GB665673A - Method of and apparatus for making improved wood products - Google Patents

Abstract

<PICT:0665673/III/1> <PICT:0665673/III/2> <PICT:0665673/III/3> <PICT:0665673/III/4> A method of producing laminated sheets as in 665,762, [Group XXIII], comprises applying a mixture of discrete wood particles of sanderdust and/or sawdust and synthetic thermosetting resin to at least one surface of a plywood panel, compacting the mixture and bending it to the plywood panel by heat and pressure from a smooth metal plate and subsequently stripping the plate off, the mixture being in sufficient quantity to form a skin <PICT:0665673/III/5> <PICT:0665673/III/6> coating of less thickness than the plywood panel but such that the inner side of the coating fills defects in the panel and the outer side presents a smooth surface. In one form of apparatus for carrying out the above method, Fig. 2, a conveyer 28, consisting of four parallel belts, has metal plates 38 from a stack laid on it with their ends contiguous. Aggregate is mixed in a revolving blade mixer 10, having suction and/or heating means to reduce the moisture content of the mixture, and spread on the plates by a shoot 23, the thickness of the layer being varied by vertical adjustment of the lower end of the shoot. The excess mixture is removed by a smoothing roller 40 and returned by a transverse belt 55 to the hopper 58, Fig. 1 (not shown) for re-use. Wood sheets are then laid on the smoothed mixture from a stack 65 with their margins in registry with the metal plates and the assemblies so produced transferred at the foot of the line to a hot press 70. After removal from the press the metal plates are stripped and their surfaces dusted with talc or oil to prevent adhesion of the synthetic resin. Alternatively, the wood sheets may be laid on first from the stack 38, the mixture spread on and covered with metal plates from the stack 65. In another method of operation of this apparatus the stack 65 is eliminated and the stack 38 consists of alternate wood sheets b and metal plates a which are laid on the conveyer in pairs, Fig. 8, the mixture c then being laid on and smoothed and the resulting assemblies stacked. The stack is then subdivided into smaller units x, Fig. 9, which are passed to the hot press. Alternatively, pairs of metal plates and wood sheets may be laid on the conveyer alternately, Fig. 10, the mixture spread on and the assemblies stacked and subdivided as before. Using this method to coat wood sheets on both sides, Fig. 12, the wood sheets alternate on the conveyer with pairs of metal plates of one-half thickness and the procedure is carried out as above. In another form, a panel having both sides covered may be formed by an apparatus having two mixture shoots and carrying out the operations of laying the metal plates on the conveyer, spreading the mixture, smoothing the mixture layer, laying wood sheets on, spreading a further mixture layer on the wood sheets, smoothing this layer and laying another metal plate on, the assemblies then being placed in the hot press. In a further modification, Fig. 6, metal plates from the stack 137 are covered with mixture from the shoot 123, smoothing of the layer being carried out by the roller 149 and cross-conveyer 155. Veneer plies or a plurality of edge-abutted strips from a stack 165 are laid with their grain longitudinally and in registry with the metal plates. Core plies (or edge-abutted strips) are coated on both sides by a conventional glue-coating machine 166 and laid on with their grain running p transversely of the line and their side edges in abutment and overlapping the face plies. Another series of face plies with their grains running longitudinally and their ends in registry with the metal plates are laid on and the core ply cut in line with a metal plate by a clipping machine 167. The severed assemblies are then carried by another conveyer 128 to the hot press and the veneer sheets consolidated simultaneously with the bonding of the mixture. In a further form (not shown) the mixture and the plywood panels are laid on a continuous metal belt which then passes through a hot press. The resins used in the mixture may be condensation type such as phenol-formaldehyde, urea and furfural or addition type polymers such as diallyl phthalate and vinyl methacrylate. Colouring pigments or fireproofing materials may be added. Where one side of the ply only is coated, the cracks and imperfections in the other provide suitable base for substances such as paint or adhesives.