Glass manufacturing – Fiber making apparatus – With drawing means
Reexamination Certificate
1998-03-25
2001-07-10
Hoffmann, John (Department: 1731)
Glass manufacturing
Fiber making apparatus
With drawing means
C065S374150, C065S374120
Reexamination Certificate
active
06257023
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of Invention
The present invention relates to a fiber optic draw furnace for making optical fiber; and more particularly to insulators for separating a heating element from an outer furnace shell in graphite resistance and inductance furnaces.
2. Discussion of Related Art
Known graphite resistance fiber optic draw furnaces typically have a standard graphite felt insulation insert that may be nonhomogeneous (density variation). The standard graphite felt insulation is very “dirty” (loose graphite particles and graphite fibers). The standard graphite felt is also very susceptible to moisture and oxygen absorption.
SUMMARY OF THE INVENTION
The present invention provides an improvement to a fiber optic draw furnace having a heating element arranged inside a furnace shell for drawing an optical fiber from a preform. The fiber optic draw furnace has one or more fiber draw furnace insulation to separate the heating element from the furnace shell for reducing the thermal transfer therebetween. At least one of the fiber draw furnace insulation means is made from rigidified high purity graphite felt that provides highly efficient thermal insulation between the heating element and the outer furnace shell. The rigidified high purity graphite felt insulation may include either a bottom insulation ring, a cylindrical insulation insert or a cylindrical insulation canister.
Some advantages of the rigidified high purity graphite felt insulation include the fact that it has less density variation than standard (i.e. non-rigidified) felt, and therefore, has superior temperature uniformity; does not generate loose graphite particles or graphite fiber; and are resistant to moisture and oxygen absorption.
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Spencer Robert A.
Uhm Daniel D.
Alcatel
Hoffmann John
Ware Fressola Van der Sluys & Adolphson LLP
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