US3673652A - Filamentary display devices - Google Patents

Filamentary display devices Download PDF

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Publication number
US3673652A
US3673652A US40659A US3673652DA US3673652A US 3673652 A US3673652 A US 3673652A US 40659 A US40659 A US 40659A US 3673652D A US3673652D A US 3673652DA US 3673652 A US3673652 A US 3673652A
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Prior art keywords
coils
temperature
heating
filamentary
range
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US40659A
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English (en)
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Richard Arthur Bonnette
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RCA Corp
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RCA Corp
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    • 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

Definitions

  • One type of filamentary display device comprises an array of electrical resistance filaments individually mounted between pairs of support terminals. By passing an electrical current through various selected ones of the filaments, to heat the filaments to incandescence, various images, e.g., numerals, are displayed.
  • FIG. 1 is a front view of a sub-assembly used in filamentary devices of the type in which the instant invention has utility;
  • FIG. 2 is a section along line 2-2 of HG. l.
  • a plurali- 4 ty of filamentary coils 10 are mounted between pairs of support and terminal posts 12 and 14, the posts being mounted on a substrate 16.
  • two of the posts 14 are each common to two different filaments 10.
  • Means are provided for connecting the posts 12 and 14 to terminal leads of the device, whereby electrical voltages can be applied between individual pairs of posts 12 and 14 to heat the filaments mounted between the post pairs to incandescence.
  • various images e.g., the numerals through 9, in the illustrative embodiment, can be displayed.
  • Each filamentary coil is fonned of a given length of a refractory wire, e.g., tungsten, by which is meant either substantially pure tungsten, or tungsten with such additives as rhenium or thorium oxide.
  • a refractory wire e.g., tungsten
  • the length of the wire increases.
  • the coils are preferably mounted under tension.
  • the coils are fabricated with a length less than the distance between the posts between which the coils are to be mounted, and the coils are stretched and tensioned in the mounting operation.
  • the substrate is mounted on a stem, and the stem-substrate assembly is enclosed within a glass envelope, evacuated, and sealed-off.
  • a sag identified by the reference numeral 20
  • a sag is an out-of-line bulge or curvature of thecoil 10.
  • prior art devices using, for example, coils having an outer diameter of 2 mils and a length of 300 mils, sags in the order of mils often occurred.
  • a hook identified by the reference numeral22 in FIG. 1, is an abrupt bend in theaxial directionofthe coil, the hook generally occurring close to a support post 12 or 14. In the priorart devices, hooks in the order of l0 mils often occurred.
  • Hooks it presently appears, arise as a result of the process used to bond the coil ends to the'support posts 12 and 14, for example, welding or staking. ln the bonding process, the end turns of the coils which are bonded to the posts become twisted and flattened out of the normal planes thereof, thereby tending to distort the coils. Surprisingly, the hooks do not become noticeable until after the device has been completed and operated for at least a short period of time, e.g., 5 to 10 minutes.
  • a post-flashing technique refersto subjecting the various coils to a relatively high voltage heating step after completion of the devices, i.e., after seal-off thereof, but prior to any use of the device at nonnal rated voltages.
  • the actual temperature to which the coils are heated is not known to a high degree of accuracy owing to the difficulty of measuring high temperature of small objects (e.g., the diameter of the coil wire typically used is less than I mil).'ln general, however, the coils are post-flashed to a temperature well in excess of the usual operating temperature of the coils, which, in one embodiment, is in the order of l,250 C. E.g., the coils are heated to a temperature in the range between 1,900C. and 2,500 C. An optical pyrometer is used to measure the coil temperature.
  • the particular temperature to which the coils are heated is not critical. ln tenns of applied voltage, a voltage in the order of 2 k to 3 times the rated voltage is preferred.
  • the duration of the post-flashing operation is also not critical, durations in the range between 2 and 30 seconds'being generally satisfactory. The higher the voltage used, the shorter the time required.
  • the post-flashing operation is preferably performed at thelowest voltage and duration consistent with obtaining satisfactory results.
  • the coils 10 are subjected to a pre-heating operationprior to the final sealing-in of the device. Again, the coils are heated to a temperature well in excessof the usual operating temperature of the coils. While not critical, temperatures in the range between l,700 C. and 2,200 C. appear to provide best results.
  • a preferred means is to pass a current through the coils.
  • the substrate-coil sub-assembly shown in FIG. 1 is mounted on a stem, not shown, having various leads connected to the various support posts 12 and 14.
  • An example of such a stem mounting arrangement is shown in the aforementioned patent.
  • Current is then passed through the coils using standard socketlng means.
  • substantially similar results, with respect to avoiding sag of the filaments during device operation, are obtained by pre-heating the coil, in a non-oxidizing atmosphere, e.g., vacuum, using a voltage of 12 volts for a period of 1 minute, or a voltage of 9 volts for 2 minutes.
  • a non-oxidizing atmosphere e.g., vacuum
  • the higher-voltage shorterduration process is preferable.
  • a further consideration is that the particular pre-heating schedule used appears to affect the amount of distortion of the coils during the pre-heating operation. The higher the voltage used, with attendant shorter process durations, the smaller is the amount of filament distortion which occurs during the process.
  • a preferred process is to heat the coils in a reducing gas atmosphere, e.g., 90 percent nitrogen, 10 percent hydrogen, an open-ended inverted chamber being suitable for the process. Since the presence of the gas atmosphere cools the coils, higher voltages are required to obtain the desired heating. In one embodiment, for example, with a reducing gas pressure slightly in excess of atmospheric pressure, to provide a steady flow of gases out of the chamber, a voltage of 35 volts, d.c. or a.c., for 30 seconds, is used. Also, it appears that somewhat better results, with respect to sag, are obtained performing the pre-heating process in a reducing gas atmosphere rather than in vacuum.
  • a reducing gas atmosphere e.g. 90 percent nitrogen, 10 percent hydrogen
  • the amount of filament distortion occurring during the preheating process is also dependent upon the particular filamentary material used.
  • Commercially available thoriated tungsten wire (1 percent thorium oxide, balance tungsten and trace impurities), for example, is found to sag considerably less during the pre-heating operation than commercially available rhenium-tungsten wire (3 percent rhenium, balance tungsten and trace impurities).
  • rhenium-tungsten wire 3 percent rhenium, balance tungsten and trace impurities.
  • a problem with the use of thoriated tungsten wire is that it is somewhat brittle and rather difficult to form, without excessive loss of product, into the small diameter coils normally used in devices'of the type herein described.
  • rhenium-tungsten' wire is much more satisfactory with respect to the ease of fabrication of the coils, a problem using this wire is that, even using a high voltageshort duration pre-heatingschedule, a relatively large amount of distortion of the coils occurs during the pre-heating process.
  • the coils after the pre-heating step, are restraightened and retensioned by a restretching operation. This is done, in a preferred embodiment, by outwardly bending the posts 12 and 14 between which the coils are mounted, as shown in FIG. 2.
  • the coils are restretched an amount in the order of 15 mils. In general, the coils are restretched an amount necessary to eliminate the distortion caused by the preheating step.
  • the post-flashing operation is also effective to further reduce the amount of sagging which occurs during operation of the devices.
  • the use of the post-flashing operation reduced the amount of sag which developed during use of the devices, on average, from 3 mils to 2 mils.
  • the various coils are made of 0.4 mil diameter rhenium-tungsten wire. Certain ones of the coils are wound at 1,400 turns to the inch, have an outer diameter of 2 mils, and have an unstretched length of mils. When initially mounted, the coils are stretched to a length of 290 mils, thereby having about 800 turns to the inch.
  • the coils are designed to operate at 4.5 volts at 24 milliamperes.
  • the pre-heating is in the aforedescribed reducing atmosphere, at 35 volts, for 30 seconds.
  • the temperature of the coils is in the order of l,850 C.
  • Thecoils are re-stretched 15 mils.
  • the post-flashing operation is at 12.5 volts, for 10 seconds.
  • the temperature of the coils is in the order of 2,l00 C.
  • the pre-heating is done at a slightly higher temperature, using a voltage of 40 volts, for about 15 seconds in a reducing atmosphere. Restretching may or may not be required.
  • a method of fabricating filamentary devices comprising filamentary coils mounted between support terminals and sealed within an envelope, said coils, in usage of said device, operating at a pre-selected temperature, said method comprising:
  • step of again heating said coils is performed by applying a voltage in the range of 2 w to 3 times the voltage applied across the coils during normal operation thereof.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Resistance Heating (AREA)
  • General Induction Heating (AREA)
US40659A 1970-05-26 1970-05-26 Filamentary display devices Expired - Lifetime US3673652A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US4065970A 1970-05-26 1970-05-26

Publications (1)

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US3673652A true US3673652A (en) 1972-07-04

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US40659A Expired - Lifetime US3673652A (en) 1970-05-26 1970-05-26 Filamentary display devices

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US (1) US3673652A (OSRAM)
BE (1) BE767563A (OSRAM)
BR (1) BR7103064D0 (OSRAM)
CA (1) CA950526A (OSRAM)
CH (1) CH539338A (OSRAM)
EG (1) EG10329A (OSRAM)
ES (1) ES391353A1 (OSRAM)
FR (1) FR2093776A5 (OSRAM)
GB (1) GB1315597A (OSRAM)
NL (1) NL7107153A (OSRAM)
SE (1) SE360777B (OSRAM)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5567192A (en) * 1994-05-31 1996-10-22 Cummings Incorporated Method and apparatus for processing electron gas discharge tubing

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2812508A (en) * 1954-10-20 1957-11-05 Westinghouse Electric Corp Filament lighting contact assembly for fluorescent lamp exhaust machines
US2991387A (en) * 1958-09-22 1961-07-04 Burroughs Corp Indicator tube
US3408523A (en) * 1966-05-06 1968-10-29 Ohmega Lab Light bulb with a plurality of independently connected filaments for indicating graphic symbols
US3483609A (en) * 1967-10-31 1969-12-16 Gen Electric Incandescent lamp manufacture
US3529335A (en) * 1966-05-06 1970-09-22 Pinlites Inc Method of making a light bulb with a plurality of independently connected filaments for indicating graphic symbols
US3564325A (en) * 1969-04-29 1971-02-16 Rca Corp Display device including a point image

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2812508A (en) * 1954-10-20 1957-11-05 Westinghouse Electric Corp Filament lighting contact assembly for fluorescent lamp exhaust machines
US2991387A (en) * 1958-09-22 1961-07-04 Burroughs Corp Indicator tube
US3408523A (en) * 1966-05-06 1968-10-29 Ohmega Lab Light bulb with a plurality of independently connected filaments for indicating graphic symbols
US3529335A (en) * 1966-05-06 1970-09-22 Pinlites Inc Method of making a light bulb with a plurality of independently connected filaments for indicating graphic symbols
US3483609A (en) * 1967-10-31 1969-12-16 Gen Electric Incandescent lamp manufacture
US3564325A (en) * 1969-04-29 1971-02-16 Rca Corp Display device including a point image

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5567192A (en) * 1994-05-31 1996-10-22 Cummings Incorporated Method and apparatus for processing electron gas discharge tubing

Also Published As

Publication number Publication date
EG10329A (en) 1976-06-30
BR7103064D0 (pt) 1973-04-12
DE2125953A1 (de) 1971-12-02
ES391353A1 (es) 1973-07-16
DE2125953B2 (de) 1975-06-19
SE360777B (OSRAM) 1973-10-01
CA950526A (en) 1974-07-02
FR2093776A5 (OSRAM) 1972-01-28
GB1315597A (en) 1973-05-02
BE767563A (fr) 1971-10-18
NL7107153A (OSRAM) 1971-11-30
CH539338A (de) 1973-07-15

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