US2455218A

US2455218A - Ultra high frequency tube

Info

Publication number: US2455218A
Application number: US617035A
Authority: US
Inventors: Richard S Briggs
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1945-09-18
Filing date: 1945-09-18
Publication date: 1948-11-30
Anticipated expiration: 1965-11-30

Description

Nov' 30, 19.48. R. s. BRIGGS ULTRA HIGH FREQUENCY TUBE Filed Sept. 18. 1945 w u 2 5m 4 3 w w. m 5

r EV w 4 2 W 3. 2

' INVENTOR. Richard S. Briggs BY ATTORNEY Patented Nov. 30, 1948 ULTRA HIGH FREQUENCY TUBE Richard S. Briggs, North Beverly,'Mass., assignor to Sylvania Electric Pro a corporation of Mass ducts Inc., Salem, Mass, achusetts Application September 18, 1945, Serial No. 617,035

2 "Claims.

This invention relates to ultra high frequency tubes and in particular to tubes employing a resonant circuit of the cavity type.

Such tubes heretofore have been made with the metal parts of the cavity extending directly through and sealed to the-glass walls of the tube, forexample, as shown in the patent application Serial No. 490,703 filed on June 12, 1943, by H. J. McCarthy, and now U. S. Patent No. 2,413,364, granted December 31, 1946.

My invention provides a means of making tubes for resonant cavities withoutthe necessity of sealing portions of the cavity through the glass walls of the tube.

I couple high frequency conducting elements inside the tube to those outside by capacitative coupling directly through the glass dielectric walls of the tube, by providing those elements with sufiicient surface areas in register through said glass. of the high frequency elements and the glass of the tube are thus eliminated, with consequent increased mechanical strength of the tube and obviation of the difiiculty of. securing uniform and adequate contact to the conductors otherwise necessary to complete the-cavity outside the tube. Although I have used the word glass. in describing the invention, I haveused it in ageneric senseto include any dielectric material of which the tube may be made, such as quartz, ceramics or the like in addition to the more usual tube glasses.

A particular feature of the invention is a simplified oscillator tube using my construction, although my invention is applicable to any type of tube employing a cavity part of which is external to the tube, and is particularly applicable, for example, lighthouse tube, and to tubes such as shown in the previously mentioned McCarthy application.

Other objects, features and advantages of my invention will be apparent from the following specification taken in conjunction with the accompanying drawings.

Figure 1 shows a profile section of my invention; and

Figure 2 shows a plan view.

In Figure 1, the envelope I may be a bulb of glass, quartz, or the like, as previously noted. The lead-in wires I8 and 2B are connected to, and support, the cathode 4 which may be, for example, a nickel cylinder coated with one or more of the alkaline earth oxides or other material of low-work function. One end of the filament heater coil 5 is also connected to the lead-in Difficult ring seals between the metal "passes through the The portions Wire l8 and the other end of the cathode heater coil is connected to the lead-in wire I9. The

lead-in wire I1 is attached to the "small grid-lead choke coil 8 which in turn is connected to the grid cup '3 which surrounds the cathode and which has an annular opening covered by the .grid II which may be of wire mesh. The cylindisc I6 and may be attached thereto by the eyelets 26 if desired. The anode cup 2 is sup-ported above the grid II and is spaced therefrom by the insulator rods or support I2. This anode cup comprises a flat circular end 21 close to the grid I I but spaced therefrom, the cylindrical walls 28, the annular portion 29 and the cylindrical portion '30, all of which portions are in electrical connection and are preferably all in one piece. The top of the plate may have flanges or tabs 3| which may be connected to the mica spacer or disc l5 by the insulating supports l3. The plate choke coil 9 may be connected from the circular flat part of the plate to the lead-in wire I which glass envelope I at the bead 3|. Similar beads 32, 3'3, '3 4 and 35 surround the other lead-in wires I1, l8, I9 and ill. If desired, theusual stem press common. in radio tubes may be used around these lead-in wires instead of the separate beads shown.

The elements so far described are all parts of the tube proper and form one integral unit. The metal toroid or cavity 6 is a separate unit external to the tube and is made of good high frequency conducting material such as copper, or silver, or may be merely plated with such a metal, if desired. In the lateral cross section as shown in Figure 1, the walls of the toroid do not completely close but have the fiat portions 2| and 22 parallel to the glass of the tube and spaced apart from each other in order to form a resonant cavity in conjunction with the elements inside the tube. 23 and 3B of the anode and grid cups are likewise fiat and parallel to the glass walls of the tube and act with walls 2! and 22 of the cavity to form condensers which couple the external and internal parts of the cavity 6. The walls 2| and 22 of the cavity 6 outside the tube may bear directly on the glass envelope I of the tube, but it will be desirable to separate the

walls

30 and 23 of the anode and grid cups from the tube wall I so that the anode and grid cups may be heated by high frequency induction during the manufacture of the tube, to drive ofli any occluded gases. It will generally be desirable to place the

walls

23 and 30 of the grid and anode cups as close to the walls as possible without the danger of cracking the walls of the glass when the anode and grid cups are heated during the exhausting of the tube. The tube will ordinarily require a high vacuum."

It is now clear that the cavity 6 will be capacitively coupled to the grid with them form one complete cavity of definite resonant frequency and that in the particular construction shown, the tube with its cavity will form an oscillator of the Hartley type, the cathode being connected to the external cavity at some convenient pointwhich will allow oscillations.

The same type of capacitively coupled cavity construction may, of course, be used in other types of tubes as already explained, that described being merely by way of example and not by way of limitation. My capacitively coupled cavity is applicable to all types of tube otherwise using a resonant cavity extending conductively through the glass walls of the tube.

It is clear that the inner

cylindrical walls

23 and 30 of the grid and anode cups 3 and 2 should be very close to the glass walls of the tube but spaced slightly therefrom in order to allow proper heating of the anode and grid cups 3 and 2 during the manufacture and exhaust of the tube. The cylindrical area of these anode cups must, of course, be large enough to provide the necessary coupling capacity, which will ordinarily not need to be very great at ultra high frequency. The elements in the tube, particularly the grid and anode cups must be very rigidly held and kept accurately in line with each other and should be arranged so that the spacing between them remains uniform over the normal range of tube operating temperatures.

The metal anode and grid cups 2 and 3 should be made of, or at least plated with, a material of good conductivity for ultra high frequencies.

The insulating spacers l2, l3 and 14 may best be in the form of short rods, spaced around the surface of the parts supported.

What I claim is:

l. Ultra-high frequency apparatus including a vacuum tube comprising: a sealed cylindrical diand anode cups and portion extending from said fiat circular end to an annular portion, and a cylindrical portion close to but spaced from said cylindrical envelope,

all portions of said anode cup being in electrical connection with each other; and a toroidal metal cavity resonator coaxial with said envelope and having its inner wall cylindrical, with a cylindrical opening along the middle of said inner wall to divide the same into two opposite cylindrical walls close to but spaced from said cylindrical envelope, extending toward each other but having their edges spaced from each other, one of the cylindrical Walls of said resonator being in register with the cylindrical metal wall of said grid cup and in capacitive relationship therewith and the other of said cylindrical walls of said resonator being in register with the cylindrical portion of said anode cup and in capacitive relationship therewith.

2. The combination of claim 1, and lead-in wires for said cathode, said grid cup and said anode cup extending through said envelope; a choke coil inside said envelope and connecting said anode cup to one of said lead-in wires; and another choke coil inside said envelope and connecting said grid cup to another of said lead-in wires.

RICHARD S. BRIGGS.

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

UNITED STATES PATENTS Number Name Date 2,253,080 Maslov Aug. 19, 1941 2,312,723 Llewellyn Mar. 2, 1943 2,353,742 McArthur July 18, 1944 2,414,785 Harrison et al Jan. 21, 1947 2,420,846 Strutt et al May 20, 1947