JPH11294673A - Electrofusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate abnormal stop due to a short circuit of heating wires and shorten a welding time and a cooling time after the welding by zigzag arranging heating wires in the pipe axial direction at a fixed pitch in the circumferential direction on the joint faces with pipes on both sides of a cold zone to be buried thereon. SOLUTION: On the joint face with both side pipes, heating wires 3 are arranged at a distance from a center cold zone 2 to cold zones 7 on the end parts at a fixed pitch in the circumferential direction and zigzag in the pipe axis direction, and buried thereon. When at welding, a resin of the outer layer of a heating wire is shrinked, the position of the heating wires 3 is changed inward in the radial direction while making small the pitch in the circumferential direction following this. In a joint such as a socket joint 1 in which plastic pipes 5 are inserted from both sides, when the cold zones are provided on both ends of the joint and the center, the heating wires are zigzag arranged from the center cold zone 2 to the cold zone 7 on the joint end parts and buried thereon. However when the cold zone 2 is not provided, the heating wires are zigzag arranged between the cold zones 7 on both ends of the joint and buried thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusion joint which is used for connecting a plastic pipe in piping work with a plastic pipe, and in which a heating wire is embedded in a coil or spiral shape on a joint surface with the plastic pipe. .

[0002]

2. Description of the Related Art Electrofusion joints include socket joints, elbow joints, and the like used for connecting pipes to each other.
There are various types such as cheese joints, reducer joints, saddle joints used to connect branch pipes, and cap joints attached to the pipe ends, and the heating wire is coiled on the joint surface with the pipe. Alternatively, it is embedded in a spiral shape, and at the time of fusion with a tube, fusion is performed by causing a heating wire to generate heat by energization to melt the surrounding resin.

[0003]

The above-described electrofusion joint has the following problems. (1) The heating wire buried in the joint is subjected to internal stress such that the coil diameter or winding diameter becomes smaller due to the molding shrinkage force of the resin accompanying cooling after molding. While the thermal expansion occurs due to the temperature rise, the resin in the outer layer tends to shrink due to the melting of the resin around the heating wire, so that the heating wire bends and bends. When a short circuit occurs, an abnormal current is generated, and the energization is abnormally stopped.

(2) The inner diameter of the joint is larger than that of the portion without the heating wire because the heating wire portion is suppressed from forming shrinkage due to the rigidity of the heating wire, and the inner peripheral surface of the joint is not smooth. There are steps. In such an electrofusion joint, the heating wire shrinks under a low-temperature atmosphere in winter, and the coil diameter tends to be reduced. If this is repeated several times, the pipe cannot be inserted.

(3) Since the heating wire moves to the outer layer side of the joint due to thermal expansion during fusion, it is necessary to apply electric energy more than necessary to sufficiently melt the plastic pipe. The welding time is prolonged, and the cooling time until the fused portion is solidified is also prolonged. The present invention is to solve the above problems, that is, to eliminate abnormal stop due to short-circuiting of the heating wire, to ensure that the fitting with the plastic tube is not impaired for a long time,
An object of the present invention is to provide an electrofusion joint capable of short-circuiting a fusion time and a cooling time after fusion.

[0006]

The invention according to claim 1 is an electrofusion joint into which a plastic pipe is inserted, such as a socket joint, an elbow joint, a cheese joint, a reducer joint, a cap joint, or the like. Are arranged in a zigzag manner in the pipe axis direction at a constant pitch in the circumferential direction and embedded.

According to the joint of the present invention, when the resin of the outer layer of the heating wire shrinks at the time of fusion, the position of the heating wire also changes radially inward while the circumferential pitch decreases accordingly. The present invention, among the above-mentioned joints, in a joint in which a plastic pipe such as a socket joint is inserted from both sides, in a case where cold zones are provided at both ends and the center of the joint, heating wires are provided on both sides of the cold zone from the central cold zone. As it turns around when it reaches the end cold zone,
It is arranged in a zigzag manner from the central cold zone to the cold zone at the end of the joint, and is embedded. .

The invention according to claim 2 is characterized in that heating wires are arranged in a zigzag manner in the circumferential direction at a constant pitch in the tube axis direction and embedded in a coil shape on the joint surface with the tube. In the case of the present invention, the folded ends of the heating wires facing in the circumferential direction need to be separated so that even if the joint contracts, they do not come into contact with each other and short-circuit. When located in a line in the pipe axis direction, the joint has a cold zone extending in the pipe axis direction at one location in the circumferential direction. In order to solve this problem, it is preferable to shift each bent end in the circumferential direction.

Therefore, the invention according to claim 3 is characterized in that, in the invention according to claim 2, each bent end of the heating wire formed at a constant pitch in the tube axis direction is shifted in the circumferential direction. The invention according to claim 4 relates to a joint having a saddle portion such as a saddle joint or a service tee joint, in which a heating wire is arranged and embedded in a radially zigzag manner on a joint surface of the saddle portion and a pipe. It is characterized by the following.

The invention according to claim 5 is characterized in that the heating wire is arranged and embedded in a concentric zigzag manner on the joint surface of the saddle portion with the tube.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an electrofusion socket joint 1 shown in FIG. 1, a heating wire 3 is fixed in a circumferential direction from a cold zone 2 at a center to a cold zone 7 at an end on a joint surface with pipes on both sides. They are arranged and embedded in a zigzag manner in the tube axis direction at a pitch. In the figure, 4 is a terminal connected to the heating wire, and 5 is a plastic tube inserted into the joint 1.

FIG. 2 shows another example of the heating wire buried in the socket joint. The heating wire 6 is zigzag in the circumferential direction at a constant pitch in the pipe axis direction like the conventional joint, and alternately. Shift the position of the bent end a facing in the circumferential direction,
The heat generation density in the circumferential direction is made uniform. FIG.
Saddle fitting is connected to the heating wire 9 in the saddle section 8 of the Service Qi fitting.
Are arranged and embedded in a radial zigzag.

FIG. 4 shows the heating wire 1 embedded in the saddle portion 8.
1 is zigzag in a concentric manner, and the positions of the bent ends a facing each other are shifted.

[0014]

According to the first aspect of the present invention, since the heating wire has the same function as being arranged in a zigzag manner in the axial direction and buckling at the bent end, a short circuit occurs during fusion. It is possible to eliminate abnormal stop due to the problem, increase the rigidity by increasing the wire diameter of the heating wire to prevent short circuit, and it is not necessary to use special wire material, it can reduce the manufacturing cost, and it has a small wire diameter It is possible to freely change the resistance value with, and it is possible to expand the options, and it will not be affected by the rigidity of the heating wire in the radial direction of the joint, so the contraction of the joint will reduce the circumferential pitch of the heating wire While the position of the heating wire in the radial direction of the joint shifts inward, the pitch in the circumferential direction increases with the expansion of the joint, and the position in the radial direction of the joint shifts outward. When it comes In addition to returning to the position, there is no step on the inner peripheral surface of the joint.There is no hindrance to the insertion of the pipe, and the heating wire does not move away from the pipe at the time of fusion. Since fusion can be performed and the cooling time can be shortened, there is an effect that work can be performed in a short time.

The second aspect of the invention also has the same function as buckling with a bent end, so that abnormal stop due to short circuit can be prevented, and the rigidity of the heating wire is increased. There is no need to increase the diameter or use special wires, so the manufacturing cost can be reduced.The rigidity of the heating wire eliminates the effect of the heating wire. The inner diameter of the joint changes, and a step is not likely to occur on the inner peripheral surface of the joint.The insertion of the plastic tube can be performed without hindrance, and the heating wire does not move away from the tube during welding. Since it can be worn and the cooling time can be shortened, there is an effect that the work can be performed in a short time.

According to the third aspect of the present invention, the joint and the plastic pipe are fused over the entire circumference, so that there is no occurrence of uneven fusion in the circumferential direction. As in the invention described in claims 4 and 5, the joint having a saddle portion also has the same function as buckling with a bent end, so that an abnormality due to a short circuit occurs at the time of fusion. There is no need to stop, it is not necessary to increase the wire diameter to increase the rigidity of the heating wire, and it is not necessary to use a special wire material, so that the manufacturing cost can be suppressed, and the joint is not affected by the rigidity of the heating wire And the like.

[Brief description of the drawings]

FIG. 1 is a view showing a heating wire embedded in an electrofusion joint according to the present invention.

FIG. 2 is a perspective view of a heating wire having a coil shape.

FIG. 3 is a view showing a heating wire embedded in a saddle portion.

FIG. 4 is a view showing another example of the heating wire embedded in the saddle portion.

[Explanation of symbols]

 1. Electrofusion socket joint 2, 7, Cold zone 3, 6, 9, 11, Heating wire 4, Terminal 5, Plastic tube 8, Saddle part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuto Sugiyama 1-2-1, Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Chemicals, Inc.

Claims (5)

[Claims] 1. A socket joint, an elbow joint, a cheese joint,
An electrofusion joint into which a reducer joint, cap joint, or other plastic pipe is inserted, characterized in that heating wires are arranged at a constant pitch in the circumferential direction and zigzag in the pipe axis direction at the joint surface with the pipe and embedded. Electrofusion joint. 2. A socket joint, an elbow joint, a cheese joint,
An electrofusion joint into which a reducer joint, a cap joint, and other plastic tubes are inserted, in which heating wires are arranged at a constant pitch in the tube axis direction and zigzag in the circumferential direction on the joint surface with the tube, and embedded in a coil shape An electrofusion joint, characterized in that: 3. The electrofusion joint according to claim 2, wherein the bent ends of the heating wires formed at a constant pitch in the tube axis direction are shifted in the circumferential direction. 4. An electrofusion joint comprising a saddle joint, a service tee joint and other saddle parts,
An electrofusion joint characterized in that a heating wire is radially arranged in a zigzag manner at a joint surface with a tube and embedded therein. 5. An electrofusion joint comprising a saddle joint, a service tee joint and other saddle parts,
An electrofusion joint characterized in that a heating wire is concentrically arranged in a zigzag manner and embedded in a joint surface of a saddle portion with a pipe.