Electric heating – Microwave heating – With diverse-type heating
Reexamination Certificate
1999-04-16
2001-04-17
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With diverse-type heating
C219S752000, C219S400000, C219S756000, C219S754000, C099S474000, C099S479000, C126S02100R
Reexamination Certificate
active
06218650
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heating apparatus, and more particularly to a high speed oven having a turntable mechanism, for heating food products to be cooked by utilizing a combination of impingement of heated air (a jet impingement) and microwaves or either of them, the heating apparatus comprising a safety device and an exhaust system.
DESCRIPTION OF THE PRIOR ART
Though attempts have been made in the past to improve the cooking oven, there still remains a lot of problems to be solved. Regarding the cooking oven, in particular one for use both in business and in homes, there has been a strong demand for a cooking apparatus which enables the time needed for cooking to be shortened and maintains and improves delicate cooking qualities of baked products, such as temperature, baking color, flavor, smell, and so on.
A microwave oven utilizing inductive heating generated by a microwave can raise the temperature inside the food products in a short time, so that the time needed for cooking can be shortened. However, the cooking qualities, such as finish, baking color, flavor, and smell of the food products are not good. Accordingly, the microwave oven may, in practice, be regularly used for re-heating and thawing of the food products, but only rarely used for the final cooking stage of the baked products.
To overcome the above drawback in the microwave oven, there is an oven in which inside heating and surface heating are combined, that is, while the inside of the food is heated with microwaves, its surface is heated by air convection at a high temperature and radiation of infrared rays, the oven further comprising a turntable mechanism on which the food product can be mounted, so that it can be heated more uniformly. However, the balance of the cooking finish of the food product may be lost, because the velocity needed to accomplish the inside heating with microwaves is slower than that needed to accomplish the surface heating. As a result, if a heating velocity is adjusted to the cooking finish for the surface heating, the inside of the food will be heated too much, and thus the food may be too tough and savory water and juice will be removed from the food. As a result, the time needed for cooking will not be shortened very much. On the other hand, if the heating velocity is adjusted to the time needed for raising the temperature of the inside of food product, all of the surface may not be sufficiently heated. Thus, although the cooking time can be made shorter, the quality of the food can not be maintained.
To solve these above problems, Mr. Donald Paul Smith, an American, invented an apparatus in which air at a high temperature is ejected from a plurality of small holes separated from each other to impinge the air onto the upper and lower surfaces of the food product, so that the surfaces can be heated at a rate two or four times faster than a conventionally used forced convection heat transfer apparatus, it being possible for the apparatus to utilize microwaves for the inside heating of the food product (U.S. Pat. No. 3,884,213). The heating principle and method invented by Mr. Smith are very effective, enabling the time needed for cooking to be shortened and cooking quality to be improved. However, such an apparatus having, in practice, the above benefits has not yet appeared in the market.
The reason for this is as follows. Although the above apparatus can be used as an apparatus for all baking dishes for all the dry-types of heating, such as baking, boiling, barbecuing, griddling, roasting, and fry cooking not using oil, oils and juices might be dispersed in the oven at the time of cooking depending on the kind of cooking method and the food product to be cooked. As a result, these oils and juices would be baked, carbonized and finally accumulated on wall surfaces and many portions in the oven due to the high temperature. This would cause many troubles, for example, a locking of the removable portions in the oven and a local heating resulting from a generation of microwave sparks. Accordingly, the level of the cleaning performance on the inside of the oven is very important for the above type of oven. However, even if the cleaning performance of the apparatus is improved, providing of such elements as the jet impingement mechanism, a microwave mechanism and a turntable makes the structure of the apparatus complicated, thus making the cleaning performance ineffective. Accordingly, such an apparatus as that of the present invention has been desired.
In almost all of the prior ovens each comprising a turntable, a driving device is mounted on the backside of the bottom surface of the heating chamber, the axis of which device penetrates the bottom surface of the heating chamber. In such apparatuses as above constructed, since the driving device might be immersed into oil and cleaning fluid via its axis receptor, significant disadvantages, such as a sufficient cleaning operation of the apparatus utilizing water and a chemical cleaning agent is made impossible; the axis is caused to be locked; and a failure in the driving device is made to occur, would be caused. To overcome these problems, it has been desired that a method and an apparatus as used in the present invention be provided, in which method, the driving device for the turntable is not positioned at the bottom surface of the heating chamber, and which apparatus can be disassembled for ordinary cleaning and operates perfectly.
A most typical turntable has an entirely flat form, and is supported by a rotational axis at the center thereof. The turntable itself has a latticed construction so that the food products can be effectively impinged on by the jet of heated air and microwaves. However, the area around the center of the turntable cannot be sufficiently heated due to the lack of the heating by the impingement of the heated air jet and the microwaves.
Accordingly, there has been provided a prior art apparatus having a heating mechanism made more effective due to its improved turntable mechanism, in which apparatus, for example, a turntable has an opening at the central part thereof and is supported by four roller legs. These legs are positioned at periphery portions of the turntable. In such a structure, the problem of the previously mentioned prior art has been overcome by means of supporting the turntable at the periphery portions thereof, so that the heated air and microwaves can impinge on the area about the center of the turntable. In such a structure, however, since the rotation of the turntable is allowed by means of the engagement between the supporting rollers and the outer periphery of the turntable, a new problem might arise when the engagement is made ineffective by imposing an eccentric load on the turntable, thereby causing a failure of the engagement. Thus, another new problem, namely, the turntable cannot rotate smoothly, arises. Accordingly, it is desirable to provide a structure whose heating mechanism has been improved, without, as a result, the turntable rotation being hindered.
In connection with the rotation of the turntable, it is necessary to consider the overloading problem caused at the time the turntable rotates. Since the turntable is constructed to be rotated by rotation torque transmitted to the turntable, which torque is generated by a motor positioned at the outside of the oven, it sometimes happens that large overload is applied to the driving motor due to a locking of the rotating axis which is caused by contaminants attached to the axis, or an obstruction to the turntable rotation which is caused by contaminants interposed between the turntable and, for instance, an inside wall of the oven, such an interposition being possibly caused by, for example, any incorrect management. There is a method of stopping the motor as a way to protect the driving motor from having such an overload applied thereto, in which method an electric current value (electric signals) in the motor is detected or an increase in the temperature in the motor is detected, so as to
Matsuo Hiroshi
Tsukamoto Hideki
Ueoka Akio
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Fujimak Corporation
Leung Philip H.
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