JPH0474838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement of an electric resistance heating element, particularly a band-shaped heating element (hereinafter referred to as a band-shaped heating element).

[Prior Art] Generally, this type of heating element is constructed by embedding electrode wires in both sides of a plastic body containing conductive powder shaped like a belt, and an insulating coating and an insulating coating are arranged around the heating element. It is formed by applying an exterior body depending on the conditions of use, and there are two known types of cross-sections: flat and sub-slope.

FIG. 3 shows a flat strip-shaped heating element, and FIG. 4 shows a rectangular heating element. In the figure, reference numeral 1 denotes a current-carrying heating element showing a positive temperature resistance system, which is constructed by embedding electrodes 3, 3 on both sides of a band-shaped body 2 made of crystalline synthetic resin mixed with carbon black powder;
is an insulating coating applied around the heating element.

In the case of a flat heating element, since two flat surfaces 5, 5 are provided, it is possible to bring the heating element into close contact with a flat object to be heated whose surface shape is not complicated, using one of the flat surfaces 5. Although the heat transfer performance to the object to be heated is satisfactory to some extent, it is not suitable for objects to be heated whose surface shape is rich in undulations.

This allows the heating element 1 to have a uniform thickness, a large cross-sectional coefficient, and a large resistance to bending.
According to this, when pipe heating is installed on a place with a highly undulating surface such as a valve or instrument part, due to the large bending resistance, a gap is created between the heated surface and the heat transfer. It was making it less efficient.

In addition, bending was difficult and there were problems with poor workability.

In the case of a sub-shaped heating element, the thickness between the electrodes 3 is reduced, so it has excellent flexibility and can be easily wrapped around objects with complex surface shapes. In terms of the surface shape, gutter-like grooves 6, 6 are formed on both sides, so when this is attached to the heated surface, the energized heating element between the electrodes separates from the heated surface, creating an air layer between them. This reduces the heat transfer efficiency to the heated object.

A decrease in thermal efficiency leads to an increase in the capacity of the heating element, a clear disadvantage.

In addition, the problem with the heating element in the above example is that the side opposite to the side to which it is attached to the heated surface is unprotected, and the heat dissipated from here is large, which has a considerable effect on effective heat transfer to the heated object. is affecting.

In order to prevent heat dissipation on surfaces that do not correspond to the heated surface, it has been proposed that a heat insulating material be interposed between the energized heating element and the insulator that covers it (Utility Model Application No. 52-132342
issue). However, the use of a heat insulating material tends to increase the amount of material and increase the bending rigidity.

[Problems to be Solved by the Invention] As described above, the conventional belt-shaped heating element of this type has enough flexibility to be applied closely to the heated object with a complicated surface without any gaps, and In both cases, it was not possible to effectively transfer heat to objects.

The present invention has been developed in view of the above circumstances, and is highly flexible and can be easily installed in close contact with the heating element. The purpose is to donate the body.

[Means for Solving the Problems] In the band-shaped heating element of the present invention, the resistor, which serves as a base in the current-carrying heating element and also serves as the current-carrying heat-generating portion, has one surface portion flat and the other surface portion corresponding thereto. On the flat surface side of this heating element, all of the insulating coating from the surface to the mounting surface to the heated object and the exterior body applied as necessary are closely connected. At the same time, on the other concave groove surface side, the surface portion and the insulating coating thereon or the exterior body applied as necessary are separated, and an air layer is formed between them. It is characterized by becoming.

The current-carrying heating element preferably has self-regulating properties, that is, positive temperature coefficient characteristics. this is,
A resistor is obtained by mixing an appropriate amount of carbon black powder such as acetylene black into a crystalline synthetic resin obtained from polyethylene, ethylene ethyl acrylate, polyvinylidene fluoride, etc., and a pair of electrodes is embedded within this resistor. The desired heating element can be obtained.

The insulating coating may be made of urethane, fluororesin, or the like having desired heat resistance.

The exterior body may be a resin sheath made of flame retardant polyethylene, fluororesin, or may include a metal shield such as a copper braid.

In the band-shaped heating element as described above, the air layer is
It has a large resistance to heat conduction and has a so-called adiabatic effect. As a result, the heat generated by the resistor in the current-carrying heating element has a low rate of dissipating outward through the air layer, and on the other side there is an insulating sheath that is closely applied and an exterior that is provided as necessary. It actively transfers heat to the body and increases the efficiency of heat transfer to the heated body.

Furthermore, since the air layer is formed by forming grooves in the energized heating element, bending resistance is reduced and flexibility is excellent.

[Example] FIG. 1 shows an example of a preferred band-shaped heating element of the present invention. The energizing heating element 10 consists of a band-shaped resistor 11 made of crystalline synthetic resin containing carbon black powder, and stranded wire conductors 12, 12, which serve as electrodes, embedded in the longitudinal direction of both edges of the resistor 11. . The resistor 11 serves as a main current-carrying heat generating part between the buried positions of the stranded wire conductors 12, 12, and has a flat surface 11a on one side of the heat generating part and a concave groove 11b formed on the other side. Consisting of
The insulating cover 20 is extruded and coated onto the current-carrying heating element 10 in the form of a tube, and is closely attached to the flat surface 11a of the resistor 11, but is spaced from the concave groove 11b. An internal space, ie, an air layer 30, is formed above the concave groove 11b, which is closed by the inner surface 20a of the insulating cover 20, which extends between both side edges of the resistor 11 and serves as shoulders of the groove.

The band-shaped heating element H configured in this way is attached to the heating target, for example, the high viscosity liquid transport pipe P, on the mounting surface 20 of the insulating coating on the opposite side to the side where the air layer 30 is formed.
Tracing is carried out in close contact with b.

Therefore, if the stranded wire conductors 12, 12 are connected to a predetermined power source and energized, the resistor 1 generates heat when energized.
1 is transmitted to the heated object P via the insulating covering 20 as quickly as possible.

FIG. 2 shows a second embodiment of the band-shaped heating element of the present invention. The energizing heating element 100 is made of a carbon black powder-containing resin resistor in which twisted wire conductors 120, 120 are embedded in the same manner as in the above embodiment.

However, in this embodiment, an insulating coating 200, a copper braid 400, and a synthetic resin sheath 500 are provided on the energizing heating element 100.

The insulating coating 200 is tightly coated around the current-carrying heating element 100, and therefore fits into the concave groove 1 of the resistor 110.
A similar concave groove 200a is formed alongside 10b.

A copper braid 400 and a sheath 500 are formed to cover the insulating coating 200 in a tube shape,
They are formed in close contact with each other on the flat surface 110a side of the resistor 110, but are spaced apart from the concave groove 200a surface of the insulating cover 200 on the concave groove 110b side. The inner surface 400 of the copper braid 400 is placed on the concave groove 200a.
An air layer 300 closed at a is formed. Therefore, on the opposite side of the air layer 300 via the resistor 110, the flat surface of the sheath 500 serves as the mounting surface 500a of the heated object.

In the above embodiment, a copper braid and a synthetic resin sheath were applied, but it is also possible to use only one of the copper braid and the synthetic resin sheath.

[Effects of the Invention] According to the band-shaped heating element of the present invention, the cross-section of the band-shaped resistor, which serves as the base of the energized heat-generating portion, is small and soft, so even crowded objects to be heated can be installed in close contact with each other without gaps. It has excellent construction workability, and also has good adhesion between the heated object and the resistor, and there is an air layer on the opposite side to suppress heat dissipation, so the heated object This can greatly improve the heat transfer efficiency to.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing one embodiment of the band-shaped heating element of the present invention together with the state of use, and FIG. 2 is an explanatory cross-sectional view showing another embodiment of the band-shaped heating element of the present invention. FIGS. 3 and 4 are cross-sectional explanatory views showing two types of conventional band-shaped heating elements. 10,100... Current heating element, 400... Copper braid, 20,200... Insulating coating, 500... Synthetic resin sheath, 30,300... Air layer, 11
a, 110a...flat surface, 11b, 110b, 2
00a...Concave groove.

Claims (1)

[Claims] 1. A band-shaped current-carrying heating element in which conductors serving as electrodes are embedded in the longitudinal direction of both sides of the base, which is a resistor made by mixing conductive powder in resin and shaping it into a band shape.
It is a band-shaped heating element composed of an insulating coating applied around the heating element and an exterior covering applied around it as necessary, and the band-shaped current-carrying heating element has a resistor as its base. One surface of the heating element is flat, and a concave groove is formed on the other surface of the corresponding resistor, and on the flat surface side of the resistor of this heating element, there is a flow from the surface to the heated part. All of the insulating sheathing up to the mounting surface and the exterior body provided as necessary are installed closely together, and on the side of the other concave groove surface of the resistor, the surface and the insulating sheathing or the sheathing provided as necessary are provided. A band-shaped heating element characterized by separating an exterior body and forming an air layer therebetween.