US3798490A - Vibration resistant lamp - Google Patents

Vibration resistant lamp Download PDF

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Publication number
US3798490A
US3798490A US00285938A US3798490DA US3798490A US 3798490 A US3798490 A US 3798490A US 00285938 A US00285938 A US 00285938A US 3798490D A US3798490D A US 3798490DA US 3798490 A US3798490 A US 3798490A
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Prior art keywords
tungsten
thoria
filament
lamp
percent
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Expired - Lifetime
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US00285938A
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English (en)
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S Ackerman
T Dunham
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General Electric Co
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General Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K1/00—Details
    • H01K1/02—Incandescent bodies
    • H01K1/04—Incandescent bodies characterised by the material thereof

Definitions

  • ABSTRACT An incandescent lamp having a filament made of tungsten wire containing between l-2 percent by weight thoria has greatly improved resistance to fracture caused by shock and vibration thereby increasing the service life of the lamp.
  • the thoriated tungsten filament has a recrystallized grain structure which is characterized by approximately equiaxed crystals of tungsten of a smaller and more uniform size and thoria particles which are more uniformly distributed throughout the tungsten matrix than can be obtained by conventional powder metallurgy.
  • This invention relates generally to incandescent lamps having tungsten filaments. More particularly, the invention relates to a lamp having a thoriated tungsten filament which has a unique grain structure to give greatly increased resistance to fracture caused by vibration and shock.
  • thoriated tungsten wire was substituted for unalloyed tungsten or, in some cases, for tungsten doped with aluminum, sodium, silicon and potassium known as lamp-doped tungsten.
  • Various percentages of thoria were added to the tungsten to improve strength and fracture resistance in lamps. It was found that thoriated tungsten ingots were difficult to process into filament wire. This difficulty and the accompanying production losses increased proportionately with an increase in the percentage of thoria. Because of the high production losses, it has not been economically feasible to manufacture a thoriated tungsten wire of relatively small diameter with more than approximately 1 percent by weight thoria.
  • This 1% thoriated wire known in one commercial form as NF wire, although an improvement over unalloyed tungsten and lamp-doped tungsten, continued to fracture and fail at a relatively high rate due to the presence of large crystals of tungsten.
  • Still another object of the invention is to manufacture a lamp with a tungsten filament having more than 1 percent by weight of thoria.
  • the objects of the invention are accomplished by producing a lamp containing a filament of tungsten alloyed with between 1 and 2 percent by weight of thoria with the recrystallized tungsten particles being approximately equiaxed crystals of a grain size smaller and more uniform in size than can be obtained by conventional powder metallurgy preparation and the thoria particles being more uniformly distributed throughout the tungstenmatrix. Increased dampening capacity and associated resistance to fracture caused by vibration is related to grain size and the number of grain boundaries.
  • the filament has tungcessing is necessary. This process and dispersion alloy sten crystals significantly smaller and more uniform in size than that obtained in other thoriated tungsten wire. With the smaller and more uniform tungsten grain wire,
  • the process for making the filament wire comprises the making of a porous compact of tungsten particles, soaking the compact in water, then soaking the water-saturated compact in a solution of aqueous Th(NO having a concentration of approximately 520 grams Th0; per liter of solution for about 30 hours.
  • the compact is removed and then vacuum dried until the greater part of the solvent has evaporated thereby leaving a thorium-rich additive in the tungsten.
  • the compact is presintered in hydrogen at approximately 1200C to convert thorium nitrate to thorium oxide.
  • This compact or ingot is then rolled, swaged and drawn by conventional means to form the diameter wire required for the filament.
  • FIG. 1 is an elevation view partially in section of an automotive stop, tail and signal lamp
  • FIG. 2 is a graph illustrating test data of conventional thoriated filament lamps and thoriated tungsten filament lamps of the invention
  • FIG. 3 is a photograph taken at lOOOX magnification of a 2.2-mil wire of the prior art.
  • FIG. 4 is a photograph taken at lOOOX magnification of a 2.2-mil wire used in the lamp of the invention.
  • lamp 1 is comprised of envelope 2 to which is sealed re-entrant stem 3. Pairs of lead-in conductors 4 and 5 are hermetically sealed to re-entrant stem 3.
  • the lamp 1 of the invention may contain a fill of inert gas such as argon or may be a vacuum lamp.
  • the two-filament lamp illustrated in FIG. 1 is commonly used in automobiles for stop, tail and turn signal lighting.
  • the invention is not limited to a twofilament lamp since the lamp may have a single filament or two or more filaments.
  • Filament 6 is known as the major filament and is used for stop and turn signal lighting purposes. This filament is connected to lead-in conductors 4', one of which is attached to the base shell 8 and the other of which is attached to contact tab 9. Since major filament 6 requires a higher color temperature, it is usually made of a lamp-doped tungsten.
  • Minor filament 7 is connected to lead-in conductors which are, in turn, connected to contact tab 9 and base 8 which serves as a common contact for both filaments.
  • Contacts 9 and 10 are electrically insulated from each other by plastic insulator 11. Also shown as part of base member 8 is one of two alignment lugs 12 which serve to locate the lamp 1 in an automobile socket, not shown.
  • Filament 7 burns with a color temperature of approximately 2260K at a design voltage of 14 volts and generally has a smaller diameter than that of major filament 6. Because of the smaller diameter of filament 7, necessitated in part by candle power and wattage requirements, the lamp 1 has a tendency to fail predominantly through fracture of filament 7. Some experimental data show that 60 percent of the two-filament lamp failures are due to failure of minor filament 7.
  • the Michigan Tester One of the methods used to test lamps subject to vibration in various applications, such as automobiles, is known as the Michigan Tester.”
  • This test device holds a lamp in contact with a rotating cam which has four equally spaced steps on the circumference of the cam. As the cam rotates, the lamps drop from step to step. This movement imparts a force or a bounce which simulates the vibrational forces exerted on a lamp when an automobile hits a bump.
  • Lamps on the Tester were in electrical contact with a power source which would cycle the lamps on and off to simulate user conditions in which tail, stop and signal lamps are used only a portion of the time.
  • FIG. 2 Michigan test results of lamps using 1% by weight thoriated tungsten wire of the prior art are shown in FIG. 2 as circles.
  • the triangles on the graph indicate service life of lamps manufactured with wire having the uniquely small tungsten grain structure and the more uniformly distributed thoria. Four of these lamps are shown as light triangles in the upper left portion of the graph because they failed at about the same time the four lamps illustrated by the circles failed.
  • the horizontal axis of the graph of FIG. 2 is the number of hours oflamp service life as measured by the electrical continuity of minor filament 7, and the vertical axis indicates the percentage of lamps that survived for a given number of hours.
  • FIG. 3 shows the grain size of the outer diameter surface of thoriated wire of the prior art after it has been tested on the Michigan Tester.
  • the photograph of FIG. 3 is a IOOOX magnification of a 2.2-mil wire which is generally used for minor filament 7 of stop, turn and tail lamp 1.
  • a IOOOX magnification of a 2.2-mil wire which is generally used for minor filament 7 of stop, turn and tail lamp 1.
  • there are large size grains of tungsten with the largest being located at the upper right side of the photo. Large grain size microstructures have fewer grain boundaries through which to absorb the vibrational force. Accordingly, the wire shown in FIG. 3 has a greater likelihood of fracture.
  • the 1.7 weight percent, 2.2-mil wire of the present invention magnified 1000 times as shown in the photograph of FIG. 4 has many small grains of tungsten. This, in turn, gives a greater number of grain boundaries which can absorb or dampen the vibrational force.
  • the lamp filament is prepared by way of a new wire processing method as is more fully described in copending applications, Ser. Nos. 186,143 and 248,933, assigned to the same assignee as the present invention.
  • An incandescent lamp comprising a sealed vitreous envelope, lead-in conductors hermetically sealed in the envelope and connected to an incandescible filament wherein the improvement comprises that the filament material consists essentially of a tungsten alloy containing between 1 and 2 percent by weight of thoria (ThO said tungsten alloy having a recrystallized grain structure of approximately equiaxed tungsten crystals with a grain size smaller and more uniform in size than can be obtained by conventional powder metallurgy preparation.
  • thoria particles being distributed more uniformly throughout the tungsten than can be obtained by conventional powder metallurgy processes.
  • An incandescent lamp comprising a sealed vitreous envelope, lead-in conductors hermetically sealed in the envelope and connected to a plurality of incandescible filaments .
  • the improvement comprises that one of the filaments consists essentially of a tungsten alloy containing between 1 and 2 percent thoria by weight, said tungsten alloy having a recyrstallized grain structure of approximately equiaxed tungsten crystals with a grain size smaller than can be obtained by conventional powder metallurgy preparation.

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US00285938A 1972-09-01 1972-09-01 Vibration resistant lamp Expired - Lifetime US3798490A (en)

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US28593872A 1972-09-01 1972-09-01

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JP (1) JPS559779B2 (enrdf_load_html_response)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3970888A (en) * 1973-07-23 1976-07-20 Siemens Aktiengesellschaft Tungsten-thorium dioxide-aluminum oxide mass for a high-temperature-resistant emission electrode and process for the production thereof
US4296352A (en) * 1979-12-19 1981-10-20 General Electric Company Incandescent lamp
US20030209985A1 (en) * 2002-05-13 2003-11-13 Federal-Mogul World Wide, Inc. Red incandescent automotive lamp and method of making the same
US20100084972A1 (en) * 2008-10-06 2010-04-08 Shaam Sundhar High-Efficiency Light Bulb
CN103021797A (zh) * 2012-11-27 2013-04-03 高金菊 一种长寿命灯泡用灯丝

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS621686A (ja) * 1985-06-25 1987-01-07 株式会社シマノ 自転車用デイレ−ラ−

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3211943A (en) * 1963-10-07 1965-10-12 Gen Electric Electric incandescent lamp
US3697321A (en) * 1967-06-21 1972-10-10 Siemens Ag Thermionic cathode and method of manufacturing the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3211943A (en) * 1963-10-07 1965-10-12 Gen Electric Electric incandescent lamp
US3697321A (en) * 1967-06-21 1972-10-10 Siemens Ag Thermionic cathode and method of manufacturing the same

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3970888A (en) * 1973-07-23 1976-07-20 Siemens Aktiengesellschaft Tungsten-thorium dioxide-aluminum oxide mass for a high-temperature-resistant emission electrode and process for the production thereof
US4296352A (en) * 1979-12-19 1981-10-20 General Electric Company Incandescent lamp
US20030209985A1 (en) * 2002-05-13 2003-11-13 Federal-Mogul World Wide, Inc. Red incandescent automotive lamp and method of making the same
US6906464B2 (en) * 2002-05-13 2005-06-14 Federal-Mogul World Wide, Inc. Red incandescent automotive lamp and method of making the same
US20100084972A1 (en) * 2008-10-06 2010-04-08 Shaam Sundhar High-Efficiency Light Bulb
CN103021797A (zh) * 2012-11-27 2013-04-03 高金菊 一种长寿命灯泡用灯丝
CN103021797B (zh) * 2012-11-27 2015-09-09 高金菊 一种长寿命灯泡用灯丝

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JPS4987166A (enrdf_load_html_response) 1974-08-21
JPS559779B2 (enrdf_load_html_response) 1980-03-12
FR2198261B3 (enrdf_load_html_response) 1976-07-30
FR2198261A1 (enrdf_load_html_response) 1974-03-29

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