JP2010216512A - Electrofusion joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrofusion joint capable of exhibiting reliable sealing performance. <P>SOLUTION: In the electrofusion joint 10, an electric heat layer 14 made of uncrosslinked polyethylene resin and having an electric heat wire 15 wound in an inside is formed on an inner peripheral part of a cylindrical joint body 11 made of crosslinked polyethylene resin, a pair of terminals 21 connected to both ends of the electric heat wire 15 is provided on an outer peripheral part of the joint body 11, and a holding cylinder 20 holding the terminal 21 is made of uncrosslinked polyethylene resin. A resin pipe 16 having an outer peripheral part made of uncrosslinked polyethylene resin is inserted into the joint body 11, a current is passed to the electric heat wire 15, and the electric heat layer 14 and the resin pipe 16 are thermally fused, and then, the terminal 21 is removed from the both ends of the electric heat wire 15, and the holding cylinder 20 is heated and melted, and the both ends of the electric heat wire 15 are sealed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrofusion joint (electric fusion joint) that can be used in, for example, a water supply system or a hot water system piping system and can exhibit highly reliable sealing performance.

  2. Description of the Related Art Conventionally, an electrofusion joint is known as a joint that is used in a water supply system or a hot water system piping system and has excellent joint strength of resin pipes. For example, a resin pipe joint comprising a joint body, an electrothermal fusion joint in the joint body, and a space for inserting a resin pipe whose surface layer is made of a non-crosslinked thermoplastic resin is proposed inside the electrothermal fusion joint. (See Patent Document 1). The joint body includes a tubular body into which pipes are inserted from two or more openings, a base portion joined to the inner surface of the tubular body and having a ring-shaped portion, and a stopper projecting inward from the base portion, The tubular body has an annular recess, and the electrothermal fusion joint is composed of a bobbin-like hollow body of a spirally wound coil made of a resin-coated wire coated with a non-crosslinkable thermoplastic resin.

  A hollow tube body formed of a crosslinked thermoplastic resin; and a heating element comprising a heating wire covered with a non-crosslinked thermoplastic resin layer, the heating element being on the inner peripheral surface side of the hollow tube body There has been proposed an electrofusion joint including a first spiral portion and a second spiral portion that are in contact with a member to be joined, and a connecting portion that connects them (see Patent Document 2). The connecting portion is provided with positioning means for cooperating with the core when the hollow tube main body is molded to hold the heating element inside the wall thickness of the hollow tube main body.

JP 2001-116182 A (the second page, the third page and FIG. 1) Japanese Patent Laying-Open No. 2006-153260 (Page 2, Page 3, and FIG. 1)

  In the joint described in Patent Documents 1 and 2, the terminal of the heating wire protrudes from the joint body in a state where the terminal of the heating wire is inserted and supported by a support cylinder embedded in the joint body or a support cylinder protruding from the joint body. Has been. While the heating wire and the terminal are made of metal, the support tube is made of resin, so that the terminal and the support tube are not completely in close contact with each other, and a slight gap is generated. For this reason, when a pipe was connected to the joint and water was circulated, there was a risk that the water would leak through the heating wire due to the water pressure and leak out of the joint through the gap between the terminal and the support tube. Therefore, these electrofusion joints have a problem that the reliability of the sealing performance is low.

  Accordingly, an object of the present invention is to provide an electrofusion joint capable of exhibiting highly reliable sealing performance.

  In order to achieve the above object, an electrofusion joint according to claim 1 is made of an uncrosslinked resin in which a heating wire is wound around an inner peripheral portion of a tubular joint body made of a crosslinked resin. The joint body is provided with a pair of terminals to which both ends of the heating wire are connected, and a holding cylinder for holding the terminals is made of uncrosslinked resin. Then, after inserting a resin pipe having at least an outer peripheral portion formed of an uncrosslinked resin into the joint main body and energizing the heating wire to thermally fuse the heating layer and the resin pipe, the terminal is connected to both ends of the heating wire. The holding cylinder is heated and melted to seal both ends of the heating wire.

  According to a second aspect of the present invention, in the invention according to the first aspect, the holding cylinder has a base end portion embedded in the joint main body, a tip end portion exposed, and the exposed portion heated and melted. It is constituted so that the both ends of a heat ray may be sealed.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the crosslinked resin is a crosslinked polyolefin resin, and the uncrosslinked resin is an uncrosslinked polyolefin resin.

  According to a fourth aspect of the present invention, in the invention according to the third aspect, the crosslinked polyolefin resin is a crosslinked polyethylene resin, and the uncrosslinked polyolefin resin is an uncrosslinked polyethylene resin.

  The electrofusion joint according to claim 5 is the invention according to any one of claims 1 to 4, wherein the resin pipe is formed of an uncrosslinked polyethylene resin on an outer periphery of an inner layer formed of a crosslinked polyethylene resin. The outer layer is a two-layer structure in which the outer layers are laminated.

According to the present invention, the following effects can be exhibited.
That is, in the electrofusion joint of the present invention, after the heating layer and the resin pipe are heat-sealed, the terminal is removed from both ends of the heating wire, and the holding tube is heated and melted to seal both ends of the heating wire. It is configured to. For this reason, both ends of the heating wire are covered and sealed with the heat-sealed portion of the holding cylinder. Therefore, the electrofusion joint can exhibit highly reliable sealing performance (watertight performance).

The longitudinal cross-sectional view which shows the electrofusion coupling in embodiment. (A) is a front view which shows the state which cut the spiral groove in the outer peripheral surface of the cylindrical body which forms a coupling main body, (b) is a side view which shows a cylindrical body. The front view which shows the state which wound the heating wire around the outer periphery of a pair of cylindrical body. The front view which shows the state which attached the terminal to the both ends of a heating wire from the state of FIG. The front view which shows the state which attaches a holding | maintenance cylinder to both terminals from the state of FIG. 4, and prepares a coil set. Sectional drawing which shows the state which has arrange | positioned the coil set of the state of FIG. 5 in a metal mold | die. Sectional drawing which shows the state which inserts a resin pipe into the both ends of an electrofusion coupling. Sectional drawing which shows the state which inserts a resin pipe into the both ends of an electrofusion coupling, and heat-seal | fuses. Sectional drawing which shows the state which pulls out the terminal attached to the holding | maintenance cylinder from the state of FIG. Sectional drawing which shows the state which applies the heating iron heated to the holding | maintenance cylinder from the state of FIG. 9, and is heat-seal | fused. FIG. 11 is a cross-sectional view showing a state in which the heat sealing of the holding cylinder is completed from the state of FIG. 10 and the resin pipe is connected to the electrofusion joint.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the drawings.
As shown in FIG. 1, a joint main body 11 constituting an electrofusion joint 10 is formed in a cylindrical shape from a cross-linked polyethylene resin, and the inner peripheral portion of the joint main body 11 protrudes toward the inner peripheral side at the center in the axial direction. An annular stopper 12 is provided, and a pair of annular accommodating portions 13 are recessed on both sides thereof. On the other hand, the pair of cylindrical heating layers 14 are formed of an uncrosslinked polyethylene resin, and are embedded with a heating wire 15 made of a conductive metal such as a nichrome wire wound therein. The heating wires 15 embedded in the pair of heating layers 14 are connected in series and are energized. The pair of electrothermal layers 14 are accommodated in the two annular accommodating portions 13, and insertion spaces 17 into which the resin pipes 16 are respectively inserted are formed inside the electrothermal layers 14.

  As shown in FIG. 7, the resin pipe 16 has a two-layer structure in which an outer layer 19 made of an uncrosslinked polyethylene resin is laminated on the outer periphery of an inner layer 18 made of a crosslinked polyethylene resin. The inner layer 18 exhibits characteristics such as heat resistance and creep resistance (a characteristic that suppresses an increase in strain with time under a constant load) and the like, and the outer layer 19 is capable of thermal fusion with the electrothermal layer 14. It is configured.

  As shown in FIG. 1, a cylindrical holding cylinder 20 having an enlarged leg portion 20a is embedded in the joint body 11 at the outer periphery of the joint body 11, and the distal end is exposed. Standing in the state. A through hole 22 extending in the axial direction is formed in the holding cylinder 20, and an end portion of the heating wire 15 is inserted into the base end side of the holding tube 20, while a cylindrical terminal 21 extends from the distal end opening of the through hole 22. The base end portion of the terminal 21 is connected to the end portion of the heating wire 15. The terminal 21 is made of a conductive metal such as copper. The heating wire 15 is connected to a control device (controller) (not shown) via both terminals 21 so as to store conditions such as the amount of current at the time of energization, the energization time, and the like amount of current is energized. . Then, the resin pipe 16 is inserted into the insertion space 17 of the joint body 11, and the heating wire 15 is energized through the terminal 21 to thermally bond the electric heating layer 14 and the outer layer 19 of the resin pipe 16. The both ends of the heating wire 15 are sealed with a heat-sealed portion 34 (see FIG. 11) formed by removing the both ends of the heating wire 15 and heating and melting the exposed portion of the holding cylinder 20.

Next, a method for manufacturing the electrofusion joint 10 configured as described above will be described.
As shown in FIGS. 2 (a) and 2 (b), the cylindrical body 23 forming the electrothermal layer 14 is made of uncrosslinked polyethylene resin, and a spiral groove 24 for winding the electrothermal wire 15 is formed on the outer peripheral surface thereof. Has been. The thickness of the cylindrical body 23, the depth of the spiral groove 24, and the like are set so that the heat fusion between the electrothermal layer 14 and the outer layer 19 of the resin pipe 16 is optimal. A pair of such cylindrical bodies 23 is prepared. Subsequently, as shown in FIG. 3, a pair of cylindrical bodies 23 are arranged to face each other at a predetermined interval, and the heating wire 15 is wound around a spiral groove 24 carved on the outer periphery of one cylindrical body 23 in that state. The coil 25 of the heating wire 15 is produced. The end of the heating wire 15 wound around one cylindrical body 23 is led to the spiral groove 24 of the other cylindrical body 23 and continuously wound to produce the coil 25 of the heating wire 15. The heating wire 15 may be a covered heating wire covered with an uncrosslinked polyethylene resin.

  Next, as shown in FIG. 4, cylindrical terminals 21 are attached to both ends of the heating wire 15 by welding or caulking. Subsequently, as shown in FIG. 5, the holding cylinder 20 formed of uncrosslinked polyethylene resin is press-fitted into the both terminals 21 so that the leg portions 20 a are positioned below, and the base end portions of both terminals 21 are The holding cylinder 20 is set so as to be positioned at a substantially central portion in the axial direction. In this manner, a coil set 26 in which the heating wire 15 is continuously wound around the pair of cylindrical bodies 23 is prepared.

  As shown in FIG. 6, the obtained coil set 26 is placed in a mold 27. That is, a cavity 28 having a shape corresponding to the coil set 26 is formed in the mold 27, and after placing the coil set 26 in the cavity 28, a pair of cylindrical slide pins 29 are inserted. The pair of holding cylinders 20 and the terminals 21 are inserted and fixed in the grooves 30 in the mold 27. In this state, a melt of uncrosslinked polyethylene resin to which a crosslinking agent such as an organic peroxide is added is injected from the gate 32 into the molding space 31 of the cavity 28. By such injection molding, an uncrosslinked main body cylinder portion for the joint main body 11 is formed on the outer periphery of the electrothermal layer 14. Since the main body cylinder portion is formed of the same uncrosslinked polyethylene resin as the electrothermal layer 14 and the holding cylinder 20, the main body cylinder portion is well bonded and integrated as a whole.

  Thereafter, the mold 27 is cooled, the pair of slide pins 29 are sequentially slid outwardly and pulled out, and the mold 27 is opened. Then, the molded product in the mold 27 is taken out and put into steam to heat the molded product. By this heating, the uncrosslinked polyethylene resin containing the crosslinking agent injected from the gate 32 is crosslinked. In this way, an electrofusion joint 10 as shown in FIG. 1 can be obtained.

  The resin pipe 16 is formed by an extrusion method. That is, an uncrosslinked polyethylene resin added with a crosslinking agent is used as the inner layer 18, and an uncrosslinked polyethylene resin not added with a crosslinking agent is used as the outer layer 19, and a pipe is obtained by extrusion molding using an extruder. Since the inner layer 18 and the outer layer 19 of the pipe are both uncrosslinked polyethylene resins, they are fused and integrated. By passing hot water through the obtained pipe, only the inner layer 18 is cross-linked by the cross-linking agent to become a cross-linked polyethylene resin.

Next, the usage method of the obtained electrofusion joint 10 is demonstrated.
When the resin pipes 16 are connected to both sides of the electrofusion joint 10, as shown in FIG. 7, the inner layer 18 is a crosslinked polyethylene resin and the outer layer 19 is uncrosslinked polyethylene in the insertion spaces 17 on both sides of the joint body 11. Resin pipes 16 formed of resin are respectively inserted. If the insertion of the resin pipe 16 is continued, as shown in FIG. 8, the tip ends of both the resin pipes 16 abut against the annular stopper 12 in the joint body 11. At this time, the outer peripheral surface of the outer layer 19 formed of uncrosslinked polyethylene resin of both resin pipes 16 contacts the inner peripheral surface of the electrothermal layer 14 of the joint body 11. Moreover, the inner peripheral surface of both the resin pipes 16 and the inner peripheral surface of the annular stopper 12 of the joint body 11 are flush with each other, so that no water flow resistance is generated.

  In this state, the heating wire 15 generates heat by energizing the heating wire 15 on the basis of the current amount and energization time set in advance by the controller, and the outer layer 19 of the uncrosslinked polyethylene resin and the resin pipe forming the heating layer 14. And the uncrosslinked polyethylene resin forming the melted and joined. The heat fusion between the electrothermal layer 14 and the outer layer 19 of the resin pipe 16 changes depending on the outside air temperature, the close contact state between the electrothermal layer 14 and the outer layer 19, etc. Can be adjusted. After energization, leave the joint until it cools down.

  After cooling, as shown in FIG. 9, when both terminals 21 are pulled with pliers or the like, the base end portion of the terminal 21 is separated from the end portion of the heating wire 15 in the holding cylinder 20, and the separated both terminals 21 are held. The tube 20 is pulled out. At this time, since the terminal 21 and the inner peripheral surface of the holding cylinder 20 are not bonded, the terminal 21 can be easily pulled out from the holding cylinder 20.

  After the both terminals 21 are pulled out from the holding cylinder 20, as shown in FIG. 10, the tip of the holding cylinder 20 has a conical shape heated as a heating jig to a temperature at which the uncrosslinked polyethylene resin melts. Attach and press the heating iron 33. By such an operation, the tip end portion of the holding cylinder 20 is melted to form the conical heat-sealing portion 34, and the opening of the through hole 22 of the holding cylinder 20 can be closed. In this case, since the holding cylinder 20 is formed of uncrosslinked polyethylene resin, the tip portion thereof is easily melted, and the opening portion of the through hole 22 can be easily blocked by the melted conical heat fusion portion 34. it can.

  In this way, as shown in FIG. 11, the resin pipe 16 can be connected to both sides of the electrofusion joint 10 and the holding cylinder 20 can be sealed. As a result, the water that penetrates through the heating wire 15 from the gap between the end of the resin pipe 16 and the joint body 11 is sealed and cut off by the heat fusion portion 34 of the holding cylinder 20 at the end of the heating wire 15, There is no risk of leakage.

The effects exhibited by the above embodiment will be described collectively below.
-In the electrofusion joint 10 of this embodiment, after the electrothermal layer 14 and the outer layer 19 of the resin pipe 16 are heat-sealed, the terminal 21 is removed from both ends of the heating wire 15, and the holding cylinder 20 is heated and melted. The both ends of the heating wire 15 are sealed. For this reason, both ends of the heating wire 15 are covered and sealed with the heat-sealing portion 34 of the holding cylinder 20. Therefore, the electrofusion joint 10 can exhibit highly reliable sealing performance.

  The holding cylinder 20 is configured such that the base end portion is embedded in the joint body 11, the tip end portion is exposed, the exposed portion is heated and melted, and both ends of the heating wire 15 are sealed. For this reason, the holding cylinder 20 can be firmly fixed to the joint body 11 and the exposed portion of the holding cylinder 20 can be easily and sufficiently melted by heating.

  Since the holding cylinder 20 is provided with a leg portion 20a having an enlarged diameter at the base end portion thereof, the holding cylinder 20 can be firmly fixed in the joint body 11 so as not to be pulled out, and the terminal 21 can be supported. It can be stabilized.

  -The crosslinked resin is a crosslinked polyolefin resin, and the uncrosslinked resin is an uncrosslinked polyolefin resin, so that the heat resistance and creep resistance of the electrofusion joint 10 can be improved and the connection to the resin pipe 16 is easy. And it can be done sufficiently. In particular, when the crosslinked polyolefin resin is a crosslinked polyethylene resin and the uncrosslinked polyolefin resin is an uncrosslinked polyethylene resin, the above effects can be further improved.

  The resin pipe 16 has a two-layer structure in which an outer layer 19 formed of an uncrosslinked polyethylene resin is laminated on the outer periphery of an inner layer 18 formed of a crosslinked polyethylene resin, so that an electrothermal layer of the electrofusion joint 10 is obtained. 14 can be smoothly fused.

In addition, the said embodiment can also be changed and actualized as follows.
A crosslinked polyolefin resin such as a crosslinked polybutene can be used as the crosslinked resin that forms the inner layer 18 of the joint body 11 and the resin pipe 16, and an uncrosslinked structure that forms the electrothermal layer 14, the holding cylinder 20, and the outer layer 19 of the resin pipe 16. An uncrosslinked polyolefin resin such as an uncrosslinked polybutene resin can be used as the resin.

  (Circle) the electrofusion joint 10 of the said embodiment can be formed in shapes, such as L shape and a dogleg shape. Further, the electrofusion joint 10 may be embodied as a type connecting one resin pipe 16 or a type connecting three or more resin pipes 16.

In the said embodiment, the heating wire 15 which connects between the two cylindrical bodies 23 can also be comprised so that the inside of the joint main body 11 may be wound 1 time or several times and let it pass.
A heating jig for heating and melting the tip of the holding cylinder 20 is a pyramid shape such as a quadrangular pyramid shape or a hexagonal pyramid shape or a truncated cone shape such as a truncated pyramid shape or a truncated pyramid shape. What was formed in can be used. In this case, the heat fusion part 34 at the tip of the holding cylinder 20 is formed in a cone shape or a frustum shape.

It is also possible to use a resin pipe 16 that is entirely formed of an uncrosslinked resin.
The electrofusion joint 10 can also be used for connection of water heating system piping and hot water supply system piping, floor heating piping, load heating piping, and the like.

Further, the technical idea that can be grasped from the embodiment will be described below.
The electrofusion according to any one of claims 1 to 5, wherein the heat fusion part formed by heating and melting the holding cylinder is formed in a conical shape or a frustum shape. Fittings. When constituted in this way, in addition to the effect of the invention according to any one of claims 1 to 5, the heat fusion part can be easily formed and the front end part of the holding cylinder is sufficiently sealed. can do.

  The electrofusion joint according to any one of claims 2 to 5, wherein the holding cylinder includes a leg portion having an enlarged diameter at a base end portion thereof. In this case, in addition to the effect of the invention according to any one of claims 2 to 5, the holding cylinder can be firmly fixed in the joint body so as not to be pulled out, and the terminal can be supported stably. Can be made.

  DESCRIPTION OF SYMBOLS 10 ... Electrofusion joint, 11 ... Joint main body, 14 ... Heating layer, 15 ... Heating wire, 16 ... Resin pipe, 18 ... Inner layer, 19 ... Outer layer, 20 ... Holding cylinder, 21 ... Terminal.

Claims (5)

A non-crosslinked resin heating layer around which a heating wire is wound is formed on the inner peripheral portion of the tubular cross-linked resin joint body, and both ends of the heating wire are formed on the outer peripheral portion of the joint main body. Comprising a pair of terminals to be connected, and a holding cylinder holding the terminals is made of uncrosslinked resin,
A resin pipe having at least an outer peripheral portion formed of an uncrosslinked resin is inserted into the joint body, and the terminal is removed from both ends of the heating wire after energizing the heating wire and heat-sealing the heating layer and the resin pipe. An electrofusion joint characterized in that the holding cylinder is heated and melted to seal both ends of the heating wire. The holding cylinder is configured such that a base end portion thereof is embedded in a joint body, a tip end portion is exposed, the exposed portion is heated and melted, and both ends of the heating wire are sealed. The electrofusion joint according to claim 1. The electrofusion joint according to claim 1 or 2, wherein the crosslinked resin is a crosslinked polyolefin resin, and the uncrosslinked resin is an uncrosslinked polyolefin resin. The electrofusion joint according to claim 3, wherein the crosslinked polyolefin resin is a crosslinked polyethylene resin, and the uncrosslinked polyolefin resin is an uncrosslinked polyethylene resin. 5. The resin pipe according to claim 1, wherein the resin pipe has a two-layer structure in which an outer layer made of an uncrosslinked polyethylene resin is laminated on an outer periphery of an inner layer made of a crosslinked polyethylene resin. The electrofusion joint according to any one of the above.

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