JPH10311481A - Electrofusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the fusing condition in an adequate condition, by controlling the projecting amount of a display pin in an adequate scope, as well as to form the display pin integrally with a joint main body. SOLUTION: An electric heating wire 4 is buried near the joint 9 of jointed bodies 5 and 6 of a resin layer 3 consisting of a thermoplastic resin which forms a joint main body 2 fusing by contacting to the outer peripheries of the jointed bodies 5 and 6, a recess part 8 is formed to open from the resin layer 3 near the burying part of the electric heating wire 4 to the outer surface side, a hood 13 is formed to the opening 11 in order to make the opening area of the opening 11 smaller than the cross-sectional area of the middle part 12, and a display pin 7 projecting integral from the base 14 of the recess part 8 toward the opening 11 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusion joint for completely joining thermoplastic articles such as polyolefin pipes by fusion.

[0002]

2. Description of the Related Art Conventionally, an electrofusion joint for joining a thermoplastic resin joint such as a resin pipe used as a conduit for water supply, hot water supply or gas supply by fusion has been used as an electrofusion joint. In some cases, a display member indicating a fused state is protruded to the outer surface side in order to make it possible to confirm the state.

As such an electrofusion joint, there has been proposed an electrofusion joint in which a display member made of another member is inserted into a concave portion formed in the electrofusion joint, and is projected from the surface by volume expansion at the time of fusion. (For example, JP-A-61-62669). However, in such an electrofusion joint, it is difficult to insert a display member made of a separate member so as not to fall off from the joint body, which increases the cost, and when the resin layer is deformed, the protrusion of the display portion is hindered. However, there is a problem that accurate display cannot be performed.

[0004] In order to improve such a point, there has been proposed one in which a part of a joint body is projected as a display unit. FIG. 3 is a front view showing a cross section of a part of such a conventional electrofusion joint. In FIG. 3, reference numeral 1 denotes an electrofusion joint;
A heating wire 4 inside a resin layer 3 made of a thermoplastic resin forming
Are buried, and a display portion pin 7 indicating the fused state of the objects 5 and 6 is formed in the concave portion 8.

[0005] The heating wire 4 is connected to an object 5 such as a resin pipe,
6 is arranged at the joint 9 to be inserted, and a columnar display pin 7 protrudes from the vicinity of the joint 9. The recess 8 is formed in a cylindrical shape so as to surround the display pin 7, and is formed so as to open from the vicinity of the joint 9 toward the outer surface of the joint body.

In the electrofusion joint 1 having such a structure, the objects 5 and 6 are inserted into the resin layer 3 to cover the vicinity of the butted portion 10 and when the heating wire 4 is energized, the thermoplastic material near the joined portion 9 is formed. The resin layer 3 made of resin is melted and fused with the objects 5 and 6, and the volume expands to raise the display pin 7 and protrude from the recess 8. The completion of the fusion is indicated by the projection of the display pin 7.

However, in the conventional electrofusion joint 1 as described above, it is difficult to control the amount of protrusion of the display pin 7, and when the amount of protrusion of the display pin 7 increases, a vacuum bubble is generated, or There is a problem that the heating wire is short-circuited.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display pin that can be integrally formed with a joint body, and that the amount of protrusion is controlled within an appropriate range to control the fusion state to an appropriate state. To obtain a possible electrofusion joint.

[0009]

SUMMARY OF THE INVENTION The present invention relates to the following electrofusion joint. (1) A joint main body formed so as to be in contact with the outer peripheral portion of the joined body, a resin layer made of a thermoplastic resin forming the joint main body, and a resin layer buried near a joint of the joined body with the joined body. The heating wire and the resin layer near the buried portion of the heating wire are formed so as to open toward the outer surface side, and are laid on the opening so that the opening area of the opening is smaller than the cross-sectional area of the intermediate portion. An electrofusion joint comprising: a recess formed with a portion; and a display pin integrally projecting from a base of the recess toward an opening. (2) The electrofusion joint according to (1), wherein the area of the base of the concave portion is smaller than the cross-sectional area of the intermediate portion.

In the present invention, the thermoplastic resin forming the joint body can be exemplified by polyolefin, but may be polyvinyl chloride or other thermoplastic resin. The same applies to the resin forming the joined body. Examples of the polyolefin include homo- or copolymers of α-olefins having 2 to 20, preferably 2 to 12 carbon atoms. Preferred α-
As the olefin, ethylene, propylene, butene
1,4-methylpentene-1 and the like.

The joint body is formed of these resins so as to be in contact with the outer peripheral portion of the joined body. The object is water supply,
Although it is a pipe for hot water supply or gas, a molded article of another shape may be used. The joint main body is formed in a tubular (sleeve-like) shape by burying a heating wire near the joining portion so as to cover the outer peripheral portions of these joined objects.

The concave portion is formed so as to open from the resin layer near the buried portion of the heating wire toward the outer surface side. The concave portion is formed so that the opening area of the opening is smaller than the cross-sectional area of the intermediate portion. An eave portion protruding toward the center of the opening is formed. It is preferable that the base of the concave portion is also formed to have an area smaller than the cross-sectional area of the intermediate portion.

The display pin is formed so as to protrude from the base of the recess toward the opening. It is preferable that the shape of the display pin is cylindrical and the shape of the tip is rounded, and the protruding position of the tip is preferably substantially coincident with the opening, but is not limited thereto.

The above-described electrofusion joint is manufactured by integrally molding a thermoplastic resin by injection molding or the like so as to embed a heating wire. The recess is formed in an undercut shape using, for example, a split mold.

The electrofusion joint thus manufactured is attached to a joint of a member to be joined such as a thermoplastic resin tube so that the joint of the resin layer is in contact with the member to be joined.
When the heating wire is energized, the resin layer made of a thermoplastic resin is melted and integrally fused to the object to be joined. In this fusion, the resin layer in the vicinity melts and expands in volume due to the amount of heat supplied from the heating wire, and the pressure of the resin layer increases. As a result, the display pin protrudes from the opening to display the time when the fusion is completed.

At this time, the base of the recess rises so as to fill the inside of the recess. However, the rise is stopped by the eaves formed around the opening, and the protrusion protrudes at a position where the base substantially coincides with the eaves. Stops. For this reason, the amount of protrusion of the display pin is controlled within a substantially constant range, whereby there is no excessive flow of the molten resin or insufficient heating, and the fusion state is controlled to an appropriate state.

[0017]

As described above, according to the present invention, the eaves are formed so that the opening area of the concave portion opening from the resin layer near the heating wire toward the outer surface side is smaller than the cross-sectional area of the middle part. In addition, since the display pins are provided integrally projecting from the base toward the opening side, the amount of protrusion of the display pins can be controlled within a substantially constant range. Thus, an electrofusion joint that can control the fused state to an appropriate state can be obtained.

[0018]

Embodiments of the present invention will be described below. FIG. 1 is a front view showing a cross section of a part of the electrofusion joint according to the embodiment, and FIGS. 2A and 2B are explanatory views of its operation.

In FIGS. 1 and 2, reference numeral 1 denotes an electrofusion joint, in which a heating wire 4 is embedded in a resin layer 3 made of a thermoplastic resin forming a joint main body 2, and the joined bodies 5, 6 are fused. A display pin 7 indicating a state is formed integrally with the resin layer 3 in the recess 8. The heating wire 4 is arranged in the vicinity of the joint 9 into which the objects 5 and 6 such as resin pipes are inserted.

The recess 8 is formed so as to open from the resin layer near the buried portion of the heating wire 4 to the outer surface side, so that the opening area of the opening 11 is smaller than the cross-sectional area of the intermediate portion 12. In addition, an eave portion 13 is formed in the opening portion 11. In this embodiment, the recess 8 is formed in an elliptical shape,
The area of the base 14 is also smaller than the cross-sectional area of the middle part. If the diameter of the opening 11 is a and the diameter of the intermediate part 12 is b, a <b. a = 2 to 5 mm, b = a
+ (0.2 to 0.5 mm) is preferred.

The display pin 7 protrudes from the base 14 of the recess 8 toward the opening 11, and its tip reaches a position near the opening 11 and lower than the opening 11. Display pin 7
Is preferably about 5 to 10 mm.

The above-mentioned electrofusion joint 1 is manufactured by integrally molding the heating wire 4 by injection molding of a thermoplastic resin or the like so as to embed the heating wire 4 therein. The recess 8 is formed in an undercut shape using a split mold or the like.

In the electrofusion joint 1 manufactured in this manner, the objects 5 and 6 are inserted into the resin layer 3 to cover the vicinity of the butted portion 10, and when the heating wire 4 is energized, the thermoplastic resin near the joined portion 9 is formed. The resin layer 3 is melted and fused with the objects 5 and 6, and the fused portion 15 expands in volume, the display pin 7 is lifted up and protrudes from the opening 11 of the recess 8. The completion of the fusion is indicated by the projection of the display pin 7.

At this time, the base 14 of the concave portion 8 rises so as to fill the inside of the concave portion 8, but is stopped by the eave portion 13 formed around the opening 11, and stops rising, and the base portion 14 comes into contact with the eave portion 13. The protrusion stops at a slightly lower position that almost coincides. For this reason, the projection amount β of the display pin 7 is controlled to a substantially constant range, whereby there is no excessive outflow or insufficient heating of the molten resin, and the fusion state is controlled to an appropriate state.

As described above, in the electrofusion joint 1, the opening area of the opening portion 11 of the concave portion 8 which opens from the resin layer 3 near the heating wire 4 toward the outer surface side is the intermediate portion 12.
Since the eaves 13 are formed so as to be smaller than the cross-sectional area of the display pins 7 and the display pins 7 integrally projecting from the base 14 toward the opening 11 are provided.
Can be controlled within a substantially constant range, so that there is no excessive outflow of molten resin or insufficient heating, and the fused state can be controlled to an appropriate state.

As shown in FIG. 1 and FIG.
Is smaller than the cross-sectional area of the intermediate portion 12, it becomes easier to control the height of the projection of the display pin 7.

[Brief description of the drawings]

FIG. 1 is a front view showing a cross section of a part of an electrofusion joint according to an embodiment.

FIG. 2 is an operation explanatory view of an electrofusion joint.

FIG. 3 is a front view showing a cross section of a part of a conventional electrofusion joint.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrofusion joint 2 joint main body 3 resin layer 4 heating wire 5, 6 bonded object 7 display pin 8 concave portion 9 bonded portion 10 butted portion 11 opening 12 intermediate portion 13 eaves portion 14 base 15 melting portion

Claims (2)

[Claims] 1. A joint body formed so as to be in contact with an outer peripheral portion of a body to be joined, a resin layer made of a thermoplastic resin forming the joint body, and a portion near a joint of the resin layer with the body to be joined. A buried heating wire, and an opening formed so as to open from the resin layer near the buried portion of the heating wire toward the outer surface side, and the opening area of the opening is smaller than the cross-sectional area of the intermediate portion. An electrofusion joint comprising: a recess formed with an eaves portion; and a display pin integrally projecting from a base of the recess toward an opening. 2. The electrofusion joint according to claim 1, wherein the area of the base of the concave portion is smaller than the cross-sectional area of the intermediate portion.