GB565370A - Improvements in or relating to the production of corrugated thermoplastic sheet material - Google Patents

Abstract

565,370. Corrugating thermoplastic sheet material. WATSON, F. (Munters' Industri Aktiebolag.). Dec. 9, 1942, No. 17513. [Class 87 (ii)] The hot sheet is passed between rollers having intermeshing teeth, and is then transferred to a supporting surface, such as a roller, having a contour similar to that of the sheet, and retained on the surface until it has cooled and hardened. The sheet may be heated prior to or during (or prior to and during) its passage between the rollers. Fig. 1 shows an arrangement in which transparent sheet material, such as acetyl cellulose 26 is led between steamheated corrugating rollers 28, 29, and then on to a cold roller 30. The sheet 26 may be pre-heated, prior to its passage between the rollers 28, 29, by means of hot air or pre-heating rollers, and may be heatinsulated, as at 50. Two plane sheets 34, 40 of acetyl cellulose are stuck to the corrugated sheet, which for this purpose is moistened with solvent or adhesive at 32, and the compound sheet is pressed between belts 42, 43, where it is dried with air which may be heated. A pump 47 sucks out. solvent, which is absorbed by silica gel. At the moment of joining, the two sheets 26, 24 should be at the same temperature (to prevent crinkling) ; using this precaution, sheets having different coefficients of thermal expansion may be united. To allow expansion of the sheets, the teeth of the rollers 28, 29, 30 may intermesh with some play. One plane sheet only may be applied to the corrugated sheet, or more than three may be united, alternate sheets being corrugated. Fig. 2 shows a modification in which three rollers 126, 111, 131 having radial bores 125 rotate about hollow heated shafts 127, 114 and a water-cooled shaft 132. The shafts are cut away to form recesses 130, 115, 118, 133 and 137. The recesses 130, 118 and 137 communicate with the atmosphere or with compressed air, and the recesses 115 and 133 with vacuum. As the sheet 143 passes through the rollers it is blown off roller 126 by air from recess 130, sucked on to roller 111 by vacuum from recess 115, blown off by air from recess 118, sucked on to roller 131 by vacuum from recess 133 and blown off by air from recess 137. Compressed air may be introduced also to the space between a screen 145 and the rollers 111, 131. The bases of the inter-tooth spaces may have axial grooves communicating through the bores 125 with the suction &c. recesses. Instead of rollers, toothed endless belts may be used.