US2814750A

US2814750A - Ceramic electron tube

Info

Publication number: US2814750A
Application number: US438916A
Authority: US
Inventors: James P Polese
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1954-06-24
Filing date: 1954-06-24
Publication date: 1957-11-26
Anticipated expiration: 1974-11-26

Description

Nov. 26, 1957 J. P. POLESE 2,814,759

CERAMIC ELECTRON TUBE Filed June 24, 1954 3 Sheets-Sheet 1 INVENTOR.

dames R Po/ese A TTOENEY 1957 J. P. POLESE 2,814,750

CERAMIC ELECTRON TUBE Filed June 24, 1954 3 Sheets-Sheet 2 ml 1D ,7 58

/3 3/ l4 1 7 46 I 4 PE 2' I /8 I j 8 f 52 i 32 24 38 8 f k/z INVENTOR.

Jams R Po/ese BY M547 TTOE/VEY Nov. 26, 1957 J. P. POLESE CERAMIC ELECTRON TUBE 3 Sheets-Sheet 5 Filed June 24, 1954 IN V EN TOR. dame s P. P0 less TOQ/VE) United States Patent 2,s14,7so

CERAMIC ELECTRON TUBE James P. Polese, Menlo Park, Calif., assignor to Eitel- McCullough, Inc., San Bruno, Calif., a corporation of California Application June 24, 1954, Serial No. 438,916

Claims. (Cl. 313-247) My invention relates to electron tubes employing ceramic in the envelope structure, and more particularly to an improved tetrode in the power tube category.

It is among the objects of my invention to provide a tetrode of rugged construction having an improved ceramic envelope and electrode supporting structure.

Another object is to provide an envelope and electrode structure which is easy to fabricate and assemble.

A further object is to provide an envelope side wall construction comprising stacked ceramic cylinders and an improved metal strut structure at the lower end of the envelope.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention, as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawings:

Figure 1 is a side elevational view of a tetrode embodying my improvements; and

Figure 2 is a vertical sectional view of the same.

Figure 3 is a similar vertical sectional view showing the ceramic and associated portions of the envelope prior to mounting the electrodes.

.In greater detail, the ceramic tetrode of myiinvention has coaxial electrodes including a filamentary cathode 2, control grid 3, screen grid 4, and external anode 6, the latter forming the upper portion of the evacuated envelope. The envelope is of generally cylindrical shape, having a body portion with a side wall made up of three vertically stacked

ceramic cylinders

7, 8, and 9 joined along abutting ends. Upper and lower ceramic-to-

ceramic joints

11 and 12 are thus provided in the side wall.

Such ceramic cylinders preferably have different diameters decreasing in size toward the lower end of the envelope so that the cylinders are offset atthe jointsas shown in Figure 2. The internaldiameter of an upper cylinder in the stack is thus larger than that of an adjacent lower cylinder, so that the upper edge of the lower cylinder provides an interior horizontal ledge adjacent .the joint.

The ceramic used in the wall cylinders is of a highly refractory kind, preferably alumina. In order to bond the ceramic to another ceramic section or'to adjacent metal parts, the ceramic-cylinders are ffirst metalized at the ends in a suitable manner. Any of the known metalizing techniques may be used, such as the metal powder sinteringprocess or the like. For example, the surface 'ofthe ceramic may be coated with -a finely dividedmetalssuch as molybdenum, or a mixture of molybdenum and iron or manganese, and then fired in hydrogento a temperature of about 1300 C. to sinter the metal powder to the ceramic.

Such metalized surfacemay thenbe brazed to another metalized ceramic part or to ametal member with a suitable high melting point brazing'alloy "such-as copper-silver, copper-golior the like. The brazesare readily made by 2,814,750 Patented Nov. 26, 19 5.7

fitting the metalized parts together with rings or brazing wire adjacent the joints, and then elevating the temperature of the Whole up to the melting point of the brazing material in a suitable furnace. Another metalizing technique is to coat the ceramic with titanium or zirconium hydride powders and fire in vacuum to about 1200 C.

The electrodes within the envelope have coaxial metal supports including inner and outer filament supports 13 and 14, control grid support 16 and screen grid support 17, the grid supports having flared base portions 18 and 19. Center filament support 13 also includes a solid metal stud portion 21 at its lower end, which stud provides one of the filament terminals. A fourth ceramic cylinder .22 is arranged at the lower end of the envelope inside and concentric with lower cylinder 9 of the side wall stack.

A conical metal wall strut 23 is connected at the top to center electrode support 21 and at the bottom to the lower end of inner ceramic cylinder 22, the upper end of the wall strut being brazed at 24 to stud 21 and the bottom having a horizontal flange portion 26 brazed to the metalized end of cylinder 22. In order to center the electrode support within the envelope, the wall strut preferably has a cylindrical portion 27 fitted into cylinder 22 and having a diameter substantially equal to the internal diameter of the ceramic cylinder.

A second conical metal wall strut 28 paralleling the first strut is connected at the top to outer filament support 14 and at the bottom to the lower end of the outer ceramic cylinder 9. Like the first described wall structure, second wall strut 28 has a flange portion 29 brazed to the metalized lower end of ceramic cylinder 9 and also has a cylindrical portion 31 for centering the parts within the envelope. Wall strut 28 has an intermediate flattened portion 32 brazed to the metalized upper end of inner ceramic cylinder 22 so that the latter provides a compression member between the wall struts. Cylindrical portion 31 of the wall strut which is exposed externally of the envelope also provides the second filament terminal. This wall structure at the lower end of the envelope is extremely rigid, provides centering means for the electrode supports, and is self-jigging so that parts are maintained in coaxial alignment during assembly.

Filamentary cathode 2 is preferably made up of hairpin wire filaments of thoriated tungsten fastened at the bottom to alternate tabs on the upper ends of the filament supports. The upper ends of the hairpins are suspended by hooks on a disk 33 which slides on a center rod 34. A pusher plate 36 separated from disk 33 by insulating buttons 37 is pressed upwardly by a spring 38 through a sleeve 39 encircling the center rod, thus keeping the filaments under tension.

Control grid 3, preferably of the wire cage type, is mounted by screws 41 on a circular grid mount 42 of conical formation. This mount has horizontal lips 43 engaging the upper surface of the ledge at joint 12 and vertical lips 44 engaging the inner surface of ceramic cylinder 9. The diameter of the mount at lips 44 is substantially equal to the internal diameter of cylinder 9 so as to center the mount in the envelope. Likewise, the diameter of the mount at lips 43 is substantially equal to the internal diameter of upper cylinder 8 so as to coaxially align the latter with lower'cylinder 9 and with the electrode mount 42.

In a similar manner screen grid 4 is mounted by screws 46 on a circular grid mount 47 having

lips

48 and 49 for jigging the parts at upper joint 11. Both grid mounts are brazed to the metalized ceramic cylinders at the same time the latter are brazed together. Such structure is extremely easy to assemble, using simple parts, and insures coaxial alignment of all the elements. The resulting structure is very strong and rugged.

Control and

screen grid terminals

51 and 52 are provided on the ceramic envelope and are connected to the respective mounts through metallic bonds at joints l2 and 11. These grid terminals are preferably formed in a simple manner bymetalizing the desired areas on the ceramic cylinders, which metalized areas may be electroplated with nickel or copper if a smoother terminal surface is desired.

Figure 3 shows the ceramic body portion of the envelope prior to mounting the electrodes. All of the parts in this view are assembled and brazed together in one operation in a brazing furnace. This is possible because all the parts are self-aligning and self-supporting and can be assembled together with the necessary brazing rings for delivery to the brazing furnace.

Anode 6, which forms the upper portions of the envelope, is cup-shaped, preferably of copper, and carries a metal exhaust tubulation 53 as well as cooling fins 54 which are preferably brazed directly to the anode so that the cooler construction forms a structurally integral part of the anode. A retaining cylinder 56 preferably houses the fins.

The anode support comprises a downwardly extending metal flange 57 brazed to a base anode ring 58 and encircling the upper ceramic cylinder 7. A metal sealing ring 59 is fitted into anode flange 57 and has an inturned flange portion overlapping the metalized upper end of cylinder 7 and brazed thereto. As a final assembly step the registering edges of the metal flanges are welded together at 61. When so assembled the anode base ring 58 preferably abuts the envelope structure as shown in Figure 2 to take the thrust when the envelope is evacuated and thus remove the stress from the sealing flanges.

The term electrode is used in its broad sense herein, and includes any tube element connected to a voltage source or having a potential differing from that of another element.

I claim:

1. An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, inner and outer ceramic cylinders concentric with said terminal, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner ceramic cylinder, and a second conical metal wall strut connected at its top to a second of the electrode supports and at its bottom to the lower end of the outer ceramic cylinder, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder the latter cylinder providing a compression member between the struts.

2., An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders being metallically bonded together at metalized ends, a mount for one of said electrode supports connected to the side wall at a joint between the ceramic cylinders, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said lower ceramic cylinders, and a second conical metal wall strut connected at its top to another of the electrode supports and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder, the latter providing a compression member between the struts.

3. An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders being metallically bonded together at metalized ends, a mount for one of said electrode supports connected to the side wall at a. joint between the ceramic cylinders, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said lower ceramic cylinders, a second conical metal wall strut connected at its top to another of the electrode supports and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder, the latter providing a compression member between the struts, said electrode mount being metallically bonded to the metalized ceramic at said joint, and an electrode terminal on the envelope connected to the mount through the metallic bond of said joint.

4. An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, three vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders having metalized ends metallically bonded together at upper and lower side wall joints, a mount for one of said electrode supports connected to the side wall at the upper joint, a mount for another of said electrode supports connected to the side wall at the lower joint, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said lower ceramic cylinders, and a second conical metal wall strut connected at its top to another of the electrode supports and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strutbeing connected to the upper end of the inner ceramic cylinder the latter providing a compression member between the struts.

5. An electron tube comprising an envelope, electrodes in the envelope including a filament and control grid and screen grid, coaxial electrode supports including a center support providing a filament terminal at the lower end of the envelope, three vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders having metalized ends metallically bonded together at upper and lower side wall joints, a mount for the screen grid support connected to the side wall at the upper joint, a mount for the control grid support connected to the side wall at the lower joint, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said, lower ceramic cylinders, and a second conical metal wall strut connected at its top to a second filament support and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder, the latter providing a compression member between the struts, said second wall strut providing a second filament terminal coaxial with said first filament terminal.

6. An electron tube comprising an envelope, electrodes in the envelope including a filament and control grid and screen grid, coaxial electrode supports including a center support providing a filament terminal at the lower end of the envelope, three vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders having metalized ends metallically bonded together at upper and lower side wall joints, a mount for the screen grid support connected to the side wall at the upper joint, a mount for the control grid support connected to the side wall at the lower joint, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said lower ceramic cylinders, a second conical metal wall strut connected at the top to a second filament support and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder, the latter providing a compression member between the struts, said second Wall strut providing a second filament terminal coaxial with said first filament terminal, a control grid terminal on the envelope connected to the control grid mount through the metallic bond of the lower joint, and a screen grid terminal on the envelope connected to the screen grid mount through the metallic bond of the upper joint.

7. An electron tube comprising an envelope, electrodes in the envelope including a filament and control grid and screen grid, coaxial electrode supports including a center support providing a filament terminal at the lower end of the envelope, three vertically stacked ceramic cylinders forming the side wall of the envelope, said cylinders having metalized ends metallically bonded together at upper and lower side Wall joints, a mount for the screen grid support connected to the side wall at the upper joint, a mount for the control grid support connected to the side wall at the lower point, another ceramic cylinder concentric within the lower cylinder of the side wall stack, a conical metal wall strut connected at its top to the center terminal and at its bottom to the lower end of the inner of said lower ceramic cylinders, a second conical metal wall strut connected at its top to a second filament support and at its bottom to the lower end of the outer of said lower ceramic cylinders, the intermediate portions of the latter strut being connected to the upper end of the inner ceramic cylinder, the latter providing a compression member between the struts, said second wall strut providing a second filament terminal coaxial with said first filament terminal, a control grid terminal on the envelope connected to the control grid mount through the metallic bond of the lower joint, a screen grid terminal on the envelope connected to the screen grid mount through the metallic bond of the upper joint, and an external metal anode forming the upper portion of the envelope and supported on the uppermost ceramic cylinder of said stack.

8. An electron tube comprising an envelope, a. plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, a pair of ceramic cylinders of different diameter concentric with said terminal, an annular metal wall strut connected to and extending between the center terminal and the lower end of the ceramic cylinder of less diameter, and a second annular metal wall strut connected to and extending between a second of the electrode supports and the lower end of the ceramic cylinder of greater diameter, the intermediate portions of the latter strut being connected to the upper end of the ceramic cylinder of less diameter, so that the latter cylinder extends between the struts.

9. An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, a pair of ceramic cylinders of different diameter concentric with said terminal, an annular metal wall strut connected to and extending between the center terminal and the lower end of the ceramic cylinder of less diameter, and a second annular metal wall strut connected to and extending between a second of the electrode supports and the lower end of the ceramic cylinder of greater diameter, the intermediate portions of the latter strut being connected to the upper end of the ceramic cylinder of less diameter, so that the latter cylinder extends between the struts, said wall struts being formed to provide downwardly directed cylindrical portions fitting within the lower ends of the respective ceramic cylinders,

10. An electron tube comprising an envelope, a plurality of coaxial electrode supports including a center support providing a terminal at the lower end of the envelope, a pair of telescoped ceramic cylinders of different diameter concentric with said terminal, the outer diameter of one of said cylinders being less than the inner diameter of the other of said cylinders, an annular metal wall strut connected to and extending between the center terminal and the lower end of the ceramic cylinder of less diameter, and a second annular metal wall strut connected to and extending between a second of the electrode supports and the lower end of the ceramic cylinder of greater diameter, theintermediate portions of the latter strut being connected to the upper end of the ceramic cylinder of less diameter, so that the latter cylinder extends between the struts, said wall struts being metallically bonded to the ceramic cylinders.

References Cited in the file of this patent UNITED STATES PATENTS 2,069,283 Slepian et al. Feb. 2, 1937 2,629,066 Eitel et al Feb. 17, 1953 2,647,218 Sorg et al. July 28, 1953