US3461263A - Radio frequency heating apparatus - Google Patents

Description

g- 1969 J. a. D. MANWARING 3,461,263

RADIO FREQUENCY HEATING APPARATUS Filed July 31, 1967 United States Patent 3,461,263 RADIO FREQUENCY HEATING APPARATUS Joshua G. D. Manwaring, Needham, Mass., assignor to Radio Frequency Co., Inc., Medfield, Mass., a corporation of Massachusetts Filed July 31, 1967, Ser. No. 657,294 Int. Cl. H051) 9/04, 9/06, 5/00 US. Cl. 21910.81 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to radio frequency circuitry and components and, more particularly, to radio frequency heating equipment and electrode systems useful therein.

It is a primary object of the present invention to propide an improved, compact, relatively simple and inexpensive, easily cleaned stray field electrode system which can be used for either single or double surface radio frequency heating. Other objects include providing an electrode system which is of simple and rugged construction and which may be readily tuned to accommodate a variety of conditions.

The invention accomplishes these and other objects by providing a stray field electrode system comprising a pair of spaced coplanar conductive plates and a plurality of parallel, conductive electrode elements alternately arranged in two series extending transversely of the plates. Each electrode element of one series comprises a sheet metal member mounted on the first plate electrode and with an edge surface of the member parallel thereto. Each electrode element of the second series is secured to the second plate electrode and includes a rod portion extending transverse, parallel and adjustable relative to the second plate electrode. In preferred embodiments the electrode elements of the second series comprise rods having base portions parallel to and leg portions perpendicular and secured to the second plate electrode, and hairpin tuning loops of conductive sheet metal electrically connect the plate electrodes.

The electrode system provided by the present invention is particularly useful in combination with radio frequency heating apparatus of the type disclosed in my application Ser. No. 570,780, filed Aug. 8, 1966, new Patent No. 3,329,796 dated July 4, 1967, which utilizes a tuned load circuit comprising a generally tubular electrically conductive enclosure, preferably of rectangular cross-section with a pair of opposite ends spaced a substantial distance from one another, with a plate circuit component having its series of plates mounted within the enclosure perpendicular to its walls and extending therealong throughout the length of the enclosure between its open ends. The plate circuit is connected to the enclosure and also to a radio frequency generator for heating material positioned within or without the enclosure.

Other objects, features and advantages will appear from the following detailed description of a preferred embodiment of the invention, taken together with the attached drawings in which:

FIG. 1 is a perspective view of a stray field electrode constructed in accordance with the present invention; and,

FIGS. 2 and 3 are sectional plan views of the electrode in FIG. 1.

Referring more particularly to the drawings, the stray field electrode 10 here illustrated comprises two substantially parallel plate electrodes, 12, 14 spaced one above the other and three tunabe inductive hairpin loops 16 of conductive sheet metal secured to and electrically connecting the plate electrodes. Each hairpin loop 16 in cludes a tuning portion 18 parallel with plate electrodes 12 and 14 and connecting portions 20 and 22 generally perpendicular to the plate electrodes and connected, respectively, to plate electrodes 12 and 14. A shorting member 24 is slideably mounted on the tuning portion 18 each of haidpin loops 16 for tuning.

For producing the stray field, a plurality of elongated, transversely extending, stray field electrode elements are mounted in parallel relationship on each of the plate electrodes on the side thereof, opposite tuning portions 18 of hairpin loops 16. The stray field electrode elements are alternately arranged to form two series, series 26 and series 28. Each electrode element 30 of series 26 comprises a generally planar, conductive sheet metal element mounted on plate electrode in position generally perpendicular and transverse thereto. The upper longitudinal edges 32 of the electrode elements 30 of series 26 lie in a common plane spaced above and parallel to plate electrode 12. Each electrode element of the other series, series 28, comprises a substantial U-shaped conductive rod having a base portion 40 of each rod parallel to plate electrodes 12 and 14 and spaced thereabove and two legs 42, 44 extending perpendicularly and secured by nuts 46 to plate electrode 14. Legs 42 extend through openings 48 in, and legs 44 are spaced beyond the longitudinal edge of, plate electrode 12 so that no portion of the rod electrode elements of series 28 directly contact plate electrode 12. Major portions of each leg 42, 44 are threaded so that the rod electrode elements may be adjusted relative to the plates electrodes. A plurality of insulating support members 50 and 52 extend between and are secured to electrode elements 30 and plate electrode 14, and plate electrode 14 and tuning loops 16, respectively, for rigidity.

In operation, the electrode elements may be mounted with surfaces 27 of the sheet metal elements of series 26 and base portions 40 of the rod elements of series 28 arranged either for heating on one side of of a material passed over the electrodes, as shown in FIG. 2, or as shown in FIG. 3, for heating both sides of material passed between the two series of electrodes. For single side heating (FIG. 2) the rod elements of series 28 are adjusted so that base portions 40 of each rod electrode element lies in thep lane defined by surfaces 27 of the sheet metal electrodes 30 of series 26. For two side material heating (FIG. 3) the base portions 40 of the rod electrodes are adjusted upwardly by means of nuts 46 so that base portions 40 of the rods lie in a second plane substantially parallel with the plane of surfaces 27 of the sheet metal electrodes but spaced thereabove. Material to be heated may be passed between the two planes.

Other embodiments within the scope of the following claims will occur to those skilled in the art.

What is calimed is:

1. A stray field electrode comprising:

first and second parallel, electrically conductive plate electrodes spaced one above the other; and,

a plurality of parallel, conductive electrode elements alternately arranged in two series extending transversely of said plate electrodes,

each electrode of said first series being electrically connected to said first plate electrode and comprising a sheet metal member mounted on said first plate electrode with a longitudinal edge surface of said member parallel thereto,

each electrode of said second series comprising a rod having a base portion generally parallel to said second plate electrode and at least one leg portion generally perpendicular and adjustably secured to said second plate electrode.

2. A stray field electrode comprising:

first and second parallel, electrically conductive plate electrodes spaced one above the other; and

a plurality of parallel conductive electrode elements alternately arranged in two series extending transversely of said plate electrodes,

each electrode of said first series being electrically connected to said first plate electrode and comprising a sheet metal member mounted on said first plate electrode with a longitudinal edge surface of said member parallel thereto,

each electrode of said second series being electrically connected to and including a rod portion parallel and adjustable relative to said second plate electrode and said edge surfaces of said members lying in a common plane substantially parallel with said first plate electrode and said electrodes of said second series being adjustable between a first position in which said rod portions lie in said common plane and a second position in which said rod portions lie in a second plane parallel to and spaced from said common plane. 3. The stray field electrode of claim 2 including a plurality of hairpin loops of conductive sheet metal electrically connected to said plate electrode, a shorting member being slideably mounted on each of said hairpin loops. 4. The stray field electrode of claim 3 in which each of said members is substantially perpendicular to said first plate electrode and each electrode of said second series comprises a rod having a base portion generally parallel to said second plate electrode and two leg porti ons generally perpendicular and adjustably secured to said second plate electrode.

References Cited UNITED STATES PATENTS 2,783,347 2/1957 Warren 21910.81 X 2,842,650 7/1958 Naylor et al. 219-10.81 X 3,329,797 7/1967 Clark 219-10.81 3,344,254 9/1967 Manraring 2l910.8l

JOSEPH V. TRUHE, Primary Examiner L. H. BENDER, Assistant Examiner U.S. Cl. X.R.

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