US3081989A - Induction heating coil - Google Patents

Description

March 19, 1963 E. F. MOBRIEN 3,081,989

INDUCTION HEATING COIL Filed April 20, 1960 INVENTOR EDWARD F. McBRIEN FIG. 4 50 ATTORNEY United States Patent 3,081,989 INDUCTION HEATING COIL Edward F. McBrien, Parrna, Ohio, assignor to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 20, 1960, Ser. No. 23,449 4 Claims. (Cl. 266-4) This invention relates to induction coils of the type adapted for use in heating applications, and more particularly to an induction heating coil characterized in having a large number of turns confined within a limited amount of space. Such inductors are useful, for example, in hardening and hot-machining applications where, due to space limitations, it is impossible to obtain the desired number of coil turns using conventional coil construction.

As is'well known, increasing the number of turns'in an induction heating coil increases the coil efiiciency, decreases the required inductor current, and makes it possible to more accurately control the heat pattern produced by the coil. Furthermore, in'some cases a largernumber of turns eliminates the need for a transformer and its associated heavy bus bars leading to the coil.

In theusual induction heating coil, a copper tube or the like is wound in one or more turns to produce the desired heating pattern, with the heat generated in the coil being carried away by a cooling fluid which flows through the hollow copper tube. Since the copper tube has a substantial width, an inductor of this type having the desired number of turns may require a larger amount of space than that available for the application at hand. In the hotmachini'n'g field, for example, it is frequently desirable to progressively heat the metal immediately adjacent the cutting tool. Due to space limitations, only a few turns are possible in 'a conventionalinductor due to the width of the aforesaid'coppe'r'tube. Thus, the required currents are relatively large and necessitate a transformer which must be mounted adjacent the cutting tool or heavy flexible leads must be employed to carry the inductor currents to the coil. "These requirements have restricted the use of induction heating in this and other fields where space limitations are important.

As an overall object, the present invention seeks to provide a new and improved induction coil arrangement having a maximum number of turns for a given amount of space whereby the coil efiiciency may be increased and the required inductor current decreased with more accurate control of the resulting heat pattern.

More specifically, an object of the invention is the provision of an induction heating coil formed from a plurality of turns of continuous length of flat metal strip wound in a spiral configuration whereby the long transverse sides of successive turns of the spiral lie adjacent each other, in combination with insulation between the turns of the spiral at the edges of the strip to provide a continous passageway between the turns through which a cooling fluid may pass. Thus, whereas the cooling fluid was conducted through the center of the coil itself in prior art assemblies, the present invention provides an arrangement wherein the cooling fluid is conducted between successive turns of the inductor.

Still another object of the invention is to provide an induction coil assembly particularly adapted for use in fillet hardening applications.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification and in which:

FIGURE 1 is atop or plan view of an induction coil constructed in accordance with the teachings of the present invention and adapted for use in the heating of fiat sur faces and the like;

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FIGURE 2 is a cross sectional view taken along line II-II of FIGURE 1;

FIGURE 3 is an enlarged illustration of another embodiment of the invention particularly adapted for use in fillet hardening applications and incorporating integral quenching means; and

FIGURE 4 is an illustration-of still another embodiment of the invention adapted for use in heating elongated workpieces.

Referring to FIGURES 1 and 2, the coil shown is of the pancake type which may, for example, be used to heat the surface of a metal strip 10 or other similar 'flat surface. As shown, the inductor comprises a continuous length of solid copper strip "12 wound in a spiral about an axis extending parallel to the long transverse dimension of the strip. As an example, the coil maybe formed from copper strip having a thickness of inch and a width of 1 inch; however, 'the particular dimensions of the strip will, of course, depend upon the current-carrying capacity of the coil. In any event, the width .of the strip should be at least three times its thickness 'to achieve the advantages outlined herein. A U-shaped strip of insulation 14 is slipped over the longitudinal edges of the copper strip 12 before it is wound into a spiral, although it could be ap plied afterthe coil is formed. To form the coil, the strip with the insulating strips 12 applied 'to its edges, is rolled up or coiled to provide a continuous passageway 16 between the successive turns of the coil which are sealed at their opposite edges. A suitable adhesive may be'applied to the strip 12 before coiling or the finished coil may be potted in accordance with known procedures. The ends of the passage 16 are sealed as at 18 and 20 whereby a cooling fluid maybe passed through the passageway between inlet and outletport's 22 and 24, respectively. Electrical leads 26 and "28 are provided 'for connection to a suitable source of "alternating current voltage, not shown.

It will readily be seen that since the thicknessof the "copper strip 12 is very small, a large number of turns may be produced in the coil fora given amount of space. Thus, the coil may be employed in installations where a conventional coil of a similar number of turns would be too large.

Referring to FIGURE 3, the workpiece 30 may be a flanged axle shaft or the like having a fillet as at 32. In order to harden this fillet it is necessary to induce currents in the flange portion 34 as well as in the main shank 36 of the workpiece. This would be difiicult with a conventional inductor due to space requirements. By employing the inductor shown in FIGURE 3, however, the desired result may be effected. This inductor again comprises a continuous length of solid copper strip 38 having a width many times its thickness; but in this case the width of the strip continuously varies to provide turns of varying widths in the inductor. Continuous U-shaped strips of insulation 40 are again slipped over the longitudinal edges of the strip before it is formed into a coil. In this embodiment, however, a third strip of insulating material 42 is disposed between the successive turns of the coil between strips 40 to thereby divide the coil into two separate passageways 44 and 46. The strips 40 at the inner periphery of the coil assembly are provided with apertures through which tubes 48 extend. Thus, when a quenching fluid is conducted through the passageway 46 via inlet and outlet ports 45 and 47 it will pass through the tubes 48 and onto the surface of the fillet or other portion of the workpiece being treated. At the same time, a cooling fluid may be forced through the passage 44 via ports 49 and 51 to carry away the heat generated in the strip 38. Electrical leads, not shown, are again connected to the opposite ends of strip 38 as in the embodiment of FIG- URE 1. Actually, the current density will be greater at the inner periphery of the strip 38 which is removed from the cooling passage 44. However, the heat generated at 3 the inner periphery of the strip will be readily conducted to the outer peripheral portion where it may be transferred to the cooling fluid conducted through passage 44.

In FIGURE 4, still another embodiment of the invention is shown wherein a solid copper strip 50 is wound in a spiral configuration about an axis extending parallel to the short transverse dimension of the strip. The construction of the coil in this case is similar to that of FIG- URE 1 and includes U-shaped strips of insulating material 52 applied over its edges. As will be understood, cooling fluid and electrical connections, not shown, are provided. It will be noted that the curvature in the strip is now across its width rather than its edge. With this arrangement, a large number of turns can be produced in the coil over a relatively short length. Thus, the coil is particularly adapted for use in heating elongated workpieces where space requirements are a consideration.

Although the invention has been shown in connection with a specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. An induction coil comprising a continuous length of solid electrically conductive strip material having a width many times its thickness and wound in a spiral configuration in which the long transverse sides of the strip material lie adjacent each other, insulation disposed between the turns of the spiral at the opposite edges of the strip material to provide a continuous passageway betweenthe turns, means for sealing the opposite ends of the passageway, and connections communicating with said opposite ends for conducting a cooling fluid through the passageway.

2. An induction coil comprising a continuous length of solid electrically conductive strip material having a width many times its thickness and wound in a spiral configuration having successive turns in which the long transverse sides of the strip material lie adjacent each other, U-shaped strips of insulating material with the insulating strips on successive turns of the spiral abutting each other to provide a continuous passageway between the turns, and

means for conducting a cooling fluid through the passageway.

3. An induction coil comprising a continuous length of solid electrically conductive strip material having a width many times its thickness and wound in a spiral configuration in which the long transverse sides of the strip material in successive turns of the spiral face each other, continuous lengths of insulating material disposed between the turns of the spiral to provide two separate and continuous passageways between the turns, spaced openings in one of said continuous lengths of insulating material adjacent a peripheral edge of the coil, means for injecting a quenching fluid into said one passageway whereby the quenching fluid may pass through the openings in said one length of insulating material and onto the surface of a workpiece disposed within the coil, and connections for conducting a cooling fluid through the other of said passageways.

4. An induction coil comprising a continuous length of solid electrically conductive strip material having a width many times its thickness and wound in a spiral configuration in which the long transverse sides of the strip material in successive turns of the spiral face each other, continuous lengths of insulating material disposed between the turns of the spiral at the opposite edges of the strip material and at the center thereof to provide two continuous passageways between the turns, spaced openings in the continuous length of insulating material at the edge of the strip material which defines the inner periphery of the coil, means for injecting a quenching fluid into the passageway communicating with said openings whereby the quenching fluid may pass through the openings and on to the surface of a workpiece disposed within the coil, and connections for conducting a cooling fluid through the other of said passageways.

I References Cited in the file of this patent UNITED STATES PATENTS 2,481,071 Bowlus Sept. 6, 1949 2,863,130 Gray et al Dec. 2, 1958 FOREIGN PATENTS 293,200 Switzerland Dec. 1, 1953 730,104 Great Britain May 18, 1955

Claims (1)

1. 4. AN INDUCTION COIL COMPRISING A CONTINUOUS LENGTH OF SOLID ELECTRICALLY CONDUCTIVE STRIP MATERIAL HAVING A WIDTH MANY TIMES ITS THICKNESS AND WOUND IN A SPIRAL CONFIGURATION IN WHICH THE LONG TRANSVERSE SIDES OF THE STRIP MATERIAL IN SUCCESSIVE TURNS OF THE SPIRAL FACE EACH OTHER, CONTINUOUS LENGTHS OF INSULATING MATERIAL DISPOSED BETWEEN THE TURNS OF THE SPIRAL AT THE OPPOSITE EDGES OF THE STRIP MATERIAL AND AT THE CENTER THEREOF TO PROVIDE TWO CONTINUOUS PASSAGEWAYS BETWEEN THE TURNS, SPACED OPENINGS IN THE CONTINUOUS LENGTH OF INSULATING MATERIAL AT THE EDGE OF THE STRIP MATERIAL WHICH DEFINES THE INNER PERIPHERY OF THE COIL, MEANS FOR INJECTING A QUENCHING FLUID INTO THE PASSAGEWAY COMMUNICATING WITH SAID OPENINGS WHEREBY THE QUENCHING FLUID MAY PASS THROUGH THE OPENINGS AND ON TO THE SURFACE OF A WORKPIECE DISPOSED WITHIN THE COIL, AND CONNECTIONS FOR CONDUCTING A COOLING FLUID THROUGH THE OTHER OF SAID PASSAGEWAYS.

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