GB2161348A

GB2161348A - Radiation heater reflector

Info

Publication number: GB2161348A
Application number: GB08513731A
Authority: GB
Inventors: Joseph Anthony Mcwilliams
Original assignee: Micropore International Ltd
Current assignee: Micropore International Ltd
Priority date: 1984-06-09
Filing date: 1985-05-31
Publication date: 1986-01-08
Also published as: GB8513731D0

Abstract

A reflector for a radiation heater comprises a plurality of reflecting sections (10) which are positioned substantially in a plane so as to intercept portions of radiation emitted by a radiation source (9) and to reflect the radiation in a predetermined direction. The edges of the reflector may extend out of the plane in order to prevent radiation escaping around the edges of the reflector. The reflecting sections (10) may incorporate a peaked portion (11) which is positioned so as to oppose the or each radiation source (9) in order to obtain a more even distribution of reflected radiation. <IMAGE>

Description

SPECIFICATION Reflector for a radiation heater The present invention relates to a reflector for a radiation heater, to a radiation heater incorporating such a reflector and to an electric cooker incorporating such a radiation heater.

Electric cookers which incorporate radiation heaters are known, for example, from British Patent Specifications Nos.1 273 023 and 1 406 028.

However, these prior art cookers either employ reflectors which are too deep or provide an unsatisfactory distribution of reflected radiation or employ one or more heat sources which are distributed substantially over the entire heated area.

It is therefore an object of the present invention to provide a reflector for a radiation heater which is relatively shallow and which at the same time provides a satisfactory distribution of reflected radiation.

According to the first aspect of the present invention there is provided a reflector for a radiation heater, which reflector comprises a plurality of reflecting sections which are positioned substantially in a plane to intercept portions of radiation emitted by a radiation source and to reflect the radiation in a predetermined direction.

In order to prevent radiation escaping around the edges of the reflector, the edges of the reflector may extend out of said plane.

The reflecting sections may themselves be planar or may be curved. Where the reflecting sections are curved they are preferably curved in the shape of a part of a parabola. The reflecting sections may be linear where the radiation source is intended to be linear, but a degree of curvature may be incorporated into the end portions of the reflecting sections so as to compensate for any changes in the distribution of radiation emitted towards the ends of the radiation source. Alternatively, the reflecting sections may be curved along their length where the radiation source is intended to be curved.

The configuration of the reflecting sections may be adapted to the use of a plurality of radiation sources.

The reflecting sections may incorporate a peaked portion to be positioned so as to oppose the or each radiation source in order to obtain a more even distribution of reflected radiation.

The reflecting sections may incorporate a base layer of thermal insulation material such as ceramic fibre or microporous thermal insulation material.

According to a second aspect of the present invention there is provided a radiation heater which incorporates a reflector according to the first aspect of the present invention and a radiation source.

The radiation source may be, for example, an infra-red radiation emitting lamp or a heater element in the form of a resistance wire. The radiation source may be linear or may be curved. If desired, a plurality of radiation sources may be provided.

A reflector may be positioned over the or each radiation source so as to reflect onto the reflecting sections radiation which would otherwise not be intercepted by the reflecting sections. The reflector may be a specular reflector or a diffuse reflector.

Acccording to the third aspect of the present in vention there is provided an electric cooker com prising a substantially smooth, radiation transmissive cooking surface and a radiation heater according to the second aspect of the pres ent invention.

For a better understanding of the present invention and to show more clearly how it may be car ried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a cross-sectional view through a ra diation heater incorporating a parabolic reflector such as has been proposed in the prior art; Figure 2 is a cross-sectional view through a radiation heater incorporating a dished reflector such as has been proposed in the prior art: Figure 3 is a cross-sectional view through one embodiment of a radiation heater incorporating a reflector according to the present invention: and Figure 4 is a cross-sectional view through another embodiment of a radiation heater incorporating a reflector according to the present invention.

The radiation heater shown in Figure 1 comprises a source 1 of radiation such as an infra-red lamp or a heating element and a parabolic reflector 2 having a depth D,. The radiation source may be linear, in which case the reflector 2 will also be linear, or curved, in which case the reflector 2 will usually be curved along its length to correspond with the curvature of the radiation source 1. However, although the distribution of radiation from the reflector is satisfactory, a parabolic reflector occupies a substantial depth which is not generally available in domestic cookers.

The radiation heater shown in Figure 2 comprises a source 3 of radiation such as an infra-red lamp or a heating element and a dished reflector 4 having a flat base and substantially vertical side walls so as to give the reflector a depth D2. As with the embodiment of Figure 1, the radiation source may be linear or curved, but in the embodiment of Figure 2 it is not necessary to form a curved reflector. With such a dished reflector, the depth occupied by the reflector is less than that occupied by a parabolic reflector, but the distribution of radiation from the reflector is unsatisfactory.

The radiation heater according to the present invention as shown in Figure 3 comprises a source 5 of radiation such as an infra-red lamp or a heating element and a sectional reflector 6 having a depth D3. The reflector 6 is made up of a number of sections which may be planar or curved, for example partly parabolic, and which are positioned to intercept a portion of the radiation emitted by the source 5 and to reflect the radiation substantially vertically (with regard to Figure 3). The reflector 6 thus performs the function of reflector 2 of Figure 1, but occupies substantially only the depth of reflector 4 of Figure 2. That is to say, the reflector is relatively shallow, but provides a satisfactory distribution of reflected radiation while employing a minimum number of radition sources appropriate for the heated area.

The radiation source may be linear, in which case the reflector will generally be linear, although some curvature may be incorporated into the end portions of the reflector to compensate for the change in the distribution of emitted radiation towards the ends of the source. However, the radiation source may also be curved, in which case the sections of the reflector may be curved to correspond with the curvature of the radiation source.

Further, multiple radiation sources may be provided in which case it will be necessary to produce a reflector which is a compromise in order to obtain an even distribution of reflected radiation. Indeed, some experiment may be required in order to obtain an optimum result, but such experiments are well within the capability of a person skilled in the art.

In order to prevent direct emission of radiation in an upward direction(with regard to Figure 3) a reflector 7 may be arranged above the radiation source. Such a reflector may be a specular reflector or a diffuse reflector, and in the case of an infra-red lamp may be coated onto the inside or the outside of the quartz envelope of the lamp.

The reflector 6 may be made of a material such as a foil of metal, for example an iron-chromiumaluminium alloy such as that sold under the Registered Trade Mark KANTHAL, which may be coated with a light-reflecting layer such as gold or silver.

If desired, the reflector may have a base of thermal insulation material (see Figure 4) such as a ceramic fibre material or a microporous thermal insulation material so as to reduce heat loss through the reflector 6.

The radiation heater shown in Figure 4 is similar to the heater shown in Figure 3, but the heater shown in Figure 4 incorporates a reflector 10 which includes a peaked portion 11 beneath (with regard to Figure 4) the radiation source 9. The peaked portion 11 serves to redistribute radiation which is emitted substantially directly downwardly so as to obtain a more even distribution of reflected radiation.

Figure 4 also shows the reflector 10 supported by a base 12 of thermal insulation material and the radiation heater arranged beneath a smooth cooking surface 13 of an electric cooker of which the heater forms a part. The smooth cooking surface 13 may be made, for example, of a glass ceramic material.

The use of a reflector having a plurality of reflecting sections can, particularly where the reflecting sections are made of a metal foil, have the effect of increasing the number of apparent sources of radiation. Such an increase in the number of apparent radiation sources improves the visual appearance of the heater.

Claims

1. A reflector for a radiation heater, which reflector comprises a plurality of reflecting sections which are positioned substantially in a plane to intercept portions of radiation emitted by a radiation source and to reflect the radiation in a predetermined direction.

2. A reflector as claimed in claim 1, wherein the edges of the reflector extend out of said plane in order to prevent radiation escaping around the edges of the reflector.

3. A reflector as claimed in claim 1 or 2, wherein the reflecting sections are plane.

4. A reflector as claimed in claim 1 or 2, wherein the reflecting sections are curved.

5. A reflector as claimed in claim 4, wherein the reflecting sections are curved in the shape of a part of a parabola.

6. A reflector as claimed in any preceding claim, wherein the reflecting sections are linear.

7. A reflector as claimed in claim 6, wherein a degree of curvature is incorporated into the end portions of the reflecting sections.

8. A reflector as claimed in any one of claims 1 to 5, wherein the reflecting sections are curved along their length.

9. A reflector as claimed in any preceding claim, wherein the configuration of the reflecting sections is adapted to the use of a plurality of radiation sources.

10. A reflector as claimed in any preceding claim, wherein the reflecting sections incorporate a peaked portion to be positioned so as to oppose the or each radiation sources.

11. A reflector as claimed in any preceding claim, wherein the reflecting sections are made of a metal foil.

12. A reflector as claimed in claim 11, wherein the metal foil is coated with a light-reflecting layer such as gold or silver.

13. A reflector as claimed in any preceding claim, wherein the reflecting sections incorporate a base layer of thermal insulation material such as ceramic fibre or microporous thermal insulation material.

14. A reflector for a radiation heater substantially as hereinbefore described with reference to, and as shown in, Figures 3 and 4 of the accompanying drawings.

15. A radiation heater which incorporates a reflector as claimed in any preceding claim and a radiation source.

16. A radiation heater as claimed in claim 15, wherein the radiation source comprises an infrared radiation emitting lamp or a heater element in the form of a resistance wire.

17. A radiation heater as claimed in claim 15 or 16, wherein the radiation source is linear or curved.

18. A radiation heater as claimed in claim 15, 16 or 17 and including a plurality of radiation sources.

19. A radiation heater as claimed in any one of claims 15 to 18 wherein a reflector is positioned over the or each radiation source.

20. A radiation heater as claimed in claim 19, wherein the reflector comprises a specular reflector or a diffuse reflector.

21. A radiation heater substantially as hereinbefore described with reference to, and as shown in, Figure 3 and 4 of the accompanying drawings.

22. An electric cooker comprising a substantially smooth, radiation transmissive cooking surface and a radiation heater as claimed in any one of claims 15 to 21.

23. An electric cooker substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.