JPS6126920Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a protection device for protecting the lens of the light emitting/receiving part of a transmitted light type smoke detector from dust and moisture.

A transmitted-light smoke detector includes a light projecting section that includes a light source such as a light emitting diode and a lens that converts the light emitted from the light source into parallel light beams, and a light projecting section that is placed facing the light projecting section at a predetermined distance and that emits the light beams. It consists of a convergence lens that receives light and a light receiving section equipped with a light receiving element such as a solar cell, and the light emitted from the light emitting section to the light receiving section is generated when smoke enters between the projecting and receiving sections. It was designed to detect the attenuation and warn of a fire.

However, since the above-mentioned sensor is mounted on a ceiling or the like and is constantly exposed to the air flow generated by heating and cooling, the lens surface of the light emitting and receiving part may become dirty or condensate due to dust and moisture carried by this air flow. However, there was a drawback that the light irradiated to the light receiving element was attenuated and a false alarm was issued even though there was no fire.

SUMMARY OF THE PRESENT DISCLOSURE In view of the above, the present invention provides a protection device for the light emitting and receiving parts of a light transmitted smoke detector, which is capable of protecting the lenses of the light emitting and receiving parts from dust and moisture.

An embodiment of this invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, 1 and 2 are a light projecting part and a light receiving part, which are made of cylindrical bodies and are arranged facing each other with an interval between them.
The light projector 1 includes a light source 3 such as a light emitting diode, and a lens 4 that converts the light emitted from the light source 3 into parallel rays L. The light receiver 2 includes a lens 5 that converges the rays L, and a lens 5 that converges the light rays L, and a lens 5 that focuses the light rays L. A light receiving element 6 such as a battery is provided. In addition, the lens 4 of the light emitting/receiving section,
5 has a contact surface 8 between a large number of elongated holes 7 and the lenses 4 and 5 as shown in FIGS. 2 and 3.
Lotus root-shaped columnar protection devices 9 made of a porous material (for example, a porous acrylonitrile-based special resin) are provided. Furthermore, although not shown, the light source 3 is provided with a lighting circuit, and the light receiving element 6 is provided with a detection circuit that detects a predetermined output change and issues an alarm.

Next, the operation of this sensor will be explained. Under normal conditions, the light emitted from the light source 3 of the light projecting section 1 is emitted into the measurement space as a parallel light beam L through the lens 4 and the long hole 7 of the protection device 9, and is further emitted through the long hole 7 of the protection device 9 of the light receiving section 2. The light receiving element 6 is strongly irradiated through the lens 5. In such a state, if a fire breaks out and smoke enters the parallel light beam L in the measurement space, the light will be absorbed or scattered by the smoke particles and will cause damage to the elongated hole 7 of the protection device 9 of the light receiving section 2 and the lens.
The light irradiated to the light receiving element 6 through 5 decreases,
This change is detected by the detection circuit and a fire signal is issued.

In addition, floating dust that tries to enter the light emitting part 1 or the light receiving part 2 by riding on the air flow generated by heating and cooling equipment etc. is stopped on the side wall surface of the elongated hole 7 of the protection device 9, accumulates, and absorbs moisture. Therefore, the lenses 4 and 5 are less likely to be directly soiled, fogged, or exposed to dew condensation. Furthermore, since the elongated hole 7 of the protection device 9 provided in the light receiving section 2 is provided parallel to the axis of the parallel light beam L emitted from the light projecting section 1, the scattered light generated by smoke passes through this hole 7 to the light receiving element. Since the amount of irradiation of 6 is reduced, there is also the effect that a good sensor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a transmitted light type smoke detector equipped with a protection device of this invention, FIG. 2 is a front view of the protection device, and FIG. 3 is a sectional view of FIG. 2. 1... Light projecting section, 2... Light receiving section, 4, 5... Lens, 7... Elongated hole, 9... Protective device. 〓〓〓〓〓

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A protective device that is provided in close contact with the front surface of the lens of the light emitting and light receiving parts of a transmitted light type smoke detector in which the light emitting part and the light receiving part are arranged facing each other at a certain interval. 1. A protection device for a light emitting/receiving part of a transmitted light type smoke detector, characterized in that the device is constituted by a lotus root-shaped column having a large number of long holes. 2. A protection device for a light emitting/receiving part of a transmitted light type smoke detector as set forth in claim 1 of the claimed utility model registration, in which the column body is made of a water-absorbing material.