GB1574315A - Electronic vacuum devices - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRONIC VACUUM DEVICES (71) We ENGLISH ELECTRIC VALVE COMPANY LIMITED, a British Company of 106, Waterhouse Lane, Chelmsford, Essex, CM1 2QU, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electronic vacuum devices and in particular, but not exclusively, to magnetrons.

Many electronic vacuum devices include supporting structures for electrodes such as cathodes and grids, which supporting structures comprise annular members. Many such devices, and in particular magnetrons, are required to be operated under conditions of vibration at audio frequencies.

Commonly the supporting structures have mechanical resonances at audio frequencies which tend to have high Q (magnification) values, which in turn tend to lead to relatively large amplitudes of movement.

Not only can this movement cause mechanical failure of the supporting structures, but also undesired modulation of the amplification or oscillation of the devices can be caused.

The present invention seeks to provide an improved electronic vacuum device including a supporting structure for an electrde, which supporting structure comprises an annular member, in which the above difficulty is reduced.

According to this invention an electronic vacuum device including at least one internal electrode having a supporting structure comprising an annular member, which structure is subject to vibration at audio frequencies is provided, wherein the supporting structure of said electrode is arranged to be damped by acoustically lossy material held against the outer surface of said annular member.

Said electronic vacuum devices may be a magnetron and said internal electrode may be a cathode or control grid.

Preferably said acoustically lossy means comprises one or more retaining members holding lossy material against said outer surface of said annular member. Said retaining member or each retaining member may form, with said outer surface of said annular member, an enclosure having a filling of acoustically lossy material.

Preferably said enclosure formed may be annular and extend around said outer surface of annular member.

A plurality of annular enclosures may be formed around said outer surface of said annular member, if desired formed by a common retaining member.

Said lossy material may be comprised of relatively hard, heavy grains of powder, such as, for example, alumina, silicon carbide and tungsten.

The use of alumina powder is convenient, where electrical insulation is required.

The or each enclosure may be hermetically sealed and a dried inert gas and/or dessicant introduced, thereby to reduce any tendency for the powder filling to consolidate at low temperatures.

Said lossy material may also comprise viscous material, such as bitumen or oil, which may be loaded with inertial elements, for example small spheres of dense insulating material. Such lossy material may be provided in enclosures as hereinbefore described or retained between said outer surface of said annular member and another member which two members tend to have relative motion as a result of acoustic vibration.

Said lossy material may also be solid, e.g.

silicon rubber.

The invention is illustrated in and further described with reference to the drawing accompanying the provisional specification in which, Figures I to 3 represent three different magnetron cathode structures in magnetrons in accordance with the present invention.

In all Figures like references are used for like parts, and indeed apart from the nature of the damping means provided, the cathodes shown in Figures 1 and 3 are similar.

Referring to Figure 1, the arrangement consists of an anode 1, which encloses a cathode 2 and is mounted upon a mounting 3. An opening 4 acts as an output port.

The cathode 2 is carried from a conical member 5, which forms the heater for the cathode 2. The conical member 5 extends into a general cylindrical side extension 6, having an annular insulator 7 along its length. The general cylindrical side extension 6 supports the conical member 5 and hence the cathode 2, from one end 8 provided as a heater terminal. As so far described, the magnetron oscillator is as well known per se.

In accordance with the present invention, surrounding the insulating portion 7 of the side extension 6 is a retaining member 9, which forms a plurality (in this case two) or enclosures, each containing alumina powder 10. Each chamber is separated from the other by an internal web 11, forming part of the common retaining member 9. The enclosures having the powdered filling 10 are hermetically sealed and dried inert gas is introduced in order to reduce any tendency for the powder to consolidate at low temperatures.

Referring to Figure 2, in this case a retaining member 12 surrounds the insulating portion 7 to form a single annular enclosure into which viscous material, in this case oil, 13, is introduced. The oil 11 is loaded with inertial elements in order to increase the damping effect.

Referring to Figure 3. in this case a band 14 of solid acoustically lossy material is provided around the insulating portion 7. In this case. no retaining member is necessary.

The solid lossy material used in this particular example is silicon rubber.

WHAT WE CLAIM IS: 1. An electronic vacuum device including at least one internal electrode having a supporting structure comprising an annular member, which structure is subject to vibration at audio frequencies and wherein the supporting structure of said electrode is arranged to be damped by acoustically lossy material held against the outer surface of said annular member.

2. An electronic vacuum device as claimed in claim 1 and in the form of a magnetron.

3. A device as claimed in any of the above claims and wherein said internal electrode is a cathode or control grid.

4. A device as claimed in any of the above claims and wherein said acoustically lossy means comprises one or more retaining members holding lossy material against said outer surface of said annular member.

5. A device as claimed in claim 4 and wherein said retaining member or each retaining member form, with said outer surface of said annular member, an enclosure having a filling of acoustically lossy material.

6. A device as claimed in claim 5 and wherein said enclosure formed is annular and extends around said outer surface of said annular member.

7. A device as claimed in claim 6 and wherein a plurality of annular enclosures are formed around said outer surface of said annular member.

8. A device as claimed in claim 7 and wherein said plurality of annular enclosures are formed by a common retaining member.

9. A device as claimed in any of the above claims and wherein said lossy material is comprised of relatively hard, heavy grains of powder.

10. A device as claimed in claim 9 and wherein said powder is alumina or silicon carbide or tungsten.

11. A device as claimed in claim 9 or 10 as dependent upon claim 5 and wherein the or each enclosure is hermetically sealed and a dried inert gas and/or dissicant introduced, thereby to reduce any tendency for the powder filling to consolidate at low temperatures.

12. A device as claimed in any of claims 1 to 8 and wherein said lossy material comprises viscous material.

13. A device as claimed in claim 12 and wherein said viscous material is bitumen or oil.

14. A device as claimed in claim 12 or 13 and wherein said viscous material is loaded with inertial elements.

15. A device as claimed in claim 14 and wherein said inertial elements comprise small spheres of dense insulating material.

16. A device as claimed in any of claims 12 to 15 as dependent upon claim 1 or 2 and wherein said lossy material is retained between said outer surface of said annular member and another member which two members tend to have relative motion as a result of acoutsic vibration.

17. A device as claimed in any of claims 1 to 8 and wherein said lossy material is solid.

18. A device as claimed in claim 17 and wherein said lossy material is silicon rubber.

19. An electronic vacuum device including at least one internal electrode having a supporting structure subject to vibration at

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. in which, Figures I to 3 represent three different magnetron cathode structures in magnetrons in accordance with the present invention. In all Figures like references are used for like parts, and indeed apart from the nature of the damping means provided, the cathodes shown in Figures 1 and 3 are similar. Referring to Figure 1, the arrangement consists of an anode 1, which encloses a cathode 2 and is mounted upon a mounting 3. An opening 4 acts as an output port. The cathode 2 is carried from a conical member 5, which forms the heater for the cathode 2. The conical member 5 extends into a general cylindrical side extension 6, having an annular insulator 7 along its length. The general cylindrical side extension 6 supports the conical member 5 and hence the cathode 2, from one end 8 provided as a heater terminal. As so far described, the magnetron oscillator is as well known per se. In accordance with the present invention, surrounding the insulating portion 7 of the side extension 6 is a retaining member 9, which forms a plurality (in this case two) or enclosures, each containing alumina powder 10. Each chamber is separated from the other by an internal web 11, forming part of the common retaining member 9. The enclosures having the powdered filling 10 are hermetically sealed and dried inert gas is introduced in order to reduce any tendency for the powder to consolidate at low temperatures. Referring to Figure 2, in this case a retaining member 12 surrounds the insulating portion 7 to form a single annular enclosure into which viscous material, in this case oil, 13, is introduced. The oil 11 is loaded with inertial elements in order to increase the damping effect. Referring to Figure 3. in this case a band 14 of solid acoustically lossy material is provided around the insulating portion 7. In this case. no retaining member is necessary. The solid lossy material used in this particular example is silicon rubber. WHAT WE CLAIM IS:

1. An electronic vacuum device including at least one internal electrode having a supporting structure comprising an annular member, which structure is subject to vibration at audio frequencies and wherein the supporting structure of said electrode is arranged to be damped by acoustically lossy material held against the outer surface of said annular member.

2. An electronic vacuum device as claimed in claim 1 and in the form of a magnetron.

3. A device as claimed in any of the above claims and wherein said internal electrode is a cathode or control grid.

4. A device as claimed in any of the above claims and wherein said acoustically lossy means comprises one or more retaining members holding lossy material against said outer surface of said annular member.

5. A device as claimed in claim 4 and wherein said retaining member or each retaining member form, with said outer surface of said annular member, an enclosure having a filling of acoustically lossy material.

6. A device as claimed in claim 5 and wherein said enclosure formed is annular and extends around said outer surface of said annular member.

7. A device as claimed in claim 6 and wherein a plurality of annular enclosures are formed around said outer surface of said annular member.

8. A device as claimed in claim 7 and wherein said plurality of annular enclosures are formed by a common retaining member.

9. A device as claimed in any of the above claims and wherein said lossy material is comprised of relatively hard, heavy grains of powder.

10. A device as claimed in claim 9 and wherein said powder is alumina or silicon carbide or tungsten.

11. A device as claimed in claim 9 or 10 as dependent upon claim 5 and wherein the or each enclosure is hermetically sealed and a dried inert gas and/or dissicant introduced, thereby to reduce any tendency for the powder filling to consolidate at low temperatures.

12. A device as claimed in any of claims 1 to 8 and wherein said lossy material comprises viscous material.

13. A device as claimed in claim 12 and wherein said viscous material is bitumen or oil.

14. A device as claimed in claim 12 or 13 and wherein said viscous material is loaded with inertial elements.

15. A device as claimed in claim 14 and wherein said inertial elements comprise small spheres of dense insulating material.

16. A device as claimed in any of claims 12 to 15 as dependent upon claim 1 or 2 and wherein said lossy material is retained between said outer surface of said annular member and another member which two members tend to have relative motion as a result of acoutsic vibration.

17. A device as claimed in any of claims 1 to 8 and wherein said lossy material is solid.

18. A device as claimed in claim 17 and wherein said lossy material is silicon rubber.

19. An electronic vacuum device including at least one internal electrode having a supporting structure subject to vibration at

audio frequencies and substantially as herein described with reference to the drawing accompanying the provisional specification.