GB368886A - Improvements in and relating to film-casting machines - Google Patents

Abstract

Uniform films are obtained by depositing and spreading solution from a hopper on to a rotating drum, the surface of which has been made truly cylindrical under working conditions as regards temperature, evaporating the solvent and removing the film. As shown in the drawings, a drum 4 is constructed from two spoke portions 14 mounted on a shaft 72 and a hollow rim portion 15 divided into compartments by cross ribs 5. Heating or cooling fluid enters from the pipe 8 through the trunnion of the drum and along the hollow spokes 14 to the hollow rim portion 15. Baffles 20 cause the fluid to pass backwards and forwards through the passages of the hollow rim and finally down spokes 14 on the other side of the drum and through the trunnion to an outlet pipe. The outer periphery of the drum is made truly cylindrical by grinding under working conditions as regards temperature. The drum is driven <PICT:0368886/IV/1> <PICT:0368886/IV/2> <PICT:0368886/IV/3> through a friction clutch and gearing by a motor which also drives the receiving spool 32. The drum is enclosed in a lagged casing 33 provided with an inlet 34 for conditioned air and an outlet 35 for vapour. The casing is provided with windows and doors for inspection and access to the film material. The dried film is stripped from the casting surface by a rubber roller 46 which guides the film to a roller 47 adjustably mounted in a frame 48. The film passes over metal rollers 51 .. 54 mounted in adjustable bearings carried by a pair of rods 49 pivoted on the frame 48 whereby static electricity accumulated on the film is conducted away to the casing. The weight of the rods and rollers is relieved by a roller 55 on a pivoted and counterweighted member 56. The film passes through a slot 43 in a curved sheet 44 constrained by the film to move in an arcuate path so that the casing 33 is closed at all times despite the variation in the size of the collecting roller 32 and thickness of the roll of wound film. Cooling pipes may be disposed near the outlet for the film in order to minimize loss of solvent vapour. The solution hopper 9 is supported by brackets and micrometer screws on a member 10 which is pivoted at 11 and supported at the other end by dependent lugs carrying rollers 13 which engage with the ends of the cylindrical surface of the drum. The front side 61 of the hopper may be moved about a pivot by means of a nut 62 on the screw 63, so as to regulate the width of the extrusion orifice. In the continuous production of a cellulose acetate film, the surface of the drum may first be coated with a layer of gelatine.