Tobacco – Tobacco treatment – With fluid or fluent material
Patent
1992-06-12
1995-06-20
Bahr, Jennifer
Tobacco
Tobacco treatment
With fluid or fluent material
131290, A24B 304
Patent
active
054253845
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to improvements in rotary tobacco treatment cylinders and is particularly concerned with the geometry of internal paddles or flights in such cylinders, which are provided to optimize the treatment of tobacco in the cylinder.
In the pre-treatment of tobacco before manufacture within cigarettes, it is necessary to subject it to drying, mixing processes, or conditioning with the addition of fluid; and these are often carried out in a rotary treatment cylinder which is arranged to rotate about a generally horizontal or slightly inclined axis. Such treatment cylinders are provided with internal paddles to provide transport of the tobacco product through the cylinder. In the cases of drying and conditioning it is necessary to maintain the transport time through the cylinder; not only should the average time of the mass of tobacco be maintained but also the time for each individual particle.
Furthermore, the tumbling of tobacco within such a cylinder tends to cause degradation. This degradation is very dependent upon moisture content and increases rapidly with reduction of moisture content below normal cigarette moisture contents of some 13-14%. Thus variation in moisture content in the output from a drying cylinder can be a major contribution to tobacco degradation.
There are several factors which can affect the transport time such as paddle loading, cylinder inclination, drop height, that is to say the height within the cylinder from which the material drops from a paddle to fall back to the wall of the cylinder during the tumbling operation, and the number of drops. However a factor which has been generally overlooked is the consistency which is determined by the release point and which is particularly important in the case of drying.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an arrangement in which the release position can be precisely predetermined.
A further object of the invention is to provide a consistent rapid release of the tobacco from the paddle i.e. a sharply defined release point, instead of a slow sliding or tumbling off action.
According to the present invention there is provided a rotary tobacco treatment cylinder comprising an elongate hollow cylinder arranged to rotate about its longitudinal axis and disposed substantially horizontally or inclined by a small angle to the horizontal, a series of elongate paddles extending longitudinally within the cylinder and extending generally towards the longitudinal axis from the inside surface of the cylinder, the paddles serving to convey material to be treated from a lower position within the conveyor and around one side to an upper discharge position, the paddles having a proximal portion extending at a first angle being a right angle to the tangent at the root of the proximal portion or an angle less than a right angle at the loaded side of the paddle, and a distal portion which is inclined to the proximal portion at a second angle, which is less than the first angle, to form a tip, a major part of the tip considered longitudinally being of a length (viewed axially of the cylinder) less than half the length of the proximal portion, characterised in that the cross-sectional area of the material to be treated which is loaded onto a paddle, is less than or equal to the area enclosed by the paddle and a line from the paddle tip to the cylinder wall at the angle of repose of the material to be treated, when the paddle in question is at a predetermined release point around the cylinder.
Further according to the invention the angle of the tip of each paddle to the tangent at the root of the proximal portion is such that at a predetermined release point the tip is at the angle of sliding, the surface of the tobacco charge just contained by the tip being at the angle of repose.
Preferably the proximal portion of the paddle is radially disposed.
Another aspect of the invention is that the tip is inclined relative to the proximal portion at an angle substantially greater th
REFERENCES:
patent: 1595659 (1926-08-01), How
patent: 4592150 (1986-06-01), Schnupp
patent: 4984587 (1991-01-01), Neville
Bahr Jennifer
GBE International plc
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