JP2001219479A - Method for manufacturing welded joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a welded joint by which an outgoing allowance for an indicator pin during welding can be secured, even when a hard-to-fluidize thermoplastic resin is used. SOLUTION: This method for manufacturing a welded joint 1 is to manufacture a welded joint 1 incorporating an energized heat generating element 2 with the outer peripheral part of the joint 1 into which the indicator pin 3 serving as a criterion for the termination of welding can be inserted. The method is characterized by that it comprises the process to manufacture the welded joint 1 by forming insertion holes 4 for the indicator pin 3 with a proper space formed between the bottom part of the insertion hole 4 and the energized heat generating element 2, and the process to thrust a shaping pin 9 into the insertion holes 4 opened in the preceding process and reshape the insertion holes 4 by getting the tip part of the shaping pin 9 close to the element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding joint for connecting and connecting thermoplastic synthetic resin tubes.

[0002]

2. Description of the Related Art Thermoplastic synthetic resin pipes such as polyethylene, polypropylene and polyvinylidene fluoride are used for applications such as gas pipes, water pipes and sewer pipes, and are buried underground for piping. Since the above-mentioned thermoplastic synthetic resins are all difficult to bond with an adhesive, a welding joint having a current-carrying heating element built in the inner peripheral surface side is used for the connection. As described in Swiss Patent No. 601,719, a conventional welding joint is provided with an insertion hole in an outer peripheral portion,
An indicator pin is inserted into this insertion hole, and the margin of the insertion is used as a measure of the end of welding between the pipe and the welded joint. The indicator pin is a shaft-shaped one having an inner hole formed at the tip end in the axial direction, and thermally expands due to energization of an energizing heating element containing a thermoplastic resin filled in the inner hole,
Projects from the outer surface of the welded joint. The protrusion of the indicator pin, which is the amount of protrusion, serves as a measure of the end of welding between the pipe and the welded joint.

[0003] In the above-described method for manufacturing a welded joint, an electric heating element (for example, a coated wire in which a metal wire is coated with a thermoplastic resin) is wound around the outer periphery of a core, and formed between the core and an outer mold. Molding is performed by injecting the molten thermoplastic resin into the cavity, removing it from the mold after cooling and solidifying. In the above manufacturing method, the insertion hole of the indicator pin is formed by disposing a molding pin (having an outer peripheral shape substantially the same as that of the indicator pin) so as to protrude into the cavity. A predetermined clearance is secured between the tip of the pin for use and the covering wire wound around the core.

[0004]

In the above welded joint, the margin of the indicator pin, which is a measure of the end of welding, increases as the clearance between the current-carrying heating element and the indicator pin decreases. However, in the case of using a thermoplastic resin having a high viscosity and a low fluidity in the production of a welded joint, the clearance between the heating element and the molding pin is increased because the resin is filled in the inner hole of the molding pin. Need to take. Then, the resin filled in the inner hole of the indicator pin at the time of welding escapes from this clearance at the time of thermal expansion, the margin of the indicator pin becomes small, and the indicator pin does not protrude enough to serve as a guide at the end of welding. There is.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a welded joint which can secure an allowance for an indicator pin at the time of welding even when a thermoplastic resin which does not easily flow is used. It is in.

[0006]

The present invention according to claim 1 is used for connecting pipes, and welds the pipe and the welded joint to the outer peripheral portion of the welded joint having a current-carrying heating element built in the inner peripheral surface side. In a method of manufacturing a welded joint which can be provided by inserting an indicator pin as an indication of completion, (1) an outer peripheral shape and an inner hole shape of a shaft-shaped indicator pin having an inner hole formed at an end portion in an axial direction. (2) a step of forming an insertion hole substantially in the shape of a welding joint by providing an appropriate gap between the bottom of the insertion hole and the current-carrying heating element and forming the insertion hole on the outer periphery of the welding joint;
Into the insertion hole formed in the above step, insert a shaping pin having a tip portion having substantially the same shape as the indicator pin, press the periphery of the insertion hole into a heated state, and push the tip portion of the shaping pin into an electric heating element. And reshaping the insertion hole in close proximity.

According to a second aspect of the present invention, in the method for manufacturing a welded joint according to the first aspect, in the step of reshaping the insertion hole, the vicinity of the insertion hole is heated by using an ultrasonic welding device. It is characterized by doing.

According to the first aspect of the present invention, a shaping pin having a tip portion having substantially the same shape as the indicator pin is inserted into the insertion hole, and the periphery of the insertion hole is pressed while being heated. Since the method includes a step of reshaping the insertion hole by bringing the tip of the pin close to the energizing heating element, even if a thermoplastic resin that does not easily flow is used, the pin is inserted into the reshaped insertion hole during welding. The leading end of the indicator pin is close to the current-carrying heating element, so that the margin of the indicator pin can be secured.
In the process of manufacturing the welded joint, an appropriate distance is provided between the bottom of the insertion hole and the current-carrying heating element. Resin can be filled well.

According to the second aspect of the present invention, in the step of reshaping the insertion hole, the periphery of the insertion hole is heated by using an ultrasonic welding device. It can be heated quickly and has excellent reshaping properties.

[0010]

1 to 6 show an embodiment of the present invention. FIG. 1A is a sectional view of a mold for forming a welded joint, and FIG. The cross-sectional view of the joint, and the (c) and (d) views are cross-sectional views of the main parts of the welded joint in the reshaping step. 2 is a plan view of a molding pin, FIG. 3 is a cross-sectional view of a shaping pin, FIG. 4 is an explanatory view of an ultrasonic welder device used in a process of reshaping an insertion hole, and FIG. 5 is provided with an indicator pin. FIG. 6 is a sectional view showing a method of using the welded joint, and FIG.
FIG. 2 is an enlarged cross-sectional view showing a main part of FIG.

In FIG. 1, reference numeral 1 denotes a welded joint, and the welded joint 1 is a socket type pipe joint used for connecting a pipe P (see FIG. 5). The welded joint 1 is formed of high-density polyethylene, and has a built-in current-carrying heating element 2, 2 (covered wire) in which a metal wire such as a nichrome wire is covered with a thermoplastic resin on both sides of the inner peripheral surface. I have. An indicator pin 3 (see FIG. 5 and FIG. 6) on the outer peripheral portion of the welded joint 1 is used as an indicator of the end of welding between the pipe P and the welded joint 1.
Are formed, and insertion holes 4 and 4 into which holes can be inserted are formed.

The present embodiment is a manufacturing method for manufacturing the welded joint 1 having the above structure by an injection molding method.
(1) An insertion hole 4 which substantially matches the outer peripheral shape of the axial indicator pin 3 having an inner hole 81 formed at the end portion in the axial center direction and the inner hole shape is formed with the bottom of the insertion hole 4 and the electric heating element 2. A first step (see FIGS. 1 (a) and 1 (b)) of forming a welded joint 1 by forming an appropriate space between the welded joint 1 and the outer peripheral portion; A shaping pin 8 having a tip portion substantially the same shape as the indicator pin 3 is inserted into the insertion hole 4 formed by the above step, and the periphery of the insertion hole 4 is heated and pushed in, and the tip portion of the shaping pin 9 is inserted. A second step of reshaping the insertion hole 4 by bringing the insertion hole 4 close to the heating element 2 (FIG. 1C),
(D) Refer to the figure).

The details of the first step of manufacturing the welded joint 1 will be described below. In the first step, the energizing heating element 2 is wound and attached to a cylindrical core 6 provided so as to be sandwiched by an outer mold 5 formed as a split mold for injection molding. A molding pin 8 is attached to the outer die 5. As shown in detail in FIG. 2, the molding pin 8 is a shaft with a head, and an inner hole 81 is formed at a tip end.

The outer diameter d2 of the shaft at the tip of the forming pin 8 is 4 mm, the inner diameter d1 of the inner hole 81 is 3 mm, and the depth L1 is 16 mm. The shape of the outer periphery and the shape of the inner hole at the tip of the molding pin 8 are substantially the same as those of the indicator pin 3, and the tip of the molding pin 8 having the inner hole 81 is projected into the cavity 7. And attach it. And, in the cavity 7,
The molten polyethylene is injected from a nozzle of an injection molding machine (not shown). As the polyethylene, a melt flow rate (MFR) of 0.1 having poor fluidity is used.
Was used. Thereafter, after cooling and solidification, the outer mold 5 is opened, removed from the mold together with the molding pins 8, and the core 6 is removed. Then, as shown in FIG. 1 (b), the welded joint 1 in which the insertion hole 4 of the indicator pin 3 is formed on the outer peripheral portion is obtained.

Next, the details of the second step will be described below. The details of the shaping pin 8 to be inserted into the insertion hole 4 formed in the first step are shown in FIG. The shaft outer diameter d4 at the tip of the shaping pin 9 is 3.8 mm, and the inner hole 91
Has an inner diameter d3 of 2.5 mm and a depth L2 of 17.5 mm. That is, the shank outer shape d4 of the shaping pin 9
Is slightly smaller than the outer diameter d2 of the shank of the shaping pin 8, and the inner diameter d3 of the inner hole 91 of the shaping pin 9 is slightly smaller than the inner diameter d1 of the inner hole 81 of the shaping pin 8. I have.
The depth L2 of the inner hole 91 is about 1 mm larger than the depth L1 of the inner hole 81. Thereby, the insertion hole 4
When the shaping pin 9 is pushed into the insertion hole 4 with the periphery heated, the resin is filled into the inner hole 91 as shown in FIGS. The distance D1 between the pin 9 and the current-carrying heating element 2 can be reduced to the distance D2.

FIG. 4 shows a method of heating the periphery of the insertion hole 4 using the ultrasonic welding device 10 in the second step of reshaping the insertion hole 4. The welding joint 1 is placed on the base 11 with the shaping pins 9 facing upward, and the stand 1
01 is lowered by rotating the handle 102 so that the shaping pins 9 are attached.
Abuts on the head. Then, the ultrasonic welder device 10
The heat transfer from the shaping pin 9 generated by the
Make the surroundings heated. At this time, when the handle 102 is rotated to further lower the ultrasonic welder device 10 and the shaping pin 9 is pushed into the insertion hole 4, the tip of the shaping pin 9 is brought closer to the electric heating element 2. Can be.

Next, a method of using the welded joint 1 manufactured as described above will be described with reference to FIGS.
As shown in FIG. 5, a polyethylene pipe P is inserted into an insertion port of the welding joint 1 in which the indicator pin 3 is inserted into the insertion hole 4 and attached, and electricity is supplied to the electric heating element 2 to connect the pipe P to the welding joint 1. Weld. At this time, as shown in FIG. 6, the indicator pin 3 protrudes from the outer peripheral surface of the welded joint 1 by a margin E, which serves as a measure of the end of welding.

(Operation of the Embodiment) In this embodiment, a shaping pin 9 having a tip portion substantially the same shape as the indicator pin 3 is inserted into the insertion hole 4, and the periphery of the insertion hole 4 is heated and pushed. A second step of reshaping the insertion hole 4 by bringing the tip end of the shaping pin 9 close to the energizing heating element 2 so that the MFR is as small as 0.1 and the high-density polyethylene having a poor flow is provided. The insertion hole 4 reshaped at the time of welding
The leading end of the indicator pin 3 inserted into the connector 3 comes close to the current-carrying heating element 2, so that the allowance E of the indicator pin 3 can be secured. In the first step of manufacturing the welded joint, an appropriate distance D1 is provided between the bottom of the insertion hole 4 and the current-carrying heating element 2, so that even if high-density polyethylene with poor flow is used, the molding pin 8 can be filled with this resin well.

Further, in this embodiment, the periphery of the insertion hole 4 is heated by using the ultrasonic welding device 10 in the second step of reshaping the insertion hole 4, so that the periphery of the insertion hole 4 is made uniform. And can be heated quickly and has excellent reshaping properties.

[0020]

According to the first aspect of the present invention, even when a thermoplastic resin that does not easily flow is used, the tip of the indicator pin inserted into the insertion hole reshaped at the time of welding is close to the current-carrying heating element. In addition, it is possible to secure an indicator pin. Then, in the process of manufacturing the welded joint, even if a thermoplastic resin that does not easily flow can be used, the thermoplastic resin can be well filled in the inner hole of the molding pin.

According to the second aspect of the present invention, in the step of reshaping the insertion hole, the periphery of the insertion hole is heated by using an ultrasonic welding device. It can be heated quickly and has excellent reshaping properties.

[0022]

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an embodiment of the present invention, in which (a) is a cross-sectional view of a molding die for a welded joint, (b) is a cross-sectional view of the welded joint after forming, (c) and (c). D) is a sectional view of a principal part of the welded joint in the reshaping step.

FIG. 2 is a plan view of a molding pin.

FIG. 3 is a sectional view of a shaping pin.

FIG. 4 is an explanatory diagram of an ultrasonic welder device used in a step of reshaping an insertion hole.

FIG. 5 is a sectional view showing how to use a welded joint provided with an indicator pin.

FIG. 6 is an enlarged sectional view showing a main part of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding joint 2 Electric heating element 3 Indicator pin 4 Insertion hole 8 Molding pin 9 Shaping pin 10 Ultrasonic welder device 31, 81, 91 Inner hole P tube

Claims (2)

[Claims] 1. An indicator pin, which is used for connecting pipes and has a guide for ending welding between a pipe and a welded joint, is provided at an outer peripheral portion of a welded joint having a current-carrying heating element built in an inner circumferential surface side. (1) An insertion hole substantially matching the outer peripheral shape and the inner hole shape of an axial indicator pin having an inner hole formed at an end portion in the axial direction at the bottom of the insertion hole. Forming a welded joint by forming an appropriate gap between the welding joint and the heating element, and forming the welded joint on the outer peripheral portion; (2) the insertion hole formed in the above-described process has a tip portion substantially the same as the indicator pin; Inserting the shaped shaping pin, pushing in the vicinity of the insertion hole in a heated state, and pressing the tip of the shaping pin close to the current-carrying heating element to reshape the insertion hole. A method for producing a welded joint, characterized in that: 2. The method for manufacturing a welded joint according to claim 1, wherein in the step of reshaping the insertion hole, the periphery of the insertion hole is heated using an ultrasonic welding device.