Patent GB-396723-A (GB)
Title: Improvements in the manufacture of artificial films or foils and apparatus therefor
IPC: B29C41/24
Filed: 1932-01-30
Abstract: <PICT:0396723/IV/1> <PICT:0396723/IV/2> <PICT:0396723/IV/3> <PICT:0396723/IV/4> Apparatus for the production of films and foils by wet or dry methods comprises an endless flexible band of stainless steel or cold-worked nickel.  Bands made of these metals are tough and corrosion-resistant, of high elasticity to withstand repeated flexing, and capable of receiving a high polish.  They may be employed in the production of foils or films of cellulose acetate or nitrate or other cellulose ester or ether, or of regenerated cellulose such as that obtained from viscose.  Any joint in the band is subjected to cold-rolling or other treatment in order that it may have substantially the same properties as the rest of the band.  In the production of an endless nickel band, the metal strip is annealed and the ends after cleaning are hammer-welded in a reducing atmosphere at a relatively low temperature such as 200 DEG  C. below the melting point.  The welded band is subjected to cold-rolling which brings it to the desired thickness, imparts a high degree of elasticity, hardens and toughens it, and makes the metal at the joint substantially identical in structure to that of the rest of the band. The band may then be subjected to a slight stretching by placing it over a pair of drums which can be forced apart during rotation.  As shown in Fig. 1, cellulose acetate solution is supplied by a pump 10 from a container 11 to a hopper 9 from which it is deposited upon an endless band 5 of stainless steel or cold-worked nickel.  The band is enclosed in a casing 8 provided with heating devices 13, air inlet 17, and vapour outlets 15, 18.  The atmosphere within the casing may be saturated with solvent vapour.  The foil is stripped from the band by a roller 46 and wound on a spool 47 driven by friction-wheels 48, 49 which tend to over-drive the spool.  When spool 47 is full, a second spool 50 on the arm 51 is swung into position.  The arm 51 is pivoted in a swinging frame 52.  For tensioning the band, the drum 7 is mounted in sliding bearing-blocks 19 which are connected to long screwed rods 20.  As shown in Figs. 2 and 3, nuts 21 are screwed on the rods 20 and a slidably keyed hand-wheel 22 enables coarse adjustment of each bearing block with respect to the other, or, by means of bevel gears 23, 24, and the cross-shaft 25, both of the bearing-blocks may be given a coarse adjustment by operation of either hand-wheel 22.  For independent adjustment, one of the gears 24 is disengaged from its bevel 23.  For fine adjustment, a hand-wheel 38 is operated.  This wheel is fixed to a housing 37 with internal teeth 39 which may be caused to mesh with either or both of the toothed wheels 35, 36 according to whether independent or simultaneous adjustment is desired.  The wheels 35, 36 are keyed to a shaft 33 and a sleeve 34 respectively.  Worms 31, 32 keyed to sleeve 34 and shaft 33 mesh with wheels 26.  The wheels 26 are freely mounted on the nuts 21 but normally clutched to the hand-wheels 22 by means of springs 29.  A latch 30 enables each wormwheel 26 to be disengaged from the corresponding hand-wheel 22 when it is desired to make coarse adjustments.  In the construction shown in Fig. 4, coarse adjustment of the blocks 19 is effected by independent operation of hand-wheels 22.  The adjusting gear is carried by a frame 42 slidably mounted on rods 43 connected to the frame of an air cylinder 44.  The frame 42 is connected to a ram 45 working in the air cylinder.  Fine adjustment is effected by the hand-wheel 38. During operation of the machine, the band 5 is maintained tensioned by means of the cylinder 44.  Specification 387,464, [Group XVI], is referred to.  The Provisional Specifications describe also the employment of a weighted pulley resting on the upper side of the lower run of the band in order to maintain it under tension.  There is also described the employment of a resilient depositing roller for transferring film-forming solution to the band, and also coating or the band with waxes as a further protection against corrosive influences. Specification 396,398 also is referred to.