NetComposites
3M

Filament UV Coating Process Improvement Receives Patent

04 October 2002

Fusion UV Systems, Inc. was recently awarded a patent for an apparatus which improves the UV coating process for filament type substrates such as optical fibers (including ribbon and coloring), industrial thread, wire, cable, and fiberglass filaments and rovings.

Bob Rhoades, inventor and Fusion UV’s fiber optic sales engineer said, “There are possible cost reductions for optical fiber production, fiber coloring and ribbon matrix applications. In addition, this apparatus may open up new markets for UV curing, especially those applications where previously reducing heat on the filament substrate was just too costly.”

In a typical filament UV coating process the filament passes through a quartz tube in the UV cure zone, which prevents air impingement on the fiber and provides the envelope for a nitrogen atmosphere. It is desirable to reduce the amount of heat, which is infrared (IR) heat generated by the UV lamp, on the filament itself. Others have tried various methods such as dichroic coatings and water jacketing of the quartz tubes, but these methods are all very costly. Over time the inside surface of this quartz tube becomes cloudy from the off gassing and “smoking” during the cure. So these quartz tubes must be cleaned on a regular basis. A dichroic coating on the quartz tube is effective for heat reduction, but expensive because the dichroic coating will not withstand the aggressive cleaning process.

Fusion’s new patent improves on this process by simply installing a separate dichroic coated quartz tube over the production quartz tube as shown in the diagram. Now this inner quartz tube can be changed every shift in normal production and cleaned for re-use. The outer coated tube remains in place since it is not exposed to the normal outgassing or “smoking” of the curing process.