US3067308A - Induction heating apparatus - Google Patents

Induction heating apparatus Download PDF

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Publication number
US3067308A
US3067308A US39540A US3954060A US3067308A US 3067308 A US3067308 A US 3067308A US 39540 A US39540 A US 39540A US 3954060 A US3954060 A US 3954060A US 3067308 A US3067308 A US 3067308A
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United States
Prior art keywords
coil
section
workpiece
taps
heating
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Expired - Lifetime
Application number
US39540A
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English (en)
Inventor
Edward F Mcbrien
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ohio Crankshaft Co
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Ohio Crankshaft Co
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Publication date
Application filed by Ohio Crankshaft Co filed Critical Ohio Crankshaft Co
Priority to US39540A priority Critical patent/US3067308A/en
Priority to CH749161A priority patent/CH377016A/fr
Priority to DEO8130A priority patent/DE1179315B/de
Application granted granted Critical
Publication of US3067308A publication Critical patent/US3067308A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
    • H05B6/101—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces
    • H05B6/103—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces multiple metal pieces successively being moved close to the inductor
    • H05B6/104—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces multiple metal pieces successively being moved close to the inductor metal pieces being elongated like wires or bands
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating

Definitions

  • This invention pertains to the art of induction heating apparatus and more particularly to an induction heating coil assembly capable of producing variable temperature patterns to accommodate the requirements of workpieces of different types and shapes.
  • a heating coil having a length great enough to accommodate the longest workpiece which is to be heated.
  • the coil has a constant diameter and pitch along its length and is provided with a tap at every point where the load cross-section may change or the specified temperature may change for the expected types and sizes of workpieces.
  • a second coil called a control coil, is also constructed having the same number of taps as the heating coil. its length, diameter, number of turns and other particulars may be the same as, or dilferent from, the heating coil as convenience dictates.
  • the corresponding taps on the two coils are then connected in parallel. When a voltage is applied to the two coils in parallel, the current will divide according to the ratio of the impedances of the individual coil sections.
  • the current in any short section of the heating coil may be varied by changing the impedance of the matching section of the control coil.
  • This may be easily accomplished by inserting magnetically permeable material, such as powdered iron slugs, into the sections of the control coil where the impedance is to be raised or low resistivity conducting material where the impedance is to be lowered.
  • a change in impedance can, of course, also be achieved by varying the cross-sectional area of the powdered iron slug or low resistivity conducting material disposed within the control coil, as the case may be.
  • the dimensions and location of the inserts within the control coil are determined for a given workpiece, they can either by made into a long rod to be associated with the part, or the locations can be merely noted and the same inserts used for several parts.
  • the control coil is not required to carry currents as large as in the tent O "ice heating coil. If 10% of the current is diverted to the control coil, the power in the load will be reduced to ap proximately of its former value. Assuming that the final temperature is proportional to the power, this will reduce the final load temperature, for example, from 2000 F. to 1600 F.
  • FIGURE 1 is an illustration of one embodiment of the invention wherein a varying heat pattern is produced on a workpiece or" constant cross-section by means of a control member of low resistivity material in the control coil;
  • FIGURE 2 is an illustration of another embodiment of the invention wherein the heating pattern of FIGURE 1 is again produced in a workpiece of constant cross-section, but in this case a control member of magnetically permeable material is employed in the control coil; and
  • FEGURE 3 is an illustration of another embodiment of the invention wherein a uniform heating pattern is produced over the surface of a workpiece of variable crosssection by means of a control member of low resistivity conducting material in the control coil.
  • a heating coil Til and a control coil 12 which, for purposes of explanation, has the same length, diameter and pitch as the heating coil itl. Both coils in and 12 are connected in parallel across a source of alternating current voltage 14, substantially as shown. Connected in shunt with source 14 is the usual power factor-correcting capacitor 16. The coil 16 has taps A through I which are connected to corresponding points A through I on the control coil 12. In this manner, each coil is divided into successive short sections which are connected in parallel.
  • control member 20 Disposed within heating coil 10 is a workpiece lit, and within the control coil 12 is a control member 20 which may be of low electrical resistivity, or high electrical resistivity, or magnetically permeable material depending on the desired heat pattern in the workpiece 18.
  • the control member 21 is of a low resistivity conducting material, such as copper.
  • the workpiece 18 and control member 20 may remain stationary within their respective coils during a heating operation, or they may both be passed through the coil sections progressively as by means of hydraulic cylinders 22 and 24 which are connected to the ends of the workpiece and control member through fixtures 24 and 2d respectively.
  • portion 23 of the control member 20 has a large cross-sectional area. Since it is of low resistivity conducting material, the im pedance in this section of coil 20 will be lowered so that a larger amount of the current will be diverted through control coil 12 between its left end and tap B, and the depth of heating produced in the workpiece between its left end and tap B will be relatively shallow. Between taps B and D, the cross-sectional area of the control member 29 decreases as at 30.
  • the impedance in the section of coil 12 between taps C and D increases so that a larger proportion of the current is diverted to the section of coil 10 between taps B and D to increase the depth of heating in this portion of the workpiece 18.
  • the cross-sectional area of the control member 20 again increases as at 32 so that the depth of heating between taps D and F on coil 10 decreases.
  • the cross-sectional area of the control member 20 is very small as at 34, so that the depth of heating between taps F and G on heating coil 10 again increases.
  • the cross-sectional area of the low resistivity conducting material increases as at 35 to de crease the depth of heating on the workpiece between tap G and the right end of heating coil 10.
  • he control member 2t ⁇ need not, of course, be of the same material throughout, nor of the same diameter.
  • the material between the left end of coil 12 and the tap B could be low resistivity material to decrease the impedance of that section; while that between taps B and D could be magnetically permeable material to increase the impedance of that section to a maximum and produce a maximum depth of heating between taps B and D on heating coil 10.
  • high resistivity material can be used between certain taps which will produce a depth of heating between that of the low resistivity material and the magnetically permeable material.
  • control coil 12 is the same as that of the heating coil for the embodiment shown in FIGURE 1, the pitch, diameter, length and other particulars of the control coil may be different, the only requirement being that the apparatus be designed to produce the correct impedances across the various sections of the control coil to effect the proper heating pattern in the workpiece 18.
  • the pitch of coil 12 may vary along its length just so long as the proper heating pattern is produced in the workpiece.
  • control rnember 20 may be all in one piece as shown or may comprise separate iron or copper slugs, for example, which are positioned in the control coil 12 to achieve the desired heating pattern.
  • FIGURE 2 another embodiment of the invention is shown which again includes the heating coil and the control coil 12, both of which are divided into sections connected in parallel.
  • the control member 20 is of magnetically permeable material throughout so that its configuration is reversed with respect to the dummy load of FIGURE 1 which was formed of low resistivity conducting material.
  • the diameter of the magnetically permeable material is reduced to decrease the impedance of the control coil between the left end and tap B whereby a larger portion of the current will be shunted through this section of the control coil, and a relatively shallow heating pattern will be achieved in the workpiece 18 between the left end of the heating coil and tap B.
  • the diameter of the magnetically permeable material increases so that the impedance of this section of the control coil increases to increase the depth of heating between taps B and D on the heating coil 10.
  • the diameter of the magnetically permeable material of load 20 decreases to decrease the depth of heating in this section of the workpiece 18, and so on.
  • FIGURE 3 another embodiment of the invention is shown which again includes the heating coil 10 and control coil 12.
  • the workpiece has a variable cross-section along its length while the control member 20 is formed from low resistivity conducting material. It will be assumed that it is desired to produce a uniform heating pattern over the length of the workpiece 18. Consequently, between the left end of control coil 12 and tap A the diameter of the control member 20 is decreased to increase the impedance of that section. In this manner, the magnetic field between the left end of heating coil 10 and tap A will be increased to accommodate the reduced diameter section of the workpiece 18. Between taps A and D, the diameter of the control member increases to reduce the impedance of control coil between these taps and thereby decrease the strength of the magnetic field between taps A and D on heating coil 10.
  • the diameter of the workpiece 18 increases between taps A and D, the depth of heating on its surface will be the same as that on the section between the left end of the coil and tap A due to the fact that a larger proportion of the current has been shunted through the control coil between taps A and D.
  • the diameter of the control member 20 again decreases to increase the impedance in the control coil between these points and divert a larger proportion of the current to the heating coil between taps D and H on the control coil. This will, of course, increase the strength of the magnetic field between the aforementioned taps on the control coil to produce the required depth of heating on the reduced diameter portion of the workpiece 18 between points D and H.
  • the diameter of the control member increases between taps H and I on the heating coil 10
  • the diameter of the control member also increases between taps H and I on the control coil 20.
  • the diameter of the workpiece and that of the control member decrease bet-ween taps I and I and the ends of the respective coils.
  • control member 2% could be of magnetically permeable material rather than low resistivity conducting material in which case the shape of the control member 20 will be exactly opposite to that of the workpiece 18 to obtain a uniform heating pattern over the length of the workpiece.
  • the invention thus provides a means for achieving variable heating patterns in workpieces of different shapes and sizes within a coil of constant length, diameter and pitch.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a generally constant diameter and constant pitch throughout its length, a second induction coil section having a similar number of turns, taps spaced along the length of said first coil section, corresponding taps spaced along the length of the second coil section with the number of taps on the second coil section being equal to the number on the first coil section and the spacing between successive taps on the second coil section being proportional to the spacing between successive corresponding taps on the first coil section, means connecting each tap on the first section to its corresponding tap on the second section, means for connecting said first and second coil sections in parallel across a source of alternating current voltage, and a control member of magnetically permeable material having a variable diameter along its length disposed within said second coil section whereby the impedance presented between successive pairs of taps on the second coil section will vary to produce variable flux densities between successive pairs
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a generally constant diameter and constant pitch throughout its length, a second induction coil section having a like number of turns, taps spaced along the length of said first coil section, corresponding taps spaced along the length of the second coil section with the number of taps on the second coil section being equal to the number on the first section and the spacing between successive taps on the second coil section being proportional to the spacing between successive corresponding taps on the first coil section, means connecting each spam on tap on the first section to its corresponding tap on the second section, means for connecting said first and second coil sections in parallel across a source of alternating current voltage, and a control member of low resistivity conducting material having a variable diameter along its length disposed within said second coil section whereby the impedance presented between successive pairs of taps on the second coil section will vary to produce variable fiux densities between successive
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a constant diameter and constant pitch throughout its length, a second induction coil section, separate portions on said first coil defined by taps spaced along the length of said first coil section, a corresponding number of separate portions on said second coil defined by taps spaced along the length of the second coil section, each tap on the first coil section connected to a corresponding tap on the second coil section, the separate portions of the first coil section connected in parallel with the corresponding separate portions of the second coil section, said first and second coil sections connected in parallel across a source of alternating current voltage, and core member in said second coil section for varying the reluctance presented to the magnetic field produced by the second coil section along its length whereby the impedance presented between successive taps on the second coil section will vary to produce variable magnetic fields between corresponding successive taps on the first coil section.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a constant diameter and constant pitch throughout its length, a second induction coil section, separate portions of said first coil section connected in parallel with separate portions of said second coil section, said coil sections connected in parallel across a source of alternating current voltage and metallic members magnetically coupled with the portions of said second coil for varying the reluctance presented to the magnetic field produced by the second coil section along said portions of said second coil whereby the magnetic fields produced by the various portions of said first coil section will vary.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of the workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, a second induction coil section, separate portions of said first coil section connected in parallel with separate portions of said second coil section, said coil sections connected in parallel across a source of alternating current voltage, and metallic members magnetically coupled with the portions of said second coil for varying the reluctance presented to the magnetic field produced by the second coil section along said portion of said second coil whereby the magnetic field produced by the various portions of said first coil section will vary.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a constant diameter and constant pitch throughout its length, a second induction coil section having a constant diameter and constant pitch throughout its length, separate portions of said first coil section connected in parallel with separate portions of said second coil section, said coil sections connected in parallel across a source of alternating current voltage, and a control member having variable reluctance portions along its length and being disposed within said second coil section, said variable reluctance portions magnetically coupled with the separate portions on said second coil Whereby the impedance presented to successive portions of the second coil section will vary resulting in variable magnetic fields produced by successive portions of said first coil section.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section having a constant diameter and constant pitch throughout its length, a second induction coil section, separate portions of said first coil section connected in parallel with separate portions of said second coil section, said coil sections connected in parallel across a source of alternating current voltage, control member having variable reluctance portions, said reluctance portions corresponding to the desired flux pattern and means for passing said workpiece through the first coil section while simultaneously passing said control member through the second coil section.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, a control member, a second induction coil section adapted to receive said control member, said control member having a variable reluctance along its length, separate portions of said first coil section connected in parallel with separate portions of said second coil section, said coil sections connected in parallel across a source of alternating current voltage, and means for feeding said workpiece axially through said first coil section while simultaneously feeding the control member axially through said second coil section.
  • An induction coil arrangement adapted to produce a variable flux density pattern along the length of a workpiece comprising, in combination, a first induction coil section adapted to receive a workpiece to be heated, said first coil section being divided into a number of successive separate portions by a number of taps, adjacent taps connected to separate control coil portions, said control coil portions connected in parallel with said separate coil portions, said control coil portions and said first coil section connected in parallel with a source of alternating current voltage, and a metallic member magnetically coupled with said control coil portion to vary the reluctance of said control coil portions, said metallic member having diiferent reluctance portions magnetically coupled with difierent control coil portions.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • General Induction Heating (AREA)
US39540A 1960-06-29 1960-06-29 Induction heating apparatus Expired - Lifetime US3067308A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US39540A US3067308A (en) 1960-06-29 1960-06-29 Induction heating apparatus
CH749161A CH377016A (fr) 1960-06-29 1961-06-27 Appareil de chauffage par induction
DEO8130A DE1179315B (de) 1960-06-29 1961-06-28 Vorrichtung zum induktiven Erhitzen von langgestreckten Werkstuecken

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US39540A US3067308A (en) 1960-06-29 1960-06-29 Induction heating apparatus

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US3067308A true US3067308A (en) 1962-12-04

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US39540A Expired - Lifetime US3067308A (en) 1960-06-29 1960-06-29 Induction heating apparatus

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US (1) US3067308A (fr)
CH (1) CH377016A (fr)
DE (1) DE1179315B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3485657A (en) * 1967-03-14 1969-12-23 Lfe Corp Carbon coating employing electromagnetic field
US3612805A (en) * 1970-04-27 1971-10-12 Inductotherm Corp Inductive heating-cooling apparatus and method

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1986353A (en) * 1931-09-21 1935-01-01 Ajax Electrothermic Corp Induction furnace method and apparatus
US2383992A (en) * 1943-02-25 1945-09-04 Fed Telephone & Radio Corp Induction heating apparatus and flux field control thereof
US2452197A (en) * 1945-03-22 1948-10-26 Ajax Electrothermic Corp Induction furnace for variable heat patterns
US2470443A (en) * 1944-07-21 1949-05-17 Mittelmann Eugene Means for and method of continuously matching and controlling power for high-frequency heating of reactive loads
US2490104A (en) * 1945-04-12 1949-12-06 Ohio Crankshaft Co Apparatus for equalized induction heating of workpieces

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1074781B (de) * 1960-02-04 INNOCENTI Societä Generale per rindustria Metallurgica e Meccanica, Mailand (Italien) Vorrichtung zum Erhitzen und Trennen von in Bewegung befindlichem Walzgut

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1986353A (en) * 1931-09-21 1935-01-01 Ajax Electrothermic Corp Induction furnace method and apparatus
US2383992A (en) * 1943-02-25 1945-09-04 Fed Telephone & Radio Corp Induction heating apparatus and flux field control thereof
US2470443A (en) * 1944-07-21 1949-05-17 Mittelmann Eugene Means for and method of continuously matching and controlling power for high-frequency heating of reactive loads
US2452197A (en) * 1945-03-22 1948-10-26 Ajax Electrothermic Corp Induction furnace for variable heat patterns
US2490104A (en) * 1945-04-12 1949-12-06 Ohio Crankshaft Co Apparatus for equalized induction heating of workpieces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3485657A (en) * 1967-03-14 1969-12-23 Lfe Corp Carbon coating employing electromagnetic field
US3612805A (en) * 1970-04-27 1971-10-12 Inductotherm Corp Inductive heating-cooling apparatus and method

Also Published As

Publication number Publication date
DE1179315B (de) 1964-10-08
CH377016A (fr) 1964-04-30

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