JPH02253093A - Electrofusion joint - Google Patents

Abstract

PURPOSE:To uniformly fuse the whole body by disposing a heating wire in a thermoplastic resin layer formed to make contact with the body to be connected outer circumferential part in such a manner that the distance from the resin layer bore part is large in the center part and small in the both end parts. CONSTITUTION:In an electrofusion joint 1, an uncross-linked polyolefin layer 2b having a heating wire 3 provided therein is formed on the inner both sides of a tubular cross-linked polyolefin layer 2a of a joint body in such a manner as to make contact with bodies 4, 5 to be connected. The heating wire 3 is disposed in such a manner that the distance from the bore surface of the layer 2b is large in the center part and small in the both end parts. The bodies 4, 5 to be connected such as polyolefin tubes are inserted from the both ends of the joint body 1 and butted to each other in a butt part 7, and the heating wire 3 is energized to melt the uncross-linked polyolefin layer 2b, which is then fused to the bodies 4, 5 to be connected and integrated therewith. Hence, the whole body can be uniformly fused to improve sealing property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrofusion joint for joining objects such as polyolefin pipes, particularly hot water conduits.

[Conventional technology]

Conventionally, as an electrofusion joint for joining objects to be joined such as resin pipes used as conduits for water supply, hot water supply, or gas, there is a known electrofusion joint as shown in FIG. Special Public Service 1986-
No. 40993).

In the figure, reference numeral 1 denotes an electrofusion joint, which is composed of a tubular resin layer 2 made of thermoplastic resin forming a joint body, and a coil-shaped heating wire 3 buried inside the resin layer 2. This heating wire 3 is arranged at a joining part 6 into which an object 4.5 to be joined, such as a resin pipe, is inserted.

Such an electrofusion joint 1 has a resin layer 2
When the object 4.5 to be welded is inserted into the object 4.5, the vicinity of the abutting portion 7 is covered, and the heating wire 3 is energized, the resin layer 2 made of thermoplastic resin melts and the object 4.5 is joined to the object 4.5. Fused together. Thereby, the objects to be welded 4.5 can be welded.

However, such a conventional electrofusion joint 1 has a coil-shaped heating wire 3 embedded in a resin layer 2.
Since the shape and pitch of the rosin are uniform, when the heating wire 3 is energized, the temperature distribution of the molten rosin becomes uneven.
The temperature near the center of the heating wire 3 becomes high, and the temperature near both ends becomes lower than that near the center, and in some cases, uneven melting occurs, such as not melting. As a result, there are problems such as unevenness in the fusion strength between the objects 4.5 and the resin layer 2, resulting in a decrease in pressure resistance, sealing properties, etc. during use, and a long-term deterioration in performance.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the above-mentioned problems by making the temperature distribution of the resin layer uniform during fusion, making it possible to perform even and uniform fusion, and improving performance such as pressure resistance and sealing properties. An object of the present invention is to provide an electrofusion joint that can maintain high performance over a long period of time.

[Means to solve the problem]

The present invention includes a resin layer made of a thermoplastic resin formed so as to be in contact with the outer peripheral portion of the object to be joined, and a heating wire provided on the resin layer, and the heating wire extends from the inner diameter portion of the resin layer. This is an electrofusion joint characterized in that the distance between the resin layers is large at the center of the resin layer and small at both ends.

In the present invention, the rosin layer made of thermoplastic resin may constitute the entire joint, or may constitute a part thereof. For example, the resin layer may be formed on the parts that come into contact with both objects to be joined, but it may be formed only on the part that comes into contact with one of the objects to be joined, and the resin layer may be formed on the part that comes into contact with the other object, such as a screw, etc. They may be joined by other joining members having mechanical joining means. Further, the resin layer may be formed only on the inner circumferential portion in contact with the objects to be joined, and another resin layer having strength may be laminated on the outer circumferential portion. The resin layer and the object to be joined are preferably made of the same type of resin or resins that are compatible with each other.

[For production]

In the electrofusion joint of the present invention, the object to be joined is inserted inside a resin layer made of thermoplastic resin, and when the heating wire provided in the resin layer is energized to melt the resin layer, the heating wire is connected to the resin layer. Since the distance from the inner diameter of the resin layer is larger at the center of the resin layer and smaller at both ends, the amount of heat supplied to the inner diameter of the resin layer in contact with the object The temperature distribution in the resin layer at the joint becomes uniform by increasing the temperature near both ends, where the influence of the low-temperature atmosphere is large, and decreasing the temperature at the center.

As a result, the resin layer is melted evenly and uniformly, and the entire resin layer at the joint portion is evenly and uniformly fused to the objects to be joined, thereby joining the objects to be joined. This maintains high pressure resistance, sealability, etc.

〔Example〕

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

FIG. 1 is a front view showing a cross section of the right half of the electrofusion joint of the embodiment, which is symmetrically constructed. In the figure, 1 is an electrofusion joint, which includes a tubular crosslinked polyolefin layer 2a forming the joint body;
The object to be joined 4.5 inside this crosslinked polyolefin layer 2a
A non-crosslinked polyolefin layer 2b as a thermoplastic resin layer integrally formed with the crosslinked polyolefin layer 2a and a heating wire 3 provided in a coil shape inside this non-crosslinked polyolefin layer 2b are attached to the joint portion in contact with the crosslinked polyolefin layer 2a. have Further, the heating wire 3 is arranged at a position such that the distance from the inner diameter portion of the non-crosslinked polyolefin layer 2b is large at the center of the resin layer and small at both ends. The non-crosslinked polyolefin layer 2b is formed into a tubular shape so as to be in contact with the outer periphery of the objects 4.5 to be joined at the left and right joint portions 6.

The object to be joined 4.5 consists of a tube having a layer of thermoplastic resin such as polyethylene, and may be entirely made of a fusible thermoplastic resin, but if a heat-resistant material such as crosslinked polyolefin is used, the outer surface A material coated with a fusible thermoplastic resin is used.

The crosslinked polyolefin layer 2a has a tubular structure that covers the entire circumference near the abutting portion 7 of the objects 4.5 to be joined, and has a tubular structure that covers the entire circumference near the abutting portion 7 of the objects 4.5 to be joined. A non-crosslinked polyolefin layer 2b is laminated, and a heating wire 3 is provided therein.

The electrofusion joint 1 described above is formed by integrating a crosslinked polyolefin layer and a non-crosslinked polyolefin layer adjacent to each other. Since crosslinked polyolefin does not have fusion properties, even if crosslinked polyolefin and non-crosslinked polyolefin are formed by extrusion molding, injection molding, etc.,
Each layer is separated and not integrated, but when the uncrosslinked polyolefin and the non-crosslinked polyolefin are heat-molded and integrated, and the crosslinked polyolefin is then crosslinked, the crosslinked polyolefin and the non-crosslinked polyolefin are integrated. A laminate is obtained.

Crosslinked polyolefins have a three-dimensional structure due to intermolecular crosslinking of polyolefins, and in addition to those crosslinked with crosslinking agents such as silane crosslinked polyolefins and divinylbenzene crosslinked polyolefins, they can also be crosslinked directly with organic peroxides, radiation, etc. good.

Non-crosslinked polyolefin is a polyolefin resin that does not have crosslinking properties and is generally used as a thermoplastic resin.

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

The electrofusion joint 1 described in ``1'' is produced by laminating and fixing the heating wire 3 embedded in the non-crosslinked polyolefin layer 2b with a crosslinkable polyolefin layer containing a crosslinking agent, a crosslinking aid, etc. in the polyolefin, and then It is manufactured by crosslinking a crosslinkable polyolefin and an inner layer to form a crosslinked polyolefin layer 2a.

The electrofusion joint 1 manufactured in this way is
A non-crosslinked polyolefin layer 2b is placed near the abutting portion 7 of the object 4.5 to be joined, such as a polyolefin tube.
5 and when electricity is applied to the heating wire 3, the non-crosslinked polyolefin layer 2b melts and is fused to and integrated with the object to be joined 4.5.

The heating wire 3 is placed in such a position that the distance from the inner diameter of the non-crosslinked polyolefin layer 2b is large at the center of the non-crosslinked polyolefin layer 2b and small at both ends, so that the distance between the heating wire 3 and the object to be joined 4.5 increases. The amount of heat supplied to the inner diameter portion of the non-crosslinked polyolefin layer 2b in contact with it is higher near both ends where the influence of the external low temperature atmosphere is large, and is lower at the center, which increases the temperature of the non-crosslinked polyolefin layer 2b in the joint portion 6. The distribution becomes uniform.

As a result, the bonded portion 6 of the non-crosslinked polyolefin M2b is melted evenly and uniformly, and the entire non-crosslinked polyolefin layer 2b is evenly and uniformly fused to the object 4.5 to be bonded.
．． Join with 5.

Since the tubular crosslinked polyolefin layer 2a forming the joint body provides heat resistance strength, the above-mentioned Elec 1-Rof Fusion joint has excellent shape retention even when used for joining hot water pipes and the like. On the other hand, since the non-crosslinked polyolefin layer 2b and the crosslinked polyolefin layer 2a are uniformly fused and integrated with the object 4.5 to be joined, the sealing property is excellent. This maintains high pressure resistance, sealability, etc.

FIG. 2 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
, 5a and non-crosslinked polyolefin layers 4b, 5b.

In the above embodiment, the non-crosslinked polyolefin layer 2b as a thermoplastic resin layer is laminated with the crosslinked polyolefin layer 2a, but as shown in FIG. A joint 1 may also be formed. In addition, an example was shown in which the non-crosslinked polyolefin layer 2b and the heating wire 3 were provided on both sides so that the joint 1 was symmetrical, but one side, for example, the right side in FIG. A connecting member having a connecting portion such as a screw may be attached to the connecting member to mechanically connect it to the object to be joined.

〔Effect of the invention〕

According to the present invention, since the heating wire is provided in the resin layer at a position such that the distance from the inner diameter portion thereof is large at the center of the resin layer and small at both ends, the temperature distribution of the resin layer is This results in an electrofusion joint that can maintain performance such as pressure resistance and sealing properties over a long period of time by uniformly fusion bonding the whole body.

[Brief explanation of drawings]

FIGS. 1 and 2 are front views showing a part of another embodiment in cross section, and FIG. 3 is a front view showing a part of a conventional electrofusion joint in cross section. In each figure, the same reference numerals indicate the same or equivalent parts, 1 is an Elec 1-Rof Fusion joint, 2 is a resin layer, 2a is a crosslinked polyolefin layer, 2b is a non-crosslinked polyolefin layer, 3
is a heating wire, 4.5 is an object to be joined, and 6 is a joint portion. Agent Patent Attorney Sei Yanagihara

Claims (1)

[Claims] (1) A resin layer made of thermoplastic resin formed so as to be in contact with the outer periphery of the object to be joined, and a heating wire provided on this resin layer, the heating wire being connected from the inner diameter of the resin layer. An electrofusion joint characterized in that the distance is large at the center of the resin layer and small at both ends.