JPH10300558A - Device for measuring liquid level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an explosion-proof type device for measuring liquid level which can realize accurate and stable measurement regardless of kind of liquid. SOLUTION: An optical range finder 2 which is provided a light emitting part and a light receiving part and measures a distance to an object to be measured according to the duration from emission of light emitted from the light emitting part to arrival thereof to the light receiving part after reflection on the object is provided on the top part of a tank 1 for storing a liquid. In this case, a reflection body 4 is fitted to the upper part of a float 3 floating along an elevating guide 11, thereby allowing a light emitted from the light emitting part of the optical range finder 2 to fall on the light receiving part thereof after reflection on the reflection body 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level measuring device, and more particularly to a liquid level meter using an optical distance meter.

[0002]

2. Description of the Related Art A light emitting unit and a light receiving unit are provided.
A so-called optical distance meter (also known as a lightwave rangefinder) that measures the distance to the object by measuring the time required for the light from the light-emitting unit to reflect off the object and return to the light-receiving unit. The optical liquid level gauge, which is provided at the top of the tank and measures the liquid level with the liquid level in the tank as the object to be measured, has various advantages, but the reliability is not sufficient because of the following disadvantages. However, it has not yet become widespread. (a) Since the measurement cannot be performed unless the direction of the light from the light emitting unit is exactly perpendicular to the liquid surface, the measurement becomes difficult when the liquid surface swings. Also, it is difficult to adjust the mounting angle when installing,
Even once adjusted, measurement tends to be impossible if the mounting angle changes due to deformation of the tank. (b) When a small wave or foam is generated on the liquid surface,
Light may be irregularly reflected, making measurement impossible. (c) The reflectivity of light differs depending on the type of liquid, but it is difficult to apply a liquid with a low reflectivity to a large tank with a long length measurement because the reflected light is weak. (d) If the transparent plate (such as glass) that forms the outer wall of the light emitting unit and light receiving unit of the optical rangefinder becomes dirty, the light will be absorbed and weakened, making it impossible to receive reflected light and making measurement impossible. is there. In the case of a liquid having a low reflectance, measurement becomes particularly difficult. (e) In order to solve the above problems (c) and (d), intense light must be used. However, in order to obtain intense light, it is necessary to apply large electric energy to the light emitting element. On the other hand, if the electric energy required for measurement is large, it is difficult to provide explosion-proof properties, and it cannot be used for flammable liquids.

The optical level gauge has no mechanical parts, is easy to maintain, has high durability, and has high measurement accuracy.
There are various advantages, and it is desired to realize an optical liquid level meter that has solved the above problems.

[0004]

The object of the present invention is to provide the above (a) to
The object of the present invention is to solve the problem (e) and realize a highly reliable optical level gauge.

[0005]

In order to achieve the above object, a liquid level measuring apparatus according to the present invention comprises a light emitting section and a light receiving section, wherein light from the light emitting section is reflected by an object to be measured and the light receiving section is provided. An optical distance meter that measures the distance to the object to be measured by the time to return to the top is provided at the top of the tank that stores the liquid, and a reflector is attached to the top of the float that floats on the liquid level in the tank with the lifting guide, The light from the light emitting unit of the optical rangefinder is reflected by the reflector of the float and is incident on the light receiving unit of the optical rangefinder.

In a liquid level measuring apparatus according to the present invention, the reflector is constituted by a reflector or a reflector.

Further, the liquid level measuring apparatus according to the present invention comprises a light emitting portion and a light receiving portion, and the liquid level measuring device measures the time from when the light from the light emitting portion is reflected by the object to be measured and returns to the light receiving portion. An optical rangefinder that measures the distance to the object is provided at the top of the tank that stores the liquid, and on the top of the float that floats on the liquid level in the tank with the elevating guide, the optical system that makes the emitted light parallel to the incident light A three-dimensional reflector made of a prism is attached so that light from the light emitting unit of the optical rangefinder is reflected by the reflector of the float and is incident on the light receiving unit of the optical rangefinder.

[0008]

Examples of the present invention will be described below. In the liquid level measuring and measuring apparatus of the present invention, the float 3 having the reflecting mirror 4 which is a reflecting plate as a reflector as shown in FIG. The light from the optical rangefinder 2 provided on the top of the tank 1 in a floating state is reflected by the reflecting mirror 4, and the distance from the top of the tank to the reflecting mirror is determined to measure the liquid level.

That is, in FIG. 1, a reflecting mirror 4 is provided above a float 3, and light L emitted from a light emitting unit (not shown) of an optical distance meter 2 attached to the top of a tank is omitted.
₁ is reflected by the reflection mirror 4, returns to the light receiving unit and the reflected light L ₂ is not shown of the optical rangefinder, the tank top from the time the when the light reciprocates between the distance meter and the reflecting mirror Then, the distance between the liquid mirror and the reflecting mirror is obtained, and the length between the liquid surface and the reflecting mirror is corrected to obtain the liquid level. As the reflecting mirror, a mirror having a high reflectance and a surface that is not easily stained is used.

A balance weight 5 is provided below the float 3 so that the center of gravity of the float 3 is below the center of buoyancy. By doing so, even if the float is tilted due to the oscillation of the liquid, the restoring force is generated and it returns to horizontal again, and even if ripples or bubbles are generated on the liquid surface, it will remain stationary and will not interfere with the measurement. Not at all.

As described above, the object to be measured is the reflecting mirror 4 having a high reflectance, and the float 3 is provided with the balance weight 5 so as to have resilience so that the reflecting mirror is always parallel to the liquid surface. Thereby, the reflected light of sufficient intensity returns to the light receiving section of the range finder with a high probability, and the energy of the light emitted from the light emitting section can be reduced, so that the conventional liquid surface is directly measured. The problem of the optical level gauge is remarkably improved, and a highly practical optical level gauge can be realized.

Further, depending on individual conditions such as the structure of the tank and the liquid to be measured, reliability and practicality can be further improved by adding the following improvement measures. (a) In the case of an opaque liquid or a viscous liquid, the reflecting mirror 4 is mounted on a rod-like support 6 erected on a float so that the reflecting mirror 4 is positioned sufficiently higher than the liquid surface. The mirror is not covered with liquid, so that the mirror is not dirty and the normal reflection function is not impaired. (b) As shown in FIG. 2, when the optical distance meter is attached to the top of a pipe (stilling well) 7 as a float elevating guide vertically set in a tank, the float is placed inside the pipe. When floating on the liquid surface, as shown in FIG. 3, three or more protrusions 8 whose length from the center to the tip of the float is slightly shorter than the inner radius of the pipe are projected from the outer periphery of the float, and the float is always in the pipe. Being centered prevents light from the tank's top rangefinder from coming off the reflector, improving reliability. (c) When the place where the float 3 floats is on the open liquid level in the tank, as shown in FIG. 4, the float rises and falls through the vertical hole 10 of the guide piece 9 provided on the side of the float. Two or more vertical wires (guide wires) 11 as guides are stretched in the tank to prevent the float from moving in the horizontal direction and rotating, thereby improving reliability. In the figure, reference numeral 12 denotes a wire anchor weight. (d) The vaporized liquid is applied to the light-emitting and
If there is a possibility of dew condensation on the light transmitting wall and scattering of the light, a mechanical wiping device (wiper) is attached to the transparent wall of the light transmitting wall to remove the dew. (e) For a tank that needs to be once pulled up to the top of the tank or taken out of the tank for maintenance or other purposes, the float 3 has a magnet M built in as shown in FIG. A wire 15 with a magnetic metal fitting 14 attached to the tip is hung down from the maintenance side hole 13 of the part, the metal fitting is attracted to the float by a magnet, and the float is pulled up to the top of the tank by pulling the wire 15. I do.

In the above embodiment, an example in which a reflecting mirror is used as a float reflector is shown. However, as shown in FIG. 6, a three-dimensional reflector 16 composed of a reflecting prism in which emitted light and incident light are parallel as shown in FIG. There are times when you use. As the prism of the three-dimensional reflector, for example, an inverted triangular pyramid having a shape in which the lower three side surfaces of a cylindrical body 16 made of a transparent material are tapered and tapered downward as shown in FIG. 7 is used.

In this three-dimensional reflector, light incident from the upper end is reflected by the first tapered portion 16a into the second tapered portion 1a.
The light reflected to 6b and further reflected at the second tapered portion is reflected upward at the third tapered portion 16c and emitted from the upper end surface in parallel with the incident light.

At this time, in order to prevent light attenuation, a light-shielding film such as a paint film or a metal film may be formed on the surface of each of the tapered portions 16a, 16b, and 16c of the three-dimensional reflector. Also,
In the case of a three-dimensional reflector, the outgoing light only needs to be parallel to the incident light.

[0016]

The light from the light emitting part of the optical distance meter provided on the top of the tank is reflected by the reflector attached to the float floating on the liquid surface, enters the light receiving part of the optical distance meter, and emits light. The liquid level in the tank is measured from the time until the light from the section returns to the light receiving section.

Therefore, the light from the light emitting section of the optical rangefinder returns to the light receiving section with a higher probability than the conventional liquid level measuring apparatus in which the liquid level is directly non-measured, so that the light reflectance is reduced. Accurate liquid level measurement can be performed even with small liquids, and the energy of the light emitted from the light emitting unit is small, and there is no need to apply large electric energy to the light emitting element, and it is flammable. Explosion-proof material that can be used safely in a tank for storing liquid.

Further, since the float is guided by the lifting guide, even if the liquid surface swings, the reflector keeps a substantially stationary state,
Stable measurement can be performed.

Further, since the light emitted from the three-dimensional reflector is kept parallel to the incident light by using the three-dimensional reflector, the light emitted from the three-dimensional reflector can be emitted even if the float is tilted due to the fluctuation of the liquid surface. The liquid level can be accurately returned to the light receiving section, and accurate liquid level measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a perspective view showing an example of a guide wire as a float elevating guide.

FIG. 5 is a longitudinal sectional view showing still another embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing still another embodiment of the present invention including a three-dimensional reflector.

FIG. 7 is a perspective view showing an example of a three-dimensional reflector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tank 2 ... Optical distance meter 3 ... Float 4 ... Reflection mirror 5 ... Balance weight 6 ... Bar-shaped support 7 ... Stilling well 8 which is a lifting guide of a float 8・ ・ ・ Float projection 9 ・ ・ ・ Float guide piece 10 ・ ・ ・ Vertical hole 11 ・ ・ ・ Guide wire as a float elevating guide 12 ・ ・ ・ Anchor weight 13 ・ ・ ・ Maintenance side hole 14 ・ ・ ・Metal fittings 15: Wire 16: Three-dimensional reflector 16a, 16b, 16c: Tapered part of three-dimensional reflector

Claims (3)

[Claims] An optical distance meter that includes a light emitting unit and a light receiving unit and measures a distance to the object to be measured based on a time required for light from the light emitting unit to be reflected by the object to be measured and return to the light receiving unit. Provided at the top of the tank to be stored, a reflector is attached to the upper part of the float that floats on the liquid level in the tank with the elevating guide, and light from the light emitting unit of the optical rangefinder is reflected by the reflector of the float. A liquid level measuring device that is incident on a light receiving section of an optical distance meter. 2. The liquid level measuring device according to claim 1, wherein the reflector is constituted by a reflector or a reflector. 3. An optical distance meter that includes a light emitting unit and a light receiving unit, and measures a distance to the object to be measured based on a time until light from the light emitting unit is reflected by the object to be measured and returns to the light receiving unit. A three-dimensional reflector made of a prism of an optical system in which outgoing light is parallel to incident light is mounted on a float provided at the top of a tank to be stored and floated on a liquid level in the tank by a lifting guide, and the optical rangefinder is provided. A liquid level measuring device in which light from the light emitting section is reflected by the reflector of the float and is incident on the light receiving section of the optical rangefinder.