US2490104A - Apparatus for equalized induction heating of workpieces - Google Patents

Description

- 1949 H. A. STRICKLAND, JR

APPARATUS FOR EQUALIZED INDUCTION HEATING OF WORKPIECES Flled Apnl 12, 1945 *PICIL PICI 2 RIGID".

l N V EN TOR Harold A. SUE/(land, Jr. W WQJW Q A TTORNE Y Patented Dec. 6, 1949 UNITTED- Se'IZATESJQ PATENT OFFICE.

APPARATUS. EOR- EQUALIZED-INDUCTION HEATING OF WORKPIECES.

Harold A. Strickland; Ji-., Detroit; Mich, assi'gnor,

by mesne assignments, to The. OhioCrankshath Company, Cleveland, Ohio, a corporation of Ohio Application April 12, 1945, Serial No. 587,986

nace of this type is generally satisfactory where the workpiece is uniform in-shape; for example,

cylindrical, but where the workpiece is not uni-- formly shaped as, for example, where the diameter of the central section of the workpiece is less than the diameter of the ends, this type of furnace may not be satisfactory as it may produce overheating of the central section.

A primary object of the present invention is to provide apparatus and circuit arrangements which may be utilized in connection with a heating coil to modify the energy available for heating along the length of the heating coil so as to conform to variations in the substance of the workpiece along the axis of the heating coil.

Still another object of the invention is to provide effective adjusting means for the energy output of a heating coil along its length which may be applied to usual existing furnace types without difficulty.

An object also is to provide energy adjusting means which may readily utilize alternative apparatus to accomplish the desired results.

Further objects will appear on consideration of the apparatus and circuit of an embodiment of the invention hereinbelow set forth and illustrated in the accompanying drawing, in which:

Figure l is an elevation of an induction heating coil unit with the control unit connected therewith;

Figure 2 is a diagrammatic showing of inductive means for controlling the energy flow along the coil axis;

Figure 3 shows a workpiece of irregular shape.

Referring to Figure 1, there is shown in outline an induction furnace I which includes the usual heating coil 2 of uniformly dimensioned and spaced turns surrounding a heating chamber 3. The heating coil is externally and internally lined with fire-proof insulation layers 4 and 5 and the furnace chamber is lined with fire-brick 6 supported by tubular cooling rails I. These rails are provided with support lugs 8 for holding the workpiece 9 in position within the chamber.

The coil is provided with a plurality of taps II] which extend outwardly at the side of the furnace. The furnace coil and accessory parts are supported on asbestos composition end plates II and I2 5 Claims. (01. 219-13) I asiindicatedi Alternating: currentsiszsupplied' from llf since both-pairs of asbestos composition support asource, preferably, of'high frequency current- In" order to 'secure'the variation. in energy out.- putof'tlie induction h'eatings'coil Ifor' heating are ticles of irregular-shape; I utilize asecond coil enerally indicated by the numeral I3 which is mounted'directly' above the furnace. Thisauxiliary unitacomprises a-singlecoil" Ii -provided with taps I5 and supported by endplates I6 and IL the other as shown. Electrical connection is made between the two coils through the connectors I8 and I9 each of which is formed of a flat metal strip centrally apertured at one end and slotted at the other end so that the plate may be pivotally mounted on either the upper or lower taps and detachably connected to one or more of the taps in the other unit.

In operation, the main heating current is passed through the heating coil as between points 20 and 2| of Figure 2. The applied voltage and frequency may be constant in value so that a uniform heat supply is available for a uniformly dimensioned cylindrical workpiece. Should, however, an irregular workpiece such as shown in Figure 3 and in dotted outline in Figure 1, be placed in the furnace chamber, it becomes necessary to reduce the heat output in the section 22 of lesser diameter as opposed to sections 23 and 24 of full diameter. This is accomplished by connecting the upper ends of the connectors I8 and I9 to a selected length of inductor coil I4 and the lower ends of the connectors to taps opposite the ends of section 22 so that the portion of the heating coil which encloses section 22 of the workpiece and is operative for heating the same is by-passed by the parallel connection of inductor I3. This parallel connection effectively reduces the current flow in the furnace coil section opposite section 22 of the workpiece so that the heating effect is minimized to the point of safe and adequate temperature for the desired purposes.

As indicated in Figure 2 and by the taps I5 in Figure 1, the inductor I3 is variable so as to obtain variation in the impedance of the shunt circuit. By utilizing an inductor shunt instead of a resistor, the power loss is substantially reduced. A related advantage of the inductor shunt for the specified purpose lies in its employment as a flux return for the heater coil, the coil turns of the impedance in shunt with selected sections of the heating coil, without disturbing the ,main heating coil circuit, applicant is able to secure any de-.

sired variation of heat energy input to the work piece and this may be accomplished readily with out important modification of the standard heating coil arrangement.

The showing as made is diagrammatic and hence no limitation is implied thereby otherz-than may be required by the scope of the claims hereto appended.

What is claimed is:

1. In combination, an electric induction heating coil wound in a single direction and having connections to an electric power source, said coil-having a plurality of taps intermediate said connections and an inductance coil connected across at least a pair of said taps intermediate said connections, whereby to reduce the heatingjeffect of the heating coil between the taps connected tosaid inductance coil;

2. The combination of claim 1 wherein'said inductance coil has a variable inductance.

3. The combination of claim 1 wherein said inductance coil has a plurality of taps along its length adapted to be selectively connected to the taps of said heating coil.

4. The combination of claim 1 wherein the flux field of the inductance coil is opposite to the flux fieldof the heating coil and the inductance coil is positioned exteriorly of and adjacent to the heating coil whereby the flux fields may be additive.

5. The combination of claim 1 wherein said inductance coil is wound in an opposite direction to said heating coil and said coils are disposed in adjacent relationship with their axes substantially parallel.

HAROLD A. STRICKLAND, J R.

REFERENCES CITED The 'iollowing references are of record in the file of this patent;

UNITED STA ES P-A'I'ENTS Number Name Date 1,791,934 Northrup Feb. 10, 1931 25%: 1,834,725 Northrup Dec. 1, 1931 1,943,802 I Northrup Jan. 16, 1934 1,946,876 Northrup Feb. 13, 1934 2,308,043 Bierwirth Jan. 12, 1943 2,383,992 Sherman Septv 4, 1945 Kennedy Oct. 26, 1948

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