JPH07205190A - Production of welded joint - Google Patents

Abstract

PURPOSE:To obtain a good welded joint by melting the thermoplastic resin covering the electric heating element of left and right densely wound parts under heating and fixing a thermoplastic resin film between the central part having the electric heating element roughly wound therearound and an injection port to inject a molten thermoplastic resin to provide a thermoplastic resin layer to the outer peripheral surface of an intermediate product. CONSTITUTION:After left-hand and right-hand cores 2, 3 are connected to assemble a core, a coated electric wire 4 is spirally wound around the outer peripheral surface of the core so that the left and right parts thereof become dense and the central part thereof becomes rough and terminal pins 51 are attached to both ends of the electric heating element of the coated electric wire 4 to obtain an intermediate product. Next, the thermoplastic resin on the surface on the injection side of the parts around which the coated electric wire 4 is densely wound is melted to be integrally welded. When the intermediate product is attached to a mold, the terminal pins 51 are attached to the terminal attaching mold 5 of a fixing jig 9 and a thermoplastic resin film 8 is attached between an injection port 91 and the central part of the core by a mold 6 for formation of an indicator pin. Next, a molten thermoplastic resin is injected to form a thermoplastic resin layer 7 on the outer peripheral surface of the intermediate product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a welding joint for welding a gas pipe or a water pipe made of a thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, a welding joint has been disclosed in Japanese Patent Laid-Open No. 10739/1992.
It is manufactured as described in Japanese Patent No. 4 publication. Briefly explaining this manufacturing method, the left core and the right core are joined and assembled into a core, and an electric heating element such as a nichrome wire coated with a thermoplastic resin (hereinafter referred to as a coated conductive wire) is wound on the outer peripheral surface of the core. Manufacture intermediate products. At this time, the winding method of the coated conductor was such that the thermoplastic resin tube was inserted into the welding joint so that the whole was heated uniformly, that is, the left and right parts were tightly wound and inserted from both sides. Between the thermoplastic resin pipes, that is, in the central portion where the thermoplastic resin pipes are not provided, the winding is performed loosely.

Next, this intermediate product is attached to a mold of an injection molding machine, and molten thermoplastic resin is injected onto the outer peripheral surface of the core. Then, due to the heat of the molten thermoplastic resin, the thermoplastic resin coating the electric heating element is also melted and integrated with the injected thermoplastic resin, and the heat generated when the electric heating element is embedded in the outer peripheral surface of the core. A plastic resin layer is formed. Then, after taking out from the mold and cooling, the left core is pulled out to the left side and the right core is pulled out to the right side, whereby a cylindrical welded joint in which the electric heating element is embedded in the inner peripheral surface is manufactured.

To use this welding joint, after inserting the ends of the thermoplastic resin pipes connected to both ends into the cylindrical welding joint, an electric current is passed through the electric heating element to generate heat and the welding is performed by this heat. The inner peripheral surface of the joint is melted, and the inner peripheral surface is welded to the outer peripheral surface of the thermoplastic resin pipe to connect the thermoplastic resin pipes. Therefore, usually, terminal pins connected to both ends of the electric heating element are provided on the outer peripheral surface of the welding joint so that the electric heating element and the power source can be easily connected. In addition, a hole reaching the vicinity of the inner peripheral surface is provided on the outer peripheral surface of this welding joint, and further, an indicator pin is provided so as to project into this hole, and when the inner peripheral surface of the welding joint is thermally expanded, As a result, the indicator pin rises by being pushed by the molten thermoplastic resin. The state of melting of the inner surface of the welded joint can be understood by observing the state of rise of the indicator pin.

[0005]

However, in the method for manufacturing the above-mentioned welded joint, when the molten thermoplastic resin is injected onto the outer peripheral surface of the core around which the coated conductive wire is wound, the injection pressure causes the coated conductive wire to move, resulting in electric heating. Element shifts to one side,
This electric heating element is often short-circuited. When the thermoplastic resin pipes are connected by the welding joint in which the electric heating element is displaced to one side or short-circuited as described above, there is a problem that the inner peripheral surface of the welding joint cannot be uniformly heated as desired and the connection cannot be made well.

In order to solve this, the present inventor heats and melts the thermoplastic resin covering the electric heating elements in the left and right densely wound portions and connects the adjacent thermoplastic resins. Fix the injection hole side of the tightly wound electric heating element in a lump so as not to move individually, and pass the thermoplastic resin film between the densely wound parts on the left and right, and attach both ends of this thermoplastic resin film. I tried to fuse the left and right electric heating elements to the thermoplastic resin that covers them and fix the left and right electric heating elements so that the lumps of the left and right electric heating elements did not move. Since the lumps on both sides could not be fixed sufficiently and sometimes moved, a good welded joint could not be manufactured.

Further, there are individual differences in attachment of the thermoplastic resin film, and the thermoplastic resin film may be displaced from the injection port side of the mold. When the thermoplastic resin film is displaced in this way, there is a problem that the injected resin enters the lower side of the thermoplastic resin film and rises to move the electric heating element. Therefore, an object of the present invention is to provide a method for manufacturing a welded joint in which the thermoplastic resin layer can be provided on the outer peripheral surface of the core so that the electric heating element does not move even when the thermoplastic resin is injected. .

[0008]

The present invention has been made to achieve the above object, and an electric heating element in which the outer peripheral surface of a core in which a left core and a right core are joined is coated with a thermoplastic resin. Is manufactured by winding the left and right parts densely around the center part, manufacturing the intermediate product, attaching this intermediate product to the mold of the injection molding machine, and melting the thermoplastic resin from the injection hole of this mold to the intermediate product. After injecting to the outer peripheral surface and providing the thermoplastic resin layer in which the injected thermoplastic resin and the thermoplastic resin covering the electric heating element are integrated on the outer peripheral surface of the core, pull out the left and right cores In the method for manufacturing the welding joint, the thermoplastic resin covering the electric heating elements in the left and right densely wound portions is heated and welded and fixed, and the electric heating elements are sparsely wound between the central portion and the injection hole. Fix the thermoplastic resin film on After, in which providing a thermoplastic resin layer on the outer peripheral surface of the intermediate product by injecting a molten thermoplastic resin from the injection hole.

In the present invention, there are various means for fixing the thermoplastic resin film between the central portion where the electric heating element is sparsely wound and the injection hole. For example, a thermoplastic resin film may be directly adhered to the thermoplastic resin covering the electric heating element, or a terminal terminal fixed type for fixing the terminal terminal attached to the end of the electric heating element may be attached. However, the most preferable means is, as in claim 2, in which two indicator pin molding dies are projected in the mold with the injection hole sandwiched therebetween, and the thermoplastic resin film is provided with through holes. This is a means for inserting the indicator pin molding die into the through hole of the thermoplastic resin film and fixing the thermoplastic resin film between the central portion where the electric heating element is sparsely wound and the injection hole.

The thermoplastic resin used in the present invention, that is, the thermoplastic resin coating the electric heating element, the thermoplastic resin injected by the injection molding machine, the thermoplastic resin used for the film, etc., have been conventionally known. Although thermoplastic resins which are used can be used, polyolefin resins such as polyethylene and polypropylene are particularly preferable. Then, the thermoplastic resin covering the electric heating element, the thermoplastic resin to be injected,
The thermoplastic resins such as the thermoplastic resin used for the film may be different resins as long as they are fused and integrated, but the same type of resin is easily integrated, which is preferable.

The size of the thermoplastic resin film used in the present invention may be set within a range capable of shielding the electric heating element from moving due to the force of the molten thermoplastic resin injected from the injection hole. For example, in the present invention, the thermoplastic resin provided on the surface of the left and right densely wound coated conductors is heated and melted, and adjacent thermoplastic resins are connected to each other to form a densely wound coated conductor. Since the injection hole side is fixed so as not to move individually, the left and right coated conductors do not move individually due to the injection pressure of the molten thermoplastic resin injected from the injection hole, but the left and right coated conductors are lumped together. May be moved. Since the thermoplastic resin film prevents the covered conductors from moving as a lump, the size of the thermoplastic resin film is such that the covered conductors are sparsely wound and the left and right dense It suffices if the range is such that it covers 2 to 5 turns of the covered conductive wire that is wound around. Of course, if the left and right coated conductors do not move with each other, it is possible to shield more or less than this.

In the present invention, the indicator pin molding die is provided in a protruding manner in the mold, but the indicator pin molding die may be directly provided on the mold, or the indicator pin molding die may be cured. This jig may be attached to a tool and attached to a mold. In the present invention, the injection hole of the electric heating element that is closely wound by heating and melting the thermoplastic resin that covers the electric heating elements in the left and right densely wound portions and connecting the adjacent thermoplastic resins The sides are fixed so that they do not move individually. As a means for fixing the injection hole side so as not to move individually, only the injection side of the mold may be heated and melted by using, for example, a soldering iron, or the whole may be melted. . Further, both sides may be heated and melted with the injection side interposed. In short, it suffices to fix the electric heating element on the injection hole side so as not to move due to the injection pressure of the molten thermoplastic resin from the injection hole. If the injection hole side does not move due to the injection pressure of the molten thermoplastic resin, the position other than the injection hole side does not move.

[0013]

In the present invention, the thermoplastic resin covering the electric heating elements in the densely wound portions on the left and right is heated and melted so that the adjoining thermoplastic resins are connected so as not to move individually. Since they are fixed, the coated wires in the left and right densely wound portions, that is, the electric heating elements do not move individually due to the injection pressure of the molten thermoplastic resin. Further, since the thermoplastic resin film is provided between the portion where the coated wire is sparsely wound and the injection hole, even if the molten thermoplastic resin is vigorously injected from the injection hole, The resin collides with the thermoplastic resin film and does not directly collide with the sparsely wound central portion. Therefore, the left and right coated conductor wires do not move in a lump. After all, the whole covered wire does not move.

The mold for producing this welded joint is usually
Since the indicator pin molding die for forming the indicator pin is projected, in the present invention, the indicator pin molding die is projected so as to sandwich the injection hole, and the thermoplastic resin is provided with the through hole. And
Insert the indicator pin molding die into the through hole of the thermoplastic resin film and attach the thermoplastic resin film. Then, the thermoplastic resin film can be easily and surely provided between the central portion where the coated wire is sparsely wound and the injection hole, and therefore, as in the conventional case, the molten thermoplastic resin injected from the injection hole is melted. The resin does not flow into the lower side of the film to move the electric heating element.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 4 show an embodiment of the present invention, FIG. 1 is an explanatory view showing a core around which a coated conductive wire is wound, FIG. 2 is a perspective view of a thermoplastic resin film, and FIG. 3 is a mold of a core. And FIG. 4 is an explanatory view showing the positions of the thermoplastic resin film and the core shown in FIG.

1 to 4, 1 is a core,
The core 1 is formed by joining the right core 2 and the left core 3 together. The right core 2 and the left core 3 are composed of columnar core bodies 21 and 31, grips 22 and 32, and collars 23 and 33 provided therebetween. Reference numeral 4 denotes a coated conductive wire (electric heating element coated with a thermoplastic resin). The coated conductive wire 4 is an electrical heating element made of a nichrome wire coated with a thermoplastic resin made of polyethylene.
Then, as shown in FIG. 1, the covered conductive wire 4 is spirally wound densely on the left and right parts of the outer peripheral surface of the core 1 and sparsely on the central part to manufacture an intermediate product.

Reference numeral 5 denotes a terminal pin mounting die, which holds a terminal pin 51 connected to an end portion of the electric heating element.
6 is an indicator pin molding die. The indicator pin molding die 6 and the terminal pin mounting die 5 are fixed to a fixing jig 9, and the fixing jig 9 can be fixed to the mold. Reference numeral 7 is a thermoplastic resin layer formed on the outer peripheral surface of the core 2.

Reference numeral 8 denotes a thermoplastic resin film made of a polyethylene film. As shown in FIG. 2, the thermoplastic resin film 8 has an arc-shaped cross section so as to cover the outer peripheral surface of the core 1 in the width direction. The length of one of the densely wound portions of the covered conductive wire 4 is the third to the fifth central portion of the covered conductive wire 4 of the core 1 through the sparsely wound central portion of the covered conductive wire 4 of the other densely wound portion. The covering conductor 4 is composed of a substantially curved rectangular shielding portion 81 up to the third to fifth windings, and mounting portions 82 projecting on both sides of the shielding portion 81. The mounting portions 82 projecting on both sides of the shielding portion 81 have indicator pins. A through hole 83 into which the molding die 6 is inserted is provided.

Next, a method for manufacturing the welded joint will be described. After assembling the right core 2 and the left core 3 by assembling them into the core 1, as shown in FIG. 1, the covered conductive wire 4 is spirally formed on the outer peripheral surface of the core, and the left and right parts are densely sparse in the central part. After winding, the terminal pins 51 are attached to both ends of the electric heating element of the covered conductor 4 to manufacture an intermediate product. next,
A high-temperature soldering iron is applied to the surface of the densely wound portion of the coated conductor 4 on the injection hole side to melt the thermoplastic resin on the surface,
Adjacent thermoplastic resins are almost connected and fused (45) integrally. In this way, the electric heating elements in the left and right densely wound portions are fixed in a lump so as not to move individually.

An intermediate product in which the left and right electric heating elements are prevented from moving is attached to the mold of the injection molding machine.
At this time, the terminal pin is attached to the terminal pin attachment die 5 of the fixing jig 9 to which the terminal pin attachment die 5 and the indicator pin forming die 6 are attached, and the attachment jig 9 is attached to the die. Next, the indicator pin molding die 6 is inserted into the through hole 83 provided in the mounting portion 82 of the thermoplastic resin film 8 to mount the thermoplastic resin film 8. Then, the thermoplastic resin film 8 can be easily and reliably provided between the injection hole of the mold and the sparsely wound central portion of the coated conductor wire 4.

Next, the injection hole 91 is injected from the nozzle of the injection molding machine.
Then, the molten thermoplastic resin is injected. Then,
The heat of the injected thermoplastic resin melts the thermoplastic resin coating the coated conductive wire 4, and the thermoplastic resin layer 7 is formed on the outer peripheral surface of the core 1 together with the injected thermoplastic resin. At this time, the thermoplastic resin film 8 is provided between the injection hole 91 and the sparsely wound central portion of the coated conductive wire 4.
Therefore, even if the melted thermoplastic resin is vigorously injected from the injection hole 91, it does not directly hit the central portion where the coated conductor 4 is sparsely distributed, and therefore, the injection pressure causes the coated conductor 4 to move. There is no.

After the thermoplastic resin layer 7 is provided on the outer peripheral surface of the core 1 in this way, it is removed from the mold and the left core 3 is pulled out to the left side and the right core 2 is pulled out to the right side. A welded joint in which a heating element is embedded can be manufactured. When a thermoplastic resin pipe was connected using this welding joint, the inner surface of the welding joint was melted in a predetermined manner, and the thermoplastic resin pipe could be connected without any trouble.

[0023]

According to the method for manufacturing a fusion-bonded joint of the present invention, the densely wound portions on the left and right are individually connected by integrally melting the thermoplastic resin coating the adjacent coated conductors. Do not move. In addition, since the thermoplastic resin film is present between the sparsely wound portion and the injection hole of the mold, the sparsely wound portion does not come into direct contact with the injected thermoplastic resin and becomes dense. The part where it is present does not move as a lump. Therefore, the entire covered conductor does not move, the electric heating element does not shift to one side, and there is no short circuit, and a good quality welded joint can be manufactured.

Further, since the indicator pin molding die is provided with the injection hole sandwiched and the thermoplastic resin film is attached to the indicator pin molding die, this thermoplastic resin film is easily and surely injected into the mold. It is provided between the hole and the central part where the electric heating element is sparsely wound, and the thermoplastic resin injected from the injection hole can flow into the lower side of the film and move the electric heating element as in the conventional case. It's safe because there isn't any.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is an explanatory view showing a core around which an electric heating element coated with a thermoplastic resin is wound.

FIG. 2 is a perspective view of a thermoplastic resin film.

FIG. 3 is an explanatory view showing a state in which a core is attached to a mold.

FIG. 4 is an explanatory view showing the positions of the thermoplastic resin film and the core of FIG.

[Explanation of symbols]

1 core 2 right side core 3 left side core 4 electric heating element (coated wire) coated with thermoplastic resin 5 terminal pin mounting mold 6 indicator pin molding mold 7 thermoplastic resin layer 8 thermoplastic resin film 9 fixing jig 91 Mold injection hole

Claims (2)

[Claims] 1. An intermediate heating element is manufactured by closely winding left and right portions of an electric heating element in which a left-side core and a right-side core are joined to each other with an outer peripheral surface of the core covered with a thermoplastic resin. This intermediate product is attached to the mold of the injection molding machine, the molten thermoplastic resin is injected from the injection hole of the mold to the outer peripheral surface of the intermediate product, and the injected thermoplastic resin and the electric heating element are covered. In the method of manufacturing a fusion joint in which the thermoplastic resin layer that is integrated with the existing thermoplastic resin is provided on the outer peripheral surface of the core, and then the left and right cores are pulled out, the left and right densely wound portions of the electric heating element are covered. After fixing the thermoplastic resin by heating and welding, and fixing the thermoplastic resin film between the center part where the electric heating element is sparsely wound and the injection hole, the molten thermoplastic resin is injected from the injection hole. And the outer peripheral surface of the intermediate product is thermoplastic A method for manufacturing a welded joint, which comprises providing a resin layer. 2. A means for fixing a thermoplastic resin film between a central portion of an electric heating element of a welding joint according to claim 1 which is loosely wound and an injection hole sandwiches the injection hole in a mold. With two indicator pin molding dies protruding from, and a through hole is provided in the thermoplastic resin film, the indicator pin molding die is inserted into this through hole of the thermoplastic resin film to sparse the electric heating element. A method for manufacturing a fusion-bonded joint, which is a means for fixing a thermoplastic resin film between a wound central portion and an injection hole.