U.S. patent number 3,591,751 [Application Number 04/861,418] was granted by the patent office on 1971-07-06 for browning apparatus for use in a microwave oven.
This patent grant is currently assigned to Teckton, Inc.. Invention is credited to Costas E. Goltsos.
United States Patent |
3,591,751 |
Goltsos |
July 6, 1971 |
BROWNING APPARATUS FOR USE IN A MICROWAVE OVEN
Abstract
In a microwave oven wherein a portion of food is to be cooked,
microwave coupling devices are located in contact or close
proximity to the food for the purpose of browning the food. The
microwave devices, in one embodiment, include a plurality of metal
rods, each having a length that is a multiple of a half wavelength
with respect to the microwave energy within the oven. The microwave
devices effectively transform the microwave energy into thermal
energy in which form the energy causes the browning of the food
contained therein.
Inventors: |
Goltsos; Costas E. (Weston,
MA) |
Assignee: |
Teckton, Inc. (Waltham,
MA)
|
Family
ID: |
25335737 |
Appl.
No.: |
04/861,418 |
Filed: |
September 26, 1969 |
Current U.S.
Class: |
219/728; 426/243;
219/730; 219/759; 219/745 |
Current CPC
Class: |
H05B
6/6494 (20130101) |
Current International
Class: |
H05B
6/64 (20060101); H05b 009/06 (); H05b 009/04 () |
Field of
Search: |
;219/10.55,10.81 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truhe; J. V.
Assistant Examiner: Bender; L. H.
Claims
What I claim is:
1. Microwave coupling thermal conducting device for generation of
thermal energy for use in the browning of food products, said
coupling device being contained in a microwave oven including a
microwave source and comprising a plurality of metal rods, each
having a length that is substantially a multiple of a half
wavelength with respect to the frequency of the microwave source,
dielectric means supporting said rods in spaced relation to each
other with said rods positioned to contact food being cooked and to
respond to the microwave source energy causing an increase in
microwave currents on the surface of said rods thereby generating
the heat required for browning of the food at least in the areas
where the food is touching said rods.
2. Microwave coupling device as defined in claim 1 wherein said
plurality of metal shaped rods are each parallel one to the
other.
3. Microwave coupling device as defined in claim 1 wherein said
dielectric means are freely movable within said oven.
4. Microwave coupling device as defined in claim 2 and further
including a dielectric support board with said rods supported
thereon.
5. Microwave coupling device as defined in claim 1 and further
including a second plurality of metal rods, and a second dielectric
means supporting said second plurality of rods, each of said rods
having a length that is a multiple of a half wavelength with
respect to the frequency of the microwave source and supported in
relatively close proximity to the food being cooked, said second
plurality of metal rods adapted for arrangement in facing
relationship to said first plurality of rods on the other side of
the food.
6. Microwave coupling device as defined in claim 5 wherein said
metal rods of said first plurality are all parallel to each other
and the metal rods of said second plurality are all parallel to
each other, and further wherein said first and second plurality of
metal rods lie respectively in parallel planes.
7. In a microwave oven including a source of microwave energy,
apparatus for use in the browning of foods comprising dielectric
supporting means, a plurality of elongated metal elements supported
along at least a portion by said dielectric supporting means, said
elements being spaced with a surface of at least one of said
elements contacting the food being cooked and to respond to the
microwave source energy thereby causing concentrated heating of the
food in the area surrounding the contacting surface of the
element.
8. Apparatus as defined in claim 7 wherein said plurality of metal
elements includes a plurality of rods spaced from each other and
wherein said dielectric supporting means includes an extending
supporting portion coupled to said rods at a portion intermediate
the ends of said rods.
9. Apparatus as defined in claim 7 wherein said plurality of metal
elements includes a plurality of rods spaced from each other having
ends that are supported by said dielectric supporting means.
Description
BACKGROUND OF THE INVENTION
The present invention pertains generally to microwave cooking, and
in more particular to a microwave coupling/thermal conducting
device located within the oven for causing a browning of the food
contained therein.
One of the early dissatisfactions noticed with food that had been
cooked by the use of microwave energy was the absence of a browning
of the food. It is desirable to brown food cooked in a microwave
oven for two principal reasons. First, browned food has a more
acceptable appearance, and more important, in many cases browned
foods taste better. Both of these factors are important marketing
factors in the acceptability of microwave ovens.
Certain bulky foods tend to brown because of prolonged heating
periods required to cook them and because of the attendant surface
concentration in the heating of the foods. However, these effects
are not appreciably present in most foods. Therefore, one approach
was to use several different kinds of coatings to enhance surface
coloration. One such attempt used additives to enhance browning.
The disadvantages associated with the use of additives was that
they had to be carefully controlled so that the flavors and texture
characteristic of the foods was not altered by their use.
Another method investigated involved use of a high-loss dielectric
material placed adjacent to the food to be cooked. The high-loss
properties of the dielectric caused it, upon microwave radiation,
to attain higher temperatures than adjacent food. Some browning of
the food was caused by the radiation from the hotter high-loss
dielectric material. However, the concentration of heating by this
process was inefficient and the placement of the dielectric
material was difficult to control. In addition, this technique
caused food contamination and the equipment tended, in general, to
be both expensive and fragile.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide
improved thermal food browning apparatus.
It is a further object of the present invention to provide thermal
food browning apparatus that is moderately priced, easy to
fabricate, and extremely durable.
It is still another object of the present invention to provide an
apparatus that efficiently browns the food leaving an appearance of
searing or broiling.
A further object of the present invention is to provide food
browning apparatus that uses resonant inductive browning means.
The aforementioned objects are provided in the present invention by
the use of a plurality of metal rods, each having a length that is
a multiple of a half wavelength with reference to the microwave
source frequency and with the rods supported in relatively close
proximity to or in contact with the food being cooked. In one
embodiment, these metal rods are embedded in and supported by a
dielectric such as a fiber glass board. Food is in contact or close
proximity to these rods, which can be arranged on both sides of the
food. The use of the half wavelength metal rods which respond to
the microwave source causes an increase in the microwave currents
on the surface of the rods and effectively causes the browning of
the food contained in the oven.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a microwave oven that has thermal browning
apparatus,
FIG. 2 shows one embodiment of the thermal browning apparatus of
the present invention, and
FIG. 3 is a cross-sectional view showing a piece of food located
between a double row, rod arrangement.
DETAILED DESCRIPTION
Referring in particular to FIG. 1, there is shown microwave oven
10, which can be any of a variety of conventional ovens using
microwave energy for cooking. Within oven 10 there is disposed a
dielectric board 12 positioned on the bottom 11 of the oven
interior. This board 12 may be made of fiber glass, ceramic,
plastic or similar dielectric material. The board is designed to
support a plurality of metal rods 14. The rods 14 are supported at
a fixed distance above the board 12 by a center support. Food 16
may be placed on and supported by, rods 14. The oven 10 includes a
microwave radiating source (not shown) for cooking the food. By
making the lengths of the rods 14 integer multiples of a half
wavelength with respect to the frequency of the microwave source,
there is caused a resonant increase in the microwave currents on
the surface of the rods. By the use of a resistive metal for rods
14, the resonant currents will cause the rods to attain much higher
temperatures than the average temperature of the food. One such
desirable rod was found to be one made of stainless steel. This
material also had the advantage of not contaminating the food and
is a noncorrosive material which can be easily cleaned. Similarly
board 12 should be made of a material which is easy to clean. The
rods 14 should also have a low thermal mass so that high food
heating efficiency is retained. Stainless steel is a moderately
priced material which is easy to fabricate and extremely durable
and refractory, for the purpose.
With the use of apparatus similar to that shown in FIG. 2, at 2,450
Megahertz, a Fiberglas board (0.060 inch thick) was drilled with
two rows of half-inch spaced holes. The rows were 2.4 inches apart
and 0.048-inch diameter stainless steel rods with their ends bent
to match this separation were inserted into the board. The food,
which was a small steak, was supported in the center of the oven
with similar resonant grids on both sides as shown in cross section
in FIG. 3 where rows 14 and 14' of rods are suitably supported in
parallel arrangement by boards 12. The steak was cooked to a medium
rare condition, surface grid browned after 40 seconds of exposure
to the microwave energy levels provided by one particular oven.
As a matter of convenience, the frames of dielectric bases 12 may
be freely movable within the oven so that they may be placed on top
of the food for top browning. The number and spacing of the rods
may vary depending upon the amount of heat desired for browning of
the food.
With the use of a microwave source that is oriented on the top of
the oven and with the further use of rod grids above and below the
food product, more browning is observed on the top surface of the
food than on the bottom. This is caused by the shadowing effect
provided by the top rod structure. This condition may be varied to
provide essentially equal browning on both surfaces of the food by
providing for two microwave source feeds, one from the top and the
other from the bottom of the oven 10. Similarly, if a single
microwave source is used, this can be coupled with a hybrid coupler
to provide dual, top and bottom feeds.
An alteration in the length of the metal rods to correct for the
dielectric loading of the adjacent food has been found to be not
required. This is probably due to the limited contact made by the
rods with the irregular surface of the food.
Certain modifications also are contemplated as falling within the
scope of the present invention. For example, various shapes of
support boards can be used and also different shaped rods arranged
in nonparallel and other configurations.
* * * * *