Patent GB-699246-A (GB)
Title: Filmed and strengthened glass and method and apparatus for producing
IPC: C03B27/052
Filed: 1950-11-07
Abstract: 699,246. Glass filming and strengthening. LIBBEY-OWENS-FORD GLASS CO. Nov. 7, 1950 [Nov. 10, 1949], No. 27137/50. Class 56. Glass sheets or plates are filmed and strengthened by heating the sheet &c. to substantially the softening point of the glass and then spraying one side of the hot sheet with a film forming fluid to chill and film that side while simultaneously directing a chilling' fluid against the opposite side. The glass sheet 22 supported through a slot in the furnace roof by tongs 21 and link 20 from a wheeled carriage 19 movable along the monorail 16 is first heated to substantially its softening point in a furnace A which may be fitted with electric resistance heaters and baffles and then held between the aligned cooling apparatus D and filming apparatus C. The filming device C comprises a bank 25 of spray guns which are reciprocated in a plane parallel to the plane of the glass by a frame 26. The latter includes two pairs of vertical bars 27, 28 pivotally mounted on shafts 29 carried by bearings 30 from the framework 31, 32, and tied at the lower ends by a shaft 33 journaled in bearings 34 on the bars; the two pairs of bars being tied by a platform 35 supported in bearings 36 from the shafts 33. A rod 37 from the platform 35 supports the spray guns 38 which are adjusted by means of clamping collars 39. For reciprocating the frame 26, motor 40 drives a gear reducer 43 which has an eccentric 45 keyed to the driven shaft 44, the eccentric drives a crank plate 46 mounted on an axle 47 by means of a rod 49 secured at one end to the lower periphery of plate 46 by pin 50 and at the other end to the eccentric 45 by pins 51, and the crank plate 46 drives the frame by means of a rod 54 secured at one end to the upper perimeter of plate 46 by pin 55 and at the other end by a yoke and pin 56 to the end of a cross link 52 on bars 27. The amplitude of the movement may be adjusted by fitting pin 55 into other holes 57 in plate 46..The cooling device comprises exhaust chamber 58 with a stack 59 leading to the exhaust means and openings 60, 61 in which a horizontal open ended casing 62 is arranged opposite the spray guns, a plate 63 closing the remainder of opening 61. At the forward end the casing 62 has a wall 65 with a portion 66 parallel to the walls of chamber 58, and a rearwardly sloping portion 67 which enters chamber 58. A similar wall 68 is secured in spaced parallel position to wall 65 by blocks 69 to form a passageway 70 to the interior of chamber 58, and a cover plate 72 is fitted. A plurality of spaced vertical cooling pipes 74 connected to a header 75 and held together by a strap 76 are positioned adjacent the forward end of casing 62 and mounted on flexible rods 77, the latter being secured at the rear to blocks 80 in the base 73 and at the front to a shaft 18 slidable in brackets 79. The pipes are reciprocated by a motor 81 which drives an eccentric 84 through a gear reducer 82, the eccentric being connected by a rod 86 to one end of a bell-crank 87 which is slotted at the other end 90 to surround a pin 91 on shaft 78. The flexible rods 77 act as spring levers to accelerate the reversal of movement of shaft 78. The links 20 are movable laterally in slots in the supporting plate 92 so that the links can pass through slots 96 and the sheet 22 through the opening 97 in the wall 68 to position the sheet between walls 65, 68. A lapse of several seconds is allowed between the removal from the furnace and the commencement of cooling &c. With the sheet 22 in position motor 81 is started and simultaneously compressed air is fed to the header 75 through a flexible conduit 98, to be fed through spaced openings 99 in the pipes 74 to chill the rear surface. At the same time or immediately afterwards motor 40 is started simultaneously with the turning on of guns 38 by admitting air through pipes 100 to a cylinder 101 of each gun to retract piston rod 102 of the spring closed needle valve, when air under pressure passes through pipes 103 to atomise the spraying liquid fed through pipes 104 from container 105, and form the spray. The wall 68 and cover plate 72 are readily replaceable so that a desired opening 97 of the same shape but slightly larger than sheet 22 can be used. As air is exhausted from chamber 58 through stack 59 a draught is set up through.the passage 70 to create an air stream at all four sides of the glass sheet, as shown in Fig. 5, which immediately removes any surplus spray, and because sheet 22 substantially closes the opening 97 a stream of air is pulled in through the opening in casing 62 against the rear surface of the glass, preventing the formation of a film on that surface and.chilling the latter even when pipes 74 are not used. It is preferred, however, to use pipes 74 with or without the exhausting streams. The links 20 are then moved to the middle of the carriage and the glass removed. The working data of an example is given. Electrically conducting films may be formed by using solutions of tin halides or vapours such as SnCl 4 , SnI 4 , or SnBr 4 . Cooling fluids other than air may be used, e.g. steam, oil, and mists of water / oil emulsions. The. glass sheet may be used to form a laminated sheet. The two surfaces of the sheet may be equally chilled to give a glass substantially the same as fully tempered glass, but if required the rear surface may be chilled to a greater degree, e.g. by varying the temperature or volume of cooling air or the time of spraying. In an example such glass formed into a laminated sheet for use in a pressurised airplane is said to be mechanically stronger than finely tempered glass under the same conditions. Stress diagrams of differently treated glass sheets are given. Specification 632,256 is referred to.