US2397629A

US2397629A - Induction heating

Info

Publication number: US2397629A
Application number: US491304A
Authority: US
Inventors: Nelson R Stevens
Original assignee: Induction Heating Corp
Current assignee: Induction Heating Corp
Priority date: 1943-06-18
Filing date: 1943-06-18
Publication date: 1946-04-02
Anticipated expiration: 1963-04-02

Description

April 1946. NB. STEVENS 2,337,629

INDUCTION HEATING Filed June 18, 1943 2 Sheets-Sheet '1 j v-Lsorv' 5. STEVE/V6.

ATTO/P/VEKS.

April 2, 1946.

N. B. STEVENS INDUCTION HEATING Filed June 18, 1943 2 Sheets-Sheet 2 GUENCHING FLU/D v INVENTOR. I I ZVZISO/VfiJTfi/EMS.

Z M CM Patented'A r. 2, 1946 INDUCTION HEATING Nelson B. Stevens, Woodhaven, N. Y., assignor to Induction Heating Corp., New York, N. Y., a corporation of New York Application June 1a. 194:, Serial No. 491,304

zclaims.

This invention relates to induction heating, and apparatus therefor, which is particularly'adapted among other possible uses, for internally heating objects with small cavities.

The internal induction heating of objects such as engine cylinders and the like has generally heretofore been accomplished by inserting a work coil having a number of turns arranged coaxially with the cylinder or cavity. But such an arrangement would be difllcult and have serious disadvantages if applied to the problem 01 internally heating cavities of small diameter. The conductor turns of the work coil have to be relatively large in order to embody a cooling fluid conduit and also to be able to conduct sufficient power for rapid heating eilects. Hence, if the cavity to be heated is small, there will be insufficient space available for convenient coaxial arrangement of the conductor turns, and in general it would be difllcult to conduct suilicient high frequency power into the cavity for rapid, economical heatin According to the present invention, the above noted difilculties are avoided by using a work "0011 comprising preferably a single turn having the general shape of a hairpin, adapted to be inserted longitudinally into the small cavities form of apparatus assembly embodying the invention;

to be heated. Such a hairpin turn, when its ter- 1 minals are connected to a source of high frequency powe'r, sets up a magnetic field, the lines oi force 01 which mostly extend in planes perpendicular to the longitudinal center line of the turn, as contrasted with the prior practice where the lines of force extend along planes which are ing drawings which form a part of this specification and illustrate merely by way of example, preferred forms oi the invention. The invention consists in such novel features, arrangements and combinations of parts, and methods as may be shown and described in connection with the apparatus herein disclosed.

In the drawings: I

Fig. 1 is a side elevational view of a preferred In Fig. 1 portions of a high frequency source of power are shown in the form of a transformer Ill having a secondary II and forming a part of high frequency generator equipment such for example as shown in patent to Dravneek No. 2,321,-

189. Secondary terminals for the transformer are shown at l2, l2. These respectively may be connected to lugs as at l3, 83', on which a pair of conductor bars 54, 14 are supported, as shown in further detail in Fig. 4. A cooling fluid conduit as at i5 of non-magnetic metal may be brazed to one or the lugs l3 and also along the bar it as at W. The outer end of bar i4 may be bent downwardly as at it, and formed as shown in Fig. 2 with a somewhat angularly disposed drill hole ii, through which the conduit i5 extends. From the lower end of portion. 55, the conduit is continued in the form oi? a depending hairpin-shaped work coil is adapted.

to be inserted in the cavity is of an object 20,

which is to be heated internally.

The return end or terminal of the work coil 18 may pass up through a drill hole as at ll within a depending portion it on the conductor bar 54, and thence back to the transformer to a fluid outlet, in a symmetrical arrangement with respect to the corresponding other half of the structure above described. Thus, the cooling fluid conduit l5, l5 may be integrally formed as one single piece of metal tubing, together with the work ooiY I8 and the return connection therefor.

The term work coil as herein used is intended to apply to substantially that part of the structure, such as at l8, which is to be in active coupling relation with the work piece.

As shown in Figs. 2 and 5, the conductor bars i4, it may be separated by a strip of insulation as at 2|. Also these conductor bars may be seemed together to bolts pls w more heat to these portlozoe. this t de as at elmtole ptocluolne e eutetemtlelly uniform As shown, the transformerltl may Zoe mounted heating effect tn the work piece tmoughout on e, roletiorm 23 forming of a cabinet etruo depth of the cavity ls, et the upper tm'e having at front meet formed tvltJo, 5 eml of the eevltv there will be e. greater lose oi aperture 25, through wheels Work. eol1 heat by teelietlen. thus tequlzclng the supply J porting structure extends. be of more heat at this portion it 1103 to 3 m t located in front of 35393161 265 to the same degree as the middle portion. Also epoamtus for elevating; H'lidlowering the work since lower portion of the cavity smtoumel= o' 0 nd. out o1? ooeretle fooeltien em eel by a larger emouot of metal, more laeet fie re 1866 l. m w o Q n v 19 1 1 i for also rotating the @Ulllli the tte fitment. qutretl to relse toe temperature of true portton temple eomprlse 2, go to the degree as that ot the mltlelle portion. l. views 28. within Hence the bowed. eide portions, as shown, pro lowe the upper vitle it simple expedient :Zor ecoomplishlng next of homing e9 9. oclsm form o1? the'cevtty Wells throughout the t m the in. Th o o2 lowezc he mt thereol. The desired. uniform at the platform. :Yooezz eompree a 39 emu?) the 15g wbmve eX hydraulic @istozl ol emteiole lmom lle-mod, eccomgolishecl by reletlve rotation of form es at St. t coil and. work piece, The oegtee to wktlclo. A ter .oe G9 tae portions oi the tame. must Zoe IGDWGIL, mtg; 2? and, eomeoted t3 v 2 to e, be zeetllly determined log; trlel, and. Wlll of eon: e vertical r eml with depend upon. the elle'oe and proportions of tee ot teeelvlw wort: piece and its eevltz' A5 shown to. 2 end. 3, the work 2U the housing 28, so to the WQZE pieces piling ege peer .o oometm w is intended to have I. portions 2 3' to range as to lee its outer surface the induction heating oz: the

member 2 htemelly. Elle is, Ems mey init ally held in place by any suitable claw meant {not shown) and with. metal is extending along tlaetoeee oz" each tin. l luotively the member I the eloove described metmer, the Tore will melt em"; creep beeeath lease 'ley eapill" er objeot as r. onto r he wort; piece. or case only ts are to be ElmlQCh-Ed ongulerly *N to heat or vettical center pieces. Thus t positions. llter may be coupled operated te eleve 4

e13 stationery post

1, 15; is e h e of Work shown in ggmp isi gg in conneotloo rotation t3.

he melee.

the invention shown in Z1 1.?

J is also the tut is (settled 10:; shaft so the {39 permit rotation as indicated, also vertlc movement fol .LZ'lBGIZiOIQ. and removal of the two piece as in the case of 1. After the piece has been heated to e, suficient temper eoneeewezo). ture for desired heat-treating, water o1 other 1e elreult will lee less. quenching fluid be introduced. into the cowexample, w rk 31 alt-y as through e, nozzle 38' eosltloned with its o3". t. in-cif. with c centage each an air gap will be reluctance of its l 'x/"lth the parttot";

Shown in g, fig w g m am 'g m tip in between the spread-apart terminals of the some inwerc lv the longitudinal een hairpin ter line, whereby the portions totvetel lower While the examples of Figs. 2 and 6 both lateor head end, and toward the upper o1 tem'llnel m volve internal heating of small diameter surfaces ends, extend gradually outwardly irom the cen= of revolution, it will be understood that the same 'ter line, as compared. with the intermediate porr sim ar appa tus may b us d in p a ti e f r time of the tun. shape permits closer heating within cavities of non-ciroular cross seceoupling with the wort: piece at the app and tlon. Although. in that case the degree of tml= lowez: eml portions the oevlty for? mp 5 5 tomlltv of heating at cllfietent points about the center line of the cavity will not be quite so exact, yet since the cavities are small, the heat will be generally adequately distributed by conduction in the metal and also to some extent by the effects of eddy currents.

Figs. 7-9 show a suitable form of work coil 40, also of the general shape of a hairpin for heating the walls of a cavity as at 4| having restrictions as at 42, 43 at various elevations. In this case the work piece 44 containing the cavity may be mounted on a vertically movable support 45, rotatable about the vertical axis of the cavity 4!. The incoming conductor portion 46 (Figs. 8, 9) extends along and adjacent one element ofthe surface of revolution of the cavity, then reversing at 41 for extension as at 48 along and adjacent another element of such surface, and thence out of the cavity.

The side portions of the hairpin configuration are both bent in the same directions to laterally offset positions as at 49, 50 (Fig. 7), thereby providing a shape to substantially correspond to the contour of elements of the side walls of the cavity at portions of varying diameters. Because of these laterally offset portions, this form of work coil turn cannot be arranged with its two side portions symmetrical with the axis of the cavity, and with close coupling relationship to the cavity walls, while still permitting insertion and removal of the work coil. Accordingly, here the vertical center line of the Work coil is preferably arranged along but in spaced relation to the vertical axis of the cavity, as is best shown in Fig. 9. This still permits both side portions of the hairpin configuration to extend along in close inductive relation with elements of the surface of revolution being heated. To insert or remove the work piece in the apparatus without jamming the offset portions 49, 50 against the walls of the cavity, it is first necessary of course to slide the work piece sideways to bring the work coil to a more 'central' position to clear the restrictions 42, 43.

Hairpin-like coil turns such as of Fig. 7, are also adapted to heat straight-walled cavitiesto different degrees at different elevations. For that purpose, offset portions as at 49, 50 would be located at elevations where less heating is desired.

With the above described examples of the invention, it has been found possible to quickly heat to redness the internal walls of objects such as shown, upon making flow through the work coil turn, current at a frequency for example of 375,000 cycles. It is found that such objects having cavities for example of about /2 inch in diameter, and 1 /2 inches in depth, could be thus heated by supplying to the work coil about 5 kilowatts at such frequency, and with approximately 300 volts across the upper ends of the hairpin turn.

While the invention has been described in detail with respect to a certain preferred example, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. A high frequency work coil for applying heat by magnetic induction inside a cavity of an object, comprising a turn formed with a cooling fluid cavity therein and having the general shape of a hairpin, the sides of which are bowed I somewhat inwardly toward the longitudinal center line, whereby the portions toward the head end and toward the terminals extend gradually outwardly from said center line as compared with the intermediate portions of the turn.

2. Method for the induction heating of' the internal walls of small diameter cylindrical cavities, which comprises the steps of inserting a hollow conductor turn into the cavity in position to extend along and adjacent one element of the side wall of the cavity, then across and returning along and adjacent another element of the side wall of the cavity and out thereof, the sides of said turn which extend along said elements being so positioned as to be bowed somewhat inwardly toward the longitudinal center line of the cavity, whereby the portions of the turn toward the outlet end of the cavity and toward the base of the cavity extend gradually outwardly from said center line as compared to v the intermediate portions of the turn, conducting a stream of cooling fluid through the hollow turn, and applying high frequency current to the turn, whereby heating of the cavity walls is caused by a magnetic field having its lines of force extending along planes generally perpendicular to the axis of the cavity.

NELSON B. STEVENS.