US2881104A - Methods of producing refractory metal filaments of flattened zig-zag form - Google Patents

Methods of producing refractory metal filaments of flattened zig-zag form Download PDF

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US2881104A
US2881104A US576510A US57651055A US2881104A US 2881104 A US2881104 A US 2881104A US 576510 A US576510 A US 576510A US 57651055 A US57651055 A US 57651055A US 2881104 A US2881104 A US 2881104A
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spiral
zig
flattened
refractory metal
ductile
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US576510A
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Jones David John
Gossling Brian Stephen
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General Electric Co PLC
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General Electric Co PLC
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/08—Manufacture of heaters for indirectly-heated cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K3/00—Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof
    • H01K3/02—Manufacture of incandescent bodies

Definitions

  • This invention relates to a method of producing filaments of refractory metal in the form of a flattened zig-zag.
  • the invention relates to the preparation of such filaments of relatively small dimensions that is to say dimensions such that if a zig-zag were made in known manner on a jig, the jig would be inconveniently small.
  • a method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprises the steps of associating a filamentary spiral of said refractory metal with at least one ductile metal in a relatively compact structure pressing said structure into a substantially flattened shape, thus causing said ductile metal or metals to flow in contact with said spiral and thereafter chemically removing the ductile metallic material.
  • a method of making a filament of refractory material in the form of a substantially flattened zig-zag comprises the steps of placing a filamentary spiral of refractory metal upon a relatively ductile metallic mandrel so as to form a relatively compact structure pressing said structure so as to flatten it to a desired extent, chemically removing the ductile metal and thereafter heat treating the flattened filament so as to set it.
  • said pressing may take place at a temperature between 200 C. and 400 C. so that said refractory metal becomes relatively ductile.
  • Either or both the spiral or ductile metal or metals may be heated before or during the pressing process so as to remove residual stresses.
  • silica tungsten wire of diameter 0.125 mm. is wound on a tungsten wire mandrel of diameter 0.63 mm. to form a spiral having a pitch of 0.605 mm., the overall length of the spiral thus formed being 8 mm.
  • the spiral is then removed from the tungsten mandrel and placed on an annealed cooper wire mandrel of diameter 0.604 mm.
  • the spiral and the copper mandrel are then pressed between two plain hardened steel plates at a pressure of the order of five tons per sq. inch so as to cause the copper to flow in contact with the spiral which is thus flattened to the required extent.
  • the flattened spiral and mandrel compact is then dipped in nitric acid so as to remove the copper and leave a flattened zig-zag filament of silica tungsten having an overall length of 9.5 mm. and a width of 1.4 mm.
  • the flattened filament is then furnaced in a hydrogen atmosphere at a temperature of about 1400 C. for ten minutes. This serves to set the filament in its flattened zig-zag shape.
  • the spiral having been placed on the mandrel is plated with copper to a depth of 0.5 mm. This is to ensure the rigid disposition of the spiral on the mandrel.
  • the spiral itself may be plated with copper to a suitable depth and then flattened without the necessity of placing the spiral on a mandrel.
  • the filament is plated with copper to a suitable depth before being wound into a spiral.
  • the spiral and the mandrel are annealed either separately or together either before or during the pressing, thus all residual stresses are removed from the materials.
  • the pressing takes place at a temperature such that the silica tungsten filament becomes relatively ductile, a suitable temperature being one of the order of 300 C.
  • a zig-zag silica tungsten filament prepared in accordance with the invention is particularly useful as an elec tron source in an electric discharge device such as for example, an X-ray tube or cathode ray tube.
  • Such an electron source is capable of providing a very uniform electron distribution which is hence relatively simple to control.
  • Figure l is a view of the filament
  • Figure 2 is a view, partly cut away to show internal details, of the X-ray tube.
  • the X-ray tube comprises a sealed evacuated glass envelope 1 in which is mounted an electrode structure.
  • the electrode structure includes a cathode constituted by a silica tungsten filament 2 of flattened zig-zag form produced in accordance with the invention; the filament 2 (which is shown in detail in Figure 1) is disposed within a groove formed in a machined nickel cathode head 3, the filament 2 being disposed parallel to and slightly recessed from the face of the head 3 opposite a copper anode 4.
  • a tungsten face 5 is formed upon the operating surface of the anode 4 and serves as a target.
  • a window 6 is formed in the envelope 1 between the cathode and the target, the window 6 being constituted by a reduced thickness of the glass envelope.
  • a method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps of placing a filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape in which the spiral of refractory metal is flattened into zig-zag shape, thus causing said ductile metal or metals to flow in contact with said spiral and thereafter chemically removing the ductile metallic material.
  • a method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps. of disposing a filamentary spiral of refractory metal around andin intimate contact with a relatively ductile metallic mandrel so as to form a relatively compact structure in which said spiral is supported by said ductile metal, pressing said structure so as to flatten it to an IBXtCl'lll such that the spiral of refractory metal is flattened into zig-zag shape, chemically removing the ductile metal and thereafter heat treating the flattened filament so as to set it.
  • a method of making a filament of refractory metal in the form of substantially flattened zig-zag comprising the steps of placing an open-wound filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantiallyfiattened shape in which the spiral of refractory metal is flattened into zig-zag shape, thus causing said ductile metal or metals to flow in contact with said spiral, and thereafter chemically removing the ductile metallic material.
  • a method of making .a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps or placing a filamentary spiral of said refractory metal ,in intimate contact withat least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape without restraining transverse flow thereof under pressure so that the ductile metal and spiral will spread in a direction transverse to the length of the spiral, thereby flattening the spiral into a zig-zag shape, thus causing said ductile metal or metals to fiow in con tact with said spiral, and'thereafter chemically removing the ductile metallic material.
  • a method of making a filament of refractory metal in'the form of a substantially flattened zig-zag comprising the steps of placing a filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape without restraining longitudinal or transverse .flow thereof under pressure so that the ductile metal and spiral will spread parallel and transverse to the length of the spiral, thus causing said ductile metal or metas to flow in contact with said spiral, and thereafter chemically removing the ductile metallic material.

Description

Apnl 7, 1959 D. J. JONES ET AL 2,
METHODS OF PRODUCING REFRACTORY METAL FILAMENTS 1 OF FLATTENED ZIG-ZAG FORM Filed Dec. 5, 1955 Fig.1
-v NToRS Dqvll) n/ wv JONES United States Patent 9 METHODS OF PRODUCING REFRACTORY METAL FILANIENTS OF FLATTENED ZIG-ZAG FORM David John Jones, Harrow, and Brian Stephen Gossling, Richmond, England, assignors to The General Electric Company Limited, London, England Application December 5, 1955, Serial No. 576,510
Claims priority, application Great Britain December 3, 1954 15 Claims. (Cl. 148-4) This invention relates to a method of producing filaments of refractory metal in the form of a flattened zig-zag.
In particular, the invention relates to the preparation of such filaments of relatively small dimensions that is to say dimensions such that if a zig-zag were made in known manner on a jig, the jig would be inconveniently small.
It is an object of this invention to produce a simple and effective method of producing such filaments.
According to this invention a method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprises the steps of associating a filamentary spiral of said refractory metal with at least one ductile metal in a relatively compact structure pressing said structure into a substantially flattened shape, thus causing said ductile metal or metals to flow in contact with said spiral and thereafter chemically removing the ductile metallic material.
According to one aspect of this invention, a method of making a filament of refractory material in the form of a substantially flattened zig-zag comprises the steps of placing a filamentary spiral of refractory metal upon a relatively ductile metallic mandrel so as to form a relatively compact structure pressing said structure so as to flatten it to a desired extent, chemically removing the ductile metal and thereafter heat treating the flattened filament so as to set it.
According to alternative features of the present invention said pressing may take place at a temperature between 200 C. and 400 C. so that said refractory metal becomes relatively ductile. Either or both the spiral or ductile metal or metals may be heated before or during the pressing process so as to remove residual stresses.
One arrangement in accordance with the present invention will now be described by way of example with reference to a method of producing a filament of refractory metal in the form of a flattened zig-zag suitable for use as an electron source in an electron discharge device.
In this arrangement silica tungsten wire of diameter 0.125 mm. is wound on a tungsten wire mandrel of diameter 0.63 mm. to form a spiral having a pitch of 0.605 mm., the overall length of the spiral thus formed being 8 mm. The spiral is then removed from the tungsten mandrel and placed on an annealed cooper wire mandrel of diameter 0.604 mm. The spiral and the copper mandrel are then pressed between two plain hardened steel plates at a pressure of the order of five tons per sq. inch so as to cause the copper to flow in contact with the spiral which is thus flattened to the required extent. The flattened spiral and mandrel compact is then dipped in nitric acid so as to remove the copper and leave a flattened zig-zag filament of silica tungsten having an overall length of 9.5 mm. and a width of 1.4 mm. The flattened filament is then furnaced in a hydrogen atmosphere at a temperature of about 1400 C. for ten minutes. This serves to set the filament in its flattened zig-zag shape.
In an alternative arrangement the spiral having been placed on the mandrel is plated with copper to a depth of 0.5 mm. This is to ensure the rigid disposition of the spiral on the mandrel. Alternatively the spiral itself may be plated with copper to a suitable depth and then flattened without the necessity of placing the spiral on a mandrel. In another arrangement the filament is plated with copper to a suitable depth before being wound into a spiral. In further arrangements the spiral and the mandrel are annealed either separately or together either before or during the pressing, thus all residual stresses are removed from the materials. In still further arrangements the pressing takes place at a temperature such that the silica tungsten filament becomes relatively ductile, a suitable temperature being one of the order of 300 C.
A zig-zag silica tungsten filament prepared in accordance with the invention is particularly useful as an elec tron source in an electric discharge device such as for example, an X-ray tube or cathode ray tube. Such an electron source is capable of providing a very uniform electron distribution which is hence relatively simple to control.
One particular arrangement of an X-ray tube wherein an electron source is constituted by a zig-zag silica tungsten filament prepared in accordance with the invention will now be described with reference to the accompanying drawings, in which:
Figure l is a view of the filament; and
Figure 2 is a view, partly cut away to show internal details, of the X-ray tube.
Referring to Figure 2, the X-ray tube comprises a sealed evacuated glass envelope 1 in which is mounted an electrode structure. The electrode structure includes a cathode constituted by a silica tungsten filament 2 of flattened zig-zag form produced in accordance with the invention; the filament 2 (which is shown in detail in Figure 1) is disposed within a groove formed in a machined nickel cathode head 3, the filament 2 being disposed parallel to and slightly recessed from the face of the head 3 opposite a copper anode 4. A tungsten face 5 is formed upon the operating surface of the anode 4 and serves as a target. A window 6 is formed in the envelope 1 between the cathode and the target, the window 6 being constituted by a reduced thickness of the glass envelope.
In such an X-ray tube the useof such an electron source ensures the provision of one maximum in intensity at the focal spot in the transverse direction as opposed to two maxima from a conventional spiral filament and furthermore renders possible the production of a very fine focal spot.
It will be appreciated that whilst in the above arrangements silica tungsten and copper have been used as the refractory and relatively ductile metals respectively, other metallic materials possessing the same properties may also be used.
We claim:
1. A method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps of placing a filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape in which the spiral of refractory metal is flattened into zig-zag shape, thus causing said ductile metal or metals to flow in contact with said spiral and thereafter chemically removing the ductile metallic material.
2. A method of making a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps. of disposing a filamentary spiral of refractory metal around andin intimate contact with a relatively ductile metallic mandrel so as to form a relatively compact structure in which said spiral is supported by said ductile metal, pressing said structure so as to flatten it to an IBXtCl'lll such that the spiral of refractory metal is flattened into zig-zag shape, chemically removing the ductile metal and thereafter heat treating the flattened filament so as to set it.
3. A method of making a filament accordingto claim 1 in-which said pressing takes place at a temperature between 200 C. ,and 400 C. so that said refractory metal becomesrelatively ductile.
4. A method of making a filament according to claim 1 in which the spiral is heat treated before the pressing process so as to remove residual stresses.
5. A method of making a filament according to claim 1 in which said filament is plated with ductile metal before pressing.
6. A method of making a filament according to claim 1 in which said filament is formed of tungsten wire.
7. A method of making a filament according to claim 1 in which said ductile metal is copper.
8. A method of making a filament according to claim 1 in which the spiral is heat treated during the pressing process so as to remove residual stresses.
9. A method of making a filament according to claim 1 in which the ductile metal is heat treated before the pressing process so as to remove residual stresses.
10. A method of making a filament according to claim 1 in which the spiral and ductile metal are heat treated before the pressing process so as to remove residual stresses.
11. A method ofmaking a filament according to claim 1 in which the spiral and the ductile metal are heat treated during the pressing process so as to remove residual stresses.
12. A method of making a filament of refractory metal in the form of substantially flattened zig-zag comprising the steps of placing an open-wound filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantiallyfiattened shape in which the spiral of refractory metal is flattened into zig-zag shape, thus causing said ductile metal or metals to flow in contact with said spiral, and thereafter chemically removing the ductile metallic material.
13. A method of making a filament or refractory metal in the form of a substantially flattened zig-zag comprising the steps of placing a filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as=to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattenedshap'e without restraining longitudinal flow thereof under .pressureso that the ductile metal and spiral will spread in the direction of the length of the spiral, thereby flattening the spiral into a zig-zag. shape, thus causing said ductile metal or metals to flow in contact with said spiral, and thereafter chemically removing the ductile metallic material.
14. A method of making .a filament of refractory metal in the form of a substantially flattened zig-zag comprising the steps or placing a filamentary spiral of said refractory metal ,in intimate contact withat least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape without restraining transverse flow thereof under pressure so that the ductile metal and spiral will spread in a direction transverse to the length of the spiral, thereby flattening the spiral into a zig-zag shape, thus causing said ductile metal or metals to fiow in con tact with said spiral, and'thereafter chemically removing the ductile metallic material.
15. A method of making a filament of refractory metal in'the form of a substantially flattened zig-zag comprising the steps of placing a filamentary spiral of said refractory metal in intimate contact with at least one ductile metal so as to form a relatively compact structure, in which said spiral is supported by said ductile metal, pressing said structure into a substantially flattened shape without restraining longitudinal or transverse .flow thereof under pressure so that the ductile metal and spiral will spread parallel and transverse to the length of the spiral, thus causing said ductile metal or metas to flow in contact with said spiral, and thereafter chemically removing the ductile metallic material.
References Cited in the file of this patent UNITED STATES PATENTS 1,738,960 ,Mutscheller Dec. 10, 1929 2,047,555 Gardner July 14, 1936 2,069,081 Setoguchi Jan. 26, 1937 2,165,310 Spaeth July 11, 1939 2,482,826 Bender et al. Sept. 27, '1949

Claims (1)

1. A METHOD OF MAKING A FILAMENT OF REFRACTORY METAL IN THE FORM OF A SUBSTANTIALLY FLATTENED ZIG-ZAG COMPRISING THE STEPS OF PLACING A FILAMENTARY SPIRAL OF SAID REFRACTORY METAL IN INTIMATE CONTACT WITH AT LEAST ONE DUCTILE METAL SO AS TO FORM A RELATIVELY COMPACT STRUCTURE IN WHICH SAID SPIRAL IS SUPPORTED BY SAID DUCTILE METAL, PRESSING SAID STRUCTURE INTO A SUBSTANTIALLY FLATTENED SHAPE IN WHICH THE SPIRAL OF REFRACTORY METAL IS FLATTENED INTO ZIG-ZAG SHAPE, THUS CAUSING SAID DUCTILE METAL OR METALS TO FLOW IN CONTACT WITH SAID SPIRAL AND THEREAFTER CHEMICALLY REMOVING THE DUCTILE METALLIC MATERIAL.
US576510A 1954-12-03 1955-12-05 Methods of producing refractory metal filaments of flattened zig-zag form Expired - Lifetime US2881104A (en)

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GB35096/54A GB798945A (en) 1954-12-03 1954-12-03 Improvements in or relating to electric discharge devices

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530010A (en) * 1968-07-22 1970-09-22 Research Corp Method of making blazed optical diffraction gratings
US4923529A (en) * 1987-10-22 1990-05-08 Tungsram Reszvenytarsasag Equipment for continuous heat treatment of tungsten filaments wound on molybdenum cores

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT222751B (en) * 1960-06-17 1962-08-10 Egyesuelt Izzolampa Process for the production of incandescent lamp filaments

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1738960A (en) * 1926-03-30 1929-12-10 Mutscheller Arthur Vacuum discharge device and method of using the same
US2047555A (en) * 1933-05-31 1936-07-14 Parsons & Co Ltd C A Manufacture of hollow turbine blades
US2069081A (en) * 1932-05-31 1937-01-26 Gen Electric Electric incandescent lamp
US2165310A (en) * 1939-07-11 Filament
US2482826A (en) * 1945-08-04 1949-09-27 Tung Sol Lamp Works Inc Filament structure for thermionic tubes

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2165310A (en) * 1939-07-11 Filament
US1738960A (en) * 1926-03-30 1929-12-10 Mutscheller Arthur Vacuum discharge device and method of using the same
US2069081A (en) * 1932-05-31 1937-01-26 Gen Electric Electric incandescent lamp
US2047555A (en) * 1933-05-31 1936-07-14 Parsons & Co Ltd C A Manufacture of hollow turbine blades
US2482826A (en) * 1945-08-04 1949-09-27 Tung Sol Lamp Works Inc Filament structure for thermionic tubes

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530010A (en) * 1968-07-22 1970-09-22 Research Corp Method of making blazed optical diffraction gratings
US4923529A (en) * 1987-10-22 1990-05-08 Tungsram Reszvenytarsasag Equipment for continuous heat treatment of tungsten filaments wound on molybdenum cores

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NL202520A (en)
NL96915C (en)
GB798945A (en) 1958-07-30

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