US3816690A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Induction heating apparatus
Assignee: Illinois Tool Works Inc
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Filing: 1972-09-18
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Granted: 1974-06-11
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Expires: 1992-09-18
Abstract
Abstract The embodiment of the invention disclosed herein is directed to an induction heating apparatus which includes solid state circuitry of the generator means and a tuned circuit induction heating member capable of being remotely located from the generator and readily movable to various positions. The induction heating unit comprises an inductance element and a series connected capacitance element forming a series resonant circuit at an operating frequency. The generator includes frequency adjusting means so that substantial coincidence of frequency between the generator and the frequency of resonance of the tuned inductance element is obtained. A wattsecond responsive circuit is coupled to the inductance unit to terminate operation thereof upon sensing a desired predetermined measurement of wattseconds. Also coupled to the inductance unit is an over voltage sensing circuit for sensing the value of voltage developed across the capacitance element, when in a resonant tuned condition, thereby preventing over voltages from occurring and damaging the components.
Inventors
- 👤 E Mittelmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:22
CPC Classifications
H; H05; H05B; H05B6/00; H05B6/02; H05B6/10; H05B6/101; G; G01; G01R; G01R21/00; H02; H02H; H02H3/00; H02H3/20; H05B6/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
117 words
An induction heating generator comprising in combination: an inverter circuit, an output transformer having a primary winding forming an integral part with said inverter circuit and a closely coupled secondary winding, both said primary winding and said secondary winding being wound on a magnetic core, an inductance element with a magnetic core, a capacitor element connected in series with said inductance element, said series combination being connected across the terminals of said secondary winding of said inverter circuit, the series combination of said inductance element and said capacitance element being tuned to a resonant frequency substantially equal to the frequency generated by said inverter circuit so that no substantial reactive component is reflected across the primary winding.
Claim 2
Dependent Claim
117 words
An induction heating generator comprising in combination: an inverter circuit, an output transformer having a primary winding forming an integral part with said inverter circuit and a closely coupled secondary winding, both said primary winding and said secondary winding being wound on a magnetic core, an inductance element with a magnetic core, a capacitor element connected in series with said inductance element, said series combination being connected across the terminals of said secondary winding of said inverter circuit, the series combination of said inductance element and said capacitance element being tuned to a resonant frequency substantially equal to the frequency generated by said inverter circuit so that no substantial reactive component is reflected across the primary winding.
Claim 3
Dependent Claim
64 words
The induction heating system according to claim 1 wherein said inductance element includes a U-shaped ferrite magnetic core with flat end surfaces to be placed upon a flat metal sheet surface to form the load for the induction heating unit, said flat end surfaces of said ferrite magnetIc U-shaped core being pressed against the flat surface during each operation of the induction heating unit.
Claim 4
Dependent Claim
41 words
The induction heating system according to claim 1 wherein the connection between the inductance element and the secondary winding of the output transformer is a flexible connection allowing freedom of movement of the inductance element without movement of the inverter circuit.
Claim 5
Dependent Claim
168 words
An induction heating generator comprising in combination: an inverter circuit, an output transformer having a primary winding forming an integral part with said inverter circuit and a closely coupled secondary winding, both said primary winding and said secondary winding being wound on a magnetic core, an inductance element with a magnetic core, a capacitor element connected in series with said inductance element, said series combination being connected across the terminals of said secondary winding of said inverter circuit, the series combination of said inductance element and said capacitance element being tuned to a resonant frequency substantially equal to the frequency generated by said inverter circuit so that no substantial reactive component is reflected across the primary winding and wattsecond sensing means operatively coupled with the tuned circuit formed by said inductance element and said capacitance element for sending the quantity of energy supplied thereto, said wattsecond sensing means including turn-off switch means coupled to said inverter circuit to terminate operation thereof upon accumulation of a predetermined wattsecond magnitude.
Claim 6
Dependent Claim
168 words
An induction heating generator comprising in combination: an inverter circuit, an output transformer having a primary winding forming an integral part with said inverter circuit and a closely coupled secondary winding, both said primary winding and said secondary winding being wound on a magnetic core, an inductance element with a magnetic core, a capacitor element connected in series with said inductance element, said series combination being connected across the terminals of said secondary winding of said inverter circuit, the series combination of said inductance element and said capacitance element being tuned to a resonant frequency substantially equal to the frequency generated by said inverter circuit so that no substantial reactive component is reflected across the primary winding and wattsecond sensing means operatively coupled with the tuned circuit formed by said inductance element and said capacitance element for sending the quantity of energy supplied thereto, said wattsecond sensing means including turn-off switch means coupled to said inverter circuit to terminate operation thereof upon accumulation of a predetermined wattsecond magnitude.
Claim 7
Dependent Claim
98 words
The induction heating apparatus according to claim 4 wherein said wattsecond sensing means includes a rectifier means coupled to said capacitance element, a first capacitor coupled to said rectifier means, a second capacitor coupled to said first capacitor, a silicon controlled rectifier coupled between said first and second capacitors control means coupled to said silicon controlled rectifier for periodically energizing and de-energizing said silicon controlled rectifier for transferring electric charge from said first capacitor to said second capacitor, and pulse means coupled to said second capacitor to develop a turn-off pulse for terminating operation of said inverter circuit.
Claim 8
Dependent Claim
98 words
The induction heating apparatus according to claim 4 wherein said wattsecond sensing means includes a rectifier means coupled to said inductance element, a first capacitor coupled to said rectifier means, a second capacitor coupled to said first capacitor, a silicon controlled rectifier coupled between said first and second capacitors control means coupled to said silicon controlled rectifier for periodically energizing and de-energizing said silicon controlled rectifier for transferring electric charge from said first capacitor to said second capacitor, and pulse means coupled to said second capacitor to develop a turn-off pulse for terminating operation of said inverter circuit.
Claim 9
Dependent Claim
51 words
The induction heating apparatus according to claim 4 further including over voltage sensing means operatively coupled with the tuned circuit formed by said inductance element and said capacitance element, said over voltage circuit providing automatic turn-off of said inverter circuit upon sensing a voltage that is beyond a predetermined voltage level.
Claim 10
Dependent Claim
88 words
The induction heating apparatus according to claim 7 wherein said over voltage circuit means includes a voltage divider network connected across said capacitance element, a unijunction transistor having the emitter electrode thereof coupled to a junction intermediate said voltage divider network, and a reference voltage coupled across the base electrodes of said unijunction transistor, whereby said reference voltage is compared with the voltage developed across said capacitance element and said unijunction transmission produces a turn-off pulse when said capacitance element develops a voltage beyond a predetermined voltage level.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-10 | 1977-12-10 | 1978-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-10 | 1981-12-10 | 1982-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-10 | 1985-12-10 | 1986-06-11 | $7700.00 | Window Closed / Lapsed |