WO1992003026A1 - Appareil et procede de trempe par induction de pieces de machine, comprenant la regulation precise de la puissance emise - Google Patents

Appareil et procede de trempe par induction de pieces de machine, comprenant la regulation precise de la puissance emise Download PDF

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Publication number
WO1992003026A1
WO1992003026A1 PCT/US1991/005285 US9105285W WO9203026A1 WO 1992003026 A1 WO1992003026 A1 WO 1992003026A1 US 9105285 W US9105285 W US 9105285W WO 9203026 A1 WO9203026 A1 WO 9203026A1
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WO
WIPO (PCT)
Prior art keywords
signal
power
input
phase angle
activation
Prior art date
Application number
PCT/US1991/005285
Other languages
English (en)
Inventor
John M. Storm
Spencer L. Gibbs
Original Assignee
Contour Hardening, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US07/563,398 external-priority patent/US5053596A/en
Application filed by Contour Hardening, Inc. filed Critical Contour Hardening, Inc.
Priority to KR1019930700353A priority Critical patent/KR970011547B1/ko
Priority to DE69118699T priority patent/DE69118699T2/de
Priority to AU83092/91A priority patent/AU649062B2/en
Priority to JP3513384A priority patent/JP2885511B2/ja
Priority to EP91914109A priority patent/EP0542813B1/fr
Priority to BR919106736A priority patent/BR9106736A/pt
Publication of WO1992003026A1 publication Critical patent/WO1992003026A1/fr

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Classifications

    • 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
    • H05B6/06—Control, e.g. of temperature, of power
    • 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
    • H05B6/36—Coil arrangements
    • H05B6/40—Establishing desired heat distribution, e.g. to heat particular parts of workpieces
    • H05B6/405—Establishing desired heat distribution, e.g. to heat particular parts of workpieces for heating gear-wheels

Definitions

  • the present invention relates generally to the technology of induction heating and more particularly to the use of induction heating devices for case-hardening of machine components such as gears.
  • Machine components such as gears, splined shaves and sprockets are frequently subjected to high torque loads, frictional wear and impact loading. Gears of this type are typically used in power transmission drive trains.
  • An apparatus and method for induction-hardening of such machine components is disclosed in U.S. Patent No. 4,845,328 to Storm et al., the contents of which are hereinafter incorporated by reference.
  • the Storm et al. patent and this application are both owned by the same assignee. Contour Hardening Inc., of Indianapolis, Indiana.
  • a known device for gear teeth hardening includes a dual-frequency arrangement for induction heating wherein a low frequency current is used for preheating the gear teeth and then a high frequency (Radio Frequency) current is then used for final heating prior to quench hardening of the gear teeth.
  • the dual frequency induction hardening concept is described in the article "Induction Gear Hardening by the Dual-Frequency Method" which appeared in Heat Treating Magazine, Vol. 19, No. 6, published in June, 1987.
  • dual-frequency heating employs both high and low frequency heat sources.
  • the gear is first induction heated with a relatively low frequency source (3-10 kHz), providing the energy required to preheat the mass of the gear teeth.
  • This step is followed immediately by induction heating with a high-frequency source which typically ranges from 100-300 kHz depending on the gear size and diametral pitch of the gear teeth.
  • the high-frequency source will rapidly final heat the entire tooth contour surface to a case hardening temperature.
  • the gears are then quenched to a desired hardness and tempered.
  • Induction heating is the fastest known way of heating an iron alloy gear. In some applications a pre-heat low frequency heat process precedes the final heat RF heating.
  • Heating times for the high-frequency RF heating step typically range from 0.10 to 2.0 seconds.
  • the gear is mounted on a spindle and spun while positioned within the induction heating coil.
  • a quick pulse of power is supplied to the induction heating coil which achieves an optimum final heat of the gear teeth.
  • the piece is manually or automatically moved into a water-based quench. Because induction hardening puts only the necessary amount of heat into the part, case depth requirements and distortion specifications are met with great accuracy.
  • the part characteristics dictate the optimum design of both the induction heating coil or coils and the most appropriate machine settings.
  • the amount of time that the high-frequency power signal is supplied to the induction heating coil to generate the final heat is a most critical parameter.
  • the exact amount of heat required to harden the gear is directly related to the precise amount of time that the power signal is supplied to the induction heater coil.
  • the first system utilizes what is known in the art as a "solid state" generator approach wherein high power amplification devices such as transistors, be they bipolar or CMOS, are used in the high-frequency RF generator to supply a high-frequency oscillator signal to the induction heater coil.
  • high power amplification devices such as transistors, be they bipolar or CMOS
  • An alternate approach is to use a vacuum tube RF generator and utilize thyristor type devices to switch power on and off to the high-frequency, high power vacuum tube oscillator circuit. The output of either oscillator circuit is coupled to the induction heater coil by way of a transformer.
  • a vacuum tube RF generator typically receives its input power subject to the on/off timing characteristics of thyristor devices such as silicon controlled rectifiers (SCR's) which are also known in their JEDEC description as reverse blocking triode thyristors.
  • SCR's silicon controlled rectifiers
  • the power delivery timing variance created by the SCR is intrinsic in the operation of such devices.
  • a method and apparatus for more accurately controlling the timed power output of a silicon controlled rectifier power supply is needed for accurately controlling the power signal supplied to induction heater coils used in case hardening devices.
  • An apparatus for induction hardening machine components with precise control of power output comprises an AC power source for producing an AC power signal, zero-crossing detector means connected to the AC power source for detecting zero crossings of the AC power signal and producing a zero-crossing signal corresponding thereto, a high-frequency generator having a power input and an output for producing a high-frequency, high-power signal in response to a signal supplied to the power input, a high-frequency induction heater coil sized to fit the gear and connected to the output of the generator, the coil generating a high-frequency electrical signal through the gear, thyristor power switching means having an activation input, a power input connected to the AC power source, and a power output, the power switching means producing an AC power signal at the power output in response to a signal supplied to the activation input, and processor means, connected to the zero-crossing detector and the thyristor power switching means activation input, for computing activation times and supplying a corresponding activation signal to the activation input, the processor
  • An induction-hardening apparatus include an AC power source for producing an AC power signal, phase detector means for detecting a predetermined phase angle of the AC power signal, the detector means producing a detector signal when the predetermined phase angle is detected, a high-frequency generator means having a power input and a power output for producing a high-frequency high-power signal at the power output in response to a power signal supplied to the power input, a high-frequency induction heater coil connected to the power output, the heater coil emitting a high-frequency electromagnetic signal in response to the high-frequency high-power signal, power switching means connected to the AC power signal, the power switching means including an activation input, the power switching means supplying the AC power signal to the power input in response to receiving a signal at the activation input, and timer circuit means responsive to the detector signal for supplying an activation signal of a predetermined duration to the activation input.
  • a method for precisely controlling power supplied to an induction-hardening apparatus which includes an AC power source, a high-frequency generator having a power input, and a high-frequency induction heater coil, the method comprises the steps of, detecting a predetermined phase angle of the AC power source, connecting the AC power source to the power input of the high-frequency generator for a predetermined period of time in response to detecting the predetermined phase angle.
  • An induction-hardening apparatus for precisely controlling power delivery of an high-frequency induction heater coil, comprises an AC power source for producing an AC power signal, first circuit means for producing a first signal in reponse to detecting a predetermined phase angle of the AC power signal, switch means for producing a start signal when the switch means is activated, second circuit means responsive to simultaneous occurrence of the first signal and the start signal for producing a predetermined duration activation signal in response thereto, high-frequency generator means having a power input for producing a high-frequency high-power signal in response to a signal supplied to the power input, and power switching means connected to the AC power signal and supplying the AC power signal to the high-frequency generator in response to the predetermined duration activation signal.
  • One object of the present invention is to provide an improved induction hardening machine. Another object of the present invention is to provide a method for more accurately controlling the power signal supplied to induction heater coils of an induction hardening machine to precisely control the power supplied and thus the heating of a gear during case hardening. Another object of the present invention is to provide a more accurate high power switching circuit so that the total power output signal can be controlled with greater precision.
  • FIG. 1 is a block diagram of a typical embodiment of an induction-hardening system according to the present inventio
  • FIG. 2 is a timing diagram showing variations in the active or "on" state of an SCR with respect to certain input conditions applied to the gate of the SCR.
  • FIG. 3 is a graph depicting a deviation in power output signals produced by power switching SCR circuits of the present invention as compared with prior art devices.
  • FIG. 4 is a block diagram of another embodiment of an induction-hardening system according to the present invention.
  • Switch SW1 provides an activation signal to the system processor 12 for invoking or initiating the case hardening of a gear.
  • System processor 12 is programmed by the user with timing parameters for controlling the power signal supplied to the induction heater coil.
  • Processor 12 supplies an on/off power switching signal to power switching SCR circuit 14.
  • System processor 12 receives a zero crossing indicator input signal from zero crossing detector 16.
  • One phase 6, from 36 high voltage power source 18 is supplied to an input of zero crossing detector 16.
  • the 36 high-voltage power source 18 supplies three phases of high voltage power to the power switching SCR circuits 14.
  • Power switching SCR circuits 14 when activated, supply either half-wave or full-wave AC power signals to the primary windings of step-up transformer 22.
  • Transformer 22 steps up the AC power signals 6. , b ⁇ and 6_, typically 480 volts three-phase signals, to a voltage level sufficiently high that rectifier and filter 24 produces a 24,000 volts DC signal at its output.
  • the 24,000 volts DC signal at the output of rectifier filter 24 is the power source for a vacuum tube type high-energy RF oscillator 26.
  • the output of the high-energy oscillator 26 is AC coupled to the induction heater coil 28 via windings 29.
  • Induction heater coil 28 supplies a case-hardening heating signal to the gear teeth of gear 30 when an RF signal is supplied to its input.
  • the components 22, 24 and 26 of the system 10 are part of RF generator 20 which is a high-frequency, high-power RF generator.
  • the RF generator 20 is an off-the-shelf system supplied by Pillar Industries, Inc., N92 W15800 Megal Drive, Menomonee Falls, Wisconsin 53051.
  • the RF generator 20 is referred to as a "450/600 kilowatt RF Generator".
  • gear 30 dictates the precise amount of time that power switching SCR circuits 14 are "turned on” by system processor 12 in order to produce the appropriate case hardening result. In some instances, the amount of time that the SCR circuits 14 are turned on is as small a time period as 0.10 seconds to accomplish the desired heating and case hardening of gear 30. With this condition in mind, it is easy to see why the prior art devices which did not include zero crossing detector 16, were unable to accurately control the amount of power signal or total power supplied to the induction heater coil 28.
  • the system processor 12 of the present invention typically includes a computer having adequate memory and computing capability, and a programming input device such as a CRT/keyboard device. Additionally the processor 12 has mass storage devices such as floppy or hard disk drives for use in storing and recalling control programs. Operationally speaking, an operator programs the system processor 12 through a keyboard for a particular "on-time” or heat time which is the exact time that the power switching SCR circuits 14 shall be turned on to supply a fixed quantity of high-frequency power signal to the induction heater coil 28.
  • the system processor 12 will compute a complement value for the specific "on time” which is equal to the difference between the "on time” divided by 8.33 milliseconds (the period of a 60 Hz waveform) . The remainder from this calculation is subtracted from 8.33 milliseconds to produce a time value which is the delay time that the processor 12 should delay after detecting a zero crossing of the 60 Hz signal present at the input of detector 16 prior to activating the SCR circuits 14 to supply power to the RF generator.
  • the time delay calculation is designed so that the end of the on or conducting period for the SCR devices corresponds exactly with or just prior to a zero crossing of the power signal 6, supplied to the input of zero crossing detector 16.
  • the SCR's which remain in the conducting state so long as the anode to cathode terminals are forward biased, will not remain on a substantial period of time after the system processor 12 signals the SCR circuits 14 to turn off by deactivating the input to the circuits 14.
  • SCR circuits 14 may supply a half-wave or full-wave 36 output signal to the transformer 22. If the signal is half-wave in nature, the divide-by factor described above (8.33 milliseconds) becomes 16.67 milliseconds and the remainder is subtracted from 16.67 milliseconds. Additionally, negative-slope zero crossovers must be detected to determine the appropriate timing reference points for activating a half-wave output SCR circuit. Thus, the "on time” desired is divided by 16.67, and any remainder therefrom is subtracted from 16.67. The result of the subtraction process is the delay period required after a negative-slope zero crossover of the power signal prior to activating the SCR circuits 14 for half-wave outputs therefrom. Although the other phases (6 radical and 6 soir) of the SCR circuits 14 may remain "on” after the input to circuits 14 is deactivated, the above technique produces an accurate and repeatable power output from SCR circuits 14,
  • Curve 40 is a standard sine wave power signal representing the 6, signal at the input of detector 16. Curve 40 is a 60 Hz signal plotted with respect to time. Curves 42 and 46 represent the signal produced by the system processor 12 and supplied to the gate input of the SCR circuits 14. Curves 42 and 46 are the "on time” desired to produce a predetermined amount of heat in a particular gear 30 to be induction hardened.
  • the circuits 14 are activated or caused to supply a power signal to generator 20 at the point in time which is the off-on transition of the curve 42.
  • the signal changes from the "on” state to the "off” state.
  • the precise timing of the on-off transition does not occur near a zero crossing of curve 40. Since the activation signal represented by curve 42 does not return to the "off” state until after the zero crossing at time T_, the power signal which is supplied to the RF generator 20, represented by curve 44, is continuously “on” until time T , which may be as much as 8.33 milliseconds after the on-off transition of curve 42.
  • the on signal produced by system processor 12 begins at time T., and continues until time T n , the total power signal supplied to the RF generator will last from time T " ⁇ B until time T culinary on the graph, for a total time period of
  • the system according to the present invention computes a time delay beyond a zero crossing (here the zero crossing at T_) for turning on the SCR circuits 14 so that the SCR activation signal, represented by curve 46, will change from the "on" state to the "off” state at or just prior to a zero crossing of curve 40.
  • the system processor 12 will compute a time T_ which corresponds to the desired "on time” T, divided by 8.33 milliseconds and subtract the remainder from 8.33 milliseconds to produce time T_ . Then, the system processor delays activating SCR circuits 14 a period of time T_ after a zero crossing so that the activation curve 46, which coincidentally is exactly equal in "on time” duration to curve 42, changes from the "on” to the "off” state at time T_, which corresponds with a zero crossing of the power signal curve 40.
  • FIG. 3 a graph of the power output of the RF generator 20 is shown.
  • the maximum power output of the generator 20, represented by curve 50 can be adjusted vertically to achieve higher or lower total instantaneous power output.
  • the variance in "on time”, represented by times T, and T Formula, as a result of the intrinsic functionality of SCR circuits is shown at the bottom of the graph. If the SCR circuits remain on for a length of time T ? as opposed to T, , which is the desired "on time”, the additional power represented by the shaded portion 52 underneath the curve 50 is supplied to the heater coil 28 in addition to the actual desired power, represented by the unshaded portion underneath the curve 50 and extending up to the end of time Tl. The additional amount of power supplied to the induction heater coil 28 causes excessive heating of the gear 30.
  • timing variations make for greater variations in the case hardening process, particularly when the "on time" Tl is approximately 0.10 seconds.
  • the maximum difference between times T2 and Tl can be as much as 8.33 milliseconds, and thus the power represented by area 52 can represent as much as 8-10% difference in power supplied to the induction heater coil 28 when a 0.10 second power signal is desired for heater coil 28.
  • Another recognized fact is that once the gear 30 has been heated, the additional heating time represented by the area 52 can seriously increase the heat of the gear, as the heat transfer properties of the gear are non-linear and cause heat to transfer deeper into the gear face once the gear is heated around the perimeter.
  • Switch SW2 provides a reset/start signal to single pulse timer circuit 116.
  • AC power source 118 supplies an AC signal to phase angle detector 112 and power switching devices 114.
  • Phase angle detector 112 provides a series of pulses to an input of single pulse timer circuit 116. Each pulse from detector 112 corresponds to the detection of a predetermined phase angle of the AC power signal from power source 118.
  • single pulse timer circuit 116 is triggered or activated by the next pulse from detector 112 to produce a pulse or signal having a predetermined duration. The predetermined duration pulse enables the power switching devices 114.
  • phase angle detector 112 provides a phase detector me ⁇ ns for detecting a predetermined phase angle in the power si !al from AC power source 118.
  • the RF generator 120 receives a power signal from the power switching devices 114 and in response thereto supplies a high frequency, high power sic 1 to the induction heater coil 128 via windings 129.
  • Winumgs 129 provide impedance matching between the output of the RF generator 120 and the induction heater coil 128. Single-phase and multi-phase power supplies are contemplated.
  • the phase angle detector 112 is implemented using a triac phase angle controller Part No. TDA1185A manufactured by Motorola Incorporated of Phoenix, Arizona.
  • the TDA1185A device is programmable to produce an output signal corresponding to detection of a predetermined phase angle of the AC signal. This predetermined phase angle is variable with the TDA1185A device in accordance with an external set voltage representing the conduction angle desired.
  • TDA1185A device Since the TDA1185A device detects firing angles only on the positive half of the AC signal, should a firing angle on the negative half of the AC signal be desired, an inverting operational amplifier may be inserted between the AC power source and the phase angle detector 112 to invert the AC signal, and thus provide an input signal to the phase angle detector 112 such that activation in the negative half of the AC signal may occur.
  • Signal pulse timer circuit 116 is implemented using a retriggerable monostable multivibrator integrated circuit, part No. 74LS123 manufactured by Texas Instruments.
  • the 74LS123 is a rising-edge triggered device and thus the pulses produced by the phase angle detector 112 can be used to trigger the production of an output pulse from the timer circuit 116.
  • the signal produced by switch SW2 provides a retrigger, enable or rearming signal to the timer circuit 116. Since the 74LS123 device can be configured to produce an output pulse from less than 1 millisecond to a very large time duration, such as hours, the combination of the phase angle detector 112 and the timer circuit 116 provides infinitely variable control of the timing functions necessary to activate power switching devices 114 in accordance with the previously described conditions calling for a supply of a specific duration power signal to the RF generator 120.
  • Optional control signals provide phase angle selection and pulse width duration signals to detector 112 and circuit 116, respectively.
  • the phase angle control signal present on signal path 134 and supplied to an input of detector 112, provides phase angle selection information to detector 112.
  • detector 112 In response to the signal on signal path 134, detector 112 produces an output pulse corresponding in time to the occurrence of the desired phase angle established by the signal on signal path 134.
  • the duration control signal present on signal path 132 controls the time duration of the pulse produced by circuit 116.
  • the signal on signal path 132 is typically implemented via a potentiometer/capacitor combination establishing a decaying signal well known with such circuits.
  • the device 110 of FIG. 4 includes several components which are identical with components of the device 10 of FIG. 1.
  • the AC power source 118 corresponds with the three-phase high voltage power source 18
  • power switching devices 114 correspond with power switching SCR circuits 14
  • RF generator 120 corresponds with RF generator 20
  • induction heater coil 128 corresponds with induction heater coil 28
  • gear 130 corresponds with gear 30.
  • Triacs or Silicon Controlled Rectifiers (SCR's) are contemplated as the power switching devices in block 114.
  • the pulses produced at the output of phase angle detector 112 correspond in time with a predetermined phase angle of the AC signal indicated by time line T R in FIG. 2.
  • the output pulse produced by timer circuit 116 will correspond with time T_.
  • FIG. 1 wherein a time delay after a zero crossing is used to determine turn on time of the power signal, or as in the embodiment of FIG. 4, a particular phase angle is detected to determine the point in time when an activation signal is desired for activating the power switching devices.
  • a predetermined timing reference point relative to the AC power signal is located or detected prior to the activation of the power switching devices to produce an activation signal which will subside before or simultaneously with a subsequent zero crossing of the power signal so that the power switching devices will be turned off or switched off at a precise predetermined time, typically a zero crossing as is the case with most thyristors .
  • phase angle detector 112 and timer circuit 116 are portions of a microcomputer based controller (not shown) wherein an A/D converter (not shown) is used to monitor the amplitude (which corresponds with the phase angle) of the signal from source 118.
  • A/D converter not shown
  • user-changeable software enables control of the desired phase angle detected and the width of the control pulse supplied to the power switching devices 114.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
  • Heat Treatment Of Articles (AREA)
  • Control Of Temperature (AREA)

Abstract

L'invention concerne une machine de trempe par induction servant au durcissement périphérique des pièces d'une machine, tels que des engrenages; cette machine comprend un circuit (112) de détection de l'angle de phase qui produit une impulsion à chaque détection correspondant à un angle de phase prédéterminé d'un signal de courant alternatif. Un interrupteur de démarrage (SW2) et l'impulsion produite par le détecteur de phase fournissent des entrées à un circuit (116) qui nécessite la simultanéité de l'impulsion et la mise en fonctionnement de l'interrupteur avant que soit générée une impulsion d'une largeur de signal prédéterminée. Ladite impulsion de largeur de signal prédéterminée déclenche des dispositifs de commutation de puissance (114) qui permettent d'appliquer un signal de puissance prédéterminé à un générateur de radiofréquence (120) couplé à une bobine de chauffage à haute fréquence (128). On obtient un chauffage à haute fréquence de précision en régulant avec précision l'alimentation du générateur de radiofréquence (120).
PCT/US1991/005285 1990-08-06 1991-07-25 Appareil et procede de trempe par induction de pieces de machine, comprenant la regulation precise de la puissance emise WO1992003026A1 (fr)

Priority Applications (6)

Application Number Priority Date Filing Date Title
KR1019930700353A KR970011547B1 (ko) 1990-08-06 1991-07-25 전력 출력을 정확하게 제어하여 기계 부품을 유도 경화시키는 장치 및 방법
DE69118699T DE69118699T2 (de) 1990-08-06 1991-07-25 Gerät und verfahren zum induktionshärten von maschinenbestandteilen mit genauer ausgangsleistungsregelung
AU83092/91A AU649062B2 (en) 1990-08-06 1991-07-25 Apparatus and method of induction-hardening machine components with precise power output control
JP3513384A JP2885511B2 (ja) 1990-08-06 1991-07-25 正確な電力出力制御により機械構成要素を高周波焼入れする装置および装置
EP91914109A EP0542813B1 (fr) 1990-08-06 1991-07-25 Appareil et procede de trempe par induction de pieces de machine, comprenant la regulation precise de la puissance emise
BR919106736A BR9106736A (pt) 1990-08-06 1991-07-25 Aparelho e processo de tempera por inducao de componentes de maquina com controle preciso de saida de potencia

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US563,398 1990-08-06
US07/563,398 US5053596A (en) 1990-08-06 1990-08-06 Apparatus and method of induction-hardening machine components with precise power output control
US69334391A 1991-04-30 1991-04-30
US693,343 1991-04-30

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Publication Number Publication Date
WO1992003026A1 true WO1992003026A1 (fr) 1992-02-20

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EP (1) EP0542813B1 (fr)
JP (1) JP2885511B2 (fr)
KR (1) KR970011547B1 (fr)
AT (1) ATE136721T1 (fr)
AU (1) AU649062B2 (fr)
BR (1) BR9106736A (fr)
CA (1) CA2046851C (fr)
DE (1) DE69118699T2 (fr)
RU (1) RU2113773C1 (fr)
WO (1) WO1992003026A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3355662B1 (fr) * 2017-01-25 2020-06-17 Tetra Laval Holdings & Finance S.A. Procédé de commande d'un circuit de chauffage inductif pour sceller un matériau d'emballage

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US4317975A (en) * 1976-01-14 1982-03-02 Matsushita Electric Industrial Co., Ltd. Induction heating apparatus with means for detecting zero crossing point of high-frequency oscillation to determine triggering time
US4464553A (en) * 1980-07-19 1984-08-07 Sony Corporation Induction heating apparatus with an override circuit
US4511956A (en) * 1981-11-30 1985-04-16 Park-Ohio Industries, Inc. Power inverter using separate starting inverter
US4540866A (en) * 1982-12-03 1985-09-10 Sanyo Electric Co., Ltd. Induction heating apparatus
US4626978A (en) * 1984-07-13 1986-12-02 Saphymo-Stel Static power frequency converter
US4764652A (en) * 1986-04-23 1988-08-16 Gold Star Co., Ltd. Power control device for high-frequency induced heating cooker
US4845328A (en) * 1988-01-13 1989-07-04 Contour Hardening Investors, Ltd. Apparatus for and method of induction-hardening machine components

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US464553A (en) * 1891-12-08 Piano

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317975A (en) * 1976-01-14 1982-03-02 Matsushita Electric Industrial Co., Ltd. Induction heating apparatus with means for detecting zero crossing point of high-frequency oscillation to determine triggering time
US4464553A (en) * 1980-07-19 1984-08-07 Sony Corporation Induction heating apparatus with an override circuit
US4511956A (en) * 1981-11-30 1985-04-16 Park-Ohio Industries, Inc. Power inverter using separate starting inverter
US4540866A (en) * 1982-12-03 1985-09-10 Sanyo Electric Co., Ltd. Induction heating apparatus
US4626978A (en) * 1984-07-13 1986-12-02 Saphymo-Stel Static power frequency converter
US4764652A (en) * 1986-04-23 1988-08-16 Gold Star Co., Ltd. Power control device for high-frequency induced heating cooker
US4845328A (en) * 1988-01-13 1989-07-04 Contour Hardening Investors, Ltd. Apparatus for and method of induction-hardening machine components

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Publication number Publication date
RU2113773C1 (ru) 1998-06-20
JPH06500150A (ja) 1994-01-06
CA2046851C (fr) 1995-03-07
ATE136721T1 (de) 1996-04-15
AU649062B2 (en) 1994-05-12
EP0542813A4 (en) 1993-09-15
AU8309291A (en) 1992-03-02
DE69118699T2 (de) 1996-08-29
EP0542813B1 (fr) 1996-04-10
JP2885511B2 (ja) 1999-04-26
CA2046851A1 (fr) 1992-02-07
DE69118699D1 (de) 1996-05-15
KR970011547B1 (ko) 1997-07-11
EP0542813A1 (fr) 1993-05-26
BR9106736A (pt) 1993-07-06

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