Patent GB-1429343-A (GB)
Title: Shaping of glass to a desired form
IPC: C03B7/14
Filed: 1973-03-05
Abstract: 1429343 Shaping molten glass PILKING- TON BROS Ltd 20 Feb 1974 [5 March 1973 26 March 1973 8 Aug 1973] 10640/73 14490/73 and 37641/73 Heading C1M In the shaping of glass to a desired form, molten glass is delivered on to a porous support member while feeding a gas under pressure through the support member from the reverse side so as to support the molten glass out of contact with the support member on a cushion of gas while the glass assumes a shape approximating to that of the support member under the forces of surface tension, gravity and gas cushion pressure, the glass being cooled while thus supported to a temperature at which it can be shaped by contact with a solid surface without any substantial surface damage and the conditioned glass is then shaped by a process involving contact with a solid surface. As shown in Figs. 1 and 2, a rotary turret 10 on pedestal 11 is indexed by an hydraulic or pneumatic ram 12 so that porous support receptacles 14 mounted on the turret are indexed from a delivery station D at which molten glass is delivered from a feed tube 17 to a transfer station T at which the partially formed glass is transferred to a shoot 44 for delivery to a mould (45). At station D, a gate 19 is provided immediately below orifice 18 and comprises shears like members 20, 21 drawn apart by mechanism 22 to provide a circular aperture through which the molten glass flows when opened. The porous receptacle 14 is mounted in a bracket 16 at the outer end of a horizontal radially extending arm 15 by means of a screw threaded ring 24 engaging a ring shaped part 23 to which a metal dish 25 is secured to form a plenum chamber 26. Chamber 26 is connected by a pipe 27 and hollow parts 28, 31 in bracket 16 and arm 15 to a central chamber 32 in turret 10 and thence to an inlet 34 for a supply of nitrogen or other gas. Each arm 15 is rotatable about its own axis to tilt the receptacle 14 at the transfer station T, arm 15 carrying a pinion 37 to mesh with a vertical rack 38 moved up and down by a vertical ram (42). In a modification (Figs. 6 and 7, not shown) the receptacle 14 is mounted directly on the turret table (120) by a slidable member (121) with a dovetail slot (122) to engage the top of a ram (124) at the delivery station D, so that the receptacle 14 is raised to immediately below gate 19 and lowered slowly till the glass flow is cut off by the members 20, 21. A tunnel enclosure is also provided for the receptacles 14 between the stations D and T for reducing the temperature gradient in the glass in the receptacle 14, and in place of tilting the receptacle 14 at station T, a vacuum take-out means is provided comprising a suction casing (132) on an arm (133) pivoting about a horizontal rotary joint (134) having a gear (136) meshing with a rack (137) at station T movable vertically by a ram (138) to invert the casing 132 over the shoot (141) at which point the vacuum to the casing 132 is released. As shown in Fig. 8, vacuum take-out means 132 positions the gob directly under a mould 147 at mould station M, the casing 132 being mounted to an arm 145 to swing horizontally about axis 146 which can be raised and lowered as well as rotated, the arm 145 also being rotatable about its own axis to invert the gob. The casing 132 is lowered on to an anvil 149 and the gob pressed to final shape by operation of ram 148 and mould 147. On lifting of the mould 147 with the finished article, a shoot 150 is positioned below the mould and on to which the article is ejected, to pass via a conveyer 152 to an annealing lehr 153. In a further embodiment, a moulding station M is provided between the delivery stations D and a transfer station direct to the annealing lehr, so that the receptacle 14 itself forms the mould. The bottom only of the receptacle may be porous, or the gas flow may be concentrated near the bottom of the receptacle, the gas rising up the walls to support the molten glass. As shown in Fig. 18 for the formation of glass ribbon by rolling, the porous support member 91 is channel shaped with a slightly concave bottom surface 92, shallow side walls 93 an end wall 94 adjacent a spout 90 for molten glass and has a plenum chamber 96 fed by pipe 97 with nitrogen gas and cooled by pipes 98. A ribbon 99 of glass is formed in the channel 90 on a cushion of gas while being cooled to the required temperature, when it passes to the nip of temperature controlled, polished rollers 95. To prevent sagging due to a relatively hot interior of the ribbon, heaters 100 may be provided to re-heat the surfaces and the ribbon passed to a further pair of temperature controlled polished rollers 101 and thence to an annealing lehr 102. Materials suggested for the porous support members are sintered, powdered stainless steel, nickel or nickel-copper alloy graphite or sintered silicon carbide or other porous refractory ceramic. The gas can either be pure nitrogen or a mixture with about 5% hydrogen and is delivered at a pressure of from 1 to 30 lbs./square inch, depending on the heat and thickness of the porous member. The gas may be heated. The invention is particularly useful for glasses having a low viscosity at the liquidus temperature.