A portable microwave oven

Abstract: A portable microwave oven includes: electrical components (4) for generating microwaves; a heating chamber (18) for food (13) to be heat cooked; and a door (1) for allowing food (13) to be put in and taken out from the heating chamber (18). The door (1) incorporates a microwave stirrer (12) for agitating microwaves. When food (139 is heated, the user takes the tray (26) out from the heating chamber (18) so as to place food (13) and then can easily put the food together with the tray (26) by holding the handle (27) of the tray (26). Similarly, when food (13) is taken out, it is taken out together with the tray (26).

Description: The present invention relates to a portable microwave oven, and particularly, although not exclusively to portable microwave ovens which can be carried outdoors. Conventionally, microwave ovens of a home-use counter top type have been prevalent on the market and occupy a suitable area in kitchens. In recent years, however, with drastic expansion of the automobile industry as well as the outdoor leisure industry, there have been demands for microwave ovens for cooking outdoors under the tendency to seek various leisure-oriented lives. In response to this tendency, portable microwave ovens of a light-weight type which can be carried outdoors with ease have been developed. In general, microwave ovens have a turntable which turns food or a metal-made agitator for agitating microwaves in the power feeding portion of microwaves to the heating chamber letting the food stand still, so that microwaves will uniformly heat food when it is heated. However, when these methods are applied to portable microwave ovens, it is necessary to ensure a heating chamber having some degree of volume, unavoidably increasing the apparatus size. Conversely, when the body is reduced in size, there is no space for equipment of the means for uniformly heating food, producing a problem of large uneven distribution during heating. Because of frequent carriage from place to place, this type of microwave oven needs increased strength against vibration. In view of the forgoing, the present invention seeks improvement and/or alternatives to existing microwave ovens. Further, it is desirable to provide a portable microwave oven which can cook food without uneven heat distribution, without increasing the size of the portable microwave oven body and which is improved in strength against vibrations. In addition to the above solution of the conventional problems, it is desirable to provide a portable microwave oven which is improved in user's handling performance, allowing the user to put food into, and take food out of, the heating chamber. According to the present invention there is provided a portable microwave oven as claimed in claim 1. Preferably the portable microwave oven further includes: a cooling fan for cooling the electrical components; and a motor for rotating the cooling fan. It is preferred that the air flow generated by the rotation of the cooling fan driven by the motor is used to rotate the microwave stirrer. Preferably the portable microwave oven is arranged such that the air flow which has rotated the microwave stirrer is conducted into the heating chamber through an air duct which is preferably formed in a cover provided for the door so as to preferably wrap around the microwave stirrer and is discharged from the heating chamber to the exterior thereof, preferably together with steam generated from heated food. Preferably the cover has an air guide which directs the air flow to allow the microwave stirrer to rotate smoothly. Preferably the microwave stirrer is supported by a bearing which comprises a pair of sockets disposed above and below the microwave stirrer. In order that the present invention be more readily understood, embodiments thereof will now be described with reference to the accompanying drawings, in which: Figs. 1A and 1B are views showing the appearance of an embodiment of a portable microwave oven, Figs. 1A and 1B being top and side views, respectively; Fig. 2 is a sectional view showing electrical components accommodated inside the portable microwave oven shown in Figs. 1A and 1B; Fig. 3 is a partial sectional view showing the portable microwave oven shown in Figs. 1A and 1B; and Fig. 4 is an enlarged view showing bearings disposed above and below a microwave stirrer; As shown in Figs. 1A and 1B, a door 1 for allowing food to be put in and taken out therethrough as well as shielding radiation of microwaves is provided on the top of the portable microwave oven. This door can pivot so that it can open and be closed. Door 1 has a door panel 2 made of metal for shielding radiation of microwaves, a door frame 3 made of plastic constituting the outer covering, and a latch mechanism for locking door 1. Referring to Fig. 2, when a motor 7 is driven, a cooling fan 8 that is fixed to the shaft of motor 7 starts to rotate. This rotation of cooling fan 8 sucks air from and air suction port and part of the air is conducted to cool the electrical components for generating microwaves, including a magnetron 4, a high-voltage transformer 5, a high-voltage capacitor 6 etc., and is discharged from a discharging port. Part of the air flow generated by the rotation of cooling fan 8 is conducted through a heating chamber suction port 10 on the side surface of a control panel 9 and a suction port 11 provided on the door 1 shown in Fig. 2 so as to rotate a microwave stirrer 12 for agitating microwaves. This microwave stirrer 12 is made up of a light-weighted, microwave-reflective metal material such as aluminium etc. Microwave stirrer 12 is composed of a disc-like flat branching portion 12a by which is meant a substantially flat and substantially disc shaped member. Said member having amorphous holes therein, a fin portion 12b having bends angled at approximately 90 degrees on the periphery of flate branching portion 12a and a bearing 12c serving as supports and a rotational center of microwave stirrer 12. The air flow from cooling fan 7 hits fin portion 12b so as to generate torque for rotating microwave stirrer 12. Provided for door 1 is a cover 14 which covers microwave stirrer 12. This cover has an air guide 19 along fin portion 12b, as shown in Figs. 1A and 1B so that the air flow will transmit torque to fin portion 12b more efficiently. In this way, food 13 can be uniformly heated avoiding uneven heating. Since microwave stirrer 12 is arranged in the draw-formed portion of door panel 2, this configuration enables uniform heating of food without either increasing the microwave oven body in its size or reducing the effective dimensions of heating chamber 18. Conventionally, home-use microwave ovens usually have a door with a screen window. On the other hand, since portable microwave ovens are inherently designed to be compact, they generally have no window (view-finder) in door 1. It is further reasoned that a portable microwave oven is often used in light filled places other than home kitchen and if a view-finder is provided, the range of the view-finder is small and cannot give a good interior view because the surrounding is too bright. Therefore, there is nothing to obstruct the use of microwave stirrer 12 being arranged in the center of door panel 2. The air flow which has turned microwave stirrer 12 is sent, as shown in Fig.3, into heating chamber 18 through an air duct 15 formed in cover 14, which is provided for door 1 in order to prevent the user from touching microwave stirrer 12 when cleaning or the like. The thus supplied air to the heating chamber is discharged from a discharging port 16 provided in heating chamber 18, capturing steam generated from food during heating. Since steam is discharged in the above manner, heating chamber 18 does not need to have a dedicated air duct (such as punched holes etc.) for feeding air into heating chamber 18, thus making it possible to simplify the die and reduce the number of steps for manufacturing. A pair of shafts 17 for supporting microwave stirrer 12 are provided, one fixed on the top surface of cover 14 and the other on the inner side of door panel 2, while bearing 12c of microwave stirrer 12 has a pair of sockets above and below as shown in Fig.4. This structure protects removal of microwave stirrer 12 from shafts 17 during hand carriage or transportation by car. Bearing 12c is made up of a plastic material having a low frictional coefficient, such polytetrafluoroethylene (Teflon ) in order to permit smooth rotation. Cover 14 is formed of a plastic material having a low induction ratio such as polypropylene. Fig.6 is a perspective view showing tray 26 having handles 27 attached thereto. Tray 26 has a flat portion 26a having a rectangular shape. The pair of handles 27a and 27b are engaged with tray 26 at pins 26c so that they can rotate 180 degrees with respect to the tray. Flat portion 26a is marginally smaller than the bottom face of heating chamber 24. Food 13 is placed on flat portion 26a. An outer rim 26b is provided around the periphery of flat portion 26a. This outer rim 26b is provided to prevent drips or food crumbs from directly dropping to the bottom of heating chamber 24, trying to improve cleanability of heating chamber 24. Tray 26 and handles 27 are formed of plastic molding, which is light, since they are equipped in a portable microwave oven. The top faces of handles 27 are designed to be as high as the top plane of heating chamber 24 so that they will be in contact with the door panel when door 1 is closed. When the microwave oven body is carried, it is held by a carrying handle 28. Therefore, control panel 9 is oriented downward. Handles 27 provided for tray 26 are made in close contact with door 1 as shown in Fig.6, whereby it is possible to transport the oven with the tray being unchattered and fixed therein. Figs.7A and 7B show two states of tray 26 where handles 27 are rotated 180 degrees from one state to the other. Provided at each of the four corners of rectangular tray 26 is a leg structure 29 which has two different-sized legs 29a and 29b formed integrally extending opposite to each other (see Fig.6). Pin 26c serving as a rotational center of handle 27 is provided at a point positioned at half the height of leg structure 29 and half the length B which is the width of handle 27 minus the wall thickness of its outer rim. In Fig.7A, the outer rim 26b of tray 26 functions as the stopper for handle 27 so as to prevent the handle from falling inward to heating chamber 24. On the other hand, in Fig.7B, the end face 26d of outer rim 26b of tray 26 functions as the stopper for handle 27 so as to prevent the handle from falling inward to heating chamber 24. In this way, handles 27 are assembled to leg structures 29 which each have two different height legs projected from tray 26, at the predetermined positions so that they can pivotally move at the outer periphery of tray 26. With this structure, the plate face of tray 26 is reversed when handles 27 are rotated 180 degrees, so that it is possible to change the height of the drip plate surface on which food is placed in tray 26, which allows the user to select the height of tray 26. Further, the manufacturer can indicate the height of tray 26 in accordance with the type of food so that the food may be heated uniformly. As a result, when the user selects the lower height of tray 26, it is possible to put taller food in heating chamber 24. Conversely, when the user selects the upper height of tray 26, food can be placed in a shallow position inside heating chamber 24 and hence food can be readily put in and taken out directly without putting in and taking out tray 26. Since the rotational axle of handle 27 is disposed at the vertical center of leg structure 29 having different-sized legs, handles 27 will abut door 1 in either case, where tray 26 is placed at the upper position and where it is placed at the lower position. This means that tray 26 can always be tightly held inside heating chamber 24. Also for the packaging step at the production line, this configuration lends itself to omitting the stuffing for fixing tray 26 and hence results in reduction in cost. Figs.8A and 8B are partial sectional views showing another embodiment of a portable microwave oven in accordance with the invention, where handles 27 and tray 26 can be assembled and disassembled. Specifically, as shown in Figs.8A and 8B, a plurality of indentations 111 are formed in handle 27. In this structure, the position of tray 26 can be adjusted to several levels of height in accordance with the number of indentations 111. Further, whichever height is selected, handles 27 abut door 1 (door panel 2) so that tray 26 will not chatter as in the above As will be seen from the foregoing embodiments a microwave stirrer for agitating microwaves is provided in the door for allowing food to be put in and taken out therethrough, it is possible to uniformly heat food, assuring an effective size for the heating chamber without enlarging the outside dimensions of microwave oven body. The embodiment allows the air flow generated by the rotation of the cooling fan to drive the microwave stirrer, and hence turn the microwave stirrer without increasing the number of parts such as a motor etc. for driving a microwave agitator. Also disclosed in the described embodiment is a microwave oven which allows the air flow which has turned the microwave stirrer to be introduced into the heating chamber through an air duct provided for the cover, without being discharged directly. Therefore it is possible to simplify the exhaust system. Further, since an air duct is provided for the cover, no duct for air to be injected into the heating chamber needs to be provided for in the wall of the heating chamber, and thus it is possible to simplify the die for producing the heating chamber and hence reduce the number of the production steps. In accordance with the portable microwave oven having the above fourth feature, since an air guide is provided in the cover, it is possible to guide air flow to smoothly rotate the microwave stirrer. Further, this structure improves the strength of the cover, resulting in improvement in quality. In accordance with the portable microwave oven having the above fifth through eighth features, since the bearing has a pair of sockets above and below for supporting the microwave stirrer, rotational vibrations of the microwave stirrer can be eliminated. Further, this configuration is strongly resistant to vibrations during transportation. chattered during carriage or transportation of the portable microwave oven. Also in the packaging step at the production line, this configuration lends itself to omitting the stuffing for fixing the tray and hence results in reduction in cost. In accordance with the portable microwave oven having the above eleventh and twelfth features, since the handles can be rotated 180 degrees relative to the tray, it is possible to change the height of the tray on which food is placed and hence it becomes possible to heat food uniformly in a more spatial manner compared to typical configurations in which food is uniformly heated in a planar manner using a turntable or stirrer fan. For example, popcorn is well cooked when it is placed away from the wall surface of the heating chamber by setting the tray may at the higher position. Alternatively, the tray is set at the lower position for a more usual menu so as to use large space. In this way, this configuration allows the selection of optimal cooking conditions in accordance with the food. In accordance with the portable microwave oven having the above thirteenth and fourteenth features, the pivot axles of the pivotable handles attached to the tray are positioned at the vertical center, equi-distant from two ends of the leg structure having different-sized legs which project above and below near the periphery of the tray. By this configuration, either when the tray surface is set at the higher position or when the tray surface is set at the lower position, the handles can be abutted against the door, thus the tray can always be fixed tightly during carriage or transportation. Also in the packaging step at the production line, this configuration lends itself to omitting the stuffing for fixing the tray and hence results in reduction in cost. In accordance with the portable microwave oven having the above fifteenth and sixteenth features, since a plurality of indentations are formed in the handles and the tray can be attached to any one of them, either when the tray surface is set at a higher position or when the tray surface is set at a lower position, the handles can be abutted against the door, thus the tray can always be fixed tightly during carriage or transportation. Also in the packaging step at the production line, this configuration lends itself to omitting the stuffing for fixing the tray and hence results in reduction in cost.

Claims: A portable microwave oven comprising: electrical components for generating microwaves; a heating chamber (18) in which food may be placed to be cooked; a door (1) to allow access to the heating chamber (18) characterized by a microwave stirrer (12) for agitating generated microwaves, said microwave stirrer being connected to the door (1). The portable microwave oven according to claim 1 further comprising: a cooling fan (8) for cooling the electrical components; and a motor (7) for rotating the cooling fan (8) wherein the air flow generated by the rotation of the cooling fan (8) driven by the motor (7) is used to rotate the microwave stirrer (12). The portable microwave oven according to either claim 1 or claim 2 further including a bearing for supporting the microwave stirrer (12), the bearing having a pair of sockets each having an open end facing in opposite directions. The portable microwave oven according to claim 3 further including a shaft (17) fixed on the top surface of a cover (14) and inserted into an open end of one of the sockets and a shaft (17) attached to a side of a door panel (2) and inserted into an open end of the other socket. The portable microwave oven according to any of claims 1 to 4 including a cover associated with the door (1) to wrap around the microwave stirrer (12), said cover comprising an air duct arranged to conduct the air from she heating chamber (18) and the steam generated from the heated food to the exterior of the chamber (18). The portable microwave oven according to claim 5, wherein the cover (14) has an air guide which directs the air flow to allow the microwave stirrer (12) to rotate smoothly. The portable microwave oven according to any of claims 1 to 6 wherein the microwave stirrer (12) comprises a flat disc portion (12a) which has amorphous holes therein.

Inventors: ARAMAKI YOSHIHIRO, FUSHINO KIYOTO, ARAMAKI, YOSHIHIRO, FUSHINO, KIYOTO
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1998
Main classification: H05B6
IPC codes: H05B6