Glass manufacturing – Fiber making apparatus – With means for cooling newly formed fiber – filament – or...
Reexamination Certificate
1999-04-05
2001-11-13
Hoffman, John (Department: 1731)
Glass manufacturing
Fiber making apparatus
With means for cooling newly formed fiber, filament, or...
C065S537000, C065S292000, C065S271000
Reexamination Certificate
active
06314767
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to apparatus for manufacturing an optical fiber preform, the apparatus comprising a glassmakers' lathe for holding a glass tube by means of chucks clamped to the two ends of the tube, gas feed means for injecting gaseous compounds into the inside of the tube via a leakproof connection at one end of the tube, and a source of the energy required for causing the gaseous compounds to be deposited inside the tube or for collapsing the tube after deposition has been completed.
BACKGROUND OF THE INVENTION
In such a device, heat energy from the source is transmitted to the leakproof connection via the corresponding end of the glass tube. This connection has a sealing gasket which is thus raised to a high temperature while the gaseous compounds are being deposited or while the tube is being collapsed. Unfortunately, it is very important for the gasket to maintain a good seal so as to prevent any risk of the gaseous compounds being exhausted into the medium surrounding the apparatus, and to avoid any contamination of the deposit by the surrounding medium.
A known solution to the problem of the leakproof connection between the gas feed means and the end of the tube being overheated consists in designing a gasket of a complex shape and in making it out of special materials so as to guarantee that the connection remains sealed at the temperatures generated by a blowtorch. Unfortunately, that solution increases the cost of manufacturing a preform.
Another known solution to the above problem consists in holding the glass tube on the lathe by means of a tubular endpiece. In this way, the end of the tube is located at a certain distance from the leakproof connection and the corresponding chuck which come into contact only with the tubular endpiece. The inside diameter of the endpiece is slightly greater than the outside diameter of the glass tube and it is assembled thereto by adhesive acting on an overlap zone where the glass tube is received in the tubular endpiece. This establishes a discontinuity which enables a large part of the heat energy to be dissipated by means of the end section of the glass tube. Nevertheless, that solution also increases cost due to making and assembling the endpiece.
After a preform has been subjected to an internal deposition method, similar problems arise when the preform is collapsed. At that time, the preform is held at its ends by the chucks. While the preform is being heated by the heater means for the purpose of collapsing it, the thermal radiation generated by the heater means heats the chucks that are holding the preform, thereby running a risk of the chucks becoming jammed.
Finally, similar problems arise when drawing an optical fiber from a preform. At that time, the preform is held vertically at one of its ends by means of a chuck. While the preform is being heated by the fiber-drawing oven, the thermal radiation it generates heats the chuck that is holding the preform and that also can run the risk of the chuck becoming jammed.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to solve the problem of the leakproof connection between the gas feed unit and the end of the glass tube overheating in apparatus for manufacturing a preform, and to do in a manner that combines effectiveness and low cost.
Another object of the invention is to solve the problem of overheating the means for holding a preform while it is being collapsed or while a fiber is being drawn therefrom.
To this end, the invention provides apparatus for manufacturing an optical fiber preform from a tube of vitreous material, the apparatus comprising
means for holding said tube during manufacture of said preform; and
heater means supplying said tube with the heat energy required for manufacturing said preform; and
diffuser means placed around at least one of the ends of said tube to trap and diffuse light radiation generated in said tube by said heater means.
The invention also provides an apparatus for drawing an optical fiber from a preform, the apparatus comprising
means for holding one end of said preform; and
means for lowering said preform as held by said end through a fiber drawing oven; and
diffuser means disposed around said end of said preform to trap and diffuse light radiation generated in said end by said fiber drawing oven.
The heat energy supplied by the heater means propagates along the tube or the preform towards its ends mainly in the form of light radiation. The heat energy which is thus trapped and diffused by the diffuser means is therefore not transmitted to the leakproof connection or to the supporting chuck, thereby contributing to reducing the heating thereof.
Advantageously, the diffuser means has a refractive index close to that of the tube. By way of example, it can likewise be made of a vitreous material. This makes it possible to obtain good transmission of the radiation between the tube and the diffuser means.
Also advantageously, a liquid film can be inserted between the diffuser means and the tube. The light radiation passes from the tube to the diffuser means via the liquid film, and the diffuser means diffuses it to the surrounding medium. This increases the amount of light radiation that is transmitted from the tube to the diffuser means. The liquid film can have a refractive index that is close to that of the tube and of the diffuser means.
The invention makes it quick and easy to place the diffuser means on the glass tube, thereby making savings in equipment costs and in machine time costs. In addition, the risk of breaking the glass tube while the diffuser means is being mounted is considerably reduced compared with sticking on a tubular endpiece.
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Lavanant Gerard
Pezet Didier
Alcatel
Hoffman John
Sughrue Mion Zinn Macpeak & Seas, PLLC
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