JPS6023596Y2 - pipe fittings - Google Patents

Description

[Detailed description of the invention] The present invention relates to a pipe joint for connecting pipe bodies made of thermoplastic synthetic resin, and particularly to pipe joints in which heating wires are embedded in a cylindrical body made of thermoplastic synthetic resin. Regarding improvements.

To connect pipes made of thermoplastic synthetic resin, such as polyethylene, the ends of the two pipes to be connected are brought together and heated with a heater, so that they are thermally welded together. connected.

In this case, a welding allowance is required between the end faces of both tubes, but
For example, it is difficult to obtain an appropriate welding allowance for pipes that are buried and fixed underground to transport city gas and cannot be moved.

For this reason, in the past, sealing was achieved by squeezing a sealing member from both ends into the gap between the cylindrical joint body into which the ends of both pipes are inserted, the inner peripheral surface of the joint body, and the outer peripheral surface of the ends of the pipe body. It is connected by a metal pipe joint containing a press ring.

According to this pipe joint, some variation in the distance between the end faces of both pipe bodies is allowed.

Since the joint body of this pipe joint is made of metal, it is easily corroded underground.

A prior art solution to the above-mentioned technical problem is shown in FIG.

This prior art uses a pipe joint 52 in which a heating wire 51 is embedded in the inner peripheral surface of a cylindrical body 50 made of thermoplastic HTM resin, for example polyethylene.

The heating wire 51 is embedded in a spiral along the axial direction of the cylindrical body 50, with a part of the outer periphery of the heating wire 51 being exposed from the cylindrical body 50.

For connection, the ends of the polyethylene tubes 53 and 54 to be connected are respectively fitted into both ends of the cylindrical body 50, and in this state the heating wire 51 is energized with electric power.

Then, the heat generated by the heating wire 51 heats the inner circumferential surface of the cylindrical body 50 and the outer circumferential surfaces of the tube bodies 53 and 54.

A tightening fitting (not shown) is attached to the entire outer circumference of the cylindrical body 50.
By keeping it fixed, thermal expansion of the cylindrical body 50 radially outward can be suppressed.

Therefore, the inner circumferential surface of the cylindrical body 50 and the outer circumferential surfaces of the tube bodies 53 and 54 are pressed against each other and are integrally heat-welded.

However, the heating wire 51 embedded in a spiral cannot be positioned over the entire circumference at both membrane ends 50a, 50b of the cylindrical body 50.

That is, at both membrane ends 50 a and 50 b of the cylindrical body 50 , there are portions 55 and 56 where the cylindrical body 50 and the tube bodies 53 and 54 are not thermally welded.

Therefore, after connecting the cylindrical body 50 and the tube bodies 53 and 54,
When a bending moment indicated by reference numeral 57.58 acts on the tube body 53.54, a stress concentration phenomenon occurs in the vicinity of the non-welded portions 55° and 56 of the two membrane ends 50a and 50b that are not thermally welded. -This may cause cracks.

The occurrence of this crack is caused by the cylindrical body 50 and the tube bodies 53, 5.
For example, if 4 is made of polyethylene and is in contact with a surfactant, this phenomenon is more likely to occur.

Thus, in the prior art, both membrane ends 5 of the tubular body 50
In 0a and 50b, the bending strength was poor due to the existence of portions 55 and 56 that were not thermally welded to the tube bodies 53 and 54.

To be more specific, when a bending moment 57 is applied as shown in FIG. The crank extends along the welded part with the body 53.

Therefore, an object of the present invention is to improve the bending strength of a pipe joint in which heating wires are embedded in the inner peripheral surface of a cylindrical body made of thermoplastic synthetic resin.

In the present invention, a heating wire 10 wound in a spiral shape concentric with the cylindrical body 6 is embedded in a cylindrical body 6 made of thermoplastic synthetic resin, and the thermoplastic synthetic resin is connected to both ends. The tubular body 6 and the tubular bodies 1 and 2 are fitted into each other at intervals in the axial direction of the tubes, and the heating wire 10 is energized to generate heat to thermally weld the cylindrical body 6 and the tubular bodies 1 and 2. In the joint, the heating wire 1
0 is embedded only in the remaining portions of the cylindrical body 6 excluding the extended portions at both ends in the axial direction, and the heating wire 10 of the cylindrical body 6 is
is formed by extending both ends in which the tube is not embedded outward in the axial direction, and a gap 16 is formed between the inner circumferential surface 9 of the extended portion of both ends and the outer circumferential surface of the tube bodies 1 and 2. It is a pipe fitting that

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG.

FIG. 1 shows the situation before a connection is made. Pipe bodies 1 and 2 made of thermoplastic synthetic resin, such as polyethylene, are buried underground in order to transport, for example, city gas.

The ends 3, 4 of these tubes 1, 2 are connected by a pipe joint 5 according to the invention.

The cylindrical body 6 of the pipe joint 5 is made of thermoplastic synthetic resin, such as polyethylene.

On the outer periphery of the cylindrical body 6, a fastening fitting 8 which can be opened and closed in half by means of a hinge 7, for example, is removably fitted.

A heating wire 10 embedded in the inner circumferential surface 9 of the cylindrical body 6 as described later.
A power supply 11 and a voltage regulator 12 are connected in series.

FIG. 3 is a perspective view of the pipe joint 5.

The heating wire 10 is embedded only in an embedding position 13 having a length 12 at a central portion extending a length 11 from both ends of the inner circumferential surface 9 of the cylindrical body 6 in the axial direction.

The heating wire 10 is embedded within the embedding position 13 in a spiral shape in the axial direction over the entire circumference, with a part of the outer periphery of the heating wire 10 being exposed from the inner peripheral surface 9.

The length 12 of this embedded position 13 is selected to be sufficiently larger than the length f3 between the ends of the tubes 1 and 2.

The lead wires 14.15 at both ends of the heating wire 10 are connected to the pipe body 1.2.
A slight gap 16 between the outer circumferential surface of the tube and the inner circumferential surface 9 of the cylindrical body 6.
17 to the outside.

The voltage is adjusted to a predetermined voltage by the voltage regulator 12, and the heating wire 10 is energized.

Then, the heating wire 10 generates heat, and the outer peripheral surface of the tubular body 1.2 and the inner peripheral surface 9 of the cylindrical body 6 are heated within the range of the length 12.

Therefore, the ends 3, 4 of the tubes 1, 2 thermally expand radially outward.

Since the tightening fitting 8 is fitted on the outer periphery of the cylindrical body 6,
Thermal expansion of the cylindrical body 6 in the radial direction outward is suppressed.

Therefore, the outer circumferential surfaces of the tubular bodies 1 and 2 and the inner circumferential surface 9 of the cylindrical body 6 are firmly pressed together.

Thus, the tube bodies 1 and 2 and the cylindrical body 6 are integrally heat welded.

The portions of the cylindrical body 6 at both ends in the axial direction where the heating wires 10 are not embedded are hardly heated.

Therefore, the gaps 16 and 17 between the inner circumferential surface 9 of the cylindrical body 6 and the outer circumferential surfaces of the tube bodies 1 and 2 each maintain a length of 1 in the axial direction and are not thermally welded.

FIG. 4 shows a heat welded portion 18 between the end 3 of the tube body 1 and the cylindrical body 6.
It is an enlarged sectional view of the vicinity.

A case is assumed in which a bending load is applied to the thermally welded portion 18 between the end portion 3 of the tubular body 1 and the cylindrical body 6 after the connection operation is completed and the fastening fitting 8 is removed.

When a bending moment acts on the tubular body 1 as shown by the arrow 19 in FIG.
A part of the bending load applied to the tubular body 1 is shared by the cylindrical body 6 .

In order to ensure this, in the present invention, the lengths 11 of the extended portions at both ends of the cylindrical body 6 in which the heating wires 10 are not embedded are made sufficiently large.

Therefore, the angular displacement amount α until the tubular body 1 comes into contact with the end of the inner circumferential surface 9 of the tubular body 6 is made as small as possible, and the tubular body 1 is supported by the tubular body 6.

This prevents stress from concentrating on the heat bonding portion 18.

Extended portions at both axial ends of the cylindrical body 6 in which the heating wires 10 are not embedded extend outward in the axial direction, and the inner peripheral surface 9 of the extended portions at both ends and the outer periphery of the tubular body 1.2 A gap 16 is formed between the surfaces.

The radial length of the gap 16 is designated by the reference δ.

Therefore, as shown in FIG.
When the bending moment shown by 9 is applied, the tube body 1
The outer circumferential surface of the cylindrical body 6 contacts the axially outer end 62 of the cylindrical body 6 .

Therefore, the tubular body 1 is bent by an angular displacement amount α between the welded position with the cylindrical body 6 and this axially outer end 62.

When a large bending moment 19 is applied to the tubular body 1, the tubular body 1 further bends by an angular displacement amount β using the axially outer end 62 as a fulcrum.

In this way, the tubular body 1 is angularly displaced by the angular displacement amounts α and β in two stages, and the stress acting on the tubular body 1 is reduced.

In contrast, in the prior art shown in FIG.
When the bending moment 57 is applied to the cylindrical body 50
is bent with the axially outer end 63 as a fulcrum, and the amount of angular displacement is when the same bending moment as in FIG. 82 is applied.
The amount of angular displacement is (α+β).

In this way, the tubular body 53 undergoes a large angular displacement around the single fulcrum 63.

Therefore, the stress concentration phenomenon at the base end 55a increases, and cracks are extremely likely to occur.

The present invention solves the problems of the prior art and alleviates the stress concentration phenomenon.

Also in the heat welded portion between the tubular body 2 and the cylindrical body 6, stress is prevented from concentrating on the heat welded portion in the same way as described above.

FIG. 5 is a longitudinal sectional view of another embodiment of the present invention, and corresponding parts of the embodiment shown in FIGS. 1 to 4 are given the same reference numerals.

In the pipe joint 26 in this embodiment, no heating wire is embedded in the cylindrical body 20 within the range of length t)2 between the end faces of the two tube bodies 1°2.

That is, the heating wires 24 and 25 are embedded in portions 22 and 23 near the center along the axis of the cylindrical body 20 and where the cylindrical body 20 and the tubes 1 and 2 overlap and fit together. It is rare.

The heating wires 24 and 25 are embedded at both embedded positions 22 and 23 on the inner peripheral surface 21 of the cylindrical body 20, with a part of the outer periphery of the heating wires 24 and 25 exposed from the inner peripheral surface 21 of the cylindrical body 20, It is embedded as described below.

FIG. 6 is a perspective view of the pipe joint 26.

The heating wire 24 is spirally embedded parallel to the circumferential direction and along the axial direction, with the folding point 27 located at the left end of the embedded position 22 in FIG.

The lead wires 28 and 29 of the heating wire 24 are drawn out to the right in FIG. 1 from the gap 30 between the cylindrical body 20 and the tube body 1.2.

The heating wire 25 is spirally embedded parallel to the circumferential direction and along the axial direction, with the turning point located at the right end of the embedding position 23 in FIG.

The lead wires 31 and 32 of the heating wire 25 are drawn out from the gap 33 between the cylindrical body 20 and the tube bodies 1 and 2 to the left in FIG.

When the heating wires 24 and 25 are energized, both embedded positions 22
, 23, the outer circumferential surfaces of the tubular bodies 1 and 2 and the inner circumferential surface of the cylindrical body 20 are heated and thermally welded together.

At this time, it is conceivable that a space is created around the outer periphery of the heating wire 24.25 within the cylindrical body 20 due to the difference in thermal expansion coefficient between the cylindrical body 20 and the heating wire 24.25.

In this embodiment, the length between the ends 3 and 4 of the tube 1°2 is 3.
No heating wire is embedded within the range, and the heating wires 24 and 25 are not exposed inside the tube after thermal welding.

Therefore, the space created around the outer periphery of the heating wires 24, 25 does not communicate with the inside of the tube and the outside of the cylindrical body 20, resulting in excellent airtightness.

In addition, in a pipe joint in which a heating wire is embedded in the inner peripheral surface of the cylindrical body within the length 13 between the ends 3 and 4 of the tube bodies 1 and 2, it becomes soft due to heating. The heating wire bites into the inner peripheral surface of the cylindrical body radially outward.

Therefore, a groove along the spiral heating wire may be formed on the inner circumferential surface of the cylindrical body.

In this case, if a bending load or the like is applied to the cylindrical body, stress may be concentrated in the grooves and cracks may occur.

However, in the embodiment shown in the fifth figure, no heating wire is embedded in the inner circumferential surface facing between the ends 3 and 4 of the tubes 1 and 2, so the groove is not formed, and therefore no cracks occur. There is no fear that this will occur.

Referring to FIG. 9, in the present invention, the heating wire 10 is connected to the cylindrical body 6.
It is embedded in a spiral shape concentric with the cylindrical body 6.

Therefore, the distribution of the fusion strength between the cylindrical body 6 and the tube body 1 in the tube axis direction is as indicated by reference numeral 71 in the upper part of FIG. Below , the distribution is as indicated by reference numeral 72.

In this way, the strength of the fusion bond between the cylindrical body 6 and the tube body 1 is made uniform in the axial direction, so that the strength is increased.

The experimental results of the inventor of this case are shown below.

In the above-mentioned embodiment, the tubes 1 and 2 are connected to the cylindrical body 6, and the bending moment 19 acts so that the tube 1 curves with a radius of curvature five times the outer diameter of the tube, and the atmosphere The temperature is 50℃, and the internal pressure supplied to the tube 1 is 2kq.
/ctA, no gas leakage was observed, and it was confirmed that no cracks were generated.

On the other hand, when a similar experiment was conducted using the prior art shown in FIG. 7, gas leakage occurred.

Thus, it was confirmed that according to the present invention, stress concentration is suppressed and the occurrence of cracks is prevented.

As described above, according to the present invention, the heating wire 10 that is spirally wound concentrically with the cylindrical body 6 is embedded in the cylindrical body 6, and therefore manufacturing is relatively easy.

Furthermore, the heating wire 10 is embedded only in the center of the cylindrical body 6 in the axial direction, that is, only in the remaining portion excluding the extended portions at both ends, so that the heating wire 10 of the cylindrical body 6 is not embedded. Since both ends are extended outward in the axial direction and a gap 16 is formed between the inner circumferential surface 9 of the extended portion of both ends and the outer circumferential surface of the tubes 1 and 2, a bending moment acts on the tubes 1 and 2. At this time, the tube bodies 1 and 2 hit the axially outer ends of the extended portions at both ends, and are angularly displaced in two steps.

Therefore, the occurrence of stress concentration is suppressed.

Therefore, the bending strength is improved.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, Fig. 2 is a cross-sectional view taken from line ■-■ in Fig. 1, Fig. 3 is a perspective view of the pipe joint 5, and Fig. 4 is a pipe body Thermal welding part 18 between the end 3 of 1 and the pipe joint 5
5 is a longitudinal sectional view of another embodiment of the present invention; FIG. 6 is a perspective view of the pipe joint 20 shown in FIG. 5; FIG. 7 is a longitudinal sectional view of the prior art; The figure is a sectional view for explaining the effect of the prior art shown in Fig. 7 and the embodiment of the present invention shown in Figs. 1 to 6, and Fig. 9 shows the welding strength of the above embodiment. It is a sectional view showing distribution. 1.2...tube, 3,4...end, 5
, 26... Pipe joint, 6, 20... Cylindrical body, 8... Tightening fitting, 9, 21... Inner periphery of the cylindrical body Face, 10. ．． 24゜25...Heating wire, 13,22.23...Heating wire embedding position, 1
6, 17...Gap, 18...Heat welded part, α, β...Amount of angular displacement of tube body 1, δ...
- The radial length of the gap 16.

Claims (1)

[Scope of utility model registration request] A heating wire 10 wound in a spiral shape concentric with the tubular body 6 is embedded in a tubular body 6 made of thermoplastic synthetic resin, and the tubular body made of thermoplastic synthetic resin is to be connected to both ends. 1 and 2 are fitted at intervals in the tube axis direction, and the heating wire 10 is energized to generate heat to thermally weld the cylindrical body 6 and the tube bodies 1 and 2. The heating wire 10 is embedded only in the remaining portion of the cylindrical body 6 excluding the extended portions of both ends in the axial direction, and both ends of the cylindrical body 6 where the heating wire 10 is not embedded are axially outward. A pipe joint characterized in that it is formed in an extended manner, and a gap 16 is formed between the inner circumferential surface 9 of the extended portions at both ends and the outer circumferential surface of the tube body 1.2.