# US 4,394,453 A · Envelopes for tungsten-halogen lamps

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- Number: US 4,394,453 A
- Document ID: US4394453A
- Status: Granted
- Kind: A
- Application number: 06/299,737
- Filed: 1981-09-08
- Granted: 1983-07-19
- Earliest claimed: 1981-09-08
- Assignees: Corning Glass Works
- Inventors: William H. Dumbaugh, Jr.
- Web page: https://patentgrep.com/patent/US4394453A

## CPC

- H01K 1/28: Envelopes; Vessels
- C03C 3/091: containing aluminium
- H01K: ELECTRIC INCANDESCENT LAMPS (details, apparatus or processes for manufacture applicable to both discharge devices and incandescent lamps H01J; light sources using a combination of incandescent and other types of light generation H01J61/96, H05B35/00)
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS

## 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.degree. C., a coefficient of thermal expansion (0.degree.-300.degree. C.) of 42-45.times.10.sup.-7 /.degree.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 ______________________________________ 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 ______________________________________

## Claims

### Claim 1

A glass envelope for a tungsten-halogen incandescent lamp, said glass exhibiting a strain point of at least 670.degree. C., a coefficient of thermal expansion (0.degree.-300.degree. C.) of 42-45.times.10.sup.-7 /.degree.C., a liquidus temperature below 1150.degree. C., and a viscosity at the liquidus temperature greater than 2.times.10.sup.4 poises, and consisting essentially, expressed in weight percent on the oxide basis, of
______________________________________ 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 Al.sub.2 O.sub.3 +SiO.sub.2 being held between 74.5-78, the weight ratio SiO.sub.2 :Al.sub.2 O.sub.3 being held between about 3.3-3.8, and the weight ratio CaO:MgO being held between about 1.3-1.8.

### Claim 2 (depends on 1)

A glass envelope according to claim 1 consisting essentially of
______________________________________ Al.sub.2 O.sub.3 17.4 .+-. 0.2 B.sub.2 O.sub.3 4.5 .+-. 0.1 CaO 10.9 .+-. 0.1 MgO 7.8 .+-. 0.1 SiO.sub.2 59.4 (remainder) ______________________________________