' This is the case where it is set.

Next, the function of the darkroom will be explained. For example, in FIG. 1, the light emitted from the floodlight 1 is reflected on the left side of the front wall 6, reflected on the left side wall 4, then reflected on the right side wall 5°4, and further reflected on the ceiling wall 9, the right side wall 5, and the left side wall 5. It is reflected to the left side of the wall 4 and the rear wall 7, and collides with the outer wall of the light receiver 2. The light thus emitted from the projector 1 is reflected several times by the left and right side walls 4.5, attenuating the light and acting as a light trap, resulting in extremely weak light.

To explain further in FIG. 2, the light emitted from the floodlight 1 is reflected to the left side of the front wall 6, and then to the left side wall 4, right, left, right side wall, ceiling wall 9, left side wall 4, right side wall 5, etc. It is reflected to the right side of the rear wall 7 and collides with the beam receiver 2. In addition, in FIG. 3, the light emitted from the floodlight 1 is reflected to the left side of the front wall 6, and is reflected to the left side wall 4, the ceiling wall 9, right, left, right, the left side wall, the left side of the rear wall 7, and the outer wall of the floodlight 1. It collides with the light and is attenuated by θ into a weak light.

- On the other hand, when smoke enters the dark room due to a fire outbreak, the output that notifies the occurrence of fire (scattered light illuminates the light receiving element of the light receiver 2) is controlled. Suppose that the output of the light receiving element is S when the smoke with the predetermined moisture level that is determined to be the occurrence of a fire enters the dark room, and the output during normal times is N, and the angle of the front and rear walls 6 and 7 is θ.
Then, the characteristics shown in FIG. 4 are shown. According to this figure, θ
An S/N ratio sufficient for practical use was obtained when the angle was below 140° and above 210°.

〔effect〕

In the photoelectric smoke detector of this invention, the darkroom has the above-described configuration and the darkroom itself has a light trapping function, meaning that the light rays emitted from the floodlight are reflected many times on the left and right side walls via the front and rear walls. This is a small photoelectric smoke detector with a narrow measurement space and no additional optical trapping mechanism, since the direct reflected light will not be incident on the light receiving element of the receiver, or even if it is incident, it will be extremely weak. There is an effect that the vessel can be obtained.

[Brief explanation of drawings]

Figures 1 to 3 are 4111 schematic diagrams of the photoelectric smoke detector of the present invention, (•] is a cross-sectional view, (bl is a cross-sectional view of E, and Figure 4 is a 814.Y genital line diagram. stomach). DESCRIPTION OF SYMBOLS 1... Emitter, 2... Light receiver 2:i, 3... Light shielding plate, 4... Left side wall, 5... Right side wall, 6... Front wall, 7
...Back wall, 8...Bottom wall, 9...Top 1 wall. Patent applicant Jinnomi Disaster Prevention Industry Co., Ltd. τ Figure 1 (G) 9 days FJf increase (b) Figure 2 (a) (b) 1, <) Figure 3 (Q> (b) -9 supply phase I Station E # Chestnut

Claims (1)

[Claims] In a photoelectric smoke detector equipped with a light projector that emits light into a measurement space and a light receiver that detects scattered light caused by smoke entering the measurement space, the dark room forming the space is
A front wall provided in front of the projector and provided with a flat or curved surface that reflects the light from the projector at a predetermined angle with respect to the optical axis, left and right side walls approximately parallel to the optical axis from the projector, and a front wall provided at the rear of the projector. and a rear wall having a flat or curved surface that reflects light at a predetermined angle such that the light reflected from the left and right side walls does not directly illuminate the light receiver.