CA1074873A - Eccentric beam stirrer for microwave oven - Google Patents
Eccentric beam stirrer for microwave ovenInfo
- Publication number
- CA1074873A CA1074873A CA243,890A CA243890A CA1074873A CA 1074873 A CA1074873 A CA 1074873A CA 243890 A CA243890 A CA 243890A CA 1074873 A CA1074873 A CA 1074873A
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- CA
- Canada
- Prior art keywords
- energy
- waveguide
- coupling
- opening
- shaft
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Constitution Of High-Frequency Heating (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A microwave oven having means defining an oven cavity, a magnetron microwave power source, a waveguide for coupling energy from the magnetron to the oven cavity and preferably a mode match-ing transformer for establishing primarily only the dominant mode in the oven cavity. A beam stirrer is disposed adjacent the waveguide feed into the cavity. and is in the form of a resonant structure for coupling the energy to the cavity. The resonant structure is rotated in an eccentric manner to spread the energy beam to thereby provide a more uniform heating pattern.
In one specific form the resonant structure is a cylinder of relatively short length and dimensioned to provide good matching with the magnetron source along with beam motion.
A microwave oven having means defining an oven cavity, a magnetron microwave power source, a waveguide for coupling energy from the magnetron to the oven cavity and preferably a mode match-ing transformer for establishing primarily only the dominant mode in the oven cavity. A beam stirrer is disposed adjacent the waveguide feed into the cavity. and is in the form of a resonant structure for coupling the energy to the cavity. The resonant structure is rotated in an eccentric manner to spread the energy beam to thereby provide a more uniform heating pattern.
In one specific form the resonant structure is a cylinder of relatively short length and dimensioned to provide good matching with the magnetron source along with beam motion.
Description
7~373 Back~round of the Inventlon The present invention relates in general to microwave ovens and more particularly to a beam stirrer used in the microwave oven for providing a more uniform heatiny pattern.
In order to provide uniform and rapid heating of materials and foods, high frequency energy, generally in the microwave region, has been utilized. Materials or foods to be heated are generally placed in an enclosure which i,5 sealed to prevent the escape of high fre~uency energy. The energy generated, usually fromamagnetron, is inserted either directly into the enclosure or indirectly through the use of a waveguide or other suitable coupling device.
Mode stirrers are well known in the art and are shown, for example, in U.S. Patent 3,106,629. October 8, 1963~ Although the~e mode stirrers do provide somewhat of an improvement in the uniformity of the heating pattern, there are certain disadvantages associated with these prior art structures. For example, there ; is generally a matching problem between the cavity and the magne-tron which is occasioned by the abrupt discontinuity that occurs each time the blades of the stirrer rotate across the mouth of the waveguide opening.
Accordingly, one object of the present invenkion is to provide an improved structure for location within a microwave ~ oven for providing a uniform heating pattern.
'~ Another object of the present invention is to provide a beam stirrer ~or use in a microwave oven and that is in the form of a resonant structure capable of providing good matching with the magnetron.
A further object of the present invention is to provide a beam stirrer in accordance with the preceding object and that is movable in an eccentric manner to provide beam motion over an , ~ - 2 -.
area of the ovenO
Summary of the Invention A construction in accordance with the present inven-tion includes a microwave oven having a source of microwave energy, a cooking cavity and waveguide means coupling from the source to an opening into the cooking cav:ity, a beam stirrer disposed adjacent the opening and compris.ing a resonant struc-;:
-~ ture that represents a relatively low impedance to the energy, is disposed adjacent the opening into the cooking cavity and covers a first area intermediate the opening and cooking cavity and means for eccentrically rotating the structure to spread the energy beam without substantially disrupting the impedance :
to energy and so that the structure when rotating covers a second ~ .
area larger than said first area and also intermediate the open- :
ing and cooking cavity. :
In a more specific embodiment, the microwave oven has :
. means defining an oven cooking area, a source of microwave .
energy, and a waveguide means coupling the energy from the ...
source to the cooking area, the improvement comprising an energy .:
coupling structure disposed in the oven cooking area in a posi-: tion adjacent one end of the waveguide means to receive the ~ : .
coupled energy and including a substantially continuous ring member defining a coupling opening extending in -the direction from the waveguide means to the oven cooking area, means eccen- : -trically supporting the structure from a wall adjacent the one end of the waveguide means and means for rotating the supporting means to in turn rotate the structure to thereby move the energy beam in many directions with the opening in the coupling struc- .
ture being maintained extending in substantially the same direction as the structure is rotated so that the energy is coupled relatively uniformly as the structure rotates.
~ 3 ~ . : .
! r : . ' .... : .` ': ,, ' :, " ,. ' ,.' , ' .. , ' . ' '' : ' ' .
8~3 Brief Descriptlon _f the Drawln~s Numerous other objects, features and advantages of the invention will now become apparent upon a reading of the follow-ing detailed description taken in conjunction with the accom-panying drawings, in which:
FIG. 1 is a cross-sectional view of a microwave oven using the beam stirrer of the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 of ~7~3 FIG. 1, FIG. 3 is a perspective view of the beam stirrer shown in FIGS. 1 and 2, and FIG. 4 shows an alternate embodiment for the beam stirrer.
Detailed Description FIG. 1 shows a microwave oven 10 the structure of which may be similar to that shown in U.S. Patent 3,764,770, October 9, 1973.
The oven typically includes a rack 12 for holding a plate 14 which may support a foodstuff 160 Energy is coupled to the oven cavity by way of waveguide 18 from magnetron 20. In accordance with the teachings of my U.S. Patent 3,764,770. there may be provided a quarter wavelength step 22 between the output end 19 of the -~aveguide and the oven cavity 24. This quarter wavelength step is for establishing primarily only the dominant mode within the o~en cavity. Although this structure is shown in the illustrative embodiment it should be understood that the mode stirrer of the present invention may also be used with oven structures wherein the cavity has established therein multiple modes.
Referring now to FIGS. 1-3, the beam stirrer comprises a support rod 26, a cylindrical coupling structure 30 and a drive mokor 32. The support shaft 26 may be suitabl~ supported at one or both ends and includes a pulley 34 attached to the top end.
The pulley 34 is driven by way of a small belt 36 from the motor 32. The motor is suitably supported from a top wall 37 of the waveguide 18.
The coupling structure 30 is of cylindrical shape and is attached to the shaft 26 by means of an L-shaped tab 40 which is fixed at one end to the inner surface of structure 30 and at the other end to the bottom of shaft 26.
FIG. 2 cleaxly shows the eccentric arrangement of the present arrangement wherein the cylindrical coupling structure sweeps to . .. . .
.~ - 4 -,. . . .,, ...... ~ ., . , , .................. - . .
... , ~ : . - .. . . :
10~4~73 lM215/737 1 cover an area lar~er than the area of the cylindrical structure itself.
~ IG. 2 sho~s the structure 3~ also in dotted in two other alternate positions, Wikh this arrangement the energy from the ; wave~uide is coupled to the cavit~ and the eccentric movement of the coupling structure 30 tends to spread the beam over the cooking area of the oven.
It has also ~een found that .it is desirahle to provide a slight tilt to the coupling structure 30 relative to its support 10. shaft 26, FIG. 3 sho~s this relatively small angle a which may be on the order of 5~10~.. This angle a can be provided simply by bending the tab 40 slightl~.
The:coupling structure 3a is basically a ~uarter wa~elength structure but the dimensions are pre~erably sli.ghtly altered from this quarter waveIength structure ~height h) to provide optimum matching between the magnetron and the oven cavity~
Previously, the matching required the use of posts or other elements at the output end of the waveguide.
In the disclosea embodiment the height of the coupling 2a structuxe may be 0.-7" and the inside diameter may be two inches ~hen using a waveguide of dimensions 1.50" by 3.75".
It .is known that the ma~netron source should not be operated in the sink region o~ the Rieke di~agram. See M.I.T~ Radiation Laboratory Seriesj Radar System Engineering, pages 336-340. If the heiyht of the structure is too high the tube will be operat.ing undesixably.close to this sink area with too large a VSWR. .~;
AlternativeIy, if the hei~ht.is made too small the match will not be proper. The height of 0..7" provided a proper match wherein the coupling structu~e represents a relativeIy low impedance to the magnetron source.
By the proper selection of both the dimater and height of the resonant structure a reIatively low V5WR can be provided.
::
5. .
.. . . . . .
~7~L87~
1~215/737 1 The coupling structure of this invention can also be used with an existing structure ~hereln the matchin~ has also alxeady been provided. In that case, the structure may be more nearly a quarter wavelength structure.
FIG. 4 shows a perspective view of another embodiment of a stirrer. This embodiment employs a solid disc 42 connected to shaft 26 by means of a strip 44. This arrangement also provides a spreading of the beam coupled from the waveguide structure. In still another embodiment the disc 42 ma~ be in the form of an open ring.
Having described a limited number of embodiments of the present invention it should now be appar~nt that there are numerous modifications that can be made in this invention without departing ~rom the scope thereof, For example, in the drawings a cylindrical coupling structure has been shown. ~owever, this structure could also be~square, eliptical, rectangular or could take on various other shapes. Also, the structure has been shown as being a continuous structure but could also be a segmented structure.
Also, regarding the embodiment shown in FIG~ 4 a dielectric 2Q material could be coupled to the end of the shaft and function as a coupling structure.
`. ' ~ "
., ,'," .
.' .
:
'' 6.
'
In order to provide uniform and rapid heating of materials and foods, high frequency energy, generally in the microwave region, has been utilized. Materials or foods to be heated are generally placed in an enclosure which i,5 sealed to prevent the escape of high fre~uency energy. The energy generated, usually fromamagnetron, is inserted either directly into the enclosure or indirectly through the use of a waveguide or other suitable coupling device.
Mode stirrers are well known in the art and are shown, for example, in U.S. Patent 3,106,629. October 8, 1963~ Although the~e mode stirrers do provide somewhat of an improvement in the uniformity of the heating pattern, there are certain disadvantages associated with these prior art structures. For example, there ; is generally a matching problem between the cavity and the magne-tron which is occasioned by the abrupt discontinuity that occurs each time the blades of the stirrer rotate across the mouth of the waveguide opening.
Accordingly, one object of the present invenkion is to provide an improved structure for location within a microwave ~ oven for providing a uniform heating pattern.
'~ Another object of the present invention is to provide a beam stirrer ~or use in a microwave oven and that is in the form of a resonant structure capable of providing good matching with the magnetron.
A further object of the present invention is to provide a beam stirrer in accordance with the preceding object and that is movable in an eccentric manner to provide beam motion over an , ~ - 2 -.
area of the ovenO
Summary of the Invention A construction in accordance with the present inven-tion includes a microwave oven having a source of microwave energy, a cooking cavity and waveguide means coupling from the source to an opening into the cooking cav:ity, a beam stirrer disposed adjacent the opening and compris.ing a resonant struc-;:
-~ ture that represents a relatively low impedance to the energy, is disposed adjacent the opening into the cooking cavity and covers a first area intermediate the opening and cooking cavity and means for eccentrically rotating the structure to spread the energy beam without substantially disrupting the impedance :
to energy and so that the structure when rotating covers a second ~ .
area larger than said first area and also intermediate the open- :
ing and cooking cavity. :
In a more specific embodiment, the microwave oven has :
. means defining an oven cooking area, a source of microwave .
energy, and a waveguide means coupling the energy from the ...
source to the cooking area, the improvement comprising an energy .:
coupling structure disposed in the oven cooking area in a posi-: tion adjacent one end of the waveguide means to receive the ~ : .
coupled energy and including a substantially continuous ring member defining a coupling opening extending in -the direction from the waveguide means to the oven cooking area, means eccen- : -trically supporting the structure from a wall adjacent the one end of the waveguide means and means for rotating the supporting means to in turn rotate the structure to thereby move the energy beam in many directions with the opening in the coupling struc- .
ture being maintained extending in substantially the same direction as the structure is rotated so that the energy is coupled relatively uniformly as the structure rotates.
~ 3 ~ . : .
! r : . ' .... : .` ': ,, ' :, " ,. ' ,.' , ' .. , ' . ' '' : ' ' .
8~3 Brief Descriptlon _f the Drawln~s Numerous other objects, features and advantages of the invention will now become apparent upon a reading of the follow-ing detailed description taken in conjunction with the accom-panying drawings, in which:
FIG. 1 is a cross-sectional view of a microwave oven using the beam stirrer of the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 of ~7~3 FIG. 1, FIG. 3 is a perspective view of the beam stirrer shown in FIGS. 1 and 2, and FIG. 4 shows an alternate embodiment for the beam stirrer.
Detailed Description FIG. 1 shows a microwave oven 10 the structure of which may be similar to that shown in U.S. Patent 3,764,770, October 9, 1973.
The oven typically includes a rack 12 for holding a plate 14 which may support a foodstuff 160 Energy is coupled to the oven cavity by way of waveguide 18 from magnetron 20. In accordance with the teachings of my U.S. Patent 3,764,770. there may be provided a quarter wavelength step 22 between the output end 19 of the -~aveguide and the oven cavity 24. This quarter wavelength step is for establishing primarily only the dominant mode within the o~en cavity. Although this structure is shown in the illustrative embodiment it should be understood that the mode stirrer of the present invention may also be used with oven structures wherein the cavity has established therein multiple modes.
Referring now to FIGS. 1-3, the beam stirrer comprises a support rod 26, a cylindrical coupling structure 30 and a drive mokor 32. The support shaft 26 may be suitabl~ supported at one or both ends and includes a pulley 34 attached to the top end.
The pulley 34 is driven by way of a small belt 36 from the motor 32. The motor is suitably supported from a top wall 37 of the waveguide 18.
The coupling structure 30 is of cylindrical shape and is attached to the shaft 26 by means of an L-shaped tab 40 which is fixed at one end to the inner surface of structure 30 and at the other end to the bottom of shaft 26.
FIG. 2 cleaxly shows the eccentric arrangement of the present arrangement wherein the cylindrical coupling structure sweeps to . .. . .
.~ - 4 -,. . . .,, ...... ~ ., . , , .................. - . .
... , ~ : . - .. . . :
10~4~73 lM215/737 1 cover an area lar~er than the area of the cylindrical structure itself.
~ IG. 2 sho~s the structure 3~ also in dotted in two other alternate positions, Wikh this arrangement the energy from the ; wave~uide is coupled to the cavit~ and the eccentric movement of the coupling structure 30 tends to spread the beam over the cooking area of the oven.
It has also ~een found that .it is desirahle to provide a slight tilt to the coupling structure 30 relative to its support 10. shaft 26, FIG. 3 sho~s this relatively small angle a which may be on the order of 5~10~.. This angle a can be provided simply by bending the tab 40 slightl~.
The:coupling structure 3a is basically a ~uarter wa~elength structure but the dimensions are pre~erably sli.ghtly altered from this quarter waveIength structure ~height h) to provide optimum matching between the magnetron and the oven cavity~
Previously, the matching required the use of posts or other elements at the output end of the waveguide.
In the disclosea embodiment the height of the coupling 2a structuxe may be 0.-7" and the inside diameter may be two inches ~hen using a waveguide of dimensions 1.50" by 3.75".
It .is known that the ma~netron source should not be operated in the sink region o~ the Rieke di~agram. See M.I.T~ Radiation Laboratory Seriesj Radar System Engineering, pages 336-340. If the heiyht of the structure is too high the tube will be operat.ing undesixably.close to this sink area with too large a VSWR. .~;
AlternativeIy, if the hei~ht.is made too small the match will not be proper. The height of 0..7" provided a proper match wherein the coupling structu~e represents a relativeIy low impedance to the magnetron source.
By the proper selection of both the dimater and height of the resonant structure a reIatively low V5WR can be provided.
::
5. .
.. . . . . .
~7~L87~
1~215/737 1 The coupling structure of this invention can also be used with an existing structure ~hereln the matchin~ has also alxeady been provided. In that case, the structure may be more nearly a quarter wavelength structure.
FIG. 4 shows a perspective view of another embodiment of a stirrer. This embodiment employs a solid disc 42 connected to shaft 26 by means of a strip 44. This arrangement also provides a spreading of the beam coupled from the waveguide structure. In still another embodiment the disc 42 ma~ be in the form of an open ring.
Having described a limited number of embodiments of the present invention it should now be appar~nt that there are numerous modifications that can be made in this invention without departing ~rom the scope thereof, For example, in the drawings a cylindrical coupling structure has been shown. ~owever, this structure could also be~square, eliptical, rectangular or could take on various other shapes. Also, the structure has been shown as being a continuous structure but could also be a segmented structure.
Also, regarding the embodiment shown in FIG~ 4 a dielectric 2Q material could be coupled to the end of the shaft and function as a coupling structure.
`. ' ~ "
., ,'," .
.' .
:
'' 6.
'
Claims (15)
1. In a microwave oven having means defining an oven cooking area, a source of microwave energy, and a waveguide means coupling the energy from the source to the cooking area, the improvement comprising:
an energy coupling structure disposed in the oven cooking area in a position adjacent one end of the waveguide means to receive the coupled energy and including a substantially continuous ring member defining a coupling opening extending in the direction from the waveguide means to the oven cooking area, means eccentrically supporting the structure from a wall adja-cent the one end of the waveguide means and means for rotating the supporting means to in turn rotate the structure to thereby move the energy beam in many directions with the opening in the coupling structure being maintained extending in substantially the same direction as the structure is rotated so that the energy is coupled relatively uniformly as the structure rotates.
an energy coupling structure disposed in the oven cooking area in a position adjacent one end of the waveguide means to receive the coupled energy and including a substantially continuous ring member defining a coupling opening extending in the direction from the waveguide means to the oven cooking area, means eccentrically supporting the structure from a wall adja-cent the one end of the waveguide means and means for rotating the supporting means to in turn rotate the structure to thereby move the energy beam in many directions with the opening in the coupling structure being maintained extending in substantially the same direction as the structure is rotated so that the energy is coupled relatively uniformly as the structure rotates.
2. The beam stirrer of claim 1, wherein said energy coupling structure has at least one wall extending generally in the direction of the beam.
3. The beam stirrer of claim 1, wherein said energy coupling structure includes a cylindrical body of quarter wave-length height.
4. The beam stirrer of claim 3, wherein said means for eccentrically supporting includes a shaft and tab means for securing the shaft close to one section of the body.
5. The beam stirrer of claim 4, wherein said means for rotating includes motor means coupled to said shaft.
6. The beam stirrer of claim 5, wherein a small angle is provided between the center line of the shaft and the center line of the body.
7. In a microwave oven having means defining an oven cavity, a source of microwave energy, and means coupling the energy from the source to the cavity, the improvement comprising:
a beam stirrer disposed in the oven cavity in a posi-tion to receive the coupled energy and including a cylindrical body of approximately quarter wave length height, means eccen-trically supporting the structure including a shaft. and tab means for securing the shaft close to one section of the body and motor means coupled to the shaft for rotating the cylindrical body to thereby deflect the beam in many directions with the energy being coupled relatively uniformly as the structure rotates, wherein a small angle is provided between the center line of the shaft and the center line of the body.
a beam stirrer disposed in the oven cavity in a posi-tion to receive the coupled energy and including a cylindrical body of approximately quarter wave length height, means eccen-trically supporting the structure including a shaft. and tab means for securing the shaft close to one section of the body and motor means coupled to the shaft for rotating the cylindrical body to thereby deflect the beam in many directions with the energy being coupled relatively uniformly as the structure rotates, wherein a small angle is provided between the center line of the shaft and the center line of the body.
8. The beam stirrer of claim 6, wherein said tab means is slightly bent to provide the slight angle.
9. The beam stirrer of claim 7, wherein the slight angle is on the order of 5-10°.
10. In a microwave oven having a source of microwave energy, a cooking cavity and waveguide means coupling from the source to an opening into the cooking cavity, a beam stirrer disposed adjacent the opening and comprising a resonant structure that represents a relatively low impedance to the energy, is disposed adjacent the opening into the cooking cavity and covers a first area intermediate the opening and cooking cavity and means for eccentrically rotating the structure to spread the energy beam without substantially disrupting the impedance to energy and so that the structure when rotating covers a second area larger than said first area and also intermediate the opening and cooking cavity.
11. The beam stirrer of claim 10, wherein said energy coupling structure includes a solid plate.
12. A microwave oven comprising:
a source of microwave energy, a waveguide of predetermined cross-section positioned with one end receiving energy from said source for transmission through said waveguide, the frequency of operation of said source and the dimension of said waveguide being selected to excite the dominant mode in said waveguide, means defining an enclosure including means for pro-viding access to the enclosure and means defining an opening into the enclosure, matching means coupling from the other end of the waveguide to the opening in the enclosure for establishing primarily only the dominant mode in the enclosure, and energy coupling and directing means disposed at the opening to the enclosure and including a ring structure dimensioned to act as a low impedance to the energy and covering a first area and means for rotating the ring structure to cover a second area larger than the first area.
a source of microwave energy, a waveguide of predetermined cross-section positioned with one end receiving energy from said source for transmission through said waveguide, the frequency of operation of said source and the dimension of said waveguide being selected to excite the dominant mode in said waveguide, means defining an enclosure including means for pro-viding access to the enclosure and means defining an opening into the enclosure, matching means coupling from the other end of the waveguide to the opening in the enclosure for establishing primarily only the dominant mode in the enclosure, and energy coupling and directing means disposed at the opening to the enclosure and including a ring structure dimensioned to act as a low impedance to the energy and covering a first area and means for rotating the ring structure to cover a second area larger than the first area.
13. In a microwave oven as set forth in claim 12, wherein the resonant structure includes a cylindrical shaped member and the means for eccentrically rotating includes a shaft, means for connecting one end of the shaft to the member and means for driving the other end of the shaft.
14. In a microwave oven as set forth in claim 13, wherein the opening is in the top of the oven into the cooking cavity and the shaft is positioned vertically.
15. In a microwave oven as set forth in claim 14, wherein the member defines an open coupling hole for passing energy from the opening into the cavity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA243,890A CA1074873A (en) | 1976-01-15 | 1976-01-15 | Eccentric beam stirrer for microwave oven |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA243,890A CA1074873A (en) | 1976-01-15 | 1976-01-15 | Eccentric beam stirrer for microwave oven |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1074873A true CA1074873A (en) | 1980-04-01 |
Family
ID=4105016
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA243,890A Expired CA1074873A (en) | 1976-01-15 | 1976-01-15 | Eccentric beam stirrer for microwave oven |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1074873A (en) |
-
1976
- 1976-01-15 CA CA243,890A patent/CA1074873A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |