Patent GB-1430255-A (GB)
Title: Process and apparatus for the manufacture of a multiple glazing
IPC: B32B17/10
Filed: 1973-07-25
Abstract: 1430255 Laminating method and apparatus GLAVERBEL-MECANIVER 25 July 1973 35382/73 Addition to 1368785 Heading B5N A process for forming a laminate by heating an assembly comprising at least two sheets 7, 8 of glass or vitrocrystalline material and one or more intervening thermoplastic layers 9, e.g. of polyvinylbutyral, between the or each adjacent pair of sheets to soften or melt the said thermoplastic layer(s) and exposing the assembly to heat and pressure conditions such as to cause the said sheets to become firmly bonded by means of the thermoplastic layer(s) wherein there is applied to the assembly means 10 which envelopes at least the edges thereof, to define with the edges, a space around the edges in which sub-atmospheric pressure can be created for subjecting the inter-sheet spaces to suction at said edges, and wherein the assembly is subjected in a preliminary treatment stage, before it is subjected to said firm bonding conditions, to sub-atmospheric environmental pressure acting upon at least one of the main external faces while the assembly is subjected to heat in a treatment chamber and the intersheet spaces are subjected to said suction produced by sub-atmospheric pressure within the space around the edges of the assembly is characterized in that a temperature differential exists between the central and the marginal regions of the assembly during at least a first part of said preliminary treatment stage. An apparatus for use in forming a laminate and comprising at least two chambers into which an assembly of sheets for forming a laminate can be introduced in succession, at least one of the chambers being associated with means for producing sub-atmospheric environmental pressure therein, means for conveying an assembly from one chamber to another, sealing means for enclosing the edges of the assembly to define a space around such edges and associated with means for producing a sub-atmospheric pressure in the space around the edges for subjecting the inter-sheet spaces to suction while the assembly is in a said chamber at sub-atmospheric environmental pressure, and means for heating the assembly according to a predetermined schedule is characterized in that the said heating means comprises at least one heater and heat control means so arranged that during at least a first part of the heating period, heating can be substantially confined to or mainly performed in the central or marginal region of the assembly in a said chamber at sub-atmospheric environmental pressure, and that the action of the heat can be subsequently extended to the other of those regions. The central region is preferably heat-insulated to keep it at a temperature lower than the temperature at which the plastics material starts to soften and stick to the glass or vitrocrystalline sheets. Advantageously, a number of assemblies supported edgewise and sufficiently close together to ensure that the heat supplied to the treatment space is at least initially substantially confined to or mainly acts on the marginal regions of the assemblies, are subjected to the preliminary treatment together. In an embodiment of the invention, one or more refractory screens is or are used to screen the central region(s) of the assembly (assemblies) from the source of heat, heating being preferably effected by radiant heaters. The drawing shows a treatment chamber 1 for effecting the preliminary treatment, the treatment chamber being provided with a roller conveyer 2, radiant heating elements 3, 4 and vacuum pump 5. In operation, a plurality of assemblies 6 are disposed vertically side-byside on a frame 11 resting on the conveyer 2, each assembly being provided with an endless tube 10 fitted over its peripheral edge and connected by conduit 14 and duct 15 to a vacuum pump. Heat from the heating elements 3, 4 acts directly on the marginal regions of the assemblies 6, screens 17 and 18, e.g. of asbestos fabric or glass sheeting, being provided to shield the central regions of the outer faces of the assemblies from the action of heat. The chamber has mounted therein two fans 19, 20 driven by electric motors and disposed below the frame 11  so that when the fans are switched on they maintain currents of air upwardly between the assemblies and between the end assemblies of the group and the screens 17 and 18 to extend the heating over the whole of the surfaces of the assemblies.