JP3136027B2 - Molding method of plastic pipe with inlet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a plastic pipe with a receiving port, and more particularly to a method for forming a plastic pipe with a receiving port for use in, for example, electrofusion bonding.

[0002]

2. Description of the Related Art An example of this type of conventional plastic pipe with a spout is disclosed in Japanese Utility Model Laid-Open No. 62-107193. This plastic pipe is obtained by embedding a heating wire in the inner surface of the enlarged diameter receiving port formed at the end of the plastic pipe body.

[0003]

In the above-mentioned prior art,
Since two steps, a step of forming the enlarged diameter receiving port at the end of the pipe body and a step of burying the heating wire in the inner surface of the enlarged diameter receiving port, are required, there is a problem that the formability is poor. In addition, it is difficult to form a smooth inner surface of the receiving port, so that it is difficult to insert a pipe into the receiving port during joining.

[0004] Therefore, a main object of the present invention is to improve workability and to form a smooth inner surface of a receiving port.
An object of the present invention is to provide a method for molding a plastic pipe with a port.

[0005]

According to a first aspect of the present invention, there is provided (a) a step of preparing a pipe made of a polyolefin resin;
(b) attaching a fusion heater to the outer periphery of the core pin, (c) heating the end of the pipe near the softening point, (d) heating the core pin to a temperature equal to or higher than the melting point of the pipe, (e) A method of molding a plastic pipe with a socket, comprising the steps of: inserting into an end, (f) cooling the end and the core pin, and (g) removing the core pin.

A second aspect of the present invention provides (a) a step of preparing a pipe made of a polyolefin resin, (b) a step of mounting a fusion heater on the outer periphery of a core pin, and (c) heating an end of the pipe to a melting point or higher. (D) heating the core pin near the softening point of the pipe, (e) inserting the core pin into the end, (f) placing the outer mold on the outer surface of the end, (g) end and A method for molding a plastic pipe with a socket, comprising a step of cooling a core pin, a step of (h) removing an outer mold, and a step of (i) removing a core pin.

In the first or second invention, the step
In (d), a core pin heating method is used in which a high frequency current is induced from a work coil to a core pin to heat the core pin.

[0008]

According to the first aspect of the present invention, the end of the pipe is heated to near the softening point, and the core pin having a heater mounted on its outer surface is heated to a temperature higher than the melting point of the pipe. Then, by inserting the core pin into the end of the pipe, a receiving port is formed at the end of the pipe, and at the same time, the heater is embedded in the inner surface of the receiving port.

In the second invention, the end of the pipe is heated to a temperature equal to or higher than the melting point, and the core pin having a heater attached to the outer surface thereof is heated to near the softening point of the pipe. Then, by inserting the core pin into the end of the pipe, a receiving port is formed at the end of the pipe, and at the same time, the heater is embedded in the inner surface of the receiving port.
Furthermore, by forming an outer mold on the outer surface of the receiving port, the unevenness of the outer surface of the receiving port is eliminated.

[0010] In the first and second inventions,
Before inserting the core pin into the end of the pipe, an outer mold may be put on the outside of the core pin, and the receiving port may be pushed in to increase the wall thickness. In step (d), a high-frequency current is induced
So that the core pin is heated by
The surface of the core pin can be heated quickly.

[0011]

According to the present invention, moldability can be improved. Further, since the core pins are arranged on the inner surface of the receiving port when the receiving port is formed, the inner surface of the receiving port can be finished smoothly. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0012]

Referring to FIG. 2, a plastic pipe with a receiving port 10 to which the method of molding a plastic pipe with a receiving port of this embodiment is applied is made of a polyolefin resin such as polybutene or polyethylene. Including.
At the end of the pipe 12, an enlarged diameter receiving port 16 for receiving the pipe 14 to be joined is formed, and a mesh-shaped magnetic alloy heater 18 as shown in FIG.
The Curie temperature of the heater 18 is controlled by the inlet 16 and the pipe 1.
4 is set to a temperature equal to or higher than the melting temperature. However, the heater 18 may be formed, for example, as a punching metal as shown in FIG.

Such a pipe 10 is formed, for example, using a core pin 20 as shown in FIG. The core pin 20 is formed of iron, aluminum, or the like, and includes a molded portion 24 having a step portion 22. A guide portion 28 having an outer diameter substantially equal to the inner diameter of the pipe 12 is formed at one end of the molded portion 24 via a tapered portion 26, and a pipe 1 is formed at the other end.
A stopper portion 30 that contacts the end surface of the second member 2 is formed. Further, inside the core pin 20, a cartridge heater 32 is provided.
And a cooling water passage 34. However, core pin 2
As means for heating 0, means for heating by passing high-temperature steam or oil through a passage 36 formed inside the core pin 20 as shown in FIG. 6, or heating using a far-infrared heater (not shown) Means for performing such operations may be employed.
When the core pin 20 is made of a magnetic material such as iron,
For example, means for heating by inducing a high-frequency current from a work coil 38 disposed around the core pin 20 as shown in FIG. 7 may be employed. In this case, a thermocouple 40 is provided near the surface of the core pin 20,
When the thermocouple 40 detects a predetermined temperature, the output of the high-frequency power supply 42 is stopped. According to such high-frequency induction heating, the surface of the core pin 20 can be rapidly heated mainly by the skin effect. FIG. 8 is a graph of an example of an experimental result showing a relationship between an energizing time and a surface temperature of the core pin 20 when the core pin 20 is heated by high-frequency induction heating.

A method for molding a plastic pipe with a port according to this embodiment will be described with reference to the flowchart of FIG. 1 and FIG. First, in step S1, a pipe 12 made of a polyolefin resin such as polyethylene is prepared.
The end 44 is heated to near the softening point. When the pipe 12 is made of polyethylene having a softening point of 121 ° C., for example, 125 ° C. near the softening point of 121 ° C. of the polyethylene
Heated. In addition, as the pipe 12, an arbitrary pipe such as a straight pipe, an elbow, a vent, and cheese can be used.
On the other hand, in step S3, the molding portion 2 of the core pin 20
In step S5, the outer surface of the core pin 20 is heated by the cartridge heater 32 to a temperature equal to or higher than the melting point of the pipe 12. When the pipe 12 is made of polyethylene having a melting point of 128 ° C., the pipe 12 is heated to 135 ° C., which is slightly higher than the melting point of 128 ° C. of the polyethylene.

Then, in step S7, the heated and softened end portion 44 is covered from the guide portion 28 to the outer surface of the forming portion 24 (heater 18) while expanding in diameter. That is, the core pin 40 is inserted into the heat-softened end portion 44. Then, at the same time as the receiving port 16 is formed at the end portion 44, the resin melted by the core pin 20 is heated by the heater 18.
The heater 18 is embedded in the inner surface of the receiving port 16 (FIG. 2). When the end portion 44 is put on the core pin 20, the inner surface of the end portion 44 is melted.
Does not occur in the axial direction.

In step S9, the heating of the core pin 20 by the cartridge heater 32 is stopped.
Cooling water flows through a cooling water passage 34 provided inside the core pin 20. Thereby, the core pin 20 and the end 4
4 (receiving port 16) is cooled. When the end 44 (receiving port 16) is sufficiently cooled, the pipe 10 is removed from the core pin 20 in step S11. If the pipe 12 is made of polyethylene, the end 44 (the port 16) is cooled to about 80 ° C.
Cooled to about ° C.

Referring to FIG. 2, at the time of joining, the outer peripheral surface of the end of pipe 14 to be joined is cut by a scraper or the like, and this is inserted into receiving port 16 of pipe 10. Then, a work coil 38 is arranged around the receiving port 16, and a high-frequency current is induced from the work coil 38 to the heater 18. Then, the current concentrates only on the skin portion of the heater 18 due to the skin effect, and the heater 18 rapidly generates heat.
When the temperature of the heater 18 rises and reaches the Curie temperature,
The permeability decreases, so that almost no skin current flows, and the heat generated by the heater 18 decreases. When the heat of the heater 18 is transmitted to the receiving port 16, the pipe 14, and the like, and the temperature of the heater 18 decreases, the heater 18 generates heat again by the skin current. Therefore, the heater 18 is maintained at the Curie temperature or a substantially constant temperature near the Curie temperature. As a result, the synthetic resin on the joint surface between the receiving port 16 and the pipe 14 and the vicinity thereof is melted, and both are fused.

According to the method for molding a plastic pipe with a port of this embodiment, the heater 18 can be embedded in the inner surface of the port 16 at the same time as the port 16 is formed, so that the moldability can be improved. Also, by the heated core pin 20,
Since the inner surface of the end portion 44 can be melted, the heater 1
The inner surface of the receiving port 16 can be finished smoothly by promoting the resin flowing into the opening 8.

The core pin 20 in the above-described embodiment is
Instead, for example, a core pin 48 as shown in FIG. 9 may be used. The core pin 48 includes a main body 52 divided into a plurality of (six in this embodiment) segments 50, and a guide portion 54 and a tapered portion 5 at the end of the main body 52.
6, a forming portion 58, a stopper portion 60 and the like are formed, and a slide core 62 is arranged between the respective segments 50 so as to be slidable in the radial direction. Inside the main body 52,
The center pin 64 is inserted, and each slide core 62 is operated by the center pin 64. That is, when the center pin 64 is pressed, each slide core 62 is lifted, and these are fitted between the segments 50. As a result, the diameter of the guide portion 54, the tapered portion 56, and the molded portion 58 is increased, and at the same time, their outer surfaces are flush. On the other hand, when the center pin 64 is pulled, each slide core 62 is pulled in the center direction, whereby the diameter of the guide portion 54, the tapered portion 56, and the formed portion 58 is reduced. Note that FIG.
2 shows a state where the diameter of the molded portion 58 and the like is expanded.

When the pipe 10 is formed using the core pin 48, the diameter of the forming portion 58 and the like is reduced.
, A heater 18 is mounted. Then, by pressing the center pin 64, the diameter of the molding portion 58 and the like is expanded, and the molding portion 58 is expanded.
And the inner surface of the heater 18 are in close contact with each other. Core pin 4
By using 8, the heater 18 can be easily mounted by reducing the diameter of the molding portion 58. Also,
By expanding the diameter of the molding portion 58 after the heater 18 is mounted, the outer surface of the molding portion 58 and the inner surface of the heater 18 can be in close contact with each other. Performance degradation can be prevented.

When the strength of the receptacle 16 is insufficient, for example, as shown in FIG. 10, an outer die 66 is put on the outside of the core pin 20, and this outer die 66 is formed by using a cartridge heater or the like (not shown). Alternatively, the material may be heated to near the softening point, and the receiving port 16 may be pushed in to increase the thickness. In this case, as shown in the flowchart of FIG. 11, for example, after steps S1 to S5 are executed, the outer mold 66 is put on the outside of the core pin 20 in step S13, and the outer mold 66 is softened in step S15. Heated nearby. Then, after steps S7 and S9 are executed, the outer mold 66 is removed in step S17,
In step S11, the pipe 10
Is removed. The operation in each step of steps S1 to S11 is the same as that of the previous embodiment (FIG. 1), and therefore detailed description thereof will be omitted.

Referring to the flow chart of FIG. 12, in another embodiment of the method of forming a plastic pipe with a port, first, in step S21, the end 44 of the pipe 12 is heated to a temperature equal to or higher than the melting point. When the pipe 12 is made of polyethylene having a melting point of 128 ° C.,
It is heated to a temperature of, for example, 135 ° C. or more. On the other hand, in step S23, the heater 18 is attached to the molding portion 24 of the core pin 20, and in step S25, the core pin 2
0 is heated to the vicinity of the softening point of the pipe 12. When the pipe 12 is made of polyethylene having a softening point of 121 ° C., for example, a pipe having a softening point of 121 ° C. near 121 ° C.
Heat to 0 ° C. Then, in step S27,
The end 44 of the pipe 12 is put on the outer surface of the core pin 20. Then, at the same time as the receiving port 16 is formed at the end portion 44, the molten resin flows around the opening of the heater 18, and the heater 18 is embedded in the inner surface of the receiving port 16. End 4
4 is heated to a temperature equal to or higher than the melting point in step S21. Therefore, when the end portion 44 is put on the core pin 20, the outer surface thereof becomes uneven. Therefore, in step S29, the outer mold 66 is put on the outer surface of the end portion 44, whereby the outer surface of the end portion 44 is finished smoothly. Then, after the core pin 20 and the end portion 44 (receiving port 16) are cooled in step S31, the outer mold 66 is removed in step S33, and in step S35, the core pin 2 is removed.
The pipe 10 is removed from 0.

According to this embodiment, since the heating temperature of the core pin 20 can be kept lower than in the previous embodiment, the molding efficiency can be improved. In this embodiment, also, in the state in which the outer mold 66 is put on the outside of the core pin 20, the socket 16 is closed.
May be pressed to increase the wall thickness. In this case, for example, as shown in the flowchart of FIG. 13, after steps S21 to S25 are executed, the outer mold 66 is put on the outside of the core pin 20 in step S37, and the outer mold 66 is softened in step S39. Heated nearby.
Then, after steps S27 and S31 are performed, the outer mold 66 is removed in step S33,
In step S35, the pipe 10
Is removed. The operation in each step of steps S21 to S35 is the same as that of the previous embodiment (FIG. 12), and thus detailed description thereof will be omitted.

In each of the above embodiments,
By increasing the thickness of the end portion 44 of the pipe 12 in advance, the required thickness of the receiving port 16 can be ensured.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

FIG. 2 is an illustrative view showing a pipe formed in the embodiment of FIG. 1;

FIG. 3 is an illustrative view showing a heater used in the embodiment of FIG. 1;

FIG. 4 is an illustrative view showing a modified example of the heater;

FIG. 5 is an illustrative view showing a core pin used in the embodiment of FIG. 1;

FIG. 6 is an illustrative view showing another means for heating the core pin;

FIG. 7 is an illustrative view showing another means for heating the core pin;

8 is a graph showing a relationship between an energizing time and a surface temperature of the core pin when the core pin is heated by using the heating means of FIG. 7;

FIG. 9 is a perspective view showing a modified example of a core pin.

FIG. 10 is an illustrative view showing a state where an outer mold is put on the outside of the core pin;

FIG. 11 is a flowchart showing a step of pushing a receiving port and performing a wall-thickening process in the embodiment of FIG. 1;

FIG. 12 is a flowchart showing another embodiment of the present invention.

FIG. 13 is a flowchart showing a step of pushing a receiving port and performing a wall-thickening process in the embodiment of FIG. 12;

[Explanation of symbols]

 10, plastic pipe with receptacle 12, 14 ... pipe 16 ... receptacle 18 ... heater 20, 48 ... core pin 32 ... cartridge heater 34 ... water channel 38 ... work coil 44 ... end 66 ... outer mold

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-281079 (JP, A) JP-A-63-272535 (JP, A) JP-A-58-201610 (JP, A) JP-A 53-2016 40080 (JP, A) JP-A-2-194925 (JP, A) JP-A-55-42821 (JP, A) JP-A-3-118624 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 57/00-57/12 F16L 47/00

Claims (5)

(57) [Claims] 1. A step of preparing a pipe made of a polyolefin-based resin, a step of mounting a fusion heater around an outer periphery of a core pin, and a step of heating an end of the pipe to a vicinity of a softening point. (D) heating the core pin above the melting point of the pipe, (e) inserting the core pin into the end, (f) cooling the end and the core pin,
And (g) a method for molding a plastic pipe with a socket, comprising the step of removing the core pin. 2. Before inserting the core pin into the end,
The method of molding a plastic pipe with a receiving port according to claim 1, wherein an outer mold is placed outside the core pin. (A) preparing a pipe made of a polyolefin-based resin; (b) mounting a welding heater on the outer periphery of the core pin; (c) heating an end of the pipe to a melting point or higher; (d) heating the core pin near the softening point of the pipe, (e) inserting the core pin into the end, (f) covering an outer surface of the end with an outer mold, (g) A method of molding a plastic pipe with a socket, comprising: cooling an end portion and the core pin; (h) removing the outer mold; and (i) removing the core pin. 4. Before inserting the core pin into the end,
4. The method of molding a plastic pipe with a receiving port according to claim 3, wherein the outer mold is placed outside the core pin. 5. The method according to claim 1 or 3, wherein
The plus with socket according to any one of claims 1 to 4, wherein the core pin is heated by inducing a high-frequency current from a work coil to the core pin .
Tick pipe forming method .