Patent GB-1380829-A (GB)
Title: Vacuum press and method of bonding
IPC: B30B5/02
Filed: 1972-04-10
Abstract: 1380829 Laminating press and method SEAL Inc 10 April 1972 [8 April 1971] 16457/72 Headings B5N and B5F A vacuum press for bonding materials together under heat and pressure comprises a base with a horizontal work support assembly 2 including a frame and a flexible air-impermeable sheet 34 supported at its edges by the frame, a platen assembly 4 mounted for movement into and out of engagement with the work support assembly, the platen assembly including a flat platen 82 and heater means for heating the platen, the platen assembly and the work support assembly when engaged providing an air-tight work-receiving chamber therebetween with the platen and flexible sheet forming opposite side walls of the chamber, means, e.g. vacuum pump 42 for evacuating the chamber so that the atmospheric pressure exterior of the chamber will force the flexible sheet towards the platen to compress a workpiece supported on the sheet, and control means for operating the heater means and the evacuating means to that a workpiece in the chamber is heated and compressed. The frame is made of identical upper and lower sections secured to each other and each made up of four U-shaped channel members, and supports on rigid bars 28 a stiff plate 32, e.g. an asbestos sheet. The flexible sheet 34 which has its edges clamped between and supported by the upper and lower frame sections may be made of natural or synthetic rubber, e.g. silicone rubber, plastics or a rubber or plastics coated fabric, rests in its relaxed condition on plate 32. A peripheral seal member 40 made of silicone rubber is attached to the upper surface of flexible sheet 34. The platen assembly, which may be mounted for pivotable movement on a hinge, comprises a rectangular frame 61, a cover member 72 consisting of two thin plates 74 and 76 secured to an intermediate honeycomb reinforcing structure 78 and a flat metal plate 82. The heater means preferably comprise three separate electrical heating units 90, 92 and 94 so that the heat input to the edge regions of the platen exceeds the heat input to the centre region to compensate for radiative heat losses at the edges of the platen and maintain the platen at a substantially uniform temperature. A method of bonding materials together under heat and pressure comprises placing on the air-impermeable sheet of the above press a workpiece that comprises in superposed relation at least a laminating film and a graphic arts object or a graphic arts object, a dry mount tissue and a substrate, positioning the platen over the workpiece so that the platen and air-impermeable sheet form a closed work chamber containing the workpiece, evacuating the chamber and concurrently heating the workpiece by transfer of heat from the platen so as to effect removal of free moisture and so that the workpiece is drawn up tight against the platen under a pressure determined by the difference in pressure between the pressures exterior and interior of the work chamber, thereafter increasing the temperature of the workpiece to bond together the components thereof, and thereafter opening the work chamber and removing the bonded workpiece. In effecting the method, the removal of moisture may be facilitated by placing a porous fibrous mat on the flexible sheet. The graphic arts object is preferably a photograph. The laminating film may be an adhesive coated transparent polyethylene terephthalate film. The substrate may be cardboard or a composite hardboard.