JP2978107B2 - Liquid level detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device for detecting a liquid level in a transparent pipe.

[0002]

2. Description of the Related Art For example, in detecting a liquid level in a tank, a liquid level detecting device is attached to a transparent pipe connected to the tank, and a liquid level in the transparent pipe (a liquid level at the same level as in the tank). It has been done to detect. As shown in FIG. 11, this liquid level detecting device has a configuration in which light is projected from the light projecting means 1 to the transparent pipe A and light reflected from the transparent pipe A is received by the light receiving means 2.

In this configuration, an arc-shaped concave portion 3 is formed in a holder having the light projecting means 1 and the light receiving means 2, and when detecting the liquid level, the support portions (both ends) 3a of the concave portion 3 and 3b is brought into contact with the transparent pipe A, and light is projected from the light projecting means 1 with the holder stably mounted on the transparent pipe A.

Here, when the liquid surface is at a predetermined height in the transparent pipe A, the projection light from the light projecting means 1 travels substantially straight in the liquid through the inner peripheral surface of the transparent pipe A. Therefore, since the amount of light received by the light receiving means 2 is lower than the reference value, it is determined that there is liquid. When there is no liquid surface at a predetermined height in the transparent pipe A, the projection light from the light projecting means 1 is reflected by the inner peripheral surface of the transparent pipe A to the light receiving means 2 side. Therefore, the light receiving means 2
Is greater than the reference value, it is determined that there is no liquid.

[0005]

In the conventional liquid level detecting device, as shown in FIG. 11, the supporting portions 3a and 3b
The light was projected aiming at the middle part of. Therefore, FIG.
As shown in (1), when the outer diameter of the transparent pipe A changes, the light projection point on the transparent pipe A changes, and there is a possibility that the light may not hit the inner peripheral surface of the transparent pipe A. Therefore,
As the beam of the projected light and the light receiving area of the light receiving means 2 are enlarged, the detection area is enlarged to cope with the difference in the outer diameter of the transparent pipe A.

However, in the liquid level detecting device,
Bubbles rising in the transparent pipe A enter the detection area,
The projection light may be reflected by these bubbles. On the other hand, when the detection area of the apparatus is expanded, the light receiving means 2 receives the reflected light from the air bubbles, and it is erroneously determined that there is no liquid even though there is a liquid level at a predetermined height in the transparent pipe A. Possibilities arise. In particular, as shown in FIG.
When the outer diameter of the transparent pipe A is small, the ratio of the detection area occupying the hollow portion of the transparent pipe A increases, so that the risk of malfunction of the apparatus increases.

In order to prevent this malfunction, it is effective to reduce the beam of light and the light receiving area of the projection light and narrow the detection area. However, when the detection area is narrowed, the outer diameter of the transparent pipe A that can be supported is restricted.
As described above, providing a width for the outer diameter of the transparent pipe A that can be handled is contradictory to preventing malfunction, and there has been a liquid level detection device that can solve both at once. It was not.

Further, in the conventional liquid level detecting device, as shown in FIG. 11, a light shielding means 4 is provided on a holder to block the projection light reflected on the outer peripheral surface of the transparent pipe A.
The projection light reflected on the outer peripheral surface of the transparent pipe A enters the light receiving means 2 to prevent the apparatus from malfunctioning.

However, in the prior art, the light shielding means 4 has been arranged at an intermediate portion between the support portions 3a and 3b. For this reason, when the device is mounted on the transparent pipe A having a small diameter, the light shielding means 4 is so arranged that the distal end thereof comes into contact with the outer peripheral surface of the transparent pipe A.
It was necessary to set the length dimension. Therefore, when the apparatus is mounted on the transparent pipe A having a large diameter, a gap is formed between the tip of the light shielding means 4 and the transparent pipe A, so that the projection light reflected on the outer peripheral surface of the transparent pipe A is received through the gap. There is a possibility that light may enter the means 2. Then, the ratio of the difference in the amount of light received due to the presence or absence of the liquid to the amount of light received by the light receiving means 2 decreases, so that the S / N ratio decreases,
As a result, it is difficult to detect a stable liquid level.

There are the following methods (1) and (2) for preventing the projection light reflected on the outer peripheral surface of the transparent pipe A from entering the light receiving means 2. (1) With the movement of the light shielding means 4 according to the outer diameter of the transparent pipe A, the tip of the light shielding means 4 is constantly brought into contact with the transparent pipe A. (2) For the transparent pipe A having the largest outer diameter, the light projecting means 1 is so arranged that the reflected light toward the light receiving means 2 is reduced as much as possible.
To the transparent pipe A. Then, since the light projecting point is shifted inward of the transparent pipe A with respect to the transparent pipe A having a small diameter, the reflected light toward the light receiving means 2 is further reduced.

However, in the case of the configuration (1), it is necessary to provide a mechanism for moving the light shielding means 4 to the holder, which complicates the configuration and, as a result, increases the cost. At the same time, every time the outer diameter dimension of the transparent pipe A changes, the operator needs to move the light shielding means 4, so that it is difficult to say that it is practical in general. In addition, in the case of the configuration (2), particularly, the ratio of the detection area occupying the hollow portion of the small-diameter transparent pipe A is increased, so that the risk of malfunction of the device due to bubbles is further increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a transparent pipe having an outer diameter having a width and a malfunction to be prevented at once. It is to provide a liquid level detecting device. The second object is to stably detect the liquid level by blocking the light reflected on the outer peripheral surface of the transparent pipe without causing a malfunction due to air bubbles, a complicated configuration due to the provision of the moving mechanism, and the like. It is to provide a liquid level detecting device.

[0013]

Liquid level detection device according to claim 1, wherein Means for Solving the Problems] has been made in order to achieve the first object, and the holder, et Re cross section provided in the holder circular A pair of support portions that come into contact with the outer peripheral surface of the transparent pipe,
A light projecting means provided on the holder, and a light receiving means provided on said holder, said light projecting means said transparent
The transparent pipe among the lines parallel to the axis of the pipe
Located on the inner peripheral surface of the
Projecting light onto a predetermined portion of the
When there is no liquid level in a predetermined part of the
A predetermined portion in the transparent pipe where the projected light is reflected on the peripheral surface
When there is a liquid level, the projected light strikes the inner peripheral surface of the transparent pipe.
Through the liquid so as to travel substantially straight through the liquid.
The step receives light reflected on the inner peripheral surface of the transparent pipe.
It is characterized in that it is arranged as follows .

According to the above means, the axis of the transparent pipe is
Of the lines parallel to it, located on the inner peripheral surface of the transparent pipe and
Light is projected onto a predetermined portion, which is located near one of the support portions . For this reason, the variation of the projection point due to the difference in the outer diameter of the transparent pipe is reduced as much as possible, and it is not necessary to enlarge the detection area. Therefore, malfunction of the apparatus due to the reflected light from the bubbles is minimized for the transparent pipes having various outer diameters.

A liquid level detecting device according to a second aspect is provided to achieve the second object, and the light projecting means comprises:
One of the inner peripheral portions of the transparent pipe projects light in the vicinity of one of the supporting portions, and one of the supporting portions receives light reflected from the outer peripheral surface of the transparent pipe among the light projected from the light emitting means. It is characterized in that it is provided between the light projecting means and the light receiving means so as to block light from entering the means.

According to the above means, one of the supporting portions is in contact with the outer peripheral surface of the transparent pipe without being affected by the outer diameter of the transparent pipe, and functions as a light shielding means. For this reason, the projection light reflected on the outer peripheral surface of the transparent pipe does not enter the light receiving means, and the ratio of the difference in the amount of light received due to the presence or absence of the liquid to the amount of light received by the light receiving means is reduced. Therefore, S
As a result, the liquid level is stably detected.

[0017]

FIG. 1 shows a first embodiment of the present invention.
7 will be described with reference to FIG. This embodiment is for detecting the liquid level in the transparent pipe A made of acrylic. The base end of the transparent pipe A is connected to the bottom of the tank, and the tip end extends vertically upward. The liquid level in the transparent pipe A is at the same level as in the tank.

First, in FIG. 4, a holder 11 is composed of an upper holder 12 made of synthetic resin and a lower holder 1 made of synthetic resin.
The upper holder 12 and the lower holder 13 are provided with a band head 14. Each of these band heads 14 can be moved in the directions of arrows A and A shown in FIG. 3, and each band head 14 has a hole 14a (only one hole 14a is shown). . A binding band 15 is inserted into each of the holes 14a.

As shown in FIG. 5, the upper holder 12 and the lower holder 13 are provided with support heads 16 located at the ends on the transparent pipe A side. As shown in FIG.
(Only one recess 16a is shown).
Further, as shown in FIG.
7 is rotatably mounted, and when the lever 17 is rotated, both band heads 14 move integrally in the direction opposite to the arrow A.

Therefore, when each binding band 15 is tightened on the outer peripheral surface of the transparent pipe A, both ends of each concave portion 16a are held in line contact with the outer peripheral surface of the transparent pipe A, and the holder 11 is attached to the transparent pipe A. Stablely attached. FIG.
When the lever 17 is rotated from the state shown in FIG. 2, the band heads 14 move in the direction indicated by the arrow A, and the binding bands 15 are loosened, so that the position of the holder 11 can be changed in the vertical direction along the transparent pipe A. .

The curvature of each concave portion 16a is set so as to correspond to the transparent pipe A having the smallest outer diameter of the plurality of types. Therefore, the holder 11 is attached to the transparent pipe A.
Is attached, the entire inner surface of each recess 16a is transparent pipe A
Contacts the outer peripheral surface of. Further, the support portions 18a and 18b in FIG. 1 refer to both end portions (contact portions with the transparent pipe A) of each concave portion 16a.

As shown in FIG. 2, an optical fiber 19a and a light projecting lens 19b corresponding to a light projecting means are accommodated in the right side of the holder 11. When the light emitting element (not shown) emits light, the light emitting lens 19b or Stanislaus Lo Kuang is projected through an optical fiber 19a, in FIG. 1 (a) and (b) as indicated by the broken line beta, transparent pipe A Shaft core
Of the line parallel to the line, located on the inner peripheral surface of transparent pipe A
In addition , light is applied to a predetermined portion, which is located near one of the support portions 18b .

Incidentally, as shown in FIG. 1A, the light projecting lens 19b is provided with respect to the transparent pipe A having the smallest outer diameter.
A form in which the hollow part is cut as thinly as possible (width dimension W
Is projected as small as possible). 2 and FIG. 7 indicates an allowable area of a light projection point by the light projection lens 19b.

As shown in FIG. 2, an optical fiber 20a and a light receiving lens 20b corresponding to a light receiving means are accommodated on the left side of the holder 11, and the light reflected by the inner peripheral surface of the transparent pipe A is Light is condensed by the light receiving lens 20b and is passed through the optical fiber 20a.
Light is incident on. A liquid level detection circuit (not shown) is connected to the light receiving element, and the liquid level detection circuit compares the amount of light received by the light receiving element with a reference value to determine a predetermined height in the transparent pipe A. Then, it is determined whether or not there is a liquid level. still,
The two-dot chain lines α1 and α2 in FIG. 1 define the light receiving area of the light receiving lens 20b.

In the holder 11, as shown in FIG.
A light-shielding plate 21 corresponding to the support is provided. The light shielding plate portion 21 is formed integrally with the upper holder 12, and has a base portion 21a having a rectangular plate shape and a head portion 21b having a triangular prism shape. And this light shielding plate part 2
The first head 21b cuts off the projection light reflected on the outer peripheral surface of the transparent pipe A, and therefore, along the line parallel to the axis of the transparent pipe A in the contact portion between the support 18b and the transparent pipe A. A predetermined portion is in contact with the outer peripheral surface of the transparent pipe A (that is, as shown in FIG. 4, it is located on a line connecting the upper support portion 18b and the lower support portion 18b).

Next, the operation of the above configuration will be described. In detecting the liquid level in the transparent pipe A, as shown in FIG. 3, each binding band 15 is tightened on the outer peripheral surface of the transparent pipe A, and the support portions 18a and 18
The holder 11 is mounted on the transparent pipe A in accordance with the contact of b with the outer peripheral surface of the transparent pipe A. When the light emitting element emits light in this state, as shown in FIG.
The light is projected on the inner peripheral surface of the transparent pipe A through b.

Here, when there is no liquid surface at a predetermined height in the transparent pipe A, the projected light is reflected on the inner peripheral surface of the transparent pipe A due to the difference between the refractive index of the transparent pipe A and the refractive index of air. The light is reflected and enters the light receiving element from the light receiving lens 20b through the optical fiber 20a. Therefore, since the amount of light received by the light receiving element exceeds a predetermined value, the liquid level detection circuit determines that there is no liquid. Also, when there is a liquid level at a predetermined height in the transparent pipe A,
Due to the closeness between the refractive index of the liquid and the refractive index of the transparent pipe A, the projected light travels substantially straight through the liquid through the inner peripheral surface of the transparent pipe A.
Therefore, since the amount of light received by the light receiving element falls below the predetermined value, the liquid level detection circuit determines that there is liquid.

According to the above embodiment, the axis of the transparent pipe A
Of the line parallel to the line, located on the inner peripheral surface of transparent pipe A
In addition , light was projected onto a predetermined portion of one of the support portions 18b . For this reason, as shown in FIG. 7, since the variation of the projection point due to the difference in the outer diameter of the transparent pipe A is reduced as much as possible, it is not necessary to enlarge the beam of light of the projection light and the light receiving area and enlarge the detection area. . Therefore, malfunction of the apparatus due to the reflected light from the bubbles is minimized for the transparent pipe A having various outer diameters.

In addition, regardless of whether the holder 11 is mounted on the transparent pipe A having a small diameter or the transparent pipe A having a large diameter, the contact portion between the support portion 18b and the transparent pipe A is located at a position relative to the axis of the transparent pipe A. In a predetermined portion along the parallel line, the distal end of the light shielding plate portion 21 substantially contacts the outer peripheral surface of the transparent pipe A. For this reason, the projection light reflected on the outer peripheral surface of the transparent pipe A does not enter the light receiving lens 20b.
The ratio of the difference in the amount of light received due to the presence or absence of the liquid to the amount of light received by the light receiving element increases. Therefore, the S / N ratio increases, and as a result, the liquid level is stably detected.

In order to prevent the light reflected on the outer peripheral surface of the transparent pipe A from entering the light receiving lens 20b, it is not necessary to move the light shielding plate 21 according to the outer diameter of the transparent pipe A. In addition, complication of the configuration is prevented, and as a result, cost increase is suppressed.

In order to prevent light reflected on the outer peripheral surface of the transparent pipe A from entering the light receiving lens 20b,
There is no need to bring the light projecting lens 19b closer to the transparent pipe A. For this reason, as shown in FIG. 1A, light can be projected in a form in which the width W is as small as possible with respect to the transparent pipe A having the smallest outer diameter, and as shown in FIG. In addition, the occupancy of the detection area is reduced for the large-diameter transparent pipe A, similarly to the small-diameter transparent pipe A. Therefore, from this point as well, malfunction of the apparatus due to bubbles is prevented as much as possible.

By the way, the thickness of the transparent pipe A generally becomes smaller as the outer diameter becomes smaller. On the other hand, in the related art, the light projecting direction is set so that the occupation ratio of the detection area to the transparent pipe A having the largest outer diameter is as small as possible. For this reason, when the holder is attached to the small-diameter transparent pipe A, the transparent pipe A tends to be further occupied by the thin area of the transparent pipe A, and the occupation ratio of the detection area is further increased.

In this respect, in this embodiment, as described above, light can be projected in such a form that the width W is as small as possible with respect to the transparent pipe A having the smallest outer diameter.
When the diameter of is small, the occupancy of the detection area can be minimized. Therefore, as shown in (b), the occupation ratio of the detection area is reduced for the large-diameter transparent pipe A as in the case of the small-diameter transparent pipe A, so that the malfunction of the apparatus due to bubbles is generally effective. Is significantly reduced.

In detecting the liquid level in the transparent pipe A, a fiber-type photoelectric sensor configured to project light by the optical fiber 19a and receive reflected light by the optical fiber 20a is used. There is no need to incorporate an optical element, a light receiving element, a liquid level detection circuit, and the like. For this reason, since the device is downsized, the device can be mounted even in a small space.

Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. Each of the upper holder 12 and the lower holder 13 is provided with two support heads 22.
A recess is formed in each support head 22, and
With the support portions 18a and 18b corresponding to the ends of the concave portions contacting the outer peripheral surface of the transparent pipe A, the holder 1
1 is stably mounted on the transparent pipe A.

Next, a third embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. A concave portion is formed in each support head 16, and the support portion 1 corresponding to one end of the upper concave portion is formed.
8a and a supporting portion 18b corresponding to the other end of the lower concave portion
Comes into contact with the outer peripheral surface of the transparent pipe A, so that the holder 11 is stably mounted on the transparent pipe A.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. A concave portion is formed in the lower support head 16, and the support portions 18a and 18b of the upper concave portion 16 and the support portion 1 corresponding to one end of the lower concave portion.
8b comes into contact with the outer peripheral surface of the transparent pipe A,
The holder 11 is stably mounted on the transparent pipe A.

In the first to fourth embodiments, the transparent pipe A of the lines parallel to the axis of the transparent pipe A is
A is located on the inner peripheral surface of A and near the support portion 18b
The light was projected on a predetermined portion of the transparent pipe A, but the invention is not limited to this .
Of these, it is located on the inner peripheral surface of the transparent pipe A and
The light may be projected onto a predetermined portion that is located in the vicinity .
Reference symbol α ′ in FIG. 2 indicates an allowable area of the light projection point.

In the first to fourth embodiments,
Although the light-shielding plate 21 is formed integrally with the upper holder 12, the present invention is not limited to this. For example, the light-shielding plate 21 may be formed integrally with the lower holder 13, or may be formed of the upper holder 12 and the lower holder 13.
Or the separate light-shielding plate portion 21 is attached to the holder 11.
It may be housed inside.

In the first to fourth embodiments,
Although the light-shielding plate portion 21 is constituted by the base portion 21a having a rectangular plate shape and the head portion 21b having a triangular prism shape, the present invention is not limited to this. For example, the light-shielding plate portion 21 may have a triangular cross section.

In the first to fourth embodiments,
Although a fiber type photoelectric sensor was used, the invention is not limited to this. For example, an amplifier separated type in which a light emitting and receiving element is directly arranged behind the light emitting lens 19b and the light receiving lens 20b, or a built-in amplifier type May be used.

In the first to fourth embodiments,
When attaching the holder 11 to the transparent pipe A, the fixed type binding band 15 was used. However, the present invention is not limited to this. For example, a variable type binding band may be used,
A screw-type fixing bracket or the like may be used.

In the first to fourth embodiments,
Holder 11 on transparent pipe A projecting vertically from tank
Is mounted, but the present invention is not limited to this. For example, it may be mounted on a transparent pipe A projecting obliquely upward.

In the first to fourth embodiments,
In FIG. 1, the arrangement of the light projecting means and the light receiving means is reversed, or the light projecting means and the light receiving means are arranged above and below the plane of the paper, or diagonally above and below the plane of the paper. May be. In short, the transparent pipe A of the lines parallel to the axis of the transparent pipe A
And near the support portion 18a or 18b.
However, the light projecting means may be arranged so as to project light to a predetermined portion, but the light receiving means may be arranged so as to receive the light projected from the light projecting means and reflected by the inner peripheral surface of the transparent pipe A. .

[0045]

As is apparent from the above description, the liquid level detecting device of the present invention has the following effects. According to the first aspect of the present invention, the variation of the projection point due to the difference in the outer diameter of the transparent pipe is reduced as much as possible. For this reason, it is not necessary to enlarge the detection area, so that the apparatus is prevented from malfunctioning due to the influence of bubbles on transparent pipes having various outer diameters.

According to the second aspect, the light reflected on the outer peripheral surface of the transparent pipe does not enter the light receiving means, and the difference in the amount of light received by the presence or absence of the liquid occupies the amount of light received by the light receiving means. Since the ratio increases, the liquid level is stably detected. In order to prevent the light reflected on the outer peripheral surface of the transparent pipe from entering the light receiving means, first, it is not necessary to move the light shielding means according to the outer diameter of the transparent pipe. For this reason, the configuration is prevented from becoming complicated, thereby suppressing an increase in cost. Secondly, since it is not necessary to bring the light projecting means close to the transparent pipe, the light projecting direction can be set based on the transparent pipe having the smallest outer diameter. For this reason, since the ratio of the detection area occupying the hollow portion of the transparent pipe is reduced, malfunction of the device due to bubbles is also prevented from this point.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention (a diagram showing the principle of liquid level detection).

FIG. 2 is a cross-sectional view of the holder.

FIG. 3 is a perspective view showing a state where a holder is mounted on a transparent pipe.

FIG. 4 is a front view of the holder.

FIG. 5 is a side view of the holder.

FIG. 6 is a top view of the holder.

FIG. 7 is a diagram showing a variation state of a light emitting point.

FIG. 8 is a view showing a second embodiment of the present invention (a front view schematically showing a holder).

FIG. 9 is a view corresponding to FIG. 8, showing a third embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 9 showing a fourth embodiment of the present invention;

FIG. 11 is a diagram schematically showing a conventional liquid level detection device.

FIG. 12 is a diagram corresponding to FIG. 7;

FIG. 13 is a diagram corresponding to FIG. 1;

[Explanation of symbols]

A is a transparent pipe, 11 is a holder, 18a and 18b
Denotes a supporting part, 19b denotes a light projecting lens (light emitting means), 20b denotes a light receiving lens (light receiving means), and 21 denotes a light shielding plate part (supporting part).

Claims (2)

(57) [Claims] 1. A holder, a pair of support portions provided on the holder and in contact with an outer peripheral surface of a transparent pipe having a circular cross section, a light projecting means provided on the holder, and a light source provided on the holder. and a light receiving means is, the light projecting means is parallel to the axial line of the transparent pipe
Line located on the inner peripheral surface of the transparent pipe and
Light is projected on a predetermined part of the object located near the support
In addition, there is no liquid level at a predetermined portion in the transparent pipe.
In the case where the projection light is reflected on the inner peripheral surface of the transparent pipe and
When there is a liquid level in a predetermined part of the transparent pipe,
Through the inner peripheral surface of the transparent pipe so as to travel substantially straight in the liquid
And the light- receiving means reflects the light reflected on the inner peripheral surface of the transparent pipe.
A liquid level detecting device, which is arranged to receive light . 2. The light projecting means projects light in the vicinity of one support portion of the inner peripheral surface of the transparent pipe, and the one support portion projects the light of the transparent pipe out of the light projected from the light projecting means. 2. A liquid level detecting device according to claim 1, wherein said liquid level detecting device is provided between said light projecting means and said light receiving means so as to prevent the light reflected on the outer peripheral surface from entering said light receiving means. apparatus.