JP3297074B2 - How to seal the tip of the member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for securely and easily sealing the tip of a member with a thermoplastic resin.

2. Description of the Related Art In some cases, a tip portion of a member needs to be sealed with a resin for various purposes. 2. Description of the Related Art Conventionally, for example, the following method is known as a method of sealing a distal end portion of a member covered with a thermoplastic resin. (A) A method in which the member is covered with a tube so that the end of the thermoplastic resin tube is slightly longer than the end of the member, and the end of the tube is melted by heat to seal the end of the member. (B) A method in which a molten resin is added to and covered (integrated with the tube) on the distal end surface of a member covered with a thermoplastic resin tube, and the distal end portion of the member is sealed. (C) The detection element attached to the end of the thermoplastic resin-coated cable is housed in a case with a lid made of thermoplastic resin,
A method in which the joining surfaces are welded to seal the detection element at the tip (see Japanese Utility Model Laid-Open No. 1-170929).

However, in the conventional sealing methods (a) to (c), air is often contained between the member and the resin coating at the sealing tip portion. . In the case where the member is easily deformed or deteriorated by heat, the member is directly affected by the heat in the conventional method. Further, in particular, in the methods (a) and (b), since the resin is once dissolved,
For example, when sealing is performed using a transparent resin that is easily crystallized, the degree of crystallinity changes depending on the cooling rate, and transparency may be lost. In particular, when the above-mentioned conventional method is applied to, for example, sealing of an optical fiber sensor, if air is contained between the optical fiber sensor and the resin coating on the distal end surface, the refractive index of the optical fiber sensor changes and the loss of light quantity increases. Also, since the melting point of the fiber is often lower than the melting point of the thermoplastic resin,
The fiber is liable to cause obstacles such as deformation and deterioration due to heat. If the coating resin crystallizes and loses transparency, it will no longer function as an optical fiber sensor. The present invention
In order to solve the above-mentioned conventional problems, if the member has a specific function, for example, even in the case of a sensor, without impairing the function, the tip of the member having the tip surface can be securely and securely placed. It is an object to provide a method for easily sealing.

In order to achieve the above object, a sealing method according to the present invention comprises providing a coating of a thermoplastic resin on a surface other than a front end surface of a member, and then, A method of sealing a distal end portion of a member formed by fusing a thermoplastic resin plate having the same shape as the peripheral shape of the distal end portion and then cooling, wherein the fusion between the distal end portion of the coating and the resin plate is performed. Heating a heat block having a recess slightly larger than the tip of the coating, inserting a convex heat insulating spacer into the recess so that the convex surface faces outward, and then inserting the resin plate into the end. After melting, by inserting the tip of the member having the coating and pressing against the resin plate,
It is characterized by performing. The member to be sealed by the method of the present invention is an object such as a columnar body or a cylindrical body having a front end surface and other surfaces, and preferably has a flat front end surface or a gentle convex surface. Specifically, various types of sensors such as a transmission type or reflection type optical fiber sensor having the above-mentioned shape, a temperature sensor, and the like can be mentioned. It is preferable that the coating of the thermoplastic resin is provided on a surface other than the front end surface of the member so as to slightly protrude from the front end. As the thermoplastic resin in the present invention, any known thermoplastic resin such as a polyolefin resin can be used,
In terms of heat resistance, chemical resistance, transparency, etc., the melting point is 302.
A heat-fusible fluororesin such as a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA) at a temperature of ３１０310 ° C. and a copolymer of tetrafluoroethylene and hexafluoropropylene at a melting point of 253-282 ° C. preferable. The thermoplastic resin plate is a plate having the same shape as the peripheral shape of the distal end portion of the member having the resin coating and the same resin as the thermoplastic resin, and is preferably slightly larger than that. The convex heat insulating spacer is a heat insulating material made of stainless steel (SUS), aluminum, or the like having a convex surface and having a space in a portion surrounded by the convex surface, and transmitting heat from the bottom of the concave portion of the heat block. It is for preventing damage. The heat block has a convex heat insulating spacer, a thermoplastic resin plate, and a concave portion for accommodating the distal end of the member, and heats to a temperature higher than the melting point of the thermoplastic resin, preferably slightly higher.
The concave part of the heat block has such an extent that the tip part of the member can be inserted smoothly, can be fused to the resin plate, and the fused part can be rapidly cooled by blowing air to the gap between the tip part of the member and the inner wall of the concave part. It is of a size that is slightly larger than the tip of the member having the resin coating.

In the method of the present invention, the heat from the inner peripheral wall of the concave portion of the heat block is quickly transmitted since the convex heat insulating spacer is used, but air exists between the concave bottom and the convex surface. Since the thermal conductivity of air is low, the transfer of heat from the bottom of the recess is suppressed. Therefore, when the convex heat insulating spacer and then the resin plate are inserted into the concave portion, the outer peripheral end portion of the resin plate is heated first and then starts to melt. Next, when the tip of the member having the coating is inserted into the recess and pressed against the resin plate, the center of the resin plate is first pressed by the convex portion of the spacer, and then the resin plate is deformed along with the convex heat insulating spacer with the pressing. As a result, the air between the member and the tip of the member is reliably discharged, and the end of the member is fused with the coating tip of the member. In addition, since heat transfer from the bottom of the concave portion is suppressed, portions other than the end portion of the resin plate are not immediately melted, and the transparency is not impaired. In addition, the transfer of heat to the side of the member that does not want to transfer heat is also suppressed.
Obstacles such as deformation due to heat of a component material such as fiber coated with a resin having a much lower melting point can also be prevented. And, by cooling after fusion, before the central portion of the resin plate is melted, the end portion can be solidified, so that there is no problem in lifting the sealed member from the concave portion,
Therefore, a pinhole or the like does not occur on the tip surface of the coated resin.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a sealing method according to one embodiment of the present invention. FIG. 2 is a partial sectional view showing a transmission type optical fiber sensor according to an embodiment of the present invention before and after sealing. In this embodiment, first, the transmission type optical fiber sensor 1 shown in FIG.
Then, the PFA tube 2 was covered so as to cover the entire outer peripheral surface thereof, and the end of the PFA tube 2 was arranged so as to slightly protrude from the tip so as not to hinder fusion and discharge of air at that time. Separately, a convex heat insulating spacer 3 made of aluminum having an outer diameter and a convex surface substantially the same as the outer diameter of the tip of the PFA-coated optical fiber sensor, and having a space in a portion surrounded by the convex surface and the horizontal bottom surface. Was prepared. Further, a PFA plate 4 having an outer diameter substantially equal to the outer diameter of the tip of the PFA-coated optical fiber sensor was prepared. On the other hand, it has an opening and a bottom having an inner diameter slightly larger than the outer diameter of the PFA-coated optical fiber sensor, and has a convex heat insulating spacer 3, a PFA plate 4, and a concave portion 5 having a depth to accommodate the tip of the PFA-coated optical fiber sensor. The heat block 6 is subjected to PFA by the band heater 7.
(302-310 ° C.). As shown in FIG. 1, in the recess 5 of the heat block 6,
The convex heat insulating spacer 3 was inserted so that the convex surface was directed upward, and then the PFA plate 4 was immediately inserted. Immediately when the outer peripheral edge of the PFA plate 4 was melted, the tip of the PFA-coated optical fiber sensor was inserted into the recess 5 and pressed against the PFA plate 4. When the fused surfaces of both were completely melted, air was sent to the gap of the concave portion 5 to rapidly cool and solidify the fused portion. After the fused portion was completely solidified, the PFA-coated optical fiber sensor was pulled up, and the tip of the optical fiber sensor 1 was completely sealed as shown in FIG. This PFA
The optical fiber sensor 1 whose tip is sealed by
There was no air pocket between the coating surface and the tip, and the coating was transparent and no pinhole was generated. The coated tip portion sealed in this way can be cut or polished as required to produce a product. FIG. 3 is a partial sectional view showing a reflection type optical fiber sensor according to one embodiment of the present invention before and after sealing. The fiber 9 is partially exposed at the tip of the reflective optical fiber sensor before sealing. FIG.
1 is a sectional view showing a temperature sensor using a thermocouple according to an embodiment of the present invention before and after sealing. In addition, it is preferable to mix a thermally conductive filler with the thermoplastic resin used for sealing in the present embodiment.

As described above, according to the method of the present invention, the distal end of a member having a distal end surface can be reliably and easily sealed, and the sealed distal end contains air or transparency. Loss and no pinholes. Therefore, according to the present invention, for example, when the distal end portion of a member having a specific function such as an optical fiber sensor is sealed, the distal end portion can be sealed without impairing the original function of the member. For sealing purposes, for example, improvement in chemical resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sealing method according to an embodiment of the present invention.

FIG. 2 is a partial sectional view showing a transmission type optical fiber sensor according to an embodiment of the present invention before and after sealing.

FIG. 3 is a partial sectional view showing a reflection type optical fiber sensor according to an embodiment of the present invention before and after sealing.

FIG. 4 is a sectional view showing a temperature sensor according to an embodiment of the present invention before and after sealing.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Transmission optical fiber sensor 2 PFA tube 3 Convex heat insulating spacer 4 PFA plate 6 Heat block

Claims (1)

(57) [Claims] Claims: 1. A member is provided with a coating of a thermoplastic resin on a surface other than the tip end surface of a member, and then the tip portion of the coating is fused to a thermoplastic resin plate having the same shape as the peripheral shape of the tip portion. A method of sealing a tip portion of a member formed by cooling, wherein the fusion between the tip portion of the coating and the resin plate is performed by heating a heat block having a recess slightly larger than the tip portion of the coating. Then, a convex heat insulating spacer is inserted so that the convex surface faces outward, and then the resin plate is inserted and its end is melted, and then the tip end of the member having the coating is inserted and pressed against the resin plate. The method as described above.