Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1983-09-26
1986-03-11
Albritton, O. L.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
219411, F24C 706
Patent
active
045756163
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a domestic infra-red radiation oven.
Domestic ovens comprising radiation elements which emit radiation in the infra-red wavelength range are used both for conventional cooking and baking and for thawing and heating of precooked frozen food portions. The advantage of radiation elements over heating elements, which by heating the air transfer heat to the oven load, is that the transfer of heat is quicker and thus results in shorter treatment times. It is known in connection with the thawing of frozen, aqueous food that IR-radiation of a wavelength less than 1.0 .mu.m readily penetrates into the food whereas for wavelengths greater than 1.4 .mu.m the radiation is absorbed substantially in the surface layer. For wavelengths in the range of 1.0-1.4 .mu.m both penetration and absorption are obtained.
The main object of the invention is to provide an oven of the said type which is designed for thawing and heating of precooked, frozen food portions and which, compared to a convection oven, requires a considerably shorter treatment time and at the same time reduces the consumption of energy.
Another object is to design and locate the radiation elements in such a way that a uniform heating of the load is achieved.
Still another object is to prevent, in the event that the oven has a door with an inspection glass, short-wave infra-red radiation from escaping to any significant extent through the door.
An embodiment of the invention will now be described with reference to the accompanying drawings.
FIG. 1 is a longitudinal section through an oven made in accordance with the invention.
FIG. 2 is a cross section through the oven of FIG. 1.
FIG. 3 is a circuit diagram of a system for controlling the energy supply and the treatment time suitable for the oven.
FIG. 4 is a modification in cross section of a portion of the oven of FIG. 1.
The oven has a generally parallelepiped oven space 10 defined by two side walls 11, 12, a top wall 13, a bottom wall 14, a rear wall 15 and a front wall constituted by a door 16. A support plate 17 carries the oven load 18, which in the example is a frozen fish au gratin placed in a tin 19, suitably of aluminium with blackened surface. The support plate is of a material transparent to IR-radiation, for example temperature-resistant glass. Alternatively, the support plate can be in the form of a gridiron. The support plate rests on flanges 20 provided in the side walls 11, 12. Such flanges can be disposed at different levels in the oven so as to allow adjustment of the position of the support plate.
At the bottom wall 14 of the oven a radiation source is arranged for long-wave IR-radiation in the wavelength range of 3-6 .mu.m. The radiator comprises a tube element 21 bent in a meandering shape. The tube element is disposed in a reflector 22 which reflects downwardly emitted radiation to the underside of the tin 19 in order to heat it. Thus, the tube element 21 heats the tin, from which heat is transferred to the food portion au gratin by conduction. This type of radiator is suitable in the present case because frozen food on thawing and heating is often positioned on a vessel which is not pervious to IR-radiation. Furthermore, the lower radiation element is often soiled by grease and food falling onto it and sticking thereto by burning. A tube element of metal is easier to clean than the quartz-tube radiators which are used as upper radiation elements and which will be described in the following. The extension of the reflector 22 preferably coincides with the extension of the tin 19, which is shown as a double-tin, i.e. it comprises two tins which are held together and each one contains one portion.
If the tube element 21 is selected for a surface load.gtoreq.3 W/cm.sup.2 it has proved to be suitable to place the support plate 17 such that the distance between its supporting surface and the tube element will be about 30 mm. Further, the tube element should have a thermal mass which does not exceed 7 g/dm tube length to ensure that the time derivative for the increase
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Aktiebolaget Electrolux
Albritton O. L.
Miller Alfred E.
Walberg Teresa J.
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