US2077814A - Electron discharge device - Google Patents

Description

April 20, 1937. c. w. TAYLOR ELECTRON DI SCHARGE DEVICE Filed Jan. 22, 1935 INVENTOR C ha Hes W. Taylor.

BY I

Patented Apr. 20, 1937 PATENT OFFICE 2,077,814 ELECTRON DISCHARGE DEVICE Charles W. Taylor, East Orange, N. J., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application January 22, 1935, Serial No. 2,870

11 Claims.

My invention relates to thermionic discharge devices and more particularly to electrode assemblies and their supporting means within the tube.

The object of my invention is to provide a 5 mount assembly of the unit type of construction which is easily assembled, rugged in construction, and has good electrical characteristics. According to my invention an electrode assembly is so related to a shielding arrangement that a mechanically rugged tube is produced which has particularly desirable electrical characteristics. A better understanding of my invention may be had by reference to the accompanying drawing in Which'Figure 1 is a perspective view of one 5 form of the tube embodying my invention with some of the elements cut away to show the electrode assembly, andFigure 2 is a perspective View showing the outside of the mount.

Referring to Figure 1 a conventional form of 2 bulb is shown at l with contact cap 2, base 3 and the usual reentrant stem 4 the upper end of "which is a press or seal 5 in which the various lead-in wires are embedded. Upon the stem is supported an electrode assembly of the unit mount construction in which a pair of parallel equipotential cathodes 6, a control grid I, a screen grid 8, a suppressor grid 9 and an anode ID are mounted between two insulating bars or spacers II and I2. The spacer bars II and 12, which preferably are of a ceramic material, such as lavite, are secured in fixed spaced relation by side rods which pass thru the spacers and thru sleeves in the sides of anode H3. The grids are of the usual double helical side rod construction with the side rods l3 which extend into small holes in the spacer bars. The anode'is connected by a lead M to the top cap 2, the screen grid 8 by a lead I5 passing thru the side of the stem tube to a contact pin in the base 3, and the other electrodes are connected to the leading-in wires in the press to the other contact pins on the base. As distinguished from the usual prior art construction in which the electrode assembly is mounted directly upon the stern and press, my device is provided with a combination supporting and shielding arrangement in which a tubular shield I6, which surrounds the press and lead-in wires, is supported by the stem thru curved supporting rods H and is conveniently secured to the stem by embedding the inner ends of the rods in the press. This shield is reduced in diameter at the upper end to be slightly smaller than the lower spacer, and has a shoulder or offset portion l8 and upwardly extending flange IS. The lower spacer rests upon the upper edges of flanges 19,

so that the shield supports the electrode assembly. The shielding member it supports the electrode assembly on the stem, thereby relieving the leading-in wires of mechanical strains, and also electrically shielding the leading-in wires of the 5 stem.

On the upper surface of the upper insulating spacer I2 is a disc 2!], preferably of mica, which is clinched under the welded tabs at the upper ends of the plate side rods as shown. The mica disc is 10 cut away atthe center as at 2| as best shown in Figure 2, to provide a central recess which spaces the mica from all of the side rodsprojecting thru the ceramic spacer l2. Over this centralrecess an oblong. concave shield 22 is positioned and is 15 clinched in place by a strap 23 which extends across the mica disc. In order that the electrode assembly may besecurely clamped to the upper edges of the lower shield, the'outer ends of said strap are welded or otherwise secured to the up- 20 per ends of two tie rods 24 and 25, which'pass downwardly thru holes in the mica disc and are welded or otherwise fastened to shield [6. It will be seen that by securing the lower ends of these tie rods to the lower shield all of the elements be- 5 tween the upper shield 22 and lower shield l6 are securely clamped together into a very rigid structure. To resiliently but firmly center the mount structure within the dome of the bulb of the tube,

the mica disc 2!! may be provided with mica spac- 30 ers 26, such as disclosed in U. S. Patent 2,058,790 dated October 27, 1936 and filed by I-Iirmann on November 1 1 1933 and assigned to Radio Corporation of America. By this construction I have provided a unitary assembly of electrodes and 5 'shields which are clamped against longitudinal displacement and which are accurately and firmly centered within the envelope.

Very complete shielding is afforded by this construction as the lower shield l6 protects the leads 40 in the press from high frequency field effects, and

the shielding may, if desired, be virtually extended to the very end of the outside grid 9 by a collar 21 having depending flange 28. Collar 21 is of rectangular form, welded at its ends to side 45 rods of the outer grid, the sides of which are extended to form a flange as shown at 28. It may be noted that since flanges ill of the lower shield are set inwardly from the edge of the spacer, said shield and collar are out of electrical contact. I 50 may also provide at the upper end of grid 9 and supported upon its side rodsv a second shielding collar 29 with its flange so, which extends to the lower side of the mica disc, and is separated from the upper shield only by the thicknessof the mica ,.55

disc. The upper shield 22 effectively protects the upper ends of the grid side rods and of the cathodes from any high frequency field effects from the anode lead. The only exposure, therefore, of the inner electrodes to high frequency field effects from plate I!) is laterally thru the meshes of the screen grid 8. I have found in practice that this shielding arrangement substantially eliminates all back coupling between input and output electrodes even at such high frequencies as 60 megacycles.

For some applications of my tube I prefer to provide an electrical connection from the lower shield support rod ll to a contact pin in the base of the tube, so that any desired potential may be applied to the lower shield 16 and its connected upper shield 22.

According to a further feature of my inven tion the anode I0 is formed of dark surfaced metal such as carbonized nickel while the top and bottom shields are formed of polished material such as nickel or molybdenum. However, some diificulties maybe encountered in the high frequency heat treatment during exhaust unless the structure is somewhat modified. The principal difficulty in manufacture was found to be the uneven heating of the carbonized nickel with respect to the polished nickel, which apparently is due to the-difference in the heat absorption and radiating-properties of the two metals. It was foundin practice thatthe temperature of the dark anode could not be raised to the proper value before the temperature of the shields reached a dangerously high value. To overcome this difficulty and-in accordance with my invention I make the shields smaller in cross section than the -anode and as a result of the reduced cross sectional dimensions of the shields with respect to those of the anode the-reduced shields cut fewer lines of force from the high frequency heating coil placed about the tube than does the anode, thus reducing the heating of the shields.

It has been found that a carbonized electrode when placed adjacentor directly on the spacer barsof the mount assembly, causes the deposit of a considerable amount of conductive particles on the surfaces of the spacers, thus resulting in objectionable leakage paths between electrodes. To overcome thisdiiiiculty inmy device I space the carbonized electrode, which byway of example may be an anode of carbonized nickel, fromthe spacer bar by means of collars 3| on the anode side rods. Itis found that this arrangement substantially eliminates conductive deposits on thespacer bars. Theseinsulating collars may be formed of ceramic material-such for example as aluminum oxide, which has been ,chosen be cause of its freedom from conductive particles.

Collars ;3 l possess the furtheradvantage of subsubstantially reducing high frequency heating losses within the tube. In the old construction where the plate comes in direct contact with the spacer bars or where the plate is secured to the spacer bar by a metal strap passed around the spacer bar, considerable energy was found to be dissipated in the spacer bar between the plate and. the lower potential electrodes in the spacer bar. I have found that this loss in one tube causedthe normal output of 14 watts to drop to 3 watts.

To further insure against conductive deposits on the spacer bars from the carbonized grids, the end turns of the grid are freed of :the usual carbon coating.

upper spacer and mica disc under the welded tabs at the-upper end of the anode side rods. The electrode leads are then connected to their proper contacts in the press and the lower shield I6, which is provided in two halves, is welded to their support rods IT. The fabrication of my mount assembly is completed by strapping the upper shield 22 in place by welding its strap 23 to the elamping rods 24-25, which are finally welded at their lower ends to the lower shield. It will thus be seen that during assembly of the tube according to my invention all welding operations are effected from without the elements of thetube, which eliminates the diificulty of welding in confined spaces.

Inthe embodiment of my invention shown in thedrawing two equipotential cathodes mounted side by side are shown. When operated at ultra high freguency these two parallel cathodes may have an effect much like a tuned lecher wire system at the operating frequency, and hence considerable high frequency energy may be radiated directly from the cathodes. Under these conditions I prefer to connect the upper ends of these cathodes .as shown at 32 so ,as to short circuit any possiblestanding waves upon the cathodes.

Whereas I have disclosed the'preferred embodiment of my invention it is obvious to those skilled in theart that many modifications may be-made Without departing from the spirit of my inven tion. It is desired, therefore, that thescope of my invention be limited only by the art and by the appended claims.

Having describedmy invention, I claim- -1. A thermionic discharge device comprising reentrant stem with a press with lead-in wires sealed therein, a shield surrounding and mechanically secured to the stem, an electrode as- .sembly of the unit mount construction resting upon the upper edge of said shield, and electrical connections between-said electrode assembly and said lead-in wires.

2. A thermionic discharge device comprising an envelope with a re-entrant stem having a press at one end, a shield member surrounding. said press and supported by the stem, an electrode assembly of the unit mount construction positioned on and mechanically supported by the shield member.

3. In a thermionic discharge device, a unit. mount construction comprising a stem with a press, a thermionic cathode, grid and anode electrodes each having a side rod, two insulating spacers arranged one above the other and recessed to receive the side rods of said electrodes, a shield-around the stem and supported by the stem, the upperedge of the shield being arranged to bearagainst the lower face of the lower spacer, an upper shield positioned over the upper ends of the gridside rods, and connecting means between; the upper and lower shields to mechanically and electrically tie the shields together.

4. A thermionic discharge device comprising an envelope and a press, cathode, grid and anode electrodes with side rods concentrically arranged and secured between two ceramic spacers one above the other, said spacers being recessed to receive the side rods of said electrodes, locking means secured to the ends of two of said side rods so as to form a unit mount assembly of the electrodes; a lower shield positioned around the press of the discharge device and supported thereon, the upper edge of the shield being arranged to bear against the lower spacer, a mica disc secured to the upper face of the upper ceramic spacer and clinched under said locking means, said disc being recessed centrally to receive the upper ends of said side rods, an upper shield positioned over said central recess, a strap formed over the upper shield, the ends of the strap being secured mechanically to the lower shield.

5. An electron discharge device comprising a glass stem with a press, support rods extending from said press, said support rods formed with curved portions, a tubular shielding member positioned around said press, means for supporting said member on said press comprising radially extending flanges on said member, said flanges being formed around the curved portions of said support rods to prevent movement of said member on the curved rods.

6. In a thermionic discharge device, a unit mount construction comprising an anode and concentric grid electrodes with side rods, an insulating spacer recessed to receive and hold the ends of said side rods, and a concave shield positioned over and around the ends of the grid side rods.

7. A thermionic discharge device comprising an electrode assembly of the unit mount construction with an insulating spacer bar, side rods inserted at their ends into and thru said spacer bar, electrodes secured to said side rods, a centrally recessed insulating disc secured to the side of the spacer bar opposite the electrodes, and a concaved shielding means positioned over the recessed portion of said disc to enclose said ends of the side rods.

8. In a unit mount construction, a side rod and a grid mounted on said side rod, an insulating spacer bar, a collar supported by said side rod concentric with said grid, and a depending flange from said collar arranged to cover one edge of said spacer bar.

9. An electron discharge device with a reentrant stem, a press on said stem, a tubular shield surrounding and supported by said press, an insulating spacer supported upon the upper edge of said shield, the edges of said shield being positioned inwardly from the edges of said spacer, a rod, a grid mounted on said rod, an annular collar supported on said rod adjacent one end thereof, said collar resting upon the upper side of said spacer, said collar having a flange extending downwardly over the edge of said spacer.

10. In a unit mount construction for thermionic discharge devices, ceramic spacers, cathode, grid and anode electrodes positioned between said spacers, and aluminum oxide collars on the anode side rods between the anode and spacers for spacing the anode electrode from said spacers.

11. In a thermionic discharge device, an envelope with a press, a cathode lead-in wire sealed in end to said lead-in wire, and means for electrically connecting the ends of the sleeves opposite the ends which are connected to said cathode lead-in wire.

CHARLES W. TAYLOR.

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