Electric heating – Metal heating – Of cylinders
Patent
1980-11-25
1984-09-11
Reynolds, B. A.
Electric heating
Metal heating
Of cylinders
34 1, 219 1055R, F26B 2308, H05B 664
Patent
active
044711921
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
This invention relates to a microwave heating apparatus which is effective not only as a common heating apparatus but also especially as a heating apparatus of a freeze-drying apparatus or a vacuum-drying apparatus for foodstuff.
BACKGROUND ART
Freeze-drying or vacuum-drying for foodstuff can provide a produce more excellent in quality than that by normal pressure heat drying, and therefore is used reputably as a means of process for preservation foodstuffs or space foodstuffs. However, there has been adopted in that process a surface heat drying system by a radiant heat source, so that if the radiant heat thereof is increased in thermal volume in order to shorten the drying time, the surface temperature of the foodstuff is raised to excess and cells of the foodstuff are dried hard or tissue thereof is damaged, and as a result the foodstuff is changed in color or flavor. Accordingly, it has been necessary to take the drying time of 6-10 hours for obtaining a food product good in quality.
In view of this, the inventors of the present invention have previously succeeded in shortening the drying time by using a microwave heating apparatus capable of heating a material to be heated from the central portion thereof, jointly with a radiant heat source. However, the conventional microwave heating apparatus is so arranged that an electric wave may radiate onto a material to be heated substantially perpendicularly thereto, so that there is involved such an inconvenience that an electric wave transmission distance through the material to be heated is short and the heating energy thereof is not effectively consumed. Additionally, the same has to provide in a heating chamber a heat generating plate or the like serving as a radiant heat source, so that there is involved such an inconvenience that an effectively available space in the heating chamber is small.
DISCLOSURE OF THE INVENTION
This invention has for its object to provide a microwave heating apparatus free from those inconveniences, and it is characterized in that a leakage waveguide group is formed by arranging a number of leakage waveguides, each having at least in one side surface thereof an electric wave radiation opening in the form of a long slit or a series of openings spaced one from another (much in the nature of "stepping stones"), and the same is closed at each electric wave radiation opening thereof with heat resistant non-metal material such as Teflon, glass or the like and is so arranged that a heating medium such as hot air, steam or the like may be directed or passed therethrough.
Thus, according to this invention, since the leakage waveguide group is formed by arranging a number of leakage waveguides, each having at least in one side surface thereof an electric wave radiation opening in the form of a long slit or a series of spaced openings, it is advantageous in that there can be removed the foregoing inconveniences with the conventional microwave heating apparatus in which an electric wave is radiated onto the material to be heated substantially perpendicularly thereto, and that the heating speed can be improved as compared with that in the conventional one and the drying time can be shortened.
Additionally, the leakage waveguide group is closed at each electric wave radiation opening thereof with the heat resistant non-metal material such as Teflon, glass or the like and is so arranged that a heating medium such as hot air, steam or the like may be passed therethrough, and thus the leakage waveguide which radiates an electric wave from the electric wave radiation opening thereof is utilized as a thermal radiator, and consequently there can be removed the foregoing inconvenience with the conventional microwave heating apparatus of this kind in which a heat generating plate or the like serving as a radiant heat source is provided in a heating chamber, and thus it is advantageous in that there can be provided such one that an available space in a heating chamber is large, and there can be obtained practica
REFERENCES:
patent: 3056877 (1962-10-01), Schmidt et al.
patent: 3263052 (1966-07-01), Jeppson et al.
patent: 3739130 (1973-06-01), White
patent: 3783221 (1974-01-01), Soulier
Abe Ken-ichi
Awata Hidenori
Harada Masatsune
Shimizu Takehiro
Bloom Leonard
Keve Alfred S.
Osaka Gas Kabushiki Kaisha
Reynolds B. A.
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