Patent GB-324694-A (GB)
Title: Improvements in and relating to the production of films
IPC: B29C48/08
Filed: 1928-10-22
Abstract: 324,694. Pease, W. H. Oct. 22, 1928. Apparatus for making films or very thin sheets by evaporation of the solvent from suitable solutions comprises an endless band preferably of metal, passing through one or more heated and heat-insulated casings and around a pair of drums one of which is adapted to be cooled, whilst both rotate at a common peripheral speed on horizontal axes at least one of the drums being driven by toothed or worm wheel gearing. A hopper and spreading device deposit a layer of solution on the band as it passes over the cooled drum. Means are provided for heating the band near this point, and the casing is provided with inlet and outlet for a current of heated air. The dried film or sheet is stripped from the band. In the event of abnormal temperature effect, the machine may be stopped by thermally operated electrical relays. Two or more spreading devices may be arranged to deposit the respective layers such as a dope and substratum material on the travelling band in sequence so as to form a composite sheet, and additional cooling devices for the band may be placed near the non-cooled roller which roller may be carried in adjustable bearings for tensioning the band. As heat-insulating material there may be used a composite covering consisting of a metallic exterior, a plywood layer, a layer of cork fragments and a layer of asbestos sheet. A duplex machine is illustrated in the drawings. A pair of drums 4, 5 are driven by an electric motor 6 through reduction gearing incorporating clutches 7, 8 and control shafts 9, 10. The peripheries of the drums 4, 5 are cooled by brine introduced by the pipes 11, 12 and removed by pipes 13, 14. Non-cooled drums 15, 16 are arranged in bearings at the opposite end of the machine. These bearings as shown are adjustable for the purpose of tensioning endless metallic bands 20, 21 which pass round the drums 4 and 15, and 5 and 16 respectively. The bands 20, 21 are enclosed by heat insulated casings 22, 23 which extend between the frames 2, 3 from end to end of the machine. Heated air enters at 37 and leaves the casing 22 by the exit 31 the size of which is controlled by a slide valve operated by a handle 32. A solution hopper 25 is arranged so that its delivery orifice 26 is close to the band where the latter is in contact with the cooled roller 4. The width of the orifice 26 is adjusted by turning the knob 29 on the screw 27 which acts on the lever 28 of the flap 38. The hopper 25 is provided with a jacket 30 into which through pipe 39 passes fluid, the temperature of which is thermostatically controlled. Behind the cooled drums 4 and 5, stripping rollers 33 take up the dried film or sheet which then passes over guide rolls 34 to removable driven stock rolls 35. Steam or other pipes are arranged at 36, Fig. 1, beneath the band after it leaves the cooling drums 4 and 5. The Provisional Specification describes a machine in which the spreading device is placed near the non-cooled drum. Specifications 16306/00, [Class 121, Starch &c.], 4601/13; and 177,262, [Class 70, Indiarubber &c.], are referred to.