Electric heating – Microwave heating – Waveguide applicator
Reexamination Certificate
2000-10-03
2004-02-17
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
Waveguide applicator
C219S697000, C219S748000, C219S750000
Reexamination Certificate
active
06693266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a heating apparatus and a method of heating objects inside an oven using microwaves in order to carry out drying, warming, thawing, cooking, roasting, sterilizing, concentrating and the like.
2. Description of the Prior Art
In the case were objects are heated using microwaves, when microwaves emitted from a magnetron are passed through a waveguide and introduced inside a tank, a portion of such introduced microwaves form reflected waves which travel in the opposite direction and return to the magnetron, thereby creating an energy loss and damaging the magnetron due to the heat generated by such reflected microwaves. Prior art technology for preventing this includes mounting a matching device midway in the waveguide to match the microwaves in order to reduce reflected waves, and mounting an isolator near the microwave generator to absorb and eliminate reflected waves.
Further, a stirrer is generally mounted inside the oven to disperse the microwaves in order to achieve matching.
Further, in the case where a plurality of microwave introduction ports are provided in the oven, these microwave introduction ports are arranged away from mutually opposing positions to prevent increased reflected waves and mutual interference of the microwaves introduced through such introduction ports, and in the case of rectangular microwave introduction ports, if a horizontal arrangement is used on one side, a vertical arrangement can be used on the opposite side away from opposing positions.
However, the isolator and matching device used in the prior art are extremely expensive and form the main cause of high costs introduced when the microwave generator is to be used a lot for industrial applications, and for this reason the use of such high value-added energy microwaves has been limited.
Further, a stirrer is generally provided to disperse the microwaves inside the oven in order to achieve uniform heating, but because this requires a significant mounting space for holding the rotation axle for the rotor and the motor required for the stirrer, it is impossible to provide a large number of microwave introduction ports, and this makes it difficult to achieve uniform heating by means of a plurality of microwave introduction ports. Further, because the incident waves interfere with each other and become dispersed while the stirrer is rotating, a fluctuating increase and decrease in reflected waves normally appears, and this has made it difficult to achieve a stable reduction in reflected waves.
Further, in the case where a plurality of microwave introduction ports are provided in the oven, when these microwave introduction ports are arranged at positions away from opposing positions, minute changes in position can have subtle adverse effects on uniform heating and matching, and this has created problems for heating matching and made it impossible to achieve a sufficient reduction in reflected waves. In particular, this problem is striking in the case where the object being heated is fixed in place.
SUMMARY OF THE INVENTION
First, the waveguide connected to the oven is shaped so to not hinder the propagation of microwaves incident toward the oven, namely, the waveguide is shaped so that the cross-sectional area of the port portion of the waveguide at the oven side is greater than the cross-sectional area at the microwave generator side. Namely, the cross-sectional area of the waveguide gradually expands from the microwave generator side toward the oven side to give the waveguide a horn shape, and a prescribed size cone-shaped, pyramid-shaped, bell-shaped or other similarly shaped reflector apparatus is provided at a prescribed position inside the waveguide with the bottom of the reflector apparatus facing the oven side to form a structure which does not hinder the propagation of incident microwaves from the microwave generator toward the oven. With this structure, most of the reflected microwaves heading toward the waveguide from the oven will be reflected again by the bottom of the reflector apparatus and returned to the inside of the oven, and this significantly reduces the reflected microwaves traveling back toward the microwave generator.
Further, if a straight tube made of metal is provided between the waveguide and the microwave introduction port of the oven, the incident microwaves passing through the straight tube will make it possible to improve the heating matching, and this further reduces the reflected microwaves. In this case, the straight tube has a prescribed length and both ports thereof have the same size and shape as the oven-side port portion of the waveguide.
Next, if the stirrer of the prior art is replaced with a fixed metal reflection diffusion apparatus provided in the oven at a position in front of the microwave introduction port of the oven at a prescribed distance from the microwave introduction port, the microwaves incident into the oven will undergo reflection diffusion, and this makes it possible to achieve highly uniform heating. Also, the use of an appropriately sized reflection diffusion apparatus at an appropriate position facilitates heating matching and reduces reflected waves. Further, because the reflection diffusion apparatus is compact, the use thereof makes it possible to provide many microwave introduction ports, thereby making it possible to improve heating matching. Moreover, the use of the reflection diffusion apparatus prevents the reflected energy fluctuations that occur for the rotational dispersion carried out by a stirrer, and this contributes to reducing reflected waves.
Further, by providing the oven with a plurality of microwave introduction ports arranged at opposing positions, it is possible to carry out fine matching and achieve highly accurate uniform heating. In the case where the microwave introduction ports are arranged at opposing positions, because the microwaves propagate toward opposing microwave introduction portions, there is generally an increase in reflected waves which results in a loss of heating matching. However, this problem is eliminated by the waveguide provided with a reflector apparatus, and the reflection diffusion apparatus, which make is possible to significantly reduce reflected waves and significantly improve heating matching.
Namely, the method of heating objects with microwaves according to the present invention involves passing microwaves emitted from a microwave generator toward an oven through a propagation path shaped so as to not hinder the propagation of microwaves incident toward the oven, and shaped so to make the cross-sectional area of the oven side port portion of the propagation path larger than the cross-sectional area of the microwave generator side port portion of the propagation path, with a microwave reflector apparatus being provided at a prescribed position inside the propagation path to reflect most of the reflected microwaves from the oven heading toward the microwave generator back into the oven in order to reduce reflected waves and facilitate heating matching.
Further, the microwave heating method may further comprise the step of passing the microwaves incident toward the oven through a straight metal tube having a prescribed length and port portions having the same size and shape as the oven side port portion of the propagation path in order to reduce reflected waves and facilitate heating matching.
Another method of heating objects with microwaves according to the present invention involves passing microwaves emitted from a microwave generator through a microwave introduction port into an oven provided with a metal reflection diffusion apparatus arranged at a prescribed position in front of the microwave introduction port at a prescribed distance therefrom, whereby a prescribed ratio of the microwaves incident into the oven undergo reflection diffusion, wherein the major portion of the reflection diffused microwaves are directed away from the position of the reflection diffusion apparatus toward the insid
Hedman & Costigan ,P.C.
Leung Philip H.
LandOfFree
Microwave heating apparatus and method of heating objects does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microwave heating apparatus and method of heating objects, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microwave heating apparatus and method of heating objects will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3305884