US2162489A - Lead wire construction - Google Patents

Description

June 13, 1939. K MATTHlES E;- AL 2,162,489

LEAD WIRE CONSTRUCTION Filed March 9, 1938 Fig.

WlTNESSESI INVENTOR s h ies and aiented June 13, 193

Schaft, Siem ll a dt, Berlin-Friedemann, Ge

assignors to Siemens & l. near ,v

corporation of Ge ke, Aktie lin, Gc a application ch 9, resa serian No. isaaoo ma@ may s, 19st The invention relates to sealing-in wires and especially sealing-in wires for discharge tubes.

operating on short and ultra-short waves.

An object of the invention is to provide a sealing-in'wire that will not have the high losses of magnetic material when used with short waves and on the other hand will have an expansion i coefficient suitable for sealing with the glass casing or the glass utilized as vacuum-tight sealing mate- 'iial around the wire with casings of other mate- Other objects and advantages of the invention will be apparent from the following description and drawing, in which:

Figure 1 is a cross-section through the press of a discharge tube illustrating the preferred embodiment of the invention; and

Fig. 2 is an elevation with parts in cross-section of a press of a discharge tube illustrating another 2@ modification of the invention.

The sealing-in wires for discharge tubes are usually made of certain materials, such as, for instance, alloys of iron or chromium, which are magnetic and which cannot be used, therefore, in

the case of tubes that operate on short and ultrashort electric waves, because in this case their use would involve high losses. On the other hand, non-magnetic materials, such as copper, which have been proposed for the purpose just men- 39 tioned have the disadvantage that their expansion coefficients differ too much from the expansion coeilicient of glass, so that if sealing-in leads in the form of wires or rods made of such a material are used, diiculties will be encountered when the 35 seals are made, while afterwards the seals may start to leak.

The present invention covers an alloy whose expansion coeicient is about equal to the expansion coefficients of the ordinary commercial grades 40 of glass, while on the other hand the alloy is practically non-magnetic. In line with the invention, .erjsealing-in wire for short-Wave discharge tubes is made of a material obtained by alloying iron or nickel either with tantalum, or with columbium 45 (also called niobium) or with tantalum and columbium, the iron or nickel content, or the content of iro'n and nickel in combination, being not higher than It has been found that the expansion of an alloy of this kind is such that the 50 alloy is a very suitable material to be sealed in by fusing in ordinary commercial grades of glass. The alloy should contain a smaller or larger amount of nickel or iron, depending on the grade of glass. This content of iron or nickel should 55 not exceed 30% in order to obtain a material hav- (Ul. 25d-27.5)

ing non-magnetic properties. It has been found that a content of 1li-20% Ynickel is especially advantageous for ordinary grades of soft glass, because in this case the expansion coeicient of the metal is most closely equal to that of the glass. 5 But the content of iron or nickel, in percent, should never be less than 5%.

In those cases where it should not be possible to make the expansion coemcient of, the metal .j exactly equal tol that of a given grade of glass by 10 properly choosing the iron ornickel content, it may be advisable Vto use a sealing-inwire in the form of a rod-shaped core onto which has been shoved a tube-shaped sheath having a length corresponding to that of the fused seal. The ends l5 of this sheath must be joined to the core, for instance, by soldering or by welding; this will produce proper seals at these ends. The sheath should be so thin that after being fused-in it can yield under the influences of the stresses set up in 20 the glass, while on the other hand the core inside the sheath can contract freely without endanger.- ing the permanent tightness of the seal. 1

' If the sealed-in lead should be called uponcto carry, in addition to a high-'frequency currenta 25 strong current of normal frequency 50 or 60 cycles say, it would be advisable to use a lead in the form of a tube made of an alloy covered by this invenf tion into which has been shoved a core of copper. t An example of such a lead-arrangement is repre- 30 sented in Fig. 1 on the drawing. Here the tube made of non-magnetic alloy described in this specication is designated by l, and the copper core by 2. Air-tight joints between these two parts can be made in any suitable manner. The use of this copper core offers the advantage that a highly conductive lead is obtained, a point of great importance if the lead must carry heavy currents, While the tube-shaped sheath of the lead, which is made of an alloy covered by this 40 invention, is very well suitable for sealing-in purposes insofar as the expansive properties of the material are concerned.

The construction in Fig. 2 makes it possible to use any non-magnetic material, and especially for sealing-in leads in the form of rods for highfrequency tubes. In line wtih the present invention, a sealing-in lead for electric discharge Vessels, and especially for discharge vessels that must operate at high frequencies, consists of a tube-shaped outer part into which has been shoved with some clearance a rod-shaped or tubeshaped core, whereupon the clearance space between core and sheath has been closed by soldering the ends of the latter to the core. The effect which application of the method covered by this invention will have will be better understood if reference is made to the drawing. It shows the stem Il ofatubeinto whichapluralityofleads havebeensealedbyfusion. Rachoftheseleads conaistsofacoreliofwirewhichissurroimded by a tube-shaped sheath I8 over the entire lenzth of the lead that is fused into the Klass. The external diameter of the rod-I2 and the internaldiameter of thesheath i3 have been so chosen that the sheath can be shoved onto the rod without ditlicultm 'Ihe clearance space the one end by means of'solder Il other end by means of solder Il. 'nais double seal is very reliable for the solder will be drawn into the clearance space between the bodies i2 and I I. due to the "slit-effect, and for this reason the opening wm be nnen up m quite sausfactory manner. At the same time the little tube I3 willbe supported by therod l! at the soldered Joints.

deformed. This is an advantaae not shared by other known methodsot sealing in leads by fusion, because in the latter cases there is from thebeginninganair-sapbetweenthecoreand the sheath surrounding the core. If then, after thesealhasbeenmade,therodcoolso,the leadwill contraetmorestronglythanthealass,

if it is yassumed thatcopper is being means that it the lead should have videdintheformofa solidrod,stresses ismade,butthisclearancespaceisnotatall objectionable.

All diiiiculties encountered as aJconsequence of the diilerenee between the expansion eoeilicients of-themetal andtheglasswillbe eliminatedby ,wplyinsthemethodcoveredbythepresentinvention. Therefore. in makingsuch seals. tbe metalpartstobefusedintothellasscanbemade of-a material choaen/ velyonthe'basiaof 1u conductivity and of 1th mnesmntom. nom thisviewpoint, averysuitable material is copper. roritisknownthac hummm-trot adhering very tiahtlytozlasa.

AConcerningthe choiceofthe thickness-ratio of rod and sheath, the statement can be made that :ummmfoundtobeaclvwntureousimmune,`

inventionV may have many applications besides` the particular use illustrated. No limitations are accordingly intended on the following claims except as are necessitated by the prior art.

We claim as our invention:

l.A sealing-in wire for tubes formed fromva sheathofanalloyofb to 30% from theiron group and the remainder from the sroup consisting of tantalum anzi columbium and'a conductive core for said sheath. Y

2.Asealininwireiortubiormedtroma sheathofanalloyofimtom fromtheiron a'roup and the remainder from the Iroup consistingoftantalum andeolumbium andra conductivecoreofcopperforaaidsheath.

.8.Asealing-inwirefortubformedi'roman alloyoiwhichim tow'isametalselected fromthegroupconaistingofironandnickeland .the remainder is from the zroup consisting of KURT m'rrams. mmm' GANswmn'r.-

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