US3761764A

US3761764A - Piezo-electrically induced hydraulic movement of a magnetron tuning element

Info

Publication number: US3761764A
Application number: US00227366A
Authority: US
Inventors: Brady M Barry
Original assignee: English Electric Valve Co Ltd
Current assignee: Teledyne UK Ltd
Priority date: 1971-03-17
Filing date: 1972-02-18
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25
Also published as: NL7202680A; DE2211461A1; SE367276B; GB1367671A

Abstract

The tuning member of a magnetron is moved hydraulically by liquid which is moved by a piezo-electric element. The piezoelectric element forms part of a chamber containing the liquid, the tuning member being moved by the movement of the liquid in a conduit, of relatively small bore, in communication with the chamber. There may be two chambers and two conduits, providing a push-pull arrangement for moving the tuning member.

Description

I United States Patent 1 [111 3,761,764

Brady Sept. 25, 1973 [54] PIEZO-ELECTRICALLY INDUCED 3,478,246 11/1969 Perkins et a1. 315/3961 X HYDRAULIC MOVEMENT OF A 3,671,801 6/1972 Masek.... 315/3961 3,478,247 11/1969 Hull .1 315/3961 X MAGNETRON TUNING ELEMENT 3,187,220 6/1965 Dench.... 315/3961 X [75] Inventor; Michael Barry Brady, Maldon, 2,589,885 3/1952 Sonkin 315/3959 England [73] Assignee: English Electric Valve Company Primary ExaminerRudolph V. Rolinec Limited, Chelmsford, England Assistant ExaminerSaxfield Chatmon, Jr. [22] Filed: Feb 18, 1972 Atl0rneyDonald M. Wight et al.

[21] Appl. No.: 227,366

[57] ABSTRACT 30 F A l' t' 't orelgn pp y Data The tuning member of a magnetron is moved hydrauli- Mar. 17, Great Bi'llall'l uy is moved a piezo electric ment. The piezo-electric element forms part of a cham- [22] Cl 315/3961, BIS/39.55, 315739.77 Containing the liquid; the tuning member being .1; movcd the movement Of the in a conduit of 1 held 0 Search 5/39" relatively small bore, in communication with the cham- 39'57 ber. There may be two chambers and two conduits, rovidin a ushull arran ement for movin the tun- [56] References Cited p g g UNITED STATES PATENTS 3,262,009 7/1966 Sibley 315/396] 7 Claims, 6 Drawing Figures PATENTEDSEP25|975 3761.764

SHEET 10F 3 PATENTEDSEPZSlHH SHEET 2 [IF 3 nae PATENTEUSEMSM 3,761,764

SHEET 3 BF 3 PIEZO-ELECTRICALLY INDUCED HYDRAULIC MOVEMENT OF A MAGNETRON TUNING ELEMENT This invention relates to magnetrons and more specifically to magnetrons of the kind in which there is provided at least one member, which in some cases is metallic and in others is of dielectric material, and means for moving the same in relation to the anode block of the magnetron to vary the frequency generated thereby. There are many known varieties of magnetron of this kind and moving member or members of various forms have been proposed for example a moving member in the form of a metal ring carried adjacent one end of the anode block of a so-called rising sun" magnetron and movable towards and away from the block or one or more moving members in the form of one or more metal or dielectric slugs inserted in and movable to and fro endwise with respect to one or more of the holes in the anode block of a so-called hole and slot magnetron.

Considerable difficulties are experienced in designing satisfactory magnetrons of the kind referred to and the practical requirements are by no means easy to satisfy together. These requirements include providing an adequate range of variation of frequency for tuning or frequency modulation purposes and this involves providing an adequate range of movement of the tuning member or members; avoiding disturbing effects due to mechanical resonances in the mechanically moving system which includes the moving member or members and the driving means therefor such avoidance is particularly difficult to achieve if the movement of the driving means is much smaller than the required movement of the moving member or members; securing a sufficiently rapid response of the moving member or members and therefore a sufficiently rapid change is generated frequency when a control force is applied to move the driving means for said member or members; and making the whole mechanically moving system such as to avoid the need for expensive and mechanically unsatisfactory or inefficient expedients, such as magnetic driving links and making parts of the evacuated envelope of the magnetron of flexible construction (as has been proposed) in order to transmit mechanical drive from driving means outside the said envelope to a moving member or members inside it. Also a wide variety of electro-mechanical transducers has been proposed in order .to translate a control voltage into mechanical movement of a driving device. Such transducers include electro-magnetic transducers such as solenoids and piezo-electric transducers. Piezo-electric transducers have the advantages of high efficiency, low losses, and an ability to provide powerful mechanical driving forces. They have however the important defect that the mechanical movement obtainable therefrom is of small amplitude. If, in order to overcome this, a mechanical drive of large mechanical advantage is used to obtain, from a piezo-electric driving transducer, mechanical movement of adequate extent from a driving member or members driven thereby, the already mentioned difficulties of disturbance by resonant effects and limitation of rapidity of response arise. Moreover the mounting of a piezo-electric transducer inside the evacuated envelope of a magnetron has the disadvantage that its operation may become impaired by the sputtering of metal on the crystal between its electrodes and/or by the effects of heating, for the Curie point of currently available piezo-electric crystals is relatively low, being only about 300 C. If the crystal is mounted outside the evacuated envelope there is the problem of providing a satisfactory mechanical drive through said envelope.

The present invention seeks to provide a solution of the foregoing difficulties.

According to this invention in its broadest aspect a magnetron of the kind referred to comprises at least one liquid-filled chamber, piezo-electric means for varying the volume of said chamber, liquid filled conduit means in communication with the liquid in said chamber and a moving member or members adapted, upon movement thereof to vary the frequency of said magnetron, and hydraulically driven through said conduit, the whole arrangement being dimensioned to provide, in response to a given movement of said piezoelectric means, a movement of said member or members magnified by mechanical advantage obtained hydraulically.

Preferably there are two chambers, two piezoelectric means, one for each chamber, and two conduits of relatively small bore, one leading from each chamber to hydraulic means for driving the moving member or members; and the piezo-electric means are arranged to be activated in phase opposition so that the said member or members are driven in one direction through one conduit and in the other through the other.

Preferably the chamber or each chamber, has part of its wall constituted by a body of piezo-electric crystal so that the chamber and piezo-electric means are unitary with one another to constitute a chamber, the volume of which will be varied by mechanical movements of the crystal body.

Preferably again each chamber consists of a cylindrical piezo-electric member and means are provided for simultaneously applying equal and opposite drive signals, one to each cylinder, whereby one axially contracts whilst the other axially expands.

Preferably the hydraulic means for driving the moving member or members is constituted by a further small bore conduit connected between the two conduits and arranged to extend inside the evacuated envelope of the magnetron through a tuning cavity therein.

In this case the tuning member could be a dielectric or metal slug housed in the further small bore conduit.

For maximum tuning effect it is preferable to have one tuning member for each cavity. However, where the magnetron is of the external cavity type it is sufficient to have one tuning member for that cavity.

The invention is illustrated in and further described by way of example with reference to the accompanying drawings in which FIG. 1 is a diagrammatic part sectional view of one embodiment of the invention. FIG. 2 is a diagrammatic part sectional view of modification of the embodiment shown in FIG. 1. FIG. 3 is a diagrammatic sectional view of a preferred embodiment of the invention. FIG. 4 is a perspective sketch of an anode block broken away to better illustrate a detailed portion of the present invention and its operation. FIG. 5 is a sectional view showing a system as used with the preferred embodiment of the invention; and FIG. 6 is a view illustrating a conventional coaxial magnetron to which the invention is applied. The remaining parts of the magnetron are standard and have not therefore been illustrated. Like references denote like parts in the drawings.

Referring to FIG. 1 this shows a fluid chamber I having a cylindrical body portion 2 of piezo-electric material and end seals 3 and 4. End seal 4 has'a central aperture in which is mounted one end of a small bore conduit 5. The other end of the conduit 5 is connected to a similarly apertured end seal 6 of a flexible bellows 7 which has another end seal 8 to which is connected a tuning element 9.

- In operation drive signals are applied (by means not shown) to the piezo-electric cylinder 2 to cause the cylinder 2 to axially expand and contract, thus effectively expanding and contracting the volume enclosed by the chamber 1. This forces fluid from the chamber 1 along conduit 5 and moves the tuning element 9 via the flexible bellows 7.

Referring now to FIG. 2 this shows two

fluid chambers

10 and 11 connected via two

conduits

12 and 13 to opposite ends 14 and 15 respectively of a double flexible bellows 16. The bellows 16 includes an apertured plate 17 which is fixedly mounted on a rod 18. The rod 18 has its ends mounted one in conduit 12 and the other in conduit 13 and is a sliding fit therein. The apertured plate 17 has a lug 19 extending externally of the bellows 16 which carries a tuning element 20.

In operation fluid is forced from either chamber 10 or 11 (they operate in phase opposition, i.e., as one expands the other contracts) along

conduits

12 or 13 respectively to move rod 18. Since this is rigidly connected to plate 16 this causes the plate to move axially (as indicated by the double-headed arrow) which in turn moves the tuning element.

Referring now to FIG. 3 this shows two

fluid chambers

21, 22, having piezo-

electric cylinders

23, 24 respectively, joined back to back with a common wall 25. The

chambers

21, 22 have

end walls

26, 27 respectively sealed into which are small

bore metal conduits

28 and 29 respectively. These

conduits

28, 29 are joined at their free ends to a further small bore conduit 30 of ceramic in which is housed a metal tuning slug 3]. The

piezoelectric cylinders

23, 24 are each coated with inner and outer layers of metal M to which drive signals may be applied from a signal source S via leads L. The leads are connected so that equal and opposite signals are applied to the cylinders. Whilst described as being of metal the slug 31 could be made of dielectric.

In operation when suitable drive signals are applied from source S to piezo-

electric cylinders

23, 24, one chamber, say chamber 21 will expand and the other chamber 22 will simultaneously contract, forcing fluid from chamber 22 along conduit 29 via conduit 30 to conduit 28 and thus into chamber 21. This movement of fluid will move the metal slug 31 toward conduit 28.

Similarly, if the drive signal is reversed and chamber 21 axially contracts whilst chamber 22 axially expands, fluid will be forced in the reverse direction carrying the slug 31 with it.

Referring now to FIG. 4 this shows an anode block 32 of the so called "hole and slot" type which has been partly broken away to leave five holes H. FIG. 5 illustrates part of the system as described above in conjunction with FIGS. 3 and 4.

This drawing shows how the arrangement of FIG. 3 can be applied to a conventional magnetron. In this case the

conduits

28, 29, extend outside the magnetron envelope (not shown) and conduit 30 ex-tends iide the envelope through hole H. It can be seen that the slug 31 can thus be controlled to move up and down in the hole H, the extent of move-ment being indicated by the double headed arrow. This enables tuning to be effected in a simple manner with the piezo-

electric crystal members

23, 24 outside of the magnetron envelope.

In FIG. 6, a conventional coaxial magnetron is shown and in which there is included the cathode 33, inner anode 34 and outer anode 35 to present the usual external cavity 36. For such an arrangement, a single tuning element operated as described above is employed as shown. Thus, the small bore conduit 30' contains the tuning element 31 operated as described above in conjunction with FIGS. 3-5.

I claim:

1. In a magnetron having at least one tuning element, at least one hollow body defining a liquid-filled chamber, piezo-electric means forming a portion of said body for varying the volume of said chamber, and hydraulic means communicating with the interior of said chamber for moving said tuning element in response to variations in the volume of said chamber, said hydraulic means defining a second chamber acting against said tuning element in which said second chamber is of a volume substantially less than the volume of the chamber first mentioned, whereby a given movement of said piezo-electric means effects a movement of said tuning element which is magnified by mechanical advantage gained hydraulically.

2. In a magnetron as defined in claim 1 including a second hollow body defining a third chamber, second piezo-electric means forming a portion of said second body for varying the volume of said third chamber, second hydraulic means communicating with the interior of said third chamber for moving said tuning element in response to variations in volume of said third chamber, said second hydraulic means defining a fourth chamber acting against said tuning element in opposition to the hydraulic means first mentioned and in which the volume of said fourth chamber is substantially less than the volume of said third chamber, and means for energizing said piezo-electric means first mentioned and said second piezo-electric means in phase opposition.

3. In a magnetron as defined in claim 2 wherein each piezo-electric means is in the form of a cylindrical body provided for the external cavity thereof.

t ll 4' i t

Claims

3. In a magnetron as defined in claim 2 wherein each piezo-electric means is in the form of a cylindrical body portion.

4. In a magnetron as defined in claim 2 wherein said first and second hydraulic means are integrally formed as a small bore conduit and said tuning element is fitted slidably therein.

5. In a magnetron as defined in claim 4 wherein said tuning element is a dielectric or metal slug.

6. A magnetron as claimed in claim 1 and wherein there is one tuning member for each cavity.

7. A magnetron as claimed in claim 1 and of the external cavity type and wherein one tuning member is provided for the external cavity thereof.