US3789178A

US3789178A - Microwave heating apparatus

Info

Publication number: US3789178A
Application number: US00298535A
Authority: US
Inventors: P Harhen
Original assignee: SAGE LABORATORIES
Current assignee: MICRO-QUARTZ TECHNOLOGY Corp 1010 LYNDALE AVE NORTH MINNEAPOLIS MN 55141 A CORP OF; SAGE LABOR INC US; SAGE LABORATORIES
Priority date: 1972-10-18
Filing date: 1972-10-18
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29

Abstract

A combination microwave and gas oven having a divider shelf preferably horizontally disposed thereby dividing the oven cavity into a cooking section and a section containing the gas heating apparatus. The outer boundary of the shelf forms a low impedance choke with a perimetrical shelf holder thereby terminating microwave energy fed to the cooking section and preventing degradation of the gas heating apparatus disposed therebelow.

Description

FIELD AND BACKGROUND OF THE INVENTION The present invention relates in general to an oven having a microwave cooking section and a second section segregated from the microwave energy. The sec-. ond section may contain an alternate heat source which is preferably gas operated. In accordance with this invention there is provided a divider shelf preferably having a series of perforations therein for use in the oven and constructed to form a low impedance choke along its outer boundary for electrically isolating the cooking section of the oven from the section containing the alternate heat source.

One of the problems encountered in constructing a combination microwave and gas oven is that with known ovens there is a deterioration of gas heating apparatus due to the radiated microwave energy. Thus the gas heating apparatus may have to be replaced or frequently maintained.

Accordingly, an object of the present invention is to provide a combination oven having both a source of microwave energy and an alternate heat source such as a gas source, and including an isolating shelf dividing the oven into first and second sections. The first section is a cooking section and the second section contains the alternate heating source. In a preferred embodiment the first section is disposed above the second section.

Another object of the present invention is to provide a combination oven in accordance with the preceding object wherein the divider shelf defines a low impedance choke at its outer boundary with a peripheral holder for the shelf, thereby electrically isolating the cooking and gas apparatus sections of the oven.

A further object of the present invention is to provide a combination oven in accordance with the preceding objects wherein there is less degradation of the alternate heating source due to the radiated microwave energy than is the case with conventional combination ovens. Because there is less degradation of the gas heating source it need be replaced less frequently and maintained less frequently.

SUMMARY OF THE INVENTION To accomplish the foregoing and other objects of this invention the microwave heating apparatus of the present invention comprises an oven having side walls and a door, a shelf disposed in the oven for dividing the oven into first and second sections, support means secured to the inner surface of the oven for supporting the shelf, a source of microwave energy, a waveguide coupling the microwave energy from the source to the first section of the oven, and an alternate heating source disposed in the second section of the oven. In a preferred embodiment the first section of the oven is disposed above the second section of the oven and the divider shelf is preferably horizontally disposed. The shelf has at least one opening therethrough, and in a preferred embodiment has a series of perforations therein for permitting heat to pass from the lower section of the oven to the cooking section of the oven when using the alternate heating source. The outer boundaries of the shelf along with the shelf supporting means are constructed to form a half-wavelength choke preferably about four sides of the oven. Usually, the two side walls define two sides of the oven, the back wall defines the third side and the door defines the fourth side of the oven. A number of different embodiments for the half-wavelength choke are discussed hereinafter with reference to the detailed description of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS Numerous other objects, features and advantages of the invention will now become apparent upon a reading of the following detailed description taken in conjunc tion with the accompanyingdrawings in which:

FIG. 1 is a cross-sectional view through a combination oven constructed in accordance with the principles of the present invention;

FIG. 2 is a fragmentary view in the vicinity of the half-wavelength choke showing the same in a slightly larger scale than indicated in FIG. 1;

FIGS. 3-6 show four alternate embodiments for the choke illustrated in FIGS. 1 and 2; and

FIG. 7 is a fragmentary view of a preferred structure for the choke provided between the shelf and door.

DETAILED DESCRIPTION In the following description like reference numerals refer to corresponding like parts throughout the several views of the drawing. Referring now to the drawings and in particular to the cross-sectional view of FIG. 1, there is shown a combination oven 10 having a bottom wall 12,

side walls

14 and 16, top wall 18 and door 20. The oven is divided into an upper section 22 and a lower section 24 by shelf 26 which is shown as having a food container 28 resting thereon. The microwave energy is fed from a microwave source (not shown) by. way of wave guide 30 into upper section 22 of the oven. The lower section 24 of the oven housed a gas log 32 which is suitably supported by a bracket 34 at one end and by a bracket 36 at the other end. A gas supply (not shown) couples to port 38 and selectively introduces gas to log 32. The gas log 32 may be of conventional design and includes a series of small apertures 40 through which the gas is expelled creating a flame when lighted. A conventional pilot light (not shown) may be used to cause ignition of the gas.

The shelf 26 is provided with a series of perforations 42 and when there is no microwave energy being introduced by way of wave guide 30 but a gas flame is being generated from gas log 32 then the heat may rise by means of these perforations 42 into the upper section 22 of the oven thereby permitting a cooking of the food disposed therein.

In order to prevent the microwave energy coupled by way of wave guide 30 from reaching the lower section 24, the shelf 26 is constructed at its outer boundary or edge 27 with a Z-shaped bracket 29 and downtumed end 31. An L-shaped bracket 33 is fastened to the side walls, back wall and door and has the bottom leg 29A of bracket 29 resting thereupon. The structure including the L-shaped bracket 33, Z-shaped bracket 29 and downtumed end of shelf 26 defines a half-wavelength choke. Thus, the microwave energy that is introduced into section 22 is terminated by the short circuit impedance presented at the interface between the walls of the oven and the outer bondaries of the shelf by the half-wavelength choke. In order to more readily consider the half-wavelength choke arrangement reference is now made to the enlarged view of FIG. 2.

'FIG. 2 shows the shelf 26 at its outer boundary 27 including the downtumed end 31. The Z-shaped bracket 29 is affixed to the underside of shelf 26 by welding or the like. Bracket 29 and shelf 26 define cavity 25. The bottom leg 29A of bracket 29 rests upon the horizontal leg of L-shaped bracket 33. A gap g is provided between the bottom termination of end 31 and the top surface of bottom leg 29A. The choke is dimensioned so that there is a quarter-wavelength distance (referenced to the center of the operating band) from the top of the shelf to the middle of the gap g and also from the bottom of the shelf to the top surface of bottom leg 29A as is indicated in FIG. 2. The distance d in FIG. 2 is preferably equal to or lesos than a quarterwavelength and thus primarily only the undersurface 27A of outer boundary 27 functions as the low impedance short to the microwave energy.

FIG. 3 is another embodiment of the invention particularly useful when, for example, many shelves are going to be used in the oven and it is preferred that they each use 2 minimum amount of vertically measured space. The embodiment of FIG. 3 includes a shelf 26 having an outer boundary 27 and a downtumed end 31 defining a gap g with leg 29A. A Z-shaped bracekt 29 is. secured to the undersurface of shelf 26 and has its bottom leg 29A resting upon one leg 35 of U-shaped bracket 37. Bracket 37 is suitably secured to wall 16, for example, of the oven. The other leg 39 of bracket 37 extends above shelf 26 and terminates at its end 41. In the embodiment of FIG. 3 the quarter-wavelength dimension is measured from end 41 to the middle of gap g and also from surface 43 of bracket 37 to surface 45 of Z-shaped bracket 29. The dimension d shown in FIG. 3, similarly to the one shown in FIG. 2 is dimensioned equal to or less than a quarter-wavelength and the zero impedance termination is provided at surface 45.

The embodiment of FIG. 3 can be carried one step furthe by providing a U-shaped bracket 37 having two

legs

35 and 39 that are of different lengths. Leg 39 is longer than leg 35 and is terminated at end 41. Also, in this embodiment, the shelf 26 does not have a downtumed end 31 but terminates at edge 27 thereby defining gap g. The quarter-wavelength measurement is taken from end 41 to the center point of gap g and from surface 43 of bracket 37 to surface 45 of Z-shaped bracket 29. Again, the distance d in FIG. 4 is preferably equal to or less than 2 quarter-wavelength.

FIG. shows still another embodiment of the invention using a Z-shaped bracket 29, a completely horizontal shelf 26 and a U-shaped bracket 37 having

different length legs

35 and 39. In FIG. 5 there is also included a di-electric rod 50 of rectangular cross-section and suitably situated betweenthe bottom leg 29A of bracket 29 and the outer edge 27 of shelf 26. As shown in FIG. 5 the block 50 has a width of Ae/4, where he is the wavelength associated with the material of block 50, and the gap g is defined in the same manner, as shown in FIG. 4. The embodiment of FIG. 5 is structurally similar to that shown in FIG. 4 except that the Z- shaped bracket may be made smaller and leg 35 may be made smaller because of the use of di-electric rod 50.

FIG. 6 shows still another embodiment of the invention wherein the side walls have a U-shaped outer bracket 51 defining a U-shaped channel 52. The wall is provided with an elongated opening 53 defining the gap g and there is a bracket 54 extending inwardly slightly below this gap g. This bracket 54 supports the shelf 26 which has an upturned end 59. End 59 terminates at 55 and the quarter-wavelength dimension is measured from point 55 to the middle of gap g. It is also a quarter-wavelength measurement between the

ends

56 and 57 of U-shaped bracket 51 as depicted in FIG. 6.

FIG. 7 is a fragmentary view showing a preferred structure for the door. In FIG. 7 the door 20 and shelf 26 are shown in a cross-sectional view. Door 20 includes a larger top end 20A and a smaller bottom end 20B with elongated slit 20C formed therebetween. The shelf 26 does not include any upturned end in FIG. 7. The quarter-wavelength dimension is measured from the inner surface of the door to the end of the shelf and also from the end of the shelf to the termination of slit 20C. The door structure of FIG. 7 may be used with any of the embodiments of FIGS. 2-6.

Having described a limited number of embodiments for the apparatus of the present invention, it should now become obvious that numerous other embodiments and modifications of those disclosed can be constructed all of which are contemplated as falling within the spirit and scope of this invention as defined in the appended claims.

What is claimed is:

1. A cooking or heating apparatus comprising;

an oven having side walls and a door,

a shelf disposed in the oven for dividing the oven into first and second sections, said second section including alternate treating means means within said oven for supporting said shelf,

. a source of microwave energy,

and means coupling the microwave energy from the source to the first section of the oven,

a half-wavelength termination means for preventing the leakage of electromagnetic energy into said al temate treating means being provided between at least one of said walls or door and at least a segment of an outer boundary of said shelf.

2. The apparatus of claim 1. wherein said first section is the upper section and said second section is the lower section.

3. The apparatus of claim 2 wherein said shelf is generally horizontallydisposed and has a series of openings therethrough.

4. The apparatus of claim 3 wherein said means for coupling the microwave energy includes a waveguide.

5. The apparatus of claim 1 wherein said alternate heating means includes a gas log heater.

6. The apparatus of claim 5 wherein said shelf supporting means comprises an L-shaped bracket.

7. The apparatus of claim 6 comprising a Z-shaped bracket coupled between said L-shaped bracket and the outer boundary of said shelf.

8. The apparatus of claim 1 wherein the outer boundary of said shelf includes means defining a perimetrical cavity having one dimension of approximately a quarter-wavelength.

9. The apparatus of claim 8 wherein said shelf supporting means includes a bracket secured to the inner walls of the oven and having at least one portion extending inwardly of the oven for supporting said shelf.

10. The apparatus of claim 9 wherein said means defining a perimetrical cavity includes a downtumed end defining in part a gap and a Z-shaped member having one leg secured to a lower surface of said shelf inwardly of said downturned end and having another leg resting on said extending portion of said bracket.

11. The apparatus of claim wherein said bracket has two portions extending inwardly to form a U- shaped bracket.

12. The apparatus of claim 9 wherein said means defining a perimetrical cavity includes a Z-shaped member having one leg secured to a lower surface of said shelf inwardly of the edge of said shelf and having another leg resting on said extending portion of said bracket.

13. The apparatus of claim 12 comprising a dielectric member disposed between the end of said shelf and said Z-shaped member.

14. The apparatus of claim 1 wherein said shelf permits heat to pass from said second section to said first section.

15. The apparatus of claim 1 wherein said door has an inner surface with a slit defined therein of one-half wavelength depth.

16. The apparatus of claim 15 wherein said slit is partially defined by said shelf.

17. A cooking or heating apparatus comprising;

an oven having side walls and a door and an elongated perimetrical opening extending about the oven,

a shelf disposed in the oven for dividing the oven into first and second sections.

means secured to the inner surface of said oven for supporting said shelf,

a source of microwave energy,

means coupling the microwave energy from the source to the first section of the oven,

an alternate heating source disposed in the second section of the oven,

said shelf having at least one opening therethrough for permitting heat to pass from said second section to said first section and having an upturned end of approximately a quarter-wavelength,

and a member defining a channel covering said elongated opening, secured to the outer surface of said oven, and having one dimension of approximately a quarter-wavelength,

said member and upturned end defining a quarterwavelength choke.

18. A cooking or heating apparatus comprising;

an oven,

a shelf disposed in the oven for dividing the oven into first and second areas,

means for supporting said shelf,

means for coupling microwave energy to the first area of the oven,

and an alternate heating means disposed in the second area of the oven, said shelf having at least one passage therethrough permitting passage of heat from said second area to said first area, said supporting means for said shelf and said shelf together defining a termination to microwave energy introduced to said first area.

19. The apparatus of claim 18 wherein said terminations is a half wavelength termination.

20. The apparatus of claim 19 wherein said shelf is constructed of material for shielding against microwave energy.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated anuary 29, 1974 Patent No. 3 a 789 ,1 78

Inventor(s) pa'u] Harh en It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as .shown below:

The insert after Iine 4 in CIaim I shouId read as foIIows:

"said second section incIuding aIternate heating means".

In Iine 9, of CIaim I there shou'ld be recited:

"a1 ternate heating means" rather than I "aiternate treating means".

Signed and vsealed this 11th day of June 1971;.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. C. MARSHALL DANN Attesting Officer I Commissioner of Patents I USCOMM-DC 60876-P69 m u.s. GOVERNMENT PRINTING OFFICE Ian 0-366-834,

FQRM P0-1 050 (10-69) UNITED STAT iilS PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 a 789 a 78 D t d Jan uary 29 'l 974 Inventor(s) Pail-l F aYh en It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as .shown below The insert after 1ine 4 in Claim 1 should read as foHows:

said second section inc1uding aiternate heating means".

In 1ine 9, oflC1aim i, thereshou'ld be r ecit edz "a1ternate heating means" rather than "aite'rnate treating means".

Signed 'andtse alad this 11th day of June 1971].,

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 6037 BQPGQ U.S GOVERNMENT PRINTING OFFICE 1889 0-366-33L

Claims

1. A cooking or heating apparatus comprising; an oven having side walls and a door, a shelf disposed in the oven for dividing the oven into first and second sections, said second section including alternate treating means means within said oven for supporting said shelf, a source of microwave energy, and means coupling the microwave energy from the source to the first section of the oven, a half-wavelength termination means for preventing the leakage of electromagnetic energy into said alternate treating means being provided between at least one of said walls or door and at least a segment of an outer boundary of said shelf.

2. The apparatus of claim 1 wherein said first section is the upper section and said second section is the lower section.

3. The apparatus of claim 2 wherein said shelf is generally horizontally disposed and has a series of openings therethrough.

10. The apparatus of claim 9 wherein said means defining a perimetrical cavity includes a downturned end defining in part a gap and a Z-shaped member having one leg secured to a lower surface of said shelf inwardly of said downturned end and having another leg resting on said extending portion of said bracket.

11. The apparatus of claim 10 wherein said bracket has two portions extending inwardly to form a U-shaped bracket.

13. The apparatus of claim 12 comprising a di-electric member disposed between the end of said shelf and said Z-shaped member.

17. A cooking or heating apparatus comprising; an oven having side walls and a door and an elongated perimetrical opening extending about the oven, a shelf disposed in the oven for dividing the oven into first and second sections. means secured to the inner surface of said oven for supporting said shelf, a source of microwave energy, means coupling the microwave energy from the source to the first section of the oven, an alternate heating source disposed in the second section of the oven, said shelf having at least one opening therethrough for permitting heat to pass from said second section to said first section and having an upturned end of approximately a quarter-wavelength, and a member defining a channel covering said elongated opening, secured to the outer surface of said oven, and having one dimension of approximately a quarter-wavelength, said member and upturned end defining a quarter-wavelength choke.

18. A cooking or heating apparatus comprising; an oven, a shelf disposed in the oven for dividing the oven into first and second areas, means for supporting said shelf, means for coupling microwave energy to the first area of the oven, and an alternate heating means disposed in the second area of the oven, said shelf having at least one passage therethrough permitting passage of heat from said second area to said first area, said supporting means for said shelf and said shelf together defining a termination to microwave energy introduced to said first area.