Patent GB-567835-A (GB)
Title: Improvements relating to the formation of integral molded structures from fibrous sheet material
IPC: B32B27/00
Filed: 1942-03-24
Abstract: 567,835. Shaping wooden articles by pressure. STEVENS, A. H. (Vidal Research Corporation). March 24, 1942, No. 3912. [Classes 145 (i) and 145 (ii)] [Also in Groups VIII and XXXIII] A process for forming integral moulded structures from fibrous sheet material, such as wood veneer, which can be applied to the manufacture of radio cabinets, aircraft, hulls of ships, or furniture, consists in the superposing of a group of sheets and one or more interposed layers of adhesive upon a mould, together with one or more reinforcing members, and pressing the whole into contact with the mould by means of fluid pressure applied through a flexible membrane and maintained until the adhesive is set. As shown in Fig. 2, a radio cabinet may be made by coating sheets of veneer with a thermoplastic adhesive, preferably polyvinyl butyral. Coated sheets are then laid bodily on one another on a mould which is formed with channels 43 in which the reinforcing members, such as wooden strips 42 coated with adhesives, are placed. Other grooves 40d are formed in the mould to prevent the formation of wrinkles in the finished article. The sheets are made to conform to the mould by clamps, elastic bands or other suitable means. The sheets may also be held in position by spot-welding them to one another by means of a hot iron or by spots of solvent applied to the adhesive. The sheets are punctured by a sharp-pointed tool to prevent the formation or air blisters, and the sheet of non-adhesive material is placed over the assembly. Finally, the sheets are pressed, preferably by enclosing the assembly in a fluidtight container 45 such as a rubber bag which is placed in an air-tight drum 46, and submitted to heat and pressure. The air pressure and the temperature in the container is increased to bond the sheets tightly around the mould. After a time, the mould is allowed to cool and the finished product is removed. When bolts are to pass through the finished article, resincoated metal washers may be placed between the laminations during assembly ; hinges may be attached similarly. This method can be used for making an aircraft, the body and wings being made in separate moulds and subsequently united to one another by coating the compacting parts and submitting the joint to heat and pressure. Each wing may be made as a shell with internal longitudinal and transverse ribs to which the shell is united as described above. The wing may be made in longitudinal sections which can be joined to one another mechanically, but preferably it is made up of a number of separate sections or cells as in Fig. 5, each comprising a skin 51b, 52b, 53b, Fig. 6, reinforced by laminated side ribs 51a, 52a, 53a, respectively. These parts are joined by adhesive in the manner described to a pair of resin-coated beams 53, preferably of wood, which extend the full length of the wing. A beam may be formed, however, by shaping coated laminations around a core or mandrel in the manner described. The core is so constructed that it can be withdrawn from the finished hollow beam. Reinforcing strips of wood may be placed under any desired part of the laminations before they are submitted to heat and pressure. The core may have transverse channels which receive strips of resintreated veneer that become joined to the finished beams to form ribs 68, as shown in Fig. 16. In a modification, reinforcement is in the form of bulkheads which extend across the interior of the beam. Similarly, the fusilage is made in sections or moulds and is provided with reinforcing members 140, Fig. 32, which may be transverse and longitudinal or extend helically around the body. The body is formed by applying resin-treated laminations to a mandrel and submitting this to heat and pressure as described.