US2203516A - Metal radio tube - Google Patents

Description

June 4, 1940.

J. E. BEGGS METAL RADIO TUBE Filed Dec. 29, 1937 Inventor James E. Beggs,

' His AttOTT'IQy.

Patented June 4, 1940 METAL RADIO TUBE James E. Beggs, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 29, 1937, Serial No. 182,285

1 Claim.

The present invention relates to electron discharge apparatus, and more particularly to thermionic devices employing metal envelopes.

In metal radio tubes, it is customary to provide 5 ananode in the form of a cylinder which surrounds the cathode and grid or grids, and is in turn surrounded by the metal envelope. This anode cylinder is perimetrically complete and since all portions of the grid and the envelope are presented to an adjacent portion of the anode, the capacity effects between the anode and grid onthe one hand and between the anode and the envelope on the other hand are generally large. Moreover, the prior type of anode contains considerable metal due to the fact that it is a c0mplete cylinder having a length corresponding to the length of the enclosed grid. It is difficult sufficiently to denude such a large body of metal of gas and consequently, considerable time must 0 be taken to evacuate tubes containing anodes of this character.

An object of the present invention is to provide an improved metal tube in which the capacity between the electrodes and between the .5 anode and the shell or envelope is reduced to a minimum. Another object is to keep the amount of metal in the tube, particularly in the anode, as small as possible and thus permit rapid and effective denudation of the metal parts. These 0 objects are attained in brief by dividing the anode into two portions of limited size, electrically connected together and arranged on opposite sides of the cathode, away as far as possible from any side rods or metal supports. The invention will 5 be better understood when read in connection with the following specification and accompanying drawing in which Fig. 1 is an elevational view, partly in section, of a tube improved in accordance with the present invention. Fig. 2 is an en- 0 larged view of a section taken along line 2-2 in Fig. 1.

Referring more particularly to Fig. 1, numeral I designates a metal cylinder or shell which is provided with an integral closure 2 at the top and 5 terminates at the lower end in a flange 3. There is an inverted cup-shaped member 4 of somewhat larger size than the flange 3 securedto the latter, preferably by welding. The cup member 4 contains a disk of a phenolic condensation 0 product, which terminates at the bottomin a portion 5 preferably of the same diameter as the member 4. This disk serves as a support for. a number of contact pins or terminals 6 symmetrically arranged about a centrally positioned rod 1 of the same material as the disk.

This rod carries a key or projection (not shown) for locating the tube in a socket (not shown) which is provided with openings to receive the contact pins 6. The rod is hollow and may contain a metal tubulation used for exhausting the 5 envelope as is well known in the art. The flat portion of the cup-shaped member 4 is provided with a plurality of openings depending upon the number of electrodes contained within the shell, and about each opening there is secured an eye- 10' let (not shown) extending into the shell. These eyelets accommodate 1eading-in conductors which are connected to the contact pins 6 and to the electrodes. The conductors are insulated from the eyelets by beads of glass; the Beggs Patent Id No. 2,093,302 granted September 14, 1937, shows and describes this eyelet form of seal.

The electrode structure within the envelope is supported primarily from a pair of oppositely positioned side rods 9 which are insulatingly supported from the base or flat portion of the cup-shaped member 4. These side rods carry a pair of horizontally positioned cup-shaped members Ill having their recessed portions presented to one another. There are some mica disks (not shown) contained within these recesses and provided with small openings which receive the uprights or support rods II for mounting the grids and cathode l2, which will be described hereinafter, in position. The members II] are provided 39 with rectangular grooves (not shown) so as to allow these uprights to extend through the mica disks and through the metal members lfl without being short-circuited.

The cathode is preferably of the indirectly 35 heated type which is well known in the art and consists simply of a heater and a metal covering member coated with an efiective electronemitting material such as barium carbonate. As shown in Fig. 2, I have exemplified my invention 40 in connection with .a so-called pentode which includes a control grid l3, a screen grid l4, and a secondary emission suppression grid l5. As stated hereinbefore, all of these grids are" mounted on uprights II which are preferably arranged in line with one another and in line with the anode support rods 9, on opposite sides of the cathode. The grids are of the standard wound or mesh type.

Whereas in the prior form of tubes, it is customary to provide an anode of carbonized or sandblasted nickel in the form of a cylinder completely surrounding the grids, in accordance with my invention I employ anodes having a circular or cylindrical shape but of a discontinuous perimeter arranged on opposite sides of the cathode. As shown, the improved anode takes the form of-arcuate members It which are secured as by stapling, indicated at H, to

a pair of mica strips l8. These strips are secured, also by stapling or in any other suitable manner, to opposite sides of the peripheral edge of the members Ill. These anodes are preferably fabricated of carbonized nickel and have a width determined by experiment and depending upon the spread of the electron stream as it leaves the cathode and travels toward the anode.

tion as the cylindrical form of anode.

It has been found as. the result of exhaustive tests on the improved anodes of restricted size,

and notwithstanding the fact that they do not extend around the entire periphery of the oathode and grids, the anode portions nevertheless collect practically all of the electrons emitted by the cathode. The electron paths are indicated by the dotted lines in Fig. 2, and it will'be appar ent that those electrons which are not intercepted by the grids and which normally do not travel in straight lines toward the anode are actually attracted by the strong field of the anode and caused to change their direction so as to strike the anode. Consequently, many more electrons reach the anode than those which leave the cathode within an arc subtended by the anodes. Those electrons which do not reach the anode are for the most part the same electrons which would not reach the cylindrical anode of the conventional tubes on account of being intercepted by the grids. Consequently, from the efficiency standpoint, the arcuate an odes which are provided in accordance with my invention offer little or no disadvantage from. the standpoint of attracting electrons over the conventional cylindrical form. of anode. It is apparent that on account of the fact that the improved anodes do not completely surround the control grid, the grid-to-anode capacity is much lower than in a tube employing the conventional type of anode. The same thing is true of the anode-to-shell or envelope capacity, since the anode does not present itself to all portions of the envelope. By limiting the width of the anode to only a fraction of the anode found in the prior tubes, I am enabled to reduce the amount of metal in the tube,which permits a more rapid exhaust. It is also apparent that the arcuate anodes do not completely surround the grids and hence, these grids may obtain heat by direct radiation from. the metal envelope when the latter is heated during the degassing period. Another advantage of the arcuate type of anode is that it permits inspection of the grid lineup and the internal parts after the mount is assembled, which obviously would'not be possible if the anode constituted a' complete cylinder.

As contrasted with the marked advantages of the improved anode, there are no apparent disadvantages because the greater portion of the cathode current, due to the side rod effect, flows within the arc subtended by the arcuate anodes and what little current does flow outside this arc falls into the field of the anode after passing through the outer grid and is collected by the arcuatev anodes. The arcuate anodes have sufiicient'area to dissipate the necessary heat, since they are quite far removed from the cathode.

It will be apparent that the use of arcuate anodes in place of the conventional or standard cylindrical type of anode of continuous perimeter provides a tube with the advantages set forth above and yet offers no disadvantages as compared with similar tubes having the standard form of anode.

What I claim as new and desire to secure by Letters Patent of the United States is:

An electron discharge device comprising a metal envelope containing a plurality of elec. trodes including a cathode and an anode of elongate configuration, a framework supporting said electrodes, said framework including a pair of spaced metal disks extending transversely of JANIES E. BEGGS.

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