US1915863A - Grid lead-in construction - Google Patents

Description

June 27, 1933. 1 E MOURQM'TSEFF 1,915,863

GRID LEAD-IY CONSTRUCTION Filed NOV. 2, 1927 mgl.

INVENTOR Illa E/Waz/ramseff Z,

'ATTORNEY Patented June 27, 1933 UNITED STATES ILIA E. MOUROMTSEFF AND GREGORY V. RYLSKY, OF WLKINSBURG,

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ASSIGNORS TO WESTNGl-OUSE ELECTRIC AND MANUFACTURING COMPANY, A

CORPORATION OF PENNSYLVANIA GRID LEAD-IN CONSTRUCTION @ur invent-ion relates to space-current devices and particularly to devices of that character adapted for short-wave radio service.

One of the. objects of our invention is to tti provide a construction for the in-leading wires to the control electrode or grid of a short-wave radio tube.

Another object of our invention is to provide a means for feeding current uniformly l' to all parts of the control electrode of a radio tube.

Another object of our invention isA to provide a structure which' shall distribute, as uniformly as possible, the high-frequency iii electric and magnetic fields due to currents in the grid circuit of a short-wave radio tube.

A further object of our invention is to provide a .method for sealing in the conductors leading to the grid of a radio tube withf out oxidizing the parts within the tube during such sealingoperation.

Other objects of our invention will become apparent through reading the following specification, taken in connection with "T the accompanying drawing, wherein Figure 1 is a mid section of a portion of a radio tube embodying our invention and Fig. 2 is a detail view showing the conj struction of 'he in-leading wire at the time 53 it is ready to be sealed into the tube.

In radio tubes, at the frequencies now commonly used in broadcasting, the current in the in-leading wire to the control electrode is usually of small magnitude, since it is merely the charging current for that electrode. However, the magnitude of such a charging current increases with the frequency of the current being employed and, in tubes designed for so-called short-wave service, this charging current becomes of considerable magnitude. This is particularly true in tubes of the larger sizes which are used as transmitters in broadcasting.

r As a result of the increase in charging current, a problem arises in the way of providing an in-leading conductor which shall be capable of transmitting such a current to the control electrode. The grid lead structure of tubes that operated satisfactorily on 750 lilocycles became red and white Application led November 2, 1927. Serial No. 230,572.

hot and in danger of breaking at any moment when the tubes were operated at 6000 liilocycles and above. ln the case of many tubes, the requirements of electrical insulationniake it necessary that the iii-leading wire shall pass through the tube wall at some distance from the control electrode itself.

@ne preferred form of supporting structure for the control electrodes of transmitting tubes consists of a reentrant stem projecting into the tube from one end and consisting of a projection from `the press which contains the in-leading wires for the cathode. On such a reentrant-stem is mounted a metallic collar which may be clamped thereto and from which the wires supporting lthe control electrode project. ln thecase of the very high-frequency currents employed in short-wave work, it is necessary to make provision that the current shall be distributed as uniformly as possible `among the four support-stays of the control electrode.

In accordance with our invention, 'accordingly, we provide that the in-leading wires transmitting current to the control electrode shall connect to the collar at points diametrically opposite to each other.

Referring to the drawing, Fig. 1 is a view partly in section, showing the glass wall portion 1 of `a high-power transmitter tube.

art of the wall portion of this tube consistsof a meta-l anode Q, the active portions of the grid 15 and cathode 16 being within the anode. .The portion l has a reentrant stem 3, on which the collar 4, supporting the grid on projecting rods 5, is clamped.V In leading wires 17 pass through a press near the middle of the stern 3 and project into the anode 2 to support the cathode therein. Such a method of construction is well known and needs no extended description.

The lead 6 to conduct current through the tube wall to the grid is preferably sealed through the former at a point near the endof the tube. In accordance with our in vention, we provide a pair of'conductors 7 of ribbon form which are welded to diametrically opposite points on the collar 4 and curve downward and `toward each otherso that' they may be connected to the lead 6 which is located near the end of the tube and at a point on the circumference 90o displaced from each of these points of connection to the grid.

5 The double curvature of thek ribbonleads make them flexible and yielding to stresses longitudinal therein due to thermal expansion and thereby relieves the lead 6 from stress. We have found that a convenient 1G method for connecting the lead 6 to the ribbons 7 is to weld to the latter a member 9, shown most clearly in Fig. 2, which may be of copper and which is provided with a threaded hole. One convenient way of attaching ribbons 7 to member 9 is to make the latter in the form of a hollow bolt which may b-e passed through holes in ribbons 7. A nut 11 may then be screwed down binding mem- *bers 7 and 9 together. VThe two ribbons on 2G the clamp l form a triangular structure that is very rigid in respect to th-e twisting action of the nut 11 while it is being attached thereto. The connection between the two may n T then be rendered additionally secure by welding them together.

The containing vessel 1 may be of any suitable vitreous material, but the one which we prefer to use is a glass known to the trade n"`as G702P glass. The properties of this glass are such that it will make a vacuumtight seal with conductors of tungsten or molybdenum. If the iii-leading wire 6 is made of molybdenum its end may be readily 9:' threaded to engage the threaded portion of N the member 9. In case, however, a tungsten in-leading wire is used, diiiiculty will be found in threading its end.

We have found that a tungsten lead may By whatever method the threaded portionV is provided on the in-leading wire, the'latter may be sealed into the tube by the following method. The anode 2 is first sealed to the outer glass wall-portion 1. A hole with a raised rim 13 is blown at the desired location inthe wall. The stem 3 is then constructed and the cathode filament mounted thereon. W' The ribbon members 7 are affixed to the d" threaded member 9`in such vposition as to form substantially a letter V diverging therefrom. The ends are then flexed toward each other and welded to diametrically opp posite points on the collar 4. The resulting @d structure isrthen cleansed of any adherent oxides by heating it in a hydrogen atmosphere or by any other well-known method and clamped in position on stem 3. Jg, The tungsten in-leading wire 6, having the GE' threaded portion formed thereon, is providbe provided with a threaded portion by weld-V ed with a flange or collar 14 of glass of proper diameter and location to seal to the rim 13. This wire is then freed from any oxide produced by the glass blowers fires, by dipping it in sodium nitrite, for example. The stem 3 with the'cathode and grid electrodes mounted thereon as already described is sealed into container 1, with the threaded hole j in member 9 alined Ywith the hole in the rim 13 of the tube wall. The tungsten lead 6 is then inserted through the latter and screwed firmly into 'position in the threaded member 9. A seal vmay then be readily made by the in diameter and 3 centimeters long. The flexible ribbons 7 which are Welded to this collar il, consistof molybdenum ribbon 0.025 cms.r thick by 0.75 cms. wide and kapproximately 8 cms. long. Adjacent ends of these ribbons are welded to a molybdenummember 9, shown in detail in Fig. 2, which is 1.1 cms. long by 1.2 cms. in its largest diameter. The

As a specific example,r

tworibbons 7 form the sides of this V and diverge at an angle of 60'degrees. These ribbons substantially follow the cuive of a cylindrical surface that would be tangent to the face ofthe nut 11 and would extend 90 around the stem 3 to intersect with the face of the clamp 4. The particular advantage of this shape is that elongation due to heating byhigh-frequency currents will increase the radius of curvature without strain on the connection to the lead 6.

The iii-leading wire 6 is of tungsten 5.5 cms'. long by 0.3 cms. in diameter. To one end of this is butt welded a molybdenum wire 12 of the same diameter about 1.3 cms. long. This is threaded to fit a threaded hole in the molybdenum member 9. The details of construction will be readily apparent from It will thus be seen that we have provided a construction for leading current into the support collar for a control electrode which permits an'easy installation in thetube and which provides for a uniform distribution of the current to the control electrode. In accordance with the patent statutes, we have shown and described one embodiment of our invention, butV various modifications thereof will be apparent to those skilled in the art without departingfrom the principles which we have disclosed. Ve desire, therefore, that the appended claims shall be limited only by their express terms and in accordance with the prior art.

We claim as our invention:

l. An electrical-discharge device for high frequency comprising a container enclosing a plurality of electrodes, an electrode assem- -lar for supporting it upon said stem, a conductor having a threaded portion sealed through the Wall of said container, flexible ribbon conductors diverging from said conductor and engaging said threaded portion for connecting it to points spaced diametrically opposite on said electrode.

3. An electrical-discharge device for high frequency comprising a container having a reentrant stem, one of said electrodes having a collar for supporting it upon said stem, a tungsten conductor sealed through the Wall of said stem, and having an end portion comprising a different metal, a threaded portion upon said end portion and flexible ribbon conductors diverging from said conductor engaging said threaded portion and connecting it to diametrically opposite points on said collar.

In testimony whereof, vve have hereunto` subscribed our names this 7th day of October,

ILIA E. MOUROMTSEFF. GREGORY V. RYLSKY.

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