Improvements in or relating to process and apparatus for the manufacture of films and foils

摘要

In a process for the manufacture of films and foils such as are used for wrapping and packing purposes from cellulose derivatives, resins and other plastic substances with or without plastifiers wherein a solution of the plastic substance in a volatile solvent is poured on to a moving smooth support which passes through a drying chamber to evaporate the solvent, the operation of pouring the solution on to the support is separated from the slower operation of stripping the formed film or foil from the support, and the two operations are performed at independent but correlated speeds. A band 1 is unwound from a spool 2 mounted on a carriage 3 with wheels 4 and passes over guide rollers 5 to a driving roller 6 and roller 7 above which is mounted a pouring tank 8 which layers the solution of plastic substance on to the band. The band then passes in a series of vertical loops over rollers 9, 10 in a heated drying chamber 33, the upper set of rollers being provided with spring-pressed rollers 11 co-operating with the uncoated edges of the band 1. From the last roller 10 the band returns over guide rollers 12 to a take up spool 200. When a length of band 1 is nearly exhausted, the machine is thrown into low gear and the end of the band connected by clips with another length of band on a spool 2. Pipes lead from the enclosure 33 to a solvent recovery plant, which also contains a fan for blowing heated air into the lower portion of the chamber 33. In addition, air is drawn from the lower chamber of the enclosure 33 by the pipe 48 into the heater 49 and is passed from there through pipes 50 to branch pipes 51 leading into the top of the enclosure 33. The rollers 6 and 9 are driven from an electric motor 13, Fig. 2, the drive being transmitted through reduction gearing 14 to a gear box 15 and clutch 16 and thence to the distributing gears 17 which connect the shafts 18, 19, 20. The spindle of each roller 9 carries a spur wheel 22 between adjacent pairs of which are spurs 23 keyed to shafts 24 driven from the shaft 18 by a chain 26 passing over sprockets 25, 27. The shaft 19 carries a socket 28 to receive the end 29 of the spindle 30 of the spool 200. Shaft 20 drives by chain and sprocket the roller 6. To strip a finished foil, the coated band is mounted in the stripping unit, Fig. 3 on the roller 200. The foil 52 is stripped, passed over rollers 53, 54, 55, 56, to driving roller 57 and receiving roller 58 pivotally mounted on the framework 59, and counterweighted at 61. The stripped band I passes over roller 62, between rollers 63, 64 and thence over roller 65 to the spool 2 on which it is rewound, by means of the friction roller 66. The stripping unit, together if desired with other similar units is driven from an electric motor 70 through reduction gearing 91, a mainshaft 71 with bevelled gears 72, 73, clutch 74 and shaft 75, which carries two sprockets, one of which drives the sprocket 77 keyed to the shaft 78 of the roller 63. The roller 64 is driven by gearing 79 from the roller 63 and at the same speed. The other sprocket 76 drives sprockets 80, 81 by a chain 82. Sprocket 80 is keyed to the shaft of the roller 66. Sprocket 81 drives the roller 62 and a sprocket 85 which by chain and sprocket gearing drives the roller 57. Since the stripping operation is a slow one, a number of stripping units are provided for one pouring unit. In a modification, the stripping unit is arranged adjacent the pouring and drying unit, the take-up and feeding spools being fixed instead of movable, and the band is passed over guide rollers in the manner of a spiral. The band which may be of paper, canvas or celluloid, coated, e.g. with lacquer if desired may be advanced through the drying enclosure by means of endless chains, clipping the reinforced edges of the band, or carrying a plurality of rods which pick up the band in succession and carry it forward in a series of loops.