US2837207A - Getter structure - Google Patents

Getter structure Download PDF

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Publication number
US2837207A
US2837207A US478352A US47835254A US2837207A US 2837207 A US2837207 A US 2837207A US 478352 A US478352 A US 478352A US 47835254 A US47835254 A US 47835254A US 2837207 A US2837207 A US 2837207A
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US
United States
Prior art keywords
container
aluminum
melting point
atmosphere
barium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US478352A
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English (en)
Inventor
Ira S Solet
Robert L Waer
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RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to BE543977D priority Critical patent/BE543977A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US478352A priority patent/US2837207A/en
Priority to US478369A priority patent/US2872028A/en
Application granted granted Critical
Publication of US2837207A publication Critical patent/US2837207A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
    • H01J7/183—Composition or manufacture of getters

Definitions

  • This invention relates to an improved getter structure More particularly, the invention provides an improved getter wire having a core containing a material which exhibits gettering properties and a sheath surrounding the core and provides an improved method of making such a wire.
  • the wire made according to the method of the invention proves useful as a getter, that is, as a clean-up agent for removing residual gases within an evacuated electron discharge device.
  • the structure of the invention protects the core of the wire from an atmosphere which is chemically reactive with the material of the core.
  • the method vof making the structure includes the casting of a core material in a container.
  • Barium for example, forms barium oxide and hydrated oxides on exposure to the atmosphere.
  • An object of the invention is to provide an improved atent ICC structure comprising a container having therein an atrnospherically reactive material.
  • a further object is to provide a structure comprising an atmospherically reactive alkaline earth metal and a container shielding said metal from the atmosphere and which is free of entrapped gases.
  • a still further object of the invention is to provide an improved method of making a getter structure for use within an electron tube and wherein a core of an alkaline earth metal is encased within a sheath of aluminum without the entrapment of gases within the sheath.
  • Figure l is a flow chart of a method of making an aluminum-clad alkaline earth metal structure according to the invention.
  • Figure 2 is a liow chart showing in greater detail the steps of a method of the invention.
  • Figure 3 is a vertical cross-sectional view of a mold assembly illustrating a casting step according to the invention.
  • Figure 4 is a cross-sectional view taken on line 4-4 of the mold assembly shown in Figure l.
  • Figure 5 is a side view partly in section of a structure produced by the mold apparatus shown in Figure 3.
  • Figure 6 shows an enlarged perspective view partly in section of an aluminum sheathed barium wire made according to the method of the invention.
  • Figure l a flow chart of a method, according to the invention, which is used in making an aluminum-clad alkaline earth metal structure.
  • the material to be used for the core of the structure which includes a metal of the alkaline earth group and which may have a melting point above that of aluminum, is melted and poured into an aluminum container.
  • the aluminum container is maintained at a temperature below its melting point while the core material in the container cools.
  • the core material completely fills the space within the container by virtue of its being poured into the container; consequently, the resultant structure is substantially free of entrapped gases.
  • Figure 2 depicts an embodiment of the method illustrated in Figure l.
  • a vacuum melting furnace (not shown) may be used to melt the core material.
  • the core material used in this embodiment of the invention is composed of an alkaline earth in metal form such as barium having a purity of the order of 99 barium.
  • the core material is melted under vacuum or in an atmosphere of an inert gas at a relatively low pressure and at a temperature of above 850 C., the melting point of barium.
  • atmosphere of relatively pure argon at a pressure of about 0.2 atmosphere may be used.
  • the vCrucible used in containing the barium during the melting operation may be of a material known as Armco Iron.
  • a thermocouple gauge (not shown) may be used for the reading of relatively low pressures and a mercury manometer (not shown) may be used for reading higher pressures.
  • the melting may be accomplished by first placing the barium metal within the crucible in the chamber' of a vacuum furnace and evacuating the latter to a relatively low pressure, say 25 microns of mercury. The barium is then slowly heated until most of the resultant gas evolution ceases. The chamber is then flushed out a number of times with an inert gas such as argon to remove substantially all traces of oxygen; two flushings have proven sulicient. The pressure of argon is then adjusted to about 100 microns of mercury so as to provide a vapor pressure of argon which is at least as great as the vapor pressure of barium at its melting point to lprevent the barium from boiling off into the furnace. The temperature of the furnace is then increased to melt the barium.
  • a relatively low pressure say 25 microns of mercury.
  • the barium is then slowly heated until most of the resultant gas evolution ceases.
  • the chamber is then flushed out a number of times with an inert gas such as argon to remove substantially all
  • the heat is increased and the melt is held at an elevated temperature for about five minutes in order to degas the melt and to achieved an elevated pouring temperature.
  • the melt is then poured, in an inert atmosphere, into a mold assembly of the type shown in Figure 3; the mold assembly is then allowed to cool to room temperature in the same inert atmosphere.
  • FIG. 3 An apparatus showing the position of the core material and the aluminum sheath or container 12 within a mold assembly 14.
  • the mold assembly 14 which may comprise a copper mold support 16 closed off at the bottom thereof with a suitable metal plug 18, is relatively massive compared to the aluminum and barium material within the support.
  • a copper mold support having a length of 71A inches and a Wall thickness of one inch has been used.
  • the support may be split, as shown in Figure 4, to facilitate removal of the composite structure produced by the mold assembly. While the use of a split copper mold support is preferred, a mold support of any other material may be used having a thermal conductivity and capacity such that the temperature of the inside surface of the container 7 is maintained at a temperature below the melting point of aluminum throughout the pouring and cooling steps.
  • a funnel 20, which may be of a material such as graphite so as to reduce any alkaline earth metal oxides that may be formed, may be disposed around an opening at the top of the mold assembly as viewed in Figure 3 inorder to direct the ow of barium into the aluminum container 12.
  • the aluminum container 12 may have an inside diameter of about one-half inch and a wall thickness of the order of three sixty-fourths of an inch.
  • Figure 4 5 is a view partly in section of such a structure. The ends of the aluminum container 12 are pinched together in order to seal the core material 10 from the atmosphere.
  • the structure may be drawn down to the desired diameter by means of wire-drawing dies. Since the aluminurn container is relatively ductile any spaces formed between the outside surface of the core material and the inside surface of the aluminum container are substantially eliminated in the drawing operation by the pressure forcing the aluminum sheath against the core.
  • the Wire thus formed may then be cut into the desired lengths by means of a pinching operation so that an aluminum coating is retained around the barium'at the severed ends.
  • barium which has a melting point of about 850 C.
  • an aluminum container which has a melting point of about 660 C.
  • the method of the invention may be used in the casting of alloys containing a metalfrom. the group of alkaline earth metals.
  • a barium-aluminum alloy as a getter material for certain high temperature flash getters wherein the barium-aluminum alloy used is relatively unstablein air.
  • the barium-aluminum alloy may be cast by the method of the invention to produce an aluminum-clad bariumaluminum alloy core structure.
  • One getter material made according to the method of the inventionv has a core of an alloy of barium of 99% purity and aluminum of 99.6% purity in a ratio of 99.0 grams of barium to 1.0 gram aluminum i. e. 99% barium and 1% aluminum by weight.
  • the barium may be weighed in paraine oil and rinsed in toluene before being placed in the melting Crucible with the aluminum.
  • the melting crucible is placed in a vacuum melting furnace of the afore-described type and the vacuum chamber is evacuated to a relatively low pressure so as to remove barium reactive gases.
  • the charge is then slowly heated until the evolution of gases ceases and the chamber flushed out with argon.
  • the pressure of argon is then adjusted to about 150 millimeters of mercury and the charge quickly melted.
  • any other inert atmosphere may be used provided the gas of the inert atmosphere is not absorbed by the core material or the aluminum liner.
  • helium or neon may be used as the inert atmosphere.
  • argon is preferred for reasons of economy.
  • a vacuum maybe used; but, as mentioned before, the use of a vacuum is not preferred.
  • Figure 6 shows a portion of a wire adapted to be used as a getter material within an electron tube and which was made according to the method of the invention. While the drawing shows a sectional view of the wire for purposesy of illustrating its structure, the core material 22, which is of a material including an alkaline earth metal, is preferably completely sheathed by a coating of aluminum 24. l
  • the aluminum-clad structure made according to the method of the invention is useful as -a getter material within electron tubes, it will be appreciated that the invention is equally useful in other application where a core of a highly reactive material is desired which is substantially free of entrapped gases.
  • a structure adapted to be used as a getter within an electron discharge device comprising a sheath of a material including aluminum, and a solid core member including barium within said sheath, said core member completely lling the space within said sheath.
  • a structure adapted to be used as a getter within an electron discharge device comprising a solid core member including an alloy consisting of aluminum and at least 50% barium by weight, ⁇ and a sheath of aluminum surrounding said core member, said core member completely filling the space within said sheath.
  • a structure adapted to be used as a getter within an electron discharge device comprising a solid core member including an alloy containing barium and aluminum in the ratio of about 99% barium to about 1% aluminum by weight, and a sheath of aluminum surrounding said core member, said core member completely filling the space within said sheath.
  • a method of making aluminum-clad wire having a core material wherein the major constituent is barium comprising the operations of heating said material to a temperature below the melting point thereof and in an atmosphere at a pressure below that of the ordinary atmosphere for degassing said material, further heating said material in an atmosphere of argon at a pressure of at least 0.2 atmosphere whereby evaporation of said barium is reduced, raising the temperature of said material to pouring temperature within said atmosphere of argon, pouring said material into a mold assembly including an aluminum container and in said atmosphere of argon, said mold assembly being characterized by a thermal conductivity andcapacity sucient to maintain said container at a temperature below the melting point of aluminum, cooling said material in said atmosphere of argon to a temperature below that of the melting point of aluminum thereby forming a structure comprising an aluminum container and a solid core member of said material, removing said structure from said mold assembly, and working said structure into wire, whereby spaces formed during the cooling of said assembly, between the outside surface of said core member and the inside surface of

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US478352A 1954-12-29 1954-12-29 Getter structure Expired - Lifetime US2837207A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE543977D BE543977A (cs) 1954-12-29
US478352A US2837207A (en) 1954-12-29 1954-12-29 Getter structure
US478369A US2872028A (en) 1954-12-29 1954-12-29 Getter structure

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Application Number Priority Date Filing Date Title
US478352A US2837207A (en) 1954-12-29 1954-12-29 Getter structure

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US2837207A true US2837207A (en) 1958-06-03

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2872028A (en) * 1954-12-29 1959-02-03 Rca Corp Getter structure
US3620645A (en) * 1970-05-01 1971-11-16 Getters Spa Getter device

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1682590A (en) * 1923-03-01 1928-08-28 Ohio Brass Co Insulator pin and process of manufacturing the same
US2100257A (en) * 1936-02-08 1937-11-23 Reynolds Metals Co Composite body of magnesium and aluminum, and method of making same
US2100746A (en) * 1935-11-07 1937-11-30 Rca Corp Gettering vacuum tube
US2329317A (en) * 1941-03-19 1943-09-14 Gen Electric X Ray Corp Method of conditioning anodes
GB567291A (en) * 1942-11-18 1945-02-07 M O Valve Co Ltd Improvements in the manufacture of gettering material
US2624450A (en) * 1949-03-24 1953-01-06 Gen Electric Co Ltd Dispersed getter element and method of manufacture thereof

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1682590A (en) * 1923-03-01 1928-08-28 Ohio Brass Co Insulator pin and process of manufacturing the same
US2100746A (en) * 1935-11-07 1937-11-30 Rca Corp Gettering vacuum tube
US2100257A (en) * 1936-02-08 1937-11-23 Reynolds Metals Co Composite body of magnesium and aluminum, and method of making same
US2329317A (en) * 1941-03-19 1943-09-14 Gen Electric X Ray Corp Method of conditioning anodes
GB567291A (en) * 1942-11-18 1945-02-07 M O Valve Co Ltd Improvements in the manufacture of gettering material
US2624450A (en) * 1949-03-24 1953-01-06 Gen Electric Co Ltd Dispersed getter element and method of manufacture thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2872028A (en) * 1954-12-29 1959-02-03 Rca Corp Getter structure
US3620645A (en) * 1970-05-01 1971-11-16 Getters Spa Getter device

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BE543977A (cs)

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