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Publication numberUS3588588 A
Publication typeGrant
Publication dateJun 28, 1971
Filing dateJun 16, 1969
Priority dateJun 21, 1968
Also published asDE1930015A1, DE1930015B2
Publication numberUS 3588588 A, US 3588588A, US-A-3588588, US3588588 A, US3588588A
InventorsNumata Tsuneo
Original AssigneeMatsushita Electronics Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Magnetron device with exiting permanent magnet free from magnetic short-circuiting by frame
US 3588588 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

United States Patent inventor Tsuneo Numata Kyoto, Japan Appl. No. 833,253

Filed June 16, 1969 Patented June 28, 1971 Assignee Matsushita Electronics Corporation Osaka, Japan Field olSearch 315/3951, 39.77, 39.73, 39.71

References Cited UNITED STATES PATENTS 2/1962 Schall et a1.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-Saxfield Chatmon, Jr. Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: A magnetron device in which an upper insulator vessel including therein cathode lead members extending from a cathode contained, together with an anode, a cavity resonator and magnetic pole pieces, in a metal vessel is disposed in an axial hole in a cylindrical or conical permanent magnet for exciting a magnetron with an interstice therebetween to define a ventilation flue for effectively cooling the upper insulator vessel and the permanent magnet to prevent the insulator vessel from breakage due to uneven heating of the insulator vessel by making the distribution of the temperature of the insulator vessel even.

PAFENIED JUN28 1971 3 588,588

sum 1 [1F 3 INVENTOR TSUNEO NUMATA ATTORNEY PATENTED JUN28 l97l SHEET 2 OF 3 PATENIED JUN28 I972 SHEET 3 [1F 3 MAGNETRON DEVICE WITH EXITING PERMANENT MAGNET FREE FROM MAGNETIC SI-IORT-CIRCUITING BY FRAME The present invention relates to magnetron devices, and more particularly to magnetron devices suitable for use in electronic ranges.

A magnetron comprising a tubular metal vessel including therein a cathode, an anode surrounding said cathode, an upper magnetic pole piece, a lower magnetic pole piece, and a cavity resonator; an upwardly projecting upper insulator vessel contiguous to said upper pole piece and enclosing therein a cathode lead member; and a downwardly projecting lower insulator vessel contiguous to said lower pole piece and enclosing therein an antennalike electromagnetic wave emitting electrode extending from said cavity resonator is disclosed, for example, in U.S. Pat. No. 2,721,294 to E. J. Shelton. A magnetron coupled with a cylindrical permanent magnet is also known, for example, by U.S. Pat. No. 2,824,261 to P. H. Peters et al.

It is an object of the present invention to provide a magnetron device in which the occupation space of a permanent magnet for exciting a magnetron is made as small as possible so that a compact high frequency heating apparatus can be provided when the magnetron device is employed therein.

It is another object of the present invention to provide a magnetron device in which an upper insulator vessel is protected by means of a permanent magnet from an impact from outside. I

It is a further object of the present invention to provide a magnetron device in which a longitudinal hole in a permanent magnet is employed as a ventilation flue to effectively cool the permanent magnet itself and, at the same time, to make the temperature distribution of an upper insulator vessel in a longitudinal direction as uniform as possible to thereby protect an upper insulator vessel from breakage due to thermal strain.

It is a still further object of the present invention to provide a magnetron device in which provision is made against magnetic short circuiting of both poles of a permanent magnet.

According to the present invention there is provided a magnetron device comprising a magnetron having a tubular metal vessel including therein a cathode, an anode surrounding said cathode, an upper magnetic pole piece, a lower magnetic pole piece, and a cavity resonator, an upwardly projecting upper insulator vessel contiguous to said upper pole piece and enclosing a cathode lead member therein, and a downwardly projecting lower insulator vessel contiguous to said lower pole piece and enclosing therein an antennalike electromagnetic wave emitting electrode extending from said cavity resonator; a permanent magnet having an axial hole the diameter of which is greater than the diameter of said upper insulator vessel; and yoke means for magnetically coupling said permanent magnet with said magnetron, characterized in that said permanent magnet is arranged coaxially with said metal vessel in such a manner that at least a great part of said upper insulator vessel is disposed in said axial hole of said pennanent magnet with interstice therebetween with the lower end surface of said permanent magnet being coupled with the upper surface of said upper magnetic piece directly or through the intermediary of a yoke member.

Features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention when read with reference to the accompanying drawings, in which:

FIG. 1 is a partly broken perspective view of an embodiment of the invention;

FIG. 2 is a partly broken side view of the embodiment of FIG. 1;

FIG. 3 is a partly broken perspective view of another embodiment of the invention;

FIG. 4 is a partly broken side view of the embodiment of FIG. 3;

FIG. 5 is a partly broken perspective view of a further embodiment of the invention;

FIG. 6 is a partly exploded side view of a still further embodiment of the invention; and

FIG. 7 is a partly exploded perspective view of another embodiment of the invention.

Referring to FIGS. 1 and 2, a magnetron 1 comprises a cylindrical metal vessel 2 and cup-shaped insulator vessels 3 and 4 made of glass, ceramic or the like sealed to the upper and lower ends of the cylindrical metal vessel 2. Inside the metal vessel 2, a cathode 17 and an anode 19 surrounding the cathode 17 are provided coaxially with the vessel 2, and upper and lower magnetic pole pieces 24 and 25 are provided at the upper and lower ends of the vessel 2, respectively. Further, in a space adjacent to the anode inside the vessel 2 there is provided a cavity resonator 26. Cathode lead members connected with the cathode are enclosed in the upper insulator vessel 3, and an antennalike electromagnetic wave emitting electrode 5 extending from the cavity resonator 26 is enclosed in the lower insulator vessel 4.

A radiator 6 for air cooling the magnetron 1 comprises an appropriate number of good thermally conductive radiating plates 9 piled up with certain intervals therebetween disposed between an intake port 7 and an exhaust port 8. The heat radiating plates 9 are welded to the circumference of 'the metal vessel 2. The radiator 6 effects forced cooling of the magnetron 1 by combination with a blower.

A conical or cylindrical permanent magnet 10 preferably made of ferrite has an axial hole 11 within which the whole or a great part of the upper insulator vessel 3 is disposed without touching the magnet 10. The lower end surface of the permanent magnet 10 is in contact with the upper surface of the upper pole piece 24 in the metal vessel 2 directly or through the intermediary of a thin heat insulating packing, whereby one pole of the pennanent magnet 10 is magnetically coupled with the upper pole piece 24. The other pole, Le. the upper surface of the permanent magnet 10 is magnetically coupled with the lower pole piece 25 through a high permeability metal frame members 12 and 13 which serve as magnetic coupling means, the frame member 13 being in contact with the lower surface of the lower pole piece 25 directly or through an interposed thin heat insulating packing. The frame member 13 has a hole 14 through which the lower insulator vessel 4 enclosing therein the electromagnetic wave emitting electrode 5 protrudes downward. The frame member 13 has also an appropriate number of holes 15 for screws for mounting the magnetron device on an electronic range. Leadout parts 16 of the cathode lead members extend outward from the upper insulator vessel 3.

According to the second embodiment of this invention shown in FIGS. 3 and 4, the radiator 6 has a second exhaust port 18, and the permanent magnet 10 has a ventilation flue 20 cut through the sidewall thereof. In this case, a cooling air current fed from the intake port 7 of the radiator 6 through the exhaust port 18 to the permanent magnet 10 is led to the magnetron 1 through the ventilation flue 20, and goes up in the axial hole 11 along the surface of the heated upper insulator vessel 3 to effectively cool the permanent magnet 10 and the upper insulator vessel 3. Although the ventilation flue 20 is shown as of slit shape in FIGS. 3 and 4, other shapes of hole or channel may be employed as well. Of course, two or more ventilation flues can be employed. It is not always necessary to supply the cooling air current to the ventilation flue 20 through the radiator 6, but it may be supplied directly from a blower.

When it is difficult to form the ventilation flue 20 through the sidewall of the conical permanent magnet 10, it is possible to provide a conical yoke 21 made of previously magnetized or not previously magnetized ferromagnetic material between the permanent magnet 10 and the upper pole piece and to provide a ventilation flue 22 through the sidewall of the yoke as shown in FIG. 5. An axial hole 23 of the conical yoke 21 and the axial hole 11 of the cylindrical permanent magnet 10 are communicating with each other, and the upper insulator vessel 3 is included in the axial holes 11 and 23 without contactupper magnetic pole piece.

Although as the cylindrical or conical permanent magnet having an axial hole both of the so-called barium-ferrite group magnet and the alnico group magnet can be employed, the former magnet is preferable to the device of this invention for the reason that the ferrite group magnet has a good workability and is excellent in the efficiency of heat absorption and heat radiation because ofits pitch-dark color. Since the permanent magnet 10 surrounds the upper insulator vessel 3 almost along the entire length ofthe vessel 3, the magnet 10, when it is of ferrite, effectively dissipates the heat of the magnetron 1 generated at the time of its operation, and makes the heating of the whole of the upper insulator vessel 3 approximately even to reduce the strain of the vessel 3 resulting from uneven heating. It is desirable to provide a magnetoshielding metal layer on the surface of the wall of the axial hole of the ferrite magnet 10.

In the embodiments of the present invention so far described, when the periphery of particularly the lower edge of the permanent magnet 10 and the metal frame member R2 are close to each other, both poles of the permanent magnet 10 are substantially magnetically short circuited through the frame member 12 with the result that the density of magnetic flux to be supplied to the magnetron l is reduced. An embodiment provided against this short circuiting is shown in FIG. 6.

In FIG. 6, magnets 30 for repulsion are provided on the inner side of the frame member 12 at positions corresponding to the lower pole of the permanent magnet 10 in such a manner that the lower pole of the permanent magnet 10 and the same kind of poles of the magnets 30 are opposed to each other. Consequently, the short circuiting of the permanent magnet 10 by means of the frame member 12 is prevented by the magnetic field originated from the magnets 30. It was found by experiments that while the density of magnetic flux supplied to the metal vessel 2 was about 1,730 gauss when the outer diameter of the metal vessel 2 was 70 mm., the outer diameter and height of the cylindrical permanent magnet 10 were about 80 mm. and 45 mm., respectively, and the interval between the outer wall of the permanent magnet 10 and the inner wall of the frame member 112 was about mm., it was increased to about L880 gauss when two small permanent magnets for repulsive magnetic field generation were employed. Either permanent magnets or electromagnets can be employed as the magnets 30 for the repulsive field generation.

In the embodiment shown in FIG. 7, a cylindrical permanent magnet 100 surrounds not only all or a great part of the insulator vessel 3, but also the metal vessel 2 and the radiator 6. A window'ltll formed through the sidewall of the permanent magnet I00 fits the intake port 8 of the radiator 6. A yoke 102 in this embodiment is cylindrical and arranged inside the cylindrical permanent magnet 100.

lclaim:

l A magnetron device comprising a magnetron having a tubular metal vessel including therein a cathode, an anode surrounding said cathode, an upper magnetic pole piece 24, a lower magnetic pole piece, and a cavity resonator, an upwardly projecting upper insulator vessel contiguous to said upper pole piece and enclosing a cathode lead member therein, and a downwardly projecting lower insulator vessel contiguous to said lower pole piece and enclosing therein an antennalike electromagnetic wave emitting electrode extending from said cavity resonator; a permanent magnet having an axial hole the diameter of which is greater than the diameter of said upper insulator vessel; and a frame member magnetically coupling said permanent magnet with said magnetron, wherein said permanent magnet is arranged coaxially with said metal vessel in such a manner that at least a greater part of said upper insulator vessel is disposed in said axial hole of said permanent magnet with an air space therebetween with the lower end surface of said permanent magnet being coupled with the upper surface of said upper magnetic pole piece, and means preventing said permanent magnet from being magneti cally short circuited through said frame member.

2. A magnetron device according to claim 1, wherein said permanent magnet is provided with at least one hole or channel through its sidewall, said hole'or channel communicating with said air space to define a ventilation flue.

3. A magnetron device according to claim ll, comprising a yoke member interposed between said permanent magnet and said upper magnetic pole, said yoke member being provided with at least one hole or channel through its sidewall, said hole or channel communicating with said air space to define a ventilation flue.

4. A magnetron device according to claim I, in which said permanent magnet is a ferrite group magnet.

5. A magnetron device according to claim I, wherein said frame member is provided with at least one magnet for developing a repulsive field to said permanent magnet at a position close to and opposing the periphery of the lower edge ofsaid permanent magnet.

6. A magnetron device according to claim 4, wherein the sidewall of said axial hole of said permanent magnet is provided with a magnetoshielding metal layer.

7. A magnetron device comprising a magnetron having a tubular metal vessel including therein a cathode, an anode surrounding said cathode, an upper magnetic pole piece, a lower magnetic pole piece, and a cavity resonator, an upwardly projecting upper insulator vessel contiguous to said upper pole piece and enclosing a cathode lead member therein, and a downwardly projecting lower insulator vessel contiguous to said lower pole piece and enclosing therein an antennalike electromagnetic wave emitting electrode extending from said cavity resonator; a permanent magnet having an axial hole the diameter of which is greater than the diameter of said upper insulator vessel; and yoke means for magnetically coupling said permanent magnet with said magnetron, wherein said permanent magnet is arranged on said upper magnetic pole piece such that said upper insulator vessel is disposed in said axial hole of said permanent magnet with an air space therebetween defining a ventilation flue, and said lower insulator vessel extends downward through said yoke means.

8. A magnetron device according to claim ll, wherein the lower diameter of said permanent magnet is smaller than the upper diameter thereof.

9. A magnetron device according to claim I, wherein the lateral extension of the lower part of said frame member is larger than that of the upper part thereof.

10. A magnetron device according to claim 3, wherein the lower diameter of said yoke member is smaller than the upper diameter thereof. I

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 588 D t d June 28, 1971 Inventor) Tsuneo NUMATA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Claim for Convention Priority and six Japanese patent applications should be listed as follows:

Patent Appln. Patent Appln. Patent Appln. Patent Appln. Utility Model Utility Model Japan, Japan, Japan, Japan, Japan, Japan,

Signed and sealed this 25th day of January 1972.

SEAL) attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER, JR. Commissioner of Patents eating Officer and FORM O-1050110459? USCOMM-DC 60376-P59 W U 5 GOVERNMENY PRINTING OFFICE I969 0-366-33l

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3716750 *May 12, 1971Feb 13, 1973Nakada KMagnetrons
US3794879 *Oct 24, 1972Feb 26, 1974Raytheon CoMicrowave magnetron
US3809950 *Feb 14, 1973May 7, 1974Tokyo Shibaura Electric CoMagnetron
US3843904 *Aug 1, 1973Oct 22, 1974Us NavyMagnetic field geometry for crossed-field devices
US3881127 *Nov 1, 1973Apr 29, 1975Us NavyBucking samarium cobalt magnets for crossed field devices
US3916247 *Jul 10, 1974Oct 28, 1975Tokyo Shibaura Electric CoShell type magnetron device
US4042851 *Aug 27, 1975Aug 16, 1977Sanyo Electric Co., Ltd.Magnetron
US4204138 *Apr 19, 1978May 20, 1980Tokyo Shibaura Electric Co., Ltd.Permanent magnet-containing magnetron
US4282459 *Sep 4, 1979Aug 4, 1981Tomokatsu OguroMagnetron
US4794304 *Dec 24, 1986Dec 27, 1988Matsushita Electronics CorporationMagnetron with cooling fin structure
US5210465 *Oct 26, 1990May 11, 1993Eev LimitedMagnetron having an tm01 output coupling probe passing through a coupling iris
US5508583 *May 9, 1995Apr 16, 1996Samsung Electronics Co., Ltd.Cathode support structure for magnetron
US20040245864 *Oct 31, 2002Dec 9, 2004Bailey Paul BrianMoving coil transducer
WO2003039192A1 *Oct 31, 2002May 8, 2003Isis Innovation LimitedImproved moving coil transducer
Classifications
U.S. Classification315/39.53, 315/39.71, 315/39.73
International ClassificationH01J23/10, H01J23/00, H01J23/02
Cooperative ClassificationH01J23/10, H01J23/005
European ClassificationH01J23/10, H01J23/00B