Patent GB-558491-A (GB)
Title: Improved method of and mechanism for effecting correction for undesired variation in the tobacco content or the density of a travelling stream of tobacco, particularly in cigarette manufacture
IPC: A24C5/34
Filed: 1942-04-01
Abstract: 558,491. Automatic control systems. AMERICAN MACHINE & FOUNDRY CO. April 1, 1942, No. 4359. Convention date, April 2, 1941. [Class 38 (iv)] [Also in Groups XXXVI, VI, XXXVII and XL] In an arrangement for effecting correction of undesired variation in the tobacco content or density of a travelling stream of tobacco, particularly a cigarette rod in the manufacture of cigarettes, the moisture content, which is normally uniform for a given mass of tobacco, is utilized as an index of the tobacco content or density at any part of the rod or stream, for varying the electrostatic capacity of a capacitative coupling from a predetermined standard content or density and causing a current or change of current for ejecting faulty cigarettes or for changing the rate of tobacco-feed to the stream of rod to restore normal condition. The feed F, Fig. 1, feeds tobacco on to a moving paper strip which is formed at U into a rod R which is cut at K into individual cigarettes L which are pushed through a guide 46 and fall on to a belt 47, Fig. 2, or, if faulty, are deflected into shoot 82 by an ejector 15. The rod R, prior to cutting, passes through a detector box D containing a pair of condenser plates 201, Fig. 6, for detecting over-filling or under-filling by changes from the normal moisturecontent of the rod R. The feed - mechanism drives through shaft 25 and gearing 35, 36 a timing disc 38 carrying a number of spring-plungers 40 which are urged rearwards but held by levers 44. When the detector D detects a faulty piece of rod, electromagnet 225 is energized and attracts armature 50 which breaks the energizing circuit at contacts 226 but is held in attracted position by a spring latch 54. At the same time a part 58 of armature 50 obstructs the next lever 44 and the associated plunger 40 is released, thus deflecting 54 and allowing return of armature 50 in readiness for a further actuation. Meanwhile the released plunger is rotated to engage and lift a lever 64 which releases a crank lever 70, 71 which falls and by means of rod 79, allows the continuously-driven ejector 15 to rotate about pivot 18 into operation position and eject the faulty cigarette, whereupon the continuously-driven cam 75 restores the mechanism to original position leaving 70 relatched by lever 64. A ramp 85 then causes return of the displaced plunger 40. The plates 201, Fig. 6, are connected, together with a variable and standard condenser 202, between a tuned coil 212 and respective opposite ends of the centretapped anode coil 206 of an oscillator valve 207 generating, say, 500,000 cycle oscillations, whereby normally equal and opposite currents are produced at the ends of coil 206 and no voltage is impressed on coil 212. In the event of a change of capacity in 201, the resulting voltage across 212 is amplified at 213 and fed through highfrequency transformer 215 to an electron-ray indicator tube 216 and gas-filled output tube 217, the plate circuit of which includes the electromagnet 225, together with contact 226. In setting up the device, the circuits are turned to the required frequency ,and condenser 202 is adjusted for zero output of 213, as measured by 216, with a standard cigarette between plates 201. The amount of permissible variation is adjustable up or down by varying the amplification of 213 by means of rheostat 230 and the bias on the grid of 217. By suitably controlling the detector D and locating it in relation to knife K, the ejector may be adapted to eject only cigarettes having faulty ends, a switch being arranged for this purpose in the anode circuit of valve 217 so as to cut out the detector except at the severing points on the rod, Fig. 9 (not shown). Instead of, or in addition to, detector D, there may be a detector Z, Fig. 1, comprising somewhat elongated condenser plates 301, Fig. 7, for maintaining an average density of tobacco by accelerating or retarding the feed mechanism F. This system is the same as Fig. 6 up to the h.f. transformer 336, the two-part secondary of which is connected, for separate rectification of the h.f. voltages, to a double-diode 337, the rectified voltages from which are impressed on the grids of output valves 317, 317a adjustably biased by series-connected potentiometers 341, 341a. The plates are connected to electromagnets 325, 325a operating on a balanced armature 344 to control a reversible motor 352 which in turn controls variable-speed transmission mechanism 356 of the belt and adjustable pulley type between motor 357 and the chain 358 driving the feed F. In setting up this system, condenser 302 is adjusted for zero output of 313 with the detector unoccupied, and after a standard cigarette has been inserted and rheostat 330 set for maximum amplification, potentiometers 341, 341a are set below the trip points of 317, 317a. When one of the latter is tripped, depending on the sense of the variation, the feed is adjusted to restore the desired average. A cam 343 driven by the mechanism cuts off the valve 317 of 317a after a time sufficient for the correction to be detected at 301 and if the correction is insufficient a further correction can be made. In Fig. 8, tobacco passes from FE between inclined driving bands 403, 404 on to a cigarette paper strip F propelled by tape 401, and is carried into a channel formed between the tape 401 and top belt 402, both driven from the main drive. Belts 403, 404 are driven separately by means of a chain 407 and the variable speed mechanism of Fig. 7 and at a greater speed than 401, 402 so as to build up in the channel a stream CO of greater volume and density which is subsequently formed into a cigarette rod. The detector plates 400 are designed to maintain a column of uniform length in the channel and operate to regulate the feed if this length is departed from, the point of building-up of the column being preferably within the length of the detector. Alternatively, the tobacco may be normally overfed, and the feed reduced when the column builds up rearwardly of a given point, and there may be added a further detector for controlling the density in the manner of Fig. 7. In a modification of Fig. 6 adapted to detect short defects such as holes or hard spots, and not changes of density or moisture content or change in quality which affect all parts of the rod equally, two pairs of condenser plates are employed, spaced apart from one another and one pair being preferably longer than the other and serving as a standard. The tap on oscillator coil 206 then divides the coil inversely as the capacities, which are connected to respective opposite ends of that coil, Fig. 10 (not shown).