FR2543268A1 - RADIANT ENERGY HEATING AND / OR COOKING APPARATUS - Google Patents

Abstract

THE INVENTION CONCERNS HEATING OR COOKING APPLIANCES. A RADIANT COOKING AND / OR HEATING APPARATUS 10 USES A HIGH TEMPERATURE HEATING ELEMENT 11 SUCH AS TUNGSTEN FILAMENT, AND A REFLECTOR 14 WHICH DIRECTS THE RADIANT ENERGY TOWARDS A COOKING SURFACE. A LAYER OF MATERIAL 18A, 18B ABSORBING RADIATION AT VISIBLE WAVELENGTHS IS PLACED BETWEEN THE RADIANT ENERGY SOURCE AND THE COOKING SURFACE 16A, TO REDUCE THE RADIATION VISIBLE BY A USER, WHILE TRANSMITTING THE FOOD TO BE COOKED THE RADIATION CORRESPONDING AT LEAST TO NEAR INFRARED. APPLICATION TO HOUSEHOLD EQUIPMENT.

Description

The present invention relates to a heating or cooking appliance

  of foods or other, and it relates more particularly to a new heater and / or radiant energy cooking having a reduced emission of visible light.

  A food cooking appliance is well known

  using a combination of conduction-transmitted energy and radiant energy, which includes an element

  heated under a top plate capable of transmitting

  put the radiation As an example, the device of

  cooking 1 of the figure la uses a block 2 which is an iso-

  thermal lant, typically made of a ceramic material or the like, in which channels 3 are formed with a meandering pattern,

  to contain a heating coil 4 producing energy

  The energy produced by the heating coil 4 is transmitted through an upper plate 5 capable of transmitting radiation. Thus, food heating energy is applied to a cooking utensil (not shown) adjacent to the surface. external to the upper plate, when the coil 4 receives electric current-due to the connection of the ends 6 of the coil to a suitable source of energy Another cooking apparatus 8 uses a thin-film resistance element, 9, Under a top plate 5 'capable of transmitting radiation In a manner similar to that of apparatus 1, heating energy is imparted to food placed above the outer surface 5a' of the top plate , under the effect of the connection of

  conductors 6 'of the heating element to the energy source.

  Typically, a heating source provides energy at both below-average wavelengths

  red and visible wavelengths.

  prior art cooking apparatus at relatively low temperatures, not exceeding

  characteristic 14000 K, since the use of temperature

  erations can lead to visual discomfort

  the user of the heater during the preparation

  Due to the relatively low temperatures that are used, the energy at wavelengths

  far infrared is absorbed by the superior plate

  5 or 5 ', so that it quickly reaches very high temperatures At such low temperatures (eg 14000 K), the specific power density

  Me) in the heating coil 4 or 9 is relatively small.

  and appreciable energy is produced in the far infrared region, i.e. radiation having a wavelength greater than about 2.6 microns, which further increases the temperature of the plate Upper plate is highly susceptible

  to break due to the extreme thermal shock that occurs

  duit in case of overflow during cooking.

  It is therefore extremely desirable to provide a

  heater with radiant energy function-

  at a significantly higher temperature, to produce

  is a higher percentage of energy in the near-infrared region, used for cooking food, while reducing the extra energy at the visible wavelengths that is produced by the operation at

a higher temperature.

  According to the invention, a heating apparatus

  firing and / or radiant energy cooking uses:

  at high temperature, such as a tungsten filament or the like, for radiating at least one radiation

  infrared wavelengths and visible towards an over-

  where the infrared radiation is to be applied to cook food placed adjacent to that surface; and means, placed between the element producing heating energy and the surface,

  to absorb radiation at visible wavelengths

  ble. In a presently preferred embodiment of the new heater and / or radiant energy cooking appliance, the heating element is a filament tube of

  tungsten placed practically in the focus of an infrared receiver

  red The means of absorption of energy at visible wavelengths consist preferably of a layer of iron oxide The absorbent layer may be placed around

  of the heating tube or transversally to the opening

  infrared reflector, and intercepts the

  visible before the radiant energy meets an upper plate Several assemblies each comprising a heating tube, a reflector and an absorption element

  visible wavelengths (or a spectral filter that cuts

  band) can be placed in a network below at least one upper plate, to define a total area from which infrared radiation is emitted

heating the food.

  The object of the invention is therefore to provide a new heating and / or radiant energy cooking appliance in

  which proportion of visible light is reduced.

  The rest of the description refers to the drawings

  annexed which represent respectively:

  Figures la and lb: perspective views of

  firing wires of the prior art; Figure 2 is a perspective view of a presently preferred embodiment of a heater and / or radiant energy cooking appliance according to the principles of the invention; and Figure 2a: a graph showing the relationship between the specific energy density and the radiation wavelength for various temperatures of a heating element, and useful for understanding the operation of the invention. Referring now to FIG. 2, it will be noted that the new radiant energy heating and / or cooking apparatus 10 uses means 11 producing radiant energy, such as a tungsten filament or the like. The filament is preferably enclosed in a tube

  12 of a material that significantly transmits at least

  infrared wavelengths in the range of about 1.0 micro-

  meter at about 3.0 micrometer The filament 11, which may be a helically wound filament whose longitudinal axis

  coincides with the central axis of the cylindrical tube 12,

  Preferably, the heating tube is mounted by means not shown but well known in the art, with the filament II practically at about focus of a reflector 14 The function of the reflector 14 is to collect

  at least the radiant energy at the wavelengths below

  red, and focus to an opening 14a of the reflector An upper plate 16 is placed so as to extend transversely over the entire opening 14a of the reflector; and the top plate may be made of any material substantially radiation-transparent in the region of the spectrum corresponding to the near infrared, such materials including glasses (such as germanium glass, treated laminated glass

  chemically, etc.), quartz and similar materials.

  Thus, almost all the radiation produced by the filament 11 is directed towards the opening 14a of the reflector

  and to the upper plate 16 which is above.

  This radiant energy includes the desired energy in the near infrared, for cooking food, and it also includes unwanted energy at visible wavelengths. According to the invention, a filtering element

  light at visible wavelengths, 18 is

  wedged between the radiant energy source (filament 11) and the outer surface 16a of the upper plate The energy

  radiating at visible wavelengths is therefore practically

  absorbed inside the apparatus 10, and the level

  radiation at visible wavelengths that is capable of

  The light absorbing element at visible wavelengths, 18, may consist of a flat layer 18 interposed between the reflector opening 14a. and the

  upper plate 16; and the flat layer 18a can advantageously

  The upper plate 16 must be removable (for cleaning or for similar purposes), the layer 18a may be a separate element, mounted separately transversely to the opening. 14a of the reflector According to one variant, a layer 18b of material absorbing the lengths

  visible waves can be made on the outer surface.

  The layer 18a or 18b may be made from any material having a significantly higher absorption power of the radiant energy in the region of the lengths of the heater. visible waves (from about 0.4 microns to about 0.7 microns), and significantly lower absorptive power, or attenuation, of radiant energy in the near-infrared wavelength region (from about 1 micron to about 3 microns) The absorbent member may also be of a red-transmitting material, such as a glass or the like, in the form of a separate member, or

  distributed in another element, for example in the tube 12.

  Iron oxide is a material that has been found to be particularly

  especially useful for absorbing energy at lengths

  visible waves in layer 18a or 18b.

  iron oxide by the method described and claimed in US Patent Application 322,421, filed Nov. 18, 1981, and incorporated herein by reference in its entirety. This application discloses and claims the manufacture of a coating

  of iron oxide, having any desired thickness

  ble, by spraying an alcoholic solution of ferric chloride on a hot surface (which can be obtained by operating the filament II for a period of time before effectively spraying the ferric chloride solution in alcohol). an iron oxide coating is particularly advantageous in that most of the radiation corresponding to the visible wavelengths of blue and green is absorbed, whereas the radiation at the infrared wavelengths

  This is transmitted effectively through

  to the absorbing layer 18 and then through the

  than upper 16, a part of the corresponding radiation

  visible wavelengths of red, thanks to which the use of

  the viewer sees the top plate with a neighboring color

  dark red, indicating that the device is in operation

tioning.

  It should be noted that the tube 12 can be removed and the filament 11 placed inside a hermetically sealed enclosure limited by the reflector 14 and the upper plate 16. It should also be noted that other means can be used. of heating and that these may have

  forms other than the elongated filament which is

  In particular, meandering filaments having a mean axis which may be a curve in

  a space with two or three dimensions, as required by the use of

  In a similar way, one can

  use in a single device 10 additional sets of

  formed by the combination of the heating element 11, the reflector 14 and the visible light filtering means 18, as shown by the additional sets of reflectors 14 ', filaments 11' / protective tubes 12 ', associated spectral filtering means 18 'and upper plates 16' (all shown in dotted lines) which are placed to the left and to the right of the assembly shown in continuous lines in FIG.

  heating systems, it is also possible to use

  Each of the upper plates 16 and 16 'can be integrated into a unitary element defining a surface above which there is an area on which food can be cooked, or a volume in which it is possible to cook. It should also be noted that a thermal insulation can be established outside the apparatus 10, if necessary. The apparatus 10 is not limited to heating or cooking food and can be used for any demanding job

  irradiation of at least one object with infra-

  red. FIG. 2a will now be considered in which the radiation wavelength A is worn with an increasing value along an axis of abscissae 21 and

  is expressed in micrometers The spectral density of

  Meà is centered on the principal ordinate 22 and e 2 is expressed as 105 W / (m Pm) The relative amplitude of light at visible wavelengths V (>) is carried along an axis a secondary ordinate 23 A curve 25 (shown in dotted lines) is related to the secondary ordinate axis 23 and indicates the relative sensitivity

  of the human vision A family of curves in line

  tinu 27a-27g represents the relative power density, relative to the principal ordinate axis 22, of the radiation produced by a source operating at temperatures ranging from 20000K (curve 27a) to 32000K (curve 27 g) in increments of 2000 K A dotted curve 29 indicates

  the wavelength at which the density of

  maximum, depending on the temperature of the filament.

  Another dotted curve 30, at a wavelength of about 2.6 microns, indicates the wavelength above which infrared radiation is found which practically does not pass through characteristic upper plates; it is desirable that the majority of infrared radiation appear below line 30,

  and it is also desirable that the position on the cour-

  be of maximum power density 29 which corresponds to the particular filament temperature used is at a wavelength greater than about 1.0 micrometer, to maximize the proportion of available near-infrared radiation Similarly, the area of a selected radiation curve 27 that is located below

  the visible light curve should be as low as

  possible We see that filament temperatures included

  between about 20,000 K and about 30,000 K satisfy these requirements.

  The highest temperatures are more preferable

  because the higher Me X power density values that correspond to them can

  significant decrease in material costs

  This must be a compromise between this

  cost reduction and additional radiation for the long-term

  visible wavelengths that are produced at higher operating temperatures; it is considered at the present time that a preferred temperature of about 26000 K

  (curve 27 d) represents the best compromise.

Claims (16)

  1 radiant energy heating and / or cooking apparatus (10), characterized in that it comprises: means (11, 12) for producing radiant energy, at least at infrared and visible wavelengths ; means (16) for defining a surface at which radiation at least the infrared wavelengths is to be provided for a cooking operation; and means (18) placed between the heating means (11) and said surface (16a) for reducing the amount of visible-wavelength radiation that is present on said surface. 2 Apparatus according to claim 1, characterized in that it further comprises means (14) placed around the heating means (11, 12) for directing almost all of the radiation to infrared wavelengths,   at least through said surface (16a).   Apparatus according to claim 2, characterized   in that the radiation reduction means (18) comprises   take a layer (18 a, 18 b) of absorbent material   radiation at visible wavelengths.   Apparatus according to claim 3, characterized in that the absorbent material absorbs at least the light visible blue and green.   Apparatus according to claim 4, characterized   in that said material is iron oxide.   Apparatus according to claim 2, characterized in that the heating means consist of a filament   (11) placed inside the means of direction of the radiation- (14).   Apparatus according to claim 6, characterized in that the heating means further comprises a   element (12) enclosing the filament (11).   Apparatus according to claim 7, characterized in that the radiation reduction means (18b) is   formed on the element (12) enclosing the filament.   Apparatus according to claim 8, characterized in that the filament (11) has an elongated linear shape; the element enclosing the filament is a tube (12) of material   re transmitting the radiation that is formed around the filament   is lying; and the radiation steering means (14)   stand in a parabolic section channel with the filament (11) placed along his hearth.   Apparatus according to claim 6, characterized in that the filament (11) has an elongated linear shape; the radiation steering means (14) consist of a parabolic section channel with the filament placed along its focus; and the radiation reducing means (18) consists of a layer (18a) of absorbent material   the radiant energy in the spectrum corresponding to the   visible wavelengths, extending transversely compared to an opening of the canal.   11 Apparatus according to claim 1, characterized in that the heating means (11, 12) operate at a temperature of between about 20000 K and about 30000 K.   Apparatus according to claim 11, characterized   in that the heating means (11, 12) operate at a temperature of about 26000 K. Apparatus according to claim 1, characterized in that it further comprises at least one heating means   (11 ', 12'), placed on the same side of said overhead   the face (16 a) that the aforementioned heating means (11, 12) and additional means of radiation reduction (18 a ') placed between this surface and the heating means additional (11 ', 12').   Apparatus according to claim 13, characterized   in that it further comprises additional radiation directing means (14 ') associated with the additional heating means (11', 12 '), to ensure that substantially all of the radiation at the lengths of the infrared waves from additional heating means crosses said surface (16 a).   Apparatus according to claim 13, characterized   in that the surface (16 a) is a two-dimensional surface.   Apparatus according to claim 13, characterized in that the surface (16a) is a three-dimensional surface defining a volume in which at least one object can be heated by the radiation at infrared wavelengths crossing this surface.