Process for manufacturing incandescent lamps having gettering agents

• US 5,800,235 A
• Filed: 02/27/1996
• Issued: 09/01/1998
• Est. Priority Date: 02/27/1996
• Status: Expired due to Fees

• Current Assignee: Illumination Technology Incorporated
• Original Assignee: Illumination Technology Incorporated
• Inventors: Ragsdale, Charles R.
• Primary Examiner(s): Ramsey, Kenneth J.
• Application Number:
  US08/607,723
• Time in Patent Office: 917 Days
• Field of Search: 445/41, 445/48, 445/55, 445/9, 427/111
• US Class Current: 445/48
• CPC Class Codes: H01J 61/26 Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope
• CPC Class Codes: H01K 1/54 Means for absorbing or absorbing gas, or for preventing or removing efflorescence, e.g. by gettering
• CPC Class Codes: H01K 3/02 Manufacture of incandescent bodies
• CPC Class Codes: H01K 3/22 Exhausting, degassing, filling, or cleaning vessels

Abstract

Filaments having a thin exterior tungsten phosphide layer for use in incandescent lamps are made by exposing tungsten filaments to vapors of elemental phosphorous at approximately 675° to 725° C. in an evacuated vacuum furnace. The tungsten phosphide layer protects the filaments from oxidation while the lamps are manufactured, and decomposes to tungsten and phosphorous when the lamp is first energized by current. The resulting elemental phosphorous acts as a gettering agent.

Claims

1. In the process for manufacturing incandescent light bulbs of the type which include a gettering agent within the light bulb, the improvement comprising the steps of:

placing a plurality of tungsten filaments for the light bulbs into a vacuum furnace;

placing red phosphorous on the proximity of said plurality of filaments in the vacuum furnace;

heating the vacuum furnace until the temperature of said plurality of filaments rises above approximately 675°

C., and until the temperature of the red phosphorous reaches at least approximately 400°

C., maintaining said filaments in temperature range above approximately 675°

C. for a time period and maintaining the temperature of the red phosphorous at least approximately 400°

C. for a time period;

continuously evacuating the vacuum furnace at least during part of the time period while the furnace is being heated whereby said plurality of filaments are exposed to vapors of phosphorous and react therewith to form tungsten phosphides on the surface of said filaments, and

discontinue heating and evacuating the vacuum furnace and removing said plurality of filaments from the furnace.

2. In the process for manufacturing incandescent light bulbs of the type which include a gettering agent within the light bulb, the improvement comprising the steps of:

placing a plurality of tungsten filaments for the light bulbs into a vacuum furnace;

placing red phosphorous in the proximity of said plurality of filaments in the vacuum furnace;

heating the vacuum furnace until the temperature of said plurality of filaments rises to a range approximately between 675° and

725°

C., and until the temperature of the red phosphorous reaches a range approximately between 675° and

725°

C., maintaining said filaments in said temperature range above approximately 675°

C. for a first time period and maintaining the temperature of the red phosphorous in said range for a second time period;

evacuating the vacuum furnace at least during part of the first time period whereby said plurality of filaments are exposed to vapors of phosphorous and react therewith to form tungsten phosphides on the surface of said filaments, and

discontinue heating and evacuating the vacuum furnace and removing said plurality of filaments from the furnace.

3. The improvement in the process in accordance with claim 2 where said plurality of filaments and said red phosphorous are both heated to a temperature of approximately 725°

C.

4. The improvement in the process in accordance with claim 3 where the step of evacuating the vacuum furnace is commenced when the temperature of said plurality of filaments and of said red phosphorous reaches approximately 200°

C.

5. In the process for manufacturing incandescent light bulbs of the type which include a gettering agent within the light bulb, the improvement comprising the steps of:

placing a plurality of filaments for the light bulbs into a vacuum furnace;

placing red phosphorous in the proximity of said plurality of filaments in the vacuum furnace;

heating the vacuum furnace until the interior temperature rises above approximately 675°

C. and maintaining the interior temperature above approximately 675°

C. for a predetermined time period;

after the step of heating is commenced evacuating the vacuum furnace by connecting the furnace to a source of vacuum and keeping the furnace connected to the source of vacuum thereby keeping the furnace evacuated for at least a part of the predetermined time period and thereby exposing said plurality of filaments to vapors of phosphorous and causing the vapors to react with the filaments to form tungsten phosphides on the surface of said filaments, and

discontinue heating and evacuating the vacuum furnace and removing said plurality of filaments from the furnace.

6. The improvement in the process in accordance with claim 5 where the step of evacuating is commenced when the interior temperature reaches approximately 200°

C.

7. The improvement in the process in accordance with claim 5 where said plurality of filaments and said red phosphorous each are placed into a vessel, the vessel remains unsealed and is placed into the vacuum furnace.

8. In the process for manufacturing incandescent light bulbs of the type which include a gettering agent within the light bulb, the improvement comprising the steps of:

placing a plurality of filaments for the light bulbs into a vacuum furnace;

placing red phosphorous in the proximity of said plurality of filaments in the vacuum furnace;

heating the vacuum furnace until the interior temperature rises to approximately 725°

C. and maintaining the interior temperature at approximately 725°

C. for a predetermined time period;

after the step of heating is commenced evacuating the vacuum furnace by connecting the furnace to a source of vacuum, and keeping the furnace evacuated for at least a part of the predetermined time period and thereby exposing said plurality of filaments to vapors of phosphorous and causing the vapors to react with the filaments to form tungsten phosphides on the surface of said filaments, and

discontinue heating and evacuating the vacuum furnace and removing said plurality of filaments from the furnace.

9. The improvement in the process in accordance with claim 8 where the interior temperature of the vacuum furnace is raised substantially linearly from ambient temperature to approximately 725°

C.

10. In the process for manufacturing incandescent light bulbs of the type which include a gettering agent within the light bulb, the improvement comprising the steps of:

placing a plurality of filaments for the light bulbs into a vacuum furnace;

placing red phosphorous in the proximity of said plurality of filaments in the vacuum furnace;

heating the vacuum furnace until the interior temperature rises above approximately 675°

C. and maintaining the interior temperature above approximately 675°

C. for a predetermined time period, said step of heating being conducted for approximately 10 minutes;

after the step of heating is commenced evacuating the vacuum furnace by connecting the furnace to a source of vacuum, and keeping the furnace evacuated for at least a part of the predetermined time period and thereby exposing said plurality of filaments to vapors of phosphorous and causing the vapors to react with the filaments to form tungsten phosphides on the surface of said filaments, and

discontinue heating and evacuating the vacuum furnace and removing said plurality of filaments from the furnace.

11. A process for manufacturing filaments suitable for incorporation into incandescent light bulbs, said filaments comprising a tungsten core and an outer surface of tungsten phosphide, the process comprising:

placing a plurality of tungsten filaments into a vacuum furnace;

heating the furnace to maintain the tungsten filaments at a temperature above approximately 675°

C.;

evacuating the furnace and keeping the furnace evacuated by having it connected to a vacuum source while the temperature is maintained above approximately 675°

C.;

exposing said filaments to vapors of phosphorous while maintaining said plurality of filaments at a temperature above approximately 675°

C. and while keeping the furnace evacuated, and

allowing the furnace to cool and removing said plurality of filaments from the furnace.

12. The process in accordance with claim 11 where the furnace is evacuated to a pressure of approximately 100 millitorr.

13. The process in accordance with claim 11 where the step of exposing said filaments to vapors of phosphorous comprises keeping solid red phosphorous within the furnace and maintaining said solid phosphorous at a temperature of at least approximately 400°

C.

14. A process for manufacturing filaments suitable for incorporation into incandescent light bulbs, said filaments comprising a tungsten core and an outer surface of tungsten phosphide, the process comprising:

placing a plurality of tungsten filaments into a vacuum furnace;

heating the furnace to maintain the tungsten filaments at a temperature at approximately 725°

C.;

evacuating the furnace and keeping the furnace evacuated while the temperature is maintained at approximately 725°

C.;

exposing said filaments to vapors of phosphorous while maintaining said plurality of filaments at a temperature of approximately 725°

C. and while keeping the furnace evacuated, and

allowing the furnace to cool and removing said plurality of filaments from the furnace.

15. A process for manufacturing filaments suitable for incorporation into incandescent light bulbs, said filaments comprising a tungsten core and an outer surface of tungsten phosphide, the process comprising:

placing a plurality of tungsten filaments into a vacuum furnace;

heating the furnace to maintain the tungsten filaments at a temperature in the range of approximately 675°

to 725°

C.;

evacuating the furnace and keeping the furnace evacuated, the step of evacuating the furnace comprising connecting the furnace to a vacuum source when the internal temperature of the furnace is approximately 200°

C., and thereafter keeping the furnace connected to the vacuum source while the temperature is raised to and thereafter maintained in the range of approximately 675°

to 725°

C.;

exposing said filaments to vapors of phosphorous while maintaining said plurality of filaments at a temperature in the range of approximately 675°

to 725°

C. and while keeping the furnace evacuated, and

allowing the furnace to cool and removing said plurality of filaments from the furnace.

16. A process for manufacturing filaments suitable for incorporation into incandescent light bulbs, said filaments comprising a tungsten core and an outer surface of tungsten phosphide, the process comprising:

placing a plurality of tungsten filaments into a vacuum furnace;

heating the furnace to maintain the tungsten filaments at a temperature above approximately 675°

C.;

evacuating the furnace and keeping the furnace evacuated while the temperature is maintained above approximately 675°

C.;

exposing said filaments to vapors of phosphorous, the step of exposing said filaments to vapors of phosphorous comprises keeping solid red phosphorous within the furnace and maintaining said solid phosphorous at a temperature in the range of approximately 675°

to 725°

C. and while keeping the furnace evacuated, and

allowing the furnace to cool and removing said plurality of filaments from the furnace.