Electric heating – Capacitive dielectric heating – Specific electrode configuration
Reexamination Certificate
2000-07-07
2001-05-01
Leung, Philip H. (Department: 3742)
Electric heating
Capacitive dielectric heating
Specific electrode configuration
C219S773000, C219S774000, C034S250000
Reexamination Certificate
active
06225612
ABSTRACT:
FIELD OF INVENTION
The present invention relates to radio frequency (RF) heating and drying systems incorporating improved electrode structures.
BACKGROUND OF THE INVENTION
Dielectric heating/drying systems are known and are currently in use or have been proposed for use in agriculture, polymer manufacture, pharmaceuticals, bulk powder, food processing, wood products, building materials, and other industries. One of the key industries using these dielectric heating/drying systems is the wood products industry and the present invention will be described particularly with respect to the wood products industry although the invention, with suitable modifications where required, may be applied in the other industries in which dielectric heating/drying is to be performed.
In dielectric drying systems (particularly those for drying wood of the type described in U.S. Pat. No. 3,986,268 issued Oct. 19, 1976 to Koppelman), it is conventional practice for the lumber to be moved into the drying chamber, at least one power electrode that will emit electromagnetic energy and a grounding electrode to complete the circuit are positioned near or in contact with the load. After the load has been positioned in the kiln, the kiln chamber is closed and the drying process is commenced by applying a negative pressure in the chamber and applying power (energy) to the load through the power and grounding electrodes. U.S. Pat. No. 5,942,146 issued Aug. 24, 1999 to Blaker et al. (the disclosure of which is incorporated herein by reference) teaches that shaping of the electrode connectors, (elements carrying the power to the load) is important and describes the minimum curvature required for improved operation.
The electrodes used in dielectric drying systems generally have a planar surface facing the load. One theoretical system to obtain optimum RF uniformity within the load requires that the power electrode have an infinitely long and infinitely wide planer surface; obviously, this is not practical.
It is Applicant's understanding that an experiment incorporating small wings or flanges at the sides of the electrodes and projecting on opposite sides of the load was previously performed and while an effect was observed the effect was of minimal practical significance in comparison to the Applicant's current invention.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to provide an improved electrode structure to improve the electric field uniformity through the load being heated and/or dried.
Broadly the present invention relates to dielectric heating and/or drying systems comprising a chamber, a pair of opposed electrodes for applying dielectric power to a load contained between said electrodes, each said electrode having a planar electrode surface and at least one of said electrodes having a pair of wings one along each of its side, each of said wings projecting from said planar electrode surface of its electrode toward the opposed electrode of said pair of opposed electrodes, said wing of said pair of wings being laterally spaced so that said wings are positioned adjacent to an adjacent outside side surface of the load when said electrodes are in operative position to apply power to said load.
Preferably said dielectric drying comprises radio frequency drying (RFD).
Preferably said dielectric drying comprises radio frequency vacuum drying (RFVD).
Preferably each of said wings projects from its electrode planar surfaces by a distance d in the range of 26 cm to 40 cm and preferably in the range of between 29 and 36 cm.
Preferably said wings are symmetrically positioned relative to axial ends of said electrode planar surface and extend at least 80% of an axial length LE of said planar surface.
REFERENCES:
patent: 2532460 (1950-12-01), Phillips, Jr.
patent: 3986268 (1976-10-01), Koppelman
patent: 4398816 (1983-08-01), Krishnakumar et al.
patent: 5942146 (1999-08-01), Blaker et al.
patent: 6030490 (2000-02-01), Francisco et al.
patent: 6080978 (2000-06-01), Blaker et al.
Exerp from Main COFI Report. (No Date).
HeatWave Drying Systems Ltd.
Leung Philip H.
Rowley C. A.
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