JP3076653U - Electric heater - Google Patents

Abstract

(57) [Problem] To use a microporous heat insulating material having a very water-absorbing property as a heat insulating layer for supporting a heating element of a radiant electric heater. Ensure that the electrical insulation resistance between the metal support dishes is kept to an acceptable high value. The electric heater (1) includes a metal support dish (2) having a layer (5) of, for example, a microporous heat insulating material, at least one electric heating element (6) being supported with respect to the layer (5). The dish 2 is partially or entirely provided on its inner surface 3 and / or outer surface 4 with an electrically insulating coating 9, 10, for example made of glassy enamel or alumina.

Description

[Detailed description of the invention]

The invention has a metal support dish, which is particularly radiant and is provided with a layer of heat insulating material, wherein at least one electric heating element is supported with respect to said layer of heat insulating material. It relates to an electric heater.

[0002] Radiant electric heaters of this kind are known, in particular, in cookers such as, for example, ovens, hobs and grills. In a typical configuration, a metal support dish, such as steel, for example, is provided with a layer of compressed microporous thermally insulating material inside. At least one heating element is supported on or adjacent to the layer of thermally insulating material. A particularly well-known form of heating element is a corrugated metal ribbon supported on or fixed to the edge of the surface of the thermally insulating material.

[0003] Some national electrical safety laws require that an electrical heater be subjected to a submersion test, and then the electrical insulation resistance between the metal dish and the heating element be measured, and that this value must exceed a certain value. Demand that it be done.

[0004] Microporous thermal insulation materials are very water-absorbing, and if this material is used as an insulating layer to support the heating elements of a heater, the material may be between the dish and the heating elements. The measured electrical insulation resistance is unacceptably low.

It is an object of the present invention to eliminate or minimize this problem.

In accordance with the invention, an electric heater includes a metal support dish having a layer of heat insulating material, wherein at least one electric heating element is supported with respect to the layer of heat insulating material. Provided at least partially having an inner surface provided with an electrically insulating coating.

[0007] The layer of thermally insulating material may comprise a microporous thermal and electrically insulating material.

[0008] The electrically insulating coating is disposed so as to cover an inner surface of the dish, at least a portion provided with the layer of the heat insulating material, or substantially the entire inner surface of the dish. You can do so.

The dish may have at least an outer surface at least partially provided with an electrically insulating coating.

[0010] The electrical insulating coating is selected from glassy enamel, glass-ceramic, ceramic, particulate metal oxide (for example, composed of alumina), polytetrafluoroethylene material, silicon material and epoxy resin. Can be.

[0011] The electrical insulating coating may be applied in particulate form and subsequently heat treated.

In order to better understand the present invention and to show more clearly how the present invention may be put into practice, an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIGS. 1 and 2 of the drawings, the radiant electric heater 1 includes a metal support dish 2, for example, steel, which has an inner surface 3 and an outer surface 4.

A layer 5 of compressed microporous thermal and electrically insulating material is provided inside the dish 2, and at least one electric heating element 6 is fixed to the layer 5.

A single heating element 6 is shown, which is mounted on the surface of layer 5 along its edge and is partially embedded in layer 5 or otherwise. Consisting of a corrugated metal ribbon of known shape secured by known means.

The heating element 6 may be a coiled wire, or a coiled ribbon, or a face-mounted ribbon, or one or more lamps, or any other form known to those skilled in the art. Element. Also, one or more heating elements may be provided on the heater.

A terminal block 7 for one or more heating elements 6 is attached to the heater so that the heater can be connected to an operating voltage supply.

Further, a peripheral wall 8 of a heat insulating material is provided on the heater. As shown, this peripheral wall is integral with layer 5. However, as is well known in the art, the surrounding wall may be provided as a separate member.

Furthermore, an electrically insulating coating 9 is provided on the inner surface 3 of the dish 2. Such a coating 9 is provided over substantially the entire inner surface 3 of the dish, or at least over the area of the inner surface of the dish that contacts the layer 5 of insulating material.

The outer surface 4 of the dish 2 can optionally also be provided with an electrically insulating coating 10, which is suitably made of the same material as the coating 9.

These coatings 9 and 10 preferably consist of a known form of glassy enamel which is applied to the dish 2 in a known manner. Glassy enamels and methods of applying these enamels to substrates such as steel are very well known to those skilled in the art. A suitable glassy enamel is known as PROTEC 9900A sold by Protec Enamel Limited, UK.

Other well-known materials and methods can be used to provide the electrically insulating coatings 9 and 10. For example, coatings 9 and 10 can be comprised of a glass-ceramic material or a ceramic material (eg, silicon nitride). Further, a coating material composed of a particulate metal oxide such as alumina can be appropriately applied by a method such as flame spraying or plasma coating. Further, coatings 9 and 10 may be spray-coated polytetrafluoroethylene, or a silicon material, such as, for example, sold under the trade name BL AZEKOTE by Omnikote Limited, UK, or OXYPLAST F56, for example, by Oxyplast Belgium NV. // May consist of an epoxy material such as that sold by THERM.

The coatings 9 and 10 are applied as a powder (to be suspended) and then cured, sintered or other heat treated to form an electrically insulating coating.

When the heater 1 made as described above is subjected to a water immersion test, the microporous heat and electric insulation layer 5 absorbs water. If there is no electrical insulation coating 9 on the inner surface 3 of the metal dish 2, the electrical insulation resistance measured between the heating element 6 and the metal dish 2 will be unacceptably low. . However, the provision of the electrically insulating coating 9 provides a high level of electrical insulation resistance. The electrical insulation of the dish is further enhanced by providing an electrical insulation coating 10 on the outer surface 4 of the metal dish 2.

The radiant heater 1 of the present invention is particularly applicable to cookers such as ovens, grills, toasters, and hobs.

[Brief description of the drawings]

FIG. 1 is a plan view of a radiant electric heater according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the heater of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 radiant electric heater 2 metal support dish 3 inner surface 4 outer surface 5 layer of heat insulating material 6 electric heating element 7 terminal block 8 peripheral wall 9 electric insulating coating 10 electric insulating coating

Continued on the front page (73) Utility model holder 593023888 ZORTECH AVENUE, OLDI NGTON, KIDDERMINSTER, WORCESTERSHIRE DY117D, UNITED KINGDO M Droitwich Hanbury Howarf Canal Cottage 3

Claims (8)

[Utility model registration claims] 1. A method according to claim 1, further comprising a metallic support dish having a layer of thermally insulating material, wherein at least one electric heating element is supported with respect to said layer of thermally insulating material. An electric heater (1), characterized in that said dish (2) has at least an inner surface (3) at least partially provided with an electrically insulating coating (9). 2. An electric heater according to claim 1, wherein said layer of thermally insulating material (5) comprises a microporous heat and electrically insulating material. 3. An electric heater according to claim 1, wherein said electrically insulating coating is provided on an inner surface of said dish and at least a layer of said thermally insulating material. An electric heater, wherein the electric heater is provided so as to cover a portion of the electric heater. 4. An electric heater according to claim 3, wherein said electrically insulating coating (9) is arranged to cover substantially the entire inner surface (3) of said dish (2). Electric heater. 5. The electric heater according to claim 1, wherein the dish (2) has an outer surface (4) at least partially provided with an electrically insulating coating (10). An electric heater comprising: 6. An electric heater according to claim 1, wherein said electrically insulating coating is formed on said electrically insulating coating.
An electric heater characterized in that 0) is selected from glassy enamels, glass-ceramics, ceramics, particulate metal oxides, polytetrafluoroethylene materials, silicon materials and epoxy resins. 7. An electric heater according to claim 6, wherein said particulate metal oxide comprises alumina. 8. An electric heater according to claim 1, wherein said electrically insulating coating is formed on said electrically insulating coating.
0) is applied in the form of particles and then heat-treated.