JP4569880B2 - Manufacturing method of electroweld plastic pipe joint - Google Patents

Description

The present invention relates to a method for manufacturing an electroweld plastic pipe joint (hereinafter simply referred to as a joint ) .

  Conventionally, it is well known to connect a joint made of a thermoplastic resin material such as polyethylene or polybuden and a pipe by electrowelding. For example, as shown in FIG. 3, the joint 1 is wound around an inner cylinder member 1a called an inner, an outer cylinder member 1b called an outer provided so as to wrap the inner 1a, and a spiral groove 1c formed on the inner 1a. It consists of a heating wire 3 and metal connector pins 2 individually connected to both ends of the heating wire 3. In the welding operation, a pipe 4 is inserted into the joint 1, and a current-carrying terminal (not shown) on the controller side is connected to the connector pins 2 at both ends. The joint 1 and the pipe 4 are welded and connected by heat generation.

  The manufacturing procedure of the joint 1 will be briefly described with reference to FIG. First, as shown in (A), the inner 1a is manufactured by injection molding. Next, in (B), the connector pins 2 are respectively attached to seats provided at both ends of the inner 1a. In (C), the tip of the heating wire 3 is joined to one connector pin 2. Furthermore, a certain tension is applied, and the heating wire 3 is wound along the spiral groove 1c of the inner 1a. At (D), the rear end of the heating wire 3 is joined to the other connector pin 2 to complete the winding. Finally, the wound inner 1a is mounted on an injection molding machine, and the outer 1b is formed on the outer periphery of the inner 1a to complete the joint 1 as shown in FIG.

As described above, the heating wire 3 connected to one connector pin 2 is wound around the outer peripheral surface of the inner 1 a with a constant tension, and the rear end is connected to the other connector pin 2. For this reason, the tension at the time of winding remains between both the connector pins 2.
The inner 1a and the outer 1b are manufactured by injection molding with polyethylene or polybutene. And the operation | work which winds the heating wire 3 around the inner 1a is often just after the inner 1a is injection-molded, and the surface temperature of the inner 1a is about 80 degreeC. The longitudinal elastic modulus at this time is about 140 Mpa in the case of polyethylene material, and this is the property that the longitudinal elastic modulus at room temperature (about 20 ° C.) is 1000 Mpa. Winding work is performed at the time. As described above, since the connector pin 2 is mounted on the seat 1d of the inner 1a which is easily deformed, the connector pin 2 may be tilted or pulled out due to the tension during winding.

If the connector pin 2 is greatly inclined, when the outer 1b is injection-molded into the wound inner 1a, the mold and the connector pin 2 interfere with each other, and the inner 1a cannot be mounted on the mold. There is a problem that the connector pin 2 may be crushed when it is broken. Further, when the connector pin 2 is pulled out, it is a defective product.
The present invention, the connector pin 2 attached to the inner 1a, also act tension during winding, less inclined connector pins 2, exit or method of manufacturing an electric welding type plastic KanTsugi hand not to The purpose is to provide.

The method for producing an electroweld plastic pipe joint according to the present invention includes an inner molding step of molding an inner cylinder member having a seat with a hole at both ends, and one end having a burr of a connector pin inserted into the seat of the inner cylinder member. pin charging step and the winding step of the winding in the inner cylindrical member, manufacturing of the electric welding type plastic pipe joint having an outer forming step of coating the outer tubular member forming a part completing the step of In the method , a cooling process is provided such that the seat of the inner cylinder member is cooled between the inner molding process and the winding process, and the pin insertion process is performed before the cooling process.

Also, according to the electro-welding type method for producing a plastic pipe joint of the present invention, a connector pin which the back is provided can be easily inserted into the seat, electric welding type plastic according to industrially advantageously present invention Pipe joints can be produced.

An electroweld plastic pipe joint that is an object of the present invention will be described.
As a form of inclination of the connector pin 2, there are a case where the seat 1d itself is inclined and a case where the connector pin 2 itself is inclined in the seat 1d. Naturally, they may occur in an overlapping manner. As a result, when the inclination exceeds a certain allowable limit, the line is pulled out by the tension of the line.
First, means for suppressing the inclination of the seat 1d will be described.
When the displacement amount of the front end portion of the seat due to the winding tension is Y, Y is expressed by the following formula 1.

  The tension w has a predetermined value, and the length L is defined by the shape of the joint. If the seat displacement amount Y is to be reduced under this condition, the longitudinal elastic modulus E or the cross-sectional secondary moment I may be increased.

First, a method for increasing the longitudinal elastic modulus E will be described.
As described above, in the case of polyethylene, the longitudinal elastic modulus is small when the temperature is high, and in order to increase this, the temperature may be lowered. For this purpose, the inner may be cooled between the inner molding step and the winding step. This cooling may be performed by cooling the inner, particularly the seat, using a blower or a refrigerant before the step of mounting the connector pin 2, or both the connector pin 2 and the seat 1 d after the step of mounting the connector pin 2. It may be performed by applying cold air to the surface. Natural cooling may be used as a cooling means. The cooling temperature is preferably room temperature (about 10 to 30 ° C.), but may be appropriately determined in accordance with the dimensions of seats and connector pins regulated by the product specifications. It is further preferable to attach the connector pin 2 that has been cooled to room temperature or lower, for example, about 0 to 10 ° C. in advance.

Next, a method for increasing the cross-sectional secondary moment I will be described.
Assuming that winding is performed on the inner la having a temperature after molding of, for example, 80 ° C., as described above, the longitudinal elastic modulus is reduced to about 1/7 compared with that at normal temperature. Therefore, a seat having a secondary moment of inertia that is about seven times the sectional moment of inertia Ia of the allowable displacement limit when normal winding tension is applied at normal temperature may be used. For this purpose, it may be enlarged uniformly in all directions of the seat, or may be enlarged by installing ribs or the like in the direction of receiving the winding tension. The rate of increase with respect to the secondary moment of inertia Ia may be determined in accordance with temperature variations during actual winding, product design conditions, and the like, but is preferably a value that is four times or more. In the above description, the sectional moment is explained. However, if the shape factor defining the amount of displacement, for example, the section coefficient and the sectional shape are simple, the area may be evaluated.
In addition, when installing the rib, not only the rib shape as shown in FIG. 4A, for example, which acts to improve the rigidity against the winding tension, but also the heating wire as shown in FIG. It can be easily formed into a shape that can also serve as a guide and support when connecting the connector to the connector pin.

Next, means for suppressing the inclination of the connector pin 2 in the seat will be described. Inclination occurs because there is a gap between the connector pin 2 and the hole provided in the seat 1d in which it is inserted. I'm taking it. However, when the winding tension is applied, a moment is generated in the connector pin 2, and a compressive force is applied to a portion of the hole that supports the moment, causing a compressive deformation. This amount of deformation is defined by the value of the longitudinal elastic modulus, and as described above, there is a large difference between the state where the temperature after molding is high and the normal temperature, and at 80 ° C., it is about 7 times easier to deform than at 20 ° C. .
Therefore, as described above, a cooling process may be provided between the inner molding process and the winding process. It is also effective to increase the outer diameter of the connector pin and the insertion depth within the allowable range in product design.

In order to prevent the connector pin 2 from coming off, it is also effective to use a connector pin 20 with a burr having a shape as shown in FIG. The connector pin 20 with the burr is provided with a burr 20a for preventing it from coming off at the tip portion on the side inserted into the inner 1a.
In this case, once the connector pin 20 with the burr is attached to the seat 1d of the inner 1a, even if a moment is applied to the connector pin 20 with the burr, the burr 20a can receive this. It becomes difficult to incline, and it does not come out of the seat 1d. Needless to say, it is more effective when combined with the seat of the structure described above.
When inserting the connector pin 20 with the burr, it is preferable that the temperature of the inner 1a is high and the hole surface is soft because the burr insertion resistance is small. Therefore, when combined with the cooling process described above, it is better to cool after inserting the connector pin 20 with the burr.

It is a perspective view which shows the manufacturing process for demonstrating this invention. It is a figure which shows the shape of a connector pin with a burr. It is sectional drawing which shows joining of an electroweld plastic pipe joint and a pipe. It is a figure which shows the shape of a seat with a rib.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric welding type plastic pipe joint 1a Inner 1b Outer 1c Spiral groove 1d Seat 2 Connector pin 3 Heating wire 4 Pipe 20 Connector pin with burr

Claims (1)

An inner molding process for molding an inner cylinder member having a seat with holes at both ends, a pin insertion process for inserting one end having a burr of a connector pin into the seat of the inner cylinder member, and winding the inner cylinder member a winding step of, in the manufacturing method for an electro-welded type plastic pipe joint having an outer forming step of coating the outer tubular member forming a part completing the process, the inner between the inner molding step and the winding step A method for producing an electroweld plastic pipe joint, wherein a cooling step is provided such that a seat of a cylindrical member is cooled, and the pin insertion step is performed before the cooling step.

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