US1980805A

US1980805A - Electron tube construction

Info

Publication number: US1980805A
Application number: US539184A
Authority: US
Inventors: Earl L Koch
Original assignee: EARL L KOCH HOLDING CORP
Current assignee: EARL L KOCH HOLDING Corp
Priority date: 1931-05-22
Filing date: 1931-05-22
Publication date: 1934-11-13
Anticipated expiration: 1951-11-13

Description

Nov. 13, 1934. E. Ko'cH 1,980,805

ELECTRON TUBE CONSTRUCTION Filed May 22, 1951 -2 Sheets-Sheet' 1 FM'YZTF E EFZZI Z1 01:22.

NOV. 13, 1934. H 7 1,980,805

ELECTRON TUBE CONSTRUCTION Filed May 22, 1951 2 Sheets-Shet 2 H II JFK/517217.77 Ma y Ear/[7.52755 Patented Nov. 13, 1934 PATENT OFFICE 1,980,805 ELECTRON TUBE CONSTRUCTION Earl L. Koch, Chicago, 111., assignor, by mcsne assignments, to Earl L. Koch Holding Corporation, New York, N. Y., a corporation of New York Application May 22, 1931, Serial No. 539,184

5 Claims.

This invention relates to improvementsin electron tube construction as applied more particularly to power tubes or thermionic generators such as are used for transmitting in radio broadcasting and radio telegraphy.

This invention has for one of its objects the provision of a new and improved arrangement of parts in a four element tube for eliminating feed-back through electrostatic coupling between the active grid element and the anode element of the tube. a

In transmitting systems of the high frequency type, it is essential that the capacity between the active grid element and the anode element due to coupling between these two elements be kept as low as possible, and it is to secure this end that this invention has been designed.

Another object of the invention is the provision of a shield or screen grid element which is disposed between the anode element and the active grid element of the tube; the active grid element being affixed at both ends to a suitable support; the shield or screen grid element being similarly mounted. The screen grid element completely surrounds the active grid element and fully shields the active grid element and its support from the anode element, to reduce the feedback through capacity coupling between the active grid element and the anode element to a minimum.

This method of mounting the elements also permits the terminal conductor of the active grid element to be placed at one end of the glass envelope of the tube to isolate it from the terminal conductors of the screen grid and filament; which are at the opposite end of the glass envelope; to prevent coupling from this source.

Further objects and advantages of the invention are set forth in the ensuing description, and several embodiments of the invention are illustrated in the accompanying drawings; but the disclosure is explanatory only, and the construction actually shown may be varied, as by altering the shape, size and arrangement of the parts,

without going beyond the principle of the invention or exceeding the scope of the appended claims.

On said drawings:

Figure 1 shows in section one form of tube according to the invention; and

Figure 2 is a similar View of another form.

The same numerals identify the same parts throughout.

Referring now more in detail to the invention as illustrated first in Figure 1, a tube is shown which comprises a container 1, with

reentrant glass stems

2 and 3 at the opposite ends forming supports for the elements of the tube. An annular band 4 secured to the stem 2 and a similar band 5 secured to the stem 3 are joined by rods 6, the ends of which extend through loops '1 integral with the

bands

4 and 5; and the rods are made fast in the loops 7 preferably by spot- Welding. The connecting rods 6 carry suitable wire helices 8 through the turns of which a screen 5 grid element in the form of a helix 9 is threaded. The helices 3 thus constitute supports for the screen grid helix, and maintain the individual turns of the screen grid 9 spaced suitable intervals apart.

The stem 2 is provided with a reduced extension 10 which has secured thereto an annular band 11. Rods 12 are provided, the ends of which extend through integral loops 13 on the band 11 andthe rods 12 are secured in the loops 13 as before by spot-welding. The other ends of the rods 12 terminate in a metallic disc 14 and are secured thereto in any suitable manner such as by brazing or welding.

Aconducting member 15 having one end sev cured to the disc 14 and its other end brazed to a thimble 16 of metal, which is in turn sealed in the reduced extension 17 of the stem 3, maintains the disc 14 in central position relative to the screen grid 9. The rods 12 also are wound 35 with suitable wire helices 18 through which a wire forming the active grid element 19 is threaded;

and the helices 18 provide support for the active grid element 19 and keep the individual turns of the grid 19 separated a desired distance apart.

The annular bands 20 which surround the extensions l0 and 17 are also provided with integral loops 21 through which the rods 6 also extend; and the annular bands 22, between the band 11 and the disc 14 are provided with inte- 5 gral loops 23 through which the rods 12 extend. These give added rigidity to the screen grid and active grid elements.

The filament 24' is in the form of a U-shaped member of suitable electron-emitting material, the ends of which are attached to the

conductors

25 and 26 which lead out through the ,stem 2. The other ends of the

conductors

25 and 26 are brazed to metal sleeves or thimbles 27 and 28 which are sealed in the ends of a pair of projections or

bosses

29 and 30 integral with a glass stem 31inside the stem 2 and fused thereto. Spacers 45 of suitable insulating material are provided with orifices through which the

conductors

25 and 26 extend to hold the said conductors apart.

Conductors

32 and 33 secured to the

thimbles

27 and 28 form the external terminals for the filament 24. The looped end 34 of the filament 24 passes under the hooked end 35 of shock absorbing member 36, and a rod 37 of quartz or other suitable insulating material is secured to the metallic disc 14,its other end carrying the member 36. The intermediate portion of the member36 is in the form of a coil spring 38 adapted to pull the filament 24 taut.

The anode or plate 39 is in the form of a copper tube or sleeve having sealed to its respective ends the

glass envelopes

40 and 41; which bear the

internal stems

2 and 3; and, with the anode 39, make up the container 1. The screen grid element 9, the active grid element 19 and the filament 24 are mounted between the

end stems

2 and 3 to form a structural unit which is easy to assemble in the container and facilitates alignment with the tubular anode 39.

The structural

unit comprising stems

2 and 3, the

grids

9 and 19 and filament 24, is inserted in the open end of the envelope 40; and, after the centering of the unit relative to the tubular element 39, the

stems

2 and 3 are 'fused orsealed in the ends of the respective glass envelopes or

sleeves

40 and 41. The remaining ends of the envelopes are then sealed to the opposite extremities of the anode 39. A lead in conductor 42 is suitably secured to the screen grid structure 19 and brought out through the stem 2 by a suitable seal 43. A conductor 44 affixed to the sealed-in thimble 16 provides means for connecting the active grid 19 to the external circuit.

To carry away the heat energy dissipated by the anode 39 water cooling is resorted to, and a water jacket 46 is placed around the tubular anode 39. Clamping rings 4'7 and 48 and nuts 49, having threaded engagement with the protruding ends of studs 50 and 51 in the ends of the water jacket 46, and flanges or collars 52 afiixed to the tubular anode element 39 secure the water jacket 46 to the element 39. Rubber gaskets 53 placed between the clamping rings 47 and 48 and the respective flanges of the water jacket 46 and the flanges 52 of the element 39 seal the same against leakage. Suitable openings in the wall of the jacket 46 serve as an inlet and outlet for the water or like cooling medium fiowing in the jacket 46.

The double support for certain elements of the tube permits the shield or screen grid element 9 which is mounted on the connecting rods 6 to be made sufficiently long to envelope fully the active grid element 19 and the rods 12; and hold the element 9 in concentric relation to the-active grid element 19 and the tubular anode element 39.

The stem 15, which acts as a support for the active grid element 19, also serves to connect the active grid 19 to the external conductor 44 at the end opposite that of the lead-in

connections

32 and 33 of the

filament

24 and 42 of the screen grid element 19. With the active grid element 19 thus completely surrounded by the screen grid element 9, the grid element 19 will be efiectively shielded from the anode element 39 and the feedback through capacity coupling between the active grid element 19 and the anode element 39 is reduced to a minimum, as is essential in a power tube used with a high frequency system.

In Figure 2, a four element tube of similar but simpler construction is shown without a

coolcarry clamping rings

4 and 5, and rods 6 connect these rings and constitute a support for the screen grid 19. The rods are secured in loops '7 on the

rings

4 and 5.

The

stems

2 and 3 have the reduced

portions

10 and 17 to which clamping rings 11 and 11a respectively are secured and connecting rods 12 are fastened to these rings by similar loops 13. The rings 20, similarly secured to the rods 6 serve to rigidly hold the rods '6 and prevent twisting. The bands 22 secured to the rods 12 are for the same purpose.

The filament 24, which is a loop of suitable material, is engaged at its looped end by the flexible spring member 38, which is in turn secured by an anchor rod 15a to the reduced end of the stem 3. The ends 24a and 24b of the filament extend up through projections 29a and 30a on the stem 2 in the form of

leads

25 and 26.

The envelope of the electrode elements comprises an intermediate portion which is in the form of a copper tube or anode 39-and

glass sections

40 and 41 sealed to the ends of the copper tube 39. The electrodes and glass stems as a unit are inserted into one end of the tube, and when in position can be centered in the copper anode 39 through which it extends. Thenthe

respective stems

2 and 3 may be sealed to the

respective glass sections

40 and 41 as in the first instance.

It is essential that the electrodes be held rigidly and in constant spaced relation, as any slight displacement of the electrodes while the tube is operating will cause frequency changes which are detrimental to perfect operation. The

grid elements

9 and 19 are held by the

helices

8 and 18 on the connecting

rods

6 and 12; which are in turn secured respectively to the

stems

2 and 3 to provide means to prevent any relative displacement of the

grid elements

9 and 19. The filament 24 being secured at its ends as before is quite stationary, and thus a tube is provided which is most constant and efiicient in its operation. The leads to the

grids

9 and 19 are shown at 42 and 44a respectively. p

In the usual tube of this class, the elements are mounted on a stem by rods which terminate in an insulating disc for additional rigidity. This construction has its drawbacks, as possible arcing will break down the insulation, producing gases which will greatly reduce the efficiency of the tube. With the improved tube herein described this risk is entirely eliminated.

Even with the use of an insulating member to connect the elements together at the free ends, it is difiicult to maintain the positions of the elements, especially in four element tubes. The use of insulating spacers is out of the question in high power tubes, thereby making it still more difficult to obtain rigidity of the parts. With the double support at each end absolute mechanical rigidity is afforded without danger of voltage breakdown between elements due to inadequate insulation, as all elements are afiixed to the glass stems with ample clearances between them.

What is claimed is:

1. A thermionic tube including a container, a filament therein, means at one end of the container forming a support for the filament, a tensioning device for the filament, a disc, a rod mounting the disc in the opposite end of the container, and an insulating stem rigid with said disc bearing said device.

2. In a thermionic tube a hollow anode, insulating sections aflixed to the ends of the anode,

said sectionseach having an internal stem, rods carrying a screen grid rigidly secured at their ends to each of said stems, a disc mounted on one of said stems and spaced therefrom, and a second set of rods enveloped by the screen grid rigidly secured to the disc and the other stem to carry a control grid in the tube.

3. A thermionic tube comprising a tubular anode, insulating sections at both ends of said anode, each section having an inside stem with a reduced extension, bands encircling both stems, rods rigidly attached to said bands for carrying a screen grid structure, stiffening bands on said rods, bands on the extensions, rods shorter than the first rods attached rigidly to the last-named bands, stiffening bands on the shorter rods, a control grid attached to the shorter rods, and. a filament having conductors passing through one of the sections and yieldably attached to the opposite section, said filament being supported substantially in the center of said control grid.

4. A thermionic tube having a tubular anode,

an insulating section secured to both ends of the anode, each section having an internal stem with an extension, a disc rigid with one extension, a band affixed to the other extension, rods attached to said disc and said other extension, a control grid mounted on said rods, stiifening bands engaging said rods, a filament mounted between said disc and said other extension, bands on the stems between said extensions and the outer extremities of said sections, rods affixed to said last-named bands, a screen grid on the lastnamed rods and stiffening bands for the lastnamed rods.

5. A thermionic tube having a disc adjacent one end within the tube, rods aflixed to said disc and to the other end of the tube adapted to mount a grid, an insulating stem aifixed to said disc, a filament within the tube, and resilient means on said stem engaging the filament.

EARL L. KOCH.