Patent GB-892607-A (GB)
Title: Method and apparatus for polishing glass ribbons
IPC: B24B7/26
Filed: 1959-11-09
Abstract: 892,607. Polishing glass ribbons. PITTSBURGH PLATE GLASS CO. Nov. 9, 1959 [Nov. 12, 1958], No. 37871/59. Classes 55 and 60. A method of polishing a moving ribbon of glass comprises passing the ribbon 11 between a plurality of sets of opposed surfacing means 14, 14<SP>1</SP>, Fig. 1, establishing confined paths of fluid flow in contact with the upper and lower surfaces of portions of the glass ribbon defined in part by the periphery of the surfacing means, and supporting said portions of the glass ribbon by the net upward force exerted by said fluid paths. Two initial sets of polishers 14, 14<SP>1</SP> are followed by two sets of rouge polishers 15, 15<SP>1</SP>, suitable slurries being fed from tanks, 16, 18 and discharged to tanks 17, 20 as shown in Fig. 1. A grinder 12 and the groups of polishers are separately moveable laterally into maintenance bays by a rack and motor-driven pinion (Fig. 2, not shown). Vertical adjustment of the driving spindles, 21, 22 of the upper and lower runners of the polishers 14, 14<SP>1</SP> is affected respectively by a motor-driven worm gear 60, 61, Fig. 3, and by sprocket-driven screws 76, Fig. 4, the spindles being oppositely rotated by motors 40, 72, through worm gears 52, 53 and 84, 85 respectively. Upper and lower squeegee units 94, 95, are provided on each side of the runners each polishing station being defined by pairs of ribbondriving pinch-rolls 96, one pair at each side of a runner; conventional conveyer-rolls support the glass between polishing stations. Each rubberlipped and spring-biased squeegee unit is carried by a beam 100 which is moveable transversely for maintenance of the unit pneumatic pistons within the beams 100 withdrawing the squeegees from the glass surface prior to removal. A drainage trough 90 collects surplus polishing slurry and discharges it to a sump, this fluid having been supplied to the hollow spindles 21, 22 by feed pipes 23. Liquid similar to that supplied through the pipes 23 is fed to the areas within the runners 14, 14<SP>1</SP> through manifolds 103, and washing and cooling water is supplied just outside these areas through manifolds 104; separator members 93, Fig. 4, located beneath the squeegees ensure that excess cooling water is drained separately from the polishing fluid. Each runner of each polishing unit 14, 14<SP>1</SP>, carries an annular concentric facing 110, Fig. 7, preferably of felted animal hair backed by a sponge-rubber or like resilient disc 111 having a central opening from which the fluid is fed, through the space between the disc and glass 11, to radial grooves 113 in the annular facings 110 which are so dimensioned that their inner diameters exceed the width of the glass ribbon. The spaces between the polishing felts 110, where they are not in contact with the glass surfaces, are occupied, for fluid-confining purposes, by two plates 120 at each polishing station, their inner edges 124, bridging the entire overhang of the upper and lower runners beyond the width of the ribbon. Each plate 120 is provided with a splash shield 125 and is adjustably supported by a longitudinal member 121 so that the edge 124 has a small clearance from the adjacent edge of the ribbon 11. Sagging of the ribbon between the annular polishing surfaces is prevented by the net upward force of fluid. Figs. 10 and 11 show a modification in which the plates 120 are replaced by fluid seals, an arcuate channel member 128 bearing against each pair of overlapping runner edges and having sealing members 131, 132 of elastic acid-resistant material urged into contact with facings 139, of similar material, on the runner peripheries, by spring-loaded supports 138 located between the arcuate members 128- and the fixed members 121; a plurality of feed pipes 136 connect the sealing zone with the source 16 of fluid, the pressure of which may be adjusted either to throttle, reverse, or to balance the outward flow of fluid from between the polishing felts. Each of the runners 15, 15<SP>1</SP> at the rouge polisher stations is driven by a hollow shaft, by means similar to those used for the polishers 14, 14<SP>1</SP>, and incorporates a conventional spider supporting a plurality of felt-faced discs of small diameter relative to the runner periphery, about which they are mounted for free rotation on stub-shafts. Rouge is fed from the centre of the spider to the glass surface ahead of each runner face by supply pipes or hoses having flattened outlets or, alternatively, it may be supplied from the central reservoir to the centre of each polishing disc through pipes leading axially into the hollow stub shafts. Supports for the glass, coaxial with the driving spindles, are provided at the centre of each pair of rouge polishing runners; these supports are in the form of a further pair of polishing discs having sponge rubber or like facings with rounded edges and central openings into the rouge reservoir. The rouge slurry is not supplemented by flooding from outside manifolds, as described with reference to the polishers 14, 14<SP>1</SP>. The fluid supplied to the polishers 14, 14<SP>1</SP> comprises 5 parts by weight of hydrogen fluoride, 45 parts potassium bifluoride, 100 parts water and 140 parts sugar with 1 %, by weight of the solution, of chromic oxide.