Apparatus for producing continuous round jacketed lightguides

Claim 1

Apparatus for protectively jacketing optical filaments of a first polymeric material with a second polymeric material whereby the first material is exposed for only short duration to elevated temperature and which protectively jacketed product has a substantially uniform diameter, said apparatus comprising means for introducing said second polymeric material to a melt reservoir, a melt reservoir, a die orifice, a tubular filament guide member comprising an inner axial member and an outer member forming an inner chamber surrounded by a concentric outer chamber, said melt reservoir containing therein said tubular filament guide member axially disposed with said reservoir and spaced from said die orifice, said tubular member on the end disposed toward said orifice having converging configuration on its exterior surface, and the inner walls of said melt reservoir in the region of said orifice forming a converging surface, the converging surfaces of said reservoir and said tubular member forming a converging annular passage for the flow of said second polymeric material, the inner surface of said tubular member disposed to receive optical filamentary material from outside said chamber at its end opposite to that disposed to the die orifice and the inner surface of said tubular member disposed to receive and discharge cooling gas, the end of said tubular member disposed toward said orifice being spaced therefrom in an amount defined by a Y factor 6 to 40 percent, where Y ((bundle O.D. - tubing I.D.)/bundle O.D.) X 100 said orifice having a land of from 0 to 20 mils, whereby the second polymeric material passing around said tubular member flows about polymeric optical filaments of said first polymeric material in the space between the end of tubular member and said orifice before being extruded through said die to form a protectively jacketed lightguide of substantially uniform diameter.