US2181921A - Induction furnace - Google Patents

Description

Dec. 5, 1939. E. 3. SCHLUP f' HSQZV xNDUcTIoN FURNACE Filed Jan. 5, 1958 2 Sheets-Sheet l FJLLL NVENTOR. fir/VEST G'. Scum/R ATTORNEYS,

f Ima BY F gg/k Dec. 5, 1939. E. G. scHLUP 2,181,921

INDUCTION FURNACE Filed Jan. 5, 1936 2 sheets-sheet INVENTOR ffm/57' SCHL up.

ATTORNEYS. I

Patented Dec. '5, 1939 UNITED STATES PATENT OFFICE INDUCTION FURNACE Application January 5, 1938, Serial No. 183,501

2 Claims.

This invention relates to devices for electromagnetically heating metal without the application of an external source of high frequency current. More specifically my invention relates to 5 a device for heating a coil of strip metal and is particularly adapted thereto, although it should be understood that other materials or bodies, particularly of annular configuration may be heated thereby.

Conventional induction furnaces require an external source of high frequency current. Generally, a frequency of 1000 cycles or more is used, although frequencies of less than 1000 cycles per second are practical. In all cases, however, some external source of such high frequency current has been necessary.

According to my invention no external source of high frequency current is required; and I am thereby enabled to eliminate all expensive high frequency generating equipment as well as the cumbersome high frequency leads to the furnace.

It is an object of my invention to provide a device for electromagnetically heating a coil of conductive material at a uniform and adjustable rate. Another object of my invention is to electromagnetically heat a coiliof conductive material with a minimum expenditure of electrical energy. Other objects of my invention include the provision of the devices above outlinedwhich will be relatively inexpensive to manufacture and simple and inexpensive to operate.

I'hese and other' objects of my invention which will be set forth hereinafter or which will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain construction and arrangement of parts of which I have shown exemplary embodiments. Reference is madel to the drawings forming a part hereof and in which:

Figure 1 vis a cross sectional View of an .induction furnace in accordance with my invention.

Fig. 2 is an isometric View of the arrangement of the externally and internally located electric conductors with reference to a coil of strip metal. Fig. 3 is a plan View of Fig. V2. Figs. 4 and 5 are partial plan views showing the orientations of magnetic fluxes in the coil.

Briefly, in the practice of my invention, I provide a casing of any desiredform such as is indicated generally at I0 in Fig. 1. This furnace has a base or floor II, and may be provided with a seal of any conventional type, as generally indlcated at I2. On the base II I provide a spacer I2 of annular form upon which a coil Il may rest.

Centrally of the base II I provide a step bearing I5 for the motor shaft I6 which is directly coupled to the motor I'I, and also has a bearing of the vertical thrust type at I8.

Upon the shaft I6 I'mount preferably two con- 5 ductor elements designated at I9 and 20. The configurations of these elements is best seen in Fig. 2. Each is an annular formation comprising a conductor extending continuously in a series of alternatively arranged return bent loops. At 2| 10 and 22 I have indicated current collector rings for the members I9 and 20, respectively. These collector rings draw power from the leads 23.

It is preferred that the motor I'I be of the type having an adjustable speed characteristic l5 for the purpose of providing for accurate heat regulation. In the operation of my device an object to be heated, as for example, the coil Il, is placed in the furnace upon the spacer I3 and the cover I0 is then emplaced, whereby the con-rv 20 ductors I9 and 20 are brought into position inside and outside of the coil. The motor I1 is then started and current is supplied to the conductors I9 and 20 from the leads 23. The current supplied may beveither alternating or di- 25 rect. The rotation of the conductors with respect to the coil produces a, 'rapidly alternating magnetic field and the coil is heated by eddy currents caused thereby. Since the heat produced varies with the speed of alternation of the magnetic fluxes, very accurate heat regulation can be accomplished by adjusting the speed of the motor I1.

' Generally speaking, coils oi strip metal as produced in rolling mill plants today have an in- 1 ternal diameter of approximately three feet and an external diameter of approximately five feet. If the conductors I9 and 20 are spaced approximately two inches apart and the motor II rotates these conductors at a speed of approximately 600 revolutions per minute, an alternating flux of approximately 900 cycles per second can be produced, when a unidirectional current source is applied to the leads 23. On account of space limitation, the number of conductors in the inner member 20 may be approximately half that in the outer` member I9, thus providing an alternating flux of approximately 450 cycles per second. However, it will be within the skill of the elec- '50 trical engineer to provide an eequal number of conductors on the inside as on the outside. If the electrical conductors are fed from an alternating current source, as for example, a conventional 60 cycle current, the rate of heating will be somewhat higher, due to tlie beating1 effect oi the 6c cycle base current.

it will be understood that a Variable capacity may be provided across the conductors in order to correct tnevpower factor, and that the value of this capacity `will depend, ainonu7 other factors, upon the sneed of rotation or the conductors i9 and 2li, and also upon the characteristics ci the magnetic circuit.

lin iigs. 4 and 5 the arrow @il indicates tile clirection of rotation of the conductors i@ and 20, respectively, and the arrows indicate tire direction oi tbe magnetic i'lelcl about the Various conductors.

'it should be understood that although l have referred throughout the specification to the neat ing of coils of strip metal, my device is equally adapted to the heating oi other objects, partic= ularly of annular formation whereby inner and outer rotating conductors may be used. it will also be clear that While l have shown the coil as being stationary and the conductors as being rotatecl, the same result would be obtained if the conductors were stationary and the coil was rotaterl. It is therefore to be understood that various modincations may be made without departing from the spirit of my invention, and that li @,lii

do not intend to limit myself otherwise than as pointed out in tlie claims that follow.

Having thus described my invention, what I claim as new and clesire to secure by Letters Patent, is:

i. An induction furnace for heating annular metal elen'lentsu ccinnrisine7 a casing, a loan of annular formations comprising conductors ei= tending continuously, respectively, in a' series ci alternately arranged return bent loops, one of said formations being disposed to surround the metal element to be lieatecl, anol the other iis nosed Within the saine, nouer leads for sairl con ductors, and means for rotating said formations.

2. A method oi heating annular metal meinn bers, which includes tbe steps of setting un a nlurablty of substantially parallel cylindrical elece troinagnetic nelcls cutting tlirougn a .member to be heated from tbe outside, setting up a plurality of substantially cylindrical electromagnetic fields cutting through said member from the intuitieu the sense of adjacent such ilelds both in the inner and outer annulus being opposite, and causinaJ relative movement between saiol metal member and 'said fields about an axis substantially par allel to the axis of said iielris.

ERNEST G. SCI-ELU?.

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