US3106659A

US3106659A - Microwave tube construction

Info

Publication number: US3106659A
Application number: US801536A
Authority: US
Inventors: Lynn J Brady
Original assignee: Kearfott Co Inc
Current assignee: Kearfott Co Inc
Priority date: 1959-03-24
Filing date: 1959-03-24
Publication date: 1963-10-08
Anticipated expiration: 1980-10-08
Also published as: GB880674A

Description

Oct 8, 1963 L. J. BRADY 3,106,659

MICROWAVE TUBE CONSTRUCTION Filed March 24, 1959 2 Sheets-Sheet l Ly/vu J BRADY INVENTOR.

Oct. 8, 1963 L, J. 86AM 3,106,659

MICROWAVE TUBE CONSTRUCTION Filed March 24, 1959 2 Sheets-Sheet 2 Egg LyA/A/ $3840) INVENTOR.

United States Patent York Filed Mar. 24, 1959, Ser. No. 801,536 2 Claims. (Cl. 313-84) This invention generally relates to improvements in electron tube constructions and more particularly to improved ferrite magnet field focusing assemblies particularly useful for microwave electron tubes or the like.

In the transmission and amplification of extremely high frequency electromagnetic waves in the microwave region, the use of microwave electron tubes have found great acceptance. In such devices streams of electrons are directed within a tube in various paths and focused and controlled by permanent magnet assemblies external to the tube and generating strong magnetic focusing fields through the tube to interact with the electron flow. The development of larger capacity tubes to handle increased microwave power has required the use of larger and bulkier magnetic focusing means to satisfy the need for stronger magnetic fields; and despite the improvement brought about by the recent introduction of ferrite permanent magnets for such applications, there still exists a great need for reducing the size and weight of the magnetc field producing and transfer structure, or in other words, obtaining the required magnetic field strength while reducing the size and weight of the magnetic generating means, and the means for transferring the magnetic lines of force from the ferrite magnets.

According to the present invention there is provided an improved permanent magnet flux generating and focusing means which by actual measurement produces and transfers from to more useful magnetic flux for such applications than prior devices of the same overall weight and volume. This substantial improvement is brought about by stacking or cascading a plurality of permanent magnet ferrite rings through improved magnetic coupling and focusing means in such manner as to markedly reduce the leakage flux normally pro duced and thereby to focus and strengthen the useful flux being directed through the tube.

It is accordingly a primary object of the present invention to provide an improved ferrite permanent magnet focusing structure capable of producing greater useful flux with no increase in size or weight of the focusing means.

A further object is to provide a multiple array of ferrite permanent magnets having improved means for intercoupling the magnets to minimize leakage flux and concentrate and strengthen the useful flux generated and transferred thereby.

Other objects and many attendant advantages will be more readily comprehended by those skilled in the art after a detailed consideration of the following specification and drawings wherein:

FIG. 1 is a perspective view depicting one ferrite permanent magnet and preferred coupling means therefor, shown in exploded relation;

FIG. 2 is a cross-sectional view of one half of the magnet and coupling members through line 22 of FIG. 1;

FIG. 3 is a transverse cross-section depicting a plurality of the coupled rings of FIG. 1 in a cascaded array;

FIG. 4 illustrates the preferred coupling member in plan view and in cross-section, arranged side-by-side; and

FIG. 5 is an enlarged cross-sectional view, similar to FIG. 2 for illustrating the flux pattern produced.

Referring now to the drawings for a detailed con- 3,106,659 Patented Oct. 8, 1963 sideration of one preferred embodiment of the invention, there is shown in FIG. 1 a ferrite permanent magnet ring 10 having a central opening 11 and being formed with its north pole on the right-hand side thereof, as shown, and its south pole at its left-hand surface (not exposed). Positioned at the right-hand side of magnet 10 is a first generally ring shaped coupling member 12 of magnetically susceptible material, and positioned adjacent the left-hand side is a second identical coupling member 13, with both members in coaxial alignment with the central axis of magnet 10 to sandwich the magnet as shown in FIG. 2.

The left and right-

hand coupling members

12 and 13 are provided with hub portions 15 projecting inside magnet opening 11 to define a smaller diameter opening 14 therein.

The function of

coupling members

12 and 13 is to provide a low reluctance magnetic flux path from the magnet right-hand surface (north pole) to the magnet left-hand surface (south pole) through the central opening 11 of the magnet and do so in such manner as to focus a strong magnetic flux through this central aperture 14 through the coupling member and thence through an electron tube or the like (not shown) which may be accommodated within the opening 14.

As best shown by FIGS. 2, 4, and 5 these inwardly projecting hub portions 15 on each coupling ring are raised or thickened to form a wide inner rim surface 16 peripherally defining the central opening therein, and in cross-section having the shape of a wedge or pedestal with the wide rim surface or base thereof 16 positioned coaxially with and remote from the inner edge surface of magnet ring Iii. From the base surface 16 the

edges

17, 17a of the hubs are transferred inwardly along sides 18 as they approach the magnet 10, as shown.

As thus constructed, the coupling member 12 provides a low reluctance flux path from the north pole right-hand of magnet 10 to an enlarged rim area 16 positioned remote from the magnet and within the central aperture thereof, and the left-hand coupling member likewise provides a similar low reluctance flux path from the south pole left-hand of the magnet to a simialr enlarged rim area 16a in closely spaced side-by-side alignment with rim area 16 whereby a strong magnet flux 19 may be produced between these

rim areas

16 and 16a inside the central aperature 14, as best shown by FIG. 5.

However, since the

sides

18 and 18a of the projecting hubs are also in confronting relation a certain amount of undesired leakage flux 20 is also produced between these sides, which for purposes of the present invention is not gainfully employed for a useful purpose. Accordingly, these

sides

17 and 17a are deliberately transferred in a direction away from each other as they approach the edge ofmagnet 10 to provide a progressively increasing reluctance path to the passage of leakage flux, thereby minimizing the amount of leakage flux 20 which passes between these sides. The eifect of reducing this leakage flux 20 is to strengthen and concentrate the useful magnet flux being produced between

rim areas

16 and 16a; and actual measurement has shown that this useful flux may be increased in the order of from 5 to 10% over that otherwise being generated between these areas.

Thus the novel construction and interaction of the

coupling members

12 and 13 and magnet ring 10 focus a concentrated useful magnetic field in a direction predominantly transverse to the magnet ring, that is from 5 to 10% greater than that otherwise obtainable from a ferrite magnet of the same size and weight. Stated in another manner the magnet and coupling member construction of the present invention enables a reduction in the size and weight of these members to be obtained while producing a magnetic field of given intensity.

To provide an elongated magnetic field of this type to encircle the long neck portions of a microwave or other electron tube for focusing purposes, a plurality of these ferrite permanent magnets and coupling members therefor may be cascaded or stacked in the manner shown by FIG. 3. As shown each of the ring magnets are disposed in axial alignment, with a coupling member, as described above, being intermediate each pair of magnet rings and also in axial alignment therewith, thereby to provide an elongated magnetic field transversely through the central openings of the magnets and coupling members in the direction as indicated by the arrowed line 21 entitled Flux.

What is claimed is:

1. In a ferrite magnet focusing assembly for microwave tubes, a plurality of ferrite ring permanent magnets in cascaded relation with their central openings in axial alignment to accommodate an electron passage means, and means for concentrating and focusing the fiux generated thereby in an axial direction through said aligned openings, said means consisting of a plurality of magnetic separating members, one member being intermediate each pair of ferrite rings and each being formed with a smaller diameter central opening than said magnet and having an elongated and symmetrical wedge shaped portion symmetrical in cross section defining said smaller diameter opening, thereby to focus a strong magnetic field axially along said opening, each of said wedgeshaped portions extending over a portion of the project ing width of the tubular central section surrounding the smaller diameter opening of each magnetic separating member, each of said magnetic separating members having a shoulder integral with each side thereof, each of said shoulders being located radially near the wedgeshaped portion of the magnetic separating member, the ferrite rings extending outward from the shoulders of the magnetic separating members.

2. In a device of the class described, a plurality of ring shaped ferrite permanent magnets in cascaded array, a ring shaped magnetically susceptible member intermediate each pair of magnets, the magnetically susceptible members on each side thereof providing a low reluctance path from one pole of the ring magnet to an enlarged annular area within the ring opening and coaxial therewith, with said enlarged areas being in side by side relationship and the edges thereof being closely spaced together, the portions of each magnetically susceptible member adjoining said area being progressively recessed away from the confronting portions of the other in a direction toward the magnet thereby to provide a progressively increasing reluctance path between said confronting portions, whereby in cross section each said magnetically susceptible member is in the form of a symmetrical T-shaped pedestal having a flat enlarged base and inwardly tapered sides thereby to minimize leakage flux, the recessed portion of each T-shaped pedestal extending over a portion of the projecting width of the base of the pedestal, each of said magnetically susceptible members having a shoulder integral with each side thereof, each of said shoulders being located radially near the T-shaped pedestal, the ring opening through each of said ring-shaped permanent magnets being fitted to a pair of said shoulders, each ring-shaped permanent magnet extending outward from a pair of shoulders of adjoining magnetically susceptible members, and said ring permanent magnets and ring shaped magnetically suseptible members having mating sides and edges interfitting with one another in aligned coaxial array thereby to provide a unitary assembly of minimum Weight and volume.

References Cited in the file of this patent UNITED STATES PATENTS 2,843,775 Yasuda July 15, 1958 2,847,607 Pierce Aug. 12, 1958 2,875,273 Bailey Feb. 24, 1959 2,876,373 Veith et a1 Mar. 3, 1959 2,882,439 Nishio et al Apr. 14, 1959 2,895,066 Yasuda July 15, 1959 2,911,554 Kompfner et al Nov. 3, 1959 2,945,153 Chang July 12, 1960 2,956,200 Bates Oct. 11, 1960 2,965,782 Weaver Dec. 20, 1960

Claims

1. IN A FERRITE MAGNET FOCUSING ASSEMBLY FOR MICROWAVE TUBES, A PLURALITY OF FERRITE RING PERMANENT MAGNETS IS CASCADED RELATION WITH THEIR CENTRAL OPENINGS IN AXIAL ALIGNMENT TO ACCOMMODATE AN ELETRON PASSAGE MEANS, AND MEANS FOR CONCENTRATING AND FOCUSING THE FLUX GENERATED THEREBY IN AN AXIAL DIRECTION THROUGH SAID ALIGNED OPENINGS, SAID MEANS CONSISTING OF A PLURALITY OF MAGNETIC SEPARATING MEMBERS, ONE MEMBER BEING INTERMEDIATE EACH PAIR OF FERRIER RINGS AND EACH BEING FORMED WITH A SMALLER DIAMETER CENTRAL OPENINGS THAN SAID MAGNET AND HAVING AN ELONGATED AND SYMMETRICAL WEDGE SHAPED PORTION SYMMERTICAL IN CROSS SECTION DEFINING SAID SMALLER DIAMETER OPENING, THEREBY TO FOCUS A STRONG MAGNETIC FIELD AXIALLY ALONG SAID OPENING, EACH OF SAID WEDGESHAPED PORTIONS EXTENDING OVER A PORTION OF THE PROJECTING WIDTH OF THE TUBULAR CENTRAL SECTION SURROUNDING THE SMALLER DIAMETER OPENING OF EACH MAGNETIC SEPARATING MEMBER, EACH OF SAID MAGNETIC SEPARATING MEMBERS HAVING A SHOULDER INTEGRAL WITH EACH SIDE THEREOF, EACH OF SAID SHOULDER BEING LOCATED RADIALLY NEAR THE WEDGESHAPED PORTION OF THE MAGNETIC SEPARATING MEMBER, THE FERRITE RINGS EXTENDING OUTWARD FROM THE SHOULDERS OF THE MAGNETIC SEPARATING MEMBERS.