Tobacco – Tobacco treatment – Leaf stemming
Reexamination Certificate
1999-09-14
2002-11-19
Griffin, Steven P. (Department: 1731)
Tobacco
Tobacco treatment
Leaf stemming
C131S313000, C241S159000, C241S190000
Reexamination Certificate
active
06481441
ABSTRACT:
This invention relates to apparatus and a process for threshing tobacco.
In the tobacco industry, it is well-known that in order to process the tobacco into a suitable form for use in the manufacturing of products, the tobacco leaf has to have the midrib stem removed from the rest of the tobacco leaf. This separation is sometimes done by hand but is more commonly done using a threshing machine.
Threshing machines for tobacco, now in use, differ little from that described by Du Brul in U.S. Pat. No. 209,801 of Nov. 12, 1878, designed for threshing tobacco for use as cigar filler.
In the current art, the most common leaf threshing process consists of:
1. Feeding the tobacco leaves into the top of a threshing mill. The leaves are broken up by the action of a rotating element, with radially protruding teeth, until they are small enough to pass through a fixed screen at the bottom of the mill.
2. The threshed leaf is then classified using an air flow in a vertical tower. The lighter, stem free, material rises with the air flow and is removed from the threshing process. The heavier, stem containing, material drops, under the influence of gravity, down the tower, through the air.
3. This heavy, stem containing material is passed to a second threshing mill, and the process is repeated.
The overall threshing process usually has between 4 and 6 stages of threshing and classifying before all the lamina is removed from the midrib stem.
The most common form of-threshing mill for tobacco is described by Allen in U.S. Pat. No. 2,760,492 and Bonner et al in U.S. Pat. No. 3,141,485.
U.S. Pat. No. 2,962,029 (McCashen) describes a tobacco threshing machine having a single rotating threshing element mounted inside a rotating drum.
Various documents describe machines which include two or more rotating threshing elements inside a single machine with various claims for improvements over existing single rotor threshers. Bonner et al in U.S. Pat. Nos. 3,126,014 and 3,696,817 describe a thresher containing two or more rotating elements in a cascade, set in conventional fixed baskets. Smith in U.S. Pat. No. 3,706,314 describes a machine with two rotating elements with radial teeth meshing with rotating elements consisting of discs. None of these three machines is in common use.
Wochnowski in GB 1,077,410 and Johansson et al in U.S. Pat. No. 3,229,698 describe threshers containing two or more mills with fixed baskets contained within an air separation tower. In the first of these, the threshers are conventional in form. In the second, the thresher axis is mounted vertically rather than horizontally. Machines of the second form are commercially used but they seem generally to be less efficient than the conventional type and are used primarily where floor space is at a premium.
Phillips in GB 301,239 describes a machine for stripping tobacco leaves in which the lamina is separated from the stem by passing the leaves between pairs of counter-rotating brushes and rollers which rotate at different speeds. The leaves are subjected to tensile forces which separate the-lamina from the stem.
Dahistrom et al in U.S. Pat. No. 2,150,493 and U.S. Pat. No. 2,152,791 teach a device for disintegrating tobacco leaves which includes a pair of counter-rotating rollers for feeding tobacco leaves to a rotating cylinder having a series of projecting teeth. However, all of the separation of the lamina from the stem occurs away from the rollers at the point where the teeth on the cylinder pass through a series of intermeshing discs.
U.S. Pat. No. 2,789,564 (Hunter) and U.S. Pat. No. 4,805,643 (Tetaka) describe apparatus in which tobacco is delivered to a relatively large toothed rotor via an opening located. above the rotor. Hunter employs further smaller toothed rotors which intermesh with the large rotor to thresh the tobacco leaves.
EP-A-0135048 relates to a system for use with a tobacco threshing machine to control lamina size.
In the food and farming industries, threshing is traditionally used to obtain the seeds or fruits of the crop free from the bulk of the plant material. This is normally done as a part of the harvesting.
Threshers used for legume crops use an axial flow threshing system as described by Looker et al in GB 1,396,931 and 1,396,932. Here the crop mass is transferred into a large rotary drum constructed from mesh panels. Inside the drum are a number of beater elements.
According to Looker et al, these work by designing the crop mass flow path such that several impacts occur. These impacts are sufficient to break open the legume pod and free the seeds contained inside.
The present invention relates to apparatus and a process for threshing tobacco which has significant advantages over the known techniques.
Accordingly, the present invention provides apparatus for threshing tobacco comprising rotatable stripping means and a feeder comprising a pair of co-operating counter-rotatable elements for delivering tobacco leaves to the stripping means, the feeder and the stripping means being arranged such that, in use, the tobacco leaves experience shearing forces as they pass from between the counter-rotating elements to the rotating stripping means which forces at least partially strip the lamina from the stem.
The stripping means preferably comprises radially extending arms. The arms may be in the form of continuous plates or spaced teeth (which can be straight, bent or curved) and may include parts which are capable of cutting the tobacco leaves or are capable of puncturing the leaf and tearing through the leaf.
The elements also preferably comprise radially extending arms which also may be in the form of straight, curved or bent continuous plates or spaced teeth, optionally including parts which are capable of cutting the tobacco leaves. Alternatively, the feeder elements may comprise a pair of rollers or may consist of a flexible membrane wrapped around a framework which allows variable quantities of leaf to be fed.
The arms may be flexible, inflexible or a mixture of fixed and flexible components.
The rotating elements and the stripping means can take the same form and may be the same shape and size, differing only in their function which is dictated by their position in the apparatus.
The stripping means and the feeder are arranged at a relatively close distance from each other in order to subject the tobacco to the shearing forces which at least partially strip the lamina from the stem. Preferably, the distance between the outermost parts of the two elements in the feeder is less than 150 mm and the distance between the outermost parts of each of these elements and the outermost parts of the stripping means is less than 100 mm. The shearing forces are experienced by the tobacco leaves as they are directed from the feeder to the rotating stripping means. The tobacco leaves are preferably delivered to the rotating stripping means substantially along a radius of the axis of rotation of the stripping means. The lamina is stripped from the stem in the region where the leaves pass from being moved under the influence of the feeder to being moved by the stripping means and, as the skilled person will appreciate, the exact position of this region will vary depending upon the particular configuration of the apparatus and the rate of rotation of its various rotating components. The shearing force can be considered, at least in certain circumstances, as arising from the action of the stripping means on one part of the leaf while the feeder is holding another part of the leaf.
Preferably, where the arms of the stripping means and those of the elements consist of spaced teeth, the teeth are intermeshed. With such an arrangement, the stripping of the lamina from the stem is effected, to some extent, by the interaction of the stripping means and the feeder. When the teeth are intermeshed, the distance between the teeth as they pass each other is typically less than 100 mm.
The apparatus preferably comprises a rotatable drum in which the stripping means and the feeder are arranged. The drum may be generally cylindrical and
Griffin Steven P.
Imperial Tobacco Limited
Larson & Taylor PLC
Walls Dionne A.
LandOfFree
Apparatus and process for threshing tobacco does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and process for threshing tobacco, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and process for threshing tobacco will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2952496