RU1830196C - Electric heater - Google Patents

Abstract

SUBSTANCE: electric heater is made in the form of an open resistive element (RE) from a stretched wire spiral. It contains a layer fixing its position. The layer is made over the entire surface of the RE from a material with ductility at a working temperature lower than that of the RE. The fixing layer is made of ceramic or an oxide film of RE material. 1 C.p. f-ls, 2 ill.

Description

The invention relates to electric heating and can be used in domestic electric heaters with directional radiation (electric fireplaces).

An object of the invention is to improve the maintainability of a known device. At the same time, it is intended to expand the scope of the invention, extending it to all cases where the sagging of a spiral affects the performance of the product.

To this end, in an electric heater containing an open resistive element in the form of a stretched wire spiral and a position-fixing layer of a heat-resistant dielectric material, said fixing layer is made in the form of a surface layer on a resistive element of a material with less ductility at a working temperature than that of the material resistive element.

The absence of a rigid connection between the resistive element and the base makes it possible to replace any of these parts of the heater without damaging the other part, i.e. increases the maintainability of the device. At the same time, the surface layer with the indicated properties forms a reinforcing frame on the spiral, increasing its tensile stiffness and preventing sagging under operating conditions. Despite the gaps between the turns, the dielectric nature of the surface layer is also useful here, since the conductive layer would distort the calculated resistance of the resistive element. The invention is applicable both when winding the spiral on the base, and when placing it in a shell of any shape.

The surface layer with the required properties is made either in the form of an external coating, for example, ceramic, or in the form of an intrinsic oxide film of the material of the resistive element. The technology for producing such layers and the required equipment has been developed by industry.

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The required thickness of the surface layer is selected experimentally depending on the material, load and initial stiffness of the spiral. In order to accelerate the oxidation (in the thermal version), it is recommended that it be carried out near the onset of intense scale formation (for nickel-chromium alloys 1100 ± 50 ° C), in contrast to oxidation for the purpose of electrical insulation, where the optimum mode corresponds to temperatures of 850 900 ° C.

Figure 1 shows a fragment of a longitudinal section of a concentrated heater; figure 2 is a cross section of a wire with a surface layer deposited from the outside (2A) and its own oxide (26).

The heater in Fig. 1 contains an open re-resistive element 1 in the form of a double helix with an inner diameter D obtained by winding a spiral with an inner diameter dc from a wire of diameter dnp on an insulating base Зс with a helical semicircular groove ..- ..

After turning on the heater in the network and reaching the operating temperature, the plasticity of the material increases and the initial elastic stresses are removed, after which the bi-spiral resistive element 1 is prevented from sagging in the upper sections by the base 3. and in the lateral and lower sections by the surface layer 2, forming a rigid frame on the turns bispiral 1.:

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The invention can be used in all cases where the sagging of a spiral resistive element is possible and undesirable. Its use is particularly effective in heaters with a spiral in a quartz tube bent around a horizontal axis or close to it, the reliable operation of which cannot be ensured by known means. Their advantage in comparison with the heater shown in Fig. 1, where the spiral is externally insulated, is enhanced by electrical and fire safety ™.

FORMULA AND ZOBRETE N and

Claims (2)

1. An electric heater containing an open resistive element in the form of a stretched wire spiral and fixing its position a layer of heat-resistant dielectric material, characterized in that, in order to increase maintainability, this layer is made in the form of a surface layer of a resistive element made of a material with plasticity at operating temperature lower than that of the material of the resistive element. 2. The electric heater according to claim 1, with the fact that the surface layer is made of a ceramic material or an oxide film of the material of the resistive element. FIG. I 6) fig 2 J-j