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Double crucible for a glass drawing method and method of making glass fiber or a preform with the double crucible

a drawing method and double crucible technology, applied in the field of double crucibles, can solve the problems of difficult or impossible control of the drawing process, and difficulty in sufficiently thorough heating of the contents of the inner crucible, and achieve the effect of comparatively simple features and high quality

Inactive Publication Date: 2006-10-26
BUELLESFELD F +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] It is an object of the present invention to provide a double crucible of the above-described kind for a glass drawing process and / or a method of the above-described kind for making a glass fiber or a preform of it, so that the glass fiber, especially made from heavy metal oxide glass, the so-called HMO glass, is made with a higher quality and has comparatively simple features. HMO glass according to the invention is a glass containing one or more oxides of Bi, Sb, Te, Pb, As, Se, Cd and / or Ga.

Problems solved by technology

However if a glass fiber is made using a glass pair, whose coating glass located in the outer crucible has a lower viscosity than the core glass in the inner crucible, then control of the drawing process has proven to be difficult or impossible.
Furthermore poor heat conduction and / or poor transparency during radiant heating of the glass in the outer crucible can make a sufficiently thorough heating of the contents of the inner crucible difficult.

Method used

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  • Double crucible for a glass drawing method and method of making glass fiber or a preform with the double crucible
  • Double crucible for a glass drawing method and method of making glass fiber or a preform with the double crucible
  • Double crucible for a glass drawing method and method of making glass fiber or a preform with the double crucible

Examples

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Effect test

example 1

[0071] The outer crucible 1 has a height of 250 mm and a diameter of 150 mm, the nozzle 1a of the outer crucible 1 has a length of 45 mm and a diameter of 30 mm. The inner crucible 2 has a height of 500 mm and a diameter of 40 mm and is attached so that its nozzle 2a projects about 15 mm from the nozzle 1a of the outer crucible 1. The nozzle 2a has a length of 60 mm and a diameter of 4 mm. Both crucibles are made from Pt / Ir or Pt5Au.

[0072] In a separate melting step about 4 l of Bi-oxide coating glass are melted in a gold crucible at about 950° C. and ½ l of a similar Bi-oxide core glass are melted in a gold crucible from the glass batch. The glass melts are intensively bubbled with dry oxygen, in order to prevent reduction of the bismuth. Additionally the bubbling prevents separation of the light and heavy glass batch ingredients and provides thorough mixing. Further a gold stirrer can be used.

[0073] The melts are poured into the double crucible pre-heated by coupling in of MF el...

example 2

[0077] The same as in example 1 but good dissolving of the ingredients in the Bi2O3 matrix is achieved. Because of that the melting temperature and thus the formation of elemental bismuth is reduced.

example 3

[0078] The same as in example 1 but the raw materials are mixed in a suitable composition and burned in a first step at 600° C. so that a pre-reaction occurs. Because of that the melting temperature and the formation of elemental bismuth is reduced.

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Abstract

The double crucible for a glass drawing method has a heatable outer crucible (1) and an inner crucible (2) surrounded by the outer crucible (1), which is heatable separately from the outer crucible (1). Both crucibles (1,2) have an outlet nozzle (1a, 2a) for the glass to be drawn. To make glass fibers from heavy metal oxide glass (HMO-glass) with higher quality and comparatively simple crucible features, the outlet nozzle (1a) of the outer crucible (1) extends a certain distance beyond the outlet nozzle (2a) of the inner crucible (2). Surfaces of the outlet nozzles coming in contact with the glass melt are polished and are provided on a material, which has a reducing action on heavy metal glass in the melt in all cases. These surfaces also have sufficient mechanical strength for and chemical inertness to heavy metal oxide glass.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a double crucible for a glass drawing method with a heated outer crucible and an inner crucible surrounding the outer crucible. The inner crucible is formed so that it is heatable separately from the outer crucible. Both inner and outer crucibles have outlet nozzles for the glass to be drawn. The present invention also relates to a method of making glass fiber or a preform of the glass fiber with the double crucible. [0003] 2. Description of the Related Art [0004] Core-clad glass fibers, i.e. glass fibers, which have an inner core comprising a first glass and at least one outer coating or cladding comprising a second glass, are typically drawn from a coaxial double crucible. The cladding or coating glass is located in the outer crucible and the core glass is located in the inner crucible. [0005] In the known manufacturing methods typically double crucibles with heatable outer crucibl...

Claims

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Application Information

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IPC IPC(8): C03B5/193C03B37/07C03B37/023C03B5/167
CPCC03B5/1672C03B2201/60C03B37/023C03B5/1675
Inventor BUELLESFELD, F.KISSL, P.KOLBERG, U.OHMSTEDE, VOLKER
Owner BUELLESFELD F