JPH0538604U - Sensor - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a sensor in which the head (2a) of the sensor body (2) is securely placed in contact with the closed end (1a) of the fluororesin tube (1). To aim. [Structure] Inside the tube (1) made of fluorocarbon resin, one end of which is closed by heat processing, the sensor body (2) is provided with the head (2a) at the tip of the optical fiber (2b). Insert it so that the tip hits the closed end (1a) of the tube (1). A spiral or tubular repulsive body (4) is inserted from the rear of the head (2a) in the tube (1), and further a short thermally expandable tube (3a) made of a fluororesin is inserted from the rear. By thermally expanding the heat-expandable tube (3a) to form the expansion tube (3), the expansion tube (3) is closely fixed to the inner wall of the tube (1). This makes the repulsive body
A sensor having a structure in which (4) is interposed in a compressed state between the head (2a) and the expansion tube (3) is obtained.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a sensor using an optical fiber, particularly to an optical fiber type photoelectric switch.

[0002]

[Prior Art]

 The sensor body (2), which has the head (2a) at the tip of the optical fiber (2b), is inserted into the fluororesin tube (1) with the tip closed. Is used as. Since the fluororesin tube (1) has chemical resistance, oil resistance, non-adhesiveness, and heat resistance, the sensor body (2) can be protected.

In this case, if a gap is formed between the head (2a) of the inserted sensor body (2) and the closed end of the tube (1), the sensor may malfunction. Therefore, measures have been taken to eliminate the gap.

One of the methods that has been conventionally adopted as such a device is, as shown in FIG. 3, a fluorine resin having a diameter larger than that of the tube (1) at the tip of the tube (1) made of a fluororesin. A short tube (1 ') made of a system resin is fusion-bonded to form a structure with a step (d) .The optical fiber (2b) side of the sensor body (2) is inserted from the tip side of the bonding tube and the head ( Position the rear end of 2a) at the step (d), and then close the front end of the joined short tube (1 ') by thermal processing so that no gap is created between the end of the head (2a). Is the way to do it.

Another method that has been conventionally adopted is, as shown in FIG. 4, that one end side of a tube (1) made of a fluororesin is heated with a jig until the head (2a) is inserted. After forming the step (d) by deforming to the large diameter of the head, insert the optical fiber (2b) side of the sensor body (2) from the large diameter part (1 ") side and rear end of the head (2a). Is located at the step (d) and then the tip of the large diameter portion (1 ") is closed by thermal processing so that no gap is created between the tip of the head (2a).

As shown in the reference example in FIG. 5, the applicant of the present invention puts a head at the tip of an optical fiber (2b) inside a tube (1) made of a fluorine resin whose one end is closed by heat processing. Insert the sensor body (2) equipped with (2a) until the tip of its head (2a) hits the closed end (1a) of the tube (1), and place it behind the head (2a) inside the tube (1). The short expansion tube (3a) made of fluorocarbon resin is inserted, and then the expansion tube (3) that is closely fixed to the inner wall of the tube (1) by thermal expansion is placed. Recently, a sensor having a structure in which 2a) is sandwiched between the closed end (1a) of the tube (1) and the expansion tube (3) has been developed.

[0007]

[Problems to be solved by the device]

 The above-mentioned two conventional methods are as follows: the tube (1) is fusion-bonded with a short tube (1 ') having a large diameter, or one end of the tube (1) is deformed to have a large diameter, and then the sensor main body is deformed. (2) is inserted into the tube (1) and then the joined short tube (1 ') or large diameter part (1 ") is closed by thermal processing until the tip side contacts the head (2a). Therefore, the operation of inserting the long optical fiber (2b) is troublesome, the fusion splicing operation and the operation of deforming to a large diameter require skill and labor, and the head (2a) may be damaged during thermal processing. There are problems such as being there.

Further, in the sensor developed by the applicant of the present invention, even if the heat-expandable tube (3a) is inserted until it comes into contact with the rear end of the head (2a), the heat-expandable tube (3a) is subjected to the heat-expanding operation. Although it sometimes expands in the radial direction, it contracts slightly in the length direction due to stress return, so there is a limit that it is not possible to completely prevent the formation of a slight gap between the head (2a) and the expansion tube (3). is there.

Under such a background, the present invention provides a sensor in which the head (2a) of the sensor body (2) is disposed so as to surely come into contact with the closed end (1a) of the fluororesin tube (1). It is intended to provide.

[0010]

[Means for Solving the Problems]

 The sensor of the present invention has a sensor body (2) having a head (2a) at the tip of an optical fiber (2b) inside a tube (1) made of a fluororesin whose one end is closed by heat processing. Insert the head (2a) so that the tip of the head (2a) hits the closed end (1a) of the tube (1). 3a) is inserted and then thermally expanded to place the expansion tube (3) in close contact with the inner wall of the tube (1), and the spiral or tubular repulsion body (4) is replaced by the head (2a)- It has a structure in which it is interposed between the expansion tubes (3) in a compressed state.

The present invention will be described in detail below.

The sensor body (2) has a structure in which the head (2a) is provided at the tip of the optical fiber (2b). The tip of the optical fiber (2b) is exposed through the head (2a), and the light incident from the tip is sent to the other end through the inside of the optical fiber (2b).

The fluororesin tube (1) includes a fluorocarbon resin having high transparency, such as perfluoroalkoxy-substituted polytetrafluoroethylene (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). A small-diameter tube obtained by molding is used.

One end of this tube (1) is previously closed by thermal processing. That is, insert a rod-shaped jig into the tube (1), heat the tip side of the tube (1) to a temperature equal to or higher than the melting point to soften it, and press it from the outside with the jig to remove the tube (1). The tip side is deformed to form the closed end (1a). The closed end (1a) is often flat, but it may also be conical.

Then, the sensor body (2) is inserted from the open end into the inside of the fluororesin tube (1) whose one end is closed as described above, and the tip of the head (2a) of the tube (1) is Try to hit the closed end (1a).

Next, insert a spiral or tubular repulsion body (4) such as a metal or plastic coil spring or a cylindrical elastic body into the tube (1), and Insert the short heat-expandable tube (3a) made of resin.

Here, the thermally expandable tube (3a) is a tube made of a fluororesin having an outer diameter larger than the inner diameter of the tube (1) and is subjected to stress strain by stretching at a temperature. When heated, it expands to near the original diameter due to stress return.

Insert such a heat-expandable tube (3a) into the inside from the open end of the tube (1) until the repulsion body (4) is compressed from behind the repulsion body (4) inserted previously. When heated while being pressed by a jig, the thermally expandable tube (3a) thermally expands in the radial direction to form an expanded tube (3), which is tightly fixed to the inner wall of the tube (1). At that time, the heat-expandable tube (3a) is slightly shrunk in the lengthwise direction, and the repulsive member (4) compressed by the shrinkage extends. That is, in the tube (1), the repulsive body (4) is interposed between the head (2a) and the expansion tube (3) in a compressed state.

The sensor of the present invention having the above structure is particularly useful as an optical fiber type photoelectric switch, and can be used as various sensors using an optical fiber.

[0020]

[Action]

 In the sensor of the present invention, the head (2a) of the sensor body (2) is inserted into the inside of the tube (1) whose one end is the closed end (1a), from the side closer to the closed end (1a). The repulsive body (4) in the compressed state and the expansion tube (3) closely fixed to the inner wall of the tube (1) are arranged. The optical fiber (2b) of the sensor body (2) extends through the repulsive body (4) and the hollow portion of the expansion tube (3) and beyond the opening of the tube (1).

With such a structure, the head (2a) of the sensor body (2) is always supported by the urging force of the repulsion body (4) which is supported by the front end of the expansion tube (3). It is pressed against the closed end (1a) of 1) so that the head (2a) does not rattle in the tube (1).

[0022]

【Example】

 Next, the present invention will be further described with reference to examples.

Embodiment 1 FIG. 1 is a sectional view showing an example of the sensor of the present invention. FIG. 2 is an explanatory view showing the manufacturing process.

(1) is a tube made of perfluoroalkoxy-substituted polytetrafluoroethylene (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP), one end of which is closed by heat processing.

Reference numeral (2) is a sensor body, which has a structure in which the head (2a) is provided at the tip of the optical fiber (2b). The tip of the optical fiber (2b) penetrates the head (2a) and is exposed at its front end.

(3) is an expansion tube formed by thermal expansion of a thermally expandable tube (3a) made of perfluoroalkoxy-substituted polytetrafluoroethylene (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) , Tightly fixed to the inner wall of the tube (1).

(4) is a repulsive body and is composed of, for example, a coil spring made of metal or plastics.

As shown in FIG. 2 (a), a tube (1) is prepared, and a jig is pressed from inside and outside of the tube (1) while heating the tip side of the tube (1) to a temperature equal to or higher than the melting point. Thus, the tip side of the tube (1) was deformed to form a flat closed end (1a).

First, the sensor body (2) is inserted into the tube (1) from its head (2 a) side as shown in FIG. 2C, and then the repulsive body is inserted as shown in FIG. 2D. (4) was inserted, and the heat-expandable tube (3a) was further inserted from the back as shown in FIG. 2 (e).

A head (2a) inserted into the tube (1) by inserting a jig from the open end of the tube (1) and pressing the rear end of the thermally expandable tube (3a) toward the front / Repulsive body (4) / Thermally expandable tube (3a) from the outside of the tube (1) while pressing the three members toward the closed end (1a) until the repulsive body (4) is compressed. When the vicinity of the tube (3a) was heated to about 100 ° C, the heat-expandable tube (3a) thermally expanded at that position to become the expansion tube (3) as shown in Fig. 2 (f), and the inner wall of the tube (1) Fixed in close contact with.

As a result, the intended sensor was obtained. The head (2a) of the sensor body (2) is constantly pressed against the closed end (1a) of the tube (1) by the urging force of the repulsive body (4), causing rattling in the tube (1). Never happened.

[0032]

[Effect of the device]

 In the sensor of the present invention, since the head (2a) of the sensor body (2) inside the tube (1) is always pressed against the closed end (1a) of the tube (1) with moderate force, It does not cause rattling and is excellent in terms of sensor reliability and life. It is also preferable because it is easy to manufacture.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a sensor of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of the sensor of FIG.

FIG. 3 is an explanatory view showing an example of a manufacturing process of a conventional sensor.

FIG. 4 is an explanatory diagram showing another example of a conventional sensor manufacturing process.

FIG. 5 is an explanatory diagram showing a manufacturing process of a sensor as a reference example developed by the present applicant.

[Explanation of symbols]

(1) ... Tube, (1a) ... Closed end, (1 ') ... Short tube with large diameter, (1 ") ... Large diameter part, (2) ... Sensor body, (2a) ... Head, (2b) ... Optical fiber, (3) ... expansion tube, (3a) ... thermally expandable tube, (4) ... repulsive body, (d) ... step

Claims (2)

[Scope of utility model registration request] 1. A sensor body (2) having a head (2a) at the tip of an optical fiber (2b) inside a tube (1) made of a fluororesin whose one end is closed by heat processing. 2a) Insert the tube so that its tip hits the closed end (1a) of the tube (1), and place a short thermally expandable tube (3a) made of fluororesin behind the head (2a) inside the tube (1). Place the expansion tube (3) that is tightly fixed to the inner wall of the tube (1) by inserting it and then thermally expanding it. ) A sensor having a structure interposed in a compressed state therebetween. 2. An optical fiber type photoelectric switch.
The described sensor.