US3848107A

US3848107A - Inductor for heating elongated metal workpieces

Info

Publication number: US3848107A
Application number: US00428413A
Authority: US
Inventors: J Lewis
Original assignee: Park Ohio Industries Inc
Current assignee: Park Ohio Holdings Inc
Priority date: 1973-12-26
Filing date: 1973-12-26
Publication date: 1974-11-12
Anticipated expiration: 1991-11-12
Also published as: CA968417A

Abstract

An inductor is provided having an axis of orientation which coincides with the axis of a metal workpiece disposed in magnetically coupled relationship therewith. The inductor is comprised of a continuous conductor including first and second helical portions which are diametrically opposed, extend about the axis of orientation, and are twisted to have the same hand of lay with respect to the axis of orientation.

Description

United States Patent [1 1 I Lewis 1 Nov. 12, 1974 INDUCTOR FOR HEATING ELONGATED METAL WORKPIECES [75] Inventor: John C. Lewis, Wentworth, Ontario,

Canada [73] Assignee: Park-Ohio Industries, Inc.,

Cleveland, Ohio 221 Filed: Dec.26, 1973 21 App1.No.:428,413

[52] US. Cl 219/l0.79, 219/1057 [51] Int. Cl. H05b 5/08 [58] Field of Search 219/65, 10.79, 10.43,

219/10.57, 10.67, 10.73, 10.41; 266/4 El, 5 El [56] References Cited UNITED STATES PATENTS 3,203,211 8/1965 Mallinckrodt 219/65 X 3,271,115 9/1966 Keller 219/1043 X Primary ExaminerBruce A. Reynolds [57] ABSTRACT An inductor is provided having an axis of orientation which coincides with the axis of a metal workpiece disposed in magnetically coupled relationship therewith. The inductor is comprised of a continuous conductor including first and second helical portions which are diametrically opposed, extend about the axis of orientation, and are twisted to have the same hand of lay with respect to the axis of orientation.

13 Claims, 7 Drawing Figures PATENTEB NOV 1 21974 SIIEUIOFZ FIG. 2

- PATENTELNUV] 2|974 SHEET 2 BF 2 INDUCTOR FOR HEATING ELONGATED METAL WORKPIECES The present invention relates to the art of induction heating and, more particularly, to an inductor for heating an elongated metal workpiece.

It is well known in the art of induction heating to inductively heat a metal workpiece by means of an inductor in the fonn of a helical coil having an axis coinciding with the axis of the workpiece when the latter is disposed within the coil in magnetically coupled relationship therewith. Such a coil generally has a plurality of closely spaced convolutions extending helically about the coil axis from one end thereof to the other, and the opposite ends of the coil are interconnected with a source of power through which the coil is energized. Upon energization of the coil, current flows along the helical path defined by the convolutions, which path is substantially transverse to the direction of the coil axis, and a magnetic field is established between the coil and workpiece in the direction of the coil axis to inductively heat the workpiece.

It is also known in the induction heating art to provide an inductor having parallel conductor portions extending longitudinally of the axis of the workpiece to be heated and generally along opposite sides of the workpiece. With such inductors, current flows through the conductor portions parallel to the outer surface of a workpiece, whereby a magnetic field is established in a direction transverse to the workpiece axis. Thus, those portions of the outer surface of the workpiece adjacent the longitudinally extending conductor portions are inductively heated and, in order to inductively heat the entire periphery of the workpiece disposed within the confines of the inductor, either the workpiece or the inductor must be rotated about its axis.

In the induction heating field, it is sometimes desirable to heat peripherally, at one time, a substantial axial portion or the entire length of an elongated workpiece such as, for example, a rod, bar or thin walled metal tube. To heat simultaneously a given axial portion of such a workpiece with a helical coil of the character mentioned above, requires of course that the coil have a length corresponding to the length of the workpiece to be heated. The length of the workpiece to be heated may be several feet, whereby the use of a helical coil inductor is undesirable both from the standpoint of low heating efficiency and high coil cost.

To heat an elongated area of a workpiece employing an inductor having inductor portions extending parallel to the workpiece axis provides for higher heating efficiency and lower inductor cost, but requires relative rotation between the workpiece and inductor to achieve heating of the entire periphery of the workpiece. Special equipment is necessary to provide for support of the workpiece in a manner which enables rotation thereof.

In accordance with the present invention, an inductor for heating elongated workpieces is provided which has a geometry advantageously providing for the peripheral surface of a workpiece to be heated along a given longitudinal length thereof without the disadvantages attendant to heating such a workpiece with prior inductor configurations including those discussed hereinabove. More particularly, the inductor of the present invention advantageously provides for current flow to be in a direction longitudinally of the workpiece axis,

thus to increase heating efficiency and reduce the amount of conductor material required. At the same time, the inductor advantageously provides for the workpiece to be heated peripherally in a manner which is efficient with regard to heat disbribution and which does not require relative rotation between the workpiece and conductor portions of the inductor. Thus, the workpiece can be heated substantially uniformly about the periphery thereof in a minimum of time and without the special apparatus required if the workpiece or inductor has to be rotated.

More particularly in accordance with the present invention, an inductor is provided having an axis coinciding with the axis of a workpiece when the latter is disposed in magnetically coupled relationship therewith, and the inductor includes conductor portions extending longitudinally of the axis of orientation and helically thereabout from one end of the inductor device to the other. The helical portions of the inductor are twisted so as to have the same hand of lay with respect to the axis of orientation in a given longitudinal direction thereof. This geometry provides for each of the helical conductor portions to extend, with respect to a workpiece, from opposite sides thereof at a first location progressively along and laterally across the workpiece and thence to positions at a second location in which each conductor portion is on the side of the workpiece opposite that which it occupied at the first location. Accordingly, current flows through the conductor portions in a helical path extending longitudinally of the workpiece and progressively about the periphery thereof so that peripheral areas of the workpiece disposed within the inductor are simultaneously heated, as the workpiece progresses through the inductor.

Either the inductor or the workpiece can be longitudinally displaced relative to the other. In either case, the inductor geometry provides for the length of the workpiece scanned to be uniformly heated peripherally without relative rotation between the inductor and workpiece.

Accordingly, an outstanding object of the present invention is the provision of an inductor for heating elongated metal workpieces more efficiently than heretofore possible.

Another object is the provision of an inductor for heating elongated metal workpieces peripherally thereof along a given axial length of the workpiece in a manner which is more expeditious and efficient than heretofore possible.

Yet another object is the provision of an inductor for heating longitudinal and peripheral areas of a workpiece and having conductor portions extending along helical paths having the same hand of lay in a given longitudinal direction relative to the axis of the workpiece.

Still another object is the provision of an inductor for inductively heating an elongated workpiece of small dimension in cross section, which inductor has a length considerably greater than the cross-sectional dimension of the workpiece and which is comprised of a minimum amount of conductor material and achieves peripheral heating of the workpiece within the length of the inductor more efficiently and expeditiously than heretofore possible in a progressive heating installation.

The foregoing objects, and others, will in part be obvious and in part pointed out more fully hereinafter in conjunction with the description of the drawings depicting preferred embodiments of the invention and in which:

FIG. 1 is a perspective view of an inductor made in accordance with the present invention;

FIG. 2 is a plan view of the inductor illustrated in FIG. 1;

FIG. 3 is an elevational view in cross section of the inductor illustrated in FIG. 1, the view beingalong line 33 in FIG. 1;

FIG. 4 is a perspective view of another embodiment of an inductor made in accordance with the present invention;

FIG. 5 is a sectional elevational view of the inductor illustrated in FIG. 4, the view being taken along line 55 in FIG. 4;

FIG. 6 is a perspective view of still another embodiment of an inductor made in accordance with the present invention; and,

FIG. 7 is a perspective view of yet another embodiment of an inductor made in accordance with the present invention.

Referring now in greater detail to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting same, an inductor device is illustrated in FIG. 1 which is comprised of a continuous tabular conductor 10 of conductive material, such as copper. As illustrated, conductor 10 is in the form of a tube which is rectangular in cross section and which has opposite ends 12 and 14. Ends 12 and 14 are adapted to be connected across a suitable source 16 of alternating current for energization of the inductor device. The tubular conductor provides, in a well known manner, for cooling fluid, such as water, to be circulated through the conductor to control the temperature thereof during an induction heating operation. Accordingly, it will be appreciated that ends 12 and 14 of the conductor are adapted to be connected to a source of cooling fluid, not illustrated.

The inductor device has an axis of orientation A which coincides with the longitudinal axis of a workpiece W when the workpiece is disposed in magnetically coupled relationship with the inductor so as to be heated by the inductor upon energization thereof. Conductor 10 includes a leg 18 extending longitudinally of axis A from end portion 12, a bridging portion 20 extending across axis A from the outer end of leg 18, a leg 22 extending longitudinally of axia A from bridging portion 20 to the opposite end of the inductor device, a bridging portion 24 extending across axis A from the corresponding end of leg 22, and a leg 26 extending from the corresponding end of bridging portion 24 longitudinally of axis A to end portion 14 of the conductor. It will be appreciated that the several legs and bridging portions may be integral with one another or may be separate components suitably interconnected such as by brazing.

As will be seen from FIGS. 1 and 2, leg 18 extends longitudinally from end portion 12 and, with respect to the direction of bridging portion 24 toward bridging portion 20, leg 18 is twisted counterclockwise 90. Leg 22 extends longitudinally of axis A between the corresponding ends of bridging portions 20 and 24 and, in the direction from bridging portion 24 toward bridging portion 20, is twisted counterclockwise 180. Leg portion 26 extends longitudinally of axis A between bridging portion 24 and end portion 14 and, in the direction from bridging portion 24 toward bridging portion 20, is twisted counterclockwise It will be appreciated, therefore, that leg 22 defines a helical conductor portion and that legs 18 and 26, together, define another helical conductor portion. The helical conductor portions extend longitudinally of axis A and, with respect to the direction from bridging protion 24 toward bridging portion 20, the two helical portions have the same hand of lay or, in other words, are twisted in the same direction relative to axis A. Preferably, the bending or twisting of legs 18, 22 and 26 is uniform, whereby the helical conductor portions at any given location along axis A and transverse thereof are diametrically opposed, as illustrated in FIG. 3.

Bridging portions 20 and 24 are provided, respectively, with openings 28 and 30 coaxial with axis A for longitudinally receiving a workpiece W to be heated. Openings 28 and 30, of course, are peripherally closed to enable coolant circulation through the inductor without leakage at the openings. While openings 28 and 30 are illustrated as being circular it will be appreciated that these openings can have other peripheral contours. The diametrically opposed relationship between the helical conductor portions provides for the rectangular tubular conductor legs to have their narrowest dimension extending radially with respect to axis A and for the leg portions to lie in planes disposed on opposite sides of axis A and in parallel relationship. Preferably, the spacing between the helical conductor portions in the direction perpendicular to the latter planes is substantially uniform throughout the length of the inductor device. The dimension of such spacing will depend in part on the cross-sectional dimension of workpieces to be heated by the inductor, and the spacing will provide for the helical conductor portions to be suitably spaced from the outer surface of a workpiece. to achieve the desired magnetically coupled relationship between the inductor and workpiece.

It will be seen that the geometry of the inductor in FIGS. 1 and 2 provides for current to flow through the helical conductor portions along a helical path and longitudinally of a workpiece positioned therebetween. Accordingly, the magnetic field established between the helical conductor portions and workpiece extends along a corresponding helical path and has a direction along the path transverse to axis A. This advantageously provides for peripheral portions of workpiece W to be substantially uniformly heated as the workpiece moves longitudinally of the inductor and without having to rotate the workpiece relative to the inductor. Such uniform heating is enhanced by providing for the tubular conductor to be rectangular in cross section and positioned such that its dimension in width is bisected by a line extending radially of axis A. This relationship provides for the magnetic field at any given point along the length of the inductor to have a greater peripheral extent with respect to the workpiece than would be the case with a single narrow conductor extending parallel to the workpiece axis. The width dimension of the tubular conductor can of course vary and, preferably, is wider than the cross-sectional dimension of a workpiece to be heated.

While the tubular conductor illustrated in FIGS. 1 and 2 has a width dimension which is flat, it will be appreciated that the conductor could be curved in cross section so as to be concave with respect to axis A. Such a configuration would be desirable for the heating of tubular or circular workpieces in that the lateral side edges of the conductor would be closer to the outer surface of the workpiece than the lateral side edges of the flat conductor.

In use, a workpiece to be heated may be introduced into the inductor device from one of the opposite ends thereof and suitably supported for movement through the inductor and out the opposite ends. Alternatively, the workpiece may be of indeterminate length and progressively advanced through the inductor device for adjacent longitudinal portions of the workpiece, or selected longitudinal portions thereof, to be heated.

Referring now to FIGS. 4 and 5 of the drawing, there is illustrated a further embodiment of an inductor made in accordance with the present invention. The inductor in FIG. 4 is similar to the inductor in FIG. 1, but is defined by a continuous tubular conductor 40 of conductive material, such as copper, which is circular in cross section. Conductor 40 has opposite ends 42 and 44 connectable across a suitable source of alternating current 46, and the tubular conductor provides for the circulation of coolant through the inductor. As in the embodiment of FIG. 1, the inductor has an axis of orientation A coinciding with the axis of workpiece W disposed in magnetically coupled relationship therewith.

Conductor 40 includes, in succession, a leg 48 extending from end portion 42, a bridging portion 50 extending across and under axis A from the corresponding end of leg 48, a leg 52 extending longitudinally of axis A from the corresponding end of bridging portion 50 to the opposite end of the inductor, a bridging portion 54 extending across and over axis A from the corresponding end of leg 52, a leg 56 extending longitudinally of axis A from the corresponding end of bridging portion 54 to the opposite end of the inductor, a bridging portion 58 extending across and over axis A parallel to bridging portion 50, a leg 60 extending longitudinally of axis A from the corresponding end of bridging portion 58 to the opposite end of the inductor, a bridging portion 62 extending across and under axis A parallel to bridging portion 54, and a leg 64 extending longitudinally of axis from the corresponding end of bridging portion 62 to end portion 44 of the conductor.

Legs 52 and 60 of the conductor together define one helical conductor portion, and leg 56 together with legs 48 and 64 define another helical conductor portion. As in the embodiment of FIG. 1, each of the helical conductor portions is twisted to have the same hand of lay relative to a given longitudinal direction from one end of the inductor to the other. More particularly, in the direction from bridging portions 54 and 62 toward bridging portions 50 and 58, the two helical conductor portions are twisted counterclockwise relative to axis A. Preferably, the bending or twisting of the two conductor portions is generally uniform between the opposite ends of the inductor, and the conductor portions each traverse an angular path of 180 between the opposite ends of the inductor.

The adjacent legs of conductor 40 are maintained in suitable spaced relationship by means of insulating spacers 66 disposed therebetween at spaced apart locations longitudinally of the inductor. Further, at any given location along the length of the inductor the helical conductor portions are substantially diametrically opposed as illustrated in FIG. 5, and the axes of the conductor legs of each helical portion lie in a plane perpendicular to a line extending radially of axis A. Moreover, the conductor legs are spaced apart in the plane an equal distance on opposite sides of such a radial line.

As in the embodiment of FIG. I, the inductor geometry shown in FIG. 4 provides for current to flow longitudinally relative to axis A along a helical path, whereby the magnetic field extends along a corresponding helical path and has a direction transverse to axis A.

Bridging portions 50 and 58 at one end of the inductor are suitably contoured in the direction transverse to axis A to cooperatively provide an opening 68 for a workpiece to be heated. Similarly, bridging portions 54 and 62 at the opposite end of the inductor are contoured in the direction transverse to axis A to provide an opening 70 for the workpiece. Openings 68 and 70 preferably are coaxial with respect to axis A and can be of a contour other than the circular contour shown.

In the embodiments illustrated in FIGS. 1 and 4, the opposite ends of the conductor are disposed intermediate the opposite ends of the inductor device. It will be appreciated, however, that many arrangements can be provided for connecting the conductor to a source of alternating current without altering the intended operation of the inductor. One such arrangement is illustrated in FIG. 6 wherein the inductor device is comprised of a conductor formed of rectangular tubing similar to that of conductor 10 illustrated in FIG. 1. In the present embodiment, conductor 80 has opposite ends 82 and 84 disposed at one end of the inductor for interconnection with a suitable source of alternating current 86. As in the previous embodiments, the inductor has an axis of orientation A coinciding with the axis of a workpiece W disposed in magnetically coupled relationship therewith.

Conductor 80 includes one helical conductor portion 88 extending longitudinally of axis A from end portion 82 of the inductor to the opposite end of the inductor, a bridging portion 90 extending across axis A at the corresponding end of helical portion 88, and a second helical conductor portion 92 extending longitudinally of axis A from the corresponding end of bridging portion 90 to end portion 84 of the conductor. Helical conductor portions 88 and 92 are twisted to have the same hand of lay in the direction from one end of the inductor to the other, in the manner described hereinabove with respect to the embodiments of FIGS. 1 and 4, and the bending or twisting provides for the helical portions to transverse an angular path of 180 between the opposite ends thereof. Moreover, helical portions 88 and 92 are related to one another and to axis A so as to be diametrically opposed as described hereinabove in connection with the embodiment of FIG. 1. Bridging portion 90 is porvided with an opening 94 coaxial with axis A to receive a workpiece.

In FIG. 7 there is illustrated a further embodiment of an inductor made in accordance with the present invention. In this respect, the inductor has an axis of orientation A adapted to coincide with the axis of a workpiece W to be inductively heated. The inductor is comprised of a conductor in the form of a continuous hollow tube of conductive material such as copper and which tube is circular in cross section. Conductor 100 has opposite ends 102 and 104 adapted to be interconnected with a suitable source of alternating current 106. Conductor 100 further includes a helical conductor leg 108 extending longitudinally of axis A from end portion 102 to the opposite end of the inductor, a bridging portion 110 extending across and under axis A-from the corresponding end of helical leg 108, a helical conductor leg 112 extending longitudinally of axis A from the corresponding end of bridging portion 102 to the opposite end of the inductor, a bridging portion 114 extending across and under axis A from the corresponding end of helical leg 112, a helical conductor leg l16te the opposite ends of the inductor device. It will be appreciated, however, that many arrangements can be provided for connecting the conductor to a source of alternating current without altering the intended operation of the inductor. One such arrangement is illustrated in FIG. 6 wherein the inductor device is comprised of a conductor 80 formed of rectangular tubing similar to that of conductor 10 illustrated in FIG. 1. In the present embodiment, conductor 80 has opposite ends 82 and 84 disposed at one end of the inductor for interconnection with a suitable source of alternating current 86. As in the previous embodiments, the inductor has an axis of orientation A coinciding with the axis of a workpiece W disposed in magnetically coupled relationship therewith.

In FIG. 7 there is illustrated a further embodiment of an inductor made in accordance with the present invention. In this respect, the inductor has an axis of orientation A adapted to coincide with the axis of a workpiece W to be inductively heated. The inductor is comprised of a conductor 100 in the form of a continuous hollow tube of conductive material such as copper and which tube is circular in cross section. Conductor 100 has opposite ends 102 and 104 adapted to be interconnected with a suitable source of alternating current 106. Conductor 100 further includes a helical conductor leg 108 extending longitudinally of axis A from end portion 102 to the opposite end of the inductor, a bridging portion 110 extending across and under axis A from the corresponding end of helical leg 108, a helical conductor leg 112 extending longitudinally of axis A from the corresponding end of bridging portion 102 to the opposite end of the inductor, a bridging portion 114 extending across and under axis A from the corresponding end of helical leg 112, a helical conductor leg 116 extending longitudinally of axis A from the corresponding end of bridging portion 114 to the other end of the inductor, a bridging portion 118 extending across and over axis A from the corresponding end of helical leg 116, and a helical conductor lcg 120 extending longitudinally of axis A from the corresponding end of bridging portion 118 to end portion 104 of the conductor at the opposite end of the inductor.

Conductor legs 108 and 116 together define a helical conductor portion extending about axis A from one end of the inductor to the other, and conductor legs 112 and 1120 together define another helical conductor portion extending about axis A from one end of the inductor to the other. Bridging portions 110 and 118 are cooperatively contoured in the direction transverse to axis A to provide a workpiece opening, and bridging portion 114 is contoured in the direction transverse to axis A at the corresponding end of the inductor to enable the workpiece to be introduced into the inductor in a manner similar to that described hereinabove in conjunction with the previous embodiments. The helical conductor portions are twisted to have the same hand of lay relative to axis A in a direction from one end of the inductor device to the other. Moreover, each helical portion traverses an angular path about axis A of between the opposite ends of the device, and the helical portions are diametrically opposed along the length of axis A and are geometrically interrelated with one another and with axis A in a manner described hereinabove in connection with the inductor of FIGS. 4 and 5.

It will be appreciated that many embodiments of the present invention may be made and that many changes may be made in the embodiments herein described without departing from the principles of the present invention. For example, where the inductor is defined by a continuous conductor of tubular material having a circular cross section, each helical conductor portion can be comprised of one or a number of tubular legs other than the two legs described herein. Moreover, it will be appreciated that the cross-sectional contour of the conductor can be other than circular and can, for example, be polygonal. Further, it will be appreciated that in those arrangements in which a conductor of rectangular cross section is employed that the helical portions could be defined by two or more rectangular conductor legs disposed side by side rather than one wide conductor leg. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation.

Having thus described my invention, I claim:

1. An inductor for inductively heating an elongated metal workpiece having an axis, said inductor having an axis of orientation coinciding with the axis of a workpiece disposed in magnetically coupled relationship therewith, said inductor comprising a continuous conductor having opposite ends connectable across a source of alternating current, and said conductor including first and second helical portions extending about said axis of orientation, said helical portions being of the same hand of lay and substantially diametrically opposed with respect to said axis of orientation.

2. The inductor according to claim 1, wherein said helical portions each have opposite ends longitudinally spaced apart and circumferentially spaced with respect to said axis of orientation.

3. The inductor according to claim 2, wherein each of said helical portions traverses an angular path of 180 between said opposite ends.

4. The inductor according to claim 1, wherein said conductor is a tubular conductor of rectangular cross section disposed with the smallest dimension of said cross section extending in the direction of said axis of orientation.

5. The inductor according to claim 4, wherein said first and second helical portions have corresponding first ends and said conductor further includes a bridging portion extending across said axis of orientation at said corresponding ends, said bridging portion having a workpiece receiving opening therethrough coaxial with said axis of orientation.

6. The inductor according to claim 5, wherein said first and second helical portions have corresponding second ends and said conductor further includes a second bridging portion extending across said axis of orientation at said second ends, said second bridging portion having a workpiece receiving opening therethrough coaxial with said axis of orientation.

7. The inductor according to claim 6, wherein said helical portions each traverse an angular path of 180 between the first and second ends thereof.

8. The inductor according to claim 7, wherein one of said first and second helical portions has terminal ends between said first and second ends thereof, said terminal ends defining said opposite ends of said inductor.

9. The inductor according to claim 1, wherein said conductor is tubular in cross section, said helical portions of said conductor each including at-least two portions of said tubular conductor disposed adjacent one another and generally parallel in the direction perpendicular to said axis of orientation.

10. The inductor according to claim 9, wherein said helical portions each have opposite ends longitudinally spaced apart and circumferentially spaced with respect to said axis of orientation.

11. The inductor according to claim 10, wherein each of said helical portions traverses an angular path of between said opposite ends.

12. The inductor according to claim 11, wherein said tubular conductor is circular in cross section.

13. The inductor according to claim 9, wherein said first and second helical portions have corresponding opposite ends and said conductor further includes bridging portions extending across said axis of orientation at corresponding ones of said opposite ends, at least a portion of each of said bridging portions being spaced radially from said axis of orientation a sufficient distance for said inductor to receive a progressive workpiece.

Claims

3. The inductor according to claim 2, wherein each of said helical portions traverses an angular path of 180* between said opposite ends.

7. The inductor according to claim 6, wherein said helical portions each traverse an angular path of 180* between the first and second ends thereof.

9. The inductor according to claim 1, wherein said conductor is tubular in cross section, said helical portions of said conductor each including at least two portions of said tubular conductor disposed adjacent one another and generally parallel in the direction perpendicular to said axis of orientation.

11. The inductor according to claim 10, wherein each of said helical portions traverses an angular path of 180* between said opposite ends.