Apparatus and Process for Cooling Optical Fibers During the Drawing Process
Publication Date: 2005-Mar-02
The IP.com Prior Art Database
APPARATUS AND PROCESS FOR COOLING OPTICAL FIBERS DURING THE DRAWING PROCESS
Optical fibers are typically formed by a process in which hot fibers are drawn from the end of a massive cylindrical silica or glass perform that has been heated up to its softening point in a drawing furnace. This drawing process is followed by cooling the fibers within a coolant chamber or heat exchanger utilizing a coolant gas that flows through the heat exchanger in a co-current or countercurrent direction with respect to the velocity vector of the fiber traveling through the exchanger. The drawn fibers must be cooled to a sufficient temperature within the heat exchanger prior to cladding the fiber with a heat sensitive protective coating.
Normally these fibers are cooled by drawing them through the center of a water-cooled heat exchanger (or chiller). The heat exchanger typically has a clam-shell type of design so it can be opened and then closed around the fiber after the start of the drawing process. The central tube or passageway (within the interior of the heat exchanger) surrounding the fiber can vary greatly with either a smooth interior surface or with numerous other more complicated surface structures or cavities designed to improve the heat exchange process between the hot fibers and the water cooled inner walls of the heat exchanger.
Pure (or relatively pure) Helium gas is also often injected into the central section of the heat exchanger in order to promote more efficient heat exchange between the hot drawn fibers and the cold inner walls of the heat exchanger. However, Helium losses associated with this process can be costly. In addition, before the drawn fiber enters the fiber inlet end of the chiller it is in contact with air and thus some pre-cooling of the hot fiber is accomplished by heat exchange between the fiber and the ambient atmosphere. As a consequence of the contact between the hot fiber and air, some air is “dragged” into the fiber chiller by the fiber and causes the Helium coolant gas stream to become contaminated.
This kind of contamination can and does decrease the efficiency of the fiber cooling process because the contaminated Helium is not as efficient as a heat exchange medium as is pure Helium. So, the Helium flow rate must be increased (wasting more Helium), or the Helium must be extracted from the chiller, purified, then re-cycled into the chiller in order to maintain the best possible performance as a heat exchange agent. All of this adds cost and complexity to the fiber cooling process. The present invention disclosure describes a novel technique and hardware solution that can be used to avoid all of the problems associated with the contamination, purification, re-cycling, and waste of Helium during the optical fiber cooling process.
SUMMARY OF THE INVENTION
This disclosure concerns a process and method of completely shielding the uppermost section of an optical fiber draw tower with an iner...