US2354946A - Electronic tube - Google Patents

Description

1944. 'r. A. COHEN ELECTRONIC TUBE Filad Jan. 22. 1942 2 Sheets-Sheet 1 77moa0m 4. Col: m, vmo WM A fl'orn ey Aug. 1, 1944. 'r. A. COHEN ELECTRONIC TUBE Filed Jan. 22, 1942 2 Sheets-Sheet 2 VIII III

Theodore A (0/: en, mvmon, BY M X/ A ffarn e Patented Aug. 1, 1944 ELECTRONIC TUBEv Theodore A. Cohen, Chicago, Ill., assignor, by mesne assignments, to Wheelco Instruments Company, Chicago, 111., a corporation of Illinois Application January 22, 1942, Serial No. 427,794

9 Claims. (Cl. 250-275) This invention relates to electronic tubes in general and more particularly to such tubes wherein a high degree of sensitivity and dependability is required.

In electronic tubes for use in electronic appa ratus requiring a high degree of sensitivity and dependability of operation, e. g., when used in connection with automatic burner control apparatus, vacuum tube voltmeters, measuring apparatus, television, etc., leakage between the control and controlled elements, within or without the tube enclosure, would be apt to cause the tube to function erroneously.

It is accordingly the primary object of this invention to provide an electronic tube, and method of making the same, wherein leakage between the control and controlled electrodes is minimized and such as remains is rendered ineilective.

Other and further objects of this invention will become more apparent hereinafter as the same becomes better understood from an examination of the specification and claims in conjunction with the accompanying drawings wherein:

Fig. 1 is a vertical sectional view, partly frag mentary, and with certain parts in elevation, showing an electronic tube embodying this invention;

Fig. 2 is a similar view showing a modified form of the invention; and

Fig. 3 is a horizontal sectional view taken at the line 33 of Fig. 2.

Referring to the drawings more particularly, reference character I designates an envelop of a vacuum tube having a stem 2 and base 3. A support rod 4 in the stem supports a cylindrical cathode 5 within which is mounted a conventional cathode heater 6 (shown fragmentarily) in the usual manner.

Instead of the usual mica intersupport between the plate grid and cathode with its attendant leakage path and resultant bad effect upon the sensitivity or dependable operation of the tube, I provide an annular mica disc I which acts as a separator between cathode 5 and plate support rod 8, said disc being fitted to said cathode and locked tocollars I! mounted at the top of plate support rods 8. A second annular insulating disc I is also fitted, at its inner periphery, I

to cathode and has its outer margin locked to collars (similar'to I'I) mounted at top of grid support rods II. A conventional spiral grid I2 is suitably attached to grid support rods II. A metal separator ring I5 is also fitted around cathode 5 and contacts both mica separators I and I0 whereby any leakage path which may be present between plate and grid along said separators is contacted at an intermediate point by said ring which is at cathode'potential. Therefore any leakage path is split into two components which are respectively distributed in parallel with the grid cathode load and the plate cathode load, such distribution resulting in counteraction between the grid-cathode leakage effectand the plate cathode leakage effect and thereby making the plate-grid leakage resistance inefiective to cause erroneous function in the tube circuit system.

A similar arrangement is provided at the bottom of the electrode structures comprising an annular mica separator disc Ia fitted to cathode 5, at the lower end thereof, and attached to lock collars I'Ia at the lower end of plate support rods 8. A mica separator Illa likewise is fitted to cathode 5, near the lower end thereof, and said separator is attached to lock collars on the lower end of grid support rods II. A metal separator ring I5a is fitted to the lower end of cathode 5 and acts to contact any leakage path which may be present between plate and grid along separators Ia and Illa to bring said path to cathode potential to render such leakage ineffective.

Metal wire elements 9 in stem 2 extend upwardly to support rods 8.

A grid lead I3 extends from one of the metallic grid supports II downwardly through an aperture in disc Ia to a conductor I4, through stem 2, to a grid base lead 25, the latter leading to a grid base prong 28.

Sealing cement 23 acts to seal the envelop I in base 3.

A plate base lead 24 extends from one of the plate support wires 9 to plate base prong 29.

A cathode base lead 26 extends from one of the cathode support rods 4 to an annular base shield 21 around grid prong 28 and this shield is in turn connected to a cathode prong 30. Thus any leakage path that may be present in the base, or below, between plate lead 24 and grid lead 25 or between plate prong 29 and grid prong 2B is bound to be contacted by shield 21 which is at cathode potential whereupon such leakage will be rendered ineffective.

'In order to minimize the leakage in the tube which results from the deposit of getter salts, during the manufacture of the tube, the getter 22 is mounted between a mica getter flash shield I8 and the upper inner end of the envelop I with said shield between the getter and the electrodes (including their supporting structure). The shield I8 is mounted on support studs I6 attached to and extending upwardly from disc 'I and is provided with perforations I9 so that the getter function in the process of exhausting the tube envelop of gases during manufacture will not be confined to the upper portion of the envelop above the shield. A getter cap support rod 20, preferably centrally mounted on the shield I8 and a getter cap 2| supports the getter 22 Referring to the modification shown in Figs.

2 and 3, the intersupporting structure between plate, cathode and grid, likewiseprovides an intermediate contact to any leakage path which may be present between plate and grid, which contact is connected to a tube prong for contacting a portion of an external circuit for rendering such leakage ineffective. As here shown, reference character 3| designates a cylindrical cathode having a conventional heater 32 (shown fragmentarily). A conventional spiral grid 33 surrounds said cathode and is supported by rods 34. A 'cylindricalplate 35, supported byrods 36, surrounds saidgrid. Three concentric circular spaced mica separator disc portions 3'lq, 31b and Nears connected together in the same plane and form an upper supporting disc 31 for the electrodes. Disc 31 is attached to cathode 3| and the upper ends of grid support rods 34 and plate support rods 36, disc portion 31a being attached to said rods 36, disc portion 311) being attached to said rods 34 and disc portion 310 fitting around cathode 3|. Disc portions 31a and 310 are connected to inner disc portion 31b by metal concentric shield rings 40 and 39, respectively. These metal shield rings are connected together by suitable conductors 42 which lead to a shield ring conductor 43 which may pass through the'stem to a suitable'prong for contacting an external circuit at adesired potential relative to the cathode or to the cathode, as before, for rendering the leakage in the tube between plate and grid inefiective; Conductor 43 and prong therefor may be connected to. either the cathode or a predetermined potential in the circuit in-which the tube may be used. Such predetermined potential may be a neutral point in said circuit or a neutralizing potential for overcoming the leakage effect of the aforesaid leakage path efiect upon said circuit.

The bottom supporting structure comprising a lower supporting disc 38 and concentric metal shield rings 39a and 40a is exactly similar to that described above except that it is attached to the bottom of cathode 3| and rods 34 and 36 instead of to the top thereof as in the case of the upper supporting structure. These shield rings 39a and Mia also lead to the common shield ring conductor 43.

'In this modification the same getter shield and support andthe same base lead and prong shield, which for brevity are not duplicated in this illustration, are also preferably used. 7

The advantages and operation of. the aforedescribed tubeswill be apparent without further description and I am aware that many changes may be made without departingfro'm the principles of this invention and I therefore do not wish to be limited to" the details' shown or described. 1

' Iclaim:

' 1. An electronic tube comprising a controlled and a control electrode; intersupportingstructure for said electrodes provided with rneans, therbetween, for contacting any leakage path and connectingthe same to a predetermined potential, an envelop enclosing said'electrodes' and structure and a getter shield 'separatinga portion of the interior of said envelop from said structure, with the gettensupported in said separated portion for minimizing the leakage path which may result from the deposit of getter salts on said structure.

2. An electronic tube comprising a controlled and a control electrode, intersupporting structure for said electrodes, an envelop enclosing said electrodes and structure and a uniformly perforated getter shield separating a portion of the interior of said envelop from said structure, and a getter supported in said separated portion for minimizing the leakage path which may result from the deposit of getter salts on said structrue.

3. An'electronic tube comprising a pair of concentrically mounted electrodes, concentric dielectric discs attached to the respective electrodes, a concentric metallic ring separating said discs and contacting the cathode for rendering any leakage between the electrodes ineffective.

4. An electronic tube comprising a pair of concentrically mounted electrodes, a centrally mounted cathode, concentrically mounted dielectric discs, one attached to each of said first electrodes and fitted around said cathode and a concentric metallic ring separating said discs and also fitted around said cathode for contacting any leakage path between said electrodes and connecting the same to said cathode for rendering such leakage inefiective.

5. An electronic tube comprising a pair of concentrically mounted electrodes, a centrally mounted cathode, concentrically mounted dielectric discs, one attached to each of said first electrodes and a concentric metallic ring separating said discs and connected to said cathode for contacting any leakage path between said electrodes and connecting the same to said cathode for rendering such leakage ineffective.

6. An electronic tube comprising a pair of concentrically mounted electrodes, a centrally mounted cathode, concentric dielectric discs attached to the first electrodes and an intersupporting annular metallic member separating said discs and connected to said cathode for contacting any leakage path between said electrodes and connecting the same to said cathode for rendering such leakage inefiective.

7. An electronic tube comprising a cathode, concentrically mounted electrodes, concentric dielectric discs attached to the respective electrodes-a concentric metallic ring separating said discs, said ring connected to said cathode for contacting any leakage path between said electrodes and connecting the same to said cathode for rendering such leakage ineffective.

8. An electronic tube comprising a cathode, a controlled electrode, a control electrode,-and intersupporting structure for said electrodes provided with a metallic ring separating such structure and fitted around said cathode for contacting any leakage path in said structure which may be present between said electrodes and for connecting the path to said cathode, for rendering such leakage ineffective.

9. An electronic tube comprising a plate, grid and cathode and intersupporting-structure therefor provided with a concentric metallic ring separating said structure between the plate and grid for contacting any leakage paththere-between and fitted around said cathode for connecting such-path thereto. u

e I THEODORE A. COHEN;-

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