US2422819A

US2422819A - External anode electron tube

Info

Publication number: US2422819A
Application number: US549567A
Authority: US
Inventors: George A Becker
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1944-08-15
Filing date: 1944-08-15
Publication date: 1947-06-24
Anticipated expiration: 1964-06-24

Description

June 24, 1947. s. A. BECKER- 3115mm. moms mac-men TUBE Filed Aug. 15, 1944 3. Sheets-Sheet 1 mvmvmx. George 4 Becker BY ATTORNEY June 24, 1947. G. A. BECKER EXTERNAL mom: ELECTRON TUBE 3 Sheets-Sheet 2 Filed Aug. 15, 1944 INVENTOR. George A. Becker By J! ATTORNEY June 24, 1947. BECKER 2,422,819

EXTERNAL ANODE ELECTRON TUI SE Filed Aug. 15, 1944 3 Sheets-$heet 3 44 v .5. ||I l,

F f2? INVENTOR. George A. Becker ATTORNEY Patented June 1947 EXTERNAL ANODE ELECTRON TUBE George A. Becker, San Bruno, Califl, assignor to Eitel-McCullough, Inc., San Bruno, Calif., a corporation of California Application August 15, 1944, Serial No. 549,567

7 Claims.

My invention relates to an electron tube having an external anode.

It is among the objects of my invention to provide an external anode tube embodying an im-e' proved arrangement for and construction of the electrodes and associated envelope.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure l is a perspective view of a triode tube embodying the improvements" of my invention; and

Figure 2 is a vertical sectional view of the same.

Figure 3 is an enlarged detail sectional view taken transversely through the lower portions of the filament structure.

Figure 4 is a vertical sectional view showing a tetrode.

In terms of broad inclusion, my tube comprises an envelope having an intermediate metallic portion forming an external anode. A cathode supported by one end of the envelope extends into one end of the anode, and a grid supported by the opposite end of the envelope extends into the other end of the anode. Vitreous envelope sections are provided at each end of the anode, and the grid is connected to a metallic envelope section sealed to one of the vitreous sections. A cooler is provided on the anode between the vitreous envelope sections. In a modified tube 1 provide a second grid supported by the end of the envelope opposite the first grid and extending into that end of the anode into which the cathode extends.

In greater detail, and referring to Figures 1 and 2 of the drawing, a triode tube embodying my improvements comprises a tubular external anode 2 of a suitable metal such as nickel or Kovar, arranged to form the intermediate section of the tube envelope. The anode is preferably provided with enlarged end portions 3, of a metal having good glass sealing properties to which vitreous or glass envelope sections 4 and B are fused at seals I. The vitreous sections are also tubular, forming an elongated envelope of generally cylindrical shape.

The lower end of the envelope supports the cathode structure 8, and for this purpose is preferably provided with a reentrant stem 9 carrying an exhaust tubulation 10 through which the envelope is finally evacuated. The cathode chosen for illustration is of the filamentary type having longitudinal bars I I of thoriated tungsten divided into four groups disposed in cylindrical formation about the cathode axis, each group of wires being connected at the lower end to one of the four cathode leads [2 and all being connected at the upper end to a common terminal [3.

Fixed supports for the lower ends of the filament wires are provided by brackets 14 on leads I2, which leads are sealed to stem 9. Top cap or terminal l3 provides a movable support and is held centered by a rod or standard l6 sealed to the stem and projecting through the cap. Tension is applied to the filament wires by a sleeve I5 slidable along the center rod and urged upwardly against cap l3 by a spring l1 interposed between the sleeve and stem. In the final tube diametrically opposed cathode leads l2 are connected in parallel to a source of heating current. Since two of the groups of filament wires are connected in series with one pair of leads and the other two groups in series with the other two leads, all are simultaneously heated. This compact filament structure provides a large amount of electron emitting surface. It is understood of course that other types of cathode structures may be used.

It is to be noted that the cathode structure has a free end and is supported entirely by one end of the envelope with the free end of the cathode structure extending coaxially within anode 2 from one end thereof. This free ended structure makes it possible to insert the cathode into the tubular anode section while the parts are rotating coaxially on the head and tail stocks of a glass lathe, whereby accurate alignment is automatically insur ed when the cathode stem is finally sealed in place. The final seal may be made at the stem flare-along a plane perpendicular to the electrode axis as indicated by line 20 in Figure 2. Such a structure and procedure for attaining alignment is particularly important in an external anode tube because the solid metal wall hides the internal parts.

Any suitable base may be provided on the tube. I prefer to use a single pronged coaxial type base comprising a metallic shell [8 connected to a pair of the cathode leads and secured to the envelope by cement IS. A disc 2| of insulating material serves to support a hollow metallic center prong 22 which is connected to the other pair of cathode leads. During operation of the tube the stem is preferably cooled by air admitted through prong 22 and exhausted through vent openings 23.

Grid 24 is supported from the end of the envelope opposite that of the cathode. The grid is preferably of the cage type comprising vertical bars 26 and a reinforcing spiral 21 secured to end rings 28. Support and terminalconnector means for the grid is provided by a tubular metallic envelope section 29 coaxial with the electrodes and fused to envelope section 4 at seal 3i. Section 29 is of a metal, such as Kovar, having good glass sealing properties. The grid is mounted on tubular section 29 by a suitable bracket 32, preferably conical in shape, welded at one end to a grid ring 28 and at the other end to section 29. Part of envelope section 29 projects outwardly from the vitreous section 4, thus providing an external terminal surface for making connection with the grid. The grid may be made of any suitable material having the desired physical and electrical properties.

It is to be noted that the grid also has a free inner end and is supported entirely by one end of the envelope, the grid extending coaxially into that end of the anode opposite the cathode with the free end of the grid telescoped over the free end of the cathode. This permits the grid to be inserted into the anode section while the parts are rotating coaxially in a glass lath when envelope section 29 carrying the grid structure is sealed in place. The final seal at this end is preferably made along a plane perpendicular to the axis of the envelope as indicated by line 35 of Figure 2.

In order to check alignment of the internal electrodes I preferably supply a transparent vitreous end piece 33 on the envelope, sealed to the outer end of tubular section 29, to provide a window for viewing the internal parts. This end piece may be fiat sided or shaped like a lens to magnify.

A cooler 34 is also Preferably provided on anode 2 between the

vitreous sections

4 and 6 forpurposes of dissipating heat from the anode. This cooler preferably has longitudinal fins 36 and may be of any suitable metal such as copper or aluminum. It may be secured to the anode in any suitable manner, as by a high melting point solder 31.

A modified tube or tetrode embodying my invention is shown in Figure 4. In this case grid grid 24 functions as a control grid and a second or outer grid 38 functions as a screen grid. The screen grid is supported by the same end of the envelope as the cathode, and projects into the anode with its free end telescoped over the free end of the control grid. The screen grid is mounted on a conical bracket 39 secured to a metallic ring-like envelope section 4| which provides a terminal for the grid. This metallic section, say of Kovar, is fused to vitreous section 6 at seal 42 and to a third vitreous section 43 at seal 44. The latter section carries filament stem 9. Otherwise the tube structure is similar to that first described, as indicated by like reference numerals.

I claim:

1. An electron tube comprising a, tubular external anode, vitreous envelope sections sealed to opposite ends of said anode, a cathode supported by one of said vitreous sections and extending into one end of the anode, cathode tensioning means supported on the last mentioned section, a tubular metallic envelope section coaxial with the anode sealed to the other vitreous section, and a grid supported by said metallic section and extending into the other end of the anode.

2. An electron tube comprising a tubular external anode, vitreous envelope sections sealed to opposite ends of said anode, a tubular metallic envelope section coaxial with the anode sealed to each of said vitreous sections, a grid supported by one of said metallic sections and extending into one end of the anode, a second grid supported by the other metallic section and extending into the other end of the anode, a third vitreous envelope section sealed to one of said metallic sections, and a cathode supported by said third vitreous section and extending into the anode.

3. An electron tube' comprising a tubular external anode, vitreous envelope sections sealed to opposite ends of said anode, a metallic envelope section sealed to each of said vitreous sections, a control grid supported by one of said metallic sections and extending into one end of the anode, a screen grid supported by the other metallic section and extending into the other end of the anode, a third vitreous section sealed to the last mentioned metallic section, and a cathode supported by said third vitreous section and extending into that end of the anode into which the screen grid extends.

4. An electron tube comprising an envelope having a metallic intermediiate portion forming an external anode, said envelope having a metallic sleeve section adjacent one end thereof, and an internal electrode supported by said sleeve and extending within the anode, said envelope having a transparent vitreous en'd piece sealed to said sleeve to provide a window for viewing the internal electrode.

5. An electron tube comprising an envelope having a tubular metallic intermediate portion forming an external anode, a cathode structure supported entirely by one end of the envelope and having a free end extending into one end of the anode, a grid supported entirely by the opposite end of the envelope and having a free end extending into the other end of the anode and telescoped over said free end of the cathode structure, and a, second grid supported entirely by the first mentioned end of the envelope and having a free end extending into that end of the anode into which the cathode extends anid telescoped over said free end of the first gr d.

6. An electron tube comprising an envelope having a tubular external anode, a pair of concentric cathode terminal members supported on the envelope coaxial with the anode, a grid terminal member on the envelope coaxial with the anode, a cathode in the envelope connected to said cathode terminal members, a grid in the envelope connected to said grid terminal member, and an insulating ring interposed between the inner andouter cathode terminal members, the largest diameter of said insulating ring being less than that of said. outer cathode terminal member.

7. An electron tube comprising an envelope having a tubular external anode, a pair of concentric cathode terminal members supported on the envelope coaxial with the anode, a pair 01 grid terminal members on the envelope coaxial with the anode, a cathode in the envelope connected to said cathode terminal members, and a pair of grids in the envelope each connected to one of said grid terminal members.

GEORGE A. BECKER.

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

UNITED STATES PATENTS Number Name Date 2,391,927 Segerstrom Jan. 1, 1946 2,272,374 Kallmann 'Feb. 10, 1942 Number Number I 5 670,918 572,275

Name Date Gibson et al. Oct. 9, 1934 Mouromtsefl Apr. 12, 1932 Hull Aug. 30, 1932 Herrmann Sept. 1, 1936 Ronci May 17, 1927 Garner July 4, 1939 Smith July 4, 1939 Mouromtsefi June 24, 1930 Koch Nov. 13, 1934 Roncl et a1. Oct. 9, 1934 FOREIGN PATENTS Country Date France Aug. 26, 1929 Germany Mar. 13, 1933