JP2545971B2 - Electrofusion fittings - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrofusion joint for joining an article to be joined such as a polyolefin pipe, particularly a conduit for hot water.

[Conventional technology]

BACKGROUND ART Heretofore, as an electrofusion joint for joining objects to be joined such as a resin pipe used as a conduit for water supply, hot water supply, or gas supply, the one shown in FIG. 5 has been known (for example, Japanese Patent Laid-Open No. 61- 130695, Japanese Examined Sho 63-4099
No. 3).

In the figure, reference numeral 1 denotes an electrofusion joint, which is a tubular resin layer 2 made of a thermoplastic resin that forms a joint body,
The coil-shaped heating wire 3 is embedded inside the resin layer 2. The heating wire 3 is a member to be joined 4, 5 such as a resin pipe.
Is arranged at the joint portion 6 into which is inserted.

In such an electrofusion joint 1, when the objects to be joined 4 and 5 to be joined to the resin layer 2 are inserted and the vicinity of the butted portion 7 is covered and the heating wire 3 is energized, a resin layer made of a thermoplastic resin is formed. 2 is melted and integrally fused with the objects to be joined 4, 5. Thereby, the objects to be joined 4, 5 can be joined.

However, in such a conventional electrofusion joint 1, since the shape and pitch of the coil-shaped heating wire 3 embedded in the resin layer 2 are formed uniformly, the temperature distribution of the molten resin when the heating wire 3 is energized Becomes non-uniform, the temperature becomes higher near the center of the heating wire 3, and the temperature near both ends becomes lower than that near the center, and in some cases uneven melting occurs such as not melting. Therefore, there is a problem in that the fusion force between the objects to be joined 4 and 5 and the resin layer 2 becomes uneven, and the pressure resistance during use, the sealing property, etc. are reduced, causing a long-term deterioration in performance.

[Problems to be Solved by the Invention]

The object of the present invention is to solve the above problems, to make the temperature distribution of the resin layer at the time of fusion uniform, and to perform uniform fusion without unevenness, and to improve performance such as pressure resistance and sealability. An object of the present invention is to provide an electrofusion joint that can be maintained at a high level for a long period of time.

[Means for solving the problem]

The present invention is a resin layer made of a thermoplastic resin formed so as to be in contact with the outer peripheral portion of the article to be joined, and the inside of the resin layer,
The heating wire is provided on the outer surface or the inner surface, and the heating wire is arranged at a pitch such that the central portion of the resin layer is rough and both ends are dense. It is an electrofusion joint.

In the present invention, the resin layer made of a thermoplastic resin may form the whole joint, or may form a part thereof. For example, the resin layer may be formed in a portion in contact with both of the joined objects to be joined, but formed only in a portion in contact with one of the joined objects,
The other member to be joined may be joined by another joining member having mechanical joining means such as a screw. Further, the resin layer may be formed only on the inner peripheral portion in contact with the object to be bonded, and another resin layer having strength may be laminated on the outer peripheral portion. The resin layer and the article to be joined are preferably made of the same type of resin or a resin having compatibility with each other.

[Work]

The electrofusion joint of the present invention has a resin layer formed by inserting an object to be joined inside a resin layer made of a thermoplastic resin, and energizing a heating wire provided inside the resin layer, on the outer surface, or on the inner surface. When melted, the heating wires are arranged at a pitch such that the center part of the resin layer becomes rough and both ends become dense, so the amount of heat supplied to the resin near both ends, which is greatly affected by the external low temperature atmosphere. Is increased, and the temperature distribution of the resin layer at the joint becomes uniform.

As a result, the resin layer of the joint portion is evenly and uniformly melted, and the entire resin layer of the joint portion is evenly and evenly fused to the body to be joined, so that the body to be joined is joined. As a result, the pressure resistance and sealing performance are maintained in a high level.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 are front views showing the right half of an electrofusion joint of another embodiment in a cross section, and are constructed symmetrically. In the figure, reference numeral 1 denotes an electrofusion joint, which is a tubular cross-linked polyolefin layer 2a forming a joint body and a cross-linked polyolefin layer at a position inside the cross-linked polyolefin layer 2a, which is to be joined.
Non-crosslinked polyolefin layer 2b as a thermoplastic resin layer integrally formed with 2a, and this non-crosslinked polyolefin layer 2b
And a heating wire 3 provided in a coil shape on the inside, the outside surface, or the inside surface. Heating wire 3 is a non-crosslinked polyolefin layer
2b is arranged at a pitch such that the central part becomes rough and both ends become dense. The non-crosslinked polyolefin layer 2b is formed in a tubular shape so as to contact the outer peripheries of the objects to be joined 4, 5 of the left and right joints 6.

The objects to be joined 4 and 5 are made of a tube having a thermoplastic resin layer such as polyethylene, and may be entirely made of a fusible thermoplastic resin. However, when a heat resistant material such as crosslinked polyolefin is used, the outer surface What is coated with a fusible thermoplastic resin is used.

The crosslinked polyolefin layer 2a has a tubular structure that covers the vicinity of the abutting portions 7 of the objects to be joined 4, 5 over the entire circumference thereof, and is provided on the inner circumference of the joining portion 6 corresponding to the objects to be joined 4, 5 on both sides in the longitudinal direction. The cross-linked polyolefin layer 2b is laminated, and the heating wire 3 is embedded therein in FIG. 1, and is provided on the outer surface thereof in FIG. 2 and on the inner surface in FIG.

The electrofusion joint 1 described above is formed by integrating a crosslinked polyolefin layer 2a and a non-crosslinked polyolefin layer 2b adjacent to each other. Since the crosslinked polyolefin has no fusibility, even if the crosslinked polyolefin and the non-crosslinked polyolefin are molded by extrusion molding, injection molding, etc., the respective layers are not separated and integrated, but the uncrosslinked crosslinkable polyolefin is not crosslinked. When the polyolefin and the non-crosslinked polyolefin are heat-molded and integrated, and then the crosslinkable polyolefin is crosslinked, a laminate in which the crosslinked polyolefin and the non-crosslinked polyolefin are integrated is obtained.

Crosslinked polyolefin has a three-dimensional structure due to intermolecular crosslinking of polyolefin, and may be crosslinked with a crosslinking agent such as silane crosslinked polyolefin or divinylbenzene crosslinked polyolefin, or may be directly crosslinked with organic peroxide, radiation or the like. Good.

Non-crosslinked polyolefin is a non-crosslinkable polyolefin resin generally used as a thermoplastic resin.

Examples of the polyolefin include homo- or copolymers of α-olefin having 2 to 20 carbon atoms, preferably 2 to 12 carbon atoms. Preferred α-olefins include ethylene, propylene, butene-1, 4-methylpentene-1 and the like.

The electrofusion joint 1 described above has a structure in which the heating wire 3 is embedded or wound in the non-crosslinked polyolefin layer 2b such that the central part of the non-crosslinked polyolefin layer 2b becomes rough and both ends become dense. To the cross-linking agent,
It is produced by laminating and integrating with a crosslinked polyolefin layer containing a crosslinking aid and the like, and then crosslinking the above crosslinked polyolefin layer to form a crosslinked polyolefin layer 2a.

Electrofusion joint 1 thus manufactured
Is attached near the abutting portion 7 of the joined bodies 4, 5 such as a polyolefin tube so that the non-crosslinked polyolefin layer 2b is in contact with the joined bodies 4, 5, and when the heating wire 3 is energized,
The non-crosslinked polyolefin layer 2b is melted and fused to the objects to be joined 4, 5 to be integrated.

Since the heating wires 3 are arranged at such a pitch that the central portion of the non-crosslinked polyolefin layer 2b becomes rough and the both ends become dense, the heating wires 3 are supplied to the resin in the vicinity of both ends which is greatly affected by the low temperature outside atmosphere. A large amount of heat is applied, and the temperature distribution of the non-crosslinked polyolefin layer 2b at the joint becomes uniform.

As a result, the non-crosslinked polyolefin layer 2b is uniformly melted, and the whole non-crosslinked polyolefin layer 2b is bonded to the article 4,
5 and 5 are evenly and uniformly fused to bond the objects to be bonded 4, 5.

In the electrofusion joint 1 described above, the tubular cross-linked polyolefin layer 2a forming the joint body bears the heat resistance strength, so that it is excellent in shape retention even when used for joining hot water supply pipes and the like. On the other hand, since the non-crosslinked polyolefin layer 2b and the crosslinked polyolefin layer 2a are integrated with each other, they are uniformly fused and integrated with the articles 4 and 5 to be joined, so that the sealability is excellent. As a result, the pressure resistance and sealing performance are maintained in a high level.

FIG. 4 is a front view showing a cross section of the upper half of another embodiment. In this embodiment, the non-crosslinked polyolefin layer 2b is continuously and integrally provided, and the crosslinked polyolefin layer 4a,
The objects to be joined 4, 5 composed of 5a and the non-crosslinked polyolefin layers 4b, 5b are joined together.

In the above example, the non-crosslinked polyolefin layer 2b as the thermoplastic resin layer is laminated with the crosslinked polyolefin layer 2a, but as shown in FIG. The joint 1 may be formed. Further, the joint 1 is shown as an example in which the non-crosslinked polyolefin layer 2b and the heating wire 3 are provided on both sides so that the joint 1 is symmetrical, but one side, for example, the right side of FIGS.
A connecting member having a connecting portion such as a screw may be attached to the opposite side, for example, the left side to mechanically join the articles to be joined 4, 5.

〔The invention's effect〕

According to the present invention, the heating wire is provided on the inside, the outer surface, or the inner surface of the resin layer at a pitch such that the central portion of the resin layer is rough and the both ends are dense. Temperature distribution is made uniform and the whole is fused evenly, pressure resistance,
It is possible to obtain an electrofusion joint capable of maintaining high performance such as sealing property for a long period of time.

[Brief description of drawings]

1 to 4 are front views showing a part of another embodiment in a cross section, and FIG. 5 is a front view showing a part of a conventional electrofusion joint in a cross section. In each figure, the same reference numerals indicate the same or corresponding parts, 1 is an electrofusion joint, 2 is a resin layer, 2a is a crosslinked polyolefin layer, 2b is a noncrosslinked polyolefin layer, 3 is a heating wire, and 4 and 5 are objects to be joined. , 6 are joints.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akio Nakashiba 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka, Osaka Gas Co., Ltd. (72) Fumio Hase 6 Waki, Waki-cho, Kaku-gun, Yamaguchi Prefecture Chome 1-2 Mitsui Petrochemical Co., Ltd. (72) Inventor Kazunori Mito 6 1-2 Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture Mitsui Petrochemical Co., Ltd. (72) Inventor Toshio Shiabuchi Osaka Prefecture Shinwa Sangyo Co., Ltd. 2-10-16 Minamikagaya, Suminoe-ku, Osaka (72) Inventor Mikio Nakaoka 2-10-16 Minamikagaya, Suminoe-ku, Osaka-shi, Osaka

Claims (1)

(57) [Claims] 1. A resin layer made of a thermoplastic resin formed so as to contact an outer peripheral portion of an article to be joined, and the inside of the resin layer,
The heating wire is provided on the outer surface or the inner surface, and the heating wire is arranged at a pitch such that the central portion of the resin layer is rough and both ends are dense. Electrofusion fitting.