Patent GB-1102818-A (GB)
Title: Improvements in or relating to light polarizers
IPC: C03B37/025
Filed: 1965-03-09
Abstract: A method of producing a light polarizer comprises applying heat to adjacent cross-sectional portions of a glass sheath having one or more longitudinal bores containing a metallic substance so as to soften the sheath and melt the metal and concurrently applying a given tension on a leading edge of the sheath thereby to draw it out and reduce the diameter of its bores thus forming an integral unit including an appreciably extended sheath having one or more continuous attenuated metallic cores, the unit then being cooled and solidified and subsequently cut into a plurality of shorter sections, a plurality of which are then assembled in side-by-side parallel relationship.  A glass tube 14, mounted in a clamp 52 and with one end 14a sealed off, is continuously fed with slugs 18 of a metal. The clamp 52 is attached to one end of a rack 42 which is advanced by a pinion 40 driven at a given speed from a variable speed box 34 in turn driven by a variable speed motor 20, which also drives a winding on drum 70 for a wire 74 attached to the closed end 14a of the glass tube 14.  A series of bell-crank levers attached to the drum shaft 78 and to the drum 70 move a gas burner 56 along the line of draw and cause the glass tube and its metal core to be attenuated. To ensure that no breaks occur in the metal filament core a vibratory means 48, e.g. electromagnetic or ultrasonic, is attached to the free end of the rack 42 and causes dissipation of <PICT:1102818/C1/1> any gas bubbles which may arise as the metal core melts.  The attenuation causes an elongation of twenty-five times.  The filament thus produced is cooled and cut into a plurality of equal lengths.  A number of these lengths, mounted in side-by-side relationship on a glass plate of the same composition as the glass tube, are held in place by clear bees-wax or a glass solder and have their ends sealed before the composite element is further attenuated. A similar machine to that described above is used, except that the attenuated metal cored rod is drawn on a rubber-surfaced stainless steel conveyer belt (161) (Fig. 4, not shown), which is led over a flat surface (192) and thence round an idler roller (162) which is adjustable to vary the tension on the belt.  To ensure the melt cored filaments fuse to the glass base-plate after passing over the burner they pass under a carbon roller (196).  The attenuated strip is then also cut into a plurality of equal lengths, a number of which, are mounted in side-by-side relationship on another glass base-plate.  This composite unit is then firstly placed in an oven where it is heated and compressed, equally in all directions, to form a compact unit. This unit is then attenuated as above and the process repeated until a final unit is formed having the required density and size of metal filaments. At the final sealing after heating and compressing the unit is carefully annealed.  The final unit may be of rectangular shape, convex-concave, or have a convex glass cover placed on top thereof to form a lens.  For controlled heating of the glass tube or composite elements a carbon baffle is placed beneath them on the attnuated side of the burner 56.  The gas burner 56 may be replaced by an electrical radiation system.  The glass used may be either a borosilicate or a potash-soda-lead glass, or it may be quartz glass. The metal for the core may be an alloy of any of a given combination of lead, tin, bismuth, antimony, silver, platinum, palladium, indium and gallium.  In the final composite element the spacing and cross-section of the metallic filaments should be substantially similar throughout their length and should be of the order of 0.005 to 0.05 micron.  It is possible to commence the process with a glass element having a plurality of equally spaced longitudinal bores which can be filled with metal, this unit then being drawn out on the apparatus of Fig.4.