JPH051935A - Control device for liquid level utilizing polarizing characteristic of light - Google Patents

Abstract

PURPOSE:To control a liquid level with a safe and reliable method to oils, organic solvents, liquefied fuels, and chemicals, as the characteristic of liquid, under environments uncontrollable by a float switch or float-less switch, or in a sealed narrow vessel or a vessel charged with a corrosive gas. CONSTITUTION:With respect to a liquid in a transparent cylindrical vessel by glass or resin molding, as a means for controlling a level for water, oils, or chemicals, a transmission type photoelectric sensor is set near on the line extending from one end of a cylindrical vessel section as a base point to 30 deg.-150 deg. at a right-handed angle or the line extending to 210 deg.-330 deg., and the liquid level is controlled by utilizing the difference in refraction index of light between gas and liquid. Since the mechanism of detection is based on not an analogous change but a digital change from L to H, a stable certain control input can be provided. Further, the life of the sensor is extended because of non-contact detection, and chemicals corroding even metals can be safely and certainly controlled.

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] It can be used for controlling the liquid level of oil, organic solvent, chemicals, etc. in a narrow closed container where a float switch or a floatless switch cannot be used, or a container with corrosive gas.

[0002]

2. Description of the Related Art As a method for controlling the liquid level, there are a float switch, a floatless switch, a capacitance type proximity switch and the like. The floatless switch is generally known and well known, in which an electrode is placed in a water tank and a weak current is caused to flow in water to know the water level between the electrodes.
(Fig. 3) These are mainly used for controlling the water level.
Capacitance type proximity switches can be used for anything other than water, but their operation is unstable because they require analog adjustment.

[0003]

[Problems to be Solved by the Invention] An environment that cannot be controlled by a floatless switch, a tightly closed container, a container filled with corrosive gas, and physical properties such as oil, organic solvent, liquefied fuel, and chemicals. The purpose is to control the liquid level with a safe and reliable method for chemicals.

[0004]

A liquid contained in a transparent cylindrical container can be used as long as the transparency of the cylindrical container is not impaired. As a method, with one end of the cross section of the cylindrical container as a base point 0, a transmission type photoelectric sensor is set on a line passing from 30 ° to 150 ° at a right-handed angle or a line passing from 210 ° to 330 °. The liquid level is controlled by utilizing the difference in the refractive index of light.

[0005]

The cylindrical transparent container is made of glass or acrylic. If you set the emitters and receivers of the transparent photoelectric sensor on the left and right sides of this container as described in the previous section, you can see the emitters through the glass when viewed from the light receiving side. Since there is nothing to block the light, the light emitter / receiver facing each other is in the light receiving ON state. When a transparent liquid, water or oil is added, the water or oil level rises and exceeds the level of the light emitter / receiver. At this time, since the cylindrical container has a circular cross section, when the liquid is filled therein, light is refracted by a function similar to that of the lens, and the projector seen from the light receiver side becomes invisible from the field of view. In other words, it means that the light is blocked. In the case of gas, the light that went straight was refracted by the liquid filling the circular portion of the cylindrical container. Since this mechanism is not an analog curve but a stepwise digital change, a change between H and L, it can be a stable input when treated as a control input.

[0006]

EXAMPLES As a typical example of a sealed transparent pressure vessel, there is an Euler set (oil supply device), and an example thereof will be described. FIG. 1 shows a transmissive photoelectric sensor attached to an Euler set. FIG. 2 shows the mounting position of the sensor. The base point is 0 at one end of the cross section of the cylindrical container.
And, on the line that goes from 30 ° to 150 ° at the right angle,
Also, set the emitter / receiver of the transmission type photoelectric sensor on the line that goes out from 210 ° to 330 °. The control level is determined by the height to be set. In FIG. 4, a glass tube level gauge is attached to the side of the metal tank. The upper and lower ends communicate with the inside of the container. The photoelectric sensor is set on this level gauge in the same manner as described with reference to FIG.
The diameter of the glass tube must be at least about 25φ for the sensor to work effectively. Considering the case of housing in a metal case to protect the glass tube, there is an advantage that the sensor can be attached if the semicircular portion of the glass tube is exposed and the level can be visually checked. However, for complete protection, the entire surface should be housed in a metal case and a small window should be opened at the position where the sensor should be set, as shown in FIG.

[0007]

Even if an attempt is made to detect the liquid level of a transparent liquid in a pressure vessel which is closed like an Euler set, no suitable method can be found. The basic principle of detecting with a photoelectric sensor by utilizing the difference in the refractive index of light between gas and liquid can be widely applied in addition to the Euler set. The first advantage is that the detection mechanism is not an analog curve change but a digital change that goes up one step, and the light refracts as soon as the liquid level reaches the sensor. The projector seen from the light receiving side disappears from the field of view, that is, the light receiving state becomes a light blocking state, so that it is electrically changed from L to H, and the control input becomes stable and highly reliable. Therefore, once set, stable liquid level control can be performed without error during long-term use. Secondly, the use of a photoelectric sensor enables non-contact detection, which is durable for many years because the sensor has no wear elements. However, the greatest advantage of non-contact is as follows. In other words, being able to detect the level without touching the liquid surface is a condition absolutely necessary for chemicals and the like. For example, it is possible to safely and reliably control the liquid level even with respect to chemicals that corrode metals such as sulfuric acid and nitric acid.

[Brief description of drawings]

FIG. 1 is a side view showing a transmission photoelectric sensor attached to an oiler set.

FIG. 2 is a cross-sectional view in which a transmission photoelectric sensor is attached to an Euler set.

FIG. 3 is a side view showing a floatless switch attached to a water tank.

FIG. 4 is a side view in which a glass tube level gauge is attached to a water tank.

FIG. 5 is a plan view showing a state in which the level gauge is covered with a metal case and a hole is opened at a mounting position of the sensor.

[Explanation of symbols]

 A Transmission type photoelectric sensor Emitter B Transmission type photoelectric sensor Receiver 1 Euler set Transparent cylindrical container 2 Water tank 3 Floatless switch electrode sensor 4 Glass tube level gauge 5 Window

Claims (1)

Claims: 1. A liquid in a transparent cylindrical container made of glass or resin, in particular with regard to a transparent liquid, water or oil,
As means for controlling the liquid level of chemicals, etc., with one end of the cross section of the cylindrical container as the base point 0, on that line from the position of 30 ° to 150 ° in the clockwise direction, or from 210 ° to 330 °. A control device with a transmissive photoelectric sensor installed near it to control the liquid level by utilizing the difference in the refractive index of light between gas and liquid.