Patent GB-884920-A (GB)
Title: Apparatus and method for metal adhesive bonding
IPC: B29C65/00
Filed: 1958-07-03
Abstract: 884,920. Making aircraft components; jointting; stamping. GEIGER, R. F. July 3, 1958 [Aug. 1, 1957], No. 21356/58. Classes 83 (2) and 83 (4). A method of bonding a plurality of members together with a pressure-temperature-curing adhesive comprises applying the adhesive to a surface of one of the members and assembling the members, applying and maintaining uniform heat and pressure to the adhesive to cure it while maintaining a zone about the adhesive at sub-atmospheric pressure to effect removal of the volatiles formed between said members during the curing of the adhesive, subsequently cooling the adhesive and relieving said pressure when the adhesive has solidified, said pressure being transmitted by a confined compressed multiplicity of free-flowing balls on a surface of one of the members, the spaces between such balls being sufficiently great to maintain a uniform fluid-pressure throughout the space occupied by said balls. The balls are solid or hollow and made of glass, plastic, wood, metal, e.g. steel, brass or aluminium, or other hard material and in some applications sand. Apparatus for carrying out the method consists of a table 14 on which is mounted a ballretaining ring 15 within which the components to be bonded, e.g. a metal sheet 10 and stiffeners 13, are supported on a perforated aluminium sheet 20. An elastic blanket 16, e.g. of rubber, mounted on a rack 17, is lowered to cover the balls in the retaining ring. The sheet 10 is held flatly on the perforated sheet 20 by a vacuum applied through pipes 21 (Fig. 3), and tubes 22 in the table 14 circulate either a heating or cooling fluid. Heating may be effected electrically by passing an electric current through the balls. A vacuum is applied to the underside of the blanket 16 through a pipe 24 to effect blanket pressure on the balls and to exhaust solvents and polymerization products liberated during the curing of the adhesive and thereby preventing air pockets. Additional pressure is applied to the blanket by a compressed-air dome 25. In another embodiment for bonding stiffeners 13 and doublers 12 to a curved skin 10B (Fig. 8), the skin 10 is held on the platen 36 by a vacuum applied through pipes 37 and pressure is applied to the balls 23 by a blanket 16 over which is arranged a pressure dome. In a further embodiment doublers 39 and stiffeners 40 are bonded to a cylindrical sheet 10C (Fig. 10). The platen 41 may be in one piece or in sections and the sheet is held in position by vacuum pipes 42. The platen is covered with an elastic blanket 44 and when a vacuum is applied to the ball-filled container through pipes 45 the blanket subjects the balls 43 to atmospheric pressure which is in turn transmitted to the components to be joined. The sheet 10 may have an hour-glass configuration as shown in Fig. 11. In a modification (Fig. 13) the blanket 52 is tubular and is stretched over a cylindrical wire frame 53. Additional pressure may be supplied to the blanket 52 by introducing compressed-air through a pipe 62. In another embodiment a plurality of table top platens 63 (Fig. 15), are mounted on a pressure cooker 64. Pipes 65 provide a vacuum under the blankets 67 and pipes 68 a holding vacuum for the metal sheet. Heating and cooling of the cooker is effected by a radiator 70 connected to a heating and cooling source 71. The platens may be mounted on a trolley and wheeled into the pressure cooker. In a still further embodiment, in the manufacture of an aircraft elevator, sheet metal skins 79 and 79<SP>1</SP> (Fig. 20), are bonded to a honeycomb structure 80 and also to a structural member 82 having a curved portion 83. More pressure is applied to the curved portion 83 of the structural member than the honeycomb structure by the provision of a floating block 84 the top area of which is greater than the opposing area 92 which engages the curved portion 83 of the top skin. The balls 86 are the same size or smaller than the core of the honeycomb 80 to ensure a uniform pressure along the joints and the platen 81 is heated and cooled by coils 87.