GB1062835A - Improvements in or relating to glass fiber light-transmitting devices - Google Patents

Abstract

<PICT:1062835/C1/1> <PICT:1062835/C1/2> <PICT:1062835/C1/3> A glass fibre light-transmitting device comprises one or more long and slender fibres 16, Figs. 5 and 7, or 41, Fig. 9, each having a core 18 or 411 of glass of relatively high refractive index surrounded by a coating 19 or 42 of glass of lower refractive index, the device having a cross-sectional configuration of a re-entering polygon formed by a pair of spaced, oppositely disposed, substantially plane parallel sides joined by a pair of re-entrant V-shaped sides disposed with lines of their respective apices extending between the first sides in a plane parallel thereto. The single fibre 16 may be formed by dipping a circular core rod into the coating glass to give an all-over coating, the coated rod then being passed through a heating coil to driven rollers 22, Fig. 5, with V-shaped ridges 31, 32 to form a butterfly shape. The rollers 22 are mounted on blocks 25, 26 for movement towards and away from each other and are heated as by coils 33, 34. A plurality of the fibres 16 may then be packed together as in Fig. 7 in a metal, ceramic or carbonaceous support 35 heated by a coil 37, the rods 16 being pressed down by a cover 38 and the assembly fused together. The fused assembly may then be reheated and passed between rollers similar to rollers 22, these steps being repeated as required to form multifibres of the required fineness. With extremely fine multifibres, there may be flexibility of the fibre and this feature may be utilized in aligning the bunched ends of a plurality of multifibres with elements of an associated optical apparatus or in slowly heating a group of multifibres to allow them to be simultaneously shaped or curved intermediate their ends. For light transmitting devices of large area, groups of multifibres may be secured together at one or both ends or throughout by cement or by fusion, the end surfaces being optically finished as by grinding, polishing or immersion in a liquid of like refractive index. As shown in Fig. 9, a multifibre device of the butterfly shape is formed from a plurality of initially round rods 41 packed with a support 43 having a recess 44 which, with a shaped plunger 49, is of butterfly shape, the support 43 and plunger 49 being heated by coils 53-56. The heat and controlled pressure from plunger 49 causes the rods 41 to coalesce and the coatings 42 to fuse together, the resulting butterfly-shaped structure being drawn down to fibre size by gravity or rollers as with fibres 16.