Halogen incandescent lamp

#This invention relates to halogen incandescent lamps, more specifically to halogen incandescent lamps using aluminosilicate glass for bulb material.

#As compared with ones containing no halogen, tungsten-filament incandescent lamps with halogen sealed therein are improved in compactness, efficiency and life performance, performing halogen cycles which will prevent bulb blackening till the end of the life. Accordingly, they are utilized in various fields of illumination.

#In one such halogen incandescent lamp, the temperature of a glowing bulb needs to be kept at a high temperature of approximately 250.degree. C. or higher lest tungsten halide should stick to the inside wall of the bulb during halogen cycles. For the material of the bulb, therefore, there has been used quartz glass or high silica glass which can resist high heat load.

#This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawing, in which:

#FIG. 1A is a front sectional view of a halogen incandescent lamp according to an embodiment of this invention;

#FIG. 1B is a side sectional view of the halogen incandescent lamp of FIG. 1A; and

#This invention is based on a view that all the drawbacks of the prior art halogen incandescent lamps may be eliminated by using molybdenum or tungsten wires as lead-in wires to be sealed in a bulb of a halogen incandescent lamp, and aluminosilicate glass as glass material with a thermal expansion coefficient approximate to that of the molybdenum or tungsten wires and a relatively high strain point.

#The aluminosilicate glass forming the bulb of the halogen incandescent lamp of this invention has the following physical properties.

#Strain point: 660.degree. C. or higher.