JP2747651B2 - Electrofusion joint and pipe connection method using the joint - 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 joint for interconnecting pipes made of a thermoplastic resin used as a gas pipe, a hot water pipe or a water pipe, and a method of connecting pipes using the joint. Things.

[0002]

2. Description of the Related Art An electrofusion joint having a built-in heating wire connected by heating and welding two pipes made of a thermoplastic resin is disclosed in, for example, Japanese Patent Publication No. Sho.
It is widely known in JP-A-41-29393, JP-A-2-186193, and JP-A-2-253091. Such an electrofusion joint heats and melts the outer peripheral portion of a thermoplastic resin pipe inserted from each opening end, so that the inner peripheral portion of a tubular joint body corresponding to each connected pipe is respectively charged. A heating element made of a heating wire is provided independently. Therefore, when a voltage is applied between the terminals of the heating element and energized, the heating element generates heat, and the inner peripheral portion of the joint body and the outer peripheral portion of the connected pipe corresponding to the heating element are melted and welded to each other. .

[0003] The joining of the connected pipes made of a thermoplastic resin by such an electrofusion joint is generally performed in a non-pressurized state. Therefore, in order to confirm the joint state between the joint body and the connected pipe, a shallow cylindrical small concave portion is formed in the outer peripheral portion of the resin joint body corresponding to the portion where the heating element is provided. Welding between the joint body and the pipe to be connected was confirmed by a part of the molten resin entering due to the pressure due to thermal expansion caused by heating by the body and changing the shape.

[0004]

However, the number of confirmation recesses formed in the joint body is usually very small, one for one heating element and two in total. Therefore,
Even if a change in shape due to thermal expansion is recognized in the recess formed in the outer peripheral portion of the joint body due to the heat generated by the heating element,
Due to the change in the shape of the concave portion, it cannot be considered that reliable welding was performed on the entire peripheral surface of the connected pipe. Therefore, various proposals have been made as a means for confirming the welding between the joint body and the connected pipe, but in each case, a new mechanism needs to be provided on the joint body to confirm the welding. May be restricted. Further, when welding the joint body and the pipe to be connected in a pressurized state, new capital investment is required, and there are many problems to be solved practically such as an increase in cost. In particular, when an electrofusion joint that is not completely welded to a pipe to be connected is used for a hot water supply facility, water leakage may occur from the welded portion due to use at high temperature and high pressure.

In view of the above situation, the present invention improves the flow of the molten resin in a portion where a heating element is mounted without applying pressure when connecting a pipe to be connected using an electrofusion joint. An object of the present invention is to provide an electrofusion joint capable of reliably welding a joint body and a pipe connecting method capable of visually confirming welding between a connected pipe and a joint body.

[0006]

In order to achieve the above-mentioned object, an electrofusion joint according to the present invention is used for connecting a connected pipe made of a resin compatible with a connected pipe made of a thermoplastic resin. An outer peripheral portion of a tubular joint body provided with a heating element on a contact surface corresponding to a heating area of the heating element
Can be visually checked for changes in shape due to melting.
A ring-shaped thin portion is formed.

More specifically, since two connected pipes made of thermoplastic resin are directly or indirectly connected to each other in a butt state, the pipes are made of a resin compatible with the pipes to be connected. the melt surrounds the outer periphery of the corresponding to the heating region of each heating element independently is allowed tubular joint body is incorporated in the heating element to the contact surface between the connecting pipe
This is a ring-shaped thin portion in which a change in shape due to the change can be visually confirmed .

A method for connecting a pipe using an electrofusion joint according to the present invention is a method for connecting a pipe made of a resin compatible with a connected pipe made of a thermoplastic resin and having a heating element on a contact surface with the inserted pipe connected. The surrounding portion of the provided tubular joint body corresponding to the heating area of the heating element is melted.
After the connected pipe is inserted into the electrofusion joint having a ring-shaped thin part where the change in shape can be visually confirmed , the heating element is energized, and the joint and the connected pipe are welded by the change in the shape of the thin part. It is characterized in that it is performed while visually confirming.

More specifically, in order to connect two connected pipes made of thermoplastic resin inside in abutting condition, the two pipes are made of a resin compatible with the connected pipe and are in contact with the connected pipe. a visual shape change due to melt surrounds the outer periphery of the the pair <br/> response to the heating region of each heating element of the tubular joint body is incorporated in each is independently a heating element to the surface
After inserting each object connection pipe from both ends of the electro-fusion joint to form a ring-shaped thin portion can be confirmed I, energizing the heating elements, the welding of the joint and the connecting pipe by a change in the shape of the thin portion This is performed while visually confirming.

In the present invention, there is no particular limitation on the resin itself, as long as the joint body is a resin compatible with the thermoplastic resin pipe to be connected. For example, the number of connected pipes to be connected may be one or two. In the case where two connected pipes are internally connected by welding, a single heating element for melting the resin may be provided for each connected pipe.

The thin portion formed on the outer peripheral portion of the joint body is provided at a position corresponding to the heat generating area of the built-in heat generating element, and the thickness of the thin portion is more than half the thickness of the joint body. Is not preferable because the strength of the joint body itself is weakened. On the other hand, if the distance between the heating element provided inside and the thin portion is too large, the change in shape, such as a swelling phenomenon, which appears in the thin portion due to melting of the resin, is not preferable. Furthermore, this thin portion surrounds the outer periphery of the joint body.
Te be those provided in a ring shape, it is preferable specifically to grooves having a depth and a predetermined width less than half of the groove of the wall thickness of at least the joint body.

[0012]

According to the electrofusion joint of the present invention, since a thin portion is formed in a ring shape at a portion corresponding to a heat generating region of the heat generating element on an outer peripheral portion of the joint main body containing the heat generating element, the electro fusion joint is connected to the joint main body. After the pipe is installed, when the heating element is energized, the joint body melts and the resin melted by the pressure due to thermal expansion flows uniformly over the entire circumference, and the joint body and the connected pipe are firmly connected without applying pressure when joining. Can be fixed. In addition, the pipe connection method using this electrofusion joint is such that when a heating element incorporated in the joint body is energized, the resin in the joint body is melted, and a portion of the melted resin enters the thin portion and becomes thin. the shape of the part varies over the entire circumference, which this change
By visually checking from the direction, it is not necessary to check the connection state by special means after the connection between the joint body and the connected pipe.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrofusion joint of the present invention and a method for connecting a pipe using the electrofusion joint will be described. In FIG. 1, reference numeral 1 denotes a nominal diameter of about 20 mmφ with both ends opened and a length of about 5 mm.
0 mm, wall thickness a cylindrical polybutylene te down resin joint body about 4 mm, the respective distal end portions of the inner to the center of the peripheral portion also polybutylene te down resin of the connection pipe P _1, P ₂ A ridge 2 for indirect butting connection is formed integrally around the entire circumference. 3 and 4 a heating element obtained by winding the heating wire 5, 6 covering the outer peripheral portion by polybutylene te down resin spirally, the outer peripheral portion of the connected pipe P _1, P ₂ in the joint body 1 The end portions 5a and 6a are both protruded to the outside. The integral mounting of the heating elements 3 and 4 in the joint body 1 is performed by molding a spirally wound coil in a state of being inserted into an injection molding die. There is no particular limitation on the means. Numerals 7 and 8 denote recessed groove-shaped thin portions provided on the outer peripheral portion of the joint main body 1 in correspondence with the heat generating regions of the heat generating members 3 and 4, respectively. 4, if it is the outer peripheral portion corresponding to the inside of the heat generating region, the front end portion, the central portion, and the
Any position corresponding to the base end may be used.
The central part of the mounting area 4 is most preferable in terms of confirmation and the like.

The thin portions 7 and 8 in the joint body 1 in this embodiment have a depth of 1/100 of the thickness of the joint body 1 of about 4 mm.
It is composed of a concave groove of about 1.5 mm or less and a width of about 4 mm.
At 200φ, the wall thickness increases as the diameter increases, but the depth of the concave groove forming the thin portion is always 以下 or less of the wall thickness of the joint body.

In order to connect the connected pipes P ₁ and P ₂ using the joint body 1 having such a configuration, first, the connected pipes P ₁ and P ₂ to be connected from each opening of the joint body 1 are connected. Is inserted until the tip comes into contact with the ridge 2 provided inside. Then, the terminals 5a, 6 protruding out of the joint body 1
When an AC power supply is connected to a and a voltage is applied, each of the heating elements 3 and 4 generates heat by energization, and not only the resin covering the heating wires 5 and 6 but also the joint body 1 in contact with the heating wires 5 and 6. And the outer peripheral portions of the connected pipes P ₁ and P ₂ are heated and melted. At this time, the thin portions 7, 8 formed of the concave grooves of the ring strip are formed on the outer peripheral portion of the joint body 1 corresponding to the buried areas of the heating elements 5, 6, respectively , over the entire circumference, so that the melting is performed. The resin flows uniformly along the thin portions 7 and 8 by the pressure due to thermal expansion, and at the same time, the thin portions 7 and 8
Part of the molten resin invades inside, and bulges (bulges)
Is formed. When the expanded portion is found in the entire circumference of the thin sections 7 and 8, since it is found that the resin is reliably molten, after stopping the energization to the heating members 3 and 4, projecting outside the joint body 1 End portions 5a and 6a are cut at appropriate positions.
I just need .

[0016] After the above-described object connected port <br/> ribs Te down resin outer the joint body 1 is approximately 19.5mm shown in Example pipes _{P 1} and _{P 2} respectively inserted, the terminal 5a, to 6a While applying a voltage of about 40 V to each of the thin portions 7 and 8 while observing the shape change, "When applied, the external shape of the thin portions 7 and 8 changed about 7 seconds after energization, and the heating elements 3 and 4 were raised.
Power supply to was stopped. Under these conditions, 50 electrofusion joints were prepared, and the connected pipes were connected respectively. The obtained joint pipe is JIS K 6779 /
In the method specified in the hot internal pressure creep test of 8.6 polybutylene te down fittings, coupling portion was checked for leakage generation of (welded portion), 50 all hot internal pressure creep of binding the pipe The test passed with no leaks.

COMPARATIVE EXAMPLE On the other hand, as shown in FIG. 2, a joint body 11 having the same size, shape and material as that of the above embodiment was prepared.
Integrally arranged with the same heating element 13, 14 and the heating element 3, 4 in the respective Example to the inner peripheral portion of the connection pipe pipe P ₁ and P ₂ and abutting joint body 11 made of the same material And the joint body 11 corresponding to these heating elements 13 and 14
The outer peripheral portion to a depth of approximately 1 · 5 mm, to form a concave holes 17 and 18 having a diameter of about 4 mm, both ends Karapo <br/> rib Te down resin outer shape of the joint body 11 is approximately 19.5mm of After inserting each to be connected pipes _{P 1} and _{P 2} of the terminal 15a, 16
When a voltage of about 40 V was applied to each a while observing the shape change of the holes 17 and 18, the bottoms of the holes 17 and 18 were raised when about 6.2 seconds had elapsed. Power supply was stopped. Under these conditions, 50 electrofusion joints were prepared, and the connected pipes were connected respectively. When the obtained connection pipes were examined for the presence or absence of leakage by the same method as in the above example, 8 out of 50 connection pipes did not pass the hot internal pressure creep test, and leakage occurred. In the drawings, reference numerals 15 and 16 denote heating wires constituting the heating elements 13 and 14, respectively.

[0018]

Effects of the Invention Electro fusion joint of the present invention, the heating element is provided on the portion contacting with the outer peripheral portion of the connected pipes in a tubular fitting body, the outer peripheral portion of the joint body and the corresponding heat generating area of the heating element Since the surrounding thin part is formed in a ring shape, when the heating element is energized with the connected pipe inserted into the pipe, the joint body, the heating element and the connected pipe are melted, and the molten resin Flow uniformly over the entire circumference of the joint body and weld to each other. Therefore, even if the joint main body is not pressurized in a state where the connected pipe is inserted, the molten resin flows uniformly along the thin portion, and the joint main body and the connected pipe can be reliably welded.

A method for connecting a pipe using an electrofusion joint according to the present invention uses a joint body in which a thin portion surrounding an outer peripheral portion corresponding to a heat generation area of a built-in heat generator is formed in a ring shape. When the heating element is energized after the pipe to be connected is inserted into the inside, a part of the resin melted by the energization of the heating element enters the thin-walled part and changes its shape. By visually checking, it is possible to know that the joint body and the connected pipe are welded to each other without using an inspection device or the like. In addition, since the joint body with the thin-walled part formed in a ring shape corresponding to the heat generation area of the heating element built in the outer peripheral part is used, the molten resin can be removed without pressing the joint body with the connected pipe inserted. It flows uniformly along the thin portion, and the joint body and the connected pipe can be reliably welded.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of an electrofusion joint of the present invention.

FIG. 2 is a partially cutaway front view of a conventional electrofusion joint.

[Explanation of symbols]

1 joint body 3,4 heating elements 5 and 6 heating wire 5a, the thin portion P ₁ of 6a terminals 7 and 8 ring, _{P 2} the connection pipe

Continued on the front page (72) Inventor Tadanobu Suzuki 7 Aron Kasumi-cho, Minato-ku, Nagoya City Inside (72) Inventor Tadashi Hasegawa 7-Aron Kasumi Co., Ltd. 1 at Funami-cho, Minato-ku Nagoya-shi (56) References JP-A-3-183528 (JP, A) JP-A-4-203587 (JP, A) JP-A-6-137481 (JP, A)

Claims (6)

(57) [Claims] 1. A heating area of a heating element of a tubular joint body made of a resin compatible with a connected pipe made of a thermoplastic resin and provided with a heating element on a contact surface with an inserted connected pipe. the shape change by melt surrounds the outer peripheral portions corresponding to
An electrofusion joint characterized by forming a ring-shaped thin portion that can be visually confirmed . 2. A connecting pipe made of a resin having compatibility with the connected pipe and connecting the two connected pipes made of thermoplastic resin directly or indirectly in a butt state. shape change due to melting surrounds the outer periphery of the corresponding to the heating region of each heating element independently is allowed tubular joint body is incorporated in the heating element to the contact surface
An electrofusion joint characterized by forming a ring-shaped thin portion that allows visual confirmation . 3. The thin portion surrounding the outer peripheral portion of the joint main body and formed in a ring shape has a thickness of at least one of the joint main body.
The electrofusion joint according to claim 1 or 2, wherein the ratio is not more than / 2. 4. A thin-walled portion surrounding the outer peripheral portion of the joint main body and formed in a ring shape has a thickness of not more than 肉 of the thickness of the joint main body and has a groove shape. 2. The electrofusion joint according to 2. 5. A heat-generating region of the heat-generating body of a tubular joint body made of a resin compatible with a connected pipe made of a thermoplastic resin and having a heat-generating body provided on a contact surface with the inserted connected pipe. the shape change by melt surrounds the outer peripheral portions corresponding to
After inserting the connected pipe into the electrofusion joint having a ring-shaped thin part that can be visually confirmed , the heating element is energized, and the welding between the joint and the connected pipe is visually confirmed by a change in the shape of the thin part. A method for connecting pipes using an electrofusion joint, wherein 6. A heating element made of resin compatible with the connected pipe and connected to the connected pipe in order to connect two connected pipes made of a thermoplastic resin inside in a butt state. the outer peripheral portion of the corresponding to the heat generating region of the heat generating element of the tubular joint body is incorporated in each is independently a
After inserting the connected pipes from both ends of the electrofusion joint forming the ring-shaped thin-walled part, which can be visually confirmed for the shape change due to the surrounding melting .
A method for connecting a pipe using an electrofusion joint, characterized in that the heating element is energized and the welding between the joint and the pipe to be connected is visually confirmed by a change in the shape of the thin wall portion.