JP3055982B2 - Detection probe structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection probe structure in which various detection units such as a proximity switch, an optical sensor, an image sensor, and a temperature sensor are provided at the end of a sensor cable, and the end is housed in a protective tube. It is about.

[0002]

2. Description of the Related Art For example, in order to detect an object in a chemical tank by a proximity switch, when a detection unit having a built-in proximity switch and a lead such as an electric wire led from the detection unit are arranged in the liquid, Is housed in a protective tube to protect it from damage caused by a chemical solution.

FIG. 7 shows a conventional method for accommodating and fixing a sensor cable (8) in a protective tube (9). The protection tube (9) is made of fluororesin, and has a large-diameter enlarged portion (91) and a small-diameter tube portion (92) corresponding to the outer diameter of the detection portion (80) and the lead portion (81) of the sensor cable (8). ), The sensor cable (8) is inserted through the opening of the large-diameter enlarged section (91), and the detection section (80) is accommodated in the large-diameter enlarged section (91) as shown in the drawing. 250 against the opening edge of the large diameter enlarged section (91)
A heat welding process is performed at a temperature exceeding ℃, and the end of the protective tube is sealed as shown by a chain line in the figure.

As a result, in the sensor cable (8), the step from the large-diameter enlarged portion (91) to the small-diameter tube portion (92) of the protective tube (9) serves as a stopper, and is prevented from being removed. The sensor cable (8) is accommodated and fixed in (9).

[0005]

However, in the above-mentioned detection probe structure, not only a special worker is required for the heat welding operation of the protective tube, but also the work site and the heat welding site become hot, so that the workability and safety can be improved. There was a problem that required special consideration for sex. Also, fluorine gas is generated by heating,
There were problems harming the environment. Further, since a material having a special heat resistance needs to be used for the detection unit, and the heating time is greatly limited, a rapid heat welding operation by a skilled worker is indispensable.

Therefore, instead of using heat welding, a sensor cable is inserted into the protective tube using a fluororesin protective tube whose tip is sealed in advance, and both are fixed with an epoxy-based adhesive or the like. A method is conceivable.

However, in this method, it is indispensable to provide an adhesive property to the inner surface of the protective tube by using a surface treatment agent. For this reason, a harmful gas is generated at the surface treatment stage, or a transparent material is formed. There was a problem that the protective tube turned brown. Also, the adhesive strength was insufficient.

[0008] It is an object of the present invention to provide a detection probe structure that can securely fix a sensor cable in a protective tube in a simple and safe manner.

[0009]

According to the detection probe structure of the present invention, a distal end portion of a sensor cable (1) provided with a detection portion (10) is provided in a protective tube (2) having a distal end portion sealed. Is housed. Protection tube (2) and sensor cable
In the annular space between (1), a shape memory resin tube (3) that has been expanded or reduced in the radial direction by heat treatment is disposed, and the shape memory resin tube is either a protective tube or a sensor cable due to the deformation. Crimp to one side,
A stopper for the other is formed.

[0010]

When constructing the detection probe structure according to the present invention, a protection tube (2) whose tip is sealed in advance is prepared, and the end of the sensor cable (1) near the detection section (10) is prepared. A shape memory resin tube (3) having a diameter slightly smaller than the inner diameter of the protective tube (2) is fitted to the sensor cable.
(1) Protective tube with shape memory resin tube (3)
(2) Insert into.

Then, the detection unit (1) of the sensor cable (1)
0) reaches the distal end (21) of the protective tube (2), the shape memory resin tube (3) is subjected to a heat treatment at a relatively low temperature of, for example, about 100 ° C. The tube (3) is expanded and its outer peripheral surface is crimped to the inner peripheral surface of the protective tube (2) or contracted and its inner peripheral surface is crimped to the outer peripheral surface of the sensor cable (1) according to its characteristics.

As a result, one of the sensor cable (1) and the protective tube (2) has a shape memory resin tube.
(3) is fixed, and the shape memory resin tube (3) forms a stopper for the other.

[0013]

In the detection probe structure according to the present invention, heat treatment for enlarging or reducing the shape memory resin tube is necessary.
The operation is safe and easy because it is relatively low around ℃.
In addition, no harmful gas is generated from the protective tube or the like by heating.

Since the shape memory resin tube has a large deformation as a characteristic of the shape memory resin, the shape memory resin tube is firmly pressed against the sensor cable (1) or the protection tube (2), and the shape memory resin tube is pressed. By the stopper function of the resin tube, the sensor cable can be securely fixed in the protective tube.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be specifically described below with reference to the drawings. The embodiment of FIG.
A sensor cable (1) having a detecting portion (10) having a diameter larger than that of the lead portion (11) is housed in a fluororesin protective tube (2) in which (21) is sealed. The shape memory resin tube (3) crimped and fixed to the inner peripheral surface of (1) forms a stopper for the detecting portion (10) of the sensor cable (1).

As a material for the shape memory resin tube (3), for example, PFA or the like which is a fluororesin can be used. In this case, the shape memory resin tube (3) is stored by heating at about 100 ° C. It is possible to return to the original shape and dimensions.

FIG. 2 shows a process in which the shape memory resin tube (3) is enlarged by heating, and the outer peripheral surface thereof is pressed against the inner peripheral surface of the protective tube (2). At this time, as a general characteristic of the shape memory resin, it is possible to obtain a large deformation by a slight heating as compared with a normal thermal deformation, whereby the outer peripheral surface of the shape memory resin tube (3) is protected by a protective tube.
(2) Press firmly on the inner peripheral surface.

The embodiment of FIG. 1 uses a sensor cable.
The expanded shape of the detection part (10) of (1) is
(3) The sensor is used as a contact part against the stopper. However, many sensors such as photoelectric switches have built-in electronic components, and the detection part (10) has a larger diameter than the lead part (11). Therefore, most of the sensor cables (1) having various detecting portions (10) can adopt the simple retaining structure shown in FIG.

When the sensor cable (1) does not have an enlarged end shape as shown in FIG. 3, a shape memory resin tube which contracts by heating is attached to the end of the sensor cable (1).
(31) may be fitted to form a contact portion for the shape memory resin tube (3).

FIG. 4 shows the structure of a detection probe used in a liquid level meter. The sensor cable (1) is composed of a light emitting optical fiber (12) and a light receiving optical fiber (13), and a holding tube for holding the two optical fibers at a fixed interval and posture is provided at the tip of the sensor cable (1). (5) is fixed in advance by an adhesive (51), and the holding tube (5) serves as the detection unit (10) in FIG. 1 to constitute a similar retaining structure using the shape memory resin tube (3). Have been.

At the tip of the protective tube (2), a conical prism (4) is integrally formed, and in the air, the light emitted from the light projecting optical fiber (12) is condensed. The light is reflected as indicated by a dashed line in (4) and enters the light receiving optical fiber (13). On the other hand, in the liquid, most of the light emitted from the light projecting optical fiber (12) passes through the reflecting surface of the conical prism portion (4), and the amount of light received by the light receiving optical fiber (13) is large. To decline.

Therefore, by detecting a change in the amount of light from the light receiving optical fiber (13), it can be determined whether the detection probe is in the air or submerged in the liquid.

FIG. 5 shows the results obtained by using the two detection probes described above.
An example is shown in which a liquid level meter of a tank (7) containing a chemical solution is configured. The first sensor cable (1a) is arranged with the conical prism portion (4a) set at the high-level detection position L _H , and the second sensor cable (1b) is configured to detect the conical prism portion (4b) at a low level. It has been arranged to set the position L _L, emitter and receiver (6) is connected to both the sensor cable.

When the liquid level rises above the prism portion (4a) of the first sensor cable (1a), the light receiving amounts of both sensor cables (1a) and (1b) are small. In contrast,
The liquid level is the prism part (4b) of the second sensor cable (1b).
If it drops below that point, both sensor cables (1
a) The amount of received light in (1b) increases. If the liquid surface is present between the high level detected position L _H and the low level detection position L _L is the amount of light received first sensor cable (1a) Many, second
The amount of light received by the sensor cable (1b) is reduced.

Therefore, the change of the liquid level is detected by supplying the light amount signal photoelectrically converted by the light emitting and receiving device (6) to the detection circuit (61) and judging the change of the light amount. You can do it.

In the detection probe, as shown in FIG. 6, the optical axes of the light projecting optical fiber (12) and the light receiving optical fiber (13) constituting the detecting section have an opening angle mutually, and The inclination angle α of the optical axis of the section is set to 70 degrees. The outer diameter of the protective tube 2 is 6 mm, the height H of the conical prism portion 4 is 7 mm, and the vertex angle θ is approximately 50 degrees. In this case, the light emission angle β from the optical fiber to the prism portion becomes 55 degrees due to refraction.

Therefore, spots to be projected and received by the two optical fibers (12) and (13) in the horizontal plane in contact with the apex of the conical prism portion (4) (regions S ₁ and S ₂ shown by two-dot chain lines in FIG. 6).
Will not overlap each other and will be spaced apart.

The reason why the apex angle of the conical prism portion (4) is formed smaller than 90 degrees as described above is as follows. That is, placed allowed drop second sensor cable shown in FIG. 5 (1b) to a position impinging on the bottom of the tank (7), if you set the low-level detection position L _L in the tank near the bottom, the tank (7) in in a state where the liquid surface of the is higher than the low level detection position L _L, the light receiving amount of the sensor cable (1b) should be less.

However, when the vertex angle is 90 degrees, that is,
When the optical axes of the light projecting optical fiber (12) and the light receiving optical fiber (13) are parallel to each other, the aforementioned light projecting and light receiving target spots overlap each other.

As a result, the light emitted from the light emitting optical fiber (12) of the detection probe installed at the bottom of the tank (7) is reflected at the tank bottom, and the reflected light is transmitted to the light receiving optical fiber (13). Incident, and the detection probe is mistaken for being exposed to the air.

On the other hand, as shown in FIG.
In the detection probe in which the vertex angle of (4) is formed to be smaller than 90 degrees and the optical fibers (12) and (13) are provided with a fixed opening angle, the above-mentioned light projecting and receiving spots are separated from each other. Therefore, the light reflected on the bottom surface of the tank (7) does not enter the light receiving optical fiber (13), and malfunction is prevented.

Further, since the apex angle of the conical prism portion (4) is formed to be smaller than 90 degrees, when the conical prism portion (4) is exposed from the liquid to the air, the conical prism portion (4) does not move. The liquid adhering to the surface flows down along the steep slope of the conical surface, and only adheres to the apex of the conical prism portion (4) as a small water droplet. Therefore, there is no possibility that the above-mentioned water droplet may cause a malfunction of the detection probe.

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the appended claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a detection probe structure according to the present invention.

FIG. 2 is a diagram illustrating deformation of a shape memory resin tube due to heat treatment.

FIG. 3 is a sectional view showing another embodiment of the detection probe structure according to the present invention.

FIG. 4 is a cross-sectional view showing an example in which the detection probe structure according to the present invention is applied to a sensor for detecting a liquid level.

5 is a diagram showing a schematic configuration of a liquid level meter using the sensor of FIG. 4;

FIG. 6 is a view for explaining the detailed shape and dimensions of a conical prism portion of the sensor of FIG. 4;

FIG. 7 is a cross-sectional view illustrating a method for fixing a sensor cable in a conventional detection probe structure.

[Explanation of symbols]

 (1) Sensor cable (10) Detector (11) Lead (2) Protective tube (3) Shape memory resin tube

Claims (1)

(57) [Claims] 1. A protective tube having a sealed distal end,
In the detection probe structure containing the distal end of the sensor cable provided with the detection unit, the annular space between the protective tube (2) and the sensor cable (1) is expanded or reduced in the radial direction by heat treatment. A shape memory resin tube (3) is disposed, and the shape memory resin tube is provided with a protective tube (2) or a sensor cable due to the deformation.
(1) A detection probe structure characterized by being pressure-bonded to one of them and forming a stopper for the other.