JPH05318515A - Manufacture of synthetic resin pipe having receiving port in which electric heating coil is embedded - Google Patents

Abstract

PURPOSE:To simply manufacture a synthetic resin pipe having a receiving port in which an electric heating coil is embedded. CONSTITUTION:An electric heating coil 1 is provided to the outer peripheral surface of a columnar inner mold 3 and one end part of a synthetic resin pipe 2 is fitted to the outer peripheral surface of the inner mold 3 and the electric heating coil and the outer periphery of the leading end of the synthetic resin pipe 2 are surrounded by an outer mold 4 so as to leave a predetermined interval. Subsequently, the receiving port molding cavity formed between the inner and outer molds 3, 4 is filled with a molten resin and, after the molten resin integrally fuses the electric heating coil 2 and the leading end part of the synthetic resin pipe 2 to be solidified, the inner and outer molds 3, 4 are opened. By this constitution, the synthetic resin pipe having the receiving port, in which the electric heating coil is embedded can be simply manufactured. When this synthetic resin pipe is used, piping execution can be simply performed and an execution time can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily manufacturing a synthetic resin pipe having a receptacle in which an electric heating coil is embedded.

[0002]

2. Description of the Related Art In the field of piping such as gas pipes, it has hitherto been possible to use the conventional method shown in FIG.
As shown in the partial cross-sectional view, the pipe joint 1a in which the electric heating coil 11a is embedded in the inner peripheral surface of the receiving port is used, and the synthetic resin pipes 2a are fusion-bonded to both ends thereof.

By the way, the synthetic resin pipe 2 is attached to the pipe joint 1a.
In the case of fusion-bonding a, the end of the synthetic resin pipe 2a is fitted into one of the receiving ports of the pipe joint 1a, the electric heating coil 11a is heated to perform the fusion-bonding, and then the other receiving port is made of synthetic resin pipe. Two
The synthetic resin pipe 2a is inserted in the same manner as described above after the end portion of a is inserted.
Were fusion bonded.

[0004]

However, in the case of this pipe joint, the connecting operation of fitting and joining the synthetic resin pipes 2a into both the receiving ports at the time of pipe construction on site is troublesome. Not only that, it takes a certain amount of time for the molten resin interposed between the inner peripheral surface of each of the receiving ports and the outer peripheral surface of the end portion of the synthetic resin pipe 2a to be cooled and solidified. There was a problem of this. Therefore, it has been proposed to embed an electric heating coil in advance on the inner peripheral surface of the receiving port provided at one end of the synthetic resin pipe, but if an effective method / means for easily manufacturing this synthetic resin pipe is found, No
Its development was desired.

The present invention has solved the above problems and provides a method for easily manufacturing a synthetic resin pipe having a receptacle in which an electric heating coil is embedded.

[0006]

According to the present invention, an electrothermal coil is mounted on the outer peripheral surface of a cylindrical inner die, and one end of a synthetic resin pipe is externally inserted into the inner die to form the electrothermal coil and the synthetic resin pipe. The outer peripheral side of the tip end of is surrounded by an outer mold at a predetermined interval. Then, a molten resin is filled in the mouth-forming cavity formed between the inner mold and the outer mold, and the molten resin is fused integrally with the electric heating coil and the tip of the synthetic resin pipe. It is characterized by opening the inner mold and the outer mold after solidification.

[0007]

Operation: One end of a synthetic resin pipe is externally inserted into an inner mold, and the mouth end forming cavity formed by surrounding the outer peripheral side of the tip end of the synthetic resin pipe with the outer mold is filled with molten resin and solidified by cooling. Then, a receiving port is formed at one end of the synthetic resin pipe. Further, at the same time when the receiving port is formed at one end of the synthetic resin pipe, the electric heating coil mounted on the outer peripheral surface of the inner mold is embedded in the inner peripheral surface of the receiving port.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of a mold device used in the present invention, and FIG. 2 is a vertical sectional view of a synthetic resin pipe obtained by the present invention.

In the figure, reference numeral 1 is an electric heating coil. The electric heating coil 1 is formed by winding a heating wire such as a stainless wire or a nichrome wire in a spiral shape at a predetermined interval and using polyethylene.
It is integrally formed with a synthetic resin such as polypropylene or polybutene to form a cylindrical shape, and connector pins 23 are connected to both ends of the electric heating coil 1.

Reference numeral 2 is a synthetic resin tube made of polyethylene, polypropylene, polybutene or the like. One end of the synthetic resin pipe 2 has an expanded diameter, and a plurality of annular grooves are provided on the outer peripheral surface of the expanded end 211, and the receiving step portion 21 is formed on the inner peripheral surface thereof.
Two are provided. Further, the inner diameters of the receiving step portion 212 and the electric heating coil 1 are formed to have substantially the same diameter.

Next, the structures of the inner mold 3 and the outer mold 4 used in the present invention will be described. Inner mold 3 is flange 31 and cylindrical mold 3
2 and a guide portion 321 having a small diameter is provided at the tip of the cylindrical mold 32 via an inclined step portion. The outer diameter of the cylindrical mold 32 is formed to be substantially the same as the inner diameter of the receiving step portion 212 of the synthetic resin pipe 2, and the outer diameter of the guide portion 321 is substantially the same as the inner diameter of the synthetic resin pipe 2. Is formed in.

On the other hand, the outer die 4 has a half-split structure, and the inner peripheral wall thereof has an enlarged diameter end portion 21 provided at one end portion of the synthetic resin pipe 2.
The diameter is slightly larger than the outer diameter of No. 1. This outer mold 4
A side wall portion 41 that comes into contact with the outer peripheral surface of the columnar mold 32 is provided on one side wall in the axial direction, and a side wall portion 42 that comes into contact with the outer peripheral shoulder portion of the enlarged diameter end portion 211 is provided at the other side wall. Further, recesses 41 are provided at two locations on the inner peripheral wall of the outer mold 4, and support pins 42 project into the recesses 41. This recess 41
A space for forming the plug 22 is formed by the support pin 42 and the support pin 42, and the connector pin 23 can be inserted into the hole provided in the support pin 42.

Next, the step of molding the receiving port at one end of the synthetic resin pipe 2 using the inner mold 3 and the outer mold 4 will be described. First, the electrothermal coil 1 is externally inserted into the cylindrical die 32 of the inner die 3, and the connector pins 23 connected to both ends of the electrothermal coil 1 are fitted into the holes of the support pins 42 provided on the inner peripheral wall of the outer die 4. At the same time, the enlarged diameter end portion 211 of the synthetic resin tube 2 is externally inserted into the inner mold 3 and pushed in until the inner part of the socket step portion 212 comes into contact with the tip end inclined surface of the cylindrical mold 32.

Next, the outer die 4 is closed and the outer die 4 and the inner die 3 are closed.
The molten resin is injected from a gate (not shown) provided at a proper position of the outer die 4 in the mouth-forming cavity formed by the cylindrical die 32 of FIG. When the cavity is filled with the molten resin, the molten resin fuses integrally with the resin coating the electric heating coil 1 and also with the end surface of the expanded diameter end portion 211 and the outer peripheral surface thereof. A socket is formed. Therefore, the outer mold 4 is opened after waiting for the molten resin to cool and solidify, and the inner mold 3 is pulled out from the inside of the formed receiving opening. Then, the synthetic resin pipe A shown in FIG. 2 is obtained.

When the pipe construction is carried out using the synthetic resin pipe A, the receiving port 21 in which the electric heating coil 1 is embedded is provided at one end of the synthetic resin pipe 2, and therefore the other side of the receiving port 21 is provided. Simply insert the straight end of the synthetic resin pipe A, connect the power line to the connector pin 23 built in the plug 22, and heat the electrothermal coil 1, and the synthetic resin pipes A and A can be easily fused. It can be bonded to each other.

[0016]

As described above in detail, according to the present invention, the synthetic resin pipe can be formed by simply filling the molten resin into the cavity for forming an inlet formed by surrounding one end of the synthetic resin pipe with the inner mold and the outer mold. A receptacle can be formed at one end. Further, at the time of this injection molding, the electric heating coil mounted on the outer peripheral surface of the inner mold is embedded in the inner peripheral surface of the receiving port. Therefore, according to the manufacturing method of the present invention, it is possible to easily manufacture the synthetic resin tube in which the electric heating coil is embedded in the inner peripheral surface of the receiving port. When using this synthetic resin pipe for pipe construction, insert the straight pipe end of the other synthetic resin pipe into the receiving port of one synthetic resin pipe and connect them sequentially, and embed it in the inner peripheral surface of each receiving port. The synthetic resin pipes can be easily fusion-bonded to each other only by heating the existing electric heating coil.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a mold device used in the present invention.

FIG. 2 is a longitudinal sectional view of a synthetic resin pipe obtained by the present invention.

FIG. 3 is a cross-sectional view of essential parts showing a state in which a synthetic resin pipe is connected using a conventional pipe joint.

[Explanation of symbols]

 1 Electric heating coil 2 Synthetic resin tube 3 Cylindrical inner mold 4 Outer mold

Claims (1)

[Claims] 1. An electrothermal coil (1) is mounted on the outer peripheral surface of a cylindrical inner die (3), and one end of a synthetic resin pipe (2) is externally inserted into the inner die (3) to form the electrothermal coil (1). 1) and the outer peripheral side of the synthetic resin pipe (2) at the tip end are surrounded by an outer die (4) at a predetermined interval, and then the inner die (3) and outer die (4)
The molten resin is filled in the mouth-forming cavity formed between and, and the molten resin is fused and solidified integrally with the electrothermal coil (1) and the tip of the synthetic resin pipe (2). A method for producing a synthetic resin pipe having a socket in which an electrothermal coil is embedded, characterized in that the inner mold (3) and the outer mold (4) are opened.