GB981897A - Improvements relating to the manufacture of plywood - Google Patents

Abstract

981,897. Plywood. FACTORIES DIRECTION Ltd. Jan. 20, 1964 [Oct. 19, 1962], No. 39583/62. Heading B5L. A method of continuously manufacturing a sheet of plywood of indefinite length from two or more webs of wood veneer comprises forming each web by successively securing together strips of wood veneer in side-by-side abutting relationship to one end of each web, and bringing and adhesively securing together the webs thus formed to form a stack, the arrangement of the strips and webs being such that the grain of the wood runs lengthwise of the strips, each strip extends from one edge to the other of the web of which it is a component, the strips in any one web are mutually parallel and are inclined to the longitudinal axis of the web, and at least one pair of adjacent webs have the strips of one web of the pair inclined to one side of the longitudinal axis of the sheet and the strips of the other web of the pair inclined on the other side of the axis. As shown in Fig. 1, the sheet comprises three webs 10, 11, 12 with the strips of the webs inclined at 45 degrees to the longitudinal axis 13 of the sheet so that the strips of one web are at 90 degrees to that of an adjacent web. In an embodiment having four webs, the strips of the outer webs run in the same direction and those of the intermediate webs in the opposite direction. The strips may be of the same or differing widths. The strips are cut from a dried sheet of veneer by passing the sheet between a pair of rollers one of which has a plurality of radial blades. The strips are then assembled into a web by passing through apparatus having three or more adjacent drums 16, 17, 18, Fig. 3, the gaps between the drums being slightly greater than the thickness of the strips. The strips are held on the drums by suction means 21 and passed from one drum to the next by transfer means 22. The strips are placed on the first drum at an angle of 45 degrees and pass to succeeding drums which rotate slower than the preceding drum so that the strips leave the drum in tight abutting relationship to form a web. The strips are secured together to facilitate handling of the web by threads of cotton coated with quick-setting cement, by stitching or by adhesive-coated paper. The webs 24, 25, 26, Fig. 5, forming the sheet of plywood are fed from the final drums 27 of the apparatus for forming the webs to rollers 29 which turn the webs through 90 degrees for assembling in a stack 31, adhesive being supplied to the webs from rollers 30 before the stack passes between a pair of nipping rollers 32 or a preliminary unheated press, a heated press 33 and a pair of rollers 34, the preliminary press and heated press being arranged to open and close alternately. In other embodiments, the heated press is arranged to move with the web or is replaced by heated rollers. After the webs are secured together, the edges of the assembled sheet are trimmed and the surface of the sheet may be sanded.