US3048726A - Electron discharge rectifier - Google Patents

Description

W.T. MlLLls ELECTRON DISCHARGE RECTIFIER Filed sept. 14, 1959 H 7 l 7 3 7 3 5 3 3 Il 9 3 l. H 5 2 f im 4 I 3 b 1| u f 9 l llll .i 3 l l-- uunnmwHHMll 3 9 9 )l :lll 9 4 Il 2 .1P Lll 4 7 RRHH H @I ---lllTIII -l J un, f|| ---l nnfwwHnwl l 1 5 9 3 9 l 5 M .1 I 3 3 l 3 5 2 .n 7 4 5 Aug. 7, 1962 FIG.3

FIG.

FIG. 2

ite States 4arent @dice 3,048,726 ELECTRON DISCHARGE RECTIFIER Walter T. Mllis, Owensboro, Ky., assignor to General Electric Company, a corporation of New York Filed Sept. 14, 1959, Ser. No. 839,794 11 Claims. (Cl. 313-3) My invention relates t-o electron discharge devices, and more particularly to an improved electron discharge device of the rectifier type.

Rectifier tubes for receiver operation have heretofore been constructed with either directly or indirectly heated cathodes, depending on the magnitude of the voltages to be rectified thereby, as well as on other environmental factors.

Such tubes, when constructed in accordance with techniques heretofore described, are subject to destructive arc-over, especially during a critical warm-up period when the anode potential and the heater voltage are applied simultaneously.

Quick-warm-up cathodes are extremely `desirable for rectifier tube operation because (1) the probability of arc-over between cathode and anode is materially reduced according as the Warm-up period for the cathode is reduced, (2) for shorter warm-up periods, the rectifier load impedance is more `apt to be maximized in yany given circuit arrangement, especially if the rectifier reaches normal operating temperature before the other tubes in the circuit. The maximum load impedance operates to limit the current drawn during arc-over, thus minimizing injury to the rectifier cathode coating.

Directly heated cathodes in the form of filamentary members capable, when heated, of emitting copious supplies of electrons, have been used to advantage for relatively low-voltage operation because such cathodes are characterized by shorter warm-up periods, which, in turn, result from the lower thermal capacity of such cathodes. However, directly-heated cathode rectifiers cannot `satisfactorily be used for relatively high-voltage application because of the inherent mechanical limitations of such cathodes.

yFor relatively high-voltage applications, such as damper rectifiers commonly employed lin television, indirectly heated cathodes have been used yfor mechanical strength. In such rectifiers, the warm-up yperiod is commonly long as compared to that of other tubes in such circuits. Accordingly, in such tubes, the arc-over problem is appreciable and this problem is further aggravated by the fact that the peak voltages to .be rectified are very high, which, in turn, has led to the introduction of a substantial amount of high temperature insulation in the heater-cathode construction. The high-temperature insulation possesses high thermal capacity, which causes a lengthening of the warmup time. This, as noted above, operates to increase the probability of arc-over. Accordingly, -in the construction of such damper rectifiers, one has heretofore been confronted with a compromise selection of utilizing, on the one hand, a minimal amount of heater-to-cathode insulation to achieve short warm-up time, and sufficient insulation, on the other hand, to prevent high-voltage breakdown. This compromise was, at best, an unsatisfactory condition resulting as it did in manufacture of rectifiers of limited utility.

lt is, therefore, a primary obje-ct of this invention to provide an improved rectifier of the electron discharge type which is free from the above-noted difficulties.

Another object of this invention is to provide novel and improved cathode arrangements for rectifier tubes whereby a short warm-up time for such rectifiers is readily accomplished.

Still another object of this invention is to provide an improved elect-ron discharge rectifier device having novel cathode arrangements whereby such rectifier device is capable of low cathode Warm-up time under a wide variety of `operating characteristics.

`In the accomplishment of the foregoing objectives, I provide, in accordance with one aspect of my invention, a new rectifier arrangement in which the cathode is generally of the directly heated type, thereby to realize the advantage residing in the inherently low-thermal capacity thereof. However, in lieu of the coated-wire or ribbon types of directly-heated cathode, which, as discussed above, suffer inherent mechanical weakness, I provide relatively rigid, cylindrical sleeve members of novel construction through Which the heating current is directly conducted, thereby to achieved the requisite mechanical strength to overcome any tendency toward bowing, vibration, or other deformation of the cathode under the influence of high-intensity cathode-anode fields.

In accordance with another aspect of my invention, I provide a rectier device in which the cathode is in the form of a pair of tubular conductive members disposed in parallel spaced relation, each bearing an external coating of electron-emissive material, the members being interconnected at one end, the other ends of the members providing input and output terminals for applying heating current through the members, in series.

lFor a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its `scope will be pointed out in the appended claims.

FIG. 1 is a perspective view, with parts broken away, of an electron discharge tube constructed in accordance with one form of my invention.

`iFIG. 2 is a fragmentary elevational view showing a modified form of cathode construction which can be ernployed in the tube of FIG. 1.

iFlG. 3 is a fragmentary elevational View of another modified form of cathode construction according to my invention.

Referring now to the drawing, I have shown, in FIG. 1, an electron discharge device in the form of a double-diode rectifier tube 11 constructed in accordance with my invenltion. It will be understood that the features of this invention may be utilized with equal effectiveness in ysingle diode yarrangements as Well as in assemblies having any desired number of functional tube elements.

As shown, the rectifier 11 comprises a pair of diode subassemblies 13 and 15 which are of su-bstantially identical construction. Accordingly, in the following description, the elements of subassembly 13 will be described in detail, the corresponding elements of subassembly 15 being `assigned similar reference numerals with associated superscripts or prime characters. Thus, the subassemblies include -anodes or plates 17, 17' and cathodes 19, 19', mounted -in coaxial yspaced relation therefrom, the anodes and cathodes being supported within an evacuated envelope 21 between upper and lower insulative spacers or micas 23, 25.

The anodes 17, 17 can be of any suitable material for the purpose. In a successful operative embodiment, I have employed to advantage `a plural-layer material consisting of a layer of copper over which is a layer of aluminum-clad iron, as described and claimed in my copending application, S.N. 764,988, filed October 2, 1958, entitled Electron Discharge Device, and assigned to the assignee of this application.

The anode 17 is formed to provide two parallel tubular portions 27, 29, which may be conductively joined together along their adjacent side walls by an axially extending web portion 31, which, in turn, may be provided with a transversely projecting fin portion 33 of axial dimension substantially equal to those of the tubular portions 27, 29. Such fin portion 33 has been found to be desirable for dissipating relatively large quantities of heat that are generated in the anode regions between the tubular port-ions 27, 29". Projecting from the outer side walls of the tubular portions 27, 29 and in diametrally opposed, coplanar relation to the web portion 31, are additional n portions 35, 37 as required, which carry tabs 39 at top and bottom which may, in turn, pass through suitable openings in top and bottom micas 23, 25 for securing the anode therebetween and for providing a terminal to which an anode stem lead 41 may be secured as by spot welding.

The cathode 19 is formed to provide two parallel tubular portions 43, 45, which are coaxially disposed within the anode portions 27, 29, respectively, and in relatively closely spaced relation thereto. It will be appreciated that extremely small cathode-to-anode spacing can thus be realized inasmuch as the tubular construction of the cathode portions 43, 45 resists bowing, vibration, or other mechanical deformation.

The cathode portions 43, 45 are preferably of a highresistivity, high hot-strength material of the type disclosed and claimed in my U.S. Patent No. 2,878,410, patented March 17, 1959, entitled Electronic Tube Structure and assigned to the assignee of the present application. In a successful operative embodiment, a cathode material consisting of nickel-clad Inconel was used, the lnconel component being a low-thermal eX- pansion, low-thermal conductivity alloy available through the International Nickel Company, and, according to standard handbooks of metallurgy, has the following percentage composition by weight:

The tubular cathode portions 43, 45 may be formed in any suitable conventional manner to provide a smooth cylindrical surface with a lock seam, lap seam, or simple butt seam, as desired, the outer surface of the portions 43, 45 being coated, in any suitable manner, with an electron emissive material which, upon heating, provides a copious supply of electrons. The upper ends of the cathodes are passed through suitable openings in the top mica and are provided with conductive tabs 47, 49, which are bent toward each other and spot welded together to provide electrical continuity between the portions 43, 45. The lower end of cathode portion 45 carries a tab 51 to which connection may be made to a source of heater power (not shown) through a stem lead 53, while the lower end of cathode portion d3 snugly receives one leg of .a substantially U-shaped conductive connector 55, the opposite leg of which is snugly fitted into the lower end opening of tubular portion 43' of cathode 19".

Conventional getter assemblies 57 can be affixed by any suitable means to the fins.

As noted above, the subassembly is of construction generally similar to that of the subassembly 13, just described, and corresponding parts are identified with correspondingly primed reference numerals.

From the foregoing description, it will be appreciated that the cathodes of the respective diode subassemblies are adapted to be directly heated, heater current being applied serially through the tubular portions 45, `43 by means of the tabs 47, 49, thence through the connector 55 to tubular portions 43', 45 by means of the tabs 47', 49. The heater return is effected through stern lead 59 which is connected to the lower end of cathode portion 45.

FIG. 2 shows a modified construction of cathode in which the upper ends of the tubular cathode portions `61, 63 are open and instead of being provided with interconnected tabs, as .at 47, 49 (FIG. l) are adapted for interconnection by means of a low-resistance U-shaped connection 65, of which the leg portions are tightly fitted into and spot-welded or otherwise secured to the open ends of the portions 61 and 63.

In FIG. 3, I have shown still another modification wherein the tubular cathode portions 67, 69` are formed of integral tubular stock having a flattened part 71 formed therein. The tubular stock can be bent adjacent the ends of the flattened part 71 to form an inverted U-shaped part having a bight portion at part 71, which functions as the top connector for the cathodes `67, 69 without requiring .any welds or interfitting of parts.

Advantages of the above-described directly-heated cathode rectifier will thus be apparent when it is appreciated that, by the arrangements illustrated and described, I have provided a rectier capable of handling large amounts of power with relatively small cathodeto-anode spacing, inasmuch as any bowing, vibration, or other deformation of the cathode are virtually eliminated. At the same time, arc-over tendency has been minimized as a result of the directly-heated character of the cathode, which, it will be observed, is now capable of substantially increased length over that heretofore considered possible. It will be noted further that my invention completely eliminates the usual folded or other conventional heater assembly, thereby eliminating another source of arc-Over, e.g. heater-cathode shorts, as well .as a relatively costly assembly and troublesome assembling operation.

It will be appreciated by those skilled in the art that my invention may be carried out in various other ways and may take various forms and embodiments other than those illustrative embodiments heretofore described. It is to be understood, therefore, that the scope of the invention is not limited by the details of the foregoing description, but will be defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electron discharge device comprising a cathode and an anode, each comprising a pair of hollow tubular members, `the cathode members having portions of highresistivity material and coaxially disposed within respective anode members, and relatively low-resistance means interconnecting the cathode members for conducting electric current therethrough.

2. An electron discharge device comprising a cathode and an anode, each comprising a pair of hollow tubular members, said anode members being disposed in mutually spaced parallel relation, the cathode mem-bers having portions of high-resistivity material and formed in inverted U-shape, of which the leg portions are coaxially disposed within respective anode members, the bight portion of said U-shape interconnecting the cathode members in a lowresrstance path `for conducting electric current therethrough.

3. An electron discharge device comprising a cathode and an anode, each comprising a pair of tubular members, the cathode `members defining longitudinal cavities free of heat-exchanging material, said cathode members being coaxially disposed within respective anode members and comprising means providing a high-resistance path on the interior surfaces thereof and an electron-emissive coatmg on the exterior surfaces thereof, and means interconnecting the cathode members in a low-resistance path for conducting electric current therethrough.

4. An electron discharge device comprising a first cathode and a first anode, each comprising a pair of tubular members, the cores of said cathode members being empty to minimize heat loss therein, said cathode members being coaxially disposed within respective anode members, means interconnecting the first cathode members for conducting electric current therethrough, a second cathode and a second anode, each comprising a pair of tubular members, the -bores of said cathode members being empty to minimize heat loss therein, said cathode members bing coaxially disposed within respective anode members, means interconnecting the second cathode members for conducting electric current therethrough, and means serially interconnecting said iirst and said second cathode members.

5. An electron discharge device comprising a cathode and an anode, each comprising a pair of hollow tubular members, the bores of said cathode members being void of heat-loss material, said cathode members being coaxially disposed within respective anode members, and tab means at adjacent ends of said cathode members, said tab means being aixed to each other for inter-connecting thc cathode members for conducting electric current therethrough.

6. An electron dischar-ge device comprising a cathode and an anode, each comprising a pair of elongated tubular members, the cathode members detining longitudinal cavities coextensive with the lengths of said cathode members, said members being coaxially disposed within respective anode members, and U-shaped conductor means having leg portions tted into open-end portions of said cathode members Vfor interconnecting the cathode members.

7. An electron discharge rectifier, comprising an evacuated envelope, an anode, a cathode, and means supporting said anode and said cathode in said envelope, said anode comprising a pair of tubular members and means conductively connecting said members, said cathode comprising a pair of tubular members, individual ones of said cathode members being hollow and void of heat-exchanging material, said cathode members being coaxially disposed within individual ones of said anode members, and means serially interconnecting said cathode members and to a source of current.

8. A cathode assembly for an electron discharge rectifier, comprising a pair of open-ended hollow tubular members, an electron-emissive coating on the exterior surfaces of said cathode members, means defining a high-resistance path on the interior surfaces of said members, and means at one pair of adjacent open ends serially interconnecting said cathode members.

9. The assembly -as claimed in claim 8, wherein said interconnecting means comprises tabs projecting in mutually opposed directions and disposed in overlapping relation to each other, and means interconnecting said tags.

10. The assembly as claimed in claim 8, wherein said interconnecting means comprises a U-shaped conductive member having leg portions adapted to be received in said open ends of said members.

11. The `assembly as claimed in claim 8, wherein said members are integrally `formed o-f circular cross section stock with an intermediate portion of substantially fiattened cross section, said flattened portion dening a bend region interconnecting said members.

References Cited in the file of this patent UNITED STATES PATENTS 430,933 Edison June 24, 1890 1,605,735 Hough Nov. 2, 1926 2,172,207 Kolligs Sept. 5, 1939 2,181,080 Elston Nov. 21, 1939 2,244,752 Wolff June 10, 1941 2,717,975 Wihtol Sept. 13, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,048,726 August 7, 1962 Walter T. Mills s in the above numbered pat- It islhereby certified that error appear tters Patent should read es ent requiring correction and that the seid Le corrected below.

Column 4, line 71, for ",lxzoregwl read bores Signed and sealed this gy of November 1962.

(SEAL) Attest: DAVID L. LADD Commissioner of Patents Attestig Officer

Images