JPS5911195B2 - tubular heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a tubular heating element using a sheet heating element.

Conventionally, when insulating or heating a tubular body, it has been wrapped with nichrome wire or, more recently, covered with a planar heating element.

In any of these cases, the tubular body is subjected to post-processing, and the manufacturing work is very complicated, and in some cases, it may be necessary to request a specialist to carry out the construction.

Furthermore, because the processing is complicated, the electrical insulation properties may be poor, and in some cases, the nichrome wire or the lead wire of the sheet heating element may be broken. The present invention provides a tubular heating element that overcomes these drawbacks. The method for producing a tubular heating element according to the present invention is characterized in that an unstretched film or a stretched film layer, a planar heating element, and a stretched film layer are sequentially provided on the outer surface of a core body and then heat-fused.

Further, in another aspect of the present invention, the core body is removed after heat fusion. 15 The above core is made of metal, porcelain,
It is a tubular or rod-shaped core made of plastic or the like.

The material of the stretched film used includes thermoplastic resins such as polyethylene, polypropylene, polytetrafluoroethylene, fluoroethylene propylene polymer, and silicone 20.

These stretched films are usually long and uniaxially stretched in the longitudinal direction, and are preferably used at a stretching ratio of 1.5 to 6.
twice as much is usually used.

When winding the stretched film around the core, it is preferable to wind the stretched film so that the stretching direction of the stretched film is approximately perpendicular to the axis of the core 25. That is, in normal cases, the stretched film is wound around the core in a sushi-wound shape so that the stretching direction is perpendicular to the core, or a long film is wound in a spiral shape.

30 Stretched film lengths that are excessively stretched in the width direction are not very preferred because they shrink in the length direction of the core during the heat-sealing step after winding.

In addition, in order to make it easier to take out the core after heat fusion, it is necessary to wrap the unstretched film directly on the outer surface of the core until it reaches the stretched film, instead using a glass cloth or the like coated with polytetrafluoroethylene. It is advantageous to include a release sheet.

In addition, the outer surface of the core may be coated with polytetrafluoroethylene in advance, or a film having release properties such as a polytetrafluoroethylene film may be used as an unstretched film or a stretched film wound around the outer surface of the core. When using a mold release sheet, the work can be performed without intervening a release sheet. Furthermore, when heating and fusing a stretched film and a planar heating element wound around a core, a protective tape or sheet such as polytetrafluoroethylene tape is wound around the outermost stretched film layer. It is preferable to prevent changes in the shape of the stretched film layer that occur during heat fusing.

The stretched films wound around the inner and outer surfaces of the planar heating element are preferably made of the same material, but even if they are made of different materials, they can be advantageously used as long as they can be fused together by heating.

Further, in the present invention, if a tubular core is used as the core, the tubular core can be left as it is without being removed after heat fusion and used as a tubular heating element.

In the present invention, a stretched film coated with an adhesive layer can be used instead of the stretched film described above, and such a stretched film is also included in the scope of the stretched film of the present invention.

For example, a fluoroethylene propylene polymer, polyethylene, or the like is provided as an adhesive layer on the surface of a stretched polytetrafluoroethylene film. The planar heating element in the present invention is made by coating and impregnating a heat-resistant fiber woven fabric such as glass fiber with a conductive material that has a relatively high resistance and generates heat when energized, such as carbon black and a resin binder. Preferably used.

Further, as the shape of the sheet heating element, it is particularly suitable in the present invention to use a grid-like sheet heating element.

Among the tubular heating elements obtained by the method of the present invention, those having a core can be used, for example, as a heating heater by combining a predetermined number of them, and those from which the core has been removed can be used, for example, for water pipes. They are used to prevent water from freezing in the winter by being fitted over pipes for transporting highly viscous substances, and to maintain transport efficiency by insulating the pipes for transporting highly viscous materials. Next, the present invention will be explained by examples.

Example 1 As shown in Figure 1, the inner diameter is 50m7! Nitto Denko K.I. K-manufactured Nitoflon, 46973 (polytetrafluoroethylene coated glass cloth) is wrapped in a single layer in a sushi roll shape, and then a long stretched cross-linked polyethylene film (2
Double stretched, thickness 0.2W! K width 200m71L1
) Wrap 3 6 times.

Next, on top of this, as shown in Figure 2, the height is 160 m and the width is 1.
A sheet heating element 4 of 60 mm and an electric resistance of 550 Ω is wound, and the above-mentioned stretched cross-linked polyethylene film 3' is further wound 6 times, and then this is wrapped with Nitto Denko K.K. Cover the polytetrafluoroethylene sheet manufactured by K with Nitoflon Taki 923 (product name) (protective tape), heat it in a dryer at 250°C for 30 minutes, take it out of the dryer, and use the above protective tape and release sheet. , the stainless steel tube was removed to obtain a tubular heating element. The resulting tubular heating element is shown in FIGS. 3 and 4.

In the figure, numeral 31 indicates fused stretched and crosslinked polyethylene. In FIG. 2, P and P' are electrodes, and L and L' are lead wires. When the obtained tubular heating element was energized with a general household voltage of 100 V through the electrodes P and P', the internal temperature of the tube was 80 to 85°C.
It exhibited a uniform temperature state, and the insulation resistance after being immersed in water for 2 hours was 2000 MΩ or more.

In addition, in the above Example 1, the product obtained by the same manufacturing procedure except that the release sheet was not used can be made into a tubular heating element with the stainless steel tube provided on the inner surface, and this is different from the tubular heating element of Example 1. It had the same effect as a heating element. Example 2 Instead of the stretched crosslinked polyethylene in Example 1, a long fluoroethylene propylene stretched film (stretched 2.5 times in the length direction, thickness 0.2m7t width 2007!) was used.
10, a sheet heating element with an electric resistance of 125 Ω (vertical 160 m1, width 160 m1) was used instead of the sheet heating element in Example 1.
Example 1 except that 11) was used and the heating temperature was 350°C.
A tubular heating element was obtained using the same procedure.

The tubular heating element thus obtained is one for general household use.
When 00V was applied, the tube exhibited a uniform internal temperature of 195 to 200°C, and the insulation resistance after being immersed in water for 2 hours was 2000 MΩ or more, indicating good watertightness. The tubular heating element obtained by the method of the present invention as described above is
Since at least the outer surface of the planar heating element is covered with a plastic film that is tightly heat-fused together by the stretching restoring force, it has excellent electrical insulation properties.

Furthermore, since a planar heating element is used as the heater, the temperature distribution is uniform, and there is no fear of wire breakage as with nichrome wire.

Furthermore, since the planar heating element and the molten plastic film are in complete contact with each other, the heat efficiency is extremely high and it is economical. Furthermore, since the planar heating element is covered with a plastic film that has been stretched in advance and then melted, it has good watertightness and electrical insulation properties not seen in the past. In the present invention, an unstretched film can also be used as the plastic film (portion indicated by 3 in the figure) used on the inner surface of the planar heating element.

This is because even if an unstretched film is used on the inner surface, the stretched film wound around the outer surface of the planar heating element tightens and fuses the tubular heating element during heat fusion during manufacture of the tubular heating element. Further, the tubular heating element obtained by the present invention can be used for heating or heat retention as a tubular heating element having an opening by cutting the point C in FIG. 4 in the length direction of the tubular heating element. It can be used for other purposes.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams for explaining the method of manufacturing the tubular heating element of the present invention, FIG. 3 is a perspective view showing an example of the tubular heating element of the present invention, and FIG. 4 is the same as that shown in FIG. It is a sectional view taken along the line AN and viewed in the direction of the arrow. 3,3t...Stretched film, 4...Planar heating element.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a tubular heating element, which comprises sequentially providing an unstretched film or a stretched film layer, a planar heating element, and a stretched film layer on the outer surface of a core and heat-sealing them. 2. A method for producing a tubular heating element, which comprises sequentially providing an unstretched film or a stretched film layer, a planar heating element, and a stretched film layer on the outer surface of the core, heating and fusing them, and then removing the core.