US2908381A - Vacuum tube getter - Google Patents

Description

Oct. 13, 1959 B. BERNsTl-:IN 2,908,381

' VACUUMI TUBE GETTER Filed April 1e 1958 Y I NVEN TOR BERNARD BER/vsrE/N BYMMM,

ATTORNEY United States Patent O M VACUUM TUBE GErmR Bernard Bernstein, West Orange, NJ., assigner to Nuclear Corporation of America, Inc., Denville, NJ., a corporation of Delaware ApplicationApril 16, 1958, Serial No. 728,900

4 Claims. (Cl. 20G-.4)

The present invention relates to vacuum tube getters and more particularly to a highly efficient vacuum tube getter in which the metallic getter deposit may be confined Within a predetermined region.

Getters have been employed for many years in the manufacture of vacuum tubes in order to improve the vacuum within such tubes. As the frequencies at which vacuum tubes are operated increased, it became necessary to prevent the gettering material from depositing on the envelope of the tube since such deposits introduce into the circuit associated with the tube appreciable electrical leakage and also produce damage of the vacuum tube envelopes as a result of radio frequency heating of the metallic deposits on the inner surface of the envelope.

In an effort to prevent metallic gettering material from becoming deposited on the inner surface of the envelopes of high frequency vacuum tubes, there was developed a getter structure including a hollow glass cylinder having metallic end caps. The end caps have small tabs pressed out from the caps and a getter bar structureY was sus-'f pended in the glass cylinder between the tabs. The getter structure is mounted within a vacuum tube and heated by radio frequency or other suitable heating means so as to evaporate the gettering material. Vapors tend to travel in a straight line, and therefore, the vapor becomesl deposited on the inner surface of the glass cylinder while there is little tendency for the vapor to pass; out the openings in the end caps. The aforesaid getter structure is completely effective in preventing any of the gettering material from becoming deposited yon the inner surface of the vacuum tube envelope, but its eiciency is quite low since the surface area of the getter material exposed to the gases to be absorbed is less than it had been when deposited upon the envelope of the tube. Further, the small size of the openings in the end caps of the glass cylinder prevents an appreciable circulationl of the gases through the cylinder and, therefore, greatly limits the volume of gases which may contact the gettering material when it is flashed.

It is an object of the present invention to provide a getter structure having a large surface area upon which to deposit a metallic gettering material and which further provides for ready access of the gases to be absorbed to the gettering materials.

It is another object of the present invention to provide a getter structure for vacuum tubes having a large surface area upon which vaporized getter material may be deposited and having an outer surface structure which is porous so that gases to be absorbed may readily pass through the envelope and into the region of the gettering material.

Y In accordance with the present invention, there is provided a getter structure having a hollow and porous sleeve formed of a suitable material such as ber glass and filled with a thin filamentary material such asV glass wool or other non-oxidizable, wool-like material. Disposed along the axis of the sleeve or cylinder is a getter bar which may be maintained in proper relationship to 2,908,381 Patented Oct. 13, 1959 the sleeve by the glass wool in which the bar is embedded. Metallic members or ribbons extend outwardly from the bar through suitable openings in the sleeve and are secured to opposed arms of a stationary yoke. In operation, the getter bar is heated. and the gettering material supported thereby is vaporized and becomes dispersed throughout the glass wool so that an extremely large surface area of gettering material is provided. The porous sleeve is of'such a porosity that during subsequent ashing of the getter material, the` gases to be absorbed may pass through the porous sleeve and also through the openingsy in the ends of the porous sleeve into its interior and through the glass wool material where the gases contact the gettering material.

The glass wool provides a large surface on which `th gettering material may become deposited when it is vaporized and this .in conjunction with the porous sleeve pre'- vents any of the gettering material from escaping from the sleeve and becoming deposited upon the interior surface of the envelope of the vacuum tube. The glass Wool material should have a suicient density to prevent an appreciable amount of the gettering material from becoming deposited on the inner surface of the porous sleeve, since this might close the passages through the sleeve and materially reduce the eiiciency of the structure.

It is, therefore, another object of the present invention to provide a getter structure having a line, lamentary material upon which getterng material may be deposited and having a porous sleeve or enclosure for physically confining the lamentary material while permittinggases to pass therethrough into they region of the lamentary material.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailedV description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

Figure l is a schematic vertical diagram of an electron tube including the getter structure of the present invention;

Figure 2 is a longitudinal cross-section of the getter structure of the present invention; and

FigureY 3 is an endv viewgof the getter structure of the present invention. v v

Referring specically to Figure l of the accompanying drawings, there is provided a vacuum tube having an envelope 1 and a base 2. The tube is further provided with a press 3 for supporting mounting rods 4 and 6. The rods 4 and 6 extend upwardly from the press 3 and are adapted to support the active elements of the tube disposed within an anode structure 7, also supported on the rods 4 and 6.

A leg member 8 of a yoke 9 is secured, as by Welding or other suitable means, to one of the rods, such as the rod 6, and supported between arms of the yoke 9 is the getter structure of the present invention which is generally designated by the reference numeral 11.

Referring now specifically to Figures 2 and 3 of the accompanying drawings, the getter structure 11 comprises a hollow generally cylindrical envelope 12 fabricated from porous material such as ber glass. The two ends of the envelope 12 are provided with generally circular apertures 13 and the interior of the envelope is substantially filled with a non-oxidizable, fine, lamentary material 14, sfuch as glass wool. Positioned approximately along the axis of the porous envelope 13 is a conventional getter bar 16 which has secured at its opposite ends metallic supporting arms 17 and 18, respectively. The arms 17 and 18 extend outwardly through the apertures 13 and are secured as by brazing to the arms of the support yoke 9, as illustrated in Figure l of the accompanying drawings. The envelope 12 is maintained in a xed position'with respect to the" getter bar 16 by the mass of I iilamentary material 14. YThe getter bar A16, which is a commercially available structure, is provided with a suitable gettering material such as magnesium, tantalum, -aljuminum and barium and mixtures of barium and alu- IninurrnY The Vgettering material may be deposited in a 'cup supported by the bar 16 or in the type of bar illustrated in the accompanying drawings may constitute a coating 19 deposited on the bar.

In operation the getter is heated to vaporization temperaturerandthe vapor distributed throughout the glass wool 14 disposed within the envelope 12. Heating of the getter-ing material may be eected by a number of well known methods; for instance, subjecting the tube t 'a `radio frequency magnetic ield which induces current 'in a circuit constituting the bar 16, the support arms 17 and 18 and the yoke 9.' The glass wool 14 and the porous envelope 12 combine to prevent the vaporized getter- 1ing material from escaping to the inner walls of the en- 5 velope 1 and, therefore, prevent subsequent malfunction- 4ing of the tube due to high frequency leakage and heating. When gettering action is desired in addition to that provided during the -period that the material is in the vapor state, the gettering material may be flashed and due to thelarge surface area of' the glass wool 14 and the porosity of the sleeve 12, the gettering action is extremely eficient Specifically, the glass wool 14 provides a very large surface area for the vaporized gettering material and, therefore, subsequently provides a llarge surface area of Contact between the gettering material and the gases during flashing. Further, the eciency of the getter is enhanced due to the porosity of the envelope 12 which permits ready ow Yof Vthe gases through the porous envelope into the region' of the glass wool. Since glass wool is a relatively porous material is presents no impediment of ow of the gas therethrough and contact with the multiple surfaces provided thereby. The very large surface area of the glass wool not only increases the chemical reaction rate between the gas and the gettering material when the latter is flashed, but it also greatly increases the subsequent absorption of gases by the gettering material during the eiective life of the' tube. The outer porous sleeve as indicated above, confines the gettering material, during vaporization, to the region of the glass lwool, permits gas to enter the region of the wool and confines the getter flash within itself.

In the structure described above, the getter bar 16 supports the remainder of the getter structure since it is embedded in the lamentary material 14, which in itself has suicient strength to maintain a given shape and, therefore, acts as a support for the sleeve 12. However, if desired, spoked end supports for the sleeve 12 may be 5 secured to the supporting arms 17 and 18. The spokes would not materially reduce the flow of gases through the ends of the sleeve since they take up little of the total space across the opening.

The invention hasnbeen described as employing a po- Vroils 'slee'v'e'substantially filled with a tilamentarymaterial. The Yiilamentary'material is relatively self-supporting or at least tends to maintain a given shape and, therefore, the sleeve 12 may be completely open ended. Such a structure permits a ready llow of air from end to end 15 through the cylinder and, `therefore, it is not absolutely essential that the sleeve 12 be porous. The utilization of a non-porous sleeve will produce a distinct reduction in the efliciency of the structure, but'the efficiency of such a structure is still greater than that provided by the aforesaid prior art apparatus.

Y While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the general arrangement and of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

l. A getter structure comprising a porous, hollow cylinder, a body of lamentary material disposed in said cyl-A nder, a bar disposed approximately along the axis of said cylinder and embedded in said body of lilamentary material, and a quantity of gettering material supported by said bar, said gettering material being in the form of a coating on said bar.

2. A getter structure as defined in claim l wherein said cylinder is of fiber glass material.

, v3. A getter structure as defined in claim l wherein said cylinder is provided with an opening at each end.

4. `A getter structure as dened in claim 3, wherein two arms are provided which support said bar and extend outwardly through said openings.

References Cited in the le of this patent UNITED STATES PATENTS

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