US2773190A - High-frequency heating system - Google Patents

High-frequency heating system Download PDF

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Publication number
US2773190A
US2773190A US388995A US38899553A US2773190A US 2773190 A US2773190 A US 2773190A US 388995 A US388995 A US 388995A US 38899553 A US38899553 A US 38899553A US 2773190 A US2773190 A US 2773190A
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US
United States
Prior art keywords
grid
oscillator
control member
control
circuit
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US388995A
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English (en)
Inventor
Ruiter Jacob Willem De
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.)
Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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
Application filed by Hartford National Bank and Trust Co filed Critical Hartford National Bank and Trust Co
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Publication of US2773190A publication Critical patent/US2773190A/en
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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
    • H05B6/46—Dielectric heating
    • H05B6/48—Circuits
    • H05B6/50—Circuits for monitoring or control
    • 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
    • H05B6/04—Sources of current

Definitions

  • the present invention relates to high-frequency heating system. More particularly, the invention relates to a high-frequency oven comprising a grid-controlled electron tube oscillator in which the direct-current circuit of the control grid includes a coil for energizing a control member which is subject to the tension of a spring and which during operation controls the feedback coupling for automatic stabilization of the excitation of the control grid upon varying load.
  • the grid circuit include a grid-bias source which may be switched in and which cuts off the oscillator tube by means of negative grid-bias while maintaining the other operating voltages.
  • a longer life of the expensive oscillator tube especially when high powers are utilized is achieved by the use of means by which the control member is moved, against the tension of the spring, into the position of minimum excitation when the oscillator tube is made inoperative by negative grid-bias.
  • control member initially occupies the position for minimum grid excitation (minimum feed-back) when the oscillator is made operative by suppression of the blocking grid-bias temporarily applied.
  • minimum grid excitation minimum feed-back
  • suppression of the blocking grid-bias temporarily applied A transient overload on the control grid as a result of the mechanical energy of the automatic control of grid excitation which otherwise might occur is thus avoided with certainty.
  • the control member may naturally be moved into the position for minimum excitation in different ways.
  • the control member may be moved for example, by purely mechanical means with the use of an adjusting mechanism coupled to a switch for switching on the blocking voltage for the oscillator; or it may be moved by electromagnetic means with the use of a pull magnet counteracting the tension of its spring.
  • the coil available for energizing the control member, i. e. by connecting it, on the one hand, by way of a switch which is to be opened for switching off the oscillator, to the control grid and, on the other hand, by way of a switch which is to be closed upon switching off the oscillator, to a source of negative auxiliary bias which provides the auxiliary current to substitute the maximum grid current which occurs in normal operation.
  • the high-frequency oven of the figure comprises a triode 2, in Colpitts-oscillator connection, which is connected to an anode voltage source 1.
  • the anode of the triode 2 is coupled by way of a coupling capacitor 3 to 2,773,190 Patented Dec. 4, 1956 one extremity of an oscillator-circuit 4 comprising a circuit coil 5 and circuit capacitors 6, 7 connected in series.
  • the other extremity of the circuit 4 is coupled to the grid of the triode 2 by Way of an adjustable capacitive voltage-divider having capacitors 8, 9, which serves to control the excitation of the control grid.
  • the cathode of tube 2 is connected to ground and to the junction of the capacitors 6, 7 of the circuit 4.
  • a load 10 on the high-frequency oven is coupled by way of a transformer to the oscillator circuit 4.
  • the control grid of tube 2 is connected to ground by way of a D. C. grid circuit which includes in succession a high frequency choke 11, a switch 12 which is closed during operation of the oscillator, a fixed resistor 13, an adjustable resistor 14 and a coil 15 for energizing a control member 17 which can slide in the axial direction against the tension of a spring 16.
  • the control member 17 is mechanically coupled to the adjustable voltage-divider 8, 9 for varying the excitation of the control grid, as shown by dotted line.
  • the spring 16 may exhibit a linear characteristic.
  • a spring having a characteristic which is matched to the magnetic pulling force characteristic of the energizing coil with a given direct gridcurrent. More particularly the spring used may be of the type having a quadratic characteristic in the manner as described in detail in U. S. Patent application Serial No. 281,642, filed April 10, 1952.
  • the D. C. grid circuit described is interrupted by the switch 12. Thereafter the triode 2 is cut off by the negative grid-bias taken by way of a resistor 18 from a terminal 19 of a gridbias source 20, at the same time as a resistor 22 loading the grid-bias source 20 is switched in by means of a switch 21 for fixing the biassing potential. Furthermore, the series-combination of the energizing coil 15 and the adjustable resistor 14 is connected, via a switch 23, to a terminal 24 of the grid-bias source 20, in order to move the control member 17, despite the tension of the spring 16, into the position for minimum grid-excitation. The holding current then flowing in the energizing coil 15 may be adjusted to the value desired by means of the adjustable resistor 14.
  • the switches 12, 21, 23, which are preferably ganged and may be operated in common with the use of a switching relay, are moved again into the positions shown in the figure.
  • a temporary overload on the control grid of the oscillator as a result of over-excitation thereof is avoided, since, upon switching-in, the control member 17 has to leave the position for minimum grid-excitation.
  • the connection between the D. C. grid circuit 11-15 and the grid-bias source 20 may be wholly interrupted.
  • the grid-bias source 20 is utilized for sup- 3 plementing the negative grid-bias required during the op eration of the oscillator by way of the voltage-divider constituted by the elements 18, 13, l4, 15,
  • a high-frequency heating system comprising an oscillator, said oscillator comprising an electron discharge tube having a control grid and a feedback circuit coupled to said control grid, said feedback circuit comprising a variable impedance coupled to said control grid, a direct current circuit coupled to said control grid, a control member coupled to said variable impedance whereby variation in position of said control member produces variation in the impedance value of said variable impedance thereby varying the excitation of said control grid, a spring disposed to exert a force in a given direction on said control member, said direct current circuit including a coil disposed to exert a force on said control member in a direction opposite to said given direction, said lastmentioned force having a magnitude as determined by the magnitude of the current in said direct current circuit, a grid bias source, means for selectively applying a negative grid bias from said source to said tube to cut off said tube, and means operative substantially simultaneously with said last-mentioned means for applying a current from said source through said coil thereby exerting a force on said control member in
  • a high-frequency heating system comprising an oscillator, said oscillator comprising an electron discharge tube having a control grid and a feedback circuit coupled to said control grid, said feedback circuit comprising a variable impedance coupled to said control grid, a direct current circuit coupled to said control grid, a control member coupled to said variable impedance whereby variation in position of said control member produces variation in the impedance value of said variable impedance thereby varying the excitation of said control grid, a spring disposed to exert a force in a given direction on said control member, said direct current circuit including a coil disposed to exert a force in said control member in a direction opposite to said given direction, said last mentioned force having a magnitude as determined by the magnitude of the current in said direct current circuit, a grid bias source, means for selectively applying a negative grid bias from said source to said tube to cut off said tube comprising first switch means connected in said direct current circuit between said control grid and said coil to render said tube inoperative in its open position, and second switch means connected in said direct current circuit between said coil and

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
US388995A 1952-11-29 1953-10-29 High-frequency heating system Expired - Lifetime US2773190A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL2773190X 1952-11-29
NL316950X 1952-11-29

Publications (1)

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US2773190A true US2773190A (en) 1956-12-04

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US388995A Expired - Lifetime US2773190A (en) 1952-11-29 1953-10-29 High-frequency heating system

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US (1) US2773190A (de)
CH (1) CH316950A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3292104A (en) * 1963-06-24 1966-12-13 Marconi Co Ltd Amplitude control circuit for transistor oscillators

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1247462B (de) * 1959-06-20 1967-08-17 Robert Bosch Elektronik Ultrakurzwellen-Roehrengenerator mit Funkentstoerung, z. B. fuer Therapiegeraete

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1708027A (en) * 1925-08-14 1929-04-09 American Telephone & Telegraph Control device for vacuum tubes
US2454845A (en) * 1943-05-04 1948-11-30 Fed Telephone & Radio Corp High-frequency oscillator circuit for induction heating apparatus
US2594420A (en) * 1948-06-29 1952-04-29 Rca Corp High-frequency dielectric heating system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1708027A (en) * 1925-08-14 1929-04-09 American Telephone & Telegraph Control device for vacuum tubes
US2454845A (en) * 1943-05-04 1948-11-30 Fed Telephone & Radio Corp High-frequency oscillator circuit for induction heating apparatus
US2594420A (en) * 1948-06-29 1952-04-29 Rca Corp High-frequency dielectric heating system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3292104A (en) * 1963-06-24 1966-12-13 Marconi Co Ltd Amplitude control circuit for transistor oscillators

Also Published As

Publication number Publication date
CH316950A (de) 1956-10-31

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