Drying and gas or vapor contact with solids – Apparatus – Vacuum
Reexamination Certificate
2000-10-19
2001-11-20
Walberg, Teresa (Department: 3742)
Drying and gas or vapor contact with solids
Apparatus
Vacuum
Reexamination Certificate
active
06317997
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a vacuum drying system with improved vacuum draw positioning relative to the load, more particularly to a radio frequency (RF) vacuum drying (RFVD) system incorporating improved vacuum draw positioning relative to the load.
BACKGROUND OF THE INVENTION
Dielectric 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, and other industries. One of the key industries using these dielectric 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 drying is to be performed.
In dielectric drying systems (particularly those for drying wood of the type described in U.S. Pat. No. 3,968,268 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 to a grounding electrode to complete the circuit is 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 RF power (energy) to the load through the power electrode(s). In the arrangement shown in this patent, two vacuum draw headers are provided through the top of the kiln with one adjacent to each longitudinal end of the kiln.
WO 99/18401 published Apr. 15, 1999 inventor Wolf discloses a kiln with vertical electrodes similar to Koppelman and once Wolf draws the chamber down to the operating pressure used for drying, he applies vacuum at a single point on the side of the load positioned behind one of the electrodes.
Japanese patent JP4121578 published Apr. 22 1992 inventor Nishihama also discloses the use of vacuum connections one through the roof and a second through the floor, the one through the floor is referred to as sucking a part of the drain from the bottom.
In dielectric drying systems of which the Applicants are aware in the wood products industry, vacuum is drawn from one or two vacuum headers, positioned on top of the chamber (see for example the vacuum headers described in the above Koppelman patent). The belief in the industry prior to the present invention was that vacuum draw location from the chamber was irrelevant to the operation of dielectric vacuum drying processes such as radio frequency vacuum drying (RFVD).
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to provide an improved dielectric vacuum drying system that attains more uniform drying of the product being dried.
More specifically, it is an object to provide a vacuum draw system to improve the drying uniformity of the dried product.
Broadly, the present invention relates to vacuum drying system comprising a sealable drying chamber, vacuum draw means for withdrawing gases and vapors from said drying chamber during drying a load, the improvement comprising at least two vacuum draw outlet headers composed of an upper outlet header positioned to withdraw said gases and vapors preferentially from above a substantially horizontal medial plane of said load in drying position in said chamber and at least one lower outlet header positioned to withdraw said gases and vapors preferentially from below said medial plane of said load, said lower header being positioned above the a bottom of said drying chamber.
Preferably vacuum drying system is a dielectric and includes a pair of horizontal opposed electrodes for applying dielectric power to said load.
Preferably, said system is constructed so that said upper vacuum outlet header draws more gases from said drying chamber than said lower vacuum outlet header.
Preferably each said outlet header extends at least along 20% of a longitudinal length of said electrodes.
Preferably each said header extends along at least 70% of said longitudinal length of said electrodes.
Preferably at least two vacuum draw outlets comprise a first pair of said upper and lower outlet headers on one longitudinal side of said load and a second pair of said upper and lower outlet headers on a second longitudinal side of load opposite said first longitudinal side.
Preferably each said upper outlet is positioned within an upper third of a distance separating said electrodes when said electrodes are in operative position for drying said load and each said lower outlet headers are positioned within a lower third of said distance separating said electrodes when said electrodes are in operative position.
Preferably said upper and lower vacuum outlet headers are symmetrically positioned relative to the center of said load.
Preferably said dielectric vacuum drying comprises radio frequency vacuum drying (RFVD).
REFERENCES:
patent: 1672326 (1928-06-01), Kobiole
patent: 3283412 (1966-11-01), Farnsworth
patent: 3574949 (1971-04-01), Farnsworth
patent: 3986268 (1976-10-01), Koppelman
patent: 4194296 (1980-03-01), Pagnozzi et al.
patent: 4343095 (1982-08-01), Rosen et al.
patent: 4466198 (1984-08-01), Doll
patent: 5228209 (1993-07-01), Brunner
patent: 4121578 (1992-04-01), None
patent: WO99/18401 (1999-04-01), None
Kooznetsoff Gary Kenneth
Zwick Robert Lewis
HeatWave Drying Systems Ltd
Patel Vinod D.
Rowley C. A.
Walberg Teresa
LandOfFree
Vacuum port positioning for vacuum drying systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum port positioning for vacuum drying systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum port positioning for vacuum drying systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590924