Patent GB-708577-A (GB)
Title: Tobacco cleaner and classifier
Inventor: ROWELL LORNE ARCHIBALD
IPC: A24B5/10
Filed: 1952-02-29
Abstract: 708,577. Pneumatic separating. IMPERIAL TOBACCO CO. OF CANADA, Ltd. Feb. 29, 1952, No. 5412/52. Class 117 [Also in Group VI] In an apparatus for separating loose tobacco leaf from a mixture of tobacco material containing loose leaf, clean stems, and stems with portions of leaf attached, the mixture is dropped past air nozzles which project the loose leaf through inclined chambers into a collecting chamber, and an air impeller for supplying air under pressure to the nozzles has its inlet side connected through a screen to the collecting chamber and its pressure side connected to a tank supplying the air nozzles. The tobacco material is fed through a shoot 6 and drops past the lower ends of chambers 10, 12, 14 each of which is associated with a projecting baffle 27 and a pair of air nozzles 38, 31<SP>1</SP> Fig. 5, which blow across the stream of material and convey the loose tobacco through the chambers into a collecting chamber 22. The lower jet 31<SP>1</SP> of each pair of nozzles is directed against a curved portion 31 of the lower wall of each chamber to produce turbulence in the air streams adjacent the end of the chamber. The tobacco leaf carried into the chamber 22 drops on to a conveyer 24 which delivers into a shoot 33 leading to a rotatably mounted classifying screen 34 through which the fine material passes on to an inclined trough 34a, the coarser material being discharged from inside the screen on to a table 34c. The air streams entering chamber 22 flow through a rotary screen 25, the interior of which is connected through a pipe 65 to the intake of a combined fan and dust collector 62, Fig. 1, the outlet 63 of which supplies air under pressure to a tank 21 feeding the air nozzles. The fan 62 is constructed to separate dust from the air sucked thereinto, and tobacco leaf material is removed from the screen 25 by a' spring- loaded brush 79. The material passing beyond the lower end of chamber 14, which comprises clean stems and stems with some tobacco leaf attached, is intercepted by a curved plate 53 and is blown by a jet 57 up a passage 45. The longer clean stems and the stems with tobacco leaf attached are carried over into a second collecting chamber 47, whilst the short clean stems slide back down the passage 45 and drop through a shoot 55 on to a conveyer 46. The material delivered into chamber 47 drops through a hopper 48 to a hammer mill 49 which breaks up the long stems and detaches the remaining scraps of leaf from the stems, the resulting material being delivered back to the shoot 6 and passed through the machine again for separation of the leaf material from the short pieces of stem which finally drop on to the conveyer 46. The inlet 65 of the fan 62 is also connected to the interior of a rotary screen 25a in the chamber 47, so that all the air used travels in a completely closed circuit. The apparatus is completely closed by a casing, the interior of which, due to the closed circuit of the fan 62, 'may be placed under slight suction to prevent escape of dust by bleeding off from the pressure tank 21 about 10 per cent. of the output of the fan 62. Throttle valves 70, 71, 72, control the amount of air flowing to the fan 62 through the branched inlet 65. Electric lights 74 and opposed inspection windows in the side walls of the casing permit inspection of the operation of the various separating stages.