JP2002213678A - Electric fusion joint and its forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric fusion joint along with its forming device, having an arrangement such that electric heater wires are embedded at the inside circumferential surface of a pipe socket and the resin in the boundary zone between the joint and a pipe to be connected is melted by the heat emitted from the heater wires, so that the two members are melted and connected together, whereby the molten resin is prevented from protruding from the gap between the pipe socket and the pipe to be connected. SOLUTION: The inside circumferential surface of the pipe socket 3 is provided with a resin sump 7 to allow molten resin to stagnate, by forming a plurality of grooves 7a at a certain spacing in the circumferential surface direction, the grooves 7a, extending toward the open side of the socket from a starting point located near the open end part of that part 9, where the heater wires are embedded. The molten resin, melted by the heat emitted from the heater wires 8, can stagnate in the sump 7, and there is no risk of the molten resin leaking or ranging out through the gap between the joint body 2 and the pipe to be connected P1 (or P2), so that it is possible to avoid deterioration of appearance and a drop of the jointing strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-fusion joint (electro-fusion joint) for fusing and joining tubes of synthetic resin such as gas pipes, water pipes, hot water pipes and the like by electroheating, and to manufacture the same. It relates to a molding device.

[0002]

2. Description of the Related Art An electric fusion joint (electrofusion joint) is used as a joint for connecting synthetic resin tubes such as a gas pipe, a water pipe, and a hot water supply pipe. This electric fusion joint is a joint that melts the resin at the boundary portion between the joint and the connected pipe by heat generated when electricity is supplied to the heating wire and fusion-splices the two. For example, as shown in FIG. Pipe sockets 52, 52 into which the connected pipes P1, P2 can be inserted are provided at both ends of the joint body 51, and a step portion (stopper) 53 is provided at the back side of each of the pipe sockets 52 to form the pipe sockets 52, 52. A space is defined as a small-diameter portion 54, and a heating wire 55 is helically embedded in the inner peripheral surface of each pipe socket 52, and both ends of the heating wire 55 project from the outer peripheral surface of each pipe socket 52. Terminal plug 5
An electrofusion joint 50 and the like having a configuration connected inside 6, 56 are known, and manufactured, for example, as follows.

As shown in FIG. 6, a splittable mold 61 having a cavity 61a substantially corresponding to the outer structure of the electrofusion joint 50 is provided, while a contour substantially corresponding to the inner structure of the electrofusion joint 50 is provided. A pair of cylindrical mandrels (cores) 63, 63 having
The heating wires 55 are wound around the outer peripheral surface of the mandrel by abutting the ends of the heating wires 63, and both ends of the heating wires 55 are connected to terminal pins 56 a sandwiched by the terminal holding mold 64.
Next, the terminal holding dies 64, 64 are mounted on the locking concave portions 61b provided on the inner surface of the hollow portion 61a, the half-shaped mold 61 is closed, and the mandrels 63, 63 are set in the mold 61. Thereafter, a method of injecting a molten resin into a cavity 65 formed between the mold 61 and the mandrels 63, 63 to integrally form an electro-fusion joint 50 in which the heating wire 55 is embedded is adopted. I was

[0004]

However, in the conventional electrofusion joint 50, as shown in FIG.
When the connected pipe P1 (P2) is inserted into the pipe 2 and the heating wire 54 is energized to melt the resin at the boundary between the joint body 51 and the connected pipe P1 (P2), the molten resin flows into the pipe socket 52. There is a case where it protrudes outward from a small gap S between the pipe and the connected pipe P1 (P2) to deteriorate the appearance and to lower the bonding strength.

Accordingly, the present invention provides an electric fusion joint in which the resin melted by the heating wire does not protrude from a gap between the pipe socket and the connected pipe, and a molding apparatus for producing the same. It is.

[0006]

In order to solve the above-mentioned problems, the present invention provides a pipe socket into which a pipe to be connected can be inserted, and embeds a heating wire in the inner peripheral surface of the pipe socket. In an electric fusion joint in which the resin at the boundary between the joint and the connected pipe is melted by heat generation and the two are fusion-spliced, a resin reservoir capable of accumulating the molten resin is formed on an inner peripheral surface of the pipe socket. did. If a resin reservoir is provided on the inner peripheral surface of the pipe receiving port, the resin melted by the heating of the heating wire can be stored here, so that the molten resin leaks out from the gap between the joint and the connected pipe, It can be prevented from protruding, and it is possible to avoid deterioration in appearance and reduction in bonding strength as in the conventional case.

[0007] The resin reservoir is formed, for example, by forming a plurality of grooves extending toward the opening of the pipe opening starting from the vicinity of the opening side end of a portion where the heating wire is buried in the inner peripheral surface of the pipe receiving opening at appropriate intervals in the circumferential direction. It is preferable to form them by providing them.

Further, the present invention provides a molding apparatus for manufacturing the above-mentioned electrofusion joint, which comprises a mold having a cavity for forming an outer structure of the electrofusion joint, and a mold capable of being divided. And a core forming an internal structure of the electrofusion joint by being inserted into the inside, and a heating wire is wound around an outer peripheral surface of the core and set in a mold, and between the mold and the core. In a molding apparatus for integrally molding an electric fusion joint in which a heating wire is embedded by injecting a molten resin into the formed cavity, a resin reservoir forming portion is formed on an outer peripheral surface of a core, and the resin reservoir forming portion is formed. A configuration in which a heating wire is wound around the tip in the axial direction is proposed.

In such a molding apparatus, the resin reservoir forming portion includes a plurality of ridges extending from the axially intermediate portion of the outer peripheral surface of the core to the base end side in the axial direction at appropriate intervals in the circumferential direction. It is preferable to provide and form. By forming the resin reservoir forming portion in this way, not only the above-described resin reservoir portion can be formed on the inner peripheral surface of the pipe receiving port, but also the heating wire wound by the starting end portions of the plurality of ridges is locked. A flange portion can be formed, and the displacement of the heating wire can be prevented.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on examples.

An electric fusion joint 1 according to one embodiment of the present invention.
As shown in FIG. 1, pipe receiving ports 3, 3 through which connected pipes P 1, P 2 can be fitted are provided at both ends of a straight tubular joint body 2,
A step portion (stopper) 4 is provided at each of the inner ends of the pipe sockets 3,
4 and a small-diameter portion 5 is provided between
Terminal plugs 6 are provided on the outer peripheral surface of the joint body 1 near both ends in the pipe axis direction, respectively. A heating wire 8 is spirally embedded in the back of the resin reservoir 7, and both ends of the heating wire 8 are connected to the terminal plugs 6, 6.

In the present embodiment, the resin reservoir 7 is provided as shown in FIGS.
As shown in the figure, the opening of the heating wire 8 on the inner peripheral surface of the tube socket 3 (heating wire buried portion 9) is formed at the opening side end of the heating wire 8 as a starting point. A plurality of grooves 7a of an appropriate length extending toward the opening side are formed at appropriate intervals in the circumferential direction. The shape of the resin reservoir 7 is
If an appropriate amount of resin can be stored, it can be formed into an appropriate shape and an appropriate size. However, in consideration of positioning, formability, amount of accumulation, and the like when the heating wire 8 is wound as described later, The starting point of the plurality of grooves 7a is
It is preferable to form them in the vicinity of the opening-side end of the same. In the case of this example, the starting point of the resin reservoir 7 is formed obliquely so as to be close to the opening side end of the heating wire buried portion 9. What is necessary is just to form it near the opening side end part of the heat ray burying part 9 as a starting point. Further, in this example, the resin reservoir 7 is formed up to the opening end of the pipe receiving port 3, but it may be formed up to a portion inside the opening end.

The step 4 functions as a stopper for abutting and positioning the ends of the connected pipes P1 and P2, but at the same time, does not obstruct the flow in the connected pipes P1 and P2. , The step of the step portion 4 is connected pipe P1,
It is preferable to form it substantially in the same manner as the thickness of P2. In other words, it is preferable that the inner diameter of the small diameter portion 5 and the inner diameters of the connected pipes P1 and P2 are substantially the same.

The terminal plug portion 6 has a cylindrical boss 6a protruding from the outer peripheral surface of the joint body 2, a terminal pin 6b is buried inside the boss 6a, and the terminal pin 6b
The heating wire 8 is electrically connected to the base end of the heating device.
The shape and structure of the terminal plug 6 can be arbitrarily formed.

According to the electric fusion joint 1 having the above structure, the connected pipes P1, P2 are inserted into the pipe receiving ports 3, 3, respectively, and the heating wire 8 is energized through the terminal plugs 6, 6. Then, the joint body 2 and the connected pipe P
By melting the resin at the boundary between P1 and P2, the two (the joint body 2 and the connected pipe P1 and the joint body 2 and the connected pipe P2) can be fusion-spliced. In addition, at this time, even if a part of the molten resin protrudes outside from the fused portion, it can be stored in the resin storage portion 7, so that the P1. The molten resin does not protrude from the gap with P2, and appearance and bonding strength can be ensured.

As the resin of the electrofusion joint 1, a thermoplastic resin can be used as in the case of the conventional electrofusion joint, and examples thereof include polypropylene, polyethylene, vinyl chloride, and polybutene resin. it can.
However, it is not limited to these resins. Also,
As the heating wire 8, it is preferable to use a coated heating wire coated with a resin. Not only can short-circuiting of the heating wire 8 be prevented, but also by pressing an electric iron or the like against the outer peripheral surface of the heating wire 8 immediately after winding, melting the coating resin and fusing between the adjacent coating heating wires and winding Can be prevented from loosening. In addition, as the coating resin, polyethylene,
Thermoplastic resins such as polypropylene, polyvinyl chloride and polybutene resin can be used.
It is preferable to use the same resin as above. Also, for the heating wire, for example, nichrome wire, copper nickel alloy wire,
It is possible to use a general resistance wire such as a manganese-nickel alloy wire, a chromel wire, and an iron-chrome wire.

A forming apparatus 21 shown in FIG. 3 is a forming apparatus for manufacturing the above-mentioned electrofusion joint 1, and is an example of a forming apparatus according to an embodiment of the present invention.

The molding apparatus 21 is provided with the electric fusion joint 1 described above.
And a vertically splittable mold 23 having a hollow portion 22 substantially corresponding to the external structure (outline of the joint body 2 and the terminal plug portions 6, 6), and the electrofusion joint 1 inserted into the mold 23. Are provided with a pair of mandrels 24 and 25 as contours substantially corresponding to the internal structure of the pipe (the contours of the pipe socket 3, the stepped portion 4, the small diameter portion 5, and the resin reservoir 7).

The mold 23 includes a fixed mold 26 and a movable mold 27. The fixed mold 26 is provided with a gate (not shown) for injecting a molten resin, and the movable mold 27 has an inner peripheral surface of the cavity 22. There is provided a locking recess 29 into which the terminal holding mold 28 can be fitted.

The mandrels 24 and 25 form fitting portions (not shown) that can be fitted to each other on the distal end surfaces of the cylindrical bodies, and one of the mandrel 24 (25) corresponds to the small diameter portion 5. The resin reservoir is formed in an outer portion from the axial middle portion of the outer peripheral surface of the cylindrical body, that is, an outer portion (a base end side portion of each mandrel) of a portion around which the heating wire 8 is wound (heating wire winding portion 31). Forming portions 32, 32 are formed.

In this embodiment, as shown in FIGS. 3 and 4, the resin reservoir forming portion 32 has a smaller diameter at the distal end side than at the axially intermediate portion of the cylindrical body inserted into the hollow portion 22 than at the base end side. age,
By forming the boundary between the small-diameter portion and the large-diameter portion so as to enter and exit in an uneven shape when viewed from above, a plurality of convex portions 32a are provided at appropriate intervals in the circumferential direction at the axially intermediate portion of the cylindrical body, The resin reservoir forming portion 32 is formed by the plurality of convex portions 32a. At this time, each protruding portion 32a has an appropriate width and extends appropriately to the base end side in the axial direction with the outer edge of the heating wire winding portion 31 (a base end edge as viewed from each mandrel) as a starting point. It has a shape. However, the resin reservoir forming portion 32 can be arbitrarily formed as long as the resin reservoir 7 can be molded.

The pair of mandrels 24, 2
5, the tips are fitted to each other, and the heating wire 8 is spirally wound on the outer peripheral surface of one of the mandrels 24 (25) from the starting edge of the resin reservoir forming part 32 to the tip. The heating wire 8 is wound spirally again on the outer peripheral surface of the other mandrel 25 (24) to the starting edge of the resin reservoir forming portion 32. Is connected to the terminal pin 6b. Next, the locking recess 2
After the terminal holding mold 28 is mounted on the mold 9, the movable mold 27 is lowered to close the mold 23, and the mandrel 2 is inserted into the mold 23.
Set 4 and 25. Thereafter, the molten resin is injected into the cavity 33 formed between the mold 23 and the mandrels 24 and 25, and after the resin is solidified, the movable mold 27 is raised and the mold is opened to form the electrofusion joint 1. Can be taken out.

According to the molding apparatus 21 having the above configuration,
Not only can the resin reservoir portion 7 be formed by the resin reservoir forming portion 32, but also a flange portion that locks the heating wire 8 wound by the starting point ends of the plurality of ridges 32a can be formed. 8 can be prevented from shifting.

In this embodiment, a straight tubular socket joint has been described.
The present invention is applicable to various types of joints such as a socket shape, an elbow shape, a saddle shape, and a different diameter joint shape.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an electric fusion joint according to one embodiment of the present invention.

FIG. 2 is a II sectional view showing a sectional structure of a pipe socket in the electrofusion joint of FIG. 1;

FIG. 3 is a longitudinal sectional view showing an example of an apparatus for forming an electro-fusion joint according to one embodiment of the present invention.

4 shows an example of a bending process using a bending device showing a cross-sectional structure of a core in the molding device of FIG. 3 II-I
It is I sectional drawing.

FIG. 5 is a longitudinal sectional view showing an example of a conventional electric fusion joint.

FIG. 6 is a longitudinal sectional view showing an example of a conventional electrofusion joint forming apparatus.

7 is a longitudinal sectional view showing a connection state when two pipes are connected using the electrofusion joint of FIG. 5;

[Explanation of symbols]

 P1, P2 Connected pipe 1 Electric fusion joint 2 Joint main body 3 Pipe socket 4 Step part (stopper) 5 Small diameter part 6 Terminal plug part 7 Resin reservoir part 7a Groove part 8 Heating wire 9 Heating wire burying part 21 Molding device 22 Cavity Part 23 Mold 24, 25 Mandrel (core) 26 Fixed type 27 Movable type 28 Terminal holding type 29 Locking concave part 30 Small diameter part 31 Heating wire winding part 32 Resin reservoir forming part 32a Protrusions 33 Cavity

Claims (4)

[Claims] 1. A pipe socket into which a pipe to be connected can be inserted, a heating wire is buried in an inner peripheral surface of the pipe socket, and a resin at a boundary portion between the joint and the pipe to be connected is melted by heat generated by the heating wire. A fusion splicing joint for fusing the two together by forming a resin reservoir on the inner peripheral surface of the tube socket, the resin reservoir being capable of accumulating a molten resin. 2. The resin reservoir has a plurality of grooves extending from the vicinity of the opening side end of a portion where the heating wire is buried on the inner peripheral surface of the tube opening to the opening side of the tube opening at appropriate intervals in the circumferential direction. The electrofusion joint according to claim 1, wherein the joint is provided. 3. A dividable mold having a cavity forming an outer structure of the electro-fusion joint, and a core inserted into the mold to form an inner structure of the electro-fusion joint. The heating wire is wound around the outer peripheral surface of the core, set in a mold, and a molten resin is injected into a cavity formed between the mold and the core, so that the heating wire is embedded therein. In a molding apparatus for integrally molding a splice joint, an electric fusion joint having a configuration in which a resin reservoir forming portion is formed on an outer peripheral surface of a core, and a heating wire is wound around an axial front end side of the resin reservoir forming portion. Molding equipment. 4. The resin reservoir forming portion is formed by providing a plurality of ridges extending from the axial middle portion of the outer peripheral surface of the core in the axial direction to the base end side at appropriate intervals in the circumferential direction. The apparatus for forming an electro-fusion joint according to claim 3, wherein: