US2012431A - Vacuum tube - Google Patents

Description

Aug. 27, 1935. 1. E. MOUROMTSEFF VACUUM TUBE Filed April 11, 1929 a 5 6 2 3 2 3 a n 2 9 2 6 4 Z Q aiaE-EEE: u fl.=======-== F a 2 I H I 3 3 0 2 2 a a 2 M w w J g/z /A 5 6 5 8 m 4 l W I A 2 7 6 3 INVENTOR} [lid E Mouromlae/fi ATTORN EY Patented Aug. 27, 1935 UNITED STATES PATENT OFFICE VACUUM TUBE Ilia E. Mouromtseif, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application April 11, 1929, SerialNo. 354,290 1 Claim. (01. 250-475) power as possible at as short wave length as possible.

It has been found desirable, in building highpower tubes, to adopt long electrodes. With such electrodes parasitic oscillations of very high frequency occasionally arise which are accompanied by the productionof standing waves on the grid.

This has the disadvantage that a certain portion of the energy is wasted. It has the further disadvantage that very high potentials may be de- 1 veloped at points in the structure where the parts of glass, quartz, or other insulating material are exposed to the potential-gradient. The insula tion is thereby subjected to heavy stresses. Punctures, fusion or fracture may then be occasioned. It is an object of my invention to provide a means whereby the production of standing waves upon the grid will be prevented.

It is a further object of my invention to provide for damping the frequencies which tend to produce such waves. It is a further object of my invention to provide a connection uniting the two ends of the grid structure, distinct from the connections between the ends of the grid formed by the usual parts of the grid structure.

It is a further object of my invention to provide impedance devices which will prevent the flow of high-frequency current around the circuit comprising the usual grid structure and the additional connection.

Other objects of my invention and details of the construction will be apparent from the following description and the accompanying drawing, inwhich,

Figure l is a longitudinal section of one form of vacuum tube to which my invention is applied,

Fig. 2 is a longitudinal section of a tube of modified structure, and

Fig. 3 is a perspective view of a damping device which may be employed in a vacuum tube of either form.

In the vacuum tube illustrated in Fig. 1, the anode is a metallic cylinder l, sealed, at each end, into glass end- portions 2 and 3. The cathode 4 is mounted in a press in the glass end 2 in a usual way.

The grid is mounted upon a sleeve 5, clasping the press in the other glass end 3. Standards 6 are welded, or otherwise secured, to: the sleeve 5. For the sake of clearness, only two such standards are shown in the drawing but any convenient number may be employed and, ordinarily, four or six standards are provided. At their upper ends, the standards 6 are welded; or otherwise secured, to a metal ring 1 which surrounds the 5v press in the glass end 2 but is spaced away from it. The ring 1 is preferably supported by glass supports 8 which extend from it to the hollow part of the press.

' The standards 6 support the usual metal openwork constituting the grid proper and, with the rings 5 and l, constitute the usual grid structure. In the tube illustrated, the open-work is formed by winding a. fine wire Hi upon the standards, securing it thereto, at many points if not at every whorl, preferably by welding. If preferred, the grid structure may take any of the forms disclosed in my copending application, Serial No. 344,772 filed March 6, 1929 for Vacuum tubes.

The lead-in wire I! for the grid extends 20 through the press of the glass end 3 in the usual way. It is illustrated as branched and is connected to each of a plurality of thestandards 6. The conductor conveying the grid current is illustrated at l2. Itis branched, one branch being connected to the lead-in wire I! and the other branch, including a resistor 13 and a condenser i l, extending through a seal E5 in the glass end 2 to connect the conductor H. to the end of the grid structure. V

The connection, as illustrated, extends to the ring 1, but any convenient point near this end of the grid structure may be chosen for the terminus of this branch. The resistor l3 may, if desired, be replaced by a small concentrated inductance, for example, one or two turns, and the condenser it may be omitted, if desired.

In the form illustrated in Fig. 2, the vacuum tube is provided with but one glass end 29. The anode is a metallic thimble 2|, sealed into the 40 glass end 26, the usual connections for the oathode 22 extend through the press in the glass end 20.

The upper end of the cathode is supported by a quartz rod 23 which, in turn, is supported by the standards 24 which constitute part of the grid structure. The upper end of the quartz rod 23 is held stationary by means of a disk 25 extending to the wall of the tube. The rod is secured to the standards 24 in any desired manner.

For illustration, the rod is shown as fused, at 26, to a cross connection 2! uniting two of the standards 24. Although only two standards are illustrated, it is intended that any convenient 55 number of standards shall be used, and ordinarily there will be four.

The standards are secured, by welds or any other suitable joints, to a ring 28 clasping a glass sleeve 29 which extends upward from the bottom of the press.

The lead in wire for the grid is shown at 3! as extending through a seal 32 in the side of the glass endand connected, by welding or any other suitable joint, to the ring 28, which is part of the grid structure.

A connection 33 extends from the upper end of the standards 24 to a point near the ring 28 and is there connected, by soldering or other good electrical connection, to one of the standards 25. This conductor includes a resistor 34, preferably near one end thereof. If desired, a small in.- ductance, such as one or two turns, may beinserted in the conductor 33 instead of the resistor.

At its upper end, the conductor 33 is shown closely adjacent to the quartz rod 23 but this is not an essential location of the conductor end.

he quartz rod 23 extends a considerable distance from thepoint 28, at which the standards 2d are mechanically connected with it, to the top 35 of the cathode, at which point it is connected to the cathode to support the same.

In any power tube having an elongated grid structure, it is the usual practice to provide con-- siderable unoccupied length of the standards at each end of the metal open-work. This has been illustrated in Fig. 2, where the standards 2 extend considerably above and below the fine wire 36 which constitutes the open-work, as illustrated.

One way of providing the damping which may be employed as a substitute for or, in cooperation with, the impedance 3 1, is illustrated in Fig. 3. This device consists of a sleeve all which may be threaded upon the standard 25. during the manufacture of the tube. One of these devices may be located upon each standard above and another below the metal open-work, or a smaller number of such devices may be used if the damping to be effected thereby is small.

, The sleeve M is equipped with a plurality of fins t i The fins, or preferably, the whole device, will be of magnetic material.

In the operation of my invention; when the power tube is generating oscillations, any frequency capable of producing standing waves upon the grid structureis rendered ineffective. In Fig. 1, this is done by supplying grid potential to both ends of the grid structure. The grid current arrives through the conductor i2 and is supplied to one end of the grid through the lead-in wire I i and to the other end of the grid through the resistor 13 and the condenser i l. The presence by the resistor l3.

of the condenser prevents any direct-current component of the grid current from entering the tube through the seal l5. The total current carried by the seal [5 is, therefore, small and a less elaborate lead-in structure is needed than that shown at H.

The frequencies most likely to produce standing waves upon the grid are multiples of the fundamental frequency of the grid structure to electrical oscillations. Such frequencies, if present, will tend to generate a current of this frequency in the circuit comprising the grid structure and the connection through the condenser l4 and the resistor i3. Such currents will be rapidly damped This will prevent parasitic frequencies corresponding to such standing waves from occurring but will not interfere with the basic frequency of the circuit in which the tube is situated, which ordinarily differs widely from the parasitic frequency.

In Fig. 2, the connection from the upper part 21 of the grid structure to a point in it near the ring 28 completes a circuit in which current would flow if the frequency tending to produce standing waves were present, but oscillation at this frequency is prevented by the damping action of the resistor t l or by the impedance of the self-inductance located at this point. In this Way, the frequency corresponding to standing waves on the grid cannot be one of the natural periods of the system, and standing waves will, therefore, not be produced.

If the devices illustrated in Fig. 3 are located on the standards, in the grid structure of either Fig. l or Fig. 2, the high frequency currents will induce eddy currents in the magnetic material which will thus act as a damping means. The production of standing waves will thus be prevented in the same way as by the other damping means described.

Although I have illustrated and described only a few modifications of my invention, many other variations will be readily apparent to those skilled in the art. The absence of any specific description thereof is not intended as a limitation. No limitation is intended except that required by the prior art or expressed in the accompanying claim.

I claim as my invention:

A vacuum tube including an anode, a cathode, and a grid structure, connecting means extending from the ends or" said grid structure, an impedance and a capacity, said impedance and capacity, only, forming a closed circuit with said grid structure and connecting means, and a grid input connection to said closed circuit.

ILIA E. MOUROMTSEFF.

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