Patent GB-819179-A (GB)
Title: Improvements in the manufacture of laminated glass assemblies
IPC: C03C27/12
Filed: 1956-07-25
Abstract: 819,179. Laminating curved glass. PITTSBURGH PLATE GLASS CO. July 25, 1956 [Aug. 19, 1955 (2)], No. 22977/56. Class 140. A method of prepressing and/or pressing a curved laminated glass assembly comprising two matched sheets of curved glass and a thermoplastic interlayer, by removing air from between said sheets and sealing at least a narrow marginal area of the assembly, comprises enclosing the periphery and a narrow marginal portion only of the assembly with a fluid-impervious material in engagement with the outer surfaces of a narrow marginal area of the assembly and spaced from the periphery to provide a conduit, evacuating the conduit to remove air from between the interlayer and the glass sheets, and heating the entire assembly and the fluid-impervious material peripherally maintained thereon, said heating being carried out at an elevated temperature sufficient to seal at least the marginal area of the laminated assembly. As shown, a continuous channel-shaped member 11 surrounds the assembly comprising glass sheets 13 and 14 and thermoplastic layer 15 therebetween. Connected to member 11 is a tube 17 which is in alignment with a hole 18 provided in the outermost wall of member 11 so as to provide communication between the channel 19 of member 11 and conduit 20 of tube 17. The inner surfaces 22 of side flanges 23 of channel-shaped member 11 abut on to a marginal area of the laminated assembly and provide at least some degree of sealing engagement therewith. A sealing material, e.g. an aqueous solution of polyvinyl alcohol may be used to seal this joint. Tube 17 may be provided with a valve or may be made of material that can be sealed by pinching off. The channel-shaped member may be of rubber or of synthetic resin. In a modification, the channel-shaped member is of a fluid-impervious material that can be worked by hand into the desired shape, e.g. a plastic putty-like material such as a polyalkylene polysulphide type synthetic rubber. A porous material such as porous elastic tape is placed around the assembly at the periphery of interlayer 15, tube 17 is placed with one end abutting on to the porous tape, and the plastic material worked by hand around this junction and completely round the periphery of the plastic tape and into contact with the marginal outer surfaces of the laminated glass assembly to provide the channel-shaped member. In another form a porous elastic tape is mounted on a wider tape of the plastic material which may have a fabric backing. Before enclosing the assembly with the compound tape by folding the plastic tape over the edge of the assembly with the porous tape abutting on to the periphery of interlayer 15, a metal tube 17 is attached to the compound tape with one end abutting on to the surface of the porous tape adjacent to the plastic material. In a first method of operation, the assembly to be laminated is enclosed within the channel-shaped member and the conduit 19 is evacuated, and the entire assembly heated while vacuum is maintained. The pressing of the assembly is then completed in a fluid, e.g. oil or air, under pressure with or without the channel-shaped member still in place. When using oil, the channel-shaped member is removed and the laminated assembly edge-rolled as necessary in known manner before the treatment in the fluid. In a second method, the channel member is placed round the assembly to be laminated and the conduit evacuated as before. Tube 17 is closed by closing the valve in it, or by pinching off, and the vacuum source disconnected. A number of evacuated assemblies with channel members around them are placed on racks of a cart which is placed in an oven to heat and preliminarily bond the assembly. The assembly is then removed from the ovens, the channel member removed, and the laminate then edgerolled as necessary and autoclaved in known manner. In a third method the channel member is evacuated and tube 17 closed or pinched off as before, and the assembly with the channel member still around it is immersed in a fluid, e.g. oil or water, at elevated temperature and pressure to seal the laminate substantially throughout its entire area. Pressure is released after cooling. Another method is identical with the first method above except that the final pressing stage is carried out with the channel member still around the laminate and that the pressing fluid is a hot gas, e.g. steam or air, under pressure. After pressing the assembly is cooled while pressure is maintained, e.g. by displacing the hot gas by cooler gas at the same pressure, before releasing the pressure and removing the laminate. The channel member may remain in place on the finished laminate and may form a resilient frame for it.