JPH0389095A - Thermoplastic pipe joint and manufacture thereof - Google Patents

Abstract

PURPOSE:To perform thermal fusion simply and easily by double coiling a wire material along the inner surface of a heater generating body which wire material is made by coating a conductor material with a ferromagnetic material layer. CONSTITUTION:Pipes 10, 10 to be joined are inserted into a pipe joint 12. A heat generating wire material 14 is embedded in the shape of a double coil on the inner surface of the pipe joint 12. The heat generating body 14 is a wire material made by coating a conductor material with a ferromagnetic material layer. The pipe joint 12 is formed by winding a heat generating wire material 32 embedded in a plastic layer of a thermoplastic resin tape 30 together with the tape 30 around a mandrel 34, and thermoplastic resin is made to flow into the gap between the mandrel 34 and an outer frame arranged with a gap between the mandrel 34. As a result, heating temperature may be automatically controlled with the Curie point of the ferromagnetic material as a reference. Deformation of the pipe joint is prevented by the surface effect.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermoplastic resin pipe joint and a method for manufacturing the same, in particular, to connect thermoplastic resin pipes by heat fusion using the Curie temperature. The present invention relates to a thermoplastic resin pipe joint equipped with a heating element that automatically adjusts the heating temperature, and a method for manufacturing the same.

(Conventional technology) Resin pipes have become rapidly popular due to their advantages such as being lightweight, easy to handle, and have excellent corrosion resistance.As a result, various proposals have been made for pipe joints that connect pipes. is being done. Some connection means use adhesive, but in the case of thermoplastic resin pipes, heat fusion is said to be a simple means.

In this case, a pipe joint in which a heating means is embedded in advance is used.

For example, as proposed in Japanese Utility Model Publication No. 62-22712, a heating element, that is, a heating wire, is installed on the inner periphery of a thermoplastic resin tube, and after the tube is inserted, the heating element is energized to generate heat, thereby joining the tube. Joints for connecting resin pipes that fuse parts together are well known. Also JIS K67751989 r
Fittings with heating wires are also specified in ``Polyethylene Pipe Fittings for Gas.''

In addition, regarding pipe fittings with internal heating elements,
It is described in No. 2-107192, No. 62-172894, No. 62-151688, etc.

(Problems to be Solved by the Invention) However, the following problems are pointed out in all of these conventional methods.

(1) The power source is DC or low frequency AC power.

(2) Since it is difficult to set the fusion conditions, it is necessary to manually set the voltage and heating time, or to provide an automatic setting function.

(3) Since the input from the power source is supplied to the heating element through the terminal, it is necessary to make a terminal part when molding the pipe joint, and the lead wire from the heating element built inside the pipe joint must be drawn out to the terminal. The structure is also structurally complex, as it needs to be created during molding.

By the way, as a method for installing a heating wire inside the inner surface of a pipe joint, a cylindrical wire material coated with resin is wound around a mandrel, an outer frame is provided at a certain distance from the mandrel, and resin is filled in the gap. There is a method of manufacturing resin pipes by injection molding, but in this method, a cylindrical resin-coated wire is wound around a mandrel and the joint is then formed by injection molding.Resin is poured in at high pressure during injection molding. Sometimes, the wire rods are not fixed in a predetermined position due to the pressure, and the spacing between the wires and the interior depth from the inner surface of the pipe joint become uneven. Therefore, if the heating temperature when joining the joint and the pipe to be joined becomes uneven, or if the distance between the wires is too narrow, the resin covering the heating elements will melt during heating, and the heating elements will come into contact with each other, resulting in cycoat. Excessive current may flow and the resin may melt locally, affecting the quality of the joint.

Therefore, an object of the present invention is to provide a pipe joint for connecting thermoplastic resin pipes by heat fusion, which allows heat fusion to be performed simply and easily, and a method for manufacturing the same. be.

A more specific object of the present invention is to provide a highly reliable pipe joint that allows easy control of heating temperature and a method for manufacturing the same.

Another object of the present invention is to provide a highly reliable pipe joint in which a heating element built into the inner surface of a thermoplastic resin pipe is placed at a predetermined position and does not cause local overheating even when heated, and a method for manufacturing the same. It is to provide.

(Means for Solving the Problems) In order to achieve the above-mentioned purpose, the present inventor has made various studies,
We focused on the automatic temperature control characteristics at the cue point observed during high-frequency heating of ferromagnetic materials.

In other words, high-frequency current has a skin effect.
A phenomenon in which a current called ct) is concentrated on the surface is observed,
As a result, Joule heat generation at the surface increases.

On the other hand, when the temperature exceeds the cue point, the magnetic permeability of the ferromagnetic material decreases, the skin effect is lost, and the current flows in a dispersed manner deep within the body, resulting in a rapid decrease in the generation of Joule heat, and eventually This is where the automatic temperature control function comes into play.

Heating means that utilize such an automatic temperature control function are disclosed, for example, in Japanese Patent Publication No. 500166/1983 and Japanese Patent Publication No. 32938/1982, but in both cases, a block is used to ensure sufficient heat generation. This method uses a heat generating element that has been converted into a heat generating element, and therefore cannot be used for the purpose of the present invention.

Therefore, the inventor of the present invention conducted further studies and found that it is possible to secure the required amount of heat for a pipe joint in which a heating element made of such a wire is embedded even when the above-mentioned block body is used as a wire, and that by using a double-coated wire. Constant temperature characteristics can be ensured even when embedded in resin, automatic temperature control can be achieved by adjusting the Curie point by changing the string of the covering material, and furthermore, when winding the heating element in a spiral shape, it can be wound twice. The present invention was completed based on the knowledge that the current efficiency could be further improved by this method.

In the case of Fe-Ni alloys, the Curie temperature can be changed in the range of 100 to 500°C by adjusting the alloy composition, which corresponds to the melting temperature range of many thermoplastic resins. , is advantageous in this respect.

Here, the present invention is a thermoplastic resin pipe joint having a heating element inside the inner surface, the heating element being made of a wire made of a conductive material coated with a ferromagnetic layer in a double helical shape. This is a special plastic resin pipe joint characterized by being rolled.

Note that "interior" refers to embedding near the inner surface of the pipe that constitutes the joint.

Moreover, as already mentioned, it is difficult to obtain a pipe joint equipped with the above-mentioned heating element wire at a predetermined position by injection molding. Moreover, type 2 winding cannot be easily realized.

Therefore, the inventor of the present invention also considered a means for embedding the heating element wires, and found that by burying the heating element wires in pairs in a tape-shaped resin layer in advance, and connecting the reheating element wires at least at one end, two I learned that if the wire is heavily wound and fixed by wrapping the tape around the mandrel, the wire will not shift during injection molding.

Therefore, another aspect of the present invention is to embed a pair of linear heating elements in the resin layer of a thermoplastic resin tape and connect them at least at one end, and to spirally wrap the tape around a mandrel. After that, the outside of the mandrel,
This method of manufacturing a thermoplastic resin pipe joint is characterized in that a thermoplastic resin is poured between the pipe joint and an outer frame provided at a predetermined interval using, for example, injection molding means.

There are many ways to wind the linear heating element with the two-type winding described above, but the most common method is to wind it twice in a spiral shape along the inner surface of the tube in the longitudinal direction. It is also possible to wrap it twice in a spiral shape while also winding it in a wave shape.

Alternatively, the heating element wire may be wound not over the entire inner surface of the joint, but only around the part to be heat-sealed to the pipe to be joined.

When utilizing the automatic temperature control characteristic of the ferromagnetic material described above, the linear heating element is a wire made of a conductive material coated with a ferromagnetic layer.

In order to connect thermoplastic resin pipes using the pipe joint according to the present invention, after assembling the pipe joint part, a high frequency current, for example, a high frequency current of 8 to 20 MHz, is supplied to the heating element from an external power supply as appropriate. Alternatively, the above-described high-frequency current may be induced in the heating element by an induction method.

In particular, the high frequency induction method has the advantage that it is not necessary to provide lead wires, terminal parts, etc. to the pipe joint, the structure is simple, and manufacturing is very easy.

(effect) Next, the configuration of the present invention will be explained in further detail.

Here, FIG. 1 is a schematic perspective view showing a cross section of a thermoplastic resin pipe joint according to the present invention.

In the figure, the pipe to be joined 10.10 is inserted into the pipe fitting 12. A heating element wire 14 is spirally housed inside the pipe joint 12 . The heating element wire 14 may be completely buried within the pipe joint 12, or may be provided so as to be partially exposed on the inner surface. In order to prevent the wires constituting the heating element from breaking, it is preferable that the wires are slightly buried as shown in the figure.

FIG. 2 is a schematic explanatory diagram showing the winding shape of the heating element wire at this time, and is arranged in a double spiral shape in the longitudinal direction along the inner surface of the joint pipe.

- When a high-frequency current is applied to a type-wound heating element, the impedance increases and the resistance increases, so current will no longer flow through the heating element unless a large voltage is applied.

However, by using two-type winding, current flows in opposite directions in adjacent wires, so the impedances cancel each other out and the resistance does not increase, so heat can be generated efficiently even at low voltages.

In the present invention, the heating element is a wire made of a conductive material coated with a ferromagnetic layer, and the reason for such a configuration is as follows.

That is, a ferromagnetic material has high magnetic permeability below its cue temperature, but its magnetic permeability is about 1 above that temperature. Therefore, at temperatures below the queuing point, when using a high-frequency power supply, the high-frequency current of the ferromagnetic material is concentrated on the outer circumference, and the current density is maximum at the surface of the ferromagnetic material.The skin effect generates Joule heat, which causes strong The resin near the magnetic material is heated and melted.

On the other hand, at temperatures above the cue point, the magnetic permeability is almost the same as that of the conductor, so the skin effect is not obtained and the Joule heat decreases. Therefore, by using the heating element as a wire made of a conductive material coated with a ferromagnetic layer, the heating temperature can be automatically controlled at the Curie temperature of the ferromagnetic material.

That is, this ferromagnetic material loses its magnetism when the temperature exceeds the Curie point, and when an induction method is adopted, the induced current stops flowing, heat generation stops, and self-temperature control is achieved.

Note that when a high-frequency current is supplied from an external power source, the skin effect is lost and no Joule heat is generated.In fact, the thermal curve rapidly decreases due to heat conduction by the internal conductive material, and the constant temperature effect is lost. work.

In addition, since the area heated due to the skin effect is narrow, the area where the resin is melted can be narrowed, thereby preventing the pipe joint from deforming due to heating.

The high-frequency current may be supplied to the heating element by providing lead wires at both ends of the heating element or from an external power supply, or by generating a high-frequency induced current without providing lead wires. When supplying current from an external power source, one end of the double winding described above may be connected, but in the case of a system in which an induced current flows, both ends are connected. Note that the state of the connections is not shown in Figure 1 to simplify the drawing.

In this way, in the present invention, by using a heating method that induces a high-frequency current, the lead wire of the heating element is no longer necessary because the induced current is passed from outside the pipe joint without contact.
Molding of pipe fittings is also particularly advantageous as there is no need to add extra structures such as forming terminals.

Next, a method for manufacturing a pipe joint according to the present invention will be described, and it is particularly preferable to manufacture the pipe joint in the following manner.

In addition, in the manufacturing method according to the present invention, in principle, the heating element does not necessarily have to have the above-mentioned composite structure, and even a conventional heating element can achieve the desired effect. When using a composite wire in which a conductive material is coated with a ferromagnetic layer as in the present invention, its characteristics are particularly effectively exhibited.

That is, according to the method for manufacturing a pipe joint according to the present invention,
A heating wire made of a conductive material coated with a ferromagnetic layer is embedded in a tape-shaped thermoplastic resin in pairs and at least one end is connected, and then the tape with the wire embedded therein is wound in a spiral around a mandrel. This allows the heating wire to be wound twice on the mandrel with a uniform thickness without any gaps.

In FIG. 3, heating element wires 32 embedded in pairs in the resin layer of a thermoplastic resin tape 30 are wound around a mandrel 34 together with the tape. In the case of Fig. 3, the side surface is sloped 38 to prevent it from rising when it is wrapped.
The tapes 30 and 30 on both sides overlap each other.

For double spiral winding, it is not necessarily necessary to use wires buried in pairs within the tape; for example, two single wires may be wound in parallel and at least one end thereof connected.

It is also possible to first prepare a tape with the heating element wire embedded therein and wrap it around a mandrel;
By winding it directly around a mandrel, adjacent tapes may be thermally fused to each other, and a resin layer in which a spiral heating element is embedded may be formed without any gaps.

By adopting such a configuration, the position of the tape will not shift even if the thermoplastic resin is poured under high pressure in subsequent injection molding, and therefore the heating wire can be placed inside the pipe joint at a predetermined position and a predetermined depth. I can do it.

In a pipe joint with a heating element installed in this way,
The position of the heating element wire becomes constant, the structure is more reliable, and overheating due to uneven heating or short circuits can be effectively prevented.

The thermoplastic resin used in the present invention is, for example, a polyolefin resin or a vinyl chloride resin, and is not limited to a specific one as long as it can be heat-sealed after being molded into a pipe joint.

A wire made of a conductive material or a wire coated with a ferromagnetic material is buried in the inner surface of the tube. Examples of such conductive materials include copper, silver, and aluminum, but these are not limited to any particular material.

If the conductive material wire is too thick, a step may form during molding, or a step may form at the resin joint due to the difference in thermal expansion coefficient between the resin and the wire during heating and cooling, reducing the strength of the joint. Therefore, the diameter is preferably about 0.2 to 1.5 nm+m.

Further, the cross-sectional shape of the wire may be not only circular but also oval, rectangular, or the like.

A ferromagnetic layer is provided on the wire of such conductive material, and is heated by a high-frequency current supplied from an external high-frequency power supply, or placed inside a high-frequency induction coil and induced by an induction method. heated by high-frequency current. Examples of such a ferromagnetic material include iron, nickel, cobalt, etc., but a Ni--Fe alloy of 36% nickel and balance iron is preferable for heating resin pipes. The cue point of this alloy is approximately 280℃, and the effective magnetic permeability is 100 to 300.
It is.

Further, the thickness of the ferromagnetic layer is preferably thin in order to increase heating efficiency, and is usually preferably 100 μm or less.

Such a composite conductor can be manufactured, for example, by making a clad ingot using a casting method, rolling it into a rod shape, and then drawing it.

Since this point is already well known as a method for manufacturing clad wires, no further explanation will be necessary for those skilled in the art.

If the distance between the double-wound wires and the distance between the heating element wires on both sides are too large, the heating efficiency will decrease and the bonding strength will decrease. On the other hand, if it is too small, there is a risk of short circuiting and overheating when the resin is heated and melted. The spacing between the wire rods is preferably about 1 to 3 mm when the wire rod thickness is 0.5 mm.On the other hand, the spacing between the adjacent winding wires on both sides depends on the thickness of the wire rod itself, but when the wire rod thickness is 0.5 mm. When it is 5 mm, a value of 1 to 31 is appropriate.

If the interior depth from the inner surface of the pipe joint is deep, the heating efficiency will decrease and the joint strength will decrease. On the other hand, if it is too shallow, the wire may come out to the inner surface during heating and melting, reducing the bonding strength.
m, the distance between the pipe joint and the center of the wire is 0.5 to 1.
Approximately 51 is appropriate.

When using a tape in which heating element wires are embedded in advance as described above, the positional relationship between the tapes can be precisely controlled, so that the spacing can be made considerably narrower.

Here, a method for manufacturing a resin pipe joint according to the present invention will be explained.

A wire rod formed by coating a ferromagnetic layer on a conductive material that has been shaped in advance by an appropriate method such as a method for manufacturing a clad wire rod is further placed in a tape-shaped thermoplastic resin layer, preferably in pairs, by extrusion molding, for example. Embed and wrap the resulting tape around a mandrel in a spiral. The width and thickness of this tape are determined by the installation interval and depth of the wire rods. In terms of material, it may be made of thermoplastic material, for example, the same material as the pipe joint. The shape of the tape should be such that it can be wrapped around the mandrel with a uniform thickness without any gaps.For example, by using a tape with the shape shown in Figure 3, the pressure of pouring the resin during injection molding will allow the wire to be rolled. The position will not shift,
On the inner surface of the pipe joint, the wire can be placed at a predetermined position and at a predetermined depth. Thereby, it is possible to prevent overheating due to non-uniform heating and short circuits when joining the tubes.

Next, the present invention will be explained in further detail with reference to examples thereof.

Example After a polyethylene tape covering two wire rods having the shape shown in Fig. 3 is wound spirally around a mandrel, a polyethylene resin tape is placed between it and an outer frame installed at a predetermined interval on the outside of the mandrel. was poured by injection molding to form the first
The pipe joint shown in the figure was manufactured. The appearance of the two-type winding of the wire rod at this time was as shown in FIG. Both ends were connected.

At this time, the wire rod embedded in the resin had a core material of copper, which was coated with an alloy layer of 36% nickel and balance iron with a thickness of 30 μm, and had a diameter of 0.5 mm. The spacing between the wire rods was 2.5 mm, and the depth from the inner surface of the pipe joint was 0.5 mm at the center of the wire rods.

As shown in FIG. 1, a polyethylene resin pipe was inserted into this pipe joint, and the heating element wire was heated in a non-contact manner using a 13 MHz high frequency induction method to join the pipes. The bonding conditions were as shown in Table 1.

In order to check the adhesion status after joining, the joint was cut in half and the joint and pipe were reliably joined by heat fusion, and no deformation of the joint was observed.

High frequency type g: 13MIIz, IKW, constant current type Heating time: 3 minutes Maximum heating temperature: 280°C (Effects of the invention) As described above, according to the present invention, the following effects can be obtained. .

(1) The heating temperature can be automatically controlled with the Curie temperature of the ferromagnetic material as the boundary.

(2) Deformation of the pipe joint can be prevented because the range heated by the skin effect is narrow.

(3) If a high-frequency induction heating method is used, a lead wire for the heating element is unnecessary, and there is no need to add extra structures such as terminals to the pipe joint.

(4) By further embedding the wire in a tape-shaped thermoplastic resin, it is possible to wrap it around the mandrel with a uniform thickness without any gaps, and even after pouring the thermoplastic resin, the heating element wire can be kept at a predetermined position and at a predetermined depth. It can be installed inside pipe joints to prevent overheating due to uneven heating or short circuits.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view illustrating the pipe joint according to the present invention and how it is used to connect double-wave joint pipes; Figure 2 is a wire coated with a ferromagnetic material that constitutes a heating element. FIG. 3 is a schematic explanatory diagram showing the form of a two-shaped winding of conductive material; and FIG. 3 is a schematic explanatory diagram showing the form of a resin tape in which a heating element wire is embedded. 10: Pipe to be joined 12: Pipe joint 14: Heating element wire 30: Thermoplastic resin tape 32:
Heating element wire 34: Mandrel 38: Slope

Claims (2)

[Claims] (1) A thermoplastic resin pipe joint with a heating element built into the inner surface, the heating element being a wire made of a conductive material coated with a ferromagnetic layer in a spiral shape along the inner surface. A thermoplastic resin pipe joint characterized by being double-wound. (2) A pair of wires made of a conductive material coated with a ferromagnetic layer is embedded in the resin layer of a thermoplastic resin tape and connected at least at one end, and the tape is spirally wound around a mandrel. 1. A method for manufacturing a thermoplastic resin pipe joint, the method comprising: pouring a thermoplastic resin between the outside of the mandrel and an outer frame provided at a predetermined distance from the mandrel.