Electromagnetic wave energy seal arrangement

Abstract

In an apparatus which produces high frequency electromagnetic waves, a choke portion is provided in a leakage transmission path, which choke portion has a groove wall corresponding to a grounded conductor, a number of strip conductors arranged with a line width a and a pitch p, and a groove bottom, so as to minimize leakage propagation in the longitudinal direction of the groove. Further, this choke portion is designed so that the characteristic impedance of its portion is changed in a region shorter than λ/4 of the frequency to be used. As a result, the depth and .[.width.]. .Iadd.clearance .Iaddend.of the groove can .[.also.]. .Iadd.both .Iaddend.be made less than λ/4.

What is claimed is: .[. 
     
       1.  An electromagnetic wave energy seal arrangement comprising: at least a pair of members separably fitted together and defining at least one electromagnetic active space for confining electromagnetic waves from a high frequency oscillation source, said pair of members having opposed portions defining a leakage path for electromagnetic waves from said space to the exterior around said space, at least one of said members having at least one groove in the portion defining said leakage path with the depth thereof for attenuating the electromagnetic waves of basic frequency extending perpendicular to the direction of said leakage path, and the groove extending along said one member transverse to the direction of the leakage path; and   a plurality of conductor plates extending along the groove on at least one surface of the portion of said one member defining said leakage path and groove, said conductor plates extending from the bottom of said one groove remote from the other member toward said other member, the width of the groove being less than 1/4 the effective wavelength of the electromagnetic waves of basic frequency, at least one parameter from among the width of said conductor plates, the clearance between said conductor plates and the surface of the groove opposed to said conductor plates, and the dielectric constant of any dielectric in said groove, is different at the outer portion of the groove adjacent the leakage path than at the inner portion, and wherein the depth of said groove is less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path and the sum of the depth of said groove and the width thereof is also less than 1/4 the effective wavelength of the electromagnetic waves in said leakage path..].   
     
     
       2. An electromagnetic wave energy seal arrangement as claimed in claim .[.1.]. .Iadd.10 .Iaddend.wherein the conductor plate width, the clearance, and the specific dielectric constant are such that the relationship b/a√ε r , wherein a is the conductor plate width, b is the clearance, and ε r  is the dielectric constant, has at least two values in the different portions of the groove. .[.3. An electromagnetic wave energy seal arrangement as claimed in claim 1 in which at least one parameter from among the width of said conductor plates, the clearance between said conductor plates and the surface of the groove opposed to said conductor plates, and the dielectric constant of any dielectric in said groove, is different at the outer portion of the groove adjacent the leakage path than at the inner portion, and the depth of the groove is less than 1/4 of the effective wavelength of the 
     
     
        electromagnetic waves in said leakage path..]. 4. An electromagnetic wave energy seal arrangement as claimed in claim .[.3.]. .Iadd.10 .Iaddend.in 
     
     
        which there are a plurality of said grooves with conductor plates. 5. An electromagnetic wave energy seal arrangement as claimed in claim 4 in which there are a plurality of electromagnetic active spaces each confining electromagnetic waves of different frequencies, and the resonance frequencies of the respective grooves and conductor plates are substantially equal to the frequencies of the electromagnetic waves in the 
     
     
        respective spaces. 6. An electromagnetic wave energy seal arrangement as claimed in claim 4 in which there are a plurality of electromagnetic active spaces each confining electromagnetic waves of different frequencies, and the resonance frequencies of the respective grooves and conductor plates .[.corresponding.]. .Iadd.correspond .Iaddend.to the frequencies of the electromagnetic waves in the respective spaces. .[.7. A heating apparatus comprising: an enclosure having at least one wall member with an access opening therein;   means for energizing said enclosure with microwaves having at least one predetermined frequency;   a door member on said enclosure for closing said access opening and when in the closed position defining with the edge of said wall member around said access opening a leakage path for electromagnetic waves from said enclosure to the exterior around said enclosure, at least one of said members having at least one groove in the portion defining said leakage path with the depth thereof for attenuating the electromagnetic waves of basic frequency extending perpendicular to the direction of said leakage path, and the groove extending along said one member transverse to the direction of the leakage path; and   a plurality of conductor plates extending along the groove on at least one surface of the portion of said one member defining said leakage path and groove, said conductor plates extending from the bottom of said one groove remote from the other member toward said other member, the width of the groove being less than 1/4 the effective wavelength of the electromagnetic waves of basic frequency, at least one parameter from among the width of said conductor plates, the clearance between said conductor plates and the surface of the groove opposed to said conductor plates and the dielectric constant of any dielectric in said groove, is different at the outer portion of the groove adjacent the leakage path than at the inner portion, and wherein the depth of said groove is less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path and the sum of the depth of said groove and the width thereof is also less than 1/4 the effective wavelength of the electromagnetic waves in said leakage   
     
     
        path..]. 8. An electromagnetic wave and energy seal arrangement as claimed in claim .[.7.]. .Iadd.11 .Iaddend.further comprising a dielectric cover covering said groove .[.where it opens into.]. .Iadd.adjacent .Iaddend.said leakage path. .[.9. An electromagnetic wave energy seal arrangement comprising: a heating chamber having an access opening thereto and having a flat plate around said access opening;   a high frequency oscillation means supplying electromagnetic waves to said heating chamber;   a door mounted on said chamber for opening and closing said access opening, said door when in the closed position defining a leakage path between it and said flat plate;   said door having a plurality of grooves therein opening into said leakage path and extending along said door opposite said flat plate with the depth extending perpendicular to the direction of the leakage path, the width of each groove being less than 1/4 the effective wavelength of the electromagnetic waves of basic frequency; and   a plurality of dielectric parts having a high dielectric constant mounted along said grooves for serving as waveguide bodies, said dielectric parts having a shape which changes in the direction of the depth of said grooves the depth of each groove being less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path and the sum of the depth of each groove and the width thereof is also less than 1/4 the effective wavelength of the electromagnetic waves in said leakage path..].   
     
     
        .Iadd.     An electromagnetic wave energy seal arrangement comprising: at least a pair of members separably fitted together and defining at least one electromagnetic active space for confining electromagnetic waves from a high frequency oscillation source, said pair of members having opposed portions defining a leakage path for electromagnetic waves from said space to the exterior around said space, said leakage path extending in a first direction, at least one of said members having first and second spaced portions extending in a second direction perpendicular to said leakage path and a third portion between said first and second portions extending in said first direction, said first, second and third portions of said at least one member defining a groove extending in a third direction transverse to said first and second directions for attenuating the electromagnetic waves of basic frequency, said groove having a depth dimension in said second direction between said leakage path and the third portion of said at least one member; and   a plurality of spaced conductor plates located within said groove and extending in said third direction, the dimension of each of said plates in said third direction being defined as the width thereof, each conductor plate having first and second parts spaced from each other in said first direction, extending in said second direction, and spaced by a clearance dimension from the first and second portions of said at least one member, at least one parameter from among said width dimension, said clearance dimension and the dielectric constant of any dielectric in said groove being different at the outer portion of the groove adjacent the leakage path than at the inner portion of the groove adjacent the third portion of said at least one member, and wherein the depth and clearance of said groove are both less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path. .Iaddend. .Iadd.11. A heating apparatus comprising:   an enclosure having at least one wall member with an access opening therein;   means for energizing said enclosure with microwaves having at least one predetermined frequency;   a door member on said enclosure for closing said access opening and, when in the closed position, defining with an edge of said wall member around said access opening a leakage path for electromagnetic waves from said enclosure to the exterior around said enclosure, said leakage path extending in a first direction, at least one of said wall and door members having first and second spaced portions extending in a second direction perpendicular to said leakage path and a third portion between said first and second portions extending in said first direction, said first, second and third portions of said at least one member defining a groove extending in a third direction transverse to said first and second directions for attenuating the electromagnetic waves of basic frequency, said groove having a depth dimension in said second direction between said leakage path and the third portion of said at least one member; and   a plurality of spaced conductor plates located within said groove and extending in said third direction, the dimension of each of said plates in said third direction being defined as the width thereof, each conductor plate having first and second parts spaced from each other in said first direction, extending in said second direction, and spaced by a clearance dimension from the first and second portions of said at least one member, at least one parameter from among said width dimension, said clearance dimension and the dielectric constant of any dielectric in said groove being different at the outer portion of the groove adjacent the leakage path than at the inner portion of the groove adjacent the third portion of said at least one member, and wherein the depth and clearance of said groove are both less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path. .Iaddend. .Iadd.12. An electromagnetic wave energy seal arrangement comprising:   a heating chamber having an access opening thereto and having a flat plate around said access opening;   a high frequency oscillation means supplying electromagnetic waves to said heating chamber;   a door mounted on said chamber for opening and closing said access opening, said door when in the closed position defining a leakage path extending in a first direction between it and said flat plate, said door having first and second spaced portions extending in a second direction perpendicular to said leakage path and a third portion between said first and second portions extending in said first direction, said first, second and third portions of said door defining a plurality of grooves extending in a third direction transverse to said first and second direction, said grooves having depth dimensions in said second direction between said leakage path and the third portion of said at least one member; and   a plurality of spaced conductor plates located within said grooves and extending in said third direction, the dimension of each of said plates in said third direction being defined as the width thereof, each conductor plate having first and second parts spaced from each other in said first direction, extending in said second direction, and spaced by a clearance dimension from the first and second portions of said at least one member; and     a plurality of dielectric parts having a high dielectric constant mounted along said grooves for serving as waveguide bodies, said dielectric parts having shapes which change in the direction of the depth of said grooves, and wherein the depth and clearance of said groove are both less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage   
     
     
        path. .Iaddend. .Iadd.13.  A heating apparatus comprising: an enclosure having at least one wall member with an access opening therein;   means for energizing said enclosure with microwaves having at least one predetermined frequency;   a door member on said enclosure for closing said access opening and, when in the closed position, defining with an edge of said wall member around said access opening a leakage path for electromagnetic waves from said enclosure to the exterior around said enclosure, said leakage path extending in a first direction, said door member extending in a second direction perpendicular to said leakage path and in a third direction transverse to said first and second directions to define a groove therein having a depth in said second direction; and   a plurality of spaced conductor plates extending in said third direction, each conductor plate having first and second parts spaced from each other in said first direction, extending in said second direction, and spaced in said first direction by first and second different respective clearance dimensions from a portion of said door member extending in said second direction, and wherein the depth of said groove and the clearance dimensions are both less than 1/4 of the effective wavelength of the electromagnetic waves in said leakage path, said energy seal attenuating the electromagnetic waves being propagated in said leakage path. .Iaddend.   
     
     
        .Iadd.14.  A heating apparatus as claimed in claim 13 wherein the first part of each conductor plate is conductively connected to the portion of said door member, the second part of said conductor plate is interposed between said first part thereof and the portion of said door member, and the length of the second part of said conductor plate in said depth direction is less than that of the first part of said conductor plate. .Iaddend.