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
  • H05B6/74—Mode transformers or mode stirrers
• • 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
  • H05B6/74—Mode transformers or mode stirrers
  • H05B6/745—Rotatable stirrers

Definitions

• the walls W of the microwave M impose boundary conditions that cause the distribution of electromagnetic field energy within the volume of the oven to vary. This generates a standing wave energy pattern within the volume of the oven.
• the susceptor assembly 10 comprises a conventional, generally planar susceptor 12 having a field director structure generally indicated at reference numeral 14 connected thereto.
• the field director structure 14 is useful for redirecting and relocating the regions of high and low electric field intensity of the standing wave pattern within the volume of the oven.
• the positions of the redirected and relocated regions change continuously, further improving the uniformity of warming, cooking or browning of a food product placed on a susceptor assembly 10 that includes the field director structure 16.
• a vane may have its first end 16D and its second end 16E disposed at any predetermined respective points of origin and termination on the planar susceptor 12.
• the distance along the edge 16F of a vane between its first end 16D and its second end 16E defines the edge length of the vane.
• the vanes in the field director structure 14 may have any desired edge length, subject to the proviso regarding the length of the conductive portion 16C mentioned below.
• the vanes 16 may be integrally constructed from an electrically conductive foil or other material. In such a case the entire surface 16S of the vane is electrically conductive (e.g., as shown in Figure 2 for the vane 16-1). The length and width of the conductive portion 16C thus correspond to the edge length and width of the vane.
• planar susceptor 12 and a surface area 16S of a vane 16 intersect along a line of intersection 12L extending in a generally transverse direction with respect to the planar susceptor 12.
• a straight-edged vane 16 will produce a straight line of intersection 12L.
• a vane 16 having a bent edge or curved edge when intersected with the planar susceptor 12, will produce a bent or curved line of intersection 12L, respectively.
• the magnitude of the bend angle or the shape of curvature of the line of intersection will depend upon the angle of inclination of the vane to the planar susceptor. Whether the line of intersection is a straight line, a bent line or a curved line, the extension of the conductive surface of the vane will lie along the line of intersection.
• the conductive portion 16C of the vane 16 were in electrical contact with the lossy layer 12C the value of the component vector E x lying along the line of intersection 12L and the value of the component vector E 2 would be zero, for the reasons just discussed. However, the conductive portion 16C is not in electrical contact with the lossy layer 12C 1 but is instead spaced therefrom by the distance D. The conductive portion of the surface of the vane nevertheless exerts an attenuating effect having its most pronounced action in the extension of the conductive portion of the surface of the vane. Thus, the component vectors E x and £ z of the electric field of the wave have .only attenuated intensities "X 3 " and "z a ".
• Figure 7B is a plot showing total energy exposure for one full rotation of the turntable at each discrete point J, K and L. The corresponding waveform of the plot of Figure 1B is superimposed thereover.
• a crisping ring (intended for browning the edges of the pizza) provided with the pizza in the package was not used.
• the planar susceptor was placed directly upon a turntable of a microwave oven.
• frozen pizzas were placed directly on the planar susceptor and cooked at full power for 5 minutes, except for Example 5, which was cooked in a lower power over for 7.5 minutes.
• one group of three pizzas was cooked using only the planar susceptor without a field director structure, and another group of three pizzas was cooked using the planar susceptor with a field director structure of the present invention.
• the vanes of each field director were constructed using aluminum foil of 0.002 inch (0.05 millimeter) thickness, paperboard, and tape.
• the image of the bottom crust was divided into multiple concentric annular rings and the mean L value was calculated for each annular ring.
• the following examples are believed to illustrate the improvements in browning and browning uniformity that resulted from the use of different field director structures of the present invention.
• Vane 16 10 -3 is an example of a vane in which the substrate 16 10 N abuts the planar susceptor 12.
• the conductive portion 16 10 C-3 is positioned on the vane such that a top border 19T of non- conductive substrate material is exposed along the edge of the vane adjacent to the susceptor 12.
• the border 19T serves to space the conductive portion 16 10 C-3 of the vane 16 10 -3 a predetermined close distance 21 D away from the susceptor 12.
• the dimension 21 D measured in a direction orthogonal to the plane of the susceptor 12, lies in a range from 0.025 to 0.1 times the wavelength of the standing electromagnetic wave produced in the microwave oven in which the susceptor assembly 10 10 is being used.
• Vane 16 10 -5 is an example of a vane in which the conductive portion 16 10 C-5 is generally rectangular (similar to the conductive portion 16 10 C-4) but with rounded comers. The corners may be rounded at a radius dimension 15R up to and including one-half of the width dimension of the conductive portion 16 10 C ⁇ 5 (i.e., 15R ⁇ 0.5 width). When the corners are rounded the length of the conductive portion is defined by the radial extent of the conductive portion.
• the vane 16 10 -5 also has borders 19T, 19L 1 19D, 19E (similar to those shown about the vane 16 10 C-4). The dimension of the lower border 19L is indicated by the reference character 21L.
• Examples 18-20 tested the effect of varying the center gap between radially opposite conductive portions on arcing and overheating.
• Examples 15 and 16 the surface of the conductive portion was covered by the polyacrylic or polytetrafluoroethylene spray coating, respectively.
• the top and bottom edges of the aluminum conductive portion were covered only by incidental over-spray of the polyacrylic or polytetrafluoroethylene coatings.
• Tables 3, 4A, 4B and 5 also contain a column of alpha-numeric designators indicating the "Oven" used for the test. Each designator corresponds to a particular microwave oven manufacturer and model, as follows:
• the "Susceptor" in some of the examples contained in Tables 3 and 5 below is identified by a reference designation comprising hyphenated first and second numeric values.
• the first numeric value represents the polymeric substrate material of the susceptor, while the second numeric value denotes the thickness of the susceptor lossy layer metallization (vacuum deposited aluminum) based upon its measured optical density.
• the first numeric value denotes the polymeric substrate material, as follows:
• Examples 51-60 assessed the overall microwave cooking performance, specifically the ability of this configuration of the susceptor assembly to brown uniformly the bottom of a pizza. Percent browning ("% browning") of a pizza was measured in the same manner as described in connection with Examples 1 through 8. The measured % browning was averaged over three pizza samples.
• the base electric field increases to a level above that extant when the food or other article is present.
• the local intensity of the field along the edge of a conductive portion may be sufficiently high to exceed the breakdown threshold of the air causing an electric discharge in the form of an arc to occur.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Constitution Of High-Frequency Heating (AREA)
• Electric Ovens (AREA)
• Cookers (AREA)

Priority Applications (5)

Applications Claiming Priority (4)

Publications (3)

Family

ID=39136447

Family Applications (1)

Country Status (8)

Families Citing this family (2)

Family Cites Families (42)

• 2006
  • 2006-12-18 US US11/641,370 patent/US8367988B2/en not_active Expired - Fee Related
• 2007
  • 2007-08-15 JP JP2009526612A patent/JP5340154B2/ja not_active Expired - Fee Related
  • 2007-08-15 WO PCT/US2007/018016 patent/WO2008027191A2/en not_active Ceased
  • 2007-08-15 BR BRPI0714898-4A patent/BRPI0714898A2/pt not_active IP Right Cessation
  • 2007-08-15 EP EP07836829A patent/EP2057865A2/en not_active Withdrawn
  • 2007-08-15 AU AU2007290767A patent/AU2007290767A1/en not_active Abandoned
  • 2007-08-15 CN CN200780040199A patent/CN101690394A/zh active Pending
  • 2007-08-29 AR ARP070103848A patent/AR062594A1/es unknown

Also Published As

Similar Documents

Legal Events