Microwave Oven

The present invention relates to a patent application MICROWAVE OVEN, Ser. No. 971,727, filed Oct. 21, 1978, by James E. Simpson, which is assigned to the assignee of the present invention and to a patent application MICROWAVE OVEN HAVING ROTATING CONDUCTIVE RADIATORS, Ser. No. 965,636, filed Dec. 1, 1978, by John M. Osepchuk, which is assigned to the parent company of the assignee of the present invention.

1. Field of the Invention

The present invention relates generally to heating with electromagnetic wave energy in a conductive cavity, and more particularly, pertains to an antenna assembly including a directional rotating antenna, an antenna rotor, an antenna rotating assembly, and a grease shield for directing air flow velocity to drive the antenna rotor to axially rotate the directional antenna axially supported by the antenna rotating assembly.

2. Description of the Prior Art

Prior art microwave ovens suffer from nonuniform energy distribution, and more particularly, nonuniform heating patterns depending upon the type of particular product, which usually is food, being heated. The nonuniform heating pattern occurs because of the unequal distribution of microwave energy coupled into a conductive cavity of a microwave oven from a source of microwave power such as a magnetron, from the reflections of microwave energy from the product within the microwave oven cavity, and the conductive sidewalls framing the microwave oven cavity. Multiple reflections within the conductive microwave oven cavity occur and produce configurations of the electromagnetic fields referred to as modes. These reflections cause constructive and destructive interference at and in different parts of the product being heated, and therefore, result in hot areas intermixed with cold areas. Where the product is food, the result is overcooked areas of the food intermixed with undercooked areas of the food.

Some food products which have been particularly difficult to cook in the prior art microwave ovens include yeast products such as breads; baked products such as cakes and pies; scattered products such as cookies, appetizers, and hors d'euvres, and; egg dishes such as custards and quiches. All of these types of food products when cooked in the prior art microwave ovens have exhibited overcooked areas intermixed with undercooked areas leaving much to be desired in the cuisine of the consuming gourmet.

The prior art processes for improving the nonuniform energy distribution patterns in the prior art microwave ovens have been mode stirring which attempts to randomize reflections by introducing a time varying scattering of the microwave energy; utilizing a turntable within the microwave oven cavity to rotate the product about a vertical axis within the microwave oven separately or in combination with a mode stirrer; and, utilizing rotatable antennas within the microwave oven cavity.

The prior art process of utilizing rotatable antennas or exciters within the microwave oven cavity has been deficient from the point that rotatable antennas or exciters within the microwave oven cavity failed to achieve a uniform energy distribution and complex mechanical structure has been required to support and rotate the antennas.

In rotating physical structures within the microwave oven cavity, a rotating mechanism such as an electric motor was required along with suitable mounting of the motor, isolating the motor and shaft from the electromagnetic field within the microwave oven cavity, and providing additional energy to power and drive the electric motor. Further, the prior art rotation assemblies of either turntables or antennas were always subject to mechanical breakdown and in the event of mechanical breakdown, a skilled serviceman was required to service the mechanical working components of the microwave oven.

The present invention provides a microwave oven having a uniform energy distribution pattern and overcomes the disadvantages of the prior art microwave ovens.

The purpose of the present invention is to provide a microwave oven with an antenna assembly including a directional rotating antenna which axially rotates about an axis of the microwave oven cavity and an antenna rotating assembly which locks and unlocks in engagement in the wall of the cavity. The directional rotating antenna supports an antenna rotor including a plurality of turbine vanes, which when struck by air flow velocity circulated through the cavity, rotates about the center axis of the directional rotating antenna. Another purpose of the present invention is to provide a grease shield to direct the air flow velocity of air past the turbine vanes, past the front of the microwave oven door to clear the door of moistures and vapors, exhaust the air through the top wall of the microwave oven cavity, and out through a vent in the front of the microwave oven.

According to one embodiment of the present invention, there is provided an antenna assembly for a microwave oven including an antenna rotating assembly supported on an axis of a horizontal wall of a microwave oven cavity and having at least one axially rotatable bearing; plurality of fingers extending outwardly from the antenna rotating assembly which provide for engagement and disengagement of the antenna assembly on the wall from within the confines of the cavity; a directional rotating antenna in the cavity having a probe antenna extending between the cavity and waveguide and supported by the axially rotatable bearing; and, an antenna rotor having a plurality of turbine vanes extending radially outward whereby the probe antenna couples energy from a microwave power source to the directional rotating antenna and the velocity of the air flow circulated through the microwave oven cavity strikes the vanes of the antenna rotor to axially rotate the directional rotating antenna about the axis of the axially rotatable bearing thereby providing uniform energy distribution and consistent heating in the microwave oven cavity.

According to another embodiment of the present invention, there is provided a grease shield for shielding the top wall of a microwave oven cavity from splatter including a plurality of upwardly extending vertical members in the rear of the grease shield to direct incoming air flow from holes in the rear of the cavity to the front of the cavity above the grease shield and driving directional rotating antenna having an antenna rotor including turbine vanes; a plurality of perforations in a forward portion of the grease shield to exhaust air from between the top wall of the cavity and the grease shield into the cavity; and, a plurality of longitudinal perforations adjacent to the door to exhaust air out of the cavity whereby the grease shield is removable for cleaning and for access to the antenna assembly in the top wall of the cavity.

One significant aspect and feature of the present invention is an antenna assembly having an antenna rotating assembly including the directional rotating antenna which supports and engages with the antenna rotor. The antenna assembly can be installed and removed from within the immediate confines of the microwave oven cavity with a U-shaped tool. If the need arises to replace the antenna rotating assembly which is extremely unlikely but in such an unlikely event, it is necessary to remove the screws of the grease shield and subsequently remove the antenna assembly with a U-shaped tool which extends up through two holes in the directional rotating antenna and into a bushing of the antenna rotating assembly. With a counterclockwise twist, the antenna assembly unlocks from the top wall of the microwave oven and is removed from within the interior confines of the microwave oven cavity.

Another significant aspect and feature of the present invention is to provide a grease shield which can be removed from the microwave oven for cleaning by the user by removing screws from the microwave oven thereby permitting the user to keep the microwave oven in cleanliness condition.

Having briefly described one embodiment of the present invention, it is a principal object hereof to provide a microwave oven having a removable antenna assembly and a removable grease shield, both attributing to uniform energy distribution and consistent heating within the microwave oven.

An object of the present invention is to provide uniform energy distribution of microwave energy and a consistent uniform heating pattern in a product being heated in the cavity, especially food, by an antenna assembly axially rotated about an axis of one wall of the microwave oven cavity. The present invention provides uniform heating of foods, especially sensitive foods, over short periods of time. The present invention provides for the microwave cooking of sensitive foods such as yeast breads, cakes, quiches, and scattered loads such as cookies. The microwave cooking of foods according to the present invention is faster for small and compact loads, and require virtually no manual manipulations of the food during microwave cooking even though cooking manipulations may be required depending upon the type of food being cooked.

Another object of the present invention is to provide an antenna assembly for uniform microwave energy distribution and consistent heating in a product being heated within a microwave oven cavity of a microwave oven. The antenna assembly includes a directional rotating antenna axially supported in the antenna rotating assembly, and an antenna rotor supported and engaged to the directional rotating antenna. A probe antenna affixes to a common junction of the directional rotating antenna. The antenna rotating assembly has at least one axial component supporting the probe antenna. The antenna rotating assembly includes a plurality of outwardly extending fingers to lock the antenna assembly into position in the top wall of the microwave oven cavity. The antenna is a two-by-two array of four end driven half-wavelength resonating elements which are connected to the axially supported probe near the center of the microwave oven cavity by support elements and microstrip parallel plate transmission feed line conductors. The antenna rotor includes a dielectric disc having a plurality of outwardly radially extending circumferentially spaced vanes to receive air flow velocity in a turbine manner and a plurality of downward extending U-shaped channel members having slots from the dielectric disc to encompass the support members between the resonating elements and the parallel plate transmission line conductors.

A further object of the present invention is to provide a microwave oven having a removable grease shield for cleaning of the grease shield and for installation of the antenna assembly. The grease shield is affixed to the top wall of the microwave oven cavity with a plurality of screws and is removable for cleaning in the event as required.

An additional object of the present invention is to provide an antenna assembly which is easily manufactured and assembled, and does not require complex mechanical machinery for manufacture or assembly. The antenna rotating assembly includes molded plastic components. The directional rotating antenna is stamped and subsequently formed by two complimentary actions of wiping dies. The antenna rotor is a molded plastic component. A still further object of the present invention is to provide a grease shield in the microwave oven cavity of the microwave oven cavity which directs air flow velocity to vent the microwave oven cavity of moisture and cooking vapors, and more importantly, directs the air flow velocity to rotate the antenna assembly including the directional rotating antenna in a clockwise direction about a vertical axis of the microwave oven cavity. The air flow velocity is forced through the microwave oven and the microwave oven cavity including the space between the top wall of the microwave oven cavity and the grease shield in a direct path of least resistance providing for cooling of not only the internal power supply components of the microwave oven but also venting of the microwave oven cavity of vapors and moisture.

A still additional object of the present invention is to provide a microwave oven cavity having uniform energy distribution and providing uniform heating of a product in a microwave oven cavity, especially food products. Particularly, the microwave oven of the present invention provides for consistent even heating in foods such as baked goods and yeast products over short periods of time. Specifically, the microwave oven of the present invention has overcome the shortcomings of the prior art by providing a microwave oven which consistently and evenly cooks baked goods, yeast breads, quiches, in addition to cooking of scattered products such as cupcakes, appetizers, hors d'oeuvres, hot dogs, sausage, hamburgers, bacon, etc., and the ordinary foods usually cooked in the microwave ovens. The microwave oven also cooks such foods as cookies, egg dishes such as egg custards, and yeast breads. The microwave oven further cooks roasts, meatloafs, chickens, turkeys, and other large body meats. Finally, the microwave oven provides uniform energy distribution and heating so that evaporation of the moisture from the food product is minimum and the foods retain moisture during cooking.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood, by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 illustrates a front view of a microwave oven of the present invention;

FIG. 2 illustrates a section of the present invention taken on line 2--2 of FIG. 1 looking in the direction of the arrows and illustrates a section of the present invention;

FIG. 3 illustrates a section of the present invention taken on line 3--3 of FIG. 1 looking in the direction of the arrows and illustrates a side view of the microwave oven;

FIG. 4 illustrates a section of the present invention taken on line 4--4 of FIG. 2 looking in the direction of the arrows and illustrates an upper vertical sectional view of the microwave oven;

FIG. 5 illustrates an exploded vertical sectional view of the components of an antenna rotating assembly 36;

FIG. 6 illustrates a vertical sectional view of the antenna rotating assembly of FIG. 5 assembled;

FIG. 7 illustrates a top view of an antenna assembly prior to locking engagement in a dome wall;

FIG. 8 illustrates a top view of an antenna assembly locked in engagement in a dome wall;

FIG. 9 illustrates a top perspective view of the antenna assembly locked in engagement with the dome wall;

FIG. 10 illustrates a side view of the antenna assembly prior to bending resonating elements of a directional rotating antenna in an antenna rotor;

FIG. 11 illustrates a side view of the antenna assembly;

FIG. 12 illustrates a bottom view of the antenna assembly;

FIG. 13 illustrates a section of the present invention taken on line 13--13 of FIG. 4 looking in the direction of the arrows and illustrates a view looking upwardly towards a grease shield;

FIG. 14 illustrates a section of the grease shield taken along the lines 14--14 of FIG. 4 and illustrates a top view looking downwardly towards the grease shield;

FIG. 15 illustrates a section of the grease shield looking in the direction of the arrows 15--15 of FIG. 14 and illustrates a cutaway view of the grease shield; and,

FIG. 16 illustrates a vertical sectional view of another embodiment of the present invention.

FIG. 1, which illustrates a front view of a microwave oven 10 of the present invention, shows the microwave oven 10 having a three-sided channel shaped housing cover 12a-12c respectively housing and enclosing the internal components of the microwave oven 10 as now described. A microwave oven cavity 14 of the microwave oven 10 as also illustrated in FIG. 4 includes five metallic conductive sides, such as stainless steel by way of example and for purposes of illustration only, and includes a top wall 14a, a bottom wall 14b not illustrated in the figures, a left sidewall 14c and a right sidewall 14d illustrated in FIG. 4, and a rear wall 14e which are secured to each other such as by welding to form the five-sided conductive microwave oven cavity 14. A bottom hinged door 16 pivots within the confines of the walls 14a-14d of the microwave oven cavity 14, and includes a microwave energy absorbing structure such as quarter wave choke and a carbon impregnated door gasket surrounding the outside perimeter of the door 16 to dissipate any leakage of microwave energy between the walls 14a-14d and the outer perimeter of the door 16. A see-through window, by way of example and for purposes of illustration only, affixes in the center of the door 16. A door handle 16a on the top of the hinged door 16 facilitates opening and closing of the door 16. A cake 17 in a glass cake pan 19 cooks in the microwave oven 10 and is observed through the door 16. An automatic safety latch lever not illustrated in the figure mounts on one side of the door 16 to lock the door 16 in a closed position when the microwave oven 10 is energized. A control panel 18 supports a plurality of programmable keyboard controls connected to microprocessor control circuitry or electromechanical control circuitry to control a microwave oven power supply connected to a microwave power source for predetermined heating time, temperature, and power levels. Start, stop, and microwave cavity light switches 18a, 18b, and 18c respectively are positioned at the bottom of the control panel 18. An exhaust vent 20 mounts in the upper front right corner of the microwave oven 10 directly above the control panel 18 to exhaust cavity vapors and moisture from the microwave oven cavity 14 as later described.

FIG. 2, which illustrates a section of the present invention taken on line 2--2 of FIG. 1 looking in the direction of the arrows and partially cutaway, shows a top view of the microwave oven 10. A flattened conical shaped dome 22 having a large diameter 22a positions in the top wall 14a of the microwave oven cavity 14. An angular sloping section 22b including a planar rectangular transition section 24 as later described extends above the top wall 14a of the microwave oven cavity 14 to a small diameter 22c which determines the angular degree of the slope of the dome 22. A planar flattened truncated top wall 22d of the dome 22 is parallel to the top wall 14a of the microwave oven cavity 14. The rectangular transition section 24 provided on the angular slope section 22b of the dome 22 includes a lower transition junction 24a between the top wall 14a of the microwave oven cavity 14 and the transition section 24, and an upper transition junction 24b between the transition section 24 and the flattened wall 22d of the dome 22. A front junction 24c and a back junction 24d extend between the junctions 24a and 24b respectively along the longitudinal length of the transition section 24. A three-sided waveguide 26 having tapers on the two opposing vertical sidewalls 26b and 26c corresponding to the tapers of the rectangular dome 22 and transition 24 as also illustrated in FIG. 3, affixes between the microwave power source 28 having an antenna 28a on a top wall extension 14a.1 of the top wall 14a of the microwave oven cavity 14 and to a point beyond the center 22e on the flat truncated wall 22d of the dome 22. The waveguide 26 includes a top wall 26a, vertically tapered sidewalls 26b and 26c, and end walls 26d and 26e where the distance between the end wall 26e to the center 22e of the dome 22 compensates the matching of the microwave power source 28 to the microwave oven cavity 14 as later described. Flanges 30b, 30c, 30d, and 30e are provided at the bottom of the waveguide sidewalls 26b, 26c, 26d, and 26e respectively of the waveguide 26 to affix the waveguide 26 to the top wall extension 14a.1, the top wall 14a, the tapered section 24, the slope 22c of the dome 22, and the top wall 22d of the dome 22, all of which serve as the fourth bottom wall of the three-sided waveguide 26 respectively. A directional rotating antenna 32 illustrated in dashed lines and also referring to FIGS. 4 and 12 includes four end driven half-wavelength resonating elements 23a-32d parallel to the top wall 14a and dome wall 22d, vertical supports 32e-32h connected to each of the elements 32a-32d, microstrip parallel plate transmission line conductors 32i-32l parallel to the top wall 14a of the microwave oven cavity 14 and dome wall 22d which connect to each of the vertical supports 32e-32h, and join at a junction 32m. A probe antenna 34 having a capacitive hat 34a axially mounts in a dielectric antenna rotating assembly 36 located at the center 22e of the flattened wall 22d of the dome 22 as later described in detail in FIGS. 5-9 and connects to the junction 32m of the directional rotating antenna 32. The probe antenna 34 extends between the microwave oven cavity 14 and partially into the waveguide 26 above the top wall 22d of the dome 22. A dielectric circumferential disc 38 surrounds the parallel plate transmission line conductors 32i-32l and affixes thereto. A plurality of turbine vanes 38a-38f are circumferentially positioned around the circular disc 38 and are driven by forced air flow velocity circulated through the microwave oven cavity 14 as later described in detail. A blower 40, such as a squirrel cage blower by way of example and for purposes of illustration only, draws air up through a plurality of holes not illustrated in the bottom of the microwave oven 10, between the bottom of the microwave oven 10 and the bottom wall 14b of the microwave oven cavity 14, past the control panel 18 and the microwave oven power supply components as later described, through the blower 40, past the heat dissipating plates of the microwave power source 28, and up through side and rear perforations 42a and 42b respectively in the rear right corner of the top wall extension 14a.1 of the top wall 14a. Rear and rear side perforations 44a and 44b respectively having a plurality of holes provide for air flow into a horizontal space between the top wall 14a and a grease shield 46, also referred to as a splatter shield, illustrated in FIG. 4. A longitudinal vertical upright extending member 48 longitudinally extending the length of the microwave oven housing 12b directs the air flow from the right rear, through the holes 42a and 42b, above the extension wall 14a of the top wall 14a, past the waveguide 26, past the dome 22, and into the rear and side vent holes 44a and 44b. A right angular member 44c directs the air flow through the rear side holes and also serves as a light reflector for a light bulb not illustrated for purposes of clarity. Vertical directional vanes 46a-46c and 46d as illustrated in dashed lines extend vertically upwardly on the grease shield 46 to force the air flow velocity to drive the turbine vane blades 38a-38f in a counterclockwise direction thereby rotating the directional rotating antenna 32 about the center 22e of the dome 22. Air is exhausted out of the space between the grease shield 46 and the top wall 14a at louvers 46e, 46f, and 46g of the grease shield 46 into the microwave oven cavity 14. A plurality of vent holes 50 in the left front corner of the top wall 14a of the microwave oven cavity 14 provide for exhausting of additional air out through the holes 50 in the microwave oven cavity 14. An upwardly vertical extending perforated cavity exhaust panel 14a.2 of the top wall 14a is provided with a plurality of holes 52 which provides for exhausting of vapor and moisture through the longitudinal louvers 46h in the grease shield 46 including a complimentary vertically upwardly extending member 46i. Consequently, the air flow velocity exhausts vapors and moisture out through the front exhaust vent 20.

FIG. 3, which illustrates a section of the present invention taken on line 3--3 of FIG. 1 looking in the direction of the arrows, shows a side view of the microwave oven 10. Air is drawn in through a plurality of holes in the bottom of the microwave oven 10 not illustrated for purposes of clarity in the illustration, between the bottom of the microwave oven 10 and the bottom of the microwave oven cavity 14b; around past the rectifier assembly, the transformer, and the control circuitry; up through the blower 40; through the heat dissipating plates of the microwave power source 28; up through the side and rear perforations 42a and 42b; and, down the longitudinal area between the vertical member 48 and the back wall of the microwave oven housing. The air is then forced into the cavity 14, through the cavity 14, out of the cavity 14, and out through the front exhaust vent 20 as later described.

FIG. 4, which illustrates a section of the present invention taken on line 4--4 of FIG. 2 looking in the direction of the arrows, shows a side view of the top wall 14a of the microwave oven cavity 14, the dome 22, the large diameter 22a, the angular slope 22b, the small diameter 22c, the flattened top wall 22d, the center of the dome 22e, the rectangular transition 24, the lower junction 24a, the upper junction 24b, the waveguide 26, the top waveguide wall 26a, the waveguide sidewall 26c, the waveguide end walls 26d and 26e respectively, the microwave power source 28 including the antenna 28a, the flanges 30d and 30e, the directional rotating antenna 32, the end driven half-wavelength resonating elements 32a and 32c, the vertical connecting members 32e and 32g, the parallel plate microstrip transmission line conductors 32i and 32k, the probe antenna 34, the antenna rotating assembly 36 as described below in detail in FIGS. 5-9, the antenna support 38 including the turbine vanes 38a, 38b, 38c, 38d, 38e and 38f shown in FIG. 12, and the grease shield 46 of the microwave oven 10.

FIG. 5, which illustrates an exploded vertical sectional view of the components of the antenna rotating assembly 36 and also referencing FIGS. 6-9 shows the antenna rotating assembly 36 including in order, a dielectric bushing 36a, a dielectric washer 36b, a dielectric bearing 36c, and a dielectric antenna cap 36d where each component of the assembly 36 is now described in explicit detail. The bushing 36a of dielectric material such as plastic includes a plurality of horizontal outward extending ring or lip sections 36a.1-36a.3, vertical upward extending members 36a.4-36a.6 connected to the respective rings 36a.1-36a.3, horizontal extending members 36a.7-36a.9 and downward extending keys 36a.10-36a.12 connected to the respective elements as also illustrated in the other figures. A plurality of keyway sections 22h.1-22h.3 are circumferentially positioned in an aperture 22g of the top wall 22d of the dome 22, and provide for clearance of the respective elements 36a.4-36a.12 of antenna rotating assembly 36. An internal diameter of partially decreasing taper 36a.13 geometrically coincides with the external taper 36c.1 of the bearing 36c as later described. The internal diameter 36a.13 includes an upper and lower vertical contact surface sections 36a.13a and 36a.13b respectively of finite height and no draft. A downwardly extending member 36a.14 provides additional length of the external taper 36c.1 of the axial bearing 36c and supports the lower vertical contact surface section 36a.13b. A plurality of moisture drain holes 36a.15-36a.20 extend entirely through the base of the bushing 36a and provide for drainage in cores 36a.21-36a.23 of the bushing 36a as illustrated in FIG. 9. Two antenna assembly installation holes 36a.24 and 36a.25, which hold the directional rotational antenna 32 and the bushing 36 in alignment during installation, extend partially upwards into the base of the bushing 36a as illustrated. The dielectric washer 36b such as low friction Teflon having inner and outer diameters equal to inner and outer diameters of horizontal surface 36a.26 and bearing 36c coincides therewith at horizontal surface 36c.2. The bearing 36c includes internal diameters 36c.3 and 36c.4 which accept the outer diameters of the probe antenna 34 including the capacitive top hat 34a. The external taper 36c.1 includes an upper and lower vertical contact surface sections 36c.1a and 36c.1b respectively of finite height and no draft. The vertical contact surfaces 36a.13a and 36c.1a, and 36a.13b and 36c.1b contact each other respectively during axial rotation of the bearing 36c in the bushing 36a. The tapers 36a.13 and 36c.1 geometrically coincide but do not contact each other during axial rotation. The antenna cap 36d having an internal diameter 36d.1 accepts an external diameter 36c.5 of the bearing 36c. A plurality of lock tabs 36d.2-36d.5 extend outwardly from the internal diameter 36d.1 of the antenna cap 36d to engage against the external diameter 36c.5 of the bearing 36c. A hole 32n at the junction 32m of the directional rotating antenna accepts the threaded portion 34.1 of the probe antenna 34 and abuts up against the bottom lip 34.2 of the probe antenna 34 so as to be tightly secured to the bottom lip 34.2 by the nut 34.3 of the probe antenna 34. Holes 32o and 32p in the transmission line conductors 32i and 32k of the directional rotating antenna 32 coincide with the antenna mounting holes 36a.24 and 36a.25 in the bushing 36a for mounting the antenna 32, the bushing 36a and the antenna rotor 38 as later discussed into the top wall 22d of the dome 22 as later described in detail.

FIG. 6 illustrates a vertical sectional view of the antenna rotating assembly 36 of FIG. 5 assembled and positioned in the top wall 22d of the dome 22 in the aperture 22g and axially supporting the antenna 32 as illustrated. A mounting member 54 having parallel opposing arms 54a and 54b extends through the antenna mounting holes 32o and 32p of the antenna 32 and into the antenna mounting holes 36a.24 and 36a.25 of the bushing 36a. An antenna rotor 38 not illustrated has an inner hole 38l as illustrated in FIG. 12 to provide clearance for the arms 54a and 54b. All numerals correspond to the elements delineated in FIG. 5.

FIG. 7 illustrates the antenna assembly 56 prior to locking into engagement with the upwardly extending teeth 22f.1-22f.3 of the dome wall 22d. The antenna assembly 56 including the antenna rotating assembly 36, the antenna 32 not illustrated, and the antenna rotor 38 not illustrated, are pushed up through the aperture 22g at the center 22e of the top wall 22d of the dome 22 from within the interior confines of the microwave oven cavity 14 to the position where the rings 36a.1-36a.3 of the antenna rotating assembly 36 coincide and abut up against the bottom of the top wall 22d of the dome 22. Subsequently, the antenna assembly 56 is rotated in a counterclockwise direction as viewed from the top into the engaged and locked position illustrated in FIG. 8.

FIG. 8 illustrates a top view of the antenna assembly 56 where the keys 36a.10-36a.12 are locked into engagement with the upwardly extending teeth 22f.1-22f.3 respectively of the dome 22. The bearing 36c not illustrated axially rotates in the bushing 36a when the velocity of air flow strikes the turbine vanes 38a-38f of FIG. 12 of the antenna rotor 38 supported on the directional rotating antenna 32.

FIG. 9 illustrates a top perspective view of the antenna assembly 56 locked into engagement in the top wall 22d of the dome 22. All numerals correspond to those elements previously delineated.

FIG. 10, and also referring to FIGS. 11 and 12, illustrates a side view of the antenna assembly 56 including the antenna 32 prior to bending the resonating elements 32a-32d, the antenna rotating assembly 36 as previously described in detail in FIGS. 5-9, and the antenna rotor 38 as now described in detail. The antenna rotor 38 includes a plurality of outwardly extending turbine vane blades 38a-38f affixed in an equal angular displacement around the center of the disc 38g as illustrated in FIG. 12. Four longitudinal downwardly extending slotted rectangular keyways 38h-38k extend perpendicular to the disc 38g and receive the respective vertical supports 32e-32h of the directional rotating antenna 32. The resonating elements 32a-32d of the antenna are pushed through the rectangular slotted keyways 38h-38k of the antenna rotor 38 as illustrated in FIG. 10 to the position where the slots surround the vertical supports 32e-32h and the parallel plate transmission line conductors 32e- 32h engage against the top of disc 38g of the antenna rotor 38.

FIG. 11 illustrates a side view of the antenna assembly 56 including the directional rotating antenna 32 supporting the antenna rotor 38 and axially supported by the antenna rotating assembly 36. The antenna rotor 38 affixes to the directional rotating antenna 32 by opposing right angle bends in the vertical supports 32e-32h between the parallel plate transmission line conductors 32i-32l and the resonating elements 32a-32d thereby locking the directional rotating antenna 32 to the antenna rotor 38.

FIG. 12 illustrates a bottom view of the antenna assembly 56 including the directional rotating antenna 32 supporting the antenna rotor 38 and axially supported in the antenna rotating assembly 36 as previously described.

FIG. 13, which illustrates a section of the present invention taken on line 13--13 of FIG. 4 looking in the direction of the arrows, shows the grease shield 46, which includes the upwardly extending vertical directional vanes 46a-46d illustrated in dashed lines extending upwardly on the grease shield to force the velocity of the air flow from the vent holes 44a and 44b in a clockwise direction to drive the turbine vane blades 38a-38f of the antenna rotor 38 about the center axis 22e of the dome 22 thereby rotating the directional rotating antenna 32 about the center axis of the dome 22. Upwardly extending vertical members 46d provides that the air flow velocity continues in a circular pattern towards the antenna assembly 56. The plurality of louvers 46e-46g in the grease shield 46 exhaust air into the cavity. A vertical member 46j extends upwardly between the grease shield and the top wall 14a of the microwave oven cavity 14 and is connected to the top wall 14a by screws 51a-51d. Longitudinal louvers 46h exhaust air from the microwave oven cavity between the grease shield 46 and the top wall 14e, and around past the front wall 14a.2 through the holes 52 in the vertical member as shown in FIG. 2. The front vertical extending member 46i extends upwardly from the grease shield 46. A plurality of teats 46k.1-46k.4 extend outwardly from the rear of the grease shield 46 and protrude into respective holes 14e.1-14e.4 in the rear wall 14e of the microwave oven 10 to securely engage the rear of the grease shield 46 into rear wall 14e.

FIG. 14 illustrates a section of the grease shield 46 taken along the lines 14--14 of FIG. 4 which illustrates a top view looking down on the grease shield in position in the microwave oven cavity 14. All numerals correspond to those numerals previously delineated.

FIG. 15 which illustrates a section looking in the direction of the arrows 15--15 of FIG. 14 shows a side cutaway view of the grease shield 46 and more particularly, shows the directional vanes 46e and 46d, the louvers 46g, the vertical member 46j, the louvers 46h, and the vertical member 46i of the front of the grease shield 46.

FIG. 16, which illustrates a vertical sectional view of another embodiment of the present invention, shows the top housing wall 12b, the microwave oven cavity 14, the dome 22, the waveguide 26, the directional rotating antenna 32, and the antenna rotating assembly 36. Specifically, a hexagonal hole 34.4 extends partially into the top center of the capacitive top hat 34a of the probe antenna 34. A hexagonal hole 36d.6 in the antenna cap 36d coincides with the hexagonal hole 34.4 in the probe antenna 34. A motor 60 affixes to the top wall 26a of the waveguide 26 and a dielectric hexagonal shaft 60a extends down through an aperture 26f in the waveguide 26, through the hexagonal hole 36d.6 in the antenna cap 36d, and into the hexagonal hole 34.4 of the probe antenna 34. All other elements correspond to those elements previously described.

FIGS. 10-12 illustrate the antenna assembly 56. The directional rotating antenna 32, in a first bending operation, is formed at a first perpendicular bend having a finite radius at the junction of the supports 32e-32h and the microstrip parallel plate transmission line conductors 32i-32l as illustrated in FIG. 10. The resonating elements 32a-32d integrated and attached to the vertical supports 32e-32h are pushed down through the keyway slots 38h-38k respectively in the antenna rotor 38. Subsequently, a wiping die in a second bending operation bends the resonating elements 32a-32d of the antenna upwardly ninety degrees as illustrated in FIG. 11 forming an opposing second perpendicular bend having a finite radius where the resonating elements 32a-32d are in a plane parallel to the microstrip parallel plate transmission line conductors 32i-32l. The vertical supports 32e-32h are engaged and locked in position in the slots of the keyways 38h-38k of the antenna rotor 38 between the opposing first and second perpendicular bends. The vertical supports 32e-32h longitudinally lie in the slots 38h-38k, and opposing perpendicular bends reside at the top and bottom of the slots 38h-38k. The microstrip parallel plate transmission line conductors 32i-32l reside adjacent the top of the disc 38g of the antenna rotor 38.

FIGS. 5 and 6 illustrate the probe antenna 34 accepted in the axial bearing 36c, the axial bearing 36c axially supported on the bushing 36a with the washer 36b in between the components 36a and 36c, and the antenna 32 affixed to the probe antenna 34 with the nut 34.3. The antenna cap 36d frictionally engages over the outer diameter of the axial bearing 36c with the lock tabs 36d.2-36d.5 to provide a dielectric insulation between the probe antenna 34 and the waveguide 26.

FIGS. 6-9 illustrate mounting of the antenna assembly 56 in the top wall 22d of the dome 22 in the microwave oven cavity 14. FIG. 7 illustrates pushing the antenna assembly 56 up through the aperture 22g in the top wall 22d of the dome 22 in the microwave oven cavity 14a. FIG. 8 illustrates turning the antenna assembly 56 in a counterclockwise position to lock the keys 36a.10-36a.12 in position over the teeth 22f.1-22f.3 in the top wall 22d of the dome 22 in the microwave oven cavity 14. FIG. 9 illustrates a perspective view of the keys 36a.10-36a.12 locked over and engaged with the teeth 22f.1-22f.3. The rotational motion of FIGS. 7-9 is accomplished by inserting the member 54a and 54b of the tool 54 through the holes 32o and 32p in the parallel plate transmission line conductors 32i and 32k of the antenna 32, and up into the holes 36a.24 and 36a.25 in the bushing 36a. This provides simultaneous engagement of the bushing 36 and the antenna 32 having the antenna rotor supported on the antenna 32 to permit installation of the antenna assembly 56 in the top wall 22d of the dome 22 in the microwave oven of FIGS. 7-9 by a qualified serviceman having the proper tool 54 and knowledge of servicing techniques. Removal of the antenna assembly 32 is accomplished in the reverse manner of FIGS. 9-7 respectively.

FIG. 4 illustrates the directional rotating antenna 32 rotating about the vertical axis of the dome 22 of the top wall of the microwave oven cavity 14. The grease shield 46 of the figures directs the air in a clockwise rotational flow to rotate the antenna 32 about the center axis of the microwave oven cavity 14 uniformly distributing microwave energy within the confines of the conductive microwave oven cavity 14.

The air flow velocity path through the microwave oven 10 is best illustrated by referencing FIGS. 3, 13-15 and 2 in the respective order.

FIG. 3 illustrates the blower 40 which brings air in through a plurality of holes not illustrated in the bottom housing base of the microwave oven 10, up past the right side of the oven housing 12c, past the rectifier, past the transformer, past control circuitry for the power supply, up through the blower 40, through the heat dissipating plates of the microwave power source 28, up through the rear vent holes 42a and 42b, through the rear of the oven along the longitudinally extending member 48, and subsequently down into the microwave oven cavity 14 through the vent holes 42a and 42b between the top wall 14a of the microwave oven cavity 14 and the grease shield 46. The directional vanes 46a, 46b, and 46c of FIG. 13 direct the air flow in a clockwise rotational manner about the antenna rotor 38 thereby rotating the antenna 32 and the probe antenna 34 axially on the bushing 36a. The flow of air as shown in FIGS. 13, 14 and 15 then travels down through the louvers 46e-46g in the grease shield 46 which produces a path of travel across the door 16. Air also flows out through the holes 52. The air in the microwave oven cavity 14 travels across the door 16, up through the longitudinal louvers 46h, in between the edge of the grease shield 46i and the upwardly extending perforated exhaust panel 14a.2, and out through the plurality of holes 52 to be exhausted out through the front exhaust vent 20 illustrated in FIG. 2. Significantly, the moisture and vapor in the air does not travel past any moving components in the top of the microwave oven and is exhausted out through sheet metal ducting between the top of the housing 12b and the top wall 14a of the microwave oven. The air travel path provides a clean smooth air flow path having least resistance permitting a minimal size of blower motor.

The directional rotating antenna 32 axially can rotate in the range of 25-250 revolutions per minute and preferably in the range of 40-90 revolutions per minute. The air flow velocity and volume of air is predetermined and a function of the blower motor 40 to obtain the predetermined revolutions per minute. Any back pressure of air between the microwave oven cavity 14 and the grease shield 46 is vented through the holes 50 in the top wall 14a.

FIG. 16 illustrates another embodiment of rotating the directional rotating antenna 32 with the motor 60 in lieu of utilizing air flow velocity through the grease shield 46 as illustrated in FIG. 14.

Various modifications can be made to the microwave oven 10 of the present invention without departing from the apparent scope thereof. The antenna rotating assembly 36 can be utilized in any microwave oven and can axially support any directional rotating antenna 32. The antenna rotor 38 can accept any directional rotating antenna with suitable and corresponding geometrical and angular positioning of the plurality keyway slots.