JPH079480A - Manufacture of cap for blocking cap - Google Patents

Abstract

PURPOSE:To provide a manufacturing technique capable of easily producing a cap for blocking a pine with a heating wire embedded in an outer peripheral surface of a thermoplastic resin-made cylindrical body having a closed end and with a pair of conduction terminals provided on the end face thereof on a mass production base and to prevent an occurrence of an exposure of a connection part between the heating wire and the conduction terminal, a short circuit accident, and the like. CONSTITUTION:A coil heating body 6 is obtained by spirally winding a resin- coated Nichrome wire around an outer peripheral surface of a cylindrical core, fusing and fixing the coating resin, and removing the core. Conduction terminals 4 are connected to the coil heating body 6. Thereafter, the coil heating body 6 is securely fitted into a groove-form holding part 63 provided between two ring-form ribs 62 projected on an inner peripheral cavity surface 61 of a mold. The conduction terminals are fitted with fixing pins 65 projected on an end ring 64. Thereafter, a melt resin is injected to be charged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe line closing cap used for closing a pipe line of a water and sewer pipe or a gas pipe made of a thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, as a pipe line closing cap for closing a pipe line of a water and sewer pipe or a gas pipe made of a thermoplastic resin, an electric fusion plug described in JP-A-3-81494, a design registration As in the tube end protection cap described in Japanese Patent No. 841165, a spiral heating wire is provided on the inner peripheral surface of a thermoplastic resin cylindrical body whose one end is closed, and the outside of the end of the tube to be closed It is known that a heating wire is heated by energization to heat the heating wire, and the inner peripheral surface of the synthetic resin pipe joint and the outer surface of the end portion of the pipe to be closed are heat-fused and integrally closed.

Further, the present inventors have previously shown that a spiral heating wire C is provided on the outer peripheral surface of a thermoplastic resin cylindrical body B having one end closed, as shown in FIG. A pipe closing cap A (1993 patent application No. 10719) in which an energizing terminal D is provided on an end surface of a cylindrical body B is proposed. The pipe line closing cap A is fitted inside the end portion of the pipe to be closed, heats the heating wire C by energization, and the end face of the pipe to be closed with the outer peripheral surface of the pipe line closing cap A. The inner surface and the inner surface are heat-fused and closed.

By the way, in the case of manufacturing the electric fusion plug described in Japanese Patent Laid-Open No. 3-81494 and the pipe end protection cap described in Japanese Patent Registration No. 841165, in which a spiral heating wire is provided on the inner peripheral surface, A method of spirally winding a resin-coated heating wire that has been surface-coated with synthetic resin around the core of an injection mold, inserts the core into the cavity of the injection mold, and injects and fills the molten resin for molding. It has been done conventionally.

However, in the manufacture of the tube end protection cap A having the spiral heating wire C provided on the outer peripheral surface as shown in FIG. 9, the heating wire C is injected prior to injection and filling of the molten resin.
Is wound around the inner surface of the injection molding die in a suspended state without a support, or the spirally wound heating wire and energization terminal D while paying attention to uniform heat generation and avoiding a short circuit. It is necessary to keep the inside of the cavity of the injection mold, but it is not technically established yet.

After molding the thermoplastic resin cylindrical body B,
The heating wire C can also be manufactured by a method of spirally winding the heating wire C on the outer peripheral surface thereof, but the connecting portion between the heating wire C and the energization terminal D is exposed, or the energization terminal D is connected to the thermoplastic resin cylindrical body B. Since the fixation is uncertain, mass production is difficult, and it is the current situation that only handmade sample products can be made.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, in which a heating wire is embedded in the outer peripheral surface of a thermoplastic resin cylindrical body whose one end is closed, and the end surface is It is an object of the present invention to provide a method for manufacturing a conduit block cap, which allows a conduit block cap provided with a pair of energizing terminals to be easily manufactured on a mass production basis.

Further, the connection between the heating wire and the current-carrying terminal is not exposed and the current-carrying terminal is not uncertainly fixed, and there is no short-circuit accident of the heating wire due to the current supply, and it can be used safely and reliably. The purpose of the present invention is to provide a cap for blocking a duct.

[0009]

In order to achieve the above object, in the method for manufacturing a conduit closing cap of the present invention, a heating wire is embedded in the outer peripheral surface of a thermoplastic resin cylindrical body whose one end is closed. A method for manufacturing a pipe line closing cap having a pair of energization terminals provided on an end surface, wherein a resin-coated heating wire coated with a thermoplastic resin is spirally wound around a cylindrical core-shaped outer peripheral surface and coated. Heat and melt the resin,
A process of manufacturing a coil-shaped heating element by fusing and fixing resin-coated heating wires together, a step of releasing the coil-shaped heating element from the core mold, and connecting energizing terminals to both ends of the heating wire, and energizing terminals are connected. The coiled heating element is fitted and fixed to the shallow groove-shaped holding part provided on the inner peripheral surface of the cavity of the injection mold, and the energizing terminal is fitted to the fixing part protruding from the end surface of the cavity. It is characterized by including a step of combining and fixing and a step of injecting and filling a molten resin into the cavity.

In the present invention, the thermoplastic resin cylindrical body is made of a general-purpose thermoplastic resin such as polyethylene, polypropylene or vinyl chloride resin, or an engineering plastic such as polyvinylidene fluoride or polyphenylene sulfide.

As the heating wire, a nichrome wire, a copper-nickel alloy wire, a carbon fiber or the like which generates heat by electricity, or a wire which generates heat by a high frequency current is used.

The resin for coating the resin-coated heating wire is preferably the same thermoplastic resin as the thermoplastic resin cylinder, but any resin having a good compatibility therewith may be used. The resin-coated heating wire can be produced by a known electric wire coating extrusion molding using a crosshead mold.

[0013]

The method for manufacturing a pipe line closing cap according to the present invention comprises the step of spirally winding a resin-coated heating wire around an outer peripheral surface of a cylindrical core mold,
The coating resin is heated to fuse the resin-coated heating wires to each other to produce a coil-shaped heating element, and the coil-shaped heating element connected to the current-carrying terminal is inserted into the cavity of the injection molding die to form a coil. The heating element and the energization terminal are held, and then the molten resin is injected and filled into the cavity.

Therefore, since the heating wires are spirally wound at a certain interval without making contact with each other, there is less risk of short circuit, and it is easier than when the electric heating element is wound directly on the inner surface of the cavity. The molding cycle time is also shortened.

As means for holding the coil-shaped heating element, the coil-shaped heating element is fitted and fixed to a holding portion provided on the inner peripheral surface of the cavity of the injection molding die, and the holding portion has a shallow groove. Because of the shape, the coil-shaped heating element can be loaded and fitted into the mold without difficulty, and moreover, the coil-shaped heating element can be held without coming off due to the injection pressure at the time of injecting the molten resin. Also,
Since the holding portion is in the shape of a shallow groove, there are few undercuts. Therefore, excessive removal of the product is not required when the product is released from the mold, and the product or the mold is not damaged.

As a means for holding the energizing terminal, since it is fitted and fixed to a fixing portion projecting on the end face portion in the cavity, it is held without being disengaged by the injection pressure of the molten resin, and the energizing terminal is held. Is always projected at a fixed position on the end face of the thermoplastic resin cylindrical body, and the product in which the connecting portion between the heating wire and the current-carrying terminal is not exposed is buried is obtained.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 (a) is a cross-sectional view showing an example of a conduit closing cap manufactured by the method of the present invention, and FIG. 1 (b) is a side view thereof.

In the pipe line closing cap 1 shown in FIG. 1, a nichrome wire is spirally wound and embedded as a heating wire 3 on the outer peripheral surface of a thermoplastic resin cylindrical body 2 having one end closed. Both ends of the heating wire 3 are electrically connected to the energization terminal 4 projecting from the end surface of the thermoplastic resin cylindrical body 2, and when a voltage is applied to the energization terminal 4, a current flows through the heating wire 3 to heat it. Then, the outer peripheral surface of the thermoplastic resin cylindrical body 2 is heated and melted, and further, the inner surface of the thermoplastic resin pipe P that is in contact with the outer peripheral surface of the thermoplastic resin cylindrical body 2 is also melted, and the pipe line closing cap 1 and The plastic resin pipe P is adapted to be fused.

2 (a) is a front view showing a state in which the resin-coated nichrome wire 3a is spirally wound around the outer peripheral surface of the core die 50 in the manufacturing process of the coil-shaped heating element in the method of the present invention, FIG. 2B is a front view showing a state in which a current-carrying terminal is connected to the coil-shaped heating element manufactured by the method of FIG. 2A, and FIG. 3 shows a state in which the coil-shaped heating element and the current-carrying terminal are fixed to an injection molding die. It is a schematic diagram which shows.

As shown in FIG. 2A, the cylindrical core die 50 formed so as to be capable of expanding and contracting the diameter is set in the winding machine in the expanded state, and the thermoplastic resin cylindrical body 2 is set. The resin-coated nichrome wire 3a coated with the same type of resin as above is spirally wound around the outer peripheral surface of the core die 50, and hot plates heated to a temperature equal to or higher than the melting temperature of the coating resin are applied to a plurality of positions on the surface to cover the coating resin. Is melted, fused and fixed at the band-shaped fusion-bonding portion 5, and then the core die 50
Is contracted, and the coil-shaped heating element 6 is released and taken out.

Next, as shown in FIG. 2 (b), the core die 5
The end portions 3a1 and 3a2 of the resin-coated nichrome wire 3a of the coil-shaped heating element 6 taken out from 0 are folded back from the inner surface side of the coil-shaped heating element 6 and pulled out, and the energization terminal 4 (recessed type in the example of FIG. 2B) Stuff) is connected by a method such as welding or caulking.

Next, the coil-shaped heating element 6 having the energization terminals 4 connected to both ends is manually fixed to the injection molding die.
As shown in FIG. 3, on the inner peripheral surface 61 of the cavity 60 of the injection mold, the wire diameter of the resin-coated nichrome wire 3a is approximately 1 mm.
/ 2 to 1 times the height of the annular rib 62 having a low height is provided in two projections, whereby a holding portion 63 in the form of a shallow groove is formed while being sandwiched between the two annular ribs 62. The outer peripheral surface and the end surface of the coil-shaped heating element 6 are fitted and fixed to the holding portion 63.
Since the coil-shaped heating element 6 has a thin cylindrical shape, it can be deformed to some extent in the diametrical direction, and since it is resin-coated, the inside of the cavity 60 is slightly deformed and slid,
It can be easily fitted and fixed to the holding portion 63.
Also, the end ring 64 that forms the end of the cavity 60.
The energizing terminal 4 is fitted and fixed to the two fixing pins 65 protrudingly provided on the inner surface side of the.

The annular rib 62 is used as the coil-shaped heating element 6.
It is preferable to have a cross-sectional shape such that the inner end of the groove-shaped holding portion 63 rises vertically from the inner peripheral surface 61 of the cavity 60 so as to be securely fixed.

Then, in this state, the end ring 64 is closed,
The movable die is advanced to insert the core 70 into the cavity 60, and the molten resin is injected and filled into the cavity 60.

When the movable die retracts after cooling the molded product, since the annular rib 62 has a low height substantially the same as the wire diameter of the resin-coated nichrome wire 3a, it is only slightly forced to remove the product. Is withdrawn along with the core 70 with the end ring 64 attached and falls. Then, the end ring 64 is removed by hand to obtain a product for a conduit closing cap.

FIG. 4 is a sectional view showing another example of the coil-shaped heating element, in which the coating resin of the resin-coated nichrome wire 3a folded back toward the inner surface is peeled off, and instead that portion is covered with a heat-resistant insulating tube 7. It is coated.

Since the nichrome wire at the folded portion is covered with the heat-resistant insulating tube 7 in the conduit closing cap manufactured by using the coil-shaped heating element 6a, the covering resin is melted and expanded by the energization. Or even if the nichrome wire moves, it does not come into direct contact with the coiled nichrome wire, and a short circuit accident can be prevented.

FIG. 5A is a sectional view showing still another example of the coil-shaped heating element, and FIG. 5B is a side view. The coil support 8 molded from the same resin as the thermoplastic resin cylinder 2 is
Cylindrical portion 81, and at both ends thereof, a flange portion 82 having a low height, which is approximately 1/2 to 1 times the diameter of the resin-coated nichrome wire 3a, and a joint portion with each of the flange portions 82 of the cylindrical portion 81. Insertion holes 83 and 84 having a diameter through which the resin-coated nichrome wire 3a can pass are formed in the hole.

The coil support 8 is supported in a state in which a cylindrical core mold capable of expanding and contracting the diameter is expanded, and this is set on a winding machine to mount the resin-coated nichrome wire 3a on the cylindrical portion 81. Wrap around the outer peripheral surface and melt the coating resin in the same manner as in the above example.
After fixing, the diameter of the cylindrical core mold is reduced, and the coil support body 8 is taken out. Next, one end 3 of the resin-coated nichrome wire 3a
a3 is inserted from the insertion hole 83 to the inner surface side of the support 8 and folded back, and then the other end 3a4 of the resin-coated nichrome wire 3a is inserted from the insertion hole 84 to the inner surface side of the support 8 to form the coil-shaped heating element 6b. Obtained and resin-coated nichrome wire 3 in the same manner as above
The energizing terminal 4 is connected to the ends 3a3 and 3a4 of a.

Next, a method of manufacturing a pipe line closing cap using the coil-shaped heating element 6b thus obtained will be described. FIG. 6 is a schematic view showing a state in which the coil-shaped heating element shown in FIG. 5 is fixed to an injection molding die. As shown in FIG. 6, on the inner peripheral surface 61a of the cavity 60a of the injection molding die, approximately 1/1 of the wire diameter of the resin-coated nichrome wire 3a is provided.
A shallow annular groove 63a having a depth of 2 to 1 times is formed, and the annular groove 63a serves as a holding portion.

The coil-shaped heating element 6b to which the current-carrying terminal 4 is connected is fitted and fixed in the annular groove 63a, and the current-carrying terminal 4 is fixed to the fixing pin 65 protruding from the inner surface of the end ring 64. After fitting and fixing, a pipe line closing cap is manufactured in the same manner as in the above-mentioned embodiment.

The pipe line closing cap manufactured by using the coil-shaped heating element 6b is strong because the resin-coated nichrome wire 3a is supported by the coil supporting body 8, and the annular groove 6 is used.
It is unlikely to lose its shape or deform due to fitting into 3a or injection pressure of molten resin. Further, since the coil-shaped nichrome wire and the folded nichrome wire are separated by the cylindrical portion 81, the coating resin melts and expands by energization, or even if the nichrome wire moves, the nichrome wire directly contacts the coil-shaped nichrome wire. It is possible to prevent a short circuit accident.

FIG. 7 (a) is a front view showing another example of the coil support used for the coil-shaped heating element, and FIG. 7 (b) is FIG.
It is sectional drawing in the XX line of (a). The coil support body 8a includes insertion holes 83 in the coil support body 8 of FIG.
Instead of 84, notches 85 and 86 having a width through which the resin-coated nichrome wire can pass are provided in the flange 82a.

FIG. 8A is a sectional view showing still another example of the coil support, and FIG. 8B is a side view. The coil support 8b has an insertion hole 83 similar to that shown in FIG.
a and 84a are bored, and a pedestal 8 is provided on the inner surface.
7 is provided, and a pedestal 87 is formed with a cut 88 into which a resin-coated nichrome wire is fitted.

The resin-coated nichrome wire inserted through the insertion hole 83a to the inner surface side of the coil support 8b is fitted into the notch 88 of the pedestal 87 to support the resin-coated nichrome wire. Since it is supported at a certain distance from, a short circuit accident with the coiled nichrome wire is reliably prevented.

[0036]

As is apparent from the above description, according to the method of the present invention, the heating wire is embedded in the outer peripheral surface of the thermoplastic resin cylindrical body whose one end is closed, and the pair of current-carrying terminals are provided on the end surface. The cap for blocking a pipeline can be easily manufactured on a mass production basis by using a simple manufacturing apparatus.

Further, the produced pipe closing cap is
Since the connection between the heating wire and the energizing terminal is not exposed or the fixing of the energizing terminal does not become uncertain, and a short-circuit accident of the heating wire is prevented, it can be used safely and reliably.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing an example of a conduit closing cap manufactured by the method of the present invention, and FIG. 1B is a side view.

2A is a front view showing a coil-shaped heating element manufacturing process in the method of the present invention, and FIG. 2B is a front view showing a state in which an energization terminal is connected to the coil-shaped heating element of FIG.

FIG. 3 is a schematic view showing a state where the coil-shaped heating element of FIG. 2 is fixed to an injection molding die.

FIG. 4 is a cross-sectional view showing another example of a coil-shaped heating element.

5A is a sectional view showing still another example of a coil-shaped heating element, and FIG. 5B is a side view.

FIG. 6 is a schematic view showing a state in which the coil-shaped heating element shown in FIG. 5 is fixed to an injection molding die.

FIG. 7A is a front view showing another example of the coil support, and FIG. 7B is a sectional view taken along line XX of FIG.

8A is a sectional view showing still another example of the coil support, and FIG. 8B is a side view.

FIG. 9A is a cross-sectional view showing an example of a pipe line closing cap of the prior invention, and FIG. 9B is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cap for pipe closing 2 Cylindrical body made of thermoplastic resin 3 Heating wire 3a Resin-coated nichrome wire 4 Energizing terminal 5 Fusion part 6,6a, 6b Coil-shaped heating element 8,8a, 8b Coil support 81 Cylindrical part 82 Collar part 83,84 insertion hole 85,86 notch portion 50 core type 60,60a cavity 61,61a inner peripheral surface 62 annular rib 63 retaining portion 63a retaining portion (annular groove) 64 end ring 65 fixing pin

Claims (1)

[Claims] 1. A method for manufacturing a pipe line closing cap in which a heating wire is embedded in an outer peripheral surface of a thermoplastic resin cylinder whose one end is closed, and a pair of energizing terminals are provided on the end surface, the thermoplastic line closing cap comprising: A resin-coated heating wire coated with resin is spirally wound around the outer peripheral surface of a cylindrical core, and the coated resin is heated and melted,
A process of manufacturing a coil-shaped heating element by fusing and fixing resin-coated heating wires together, a step of releasing the coil-shaped heating element from the core mold, and connecting energizing terminals to both ends of the heating wire, and energizing terminals are connected. The coiled heating element is fitted and fixed to the shallow groove-shaped holding part provided on the inner peripheral surface of the cavity of the injection mold, and the energizing terminal is fitted to the fixing part protruding from the end surface of the cavity. A method for manufacturing a pipe line closing cap, comprising: a step of combining and fixing and a step of injecting and filling a molten resin into a cavity.