Envelopes for tungsten-halogen lamps

• US 4,394,453 A
• Filed: 09/08/1981
• Issued: 07/19/1983
• Est. Priority Date: 09/08/1981
• Status: Expired due to Term

• Current Assignee: Corning Glass Works Inc. (Corning Incorporated)
• Original Assignee: Corning Glass Works Inc. (Corning Incorporated)
• Inventors: Dumbaugh, William H. Jr.
• Primary Examiner(s): Bell, Mark
• Application Number:
  US06/299,737
• Time in Patent Office: 679 Days
• Field of Search: 313/221, 501/66
• US Class Current: 501/66
• CPC Class Codes: C03C 3/091 containing aluminium
• CPC Class Codes: H01K 1/28 Envelopes; Vessels

Abstract

The present invention is directed to glasses especially suitable as envelopes for tungsten-halogen lamps. The glasses exhibit strain points of at least about 670° C., a coefficient of thermal expansion (0°-300° C.) of 42-45×10^-7 /°C. and can be readily melted and shaped utilizing conventional glass melting and high speed tube drawing processes. The glasses consist essentially, in weight percent, of

______________________________________                                    

SiO₂ 60.0 ± 1.5 Al₂ O₃ 17.0 ± 1.0 B₂ O₃ 5.0 ± 0.8 CaO 11.4 ± 0.8 MgO 7.5 ± 0.8 ______________________________________

Claims

1. A glass envelope for a tungsten-halogen incandescent lamp, said glass exhibiting a strain point of at least 670°

C., a coefficient of thermal expansion (0°

-300°

C.) of 42-45×

10^-7 /°

C., a liquidus temperature below 1150°

C., and a viscosity at the liquidus temperature greater than 2×

10⁴ poises, and consisting essentially, expressed in weight percent on the oxide basis, of

space="preserve" listing-type="tabular">______________________________________ SiO.sub.2 60.0 ±

1.5 Al.sub.2 O.sub.3 17.0 ±

1.0 B.sub.2 O.sub.3 5.0 ±

0.8 CaO 11.4 ±

0.8 MgO 7.5 ±

0.8 ______________________________________

the total Al₂ O₃ +SiO₂ being held between 74.5-78, the weight ratio SiO₂ ;

Al₂ O₃ being held between about 3.3-3.8, and the weight ratio CaO;

MgO being held between about 1.3-1.8.

2. A glass envelope according to claim 1 consisting essentially of