US2441349A

US2441349A - Electrode mounting structure for electron tubes

Info

Publication number: US2441349A
Application number: US619810A
Authority: US
Inventors: William W Eitel; Jack A Mccullough
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1945-10-02
Filing date: 1945-10-02
Publication date: 1948-05-11
Anticipated expiration: 1965-05-11

Description

May 11, 1948. w. w. EITEL ETAL 2,441,349

ELECTRODE MOUNTING STRUCTURE FOR ELECTRON TUBES Filed Oct. 2, 1945 2 Sheets-Sheet 1 \1 X K 9 w a /e 48 54 M l 6 .ILL J INVENTOR.

Mil/131m bl- Ene/ Jqs/i Av McCullough Mai,

\ ATTORNEY y 1948' w. w. EITEL arm. 2,441,349

ELECTRODE MOUNTING STRUCTURE FOR ELECTRON TUBES Filed Oct. 2, 1945 2 Sheets-Sheet 2 54 \\I it 7 24 fig .2

ATTORNEY Patented May 11, 1948 ELECTRODE MOUNTING STRUCTURE FOR ELECTRON TUBES William w. Eitel, Woodslde, .44 Jack a. McCullongh. Mlllbrae, Calif., minors to Eltel-Mc- Cullough, Inc, San Bruno, Calif a corporation of California Application October 2, 1945, Serial No. 619,810

1 18 Claims.

Our invention relates to electron tubes, and more particularly to power tubes of the vacuum typ It is among the objects of our invention to provide a tube structure capable of large power outputs at high frequencies, as well as at the lower frequencies.

Another object is to provide a tube of the character described having an improved arrangement of electrodes and electrode terminals, particularly adapted for making the tube operable in the higher frequency ranges, say above 100 megacycles.

A further object is to provide an improved filamentary type of cathode.

The invention h w: a other objects and features of advantage. some or which, with the foregoing, will be set forth in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure l is a vertical sectional view of a tube embodying the improvements of our invention;

and A Figure 2 is a similar view of the cathode-grid assembly, showing the cathode in elevation.

In terms of broad inclusion, our tube comprises an envelope having an anode, a cathode stem and a grid terminal member. The cathode stem preferably comprises a pair of coaxial stem members, and the grid terminal member is preferably a ring interposed in the envelope wall between the outer stem member and the anode, the stem members and terminal ring and anode being arranged about a common axis. A grid connected to the terminal ring is provided in the envelope. The cathode preferably comprises longitudinal filament wires having an improved supporting and tensioning means. Inour tube the cathode and grid structures and their mounting means are particularly designed to maintain close spacings between electrodes of relatively large diameter. While a filamentary type of cathode is preferred it is understood that any of the conventional directly or indirectly heated types of cathodes may be used.

In greater detail, and referring to the drawings, our improvements are illustrated in a triode type of tube having a full external anode, it being understood that the improvements may be incorporated in tubes having more than one grid and in tube types having full internal anodes as well as anodes which are partially internal and partially external. The tube illustrated comprises an envelope having an external anode 2, a'cathode stem 3 and a grid terminal member 4 joined by vitreous or glass sections 6 and I.

Anode 2 is preferably a tubular cup having a cylindrical wall 8 and a top 9, formed of suitable metal such as copper or nickel. A metal tubulation Ii on the anode provides a passage for evacuating the envelope, after which the tubulation is pinched off at tip II. The anode is connected to envelope section 8 by a flange I3 of metal having expansion characteristics matching that of the glass. This flange is secured to the lower end of the anode at braze i4 and is joined toglass sectioni atseal it. 4

Grid terminal 4 is preferably a ring-shaped member Joined to section b at seal l1 and to section 1 at seal it. This terminal has a cylindrical contact surface I! for engagement with resilient fingers of a socket. Since our tube is adapted for plugging into a socket structure, the terminal ring 4 is preferably formed with a step or offset 2| adjacent seal it to locate the latter inwardly of surface It so that enough clearance is provided between the socket and the seal to prevent breaking the glass. A second offset 22 is also provided adjacent seal II to form a ledge which functions as a stop for the socket to prevent breakage of seal ii.

Cathode stem 3 preferably comprises a pair of

coaxial stem members

23 and 24. Outer tubular member 23 is of a metal similar to that of flange l3, and is Joined to glass section I at seal 26. This stem member is provided with an offset 21 to form a stop for the socket. Inner stem member 24 is preferably a solid piece, and is preferably made of a metal, such as copper. having good thermal conducting properties to aid in removing heat from the cathode structure. The stem members are joined by a pair of

sleeves

28 and 29 also of a metal-similar to that of flange l3 sealed together by vitreous ring II, the upper sleeve 28 being brazed to member 24 and the lower sleeve 29 being connected to member 23 at braze 32.

The various glass and metal parts hereinbefore described all form part of the envelope structure and coact to provide a vacuum tight closure. It will be noted that anode 2, grid terminal member 4 and

cathode stem members

23 and 24 are all coaxially disposed about a common axis, which preserves the symmetry of the electrode terminals with respect to circuit components such as coaxial lines. The tube 3 may thus be interposed between and plugged directly into the ends of coaxial lines 01 a high frequency unit.

The cathode structure in our tube preferably comprises a pair of fixed filament supports 33 and 34 concentrically arranged in coaxial alignment with the stem. These metallic supports are of annular shape, the outer support 33 being mounted on and electrically connected to stem member 23 by metal sleeve 35 and the inner support 34 being mounted on and electrically connected to stem member 24 by metal sleeve 35.

Supports

33 and 34 are formed with

peripheral tabs

31 and 33 alternately arranged in a circle which defines the circumference of the cathode.

Longitudinal filament wires 39 of thoriated tungsten are spaced about the cathode circumierence with the lower ends secured to

tabs

31 and 38, so that one wire is connected to one of the supports and an adjacent wire is connected to the other support. A pair of knock-out loops are preirably formed on each tab, through which the wire passes, the lower end of the wire being welded adjacent the bottom loop. In our preferred construction the wires are hairpin filaments each having one end connected to a tab 31 and another end connected to a tab 38 so that pairs of the filament wires are connected in series across the stem members through which filament current is applied.

A center rod or standard 4| projects from and is anchored to inner stem member 24. This standard carries at its upper end a common filament support 42 mounted for axial movement and preferably in the form oi! an apertured disk having radially extending arms 43 with hook ends engaging the bights of the filaments. This support is of a resilient refractory metal, such as molybdenum, and is suillciently thin to give ample flexibility to arms 43. Support 42 is insulated from standard 4| by a washer 45, say of beryllium oxide, moveable on the standard and recessed to engage the aperture of the support.

The filaments are tensioned by a pusher sleeve 44 surrounding standard 4i and interposed between washer 45 and a spring 48, which spring is centered by end caps 41. It will be observed that spring 46 is disposed below the cathode and remote from the intense heat zone about the filaments. Also, heat is conducted away from center rod 4| and from the region of the spring by copper stem member 24, so that the resilience of the spring is not impaired by heat during operation. Removal of heat is enhanced by the center rod being embedded directly in member 24, and by the fact that spring 46 seats on the top of the copper member.

With this improved tensioning device the spring 46 functions as main tensioning element common to all the filaments. Support 42 distributes the force to the several hairpin filaments through the radial arms 43. Since these arms are capable of independent flexing, they also function as equalizing arms, so that the individual hairpins are maintained under substantially uniform tension. Thus, if one hairpin should be slightly longer than another, this discrepancy in length will be compensated for by relative fiexing between arms 43. Bowing between individual wires is therefore avoided, and a straight-wire filament structure is assured.

Control grid 50 in our tube preferably comprises a cage-like structure of suitable wire with a base ring 48 secured to a bracket 49. This bracket is of a metal such as nickel, a d is pret- 4 erably of conical shape .tor rigidity. The grid is supported on and electrically connected to terminal ring 4 by plurality oi studs 5|, only one oi which is shown in Figures 1 and 2. A suitable number, say three, of these studs are spaced about the base of cone 49, the latter being indented to provide a recess 52 adjacent each stud. Studs 5| are threaded into a flanged ring 53 which is secured, as by brazing, to the inner face of terminal member 4. A nut 54 looks the stud in place. Each stud projects through an aperture in bracket 49, and the parts are held together in final position by nuts 58.

This arrangement provides means for adjustably positioning the grid when the electrodes are assembled in the envelope, and facilitates alignment of the electrodes. The final seal is preterably made adjacent the anode, so that the cathode and grid structures are accessible for mounting purposes on the lower portions of the envelope. Figure 2 shows the cathode-grid assembly prior to sealing on the anode.

We preferably air cool the anode, and for this purpose provide a suitable cooler 51 having fins 58, the cooler being attached to the anode by solder 59. It is understood, of course, that the anode may be provided with a jacket for water cooling if such is desired.

We claim:

1. An electron tube comprising an envelope having an anode at one end and a pair oi coaxial stem members at the other end, said stem members projecting into the envelope and terminating in a pair of freely spaced annular cathode supports, a terminal ring coaxial with said annular cathode supports interposed in the envelope wall between the outer stem member and the anode, a cathode in the envelope comprising longitudinal filament wires connected to the stem members, and a grid in the envelope connected to said terminal ring.

2. An electron tube comprising an envelope having an anode at one end and a pair of coaxial stem members at the other end, said stem members projecting into the envelope and terminating in a pair of freely spaced annular cathode supports, a terminal ring coaxial with said annular cathode supports interposed in the envelope wall between the outer stem member and the anode, a cathode in the envelope comprising longitudinal filament wires mounted with adlacent wires at one end of the cathode connected to difierent supports oi! said stem members, means engaging the wires at the other end 0! the cathode for tensioning said wires, and a grid in the envelope connected to said terminal ring.

3. An electron tube comprising an envelope having an anode at one end and a pair of coaxial stem members at the other end, said stem members projecting into the envelope and terminating in a pair of freely spaced annular cathode supports, a terminal ring coaxial with said annular cathode supports interposed in the envelope wall between the outer stem member and the anode, a cathode in the envelope comprising longitudinal filament wires'mounted with adjacent wires at one end of the cathode connected to difierent supports of said stem members, means mounted on the inner stem member and having a part engaging the wires at the other end of the cathode for tensioning said wires, an insulator interposed in said tensioning means and located between the inner stem member and said wire engaging part. and a rid in the envelope connected to said terminal ring.

said axis, and a grid in the envelope connected to said terminal ring.

5. 'An electron tube comprising an envelope having an anode at one end and a pair of coaxial stem members a the other end, a terminal ring interposed in the envelope wall between the outer stem member and the anode, said stem members and terminal ring and anode being disposed about a common axis, a cathode in the envelope comprising longitudinal wires connected to the stem members and mounted in a circle concentric with said axis, a grid in the envelope concentric with said axis, and means adjustably mounting the grid on said terminal ring.

6. An electron tube comprising an envelope having a pair of coaxial stem members, a standard projecting from the inner stem member, a pair of filament supports on the stem members having tabs alternately disposed in a circle about the axis of said stem members, a plurality oi. hairpin filaments each having one end connected to a tab on one of the supports and another end connected to a tab on the other support, and a filament support on the standard engaging the bights ofsaid filaments.

'7. An electron tube comprising an envelope having a pair of coaxial stem members, a standard projecting from the inner stem member independently of the outer member, a pair of filament supports on the stem members having tabs alternately disposed in a circle, a plurality of hairpin filaments each having one end connected to a tab on one of the supports and another end connected to a tab on the other support, and a filament support on the standard engaging the bights of said filaments.

8. An electron tube comprising an envelope having a pair of coaxial stem members, a standard projecting from the inner stem member independently of the outer member, a pair of filament supports on the stem members having tabs alternately disposed in a circle, a plurality of hairpin filaments each having one end connected to a tab on one of the supports and another end connected to a tab on the other support, a filament support engaging the bights of said filaments, an insulator engaging the last mentioned support, and a spring pressed pusher on the standard bearing against said insulator.

9. An electron tube comprising an envelope having an anode at one end and a terminal ring adjacent the other end, a grid in the envelope connected to said terminal ring, a pair of independently mounted fixed filament supports having tabs alternately disposed in a circle coaxial with the grid, a plurality of longitudinal filament wires connected to said tabs, and means tensioning said filament wires.

10. An electron tube comprising an envelope having an annular terminal member, a grid in the envelope coaxial with and connected to said member, a pair of independently mounted fixed concentric filament supports adjacent an end of the grid and having peripheral portions mounted in a circle coaxial with said member, and longi- 6 tudin'al filament wires connected to said peripheral portions.

11. An electron tube comprising an envelope having an annular terminal member, a grid in the envelope coaxial with and connected to said member, a pair of independently mounted fixed concentric filament supports adjacent an end oi the grid and having tabs alternately mounted in a circle coaxial with said member, a plurality of hairpin filaments each having one end connected to a tab on one of the supports and another and connected to a tab on the other support.

12. An electron tube comprising an envelope having an annular terminal member, a grid in the envelope coaxial with and connected to said member, a pair of independently mounted fixed concentric filament supports adjacent an end of the grid and having tabs alternately mounted in a circle coaxial with said member, a plurality of hairpin filaments each having one end connected to a tab on one of the supports and another end connected to a tab on the other support, a standard coaxial with said supports, and a filament support on the standard engaging the bights of said filaments.

13. An electron tube adapted for insertion into a socket, comprising an envelope having a terminal ring sealed between vitreous sections, said ring having an intumed lip and downtumed flange integral with the ring adjacent one seal to provide clearance for the socket and having an outturned lip and upturned flange integral with the ring adjacent the other seal to provide a stop for the socket.

14. An electron tube comprising an envelope having an anode at one end and a pair of co axial stem members at the other end, the outer stem member being tubular and disposed about the inner stem member, a sleeve between the stem members and having an edge registering with that of the tubular stem member, a fused metallic bond uniting said edges, a terminal ring interposed in the envelope wall between the outer stem member and the anode, a cathode in the envelop connected to the stem members, and a grid in the envelope connected to said terminal ring.

15. An electron tube comprising an envelope having an anode at one end and a pair of coaxial stem members at the other end, the outer stem member being tubular and disposed about the inner stem member, a pair of sleeves between the stem members and connected thereto, a sealing ring of vitreous material joining the sleeves, a terminal ring interposed in the envelope wall between the outer stem member and the anode, a cathode in the envelope connected to the stem members, and a grid in the envelope connected to said terminal ring.

16. An electron tube comprising an external anode, a metallic terminal ring below the anode, a vitreous wall section between the terminal ring and anode and sealed to the upper edge of said ring, a pair of coaxial metallic stem members opposite the anode, the outer stem member being tubular and disposed about the inner stem member, a vitreous wall section between the terminal ring and outer stem member and sealed to the lower edge of said ring, means including a vitreous sealing ring connecting the stem members, a cathode comprising a lurality of parallel filament wires, the lower end of one wire being connected to one stem member and the lower end of an adjacent wire being connected to another stem member, a standard projecting from the 7 inner stem member independently oi the outer member ior supporting the upper portions 0! the filament wires. and a grid connected to the terminal 11118.

17. An electron tube comprising an external anode, a metallic terminal ring below the anode, a vitreous wall section between the terminal ring and anode and sealed to the upper edge of said ring, a pair of coaxial metallic stern members opposite the anode, the outer stem member being tubular and disposed about the inner stem member, a vitreous wall section between the terminal ring and outer stem member and sealed to the lower edge oi said ring, means including a vitreous sealing ring connecting the stem members, a cathode comprising a plurality of hairpin filaments each having a lower end connected to one 01 the stem members and another lower end connected to the other stem member, a standardprojecting from the inner stem member independently oi the outer member for supporting the upper bight portions of the filaments, and a grid connected to the terminal ring.

18. An electron tube comprising an external anode, a metallic sealing flange on the anode, a metallic terminal ring below said flange, a vitreous wall section sealed at one end to the flange and at the other end to the upper edge of said ring, a pair of coaxial metallic stem members opposite the anode, the outer stem member being tubular and disposed about the inner stem memher, a vitreous wall section sealed at one end to the outer stem member and at the other end to the lower edge of said ring, means including a vitreous sealing ring connecting the stem memhere, a cathode comprising a plurality of hairpin filaments each having a lower end connected to one of the stem members and another lower end connected to the other stem member, a stand ard projecting from the inner stem member independently oi the outer member ior supporting the upper bllhts oi the filaments, and a grid connected to the terminal ring.

WILLIAM W. EITEL. JACK A. MCCULIOUGH.

REFERENCES CITED The following references are of record in the file or this patent:

UNITED STATES PATENTS Number Name Date 2,288,380 Wing, Jr June 30, 1942 2,314,037 Eitel et al. Mar. 16, 1943 2,385,435 Werner et a1 Sept. 25, 1945 2,399,757 Murdock May 7, 1948 2,411,046 Liimatainen Nov. 12, 1948