Classifying – separating – and assorting solids – Plural – diverse separating operations – Gaseous suspension and stratifying
Patent
1991-02-27
1992-09-22
Huppert, Michael S.
Classifying, separating, and assorting solids
Plural, diverse separating operations
Gaseous suspension and stratifying
209466, 209467, 209486, 209493, 209494, 209506, B07B 900
Patent
active
051489210
DESCRIPTION:
BRIEF SUMMARY
The invention relates to apparatus for the pneumatic separation of particulate material particularly by not solely for the separation of objectionable material such as stem from cut lamina or cut rolled stem tobacco (CRS).
In the tobacco industry such products are unthreshed tobacco, threshed tobacco, cut dried stem, cut dried lamina, cut tobacco generally in the primary process, in the feed systems to cigarette makers and within the makers.
It is well known in the tobacco industry to use a vertical upward flow of air to separate tobacco particles of differing terminal velocity, into two fractions. The particles with terminal velocity below that of the air (lights) being carried upward by the air stream and those with terminal velocity above that of the air (heavies) falling downwardly against the air stream, the particle fraction being adjusted by the air velocity.
The unseparated particles are normally thrown horizontally into the air stream by a winnower. The light particles carried upwardly are removed from the air by a tangential separator (e.g. cyclone) or screen separator and the heavy particles are dropped out through a chute, preferably with an air lock.
Typically the screen separator contains a screen through which air but not desired product can pass and also an airlock in the form of a paddle wheel assembly. The tangential separator also has an airlock of paddle type. In either arrangement the rotation of the paddle wheel limits air interchange and allows the product to be discharged.
Product size degradation can be caused by impaction against the screen, material sliding across the screen, by abrasion and chopping within the paddle wheel. Degradation can also occur by impaction and abrasion in the conveying tube.
The heavy particles may instead fall on to a horizontal gauze screen in the air stream which is vibrated in the manner of a jigging conveyor to convey the particles out of the air stream. The vibrating screen can also be used to feed the unseparated particles into the air stream.
To provide an accurate classification it is clearly important to have an air flow of uniform velocity. In one form of the equipment this is achieved by adjustable air guides below the gauze screen. In another the gauze screen is replaced by a perforated diffusion plate with fine holes.
The plate has a low percentage free area of typically 2.5% and builds up enough pressure on its under side to diffuse the air uniformly.
Tobacco leaf comprises thin lamina and a relatively thick mid-rib (known as stem) and veins which are structural and vascular. These are separated during manufacture by a threshing process into mid-rib and lamina with veins and then processed separately including cutting or shredding.
The cutting of mid-rib or stem produces some stick-like pieces or slivers, which when made into cigarettes can penetrate the paper tube. These can be effectively separated by the known methods described above, usually following drying, where the separating air also cools the tobacco.
The cutting of the lamina also produces some slivers partly from the 1 or 2% of stem which has not been separated from lamina, but also from the veins and tip of the mid-rib which are not separated by threshing.
The cigarette making maching is fitted with a winnower to remove these slivers but is only 75% successful. It is desirable to remove these slivers before they reach the making machine.
In some parts of the world the leaf is hand cut by the farmer before it reaches the cigarette manufacturer. The cut is at right angles to the stem, so the strands of cut lamina include a cross section of the stem known as a `birds eye`. This is broken away from the cut lamina by the carding drums in the cigarette maker to produce an undesirable drop out from the cigarette.
It is possible to break the birds eyes from the cut lamina before the cigarette maker by the use of prior carding drums. It then becomes necessary to remove the birds eyes from the cut lamina before they reach the making machine.
A disadvantage of the pneumatic method of sepa
REFERENCES:
patent: 1315880 (1919-09-01), Sutton et al.
patent: 2006119 (1935-06-01), Steinmetzer
patent: 2028904 (1936-01-01), Haworth
patent: 2803346 (1957-08-01), Weston et al.
patent: 4294693 (1981-10-01), Brennan
patent: 4913804 (1990-04-01), Muller
patent: 5087351 (1992-02-01), Valentine, Sr.
GBE International plc
Huppert Michael S.
Kaufman Joseph A.
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