US3846667A - Magnetron having external choke structure - Google Patents

Magnetron having external choke structure Download PDF

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Publication number
US3846667A
US3846667A US00372903A US37290373A US3846667A US 3846667 A US3846667 A US 3846667A US 00372903 A US00372903 A US 00372903A US 37290373 A US37290373 A US 37290373A US 3846667 A US3846667 A US 3846667A
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United States
Prior art keywords
input side
metal member
magnetron
insulator
side sealing
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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
US00372903A
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English (en)
Inventor
H Hisada
A Harada
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Hitachi Ltd
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Hitachi Ltd
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Publication date
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Publication of US3846667A publication Critical patent/US3846667A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/14—Leading-in arrangements; Seals therefor
    • H01J23/15—Means for preventing wave energy leakage structurally associated with tube leading-in arrangements, e.g. filters, chokes, attenuating devices
    • 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
    • H05B6/64—Heating using microwaves

Definitions

  • ABSTRACT A magnetron comprising an air-tight vacuum envelope
  • Foreign Application Priority Data including a cylindrical anode having a plurality of J 30 1972 J 47 76597 vanes, a cathode for thermionic emission arranged on une apan the central axis of the anode and magnets for applying magnetic field to the working space between the 315/3953 315/ anode and cathode.
  • the magnetron is further pro- 58] Fieid 39 51 vided with a choke structure having an opening in the vicinity of the input terminal of the air-tight vacuum envelope, the choke structure being arranged outside [56] References Cned of the envelope and with its effective length almost UNITED STATES PATENTS one fourth of the wavelength of microwave energy 3,315,121 4/1967 Pope 315/3953 X generated by the magnetron. 3,377,562 4/1968 Pope INS/39.53 3,543,082 11/1970 Boehm 3l5/39.53 X 3 Claims, 3 Drawing Figures PAIENIEIJNUV 51914 $846166! sum 1 or 3 FIG.
  • the present invention relates to a magnetron or more in particular to an improved input structure of the magnetron.
  • FIG. 1 is a sectional view showing the essential parts of an example of the conventional magnetrons
  • FIG. 2 is a sectional view showing the essential parts of an embodiment of the present invention.
  • FIG. 3 is a sectional view showing the essential parts of another embodiment of the present invention.
  • the magnetron which generates microwave energy effectively is used for the microwave oven, defreezer and the like and there are various constructions suggested therefor.
  • FIG. 1 shows an example of the magnetron of inner-magnet type in general use.
  • reference numeral 1 shows an anode cylinder made of oxygen free copper
  • numeral 2 a plurality of vanes fixed in such a manner as to divide equally the inner wall of the anode cylinder 1
  • numeral 3 an anode comprising the anode cylinder 1 and vanes 2.
  • Reference numerals 4 and 5 show conical magnets fixed on the sides of the anode cylinder 1 and numeral 6 a cup-shaped input sealing metal having a bottom portion 6a and a through hole 6b and fixed on the magnet 4.
  • Numeral 7 shows an input insulating material arranged in abutment with the bottom portion 6a of the sealing metal 6 and hermetically fixed on the sealing metal 6 at a connection 60.
  • Reference numeral 8 shows a spiral cathode of thoriated tungsten wire or the like for thermionic emission arranged coaxially with the anode cylinder 1 within the space defined by the edges of the vanes 2. The edges of the vanes 2 are in predetermined spaced relationship with the spiral cathode 8 thereby to form a working space 9.
  • Reference numerals l0 and 11 show end shields arranged on the ends of the spiral cathode 8 for preventing the diffusion of electrons in the direction of the axis of the tube
  • numerals 12a and 12b side supports each with an end passed through the through hole 6b of the sealing metal 6 and fixed within the insulating material 7,
  • numeral 12c a center support similar to the side supports 12a and 12b through which working current is supplied, the other ends of the supports 12a, 12b and 12c being fixed on the spiral cathode for thermionic emission.
  • Reference numerals 13a, 13b and 13c show sealing members for hermetically fixing the supports 12a, 12b and 12c, numeral 14 a radiator for cooling the anode 3, numeral 15 an output sealing member fixed on the magnet 5 numeral 16 a cylindrical output insulator fixed on the sealing member 15, numeral 17 an output terminal fixed on the insulator 16, and numeral 18 a metal rod with the ends thereof connected to one of the vanes 2 of the anode 3 and output terminal 17 respectively, so that microwave output generated in the anode 3 is transmitted through metal rod 18 to the output terminal 17 from which it is emitted outside.
  • Reference numeral 19 shows a magnetic device comprising a permanent magnet, numerals 20 and 21 yokes for introducing to the working space the magnetic field generated by the magnetic device 19, numerals 22 and 23 inductors connected to the supports 12a and 12c, numerals 25 and 26 connectors for connecting the supports 12a and 12c to the inductors 22 and 23, and numeral 24 a capacitor connected to the inductors 22 and 23, the inductors 22 and 23 and the capacitor 24 functioning as a filter to erase noise.
  • Numerals 27 and 28 show shield cases for shielding noise waves radiated from the inductors 22 and 23, and numeral 29 a cylindrical stepped metal member with a flange 29a at one end thereof which is fixed on the shield case with a plurality of screws 30, while the other end of the metal member is forcibly fitted on the input sealing metal member 6 to prevent the noise wave from being radiated outside through the magnetic device.
  • Reference numeral 31 shows an insulating tube for preventing dielectric breakdown between the supports 12a to 12, sealing members to 13c or connectors 25 and 26 and shield cases 27 and 28, screws 30 or the cylindrical stepped metal member 29.
  • the air-tight vacuum envelope comprises various component members including the supports 12a to 12c, input insulator 7, input sealing metal member 6, magnets 4 and 5, anode 3, output sealing member 15, output insulator 16 and output terminal 17.
  • the input insulator 7 positioned between the input sealing metal member 6 and the sealing members 13b and 13c has an impedance Za to high-frequency current and the shield case 28 has a certain impedance Zb, that part of microwave energy which has been transferred to the supports 12b and 12c is reflected for lack of the matching of impedances and the reflected microwave energy generates an abnormal standing wave in the spiral cathode 8, so that the spiral cathode for thermionic emission is abnormally heated, resulting in unstable electrical characteristics and short life of the magnetron.
  • An object of the presentinvention is to provide a magnetron with a long useful life.
  • Another object of the invention is to provide a magnetron with stable electrical characteristics.
  • a magnetron comprising an air-tight vacuum envelope, a cy lindrical anode including a plurality of vanes, a cathode arranged on the central axis of the anode for thermionic emission, an input side insulator, a plurality of magnets for applying magnetic field to the working space between the anode and cathode, a plurality of supports for supporting the cathode through the input side insulator, working current being supplied through the supports, an input side sealing metal member interposed between the anode and the input side insulator, the input side sealing metal member being hermetically attached to the input side insulator, an output side sealing member, an output side insulator, and an output terminal, the air-tight vacuum envelope being defined by the anode, the magnets, the input side insulator, the input side sealing member, the output side sealing member, the outputside insulator and the output terminal, wherein the magnetron further comprises a choke structure having an opening in
  • the inventors have developed an improved magnetron which obviates the disadvantages of the prior art magnetron on the basis of technical concept that it is possible to increase greatly the transmission attenuation and enlarge considerably the impedance as viewed from the opening to the choke by providing the choke of a wave-guide or a coaxial cable with an inner conductor having the effective length approximately one fourth of the wavelength involved.
  • FIG. 2 A sectional view of an embodiment of the invention is shown in FIG. 2, in which the same reference numerals are attached to similar component elements as in FIG. 1.
  • reference numeral 32 shows a metal cylinder with a flange which is arranged on the outside of the air-tight vacuum envelope of the magnetron and fixed on the shield case 28 with the screw 30 through the flange 32a and the flange 29a of the cylindrical stepped metal member 29 which is closely attached to the flange 32a.
  • the cylindrical portion 32b is arranged coaxially with the cylindrical stepped metal member 29 and the sealing metal member 6 and extends toward the connection 60 between the input sealing metal member 6 and the input insulator 7 while leaving predetermined space 33.
  • connection 60, the cylindrical stepped metal member 29 and the flanged cylinder 32 constitute a choke structure with the space 33 as an opening in such a manner that the effective length lof the choke is set at approximately one fourth of the length of the microwave generated by the magnetron, by appropriately determining the length of the cylindrical portion 32b of the flanged cylinder 32 and the length of the large diameter cylinder portion 29b of the metal member 29.
  • the above-mentioned arrangement permits impedance Zc of the choke as viewed from the opening of the space 33 to be increased greatly in spite of the three supports 12a to 120 being arranged internally, and as a result both the impedance Za due to the input insulator 7 and impedance Zb within the shield case 28 are negligible.
  • the standing wave occurring in the cathode 8 depends on the position of the opening of the choke structure and impedance Zc thereof, so that by locating an end of the opening of the choke structure at the connection 6c of the sealing metal member as in the above-described embodiment, it is possible not only to minimize the standing wave in the cathode but also to maximize the tolerance of effective length of the choke.
  • This together with the employment of such choke structure, contributes to the advantage of greatly increased transmission attenuation, resulting in great attenuation of micro-wave energy transmitted into the shield case 28 thereby to prevent abnormal temperature increase of the inductors 22 and 23.
  • the insulating tube 31 is interposed between the flanged cylinder 32 and the insulator 7 in such a manner as to cover the space 33, so that the effect of the dielectric constant of the insulating tube 31 increases the degree of coupling of the choke structure, resulting in an increased efficiency of the choke.
  • FIG. 1 Another embodiment of the invention comprising a magnetron of inner magnet type is illustrated in F IG.3.
  • reference numeral 42 shows a cupshaped stepped metal member with an end 42a of the large-diameter side wall thereof fixed on an appropriate position on the shield case 48, while the smalldiameter bottom portion 42b is arranged around the input insulator 47 in such a manner as to provide predetermined space 43 between the bottom portion 42b and the connection 46a of the input sealing metal member 46.
  • the cup-shaped metal member 42, part of the shield case 48 and the connection 46a make up a choke structure with the space 43 as an opening.
  • the size of the cupshaped metal member 42 as well as the distance from the connection between the shield case 48 and the sealing metal member 46 to the connection of the shield case 48 and the part 42a of the large-diameter portion of the cup-shaped metal member 42 is so selected that the effective length I of the choke is approximately one fourth of the wavelength of the microwave generated by the magnetron.
  • Reference numeral 44 shows a capacitor, numeral 49a magnetic device and numeral'50 a magnetron proper.
  • the mag-- netron according to the present invention is characterized by a choke structure provided outside of the airtight vacuum envelope of the magnetron and with its opening situated in the vicinity of the input insulator and the connection of the sealing metal member'so that the effective length of the choke structure is approximately one fourth of the wavelength of the micro-wave energy generated by the megnetron, resulting in a high impedance of the choke structure.
  • both the impedance due to the insulator and the impedance within the shield case are negligible and the fact that microwave energy transmitted into the shield case is greatly attenuated permits the prevention of the tem perature of the inductors from being increased to an abnormally high level.
  • the opening of the choke is situated in the vicinity of the periphery of the input insulator and the sealing metal member, the standing wave generated in the cathode for thermionic emission is minimized while the tolerance of the choke effective length l is maximized.
  • the choke structure is located outside of the air-tight vacuum envelope of the magnetron, the assembly work of the magnetron is facilitated and an abnormal temperature increase which is often seen in the prior art magnetron containing the choke inside thereof is prevented.
  • the provision of the choke structure outside of the air-tight vacuum envelope makes possible impedance adjustment even after the completion of magnetron in accordance with the characteristics requirements thereof.
  • Still another advantage of the magnetron according to the invention resides in the fact that the shield case, inductors and other equipment are easily designed because it is only their breakdown voltages that require to be taken into consideration because of actually neglecting the effect of microwave energy upon such equipment.
  • a magnetron comprising an air-tight vacuum envelope, a cylindrical anode including a plurality of vanes, a cathode arranged on the central axis of said anode for thermionic emission, an input side insulator, a plurality of magnets for applying a magnetic field to the working space between said anode and cathode, a plurality of supports for supporting said cathode through said input side insulator, means for supplying working current through said supports to said cathode, an input side sealing metal member interposed between said anode and said input side insulator, said input side sealing metal member being hermetically closely attached to said input side insulator, an output side sealing member, an output side insulator, and an output terminal; said air-tight vacuum envelope being defined by said anode, said magnets, said input side insulator, said input side sealing member, said output side sealing member, said output side insulator and said output ter minal, wherein said magnetron further comprises a choke structure having an

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Microwave Tubes (AREA)
US00372903A 1972-06-30 1973-06-25 Magnetron having external choke structure Expired - Lifetime US3846667A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1972076597U JPS5352374Y2 (ja) 1972-06-30 1972-06-30

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DE (1) DE2333221A1 (ja)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922612A (en) * 1972-06-30 1975-11-25 Tokyo Shibaura Electric Co Magnetron device
US4006382A (en) * 1975-09-24 1977-02-01 Raytheon Company Magnetron filter
US4039892A (en) * 1975-03-13 1977-08-02 U.S. Philips Corporation Resonant cavity magnetron having a magnet system and magnetron destined for such a combination
US4066928A (en) * 1975-05-20 1978-01-03 U.S. Philips Corporation Resonant cavity magnetron having a helical cathode
US4104561A (en) * 1975-11-28 1978-08-01 New Nippon Electric Co., Ltd. Magnetron operating circuit
US4131824A (en) * 1976-09-20 1978-12-26 Tokyo Shibaura Electric Co., Ltd. Filter device for high frequency generating device
US4163175A (en) * 1977-01-21 1979-07-31 Tokyo Shibaura Electric Co., Ltd. Magnetron for which leakage of H.F. noise is minimized
US4164685A (en) * 1976-09-14 1979-08-14 Tokyo Shibaura Electric Co., Ltd. Magnetron device
US4282463A (en) * 1978-10-16 1981-08-04 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron with continuous magnetic circuit
US4300072A (en) * 1979-02-01 1981-11-10 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron having an internal capacitor for suppressing leakage of high frequency
US4310786A (en) * 1979-09-12 1982-01-12 Kumpfer Beverly D Magnetron tube with improved low cost structure
US4419606A (en) * 1980-06-02 1983-12-06 Hitachi, Ltd. Magnetron
US4851629A (en) * 1988-06-20 1989-07-25 Matsushita Electric Industrial Co., Ltd. High-frequency heating device
US5107181A (en) * 1989-05-19 1992-04-21 Hitachi, Ltd. Magnetron
US20040262304A1 (en) * 2003-06-30 2004-12-30 Matsushita Electric Industrial Co., Ltd. Magnetron
US20170251522A1 (en) * 2014-11-06 2017-08-31 Hirschmann Car Communication Gmbh Contact pin made of copper wire

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5527173Y2 (ja) * 1974-11-15 1980-06-28
JPS578136Y2 (ja) * 1975-10-06 1982-02-16
JPS5823167Y2 (ja) * 1976-11-04 1983-05-18 株式会社日立製作所 マグネトロン
JPS5824370Y2 (ja) * 1977-02-04 1983-05-25 株式会社日立製作所 マグネトロン

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3315121A (en) * 1961-04-27 1967-04-18 Gen Electric Crossed-field electric discharge device
US3377562A (en) * 1961-04-27 1968-04-09 Gen Electric Magnetron device having a cooling arrangement and capacitively coupled output circuit
US3543082A (en) * 1968-08-23 1970-11-24 Technology Instr Corp Of Calif Magnetron
US3551735A (en) * 1965-08-30 1970-12-29 Gen Electric Crossed-field discharge devices and oscillators and amplifiers incorporating the same
US3584255A (en) * 1969-05-12 1971-06-08 Gen Electric Crossed-field discharge device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4518431Y1 (ja) * 1966-03-29 1970-07-28

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3315121A (en) * 1961-04-27 1967-04-18 Gen Electric Crossed-field electric discharge device
US3377562A (en) * 1961-04-27 1968-04-09 Gen Electric Magnetron device having a cooling arrangement and capacitively coupled output circuit
US3551735A (en) * 1965-08-30 1970-12-29 Gen Electric Crossed-field discharge devices and oscillators and amplifiers incorporating the same
US3543082A (en) * 1968-08-23 1970-11-24 Technology Instr Corp Of Calif Magnetron
US3584255A (en) * 1969-05-12 1971-06-08 Gen Electric Crossed-field discharge device

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922612A (en) * 1972-06-30 1975-11-25 Tokyo Shibaura Electric Co Magnetron device
US4039892A (en) * 1975-03-13 1977-08-02 U.S. Philips Corporation Resonant cavity magnetron having a magnet system and magnetron destined for such a combination
US4066928A (en) * 1975-05-20 1978-01-03 U.S. Philips Corporation Resonant cavity magnetron having a helical cathode
US4006382A (en) * 1975-09-24 1977-02-01 Raytheon Company Magnetron filter
US4104561A (en) * 1975-11-28 1978-08-01 New Nippon Electric Co., Ltd. Magnetron operating circuit
US4164685A (en) * 1976-09-14 1979-08-14 Tokyo Shibaura Electric Co., Ltd. Magnetron device
US4131824A (en) * 1976-09-20 1978-12-26 Tokyo Shibaura Electric Co., Ltd. Filter device for high frequency generating device
US4163175A (en) * 1977-01-21 1979-07-31 Tokyo Shibaura Electric Co., Ltd. Magnetron for which leakage of H.F. noise is minimized
US4282463A (en) * 1978-10-16 1981-08-04 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron with continuous magnetic circuit
US4300072A (en) * 1979-02-01 1981-11-10 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron having an internal capacitor for suppressing leakage of high frequency
US4310786A (en) * 1979-09-12 1982-01-12 Kumpfer Beverly D Magnetron tube with improved low cost structure
US4419606A (en) * 1980-06-02 1983-12-06 Hitachi, Ltd. Magnetron
US4851629A (en) * 1988-06-20 1989-07-25 Matsushita Electric Industrial Co., Ltd. High-frequency heating device
US5107181A (en) * 1989-05-19 1992-04-21 Hitachi, Ltd. Magnetron
US20040262304A1 (en) * 2003-06-30 2004-12-30 Matsushita Electric Industrial Co., Ltd. Magnetron
US7067782B2 (en) * 2003-06-30 2006-06-27 Matsushita Electric Industrial Co., Ltd. Magnetron
US20170251522A1 (en) * 2014-11-06 2017-08-31 Hirschmann Car Communication Gmbh Contact pin made of copper wire

Also Published As

Publication number Publication date
DE2333221A1 (de) 1974-01-10
JPS4934666U (ja) 1974-03-27
JPS5352374Y2 (ja) 1978-12-14

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