US3351801A - Cathode cylinder having a heater member supported by a plurality of flexible metal bands - Google Patents

Description

Nov. 7, 1967 F. RICHTER 3,351,801

J. CATHODE CYLINDER HAVING A HEATER MEMBER SUPPORTED BY A PLURALITY OF FLEXIBLE METAL BANDS Filed Feb. 16, 1965 4 \[f a 1 i I 2 FIG. I 1

INVENTOR. JOHN E RICHTER United States Patent 3,351,801 CATHODE CYLINDER HAVING A HEATER MEM- BER SUPPORTED BY A PLURALITY 0F FLEXI- BLE METAL BANDS John F. Richter, San Mateo, Calii'., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Feb. 16, 1965, Ser. No. 433,240 Claims. (Cl. 313--270) This invention relates to electrontube cathode structure and more particularly to such electron type cathode structure capable of being rapidly heated to emission temperature.

Many power tube applications require high demand outputs at widely spaced intervals. Overall efiiciency of such devices is degraded by the constant power dissipation from the heater during the inter-pulse or standby periods.

Consequently much power can be conserved if a tubes cathode can be brought to operating temperature only at the times when the tube is required to produce an output, i.e., during standby periods the tubes cathode is not heated. The chief problem in such an arrangement is in providing a cathode which heats very rapidly and structural support for the cathode which can endure the rapid thermal expansion during heating periods.

An object of the present invention is to provide an electron tube having a high average efficiency.

Another object of the present invention is to provide an electron tube having a cathode which can be rapidly heated.

A further object of the present invention is to provide electron tube cathode structure capable of being rapidly brought to emission temperature and capable of enduring rapid thermal expansion.

The present invention attempts to solve the above problems and objects by providing a cathode element having very low thermal mass and unique support structure for the cathode which can endure repeated thermal expansion and contraction.

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 a cross-section View of a cathode structure of the present invention;

FIG. 2 is a pictorial view of the cathode support structure of the present invention.

In FIG. 1 an electron tube 1 utilizing a cathode 2 is shown. Other elements such as the grid and plate have been eliminated to more clearly show the cathode structure. Cylindrical cathode 2 is provided with a circular end plate 3 having a small hole in its center. Heater support rod 4 passes through the small hole and is bonded to the plate 3 at point C. Hence one end of support rod 4 is rigidly attached to the cylindrical cathode. Heater coils 5 and 6 are brazed or otherwise bonded to rod 4 at point D. Terminal lead wires 7 and 8 are bonded to coils 5 and 6 at points C and D respectively. Coil 5 is the primary heater coil used during normal operation of the tube whereas coil 6 is an auxiliary heater for heating the cathode by radiation during conversion of the alkaline earth carbonates during evacuation of the tube. Leads 7 and 8 are, of course, connected to the appropriate terminals on a base 14. A plurality of pins 10 are fastened to sleeves 12 on bottom 11 of the cylindrical cathode and provide the lower support for the cathode and the electrical connection thereto.

The bottom of rod 4 is flexibly attached to base 14 to allow for movement of the rod during heating and cooling. The flexible support structure is best seen in 3,351,801 Patented Nov. 7, 1967 FIG. 2. The bottom of rod 4 is bonded to washer 15 at its center opening 16. Support straps 13 are then radially arranged in asymmetrical mannerwabout the washer 15 and bonded thereto. Each strap is then twisted and attached to vertical support pins 9 which are fixed to the base 14 as shown. In the particular embodiment three straps were used and provided good dimensional stability and freedom 'for vertical movement.

When the cathode is heated it consequently expands. Since rod 4 is rigidly attachedto the cathode at point A it is subjected to some movement during heating. The instant support structure permits rod 4 to move along its vertical axis and thus follow any expansion or contraction of the cathode and yet prohibits any sideways movement of the rod.

In a particular embodiment tested an oxide cathode was used in conjunction with a thoriated tungsten heater coil. Support straps 13 were of nickel to prevent workhardening of the material at the normal operating temperatures. As an example of the expansion movement encountered in such an arrangement, the heater support assembly moved upward a distance of about .015 inch on each heating pulse.

Heating of the cathode is achieved by placing a high potential between bombarder heating coil 5 and the cathode 2. The plate power supply, by suitable switching arrangements, may be used as the high potential source. In the test case emission temperature was reached in a period of from 80 to milliseconds. Once the cathode is heated the plate supply may be switched over to its normal function to accommodate an output demand pulse. Output demand pulses of 40 milliseconds duration are possible before the cathode cools to below its emission temperature.

The instant invention, therefore, provides an electron tube cathode assembly which eliminates the normal waste of heater power.

While the invention has been described by means of a specific example and in a specific embodiment, it is not limited thereto for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A cathode structure for use in an electron power tube capable of being rapidly heated to emission temperature comprising;

a hollow conductive cylindrical cathode element having two open ends;

a conductive end plate covering one end of said cylindrical cathode and afiixed thereto;

a heater support rod extending through said cylindrical cathode along its central longitudinal axis and rigidly attached at one of its ends to said end plate;

heater coils disposed about said heater support rod and supported thereby;

a plurality of flexible bands radially and symmetrically disposed about the other end of said heater support rod;

one end of each of said bands being rigidly attached to said other end of said heater support rod;

an insulated base member;

first means attached to said base for rigidly supporting the other end of said cylindrical cathode in a position above said base; and second means attached to said base for rigidly supporting the other ends of each of said flexible bands in a position above said base.

2. The structure of claim 1 wherein said flexible bands are flat nickel strips.

3. The structure of claim 1 wherein said plurality of bands are three in number.

4. A cathode structure for use in an electron power tube capable of being rapidly heated to emission temperature comprising;

a hollow conductive cylindrical cathode of low thermal mass and having two open ends;

a conductive end plate covering one end of said cylindrical cathode and aflixed thereto;

a heater support rod extending through said cylindrical cathode along its central longitudinal axis and rigidly attached at one of its ends to said end plate;

heater coil means connected to said heater support rod at a point adjacent said end plate and disposed about the length of said heater support rod;

three flexible metal bands radially extending from the other end of said heater support rod at right angles thereto and spaced from each other at 120 intervals;

the ends of nearest said heater support rod of each of said flexible bands being rigidly attached to said heater support rod;

an insulated base member;

a plurality of first support pins perpendicularly mounted on said base and extending upwardly therefrom;

the upper ends of said first pins being rigidly attached to the remaining open end of said cylindrical cathode and adapted to support said cathode in a position over said base and spaced therefrom; and

three second support pins mounted on said base extending upwardly therefrom;

said second pins being disposed on said base so that their upper ends mate with the other ends of respective ones of said flexible bands;

each of said other ends of said flexible bands being rigidly attached to said upper ends of said second support pins.

5. The structure of claim 4 wherein said flexible bands are flat nickel strips.

References Cited UNITED STATES PATENTS 2,082,120 6/1937 ROnci 313-278 2,717,975 9/1955 Whitol 313331 3,038,098 6/1962 Neill 3l3250 FOREIGN PATENTS 1,286,724 1/1962 France.

JOHN W. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner.

Claims (1)

1. A CATHODE STRUCTURE FOR USE IN AN ELECTRON POWER TUBE CAPABLE OF BEING RAPIDLY HEATED TO EMISSION TEMPERATURE COMPRISING; A HOLLOW CONDUCTIVE CYLINDRICAL CATHODE ELEMENT HAVING TWO OPEN ENDS; A CONDUCTIVE END PLATE COVERING ONE END OF SAID CY LINDRICAL CATHODE AND AFFIXED THERETO; A HEATER SUPPORT ROD EXTENDING THROUGH SAID CYLINDRICAL CATHODE ALONG ITS CENTRAL LONGITUDINAL AXIS AND RIGIDLY ATTACHED AT ONE OF ITS END TO SAID END PLATE; HEATER COILS DISPOSED ABOUT SAID HEATER SUPPORT ROD AND SUPPORTED THEREBY; A PLURALITY OF FLEXIBLE BANDS RADIALLY AND SYMMETRICALLY DISPOSED ABOUT THE OTHER END OF SAID HEATER SUPPORT ROD; ONE END OF EACH OF SAID BAND BEING RIGIDLY ATTACHED TO SAID OTHER END OF SAID HEATER SUPPORT ROD; AN INSULATED BASE MEMBER; FIRST MEANS ATTACHED TO SAID BASE FOR RIGIDLY SUPPORTING THE OTHER END OF SAID CYLINDRICAL CATHODE IN A POSITION ABOVE SAID BASE; AND SECOND MEANS ATTACHED TO SAID BASE FOR RIGIDLY SUPPORTING THE OTHER ENDS OF EACH OF SAID FLEXIBLE BANDS IN A POSITION ABOVE SAID BASE.

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