Patent GB-727903-A (GB)
Title: Tobacco sheet material, method of and apparatus for making the same
IPC: A24B15/12
Filed: 1952-04-02
Abstract: 727,903. Tobacco substitutes; treating tobacco. AMERICAN MACHINE & FOUNDRY CO. April 2, 1952 [April 10, 1951], No. 8371/52. Class 130. Sheets or filaments for use in place of natural tobacco in cigars, cigarettes etc. are formed by depositing in successive layers, on a filmforming surface, tobacco particles, a filmforming material and further tobacco particles. Suitable film-forming materials are watersoluble salts of specified water-insoluble cellulose derivatives, or aqueous dispersions of these derivatives, prepared as described in Specification 698,948, [Group IV (a)], with added glyoxal and/or glycerine if desired. An endless metal conveyer belt 12 is uniformly sprayed with a wetting solution 15, comprising water with, if desired, small quantities of detergent and/or film-forming material, and supplied from a mixer 10 through a metering pump or valvecontrolled flowmeter 13 to a compressed-air sprayer 20 which may have multiple stationary heads or a single head reciprocable on a crossthreaded drive shaft 24. Excess spray may be caught in a hood' connected to an air/droplet separator. Tobacco particles screw-fed from a hopper 48 having an electric vibrator 46 are forced by air from a blower 41 through a tube 40 to be uniformly deposited in a relatively thick layer on the wetted belt 12 through a nozzle 38 which may extend across the belt, be one of a plurality of nozzles or be reciprocable on a cross-threaded drive-shaft 53. Film-forming material 51 is forced by a metering pump, such as that described in U.S.A. Specification 1,848,024, through a pipe 64 to a compressedair sprayer 70 reciprocable on a cross-threaded shaft 69 to deposit a thin layer of material over the tobacco on the belt 12. A hood may be provided to recover excess spray. Further tobacco particles, gravity-fed into the inlet of an air blower 88 from a hopper 82 vibrated by a motor 84, are forced together with the blown air through a nozzle 74 and deposited in a relatively thick layer on the film-forming material to produce the final coated web W. The nozzle 74 is reciprocable by a cross-threaded drive shaft 77. The belt 12 then passes blades (not shown) of rubber, thin steel or other flexible material bearing on its upper surface at either side and which scrape off and remove the web edges to bring the web to a desired width determined by the adjustable setting of the blades laterally of the belt. The web W is then dried by passing through a heater 90 which may be divided into zones, as I, II, III, having appropriate individual conditions of temperature, air velocity and humidity, and also, if desired, individual temperature and/or air velocity control on either side of the belt, such that belt expansion is completed before web solidification occurs, and web cracking is minimized. The zones I, II, III, may be controlled by thermally actuated valves 91 each responsive to the exhaust air temperature of the respective zone and, in the case of a gas fired dryer, controlling the quantity of gas burnt therein. Alternative or additional belt expansion prior to web solidification may be effected by a heater 110. On leaving the heater 90 the web W passes beneath a brush 122 rapidly rotated to remove loose tobacco which is collected by one suction hood 126 of a dustair separator (not shown), such as a bag filter or a cyclone, which also receives from suction hoods 45, 76 excess tobacco from the nozzles 38, 74 and delivers separated tobacco to the hopper 48. After brushing, the web W may be moistened and/or dyed by spray sets 142, 144 supplied by gravity or pump from water and dye reservoirs 163, 165 through metering devices 166, 167 and a mixing and atomizing valve 160 supplied with compressed air through a conduit 168. The web W is then stripped from the belt 12 by a scraper 180 and passes over a nozzle 188 which, to dye the undersurface of the web, may optionally be reciprocated from a cross-threaded shaft 186 whilst being supplied, by the opening of a control valve (not shown), with dye, as from the reservoir 163 through a metering device, and with compressed air from a conduit 191. The devices 188 and 142, 144 may both be hooded for excess dye spray recovery. Additionally or alternatively to being dyed, the web undersurface may be moistened. After passing on a canvas or like belt 192 through a dryer 202 which determines its final moisture content, the web W is cleaned of any remaining loose tobacco by rotary brushes 210, 220 provided with further suction hoods 212, 224 of the dust-air separator previously mentioned, and may then be rolled into reels but, as shown, is cut longitudinally into strips by a number, e.g. five, of equally spaced rotary knives 230 co-acting with grooves in a rotary metal roller 238, successive lengths being then cut from the strips by coaction of a rotary knife 242 and a rotary ledger blade 252 and falling between a plate 264 and a suction hood 262 of the dust-air separator which removes loose tobacco caused by cutting. Between the scraper 180 and the nozzle 188, the web may pass through a dyer and be brushed on its undersurface to ensure even dyeing thereof. In a modification, the initial layer of tobacco. deposited is dried before application of the film-forming material. A longer belt 12 may be used and the initial tobacco deposition, and, if desired, also the application of wetting solution, made on the upper run of the belt. Specification 727,886 also is referred to.