JPS5826226A - Detector for liquid level - Google Patents

Abstract

PURPOSE:To eliminate errors in detection owing to sticking of water drops in a detector for liquid levels wherein there is reflection of incident light when a prism is in liq. and there is reflection of the incident light when the prism is out of the liq., by providing a projecting part which does not interfere the conducting passage for light to the prism. CONSTITUTION:A prism 1 consisting of a conductive passage forming part 1b which forms a passage for light and a water drop sticking part 1c is provided in a vessel 7 in order to measure the level of the liq. 8 in the vessel 7. The light from a light emitting element 4 is made incident to the prism 1 via an optical connector 61, an optical fiber 31, and a collimator 21. The incident light is totally reflected in a direction X, and is detected with a photodetector 5 via a collimator 22, an optical fiber 32 and an optical connector 62. When the prism 1 is in the liq., the incident light advances into the liq. without total reflection by a leading end part 1a, and when the prism is out of the liq., the light is totally reflected thereby and is detected with the photodetector 5, whereby the level of the liq. is detected. Since the water drops that may stick on the prism 1 stick only on the part 1c that has no relation with the passage of the light, the erroneous detection owing to the sticking of water drops is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detection device constructed by applying the principle of optical catadioptric refraction and having nine prisms.

Conventionally, liquid level detection devices have been considered indispensable for controlling liquid volume, and many methods have been implemented, but the latest method is a prism-type liquid level detection that applies the principle of optical catadioptric refraction. The device used is a columnar prism having a right-angled wedge-shaped tip 1a, and is made of a material such as glass or epoxy resin that is transparent to light and has a high refractive index for the light of the liquid to be detected. 21, 22 are collimators, 31,
32 is an optical fiber, 4 is a light-emitting element such as a light-emitting diode, 5 is a photodiode or a light-receiving element such as a phototransistor, and 61 and 62 are the optical fiber 31 and the light-emitting element pre-arrangement, and the optical fiber 32 and the light-receiving cable 5. The optical connector to be connected is shown. When detecting the liquid level of the liquid 8 in the container 7 using this liquid level detection device, when the prism l of the liquid level detection device in the throat of FIG. 1(A) is outside the liquid, the light emitting element The light emitted from the optical connector 61. Optical fiber 31. The light enters the prism 1 via the collimator 21 and is totally reflected at the tip n of the prism 1 in the direction indicated by the solid arrow X, and is received by the light receiving element 5 via the collimator 22, the optical fiber 32, and the optical connector 62.

Next, when the prism 1 of the liquid level detection device is immersed in the liquid as shown in FIG. Proceed into the liquid in the direction shown, and remove the collimator blades and the light 7 eyeper 32.
, the amount of light received by the light receiving element 5 via the optical connector 62 is almost negligible. The liquid level position can be detected by measuring the amount of light received by the light receiving element 5 using such a difference in the amount of light received by the light receiving element 5.

However, the above-mentioned liquid level detection device has the following drawbacks when the prism is once immersed in the liquid and then pulled up from the liquid and placed outside the liquid. That is, as shown in FIG. 1(C), a droplet 9 of the liquid 8 to be detected is placed on the tip of the prism 1.
remains, and due to the influence of this, the light from the light emitting element premonition passes through prism 1.
Even if the water enters the water droplet, it does not follow the path shown in FIG. .

However, the reflected light that has entered the prism 1 does not enter the collimator blades and travels in a different direction, so that the reflected light does not enter the light receiving element 5. For this reason, even though the prism of the liquid level detection device is not immersed in the liquid 8, it operates as if it were in the liquid 8, resulting in erroneous detection.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a liquid level detection device that does not make false detections due to water droplets even immediately after they are removed from the liquid.

According to the present invention, this purpose is to form a light guide path for incident light and reflected light using a light-transmitting columnar prism, and to provide a liquid level detection device that includes a light emitting element and a light receiving element at both ends of this guide path. This is achieved by configuring the prism with a guide path forming part that forms a light guide path, and a water drop adhesion part that does not block the light guide path and protrudes from the guide path forming part.

Examples of the present invention will be described below based on the drawings (A).
,tβ之(C/)ru. 2I is a schematic diagram showing the liquid level inspection and the configuration of the device which is an embodiment of the present invention. FIG. When the device is immersed in the liquid to be detected, Fig. 2 (C) shows the case where the device is once immersed in the liquid to be detected and then pulled up again from the liquid to be detected and is outside the liquid. The same reference numerals are given to the members. The improvement according to the present invention is that the prism 1 is composed of a guide path forming part 1b that forms a light guide path for incident light and reflected light, and a water droplet adhesion part IC that protrudes from the guide path forming part lb. This point is that a protrusion 1O is provided at the direct expansion wedge-shaped tip of the prism 1 so as not to block the light guide path. When the prism l is outside the liquid, that is, in Fig. 2 (A
), the traveling direction of the light is the same as in the conventional case, and the protrusion 10
Proceed in the direction of solid arrow X without being obstructed by. Most of the light from the light-emitting element reaches the light-receiving element δ, and it is detected that the device is outside the liquid. In addition, when the prism 1 of the device is immersed in the liquid, the traveling direction of the light is the same as in the conventional case, as shown in Fig. 2 (B), and is not obstructed by the protrusion 10. 5- Solid line arrow Proceed in the Y direction. In this case, the amount of light from the light emitting element +4 hardly reaches the light receiving element 5, and it is detected that the prism is immersed in the liquid. Next, if the prism 1 of the device is once immersed in the liquid and then pulled out of the liquid again and drops to the liquid level, the liquid adhering to the prism will flow down and collect on the protrusion 10, as shown in FIG. 3(C). This becomes a water droplet 91. In this case, the light emitted from the light emitting element +4 enters the prism 1, is totally reflected at the tip 1a of the prism 1, travels in the direction indicated by the solid arrow X, and is finally received by the light receiving element 5.

In other words, the light guide path by the water droplet 91 is not obstructed, as shown in FIG.
Following the same direction of movement as in A), most of the light from the light emitting element 4 reaches the light receiving element 5, and it is detected that the prism is outside the liquid.

The shape of the protrusion 1O is that when the prism 11 is prismatic as shown in FIG. If it is a cylinder, it is preferable that the protrusion 3o#'i has a conical shape.

According to the present invention described above, by configuring the prism with a guide path 6- forming part and a water droplet adhesion part, when the prism is immersed in liquid and is separated from the liquid surface, errors caused by the presence of pre-drops can be avoided. This method has the advantage that no detection occurs and accurate liquid level detection can be performed.

[Brief explanation of the drawing]

(A), (B), α) 1st A - A schematic diagram showing the structure of a liquid level detection device with a conventional structure and the structure of a liquid level detection device which is an embodiment of light, and the path of light, Figure 2 (B), Figure 2 (C) is an explanatory diagram of the operation, Figure 3 (A) is a perspective view of a prismatic prism, Figure 3 (B) is a perspective view of a cylindrical prism. It is a diagram. Ma2 1.11. Spear...prism, -...right-angled wedge-shaped tip, lb...guiding path forming part, IC...water droplet attachment part, 4
...Light emitting element, O/1 (A (B), (C rough 2)
Diagram 3

Claims (1)

[Claims] 1) In a liquid level detection device in which a light guide path for incident light and reflected light is formed using a light-transmitting columnar prism, and a light emitting element and a light receiving element are provided at both ends of this guide path. , a guide path forming portion detection device that uses the prism to form a light guide path. A liquid level detection device characterized in that the attachment part is horizontal. A liquid level detection device whose el& is defined by the conical shape of the fitting part.