JPH05296929A - Fume transmissivity measuring instrument - Google Patents

Abstract

PURPOSE:To prevent the occurrence of such a case that the title instrument cannot make accurate measurement due to the contamination of its light emitting and receiving sections with dust in the air. CONSTITUTION:In order to prevent the adhesion of dust to the surface of a leans 5, clean air is fed into the dustproof lens barrel 6 of a light emitting section 1 from an air blower 16 and the pressure in the barrel 6 is increased. Since the contamination of the lenses of the section 1 and a light receiving section with dust can be prevented, the accuracy and reliability of the title instrument can be stabilized at high levels for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fume transmittance measuring device used for measuring a visual distance in a road tunnel or the like.

[0002]

2. Description of the Related Art FIG. 4 is a sectional side view showing a conventional optical fume transmittance measuring apparatus.
Is a light receiving portion, and 3 is air to be measured between the light emitting portion 1 and the light receiving portion 2. In the light projecting unit 1, 4 is a light source, 5 is a lens that focuses the light from the light source 4, 6 is a dustproof tube provided in front of the lens 5, and 7 is light that exits from the light source 4 and travels in the dustproof tube 6.

In the light receiving section 2, 8 is a dust-proof cylinder provided on the light-receiving side, 9 is light traveling in the dust-proof cylinder 8, 10 is a lens for focusing the light 9, 11 is light received from the lens 10, and an electric signal A photoelectric tube as a photoelectric element for converting into 12
An arithmetic unit for obtaining the transmittance of the measured air 3 on the basis of the output signal of, and an output signal 13 for indicating the transmittance obtained by the arithmetic unit 12. Reference numeral 14 denotes light that travels in the measured air 3.

Next, the operation will be described. In the light projecting unit 1, the light 7 emitted from the light source 4 and narrowed down by the lens 5 passes through the measured air 3 as the light 14. In the light receiving section 2, the incoming light 9 is focused by the lens 10 and enters the phototube 11. Since the phototube 11 outputs a signal proportional to the intensity of the light 9, this is amplified by the calculator 12 to obtain the output signal 13. This output signal 13 is the measured air 3
It is proportional to the smoke density of.

The air 3 to be measured contains fine particles having a very high viscosity due to soot from cars and dust on the road surface, and adheres to the surfaces of the lenses 5 and 10 as the measurement time elapses, resulting in accurate output signals. You will not be able to get 13. Therefore, the dustproof cylinders 6 and 8 are provided in front of the lenses 5 and 10 to reduce the chance that the particles directly contact the lenses 5 and 10 and prevent the lenses 5 and 10 from being soiled. The lenses 5 and 10
In some cases, a transparent plate (film-like) for preventing dust is provided on the front surface of the lens to prevent the lenses 5 and 10 from being directly soiled.

[0006]

Since the conventional haze transmittance measuring device is constructed as described above, the lenses 5, 1
The surface of No. 0 is exposed to the measured air 3 whose surface is dirty for a long time. Therefore, even if the dustproof cylinders 6 and 8 are provided, the surfaces of the lenses 5 and 10 are eventually soiled, and correct measurement cannot be performed. There is a problem that the surfaces of the lenses 5 and 10 need to be cleaned. Further, even when a transparent plate (film-like) is provided on the front surface of the lenses 5 and 10 to prevent dust, the transparent plate is contaminated, and there is essentially the same problem as described above.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a fume transmittance measuring apparatus capable of reducing dirt on a lens.

[0008]

According to another aspect of the present invention, there is provided a haze transmittance measuring device which blows clean air pressurized to the front surface of at least one of a lens of a light projecting portion and a lens of a light receiving portion. It is equipped with a blower.

According to a second aspect of the present invention, there is provided a haze transmittance measuring device comprising a water supply means for flowing cleaning water to a transparent plate provided on the front surface of at least one of the lens of the light projecting section and the lens of the light receiving section or in front of this lens. It is provided.

According to a third aspect of the present invention, there is provided a fume transmittance measuring device, wherein a shutter is provided on the front side of at least one of the lens of the light projecting portion and the lens of the light receiving portion, and a control device for opening and closing the shutter is provided. Is.

[0011]

In the blower according to the first aspect of the present invention, the clean air pressurized in front of the lens is blown, so that the surface of the lens does not become dirty.

In the water supply means according to the second aspect of the present invention, since water is caused to flow on the front surface of the lens or the transparent plate, dirt on the lens or the transparent plate is washed.

In the shutter according to the third aspect of the present invention, the air comes into contact with the lens only when it is opened, so that the lens is less likely to become dirty.

[0014]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 shows the invention of claim 1, parts corresponding to those in FIG. In FIG. 1, 15 is clean air, 16 is a blower that pressurizes the clean air 15, and 17 is clean air that is pressurized by the blower 16 and is blown to the front surface of the lens 5. Although not shown, a blower is also provided on the front side of the lens 10 in the light receiving section 2.

Next, the operation will be described. The air 15 cleaned by a filter (not shown) or the like is sent to the blower 16
And is discharged as clean air 17 pressurized in the dustproof cylinder 6 by. Therefore, the air pressure inside the dustproof cylinder 6 becomes higher than that outside the dustproof cylinder 6, and the measured air 3 that is dirty outside the dustproof cylinder 6 cannot enter the dustproof cylinder 6. Therefore, the surface of the lens 5 is always in contact with clean air and does not become dirty. The same applies to the light receiving unit 2.

Example 2. FIG. 2 shows an embodiment of the invention of claim 2. In the first embodiment, the case where the lens 5 is prevented from being contaminated by the air contaminated by the air pressure has been described.
As shown in FIG. 2, a transparent plate 18 made of glass or the like is provided on the front surface of the lens 5, and clean water 20 is supplied from a water supply pipe 19 provided as a water supply means, and a thin film 21 of water is provided on the surface of the transparent plate 18.
As a water 22 through the drain pipe 23. As a result, the dust that has entered the dustproof cylinder 6 is
At the same time, the lens 5 is discharged to the outside and the surface of the lens 5 is isolated from the dirty air, so that the surface of the lens 5 is not soiled. In addition, the transparent plate 18 is not particularly provided, and clean water 2
The same effect can be expected by providing a water film of 0 directly on the surface of the lens 5. Further, the light receiving unit 2 may have the same configuration.

Embodiment 3. FIG. 3 shows an embodiment of the invention of claim 3. In FIG. 3, mechanical shutters 24 and 25 are provided in front of the lenses 5 and 10, respectively. The shutters 24 and 25 are opened only during the measurement, and the shutters 24 and 25 are closed when the measurement is completed. Then, the shutters 24 and 25 remain closed until the next measurement time comes. During this time, the output signal of the photoelectric tube 11 and the output signal 13 of the calculator 12
Is zero, the signal holding device 2
6, the output signal 27 is held while the shutters 24 and 25 are closed, and the output signal 27 is apparently continuously obtained.

Further, the shutter 24 of the light projecting unit 1 and the light receiving unit 2
A control device 28 is provided to open and close the shutter 25 in synchronization with. According to the above, the lenses 5 and 10 are opened to dust that jumps in through the dustproof cylinders 6 and 8 only for a very short time during measurement, so that the surfaces of the lenses 5 and 10 are less likely to be soiled than before.

[0019]

As described above, according to the first aspect of the invention, since the clean air blowing means is provided on the front side of the lens, the lens can be reliably prevented from being contaminated. There is an effect that the measurement accuracy and reliability of the haze transmittance can be improved.

According to the second aspect of the present invention, since the water is made to flow on the lens surface or the transparent plate arranged in front of the lens, it is possible to surely prevent the lens from being soiled, and to improve the measurement accuracy and reliability. There is an effect that can be improved.

According to the third aspect of the present invention, since the shutter is provided in front of the lens to open and close the lens, there is an effect that the surface of the lens is less likely to be soiled.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a first embodiment of the present invention.

FIG. 2 is a sectional side view showing a second embodiment of the present invention.

FIG. 3 is a sectional side view showing a third embodiment of the present invention.

FIG. 4 is a sectional side view of a conventional dustproof device for a fume transmittance measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting part 2 Light receiving part 3 Measured air 4 Light source 5, 10 Lens 11 Phototube (photoelectric element) 16 Blower 17 Clean air 18 Transparent plate 19 Water pipe (water sending means) 20 Clean water 24, 25 Shutter 28 Control device

Claims (3)

[Claims] 1. A light projecting section for projecting light from a light source into the air to be measured through a lens, and light from the light projecting section to be received through the air to be measured, and a photoelectric element via the lens. In a fume transmittance measuring device having a light-receiving part to be incident, a blower for sending pressurized clean air to a surface side of the lens of the light-projecting part, the lens of the light-receiving part, or both lenses that comes into contact with the measured air. A fume transmittance measuring device characterized by being provided. 2. A light projecting section for projecting light from a light source into the air to be measured through a lens, and light received from the light projecting section through the air to be measured and incident on a photoelectric element through the lens. In a fume transmittance measuring device having a light receiving section for
Water transmitting means for flowing clean water is provided on a surface of the lens of the light projecting section, the lens of the light receiving section, or both of the lenses that comes into contact with the air to be measured or a transparent plate provided in front of this surface. Fume transmittance measuring device. 3. A light projecting section for projecting light from a light source into the air to be measured through a lens, and light from the light projecting section to be received through the air to be measured, and to a photoelectric element via the lens. In a haze transmittance measuring device having a light-receiving part to be incident, a shutter provided on a surface of the lens of the light-projecting part, the lens of the light-receiving part, or both lenses that comes into contact with the air to be measured, and the shutter is opened and closed. A fume transmittance measuring device characterized by being provided with a control device.