JP2998057B2 - Electrofusion coil and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusion coil used for piping and the like made of a thermoplastic resin and a method of manufacturing the electrofusion coil.

[0002]

2. Description of the Related Art There are known a method of connecting a synthetic resin pipe used for a pipe of gas or water supply, for example, by a method of connecting with an adhesive or a method of thermally melting a portion to be connected. Many of the latter methods of hot-melt connection
An electric welding coil in which a linear heating element coated with a resin of the same quality as the connected pipe is wound in a coil at a predetermined pitch inside the connection end of the connected pipe made of a thermoplastic resin, and then connected. Insert the end of the pipe inside the coil for electrofusion, energize the coil for electrofusion to cause the linear heating element to generate heat and melt the coating resin, and the inner peripheral surface of the connected pipe and the outer peripheral surface of the connection pipe Are fused and integrated.

[0003] An electrofusion coil used in such an application has a linear heating element coated with a thermoplastic resin such as polyethylene as disclosed in Japanese Patent Application Laid-Open No. 3-37496. The thing is wound in a coil shape around a roller having a predetermined diameter, and while maintaining that state, an externally heated hot plate is brought into contact with at least one location in the circumferential direction to melt and solidify the coating resin, thereby forming a fused portion. By forming, adjacent coils are integrated with each other, and the shape thereof is fixed.

[0004]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 3-37496
The electrofusion coil proposed in Japanese Patent Application Publication is extremely simple and easy to manufacture because the coated wires wound in a coil shape are fixed so as not to be fused and separated from each other at at least one location in the circumferential direction. Has advantages.

[0005] However, the proposed electrofusion coil has a problem that an extra heat history is added to the resin coating the linear heating element when the coil is insert-molded at the time of manufacturing the coil. resin contacting the heat appliances covering the linear heating element to melt the coating resin, when you fixed by fusing the covered wire between the linear heating element covered fused portion is thermally degraded It was found that the fusion strength was reduced in that region when current was applied and the melt was integrated.

As a result, for example, when a pipe made of the same material as the joint provided with the electric welding coil is supplied with electricity to the linear heating element and melted and fused, the outer peripheral surface of the electric welding coil and the outer peripheral surface If the joint does not completely melt at the boundary surface with the inner peripheral surface of the joint, especially in the area of the coating fusion joint, or the fusion strength is weak, the part concerned will be subject to a water leakage route when used under high temperature and high pressure. There was a possibility that.

[0007] That is, as shown in FIG.
In many cases, the interface indicated by a ′ and eho ′ is insufficiently fused. Therefore, it is necessary to sufficiently perform the fusion at the boundary surfaces indicated by ro-ro ', ha-ha', and ni-ii to block the water leakage route.・ Since a continuous coating fusion portion is formed at the boundary surface indicated by c ′ and d ′, if the fusion portion is thermally degraded and sufficient fusion / fusion is not performed in that region, It was found that the fused portion was a water passage. In this case, in the drawing, D, water that has entered through the gap indicated by E, the problem of leakage to the outside shown in the figure F via the interface 'interface → B-B' of Lee Lee occurs.

According to the present invention, it is provided that the heating of the coating resin for coating such a linear heating element causes thermal deterioration of the coating resin, and the fusion strength decreases when the portion to be connected is thermally melted. Heading, one is to form the fused part for holding the coil shape discontinuously, and the other one is good fusion performance by setting the temperature at the time of forming the fused part to a specific range. An object of the present invention is to provide an electrofusion coil and a method of manufacturing the coil.

[0009]

To achieve pre-Symbol purpose Means for Solving the Problems], electrical fusing coil according to claim 1 of the present invention,
A predetermined coil group consisting mainly of a sleeve formed by winding a coated wire in which a linear heating element is coated with a thermoplastic resin into a coil shape is simply described.
Position as, discontinuously to form a fused portion along the length of the co <br/> yl group on the outer periphery of the coil groups of the sleeve mainly
This discontinuous fusing allows the adjacent coated wire to be coiled.
It is characterized in that the coils are connected to each other over the entire length of the group to maintain the coil shape.

[0010] The electrofusion core according to claim 2 of the present invention.
Il is fused to the sleeve-based coil group
Part of the coil group over the entire outer periphery of the sleeve
It is characterized by being formed in the length direction.

According to a third aspect of the present invention, there is provided a method for manufacturing an electric fusion coil, wherein a linear heating element is covered with a polybutene resin and wound into a coil shape to form a sleeve main body. When continuously forming the fused part along the coil length direction and holding the coil shape,
The heating temperature is set to 150 ° C. or more and 250 ° C. or less to form a fused portion.

In the present invention, the linear heating element may be a linear element such as a nichrome wire or a carbon fiber which generates heat when energized, and the thermoplastic resin covering the linear heating element may be a synthetic resin pipe to be connected. It is preferable that they are of the same quality or have high affinity, and specific examples thereof include polyvinyl chloride, polyolefin, polyamide, polyacetal, and polybutene. Also,
Even if the number of linear heating elements covered with the thermoplastic resin is one,
A book may be used, and the linear heating element may be coated directly or with an insulating material, and then coated with a thermoplastic resin.

[0013] The coated wire covered with the thermoplastic resin is wound around a cylindrical roller to form a helical shape with a sleeve as a main body.
In which discontinuously to form a fused portion along the <br/> length direction of the coil group in its outer periphery a predetermined coil group as a unit. This fused portion is formed discontinuously over the entire length by bringing a plate-shaped heating element having a predetermined length into contact with the outer peripheral portion of the sleeve-based coil group . Adjacent covered wires are connected to each other over the entire length to maintain the coil shape. Fused portion forming the coils of the sleeve entity may be formed only on one surface along the length of the coil group, it is preferably formed on the outer peripheral portion throughout.

In the case where the fused portion is formed discontinuously in the main body of the sleeve, the fusion may be performed basically at a temperature equal to or higher than the melting point of the coating resin. Absent. For example, the temperature does not need to be 250 ° C. or lower as in the case of polybutene resin, and the temperature is 300 ° C.
° C or higher.

In this case, even when a part of the fused portion is in an incompletely fused / fused state when being fused / fused by energization, it is also possible to use the ii ′ in the drawing shown in FIG. Even if the interface between the roller and the roller was insufficiently fused, the fused portion was formed discontinuously along the coil length direction on the outer periphery of the sleeve main body. Since the fusion / fusion region always exists in a state of being connected in the circumferential direction, a route that may cause water leakage is surely cut off, and no water leakage occurs during use.

On the other hand, when the fused portion is formed continuously in the sleeve main body, the temperature of the heating element, that is, the heating temperature is set at a temperature higher than the melting point of the coating resin, but is maintained at a temperature lower than a temperature causing thermal degradation. In this way, fusion and fusion of the parts to be connected (for example, a pipe and a joint) are performed well without causing thermal deterioration of the fusion portion. Sufficient fusion strength is obtained.

Therefore, when the linear heating element is covered with the polybutene resin, the temperature exceeding the melting point (130 ° C.) of the polybutene resin, from 150 ° C. to 250 ° C.
C., particularly a temperature range of 180 ° C. to 220 ° C. is preferable, and if the heating temperature is close to the melting point, it takes time for melting, so it cannot be said that it is preferable. If the temperature is 250 ° C. or higher, the resin is heated. It is not preferable because it is affected. In the case where the fused portion is formed discontinuously in the sleeve main body,
Needless to say, it is desirable that the heating is performed while the temperature of the heating element is maintained at a temperature equal to or higher than the melting point and equal to or lower than a temperature at which thermal degradation occurs.

Hereinafter, a specific example of the electrofusion coil according to the present invention will be described with reference to FIGS. An electrofusion coil 1 shown in FIG. 1 has a coating wire 3 obtained by coating a single nichrome wire 2 having a predetermined diameter with a polybutene resin and folding the coated wire 3 at an inflection point 4 to a roller R having a predetermined shape. A plate-like heating element heated to a predetermined temperature along the coil length direction is brought into contact with the outer peripheral portion of the one-way sleeve main body 1 (for convenience, denoted by the same reference numeral as the electrofusion coil) obtained by winding. By heating the relevant portion, the six fused portions 4a to 4f
Are formed discontinuously.

That is, the adjacent covered wires 3a to 3d are fused by the fused portion 4a, and the covered wires 3d to 3d are fused by the fused portion 4b.
f, the covered wires 3f to 3h are integrated by the fused portion 4c, 3i and 3j are fused by the fused portion 4d, the covered wires 3h to 3k are fused by the fused portion 4e, and the coated wires 3k to 3n are fused by the fused portion 4f. As a result, the sleeve main body 1 is inseparably connected to maintain a predetermined shape.

The electric welding coil 11 shown in FIG. 2 is wound around a roller so that a covered wire 31 obtained by covering one nichrome wire 21 with a polybutene resin can be divided right and left at a center point 41. Two coil groups A,
A coil-shaped heating element heated to a predetermined temperature in the coil length direction is applied to the outer peripheral portion of each of the coil groups A and B. By contacting and heating the corresponding portions, six fused portions 41a to 41f and 41h to 41l are respectively formed discontinuously, and the respective coil groups A and B are inseparably connected to form a predetermined shape. It is what was kept.

[0021]

[Action] Electrical fusing coils of the present invention, discontinuously to form a fused portion along the length of the coil group in the outer peripheral portion of the coil groups of the sleeve main body, the discontinuous fused portion The adjacent covered wires are connected to each other over the entire length to maintain the coil shape, so that only a very small area is required to cause thermal degradation, and the covered wire is discontinuously fused to cover the entire length of the sleeve. Can be held in a predetermined shape.

Further, the method for manufacturing the coil for electrofusion according to the present invention is characterized in that, when the linear heating element coated with the polybutene resin is held in a predetermined shape, the fusion zone is continuously or discontinuously formed on the outer periphery thereof. By setting the temperature of the heat generating element in a certain range, the coil for electrofusion can be formed without affecting the subsequent electrofusion.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the coil for electrofusion according to the present invention will be described below. Example 1 A coated wire was formed by coating a nichrome wire having a diameter of 1.2 mm with a polybutene resin, and the obtained coated wire was wound around a roller six times so as to be the same type as that of FIG. 1 to form a sleeve main body. A plate-shaped heating element heated to a temperature of 300 ° C. is contacted along the coil length direction of the outer periphery of the sleeve main body,
The coated wire was heated to form a fused portion discontinuously to obtain an electrofusion coil in which the sleeve main body was maintained in a predetermined shape. With the thus obtained electrofusion coil inserted into the injection molding mold, polybutene resin is injected to produce 50 electrofusion joints, and a connected pipe made of polybutene resin is fused to each electrofusion joint. I wore it. When the electrofused joint fused to the pipe to be connected was inspected for the occurrence of leakage at the fused portion by a method specified in 8.6 KIP hot joint creep test of 8.6 of JIS K 6779 / polybutene pipe joint, All 50 passed the hot internal pressure creep test with no leaks.

Comparative Example 1 A nichrome wire having a diameter of 1.2 mm was covered with a polybutene resin to form a covered wire in the same manner as in Example 1, and the obtained covered wire was wound around a roller six times to form a sleeve main body. A plate-like heating element heated to a temperature of 300 ° C. is brought into contact with and heated along the coil length direction of the outer periphery of the sleeve main body, and a fused portion is continuously formed over the entire length of the sleeve main body to form the sleeve main body. An electrofusion coil maintained in a predetermined shape was obtained. The thus obtained electrofusion coil is inserted into a mold for injection molding, and the polybutene resin is injected to produce 50 electrofusion joints. I wore it. Then, when a hot internal pressure creep test was carried out in the same manner as in Example 1, 22 out of 50 pieces did not pass and water leakage occurred. Therefore, when the rejected electrofusion joint 31 was cut vertically and its cross section was observed, as shown in FIG. 3, the inner peripheral portion of the electrofusion coil and the connected pipes P ₁ , P ₂ were not found. Was completely fused, but between the continuous fused portion formed on the outer peripheral portion of the electrofusion coil and the inner peripheral surface of the electrofusion joint 31 in contact with the outer peripheral surface (boundary surface). ) Gap 34
(Incompletely melted portion) was confirmed. This is because the coating resin is thermally degraded over the entire length due to the heating of the outer peripheral portion by the heating element, and even if the linear heating element generates heat, the heat melting of the portion is poor, and the resin constituting the electro-fusion joint 31 is fused well. It is due to the result of not wearing. In the drawing, 32 indicates a nichrome wire, and 33 indicates a covered wire.

Embodiment 2 As shown in FIG. 4, a single wire of nichrome 52 having a predetermined diameter is coated with a polybutene resin, and a covered wire 53 obtained by folding the wire at an inflection point 54 is formed into a roller having a predetermined shape. Was wound six times to obtain a sleeve main body 51 for one direction. Next, a plate-shaped heating element heated to a predetermined temperature along the coil length direction is brought into contact with the outer peripheral portion of the sleeve main body 51,
By heating the portion, a fused portion 55 continuous over the entire length was formed to form an electrofusion coil.
At that time, the temperature of the heating element was set to 150 ° C, 200 ° C, 250 ° C.
In the state of inserting the electrofusion coil obtained at each temperature into the injection mold, polybutene resin was injected, and 50 electrofusion joints were prepared, and the same as in Example 1. When a hot internal pressure creep test was performed on
All electrofused joints passed the test, confirming that the heating temperature was a very important factor in forming the fusion around the sleeve.

[0026]

Effects of the Invention Electrical fusing coils of the present invention, the time of coated wire sleeves principal shape retaining wound in a coil shape, on its outer <br/> periphery a predetermined coil groups of the sleeve main body as a unit Since the fused portion is formed discontinuously along the length of the coil group and the adjacent coated wires are interconnected over the entire length by the discontinuous fused portion, the strength is reduced by the fusion. Since there is no possibility of concentrating the area at one location and the area of the fused portion can be reduced, a reduction in the strength of the sleeve main body after the formation of the fused portion can be suppressed. In particular, the fusion portion is formed with respect to the coil group mainly composed of the sleeve.
When the joints and pipes are melt-fused using the electrofusion coil obtained by forming the wire discontinuously, the imperfections caused by the thermal deterioration in the fused part of the resin covering the linear heating element Prevents a fused part from becoming a water leakage route.

According to the method of manufacturing an electrofusion coil of the present invention, a fused portion is formed continuously or discontinuously on an outer peripheral portion of a sleeve main body in which a coated wire in which a linear heating element is coated with a polybutene resin is wound in a coil shape. When maintaining the shape by forming, by setting the heating temperature within a certain range, the fused portion can be formed without causing the polybutene resin to thermally degrade, and when electricity is fused by energizing Eliminates incomplete melting caused by thermal degradation of polybutene resin,
Joints and pipes can be reliably fused and fused.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of an electrofusion coil according to the present invention.

FIG. 2 is a front view showing another embodiment of the electrofusion coil of the present invention.

FIG. 3 is a longitudinal sectional view of an electric welding coil described as a comparative example.

FIG. 4 is a front view showing an example of the electrofusion coil obtained by the method for producing the electrofusion coil of the present invention.

FIG. 5 is a longitudinal sectional view of a conventional electrofusion coil.

[Explanation of symbols]

 1,11 Electric fusion coil 2,21 Linear heating element 3,31 Coated wire 4a-4f, 41a-41l

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuto Sato 74 Aaron, Funami-cho, Minato-ku, Nagoya City Within Kasei Co., Ltd. (72) Inventor Hiroki Exit 74 Aron, 1-Funamicho, Minato-ku, Nagoya-shi (56) References JP-A-5-312298 (JP, A) JP-A-3-37496 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16L 47/02

Claims (3)

(57) [Claims] A sleeve-shaped predetermined wire formed by winding a coated wire in which a linear heating element is coated with a thermoplastic resin in a coil shape.
In a unit of the coil group , a fused portion is formed discontinuously along the length direction of the coil group on the outer peripheral portion of the coil group mainly composed of the sleeve, and the discontinuous fused portion is formed. Characterized in that adjacent covered wires are connected to each other over the entire length of the coil group to maintain the coil shape. Wherein the fused portion formed on the coil groups of the sleeve main body, electrical fusing coil according to claim 1, characterized by forming the length of the coil group over the outer periphery entire area of the sleeve main body . 3. A linear heating element is covered with a polybutene resin and wound in a coil shape to form a sleeve main body, and a fused portion is continuously formed on an outer peripheral portion of the sleeve main body along a coil length direction. To maintain the coil shape
A method for producing an electric welding coil, wherein a heating portion is formed at a heating temperature of 150 ° C. or more and 250 ° C. or less.