US2652478A - Electric induction heating apparatus - Google Patents

Description

p 1953 J. c. HOWARD 2,652,478

ELECTRIC INDUCTION HEATING APPARATUS Filed Jan. 5, 1950 Inventor JOHN Cumsn: How/mo Attorney Patented p 15.1953

I ELECTRIC INDUCTION HEATING APPARATUS John Christie Howard, Weybridge, England, as-

signor to The Ohio Crankshaft Company; Cleveland, Ohio, a corporation of Ohio Application January 5, 1950, Serial No. 137,000 In Great Britain January 7, 1949 1 Claim.

This invention relates toelectric induction heating apparatus for heat treatment of metallic strip progressively.

There are a number of forms of inductor suitable for heating a workpiece in strip form, which act asymmetrically on the workpiece, for example on only one side of it. That known as the pancake type comprises a flat spiral coil; that known as the hairpin or loop type comprises a single turn or multiple turns of elongated shape; whilst various forms of iron cored inductor are available employing a single turn or a number of turns associated with a laminated or powder core of magnetic material to concentrate the flux. All types of inductors when energised and presented to one side of the workpiece set up mechanical forces which tend to move the strip towards, or away from, the inductor, depending on whether the workpiece is magnetic or not. In order to maintain a constant heat input to a workpiece in strip form, and hence a constant temperature, it is essential to maintain constant the relative position between the strip and the inductor. Moreover in many cases it is important not to impair the surface finish of the strip, and this rules out the use of guides through which the strip rubs, since these would tend to scratch and spoil the surface.

It is therefore an object of the invention to provide means for the heat treatment of metallic strip by electric induction heating in which the relative position of the inductor and strip is kept constant without scratching the surface of the strip.

According to the present invention electric induction heating apparatus for heat treatment of metallic strip includes a locating roller round a portion of the circumference of which the strip is wrapped, an inductor acting on that side of the strip remote from the roller, and means for keeping the strip in tension as it is advanced. The inductor may be of any of the forms referred to above, but is preferably suitably curved to conform to the curvature of the strip as it passes round the locating roller.

The invention may be carried into practice in various ways, but one specific embodiment will now be described by way of example with reference to the accompanying drawing, which represents diagrammatically in side elevation electric induction heating apparatus for the heat treatment of metal strip.

In this embodiment the strip II] is fed from a supply roll II, under a guide roller I2, over a locating roller l3, and under a second guide 2 roller M to a take-up roller [5. The relative position of the locating roller I3 and the two uide rollers l2 and I4 is such that the strip I0 is wrapped round anything up to about half the circumference of the locating roller. The strip II is kept in tension by winding mechanism acting on the take-up roll l5 and supply roll ll, thereby holding it firmly in contact withthe locating roller 1 3, which rotates freely. An inductor l6 acts upon the side of the strip [0 remote from the locating roller 13. The inductor I6 is of laminated cored type with the winding ll wound in sinuous form around teeth l8 in the stack of laminations. The core is curved so as to conform to the curvature of the strip In as it approaches, passes round and recedes from the locating roller l3. In the construction shown in the drawing, in which the strip l0 passes round half the circumference of the locating roller [3, the core is of semi-cylindrical shape as shown.

The construction of the locating roller i3 may vary but in this embodiment it comprises a refractory drum [9 mounted on a steel spindle 20 and covered with a smooth heat-resisting metal tube 2|. In this case the heat resisting tube 2| will be heated by induction and heat will be conducted from it to the strip I0, thus supplementingllthe heat produced by induction in the strip 1 se The apparatus may be employed for continuous hardening and tempering of steel strip or sheet or for annealing of ferrous or non-ferrous strip. Moreover, it may be enclosed in a gas-tight chamber to provide an inert atmosphere for bright heat treatment.

What I claim as my invention and desire to secure by Letters Patent is:

In apparatus for heating continuous lengths of moving metallic strip including a rotatably mounted drum over which the strip to be heated is adapted to pass and having an axis of r0- tation, a high-frequency inductor in operative relationship with said drum and said strip on one side of said axis and a pair of other rotatably mounted drums under which the strip to be heated is adapted to be passed and each having an axis of rotation, the axes of rotation of said other drums being positioned on a side of the axis of rotation of said first mentioned drum opposite from that of said inductor, said inductor having an arcuate concave surface having a center of curvature approximating that of the axis of rotation of said drum, the arcuate face of the inductor being in slightly spaced relationship with the surface of said drum, the improvea a ment which comprises said drum being comprised of an outer steel shell mounted on a ceramic insulating inner member, said outer shell being inductively heated by the high-frequency inductor to elevated temperatures where by to assist in the transfer of heat to the strip by both, conduction and radiation.

JOHN CHRISTIE HOWARD.

Number Name Date Frary May 10, 1921 Number Numlber Name Date Northrup Apr. 16, 1935 Wilson May 23, 1944 Denneen et a1 Jan. 14, 1947 Wilson Sept. 16, 1947 Baker et a1 Aug. 31, 1948 King Nov. 2, 1948 Lee Dec. 21, 1948 Gehr et a1. Aug. 16, 1949 FOREIGN PATENTS Country Date Great Britain Dec. 24, 1924

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