US2385904A

US2385904A - Electrical heating apparatus

Info

Publication number: US2385904A
Application number: US492821A
Authority: US
Inventors: William M Witty
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1943-06-30
Filing date: 1943-06-30
Publication date: 1945-10-02
Anticipated expiration: 1962-10-02

Description

* Oct. 2, 1945.

W, M. WlTTY ELECTRICAL HEATING APPARATUS Filed June 30, 1943 Patented Oct. 2, 1945 i 2,385,904 ELECTRICAL HEATING APPARATUS William M. Witty, Haddonlield, N. J., assignor to Radio Corporation of America, a corporation o! Delaware Application June 30, 1943, Serial No. 492,821

(Cl. 21S-13) 13 Claims.

This invention relates to electrical heating aplparatus, and more particularly to apparatus for heating electro-conductive articles by induction with the aid ci high frequency electrical energy.

many industrial applications, it is necessary, during the manufacture oi various articles, to apply heat thereto. in some cases, it is desirable to apply the heat only locally and with i'air ram pidity. @ne such example is in the case of ca pacitor cans comprised ci a receptacle and a cover which is soldered thereto.

lit has been proposed, heretofore, to employ radio frequency energy' for heating electro-corr ductive articles cy induction. ln accordance with customary practice employing radio frequency energy, applicator coils or inductors are used which are placed around the Work, particularly Where the Work is small. An arrangement or' this sort is obviously unsalted to a continuous heating operation AWhere a plurality of articles are to be heated, as in conveyor 'belt operation.

The primary object of my invention is to provide an improved apparatus `ior applying radio freoueocy energy inductivcly to a succession of discrete articles to ce heateda More particularly, .it is an object ci my oreserit invention to provide an imoroved apparatus for inductively heating electro-ccnductive articles hy means of radio frequency enero which apparatus is highly suitable for high speed production in continuous operations.

' another object ci my present invention to provide ari improved apparatus as aforesaid which is particularly suited the application oi' radio frequency induction heating to effect soldering.

gialli another object of my present iiivcticn is to provide an improved. inductive heat'. g acparatus by means ci? which electrical energy loe applied erilcierltly to the articles to ice 'treated during manufacture for purpose ci selectively generating 'heat within the articles While they are moved. along continuously on a conveyor belt.

il further object of my 'present invention is to provide improved inductive heating apparatus as above set iorth wherein the leakage reactance reduced to a minimum.

Still a further object of my present invention is' to provide improved inductive heating apparatus as above set forth which is inexpensive in cost and in operation, and which is extremely efficient in use.

In accordance with the present invention, I make use of specially shaped inductor devices as applicators which form the load coupling circuit of a radio frequency generator and obtain thereby very eiicierrt coupling to the articles which are lto be selectively heated, as for soldering or the v one form of my present invention, the inductors may be constituted by elongated conductors the ends of which are onset with respect to the body portion, with the ends constituting very short leads for connection to the transformer. This, together with 'the fact that the two inductors are connected together electrically in. parallei relation as iar as the generator is concerned, results in less effective leakagey reactance; and

this, inturn, together with the efect'of series coupling insofar as the load is concerned; resuits in a very high percentage of overall erliciency.

The novel features 'that I consider characteristic of my invention are set iol-th with particuiarity in appended claims. The invention itself, however, Yoo'th as to its organization and method of operation, as well as additional objects and advantages thereof, will best "ce understood trom the following description of one emhoclimerot thereof, when read in connection with 'the accompanying drawing in which:

Figure i is a perspective View ci one form o11 heating device o unt constructed in accordance 'with my invention,

Figure 2 is a similar View but showing, in acldition, a portion of the endless conveyor and one unit of the work thereon in relation to the heating device,

L'ilgure 3 is an enlarged, fragmentary sectional view taken on the line Il I--III of Figure 2. and

Figure a is a wiring diagram showing the connection of the coupling inductors to the transformer and the relation of the inductors to the work.

Referring more particularly to the drawing wherein similar reference characters designate corresponding parts throughout, there is shown a tubularrsupporting member l of insulated material on which is Wound the primary Winding 3 las a vacuum 'tube oscillator.

of a transformer coupled to a suitable high irequency oscillation generator (not shown), such Surrounding the primary winding 3 and spaced therefrom by plurality of circumferentially distributed, longitudinally disposed, insulated spacing members 5 is a single turn secondary winding fl of copper sheet material. The ends 'Ia and lb of the in each instance.

l aseaeoa for the purpose of uniting the cover` to the case Close magnetic coupling be- Jtween the work l@ and the inductors Il and IS secondary Winding I are bent outwardly to form a pair of spaced, terminal members, and they are formed, respectively, adjacent one end with the slots 9a and 9b.

Connected to the secondary winding terminals Ia and Ibare a pair of inductor coupling devices 1 or applicators I I and I3 by means of which heating currents are induced in the work in the manner shortly to be described. The applicators or devices Il and i3 are constituted by conductors having elongated, intermediate body portionsv Ita and i3d formed with substantially right angle bends IIb and lb. The body portions lla and Ita are disposedphysically in spaced relation and are arranged generally parallel to each other. Beyond the bends IIb and lh, the applicators are formed with reverse or U-bends IIc and 53o to provide end portions which are disposed in substantially parallel planes approximately at right angles to the plane in which the body portions IIa and I3a`lie. As best' seen from Figure 1, the Inductor or applicator I I is connected at one end to the terminal la, its other end passing through. the slot 9a without contacting the terminal 'lo and being connected to the terminal 1b. Similarly, the inductor or applicator I3 is connected at one end to the terminal Il?, its other' end passing through the opening 9b out 'of contact with the terminal 'Ib and being connected to the terminal 1a. Thus,

i the two inductors I I and \I3 are not only arranged in physically parallelrelation relative to each other, but are also connected in parallel relation electrically across the secondary winding as will be noted from Figure 4. Y v Betweenthe loopsformed by the U-bends IIc and I3c, there `is movably carried'an endless conveyor belt I5. A plurality of insulated receptacles I'I are secured to the belt I 5, as by means of rivets l' ,I8 (only one receptacle beingshown in the drawing by way of illustration). 'I'he receptacles I1 are so dimensioned that the sides thereof will be is obtained by reason of the fact that the recep= tacles Il are in close proximity to the inductors.

Since the inductors II and I3 are so connected to the secondary winding 'i that currents will ow therein in opposite directions instantaneously, as represented by the arrows A and B of Figure 4, it is apparent that the currents A and B will induce in the load constituted by each of the work units 'I9 currents represented by arrows l C and D. Because the currents C and D are in series,I it is apparent that they will be cumulative or additive in effect. Moreover, since the leads constituted-by the U-bendsv lic and i3@ which connect the body portions lla and' lila of the inductors to the secondary terminals la and Eb are very short, the leakage reactance will be reduced to a minimum. This factor, teken with the'serles coupling ot the inductors insofar as the load is concerned, results `in a v ery high percentage of overall emcienoy.

From the foregoing description, it will be apparent that my improved vheating apparatus affordsran arrangementfo'r heating the Work on an endless conveyor set-up with great emciency.

The speed of the conveyor belt I5 and the power input into the work will, of course, depend uponl various factors, such as the rate at which an operator can load the work, the lengths of the inductors I I. and I3, the temperature towhich it is desiredto bring the work, etc. In one installadisposedA in as close proximity to the body portions 1 of the inductors II and I3 as is feasible while the receptacles il are being advanced between the inductors by the'endless belt l5. Each of the vreceptacles Il is adapted to 'work units i9.

receive one or rnore- By Way of illustration, the Work units i9 have been shown as constituted by capacitor cans of conducting material and comprised of -a case 59a to which a bottom cover ith/is to be secured. For this purpose, the inner surface or" the bottom teli, or iowervpvortion oi the outer surface of the case ita, or both, may be coated. with a layer of relatively low melting point solder iii. During e...

tion, for example, where the work wasloaded lat a rate of about 2500 units per hour, whe're the inductors l I and I3 were approximately six inches in length. and where 4 kw. of power were delivered to the inductors at a frequency 'of 350 kc. per second; the belt I6 was advanced at a rate of about 20 feet per minute. In this particular installation, the inductors II and I3 and the .primary winding 3 were all made of copper tubing through which water was passed for cooling.

Although I have shown and described but one embodiment. of my invention, it will undoubtedlybe apparent to those skilled in the art that desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims;-

I claim as my invention: L f

l. in inductive heating apparatus, the combination of al pair of inductor coupling devices disposed one along eachside of a predetermined path with the maior portion of their lengths extending along at least a portion o,f"said path, means for coupling said devices to asource oi high frequency electrical energy, means connecting saiddevices to said ilrst 'named means in parallel relation electrically and providing a smali leakage reactance, and a movable carrier arranged for movement along said path adjacent to said devices, Said carrier being adapted to support a plurali' of electro-conductive work units i and to more said units in succession one said pa in inductive relation to each oi d devices, a c current passed through both said as hey are advanced along motive heat"z ng apparato r' @t L" induce heating current tending along at least a portion of said path,

means for coupling said devices to a source of high frequency electrical energy, means providing a small leakage reactance connecting said devices to said first named means inv parallel relation electrically in such a manner that current will flow throigh said devices instantaneously in opposite directions, and a movable carrier arranged for movement along said path adjacent to said devices, said carrier being adapted to support a, plurality of electro-conductive Work units thereon and to move said units in succession along said path in inductive relation to said devices, the current passed through said devices serving to induce heating current in said units as they are advanced along said path.

3.'Heating apparatus according to claim 2 wherein said inductor coupling devices include short leads whereby they are connected to said means.

4. Heating apparatus according to claim 2 wherein said inductor coupling devices are comprised of relatively elongated members disposed in physically parallel relation, said members terminating in relatively short offset portions constituting leads for connection thereof to said means. n

5. Heating apparatus according 'to claim 2 characterized by the addition of a plurality of work supporting members on said carrier, each adapted to receive at least one of said work units.

6. Heating apparatus according to claim 2 characterized by the addition of a plurality of Work supporting members secured to said carrier and each adapted to receive at least one of said work units, and characterized further in that said work supporting members are so arranged on said carrier as` to be in close proximity to said inductor coupling devices as said members are advanced along said path whereby to effect close magnetic coupling between said devices and the units in said members.

7. In inductive heating apparatus, the combination of a transformer of which the primary winding is adapted to be connected to a source of high frequency electrical. energy, a pair of .l

inductor coupling devices, means connecting said inductor coupling devices in electrically parallel relation across the terminals of the secondary winding of said transformer and providing a small leakage reactance, said devices comprising a pair of elongated conductors disposed in physically parallel, spaced relation along at least a portion of a predetermined path with the major portion of their lengths extending parallel to said -path portion, and a movable conveyor adapted to support a plurality of electro-conductive work units arranged for movement along said path to advance said units through the space between said devices and in close proximity thereto whereby to bring said units successively intoinductive relation with each of said devices.

8. Heating apparatus according to claim 'I characterized in that said conveyor is constituted by an endless belt.

9. Heating apparatus according to claim 7 characterized in that said conveyor is constituted by an endless belt, and characterized further by the addition of a plurality of work receiving receptacles secured to said belt, said receptacles being of such dimensions and being so disposed ony said belt that the sides thereof are in close proximity to said conductors while they are being moved through said space.

10. In inductive heating apparatus, the combination of a movable carrier, a plurality of work supporting elements mounted on said carrier and adapted to be moved through an endless path thereby, a Apair of inductor devices disposed in physically parallel relation one on each side of said path with the major portion of their lengths extending along at least a portion of said path whereby said elements will be moved between said devices, said devices being also connected in parallel relation electrically, means for coupling said devices to a source of high frequency energy, and means providing a' small leakage reactance connecting said devices to said coupling means.

11. In electrical heating apparatus, the combination of a transformer having a multi-turn primary winding and a single-turn, conductive, sheet; member inductively related to said primary winding and constituting the secondary winding of said transformer, said secondary winding having a single pair of output terminals, and a pair of inductor coupling members connected i'n parallel relation electrically across said secondary Winding output terminals, said members each comprising an elongated conductor having its end portions offset from the body thereof, and the terminals of said end portions being connected to said secondary winding output terminals.

12. In electrical heating apparatus, the combination of a transformer having a multi-tum primary winding and a single-turn, conductive, sheet member inductively related to said primary winding and constituting the secondary winding of said transformer, said secondary winding having a single pair of elongated output terminals,

and a pair of inductor coupling members connected in parallel relation electrically across said secondary winding output terminals, said members each comprising an elongated conductor disposed along a separate one of said elongatedfoutput terminals and having its end portions oifset from the body thereof, and the terminals of said end portions being connected tovsaid secondary winding output terminals.

13. An inductor coupling device comprising an elongated conductor having end portions bent substantially at right angles to the body portion thereof, said end portionsy having reverse bends in parallel planes eachsubstantially normal to said body portion, and said reversely bent portions extending generally inthe same direction.