WO2009053674A1

WO2009053674A1 - Radiant electric heater

Info

Publication number: WO2009053674A1
Application number: PCT/GB2008/003521
Authority: WO
Inventors: Kevin Ronald Mcwilliams
Original assignee: Ceramaspeed Limited
Priority date: 2007-10-23
Filing date: 2008-10-17
Publication date: 2009-04-30
Also published as: GB0720692D0

Abstract

A radiant electric heater for a domestic cooking appliance. The heater comprises a base layer (11) of electrical and thermal insulating material, a radiant electric heating element (15) supported relative to the base layer, and a peripheral wall (13) of thermal insulating material. The peripheral wall has a substantially planar upper surface (21) and substantially circular inner (19) and outer (17) faces. The centre of the inner face is offset relative to the centre of the outer face.

Description

RADIANT ELECTRIC HEATER

This invention relates to a radiant electric heater for use in a domestic cooking appliance such as a cooker hob having a glass ceramic cooktop. The invention also relates to a domestic cooking appliance incorporating such a radiant electric heater.

Glass ceramic appliances incorporating electronic controls can suffer from problems as a result of elevated temperatures. The temperature within such a cooker hob can rise excessively as a result of high ambient temperature and/or direct radiation from components of the radiant electric heaters which heat cooking utensils through the glass ceramic surface, especially under high use conditions such as with all the heaters energised. If the temperature rises excessively, the use of high cost, specialist electronic components may be required to withstand the high temperatures. In extreme circumstances, particularly in small and/or cramped appliances, an over-temperature protection device incorporated as part of the electronic circuitry will switch the appliance to reduced power, or indeed switch off the entire appliance, in order to protect the electronic controls from gross failure.

It is therefore an object of the present invention to provide a radiant electric heaterfora domestic cooking appliance which overcomes or at least ameliorates the above disadvantage. According to one aspect of the present invention there is provided a radiant electric heater for a domestic cooking appliance, the heater comprising:

a base layer of electrical and thermal insulating material;

a radiant electric heating element supported relative to the base layer; and

a peripheral wall of thermal insulating material, the peripheral wall having a substantially planar upper surface and substantially circular inner and outer faces, the centre of the inner face being offset relative to the centre of the outer face.

The heater may include a dish, for example of metal, supporting the base layer and the peripheral wall.

The heating element may comprise, for example, one or more of an elongate corrugated ribbon partially embedded edgewise into the surface of the base layer, and/or a helically coiled bare wire heating element secured to the surface of the base layer, and/or an infra-red lamp supported above the base layer.

A terminal block may be provided, for example secured to the dish, to supply electric power to the heating element. A thermal control device may extend at least partially across the base layer above the heating element for preventing excessive temperatures in the region of the heater.

According to another aspect of the present invention there is provided a domestic cooking appliance incorporating a radiant electric heater as hereinbefore defined.

The radiant electric heater may be arranged beneath a glass ceramic cooking surface.

The appliance may additionally incorporate an electronic control module for the heater, the heater being arranged within the appliance such that the widest part of the peripheral wall is closest to the electronic control module.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which:

Figure 1 is a diagrammatic plan view of a domestic cooking appliance incorporating one embodiment of a radiant electric heater according to the present invention; and Figure 2 is a sectional view of the radiant electric heater taken along the line H-Il shown in Figure 1.

Figure 1 is a plan view of a domestic electric cooking appliance 1 incorporating a glass ceramic cooking surface 2, a number of conventional radiant electric heaters 3 arranged beneath the glass ceramic cooking surface, together with an electronic control module 5 and one embodiment of a radiant electric heater 7 according to the present invention, also arranged beneath the glass ceramic cooking surface. The heater according to the present invention is shown in side view in Figure 2.

The heater according to the present invention comprises a metal dish 9 which contains a base layer 11 of thermal and electrical insulating material, such as microporous insulating material, and a peripheral wall 13 of thermal insulating material which extends within the rim of the dish 9 from the base layer 11 to the underside of the glass ceramic cooking surface throughout substantially the entire radial extent of the peripheral wall 13, the peripheral wall therefore having a substantially planar upper surface. The peripheral may be made, for example of a ceramic fibre material or of a vermiculite-based material. Both are well known to the skilled person.

A radiant electric heating element 15 is supported relative to the base layer 11 , such as embedded partially in the base layer, secured to the surface of the base layer-, or mounted above the base layer, within the confines of the peripheral wall 13. For example, the heating element 15 may comprise one or more of an elongate corrugated ribbon partially embedded edgewise into the surface of the base layer 11 , and/or a helically coiled bare wire heating element secured to the surface of the base layer 11 , and/or an infra-red lamp supported above the base layer 11. A terminal block (not shown) or other suitable connection means is secured to the metal dish to supply electric power to the heating element 15 under control of the electronic control module 5.

A thermal control device (not shown) is conventionally provided within the metal dish 9 extending at least partially across the base layer 11 above the heating element 15 for preventing excessive temperatures in the region of the heater, for example so as to de-energise, or at least reduce the supply of power to, the heating element 15 in the event the temperature of the glass ceramic cooking surface becomes excessive.

As can be seen from Figure 1 , the metal dish 9 and the inner surface of the peripheral wall 13 are conventionally circular to accommodate various sizes of cooking utensil which are also generally circular in plan view. Elongate cooking utensils, such as fish kettles, are generally accommodated by providing a part annular heating element to one or opposing lateral sides of a circular heating element or providing a waisted heating element (somewhat in the shape of an egg-timer) between two circular heating elements. In either case, although the configuration of the metal dish is non-circular, such an elongate utensil is heated with one or more circular heating elements which are surrounded by a peripheral wall of insulating material.

It should be noted that in some radiant electric heater constructions the metal dish is not required.

The peripheral wall shown in Figures 1 and 2 has a substantially circular outer face -17 and a substantially circular inner face 19, with a substantially planar upper surface 21 (that is, an upper surface which extends to a constant height) for engaging with the underside of the glass ceramic cooking surface. However, the centres of the inner and outer faces are not coincident, but are offset by several millimetres such that the width of the peripheral wall 13 varies around its circumference with the peripheral wall being at its widest at one point and being at its narrowest at a diametrically opposite point.

The configuration of the peripheral wall 13 means that the radiant electric heater can be positioned in an appliance, such as a cooktop, with the widest part of the peripheral wall closest to the electronic control module 5 so as to thermally isolate the control module 5 as far as possible from the heating effects of the heater 7. The configuration of the peripheral wall 13 has the further advantages that the peripheral wall can be arranged within a substantially circular dish 9 due to the circular outer face 17 while at the same time presenting a circular cooking area, thus adapted to circular cooking utensils, due to the circular inner face 19.

Claims

1. A radiant electric heater for a domestic cooking appliance, the heater comprising:

a base layer (11 ) of electrical and thermal insulating material;

a radiant electric heating element (15) supported relative to the base layer; and

a peripheral wall (13) of thermal insulating material, the peripheral wall having a substantially planar upper surface (21 ) and substantially circular inner (19) and outer (17) faces, the centre of the inner face being offset relative to the centre of the outer face.

2. A heater as claimed in claim 1 and including include a dish (9) supporting the base layer (11 ) and the peripheral wall (13).

3. A heater as claimed in claim 2, characterised in that the dish (9) comprises a metal.

4. A heater as claimed in any preceding claim, characterised in that the heating element (15) comprises one or more of an elongate corrugated ribbon partially embedded edgewise into the surface of the base layer (11 ), and/or a helically coiled bare wire heating element secured to the surface of the base layer, and/or an infra-red lamp supported above the base layer.

5. A heater as claimed in any preceding claim, characterised in that a terminal block is provided to supply electric power to the heating element (15).

6. A heater as claimed in claim 5 when dependent on claim 2 or any claim dependent thereon, characterised in that the terminal block is secured to the dish (9).

7. A heater as claimed in any preceding wall, characterised in that a thermal control device extends at least partially across the base layer (11 ) above the heating element (15) for preventing excessive temperatures in the region of the heater.

8. A domestic cooking appliance incorporating a radiant electric heater (7) as hereinbefore defined.

9. An appliance as claimed in claim 8, characterised in that the radiant electric heater (7) is arranged beneath a glass ceramic cooking surface (2).

10. An appliance as claimed in claim 8 or 9 and additionally incorporating an electronic control module (5) for the heater (7), the heater being arranged within the appliance such that the widest part of the peripheral wall (13) is closest to the electronic control module.