Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/64—Heating using microwaves
  • H05B6/78—Arrangements for continuous movement of material
  • H05B6/782—Arrangements for continuous movement of material wherein the material moved is food
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/64—Heating using microwaves
  • H05B6/70—Feed lines
  • H05B6/707—Feed lines using waveguides

Definitions

• the present invention relates to a microwave applicator device for the treatment, in particular cooking, of relatively small or thin individual products, deposited on a metal support.
• the frequency band of the electromagnetic waves between 300 MHz and 300 GHz is designated by microwave.
• the object of the invention is to provide a structure suitable in particular for baking food products, for example cookies, in place on a metal surface and capable of operating, in very substantially reduced times compared to the cooking times of traditional ovens heated by pulsed hot air and / or infrared, cooking of comparable quality and in very good safety conditions and despite the use as a cooking support of said products of a metal surface, for example a grid or fixed floor or conveyor belt.
• the subject of the invention is a microwave applicator device in particular for cooking products on a metallic support, comprising at least one microwave generator and a metallic waveguide, in particular of rectangular section, characterized in that said waveguide forms a cooking enclosure, the floor of which consists of a removable metallic flat support, on which the products to be cooked are deposited.
• the waveguide is connected to the microwave generator by an auxiliary guide whose axis forms with respect to the axis of said guide an angle equal to the angle of Brewster or neighbor thereof and such that the electric field is in a plane perpendicular to the metallic plane support.
• said metal flat support is a sole or plate immobile with respect to the inverted U-shaped upper part of the waveguide during the application of the microwaves, the two ends of the guide being provided with a means of closing-confinement of the cooking chamber thus produced.
• said metal plane support is a conveyor belt, the two ends of the guide possibly being provided with means suitable for limiting the leakage of waves to the outside below the tolerated values, the direction of movement of the mat being parallel to the axis of the guide.
• the device of the invention comprises a plurality of waveguides paired in parallel forming a single-mode microwave cavity, the lower horizontal part of the guides being formed by a common conveyor belt .
• a conveyor belt whether the waveguide is single or multi-ducted, serves several waveguide cavities arranged in cascade above the upper strand of the belt, so that the products undergo during their moving on the carpet a succession of microwave applications.
• Figure 1 is a schematic vertical sectional view of a first embodiment of a device according to the invention.
• FIG. 2 is a schematic vertical section view of a second embodiment
• Figure 3 is a schematic side view of an alternative embodiment of the device of Figure 2.
• FIG. 1 there is shown at 1 a waveguide of rectangular section comprising, two sidewalls 2 and 3 and a ceiling wall 4, the floor wall being constituted by a separate flat support 5.
• the guide 1 and the flat support 5 are made of a good conductive metal and preferably non-magnetic.
• the guide 1 forms a closed enclosure (the opposite ends not being shown in FIG. 1) and only open on its underside, the opening being closed by the flat support 5 which is for example a sole or plate on which are deposited products 6, for example cookies, madeleines, or other biscuit, pastry, pastry products, of the same kind, which one wants to bake or whose humidity one wants to homogenize.
• the guide 1 is connected to a microwave generator (not shown in Figure 1) connected so that the electric field E generated in the guide 1 is substantially perpendicular to the metal plane support 5 during its longitudinal propagation.
• the assembly thus formed can form an individual cooking oven from which the bottom or cooking plate 5 can be extracted to load and unload products, the device operating like a traditional microwave oven.
• FIG. 2 illustrates another embodiment in which, on the one hand, several waveguides similar to guide 1 are paired or joined so as to form three rectangular conduits open on their underside and, on the other hand, the flat metal support 5 is constituted by a single element, common and more particularly by the upper strand of a conveyor belt T.
• the upper strand of the belt T circulates while being kept at a short distance (1 to 10 mm at the frequency 2450 MHz ) of the edge of the vertical separating partitions 8 and 9 of the adjoining waveguides forming a single-mode microwave cavity 11.
• the belt is driven in a direction 12 parallel to the axis of the conduits of the cavity 11.
• the waves are sent into each of the conduits of the cavity there substantially under incidence of Brewster, through openings 14 formed in the upper horizontal wall of the cavity 11.
• openings 14 are fixed auxiliary guides of rectangular section whose axes are inclined on the axis of the conduits of the cavity 11 by an angle of the order of the Brewster angle for the type of products 6 treated, that is to say around 30 ° with the horizontal, the emitted electric field remaining in a plane perpendicular to the metal mat.
• the width of the conduits of the cavity 11 is for example of the order of 8 to 10 cm for a microwave generator of frequency 2450 MHz + 50 MHz operating in TE 1Q fundamental mode, the height of the conduits being of the order of 4 to 5 cm, at a distance from the carpet of between 1 and 10 mm approximately and the length of the order of 60 to 120 cm.
• the frequency 915 MHz and more generally of the other frequencies for ISM applications these dimensions are different, substantially in the inverse ratio of the frequencies.
• the cavity 11 can of course include any number of different variable conduits, this number being able to be reduced to 1.
• FIG. 3 there is shown in side elevation a conveyor belt T driving the products to be cooked 6 successively in three aligned cavities 11 ', 11 ", 11"', for example identical to the cavity 11 in FIG. 2.
• Each cavity 11 ′, 11 ′′, 11 ′′ ’ single or multi-duct, comprises as many microwave generators G as ducts, arranged above the ducts and each connected to a duct by an auxiliary guide 15 inclined by a angle a equal to or close to the Brewster angle for the products to be treated with a direction of the electric field emitted in a plane perpendicular to the metal mat.
• the auxiliary guides 15 open into the respective conduits through the corresponding openings 14 which are arranged closer to the upstream end of the conduits than to the downstream end.
• the axis of the auxiliary guides 15 intersects the axis of the conduits of the cavities 11 ', 11 ", 11"' and define with him vertical planes parallel to the direction of movement 12 of the mat T
• the length of the cavity conduits is such that at the downstream end there is no need to provide a sophisticated anti-leakage device, the microwave energy having been practically all absorbed
• the distance between said end and the point junction between the cavity and the auxiliary guide 15 being much greater than one or more wavelengths
• an anti-leakage device such as a wave trap, curtain of suspended chains symbolized in 16, microwave absorbing materials
• an additional heating / cooking device symbolized in 17 providing for example heating by pulsed air or by infrared radiation.
• the products 6 undergo three successive applications of microwaves, interspersed with a rest phase or auxiliary heating / cooking
• the residence time of the products in the cavity conduits naturally depends on their nature and on the type of cooking desired.
• the number of successive cavities can of course vary and be greater than 3
• the invention applies to all types of cavity or waveguide, of rectangular, square, semi-circular or other cross-section, insofar as the bottom wall of the cavity or of the guide can be replaced by a flat metallic separable support, movable or not movable relative to the body of the cavity or the waveguide and on which are placed, directly or not, the leathers, these being constituted by individual elements relatively small dimensions
• Guides and cavities generally operate in T ⁇ ⁇ Q1 mode, in one of said frequencies for ISM applications
• the invention can be applied to something other than cooking such products, for example, drying or regulating humidity profiles, as well as any heat treatment, in general.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Constitution Of High-Frequency Heating (AREA)
• Control Of High-Frequency Heating Circuits (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9487918

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (25)

Family Cites Families (18)

• 1996
  • 1996-01-19 EP EP96901421A patent/EP0875128A1/de not_active Withdrawn
  • 1996-01-19 JP JP09525723A patent/JP2000503452A/ja active Pending
  • 1996-01-19 WO PCT/FR1996/000093 patent/WO1997026777A1/fr not_active Ceased
  • 1996-01-19 US US09/101,887 patent/US6153868A/en not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events