US3403292A

US3403292A - Coolant flow means utilizing tubing of dielectric material

Info

Publication number: US3403292A
Application number: US582474A
Authority: US
Inventors: Walter J Griffin
Original assignee: Navy Usa
Current assignee: US Department of Navy
Priority date: 1966-09-26
Filing date: 1966-09-26
Publication date: 1968-09-24
Anticipated expiration: 1985-09-24

Description

Sept. 24, 1968 w. J. GRIFFIN 3,403,292

COOLAN'T FLOW MEANS UTILIZING TUBING OF DIELECTRIC MATERIAL Filed Sept. 26, 1966 2 Sheets-Sheet 1 WHmH -gi I l Ill:

IIJHUH INVENTOR. 1 Walter J.Griffin Sept. 24, 1968 w. J. GRIFFIN 3,403,292

COOLANT FLOW MEANS UTILIZING TUBING OF DIELECTRIC MATERIAL Filed Sept. 26, 1966 2 Sheets-Sheet 2 INVENTOR. Woll)er J. Griffin United States Patent O 3,403,292 COOLANT FLOW MEANS UTILIZING TUBING OF DIELECTRIC MATERIAL Walter J. Griflin, Sudbury, Mass, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Sept. 26, 1966, Ser. No. 582,474 7 Claims. (Cl. 315-50) ABSTRACT OF THE DISCLOSURE oil-seal flange.

This invention relates to electron discharge devices and, more particularly, to high power output devices in which cooling is required to permit increased high average power operation.

As high power levels are reached in the operation of amplifier tubes such as the microwave crossfield amplifier tube, the tubes cathode absorbs energy from electrons which are returned by the interaction process. This backbombardment by electrons is relatively unimportant in low power devices but becomes exceedingly important in higher power devices because the back-bombardment energy adds to the heating of the cathode as the operating power level is increased. Eventually the cathode is raised to such high temperatures that radiation cooling is ineffective, resulting in melted or vaporized materials therein.

In the field, the melting and vaporization of cathode materials has defined an upper limit to the operating average power levels attainable by devices incorporating these tubes. In the laboratory, this power limitation has been avoided by causing liquid coolant to flow from open receptacles through the cathode structure to remove heat in the same or similar manner as liquid coolants are used in many heated devices.

Several disadvantages are inherent in prior cathode cooling devices of the type mentioned, perhaps the most serious being the exposure of personnel to a coolant which is at the same high voltage as the cathode. Although insulation may be provided along the coolant path between the cathode and the coolant source, there is no known device or method for making the coolant lines and connections compatible with conventional tube systems. In particular, where high voltage bushings are immersed in insulating oil there is no known device or method for introducing coolant fluid into the cathode structure through an oil chamber without effecting major alterations to the structure and chamber. The microwave crossfield amplifier tube is an example of an important microwave component which is increasing in use and requires cathode cooling means not available at the present state of the art.

One embodiment of the present invention solves the problem of mounting higher powered microwave crossfield amplifier tubes and coolant lines therefor in conventionally oil-insulated systems by providing for safe and practical entrance and egress of the cathode coolant without significantly affecting normal high power output tube mounting arrangements.

Accordingly, it is an object of the present invention to provide a novel method of and means for applying coolant to the cathodes of high power output devices.

Another object of the present invention is to provide means for cooling the cathode structure of tubes operating at high average power such as microwave crossfield amplifier tubes without exposing personnel to lethal high voltages.

A further object of this invention is to provide a novel means of and method for entrance and egress of cathode coolant in high power output devices without significant change in conventional tube mounting structure.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is an elevation view, partly cut away, of a power tube embodying the present invention; and

FIG. 2 is an enlarged view, in section, of the novel features of the invention in relation to the structure of a conventional power tube.

Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the views, and more particularly to FIG. 1, a high power output tube such as Amplitron tube 11 is shown supported on a chamber 12 which contains a pulse transformer 13 and is filled with insulating oil as indicated at 14. Tube 11 is a microwave crossfield amplifier tube having a cathode 15 located along an axis 16 which is concentric with the tube anode 17. Anode cooling is not a part of this application but is effected through an inlet 18, tubes 19 and an outlet 20, all of which are outside of chamber 12 and, therefore, present no problem such as that posed in providing cathode cooling.

Excessive cathode heating is controlled by removing the excess heat from the cathode via a liquid coolant which is forced to flow from a coolant source, not shown, through conduit means which include an inlet tube 23 and an outlet tube 24, both of which are disposed entirely Within chamber 12 and its sealing flange 25. Since, in the embodiment illustrated, chamber 12 is hermetically sealed at flange 25, a pair of

coolant lines

27 and 28 are connected to passages through the oil-seal flange 25 in

fittings

29 and 30, respectively, so as to maintain the integrity of the hermetically sealed chamber. In oil-filled chamber 12, high voltage exists at 32 and ground potential at 33, these being separated by an insulator 34. Inlet and

outlet tubes

23 and 24, respectively, are nonconducting and flexible and preferably are made of high dielectric strength tubing. Conventional sealing components, such as externally threaded connections 36, nuts 37 and adapters 38, are used at the ends of

tubes

23 and 24.

FIG. 2 shows the cathode structure in enlarged cross section as comprising an outer conductive sleeve 40 to which a cathode emitter 41 is attached and a centrally disposed inner sleeve 42 which provides an inlet passage 44 for coolant fluid. An outlet passage 45 is formed between outer conductive tube 40 and inner sleeve 42. High voltage applied at the lower end of the structure to a connector 48 is conducted through inlet cap 49, lower plate 50, collar 51 and upper plate 52 to the lower end 55 of insulator 32. Sleeve 42 and cap 49 are attached to lower plate in sealing engagement therewith, plate 50 also receiving in sealing engagement an outlet cap 56. Cap 49 provides a plenum for intake coolant while collar 51 and cap 56 form a plenum 57 for discharge coolant. Plate 50 supports and centers inlet sleeve 42 in the device although additional centering means, not shown, may be included adjacent the end of the tube remote from plate 50 to insure that sleeve 42 remains in the desired position. Outer sleeve 40 receives support and centering from an insert 58 in upper plate 52. A central support member such as pole piece 59 is provided which is maintained at ground potential and spaced an appropriate distance from the high voltage of cathode support sleeve 40. A pair of

end hats

60 and 61 are positioned on and supported by the cathode for the purpose of shaping electrical fields in the device.

On the exposed side 65 of sealing flange 25, fittings 30 are secured in sealing engagement on a pair of externally threaded

tube stubs

66 and 67, respectively. A venting chamber 70 is formed by a flanged plate 72 and flange 25.

Tube stubs

66 and 67 pass through venting chamber 70 to preserve the integrity of the cooling system. The

stubs

66 and 67 connect fittings 29 and 3G to

tubes

23 and 24, respectively. Flange 72 is perforated as shownat 73 to provide communication between housing 12 and chamber 70. Flange 25 has a hole, not shown, in its exposed side 65 to receive a vent fitting, not shown, permitting air trapped in housing 12 to be vented therefrom after the housing has been scaled.

A source of coolant, not shown, and pumping means, not shown, complete the cooling system. Since the entire cooling system is electrically grounded at flange 25, there is no danger of exposing personnel to lethal voltages. Coolant enters through line 27, fitting 29, stub 66 and inlet tube 23, thence is directed into inlet cap 49 and through passage 44 in inner sleeve 42 to the region of cathode emitter 41. The return flow is directed downward past the cathode emitter region and through passage 45 to plenum 57 between

plates

50 and 52, thence through cap 56, outlet tube 24, stub 67, fitting 30 and line 28, to a heat exchanger, not shown, or directly to the coolant source.

Coolant lines

27 and 28 and

tubes

23 and 24 preferably are made of flexible high strength dielectric material to provide for differential expansion and resistance to impact damage. Negligible leakage current losses occur in such lines, and their composition is selected for chemical inertness to the oils and coolant fluids encountered. The material of the lines further has the property of being capable of forming a seal with the metal fittings and terminal connections of the device.

By having the coolant path traverse oil-seal flange 25, the conventional high voltage bushing oil seal may be made in the usual manner thereby avoiding a necessity for installing separate oil seals in additional openings in chamber 12. A positive electrical ground of the coolant is provided by a ground connection 74 at the oil-seal flange.

There is thus provided a safe, simple method of and means for removing excess heat from a cathode structure during high voltage operation. The invention is readily adaptable for use in other tube types as well as in foreseeable future high power tube devices and should make possible increased average power ratings therein.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a microwave crossfield amplifier device having an isolated high voltage connection, the combination therewith of:

means for cooling at least a non-isolated portion of said device; said cooling means including a coolant source disposed externally of the isolated portion of said device;

said cooling means further including a coolant fluid and conduit means for conducting said fluid through said device; and

said conduit means having inlet and outlet connections to said non-isolated portion of the device disposed in the isolated portion thereof.

2. The device of claim 1 wherein said high voltage connection is disposed in a chamber;

said chamber being filled with insulating oil and sealed;

and

said non-isolated portion of the device includes the cathode thereof whereby coolant fluid is introduced into the device and exited therefrom through conduit means which are disposed at least partly within the insulating oil in said chamber.

3. The device of claim 1 wherein said chamber is sealed by a sealing flange; and

said conduit means are admitted into the chamber through said sealing flange.

4. The device of claim 3 wherein said conduit means includes an inlet section and an outlet section disposed within said chamber;

said inlet and outlet sections composed of flexible nonconducting material.

5. The device of claim 4 wherein said conduit means further includes a centrally disposed inlet passage extending through said flange to a point beyond said cathode; and

an outer return passage concentrically disposed about the inlet passage and terminating Within said chamber.

6. The device of claim 5 wherein said crossfield microwave amplifier includes a non-conducting central support member attached to said flange;

said support member disposed externally of said chamber;

a high voltage connector disposed within said chamber remote from said central support member for conducting high voltage thereinto;

passage forming means connecting said high voltage connector and said cathode; and

insulating means disposed in said chamber concentrically spaced about at least a portion of said passage forming means.

7. The device of claim 6 and further including a centrally disposed inner elongated sleeve extending from a position adjacent said high voltage connector to a point beyond said cathode;

an outer sleeve concentrically disposed about and spaced from said inner sleeve;

said passage forming means forming a plenum at the end of said outer sleeve;

said plenum communicating with said outlet section;

said outer sleeve extending beyond said inner sleeve in the vicinity of said cathode to permit intercommunication of said inlet and said outer passages so that coolant fluid entering through said inlet section will traverse said inner sleeve and thence said outer passage past said cathode to said plenum and out through said outlet section.

References Cited UNITED STATES PATENTS 2,544,664 3/1951 Garner et a1. 313-32 X 2,546,773 3/1951-=Nelson 315- X 2,574,562 11/1951 Hansell 313-32 X 2,768,329 10/1956 Smith 313-32 X 2,787,730 4/1957 Berghaos et al 315-50 X JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner.