Abstract:
An interrupting circuit is configured to monitor for and detect a fault in a device for generating a field of electromagnetic radiation (e-field) from a radio frequency (RF) generator configured to convert low voltage direct current (DC) into the e-field for application to an article in the e-field. If a fault is detected, the interrupting circuit interrupts low voltage DC between an energy reserve and the RF generator within a predetermined time less than the time to dissipate energy stored in the energy reserve.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to a microwave oven having multiple cooking cavities, and more specifically to the door of a microwave oven having multiple cooking cavities. 
       BACKGROUND 
       [0002]    Traditional microwave ovens usually comprise a single cooking cavity in which a foodstuff to be cooked is placed. The number of foodstuffs that can be prepared at the same time in such traditional microwave ovens is therefore limited and inadequate for many users. For example, preparing different foodstuffs that require different cooking parameters in a single cavity microwave oven may require the time to cook them sequentially rather than concurrently because of the different cooking parameters. Out of this need, microwave ovens with multiple cooking cavities were developed. 
         [0003]    For example U.S. Publication No. 20130153570 discloses a microwave oven with two sub-cavities to simultaneously cook multiple foodstuffs with improved cooking evenness and cooking time. Each sub-cavity is provided with a microwave generator and feeding port to independently cook foodstuffs located therein. A removable dividing shelf between the sub-cavities attenuates microwave transmission between the sub-cavities. A sealing choke where the shelf meets the walls of the cavity aids the attenuation. However, transmission may still occur between the shelf and the door. 
       SUMMARY 
       [0004]    In one aspect, the invention relates to a microwave oven that has a cooking cavity, a dividing shelf for dividing the cooking cavity into at least two sub-cavities and a door movable between an open and closed position for selectively providing and preventing access to the sub-cavities respectively. The door may be provided with a choke frame configured to communicate with the dividing shelf in the closed position so as to attenuate microwave transmission between sub-cavities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    In the drawings: 
           [0006]      FIG. 1  is a perspective view of a microwave oven according to an embodiment of the invention; 
           [0007]      FIG. 2  is a perspective view of a microwave oven door aesthetic assembly according to an embodiment of the invention; 
           [0008]      FIG. 3  is a perspective view of a microwave oven door structural assembly according to an embodiment of the invention; 
           [0009]      FIG. 4  is an exploded view of partially assembled microwave oven door according to an embodiment of the invention; 
           [0010]      FIG. 5  is a cross sectional view of a microwave oven according to an embodiment of the invention; and 
           [0011]      FIG. 6  is a cross sectional view of section VI of  FIG. 5  showing the metal reed and dividing shelf interface according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Turning now to the drawings and to  FIG. 1  in particular, there is shown a perspective view of a microwave oven  100  according to an embodiment of the invention. The microwave oven  100  includes a cabinet  120  defining a cooking cavity  112  and a dividing shelf  114  which divides the cooking cavity  112  into a first sub-cavity  116  and a second sub-cavity  118 . The microwave oven  100  further includes a door  200 . The door  200  is provided with a choke frame  220  which encompasses a first pane of glass  224  and a second pane of glass  226  which correspond, respectively, to the first and second sub-cavities  116 ,  118 . The first and second panes of glass  224 ,  226  are constructed in such a way, that they are optically transparent but not transparent to microwaves. Furthermore, the first and second panes of glass  224 ,  226  are separated by the choke frame  220 . A hinge  228  mounted to one side of the door  200  and to the cabinet  120  pivotally connects the door  200  to the cabinet  120 . 
         [0013]    The hinge  228  allows the door  200  to pivotally move between a first open position, best seen in  FIG. 1 , for simultaneous access to the first and second sub-cavities  116 ,  118  and a second closed position, best seen in  FIG. 5 , for preventing simultaneous access to the first and second sub-cavities  116 ,  118 . When the door  200  is in the second position, the choke frame  220 , and particularly the area of the choke frame  220  between the first and second panes of glass  224 ,  226  is in communication with the dividing shelf  114  in such a manner so as to attenuate microwave transmission between the first and second sub-cavities  116 ,  118 . Furthermore, the choke frame  220  is also is in communication with a cooking cavity aperture perimeter  122  in such a manner so as to attenuate microwave transmission between the cooking cavity  112  and the door  200 . 
         [0014]    According to one embodiment, the dividing shelf  114  may be arranged at half of the height of the cooking cavity  112 , thereby enabling the division of the cooking cavity  112  into the two sub-cavities  116 ,  118  essentially identical in size (or volume). However, according to another embodiment, the dividing shelf  114  may be arranged such that the cooking cavity  112  may be divided in different manners (e.g. at one third or two third of the height or, in other cases, at one fourth or three fourths of the height), thereby resulting in sub-cavities  116 ,  118  of different sizes/volumes. In yet another embodiment, the microwave oven  100  may not be equipped with a dividing shelf  114  such that the cooking cavity  112  is undivided and that the choke frame  120  only prevents leakage of microwaves between the cooking cavity  112  and the door  200 . 
         [0015]      FIG. 2  shows a perspective view of a microwave oven door aesthetic assembly  300  according to an embodiment of the invention. The aesthetic assembly  300  includes an external panel  302 . The external panel  302  may be made from any material suitable for the application as described herein including but not limited to: glass, plastic, metal, ceramic or a composite. The external panel  302  may have first and second apertures  312 ,  314  that correspond, respectively, to the first and second panes of glass  224 ,  226  shown in  FIG. 1 . A second glass panel  304  is mounted to two lateral rails  308  which are secured to the external panel  302 . Retainers  306  mounted to the external panel  302  may also aid in securing the second glass panel  304  so as to prevent movement of the second glass panel  304 . The second glass panel  304  is constructed in such a way that it is optically transparent but not transparent to microwaves. A user interface (UI)  310  may also be mounted to the external panel  302  where a third aperture, not shown, formed in the external panel  302  may correspond to a display, not shown, of the UI  310 . The UI  310  may function to operate the microwave oven  100  and to display a plurality of information. 
         [0016]      FIG. 3  shows a perspective view of a microwave oven door structural assembly  400  according to an embodiment of the invention. The structural assembly  400  includes the choke frame  220 , the first pane of glass  224 , the second pane of glass  226 , and the hinge  228 . The choke frame  220  may also include a metal reed  222  positioned between the first and second panes of glass  224 ,  226  so as to communicate with the dividing shelf  114  shown in  FIG. 1  and provide electrical continuity with the dividing shelf  114  when the door  200  is in the second (closed) position. The metal reed  222  may be formed integrally with the choke frame  220  or securely mounted to the choke frame  220 . It is preferred that the width of the metal reed  222  be minimized in order to maximize the size of the first and second panes of glass  224 ,  226  while ensuring sufficient communication between the metal reed  222  and the dividing shelf  114  to attenuate microwave transmission between the first and second sub-cavities  116 ,  118  also shown in  FIG. 1 . 
         [0017]      FIG. 4  shows an exploded view of a partially assembled microwave oven door  500  according to an embodiment of the invention. The partially assembled microwave oven door  500  shows the structural assembly  400  mounted to the aesthetic assembly  300  where the choke frame  220  is seated on the lateral rails  308  and a choke frame cover  502  encompasses the choke frame  220  and secures it to the lateral rails  308 . At least one and preferably two pins  506  may be secured to the choke frame cover  502 . The pins  506  may be received by apertures, not shown, in the cabinet  120  of  FIG. 1  in order to secure the door  200  to the cabinet  120  when the door  200  is in the second position. A UI cover  504  may be positioned over the UI  310  and secured to the external panel  302  to protect the UI  310  and provide an aesthetic appearance. 
         [0018]    The structural assembly  400  is mounted to the aesthetic assembly  300  in such a way that the second glass panel  304  shown in  FIG. 2  is spaced apart from the first and second panes of glass  224 ,  226 , best shown in  FIG. 6 , so as to provide a layer of thermal insulation between the panes of glass  224 ,  226  and the second glass panel  304 . Furthermore, the first and second apertures  312 ,  314 , in the external panel  302  substantially align with the first and second glass panels  224 ,  226  so as to provide visibility into the sub-cavities  116 ,  118  shown in  FIG. 1 . 
         [0019]      FIG. 5  shows a cross sectional view of a microwave oven  600  according to an embodiment of the invention with the door  200  in the second (closed) position. The choke frame  220  forms a seal with the cooking cavity aperture perimeter  122  to attenuate the transmission of microwaves between the cooking cavity  112  and door  200 . The metal reed  222  forms a seal with dividing shelf  114  to attenuate the transmission of microwaves between the first and second sub-cavities  116 ,  118 . The first and second panes of glass  224 ,  226  and the second glass panel  304  also attenuate transmission of microwaves from the cooking cavity  112  or the first or second sub-cavities  116 ,  118 . The dividing shelf  114  is also constructed in such a way, that it attenuates the transmission of microwaves between the first and second sub-cavities  116 ,  118 . 
         [0020]    Microwave energy may be selectively introduced to the first and second sub-cavities  114 ,  116  through at least a first and second wave guide  602 ,  604  corresponding, respectively, to the first and second sub-cavities  116 ,  118 . Each wave guide  602 ,  604  may be supplied microwaves from a separate microwave generator including but not limited to a magnetron or a solid state radio frequency (RF) device to independently cook foodstuffs located in the two sub-cavities  116 ,  118 . 
         [0021]    In a preferred embodiment, the transmitted microwave bandwidth of each of the wave guides  602 ,  604  may include frequencies ranging from 2.4 GHz to 2.5 GHz. The wave guides  602 ,  604  may be configured to transmit other microwave frequency bands. For example, the bandwidth of frequencies between 2.4 GHz and 2.5 GHz is one of several bands that make up the industrial, scientific and medical (ISM) radio bands. In another embodiment, the transmission of other microwave frequency bands is contemplated and may include non-limiting examples contained in the ISM bands defined by the frequencies: 13.553 MHz to 13.567 MHz, 26.957 MHz to 27.283 MHz, 902 MHz to 928 MHz, 5.725 GHz to 5.875 GHz and 24 GHz to 24.250 GHz. 
         [0022]    Now referring to  FIG. 6 , there is shown a closer cross sectional view  700  showing the metal reed  222  and dividing shelf  114  interface according to an embodiment of the invention. The dividing shelf  114  may be provided with a gasket  702  configured to communicate with the metal reed  222  wherein the metal reed  222  is positioned to provide electrical continuity with the gasket  702  disposed on the dividing shelf  114  when the door  200  is in the second position in order to attenuate the transmission of microwaves between the first and second sub-cavities  116 ,  118 . The gasket  702  may be made from any suitable gasket material having electrical conductivity in the range of 0.1          /cm 2  to 10          /cm 2 . The gasket  702  may also be disposed around all four sides of the dividing shelf  114  so as to communicate with the walls of the cooking cavity  112 , shown in  FIG. 1 , to provide electrical continuity and to attenuate the transmission of microwaves between the first and second sub-cavities  116 ,  118 . 
         [0023]    The dividing shelf  114  may have a structural layer  704  that is not transparent to microwaves, an intermediate thermal insulation layer  708  and an upper dielectric layer  706 . The structural layer  704  may essentially form a rectangular box with an aperture in the top side of the box. One example of a suitable structural layer  704  of a dividing shelf  114  is disclosed in U.S. Patent Application No. 2013/0153570, published Jun. 20, 2013, which is incorporated herein by reference in its entirety. The dielectric layer  706  may be disposed over the aperture and be supported by the structural layer  704  and may be suitable for cooking a foodstuff placed directly on the dielectric layer  706 . By spacing the dielectric layer  706  a suitable distance away from the lower portion of the structural layer  704  which is not transparent to microwaves, efficient microwave cooking of foodstuff placed directly on the dielectric layer  706  may be achieved. The thermal insulation layer  708  may either partially or entirely fill the area between the structural layer  704  and the dielectric layer  706  with a suitable thermally insulating material to provide a layer of thermal insulation between the first and second sub-cavities  116 ,  118 . Furthermore, the space between the second glass panel  304  and the metal reed  222  and first and second panes of glass  224 ,  226  provide a layer of thermal insulation between the first and second sub-cavities  116 ,  118  and the external panel  302 . 
         [0024]    In accordance with one embodiment, at least the metal reed  222 , choke frame  220 , second glass panel  304 , first and second panes of glass  224 ,  226 , gasket  702 , and structural layer  706  of the dividing shelf  114  may be optimized in at least one of both materials and configuration to attenuate transmission of microwave frequencies ranging from 2.4 GHz to 2.5 GHz. The dielectric layer  706  and thermal insulation layer  708  may be optimized in at least one of both materials and configuration to promote the transmission of microwave frequencies ranging from 2.4 GHz to 2.5 GHz. 
         [0025]    It is contemplated that the present disclosure encompasses at least the following inventive concepts: 
         [0026]    Oven Door Structure 
         [0027]    1. A microwave oven comprising a cooking cavity, a dividing shelf for dividing the cooking cavity into first and second sub-cavities, and a door movable between a first position for simultaneous access to the first and second sub-cavities and a second position for preventing simultaneous access to the first and second sub-cavities, characterized by: 
         [0028]    a choke frame on the door, wherein the choke frame is in communication with the dividing shelf when the door is in the second position to attenuate microwave transmission between the first and second sub-cavities. 
         [0029]    2. The microwave oven of 1, wherein the choke frame includes a conductive reed positioned to provide electrical continuity with the dividing shelf when the door is in the second position. 
         [0030]    3. The microwave oven of 1 or 2, further comprising at least two panes of glass disposed in the door corresponding, respectively, to the first and second sub-cavities. 
         [0031]    4. The microwave oven of 3, wherein the choke frame encompasses the at least two panes of glass. 
         [0032]    5. The microwave oven of any one of 3-4, wherein the door further includes a glass panel mounted to lateral rails and spaced from the at least two panes of glass for thermal insulation. 
         [0033]    6. The microwave oven of 5, further comprising a cover to secure the choke frame to the lateral rails. 
         [0034]    7. The microwave oven of any one of 1-6, further comprising a user interface on the door. 
         [0035]    8. The microwave oven of any one of 1-7, wherein the dividing shelf has a gasket on at least one side thereof to communicate with the choke frame. 
         [0036]    9. The microwave oven of 8, wherein the dividing shelf has a gasket on all sides thereof so as to communicate with the walls of the cooking cavity to provide electrical continuity and to attenuate the transmission of microwaves between the sub-cavities. 
         [0037]    10. The microwave oven of any one of 1-8, wherein the dividing shelf has thermal insulation material between a top and bottom surface thereof. 
         [0038]    Dividing Shelf for a Microwave Oven 
         [0039]    1. A microwave oven comprising a cooking cavity, and a dividing shelf for dividing the cooking cavity into first and second sub-cavities characterized by: 
         [0040]    the dividing shelf having a gasket disposed around all sides thereof to attenuate the transmission of microwaves between the sub-cavities, an upper dielectric layer, and a lower structural layer that is not transparent to microwaves and spaced from the upper dielectric layer with thermal insulation material between the upper dielectric layer and lower structural layer. 
         [0041]    2. The microwave oven of 1, wherein the upper dielectric layer includes glass. 
         [0042]    3. The microwave oven of 1 or 2, wherein the lower structural layer is metal. 
         [0043]    4. The microwave oven of any of 1-3, wherein the lower structural layer forms a rectangular box with an aperture in a top side of the box. 
         [0044]    5. The microwave oven of 4, wherein the upper dielectric layer is disposed over the aperture. 
         [0045]    6. The microwave oven of any of 1-5, wherein the gasket or the lower structural layer is optimized in at least one of material or configuration to attenuate transmission of microwave frequencies ranging from 2.4 GHz to 2.5. 
         [0046]    7. The microwave oven of any of 1-6, wherein the upper dielectric layer or the thermal insulation material is optimized in at least one of material or configuration to promote transmission of microwave frequencies ranging from 2.4 GHz to 2.5. 
         [0047]    The embodiments described above provide for a variety of benefits including the attenuation of microwave transmission between multiple cavities in a microwave oven such that foodstuffs contained in different cooking cavities may be cooked at the same time and independently of each other resulting in more even cooking and reduced cooking time. 
         [0048]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.