Patent Description:
Methods for processing tobacco leaves are known, and in particular methods which provide for treating the tobacco leaves in order to separate their most valuable parts (lamina) from the least valuable parts (rib).

Generally the tobacco leaves that are detached from the plants have dimensions between <NUM> and <NUM> and are collected in bunches or "mannocchi", which have a weight of about <NUM> and are made up of <NUM>-<NUM> leaves held together by one of these wrapped around the others. The mannocchi are then collected together in groups of <NUM>-<NUM> to form the so-called "ballotti", which are then introduced into jute bags or cardboard boxes to be sent for subsequent processing, of which the one of interest here is the separation of the lamina from the rib.

Various separation techniques are known and one of these provides that the bales are treated in a pre-sorting line, in which they are placed on supply benches, where there are operators who take care of picking up the single mannocchi of each baling and arrange them on a conveyor belt, so that the tips of the leaves are oriented towards the longitudinal axis of the belt, in order to be then cut and separated by means of a pair of rotating knives placed at the downstream end of this feeding belt. The purpose of this preliminary separation of the tips from the remaining part of the leaves is to preliminarily remove the parts of the leaf without the rib, which constitute <NUM>-<NUM>% of the leaf itself and do not require to be subjected to an unnecessary treatment of separation of the lamina from the rib, which is required instead by the remaining part of the leaf.

Again this known method of treating tobacco leaves provides that the leaves thus deprived of the tip and any ties are subjected to a first vacuum conditioning cycle for about <NUM> minutes in a vacuum chamber, in which two or more cycles of vacuum with steam injection at each cycle, in order to increase the percentage of humidity from <NUM>-<NUM>% to about <NUM>-<NUM>% and thus make the product much more flexible and therefore less fragile and more resistant in the following phases of manipulation and mechanical processing. <NUM> These injections also have the function of carrying out a partial sterilization of the tobacco leaves.

It is then envisaged that the conditioned product is placed on sorting belts, where other operators eliminate the leaves that do not comply with the required standards, before conveying the remaining leaves to mixing silos, where provided, or to a second conditioning cycle similar to the previous one.

The leaves that come out of the second conditioning cycle are then transferred to a threshing line to undergo a series of beating cycles, each of which involves "beating" the leaves with a sort of "knives", so as to cause the detachment of parts of the lamina of the leaf from the rib. Moreover, since it is unthinkable that this occurs in a single treatment phase, it is generally envisaged that the beating line includes several beating stages, generally from three to five, each alternating with classification stages in classification chambers: at each beating stage knives which act on the leaves are arranged closer and closer to each other and, after beating, drop the pieces obtained on an underlying perforated grid with holes of different design according to the beating stage. The product that comes out of each stage is transferred to a classification chamber, where a blow of air introduced from the bottom upwards separates the lighter pieces of lamina from the heavier rib pieces and sends the first to a collection line for transfer to a packing station for subsequent uses; the heavier pieces of rib, to which pieces of lamina are still attached, are transferred to the next beating stage for further separation of other lamina, and so on until all the lamina is removed from the rib, which represents generally a percentage of about <NUM>% of the whole leaf and is sent to a rib packing station.

The efficiency of a traditional beating line is evaluated based on the percentage of lamina extracted from each classification chamber.

As an example, and with reference to international parameters (see CORESTA) in a beating line with five stages, and considering an average percentage of leaf limb or lamina equal to <NUM>% and rib equal to <NUM>%, one can think to extract <NUM>% in the first beating stage, <NUM>% in the second stage, <NUM>% in the third stage, <NUM>% in the fourth stage and <NUM>% in the fifth stage, for a total of <NUM>%.

From this brief exposition of the state of the art it is possible to understand the limits and drawbacks that it entails.

A first drawback consists in the large number of operators that a tobacco leaf treatment line of the type just described requires.

In particular, these operators are located in the pre-sorting line, in which the mannocchi or single tobacco leaves are placed, and in the sorting line, from which the leaves that do not conform to the required standards are removed.

Taking into account that an operator is generally able to feed <NUM>-<NUM> / h of product and that a treatment plant is able to process <NUM>-<NUM> / h of product, it follows that this plant must be able to count on the simultaneous presence of at least <NUM> people.

Another drawback consists in the fact that these operators, and in particular those assigned to the pre-sorting line, are forced to work in unhealthy environmental conditions, as the high quantity of dust, which is released during the handling of the mannocchi or single leaves, cannot be completely removed from the suction devices provided in the work environment.

Another drawback consists in the fact that the various stages of the beating line involve a high consumption of electrical energy, which significantly affects the final cost of the product.

Another drawback consists in the fact that the beating line involves large dimensions.

In order to reduce these drawbacks, it has already been proposed to eliminate the pre-sorting line and to place the tobacco leaf mannocchi directly on conveyor belts which feed the first conditioning cylinder. However, if on the one hand this technique has made it possible to eliminate the operators involved in the pre-sorting line and the encumbrances that this entails, on the other hand it has made the work of the beating line heavier, since it has also subjected the tips of the tobacco leaves, which would not require it and which could have been sent directly to the packaging.

Furthermore, this technique has not eliminated the other drawbacks indicated above.

A method of treating tobacco leaves is also known from <CIT>, which provides for placing the individual tobacco leaves oriented longitudinally on a feed line of a first cutter which cuts them into strips of such a width as to allow their subsequent cutting transversal with a second cutter into strips that can be used directly in a cigarette packing machine.

The strips of tobacco leaves that come out of the first cutter are fed to a first air classification chamber, which separates the portions of lamina only, which are lighter and are fed directly to the second cutter, from the lamina portions still attached to rib portions, which are heavier and are fed to a beating machine (Thresher). This detaches the lamina portions from the rib portions and feeds the whole to a second air classification chamber, in which the separation of the lamina portions from the rib portions takes place, The former are sent to the second cutter, while the latter are fed to a shredder, from which the <NUM> rib fragments are mixed with the strips of lamina coming out of the second cutter to then feed the cigarette packaging machine.

A drawback of this known technique consists in the fact that it requires manually dissolving the mannocchi and feeding the individual tobacco leaves in an oriented manner, that is, aligned with the direction of feeding.

Another drawback, a consequence of the previous one, consists in the fact that the entire treatment of the tobacco leaves requires a large number of operators, with the inevitable high cost of the treatment itself.

Another drawback of this known technique consists in the fact that it does not allow the individual leaves to be cut on a regular basis and consequently requires the product to be subjected to repeated processing steps to be brought to the homogeneous conditions required for the packaging of cigarettes.

The object of the present invention is to eliminate or at least significantly reduce these drawbacks as well.

In particular, the object of the invention is to drastically reduce the personnel assigned to handling the tobacco leaves.

Another object of the invention is to reduce the energy consumption of the apparatuses that carry out that treatment on the tobacco leaves.

Another object of the invention is to reduce the pollution due to the release of dust in the work areas.

Another object of the invention is to reduce the bulk of the treatment plant and in particular of the beating line.

Another object of the invention is to propose a plant for the treatment of tobacco leaves which achieves all the purposes indicated above.

Another object of the invention is to propose a plant which achieves all those purposes without reducing the operating potential of the plant itself.

All these objects are jointly or separately achieved according to the invention with a tobacco leaf treatment method, as defined in claim <NUM> and with a treatment plant as defined in claim <NUM>.

The present invention is further clarified hereinafter in some its preferred embodiments, reported for purely illustrative and non-limiting purposes with reference to the attached drawings, in which:.

As can be seen from the figures, the tobacco leaf treatment plant according to the invention comprises one or more supply benches <NUM>, in which the tobacco leaf mannocchi to be treated are placed.

From these benches <NUM> the mannocchi are transferred by means of conveyor belts <NUM>,<NUM> to a first rotating conditioning cylinder <NUM>, fed with jets of water and steam and subjected to the recirculation of air to increase the humidity of the tobacco leaves and bring them to a value of about <NUM>-<NUM>%, which represents an optimal value to make them more flexible and therefore more suitable for subsequent treatments, to which they must be subjected.

This first conditioning rotating cylinder <NUM> is traditional in itself and is not further described in its details.

Since then the degree of humidity of the tobacco leaves to be treated can vary according to the country of production and the treatments to which they have been subjected previously, as well as the environmental conditions to which they were preserved before being subjected to this treatment, it may happen that they already have the optimal degree of humidity and that this first conditioning is not necessary. In this case the first conditioning cylinder <NUM>, even if illustrated in the drawing, may not be present and the tobacco leaves can be directly transferred from the conveyor belt <NUM> to a shredder <NUM>.

In the example described here, the first conditioner <NUM> is provided and the conditioned leaves that come out of it are transferred by means of a conveyor belt <NUM> to the shredder <NUM>.

The shredder <NUM> comprises an operating unit with two rotors, each formed by a plurality of shaped discs <NUM>, mounted on a shaft <NUM>, and spaced apart to an extent just greater than their thickness, so as to be able to partially penetrate with the discs <NUM> mounted on the other shaft <NUM>. They have a shaped profile which highlights along their circumference of the teeth <NUM>, hook-shaped and cooperating with corresponding teeth <NUM> present in the discs <NUM> mounted on the other shaft <NUM> and partially interpenetrating.

The discs are preferably between <NUM> and <NUM> in number per linear meter of length of the shaft <NUM> which supports them and therefore each disc <NUM> has a thickness of between <NUM> and <NUM>. Furthermore, each disc <NUM> can have a diameter between <NUM> and <NUM> and can have from <NUM> to <NUM> teeth, which can preferably have a height between <NUM> and <NUM>.

The two shafts <NUM> are associated with distinct motors or distinct transmission systems driven by the same motor; in any case, the two rotors are driven at the same <NUM> peripheral speed but in opposite directions and are cyclically commanded to reverse their direction of rotation for the reasons which will become clear later.

In the position above the operating unit formed by the two rotors with the shaped discs <NUM> there is a hopper <NUM> for loading the tobacco leaves to be treated and the two opposite longitudinal walls of this hopper extend below in comb elements <NUM> with inclined teeth and partially interpenetrating with the teeth <NUM> of the respective rotor in order to favor the conveyance of the tobacco leaves towards the rotor itself.

The operating unit of the shredder <NUM> is placed on a conveyor belt <NUM> which feeds the disintegrated material to a second conditioning rotating cylinder <NUM>, similar to the first cylinder <NUM>.

This second conditioning cylinder <NUM> can preferably unload the product onto one or more benches <NUM>, from which the product can be sent to first classification chambers <NUM>, in which the free sheet parts are sent to a collection silo <NUM> and from this to a sheet collection line <NUM>, while the rib parts, to which parts of the lamina are still joined, can be transferred to a traditional multi-stage beating line <NUM>, alternating with classification chambers <NUM> for the complete separation of the lamina portions from the rib portions of the tobacco leaves.

The plant is completed by a lamina drying unit <NUM>, a dried lamina packing station <NUM>, a rib drying unit <NUM> and a dried rib packaging line <NUM>.

The operation of the system described above is as follows:
the tobacco leaf mannocchi to be treated are placed on the feeding benches <NUM> and from there they are transferred by means of the feeding belts <NUM>,<NUM> to the first conditioning rotating cylinder <NUM>, in which they are brought to the optimum moisture content before being transferred to the shredder <NUM>.

Here the bunches of tobacco leaves are subjected to the action of the counterrotating discs <NUM>, which with their teeth <NUM> break up the leaves and tear from these strips of lamina having the rough shape of "squares" with dimensions linked to the thickness of the discs themselves, to the shape of the teeth <NUM> and to the extent of interpenetration between the discs that form the two rotors; indicatively, the squares obtained can have dimensions of about <NUM> x <NUM>.

This operation already leads to a separation of about <NUM>% of the lamina from the remaining part of the leaf and this requires to subject only the remaining <NUM>% of the product to beating, with considerable advantages both in the number of stages of the beating line and in the overall dimensions. of the equipment envisaged therein, and finally in the consumption of electricity.

This <NUM>% of product on which the separation of the lamina from the rib of the tobacco leaves is carried out is treated in the various stages of the beating line <NUM> in the traditional way, in the sense that in the classification chambers <NUM> located downstream of each beating stage it takes place the separation of the lamina (which is discharged into the lamina collection line <NUM>, already fed with <NUM>% of foils generated in the shredder <NUM> and separated from the remaining part of the product in the classification chamber <NUM>)
from the remaining part of the product (which is started at the next typing stage).

At the outlet of the beating line <NUM>, therefore, only pieces of ribs are obtained, which are transferred to the drying unit <NUM> and from this to the packaging station <NUM>, while the foils collected in all the various separation stages are transferred to the drying unit <NUM> and from this to the packing station <NUM>.

Finally, the dried and packaged sheets and ribs can be transferred to subsequent processing.

Claim 1:
Method of treating tobacco leaves for the separation of the leaf portions constituting the lamina from the leaf portions constituting the rib, characterized by the fact that:
- bunches of leaves are placed on a feeding line of a shredder (<NUM>), in which portions of the lamina of each leaf are torn from the remaining part of the leaves, starting from the edge of these,
- the portions of the lamina torn from each leaf in said shredder (<NUM>) and forming portions of substantially sole lamina are separated with air in at least one classification chamber (<NUM>) from portions of lamina attached to portions of rib,
- said portions of sole lamina torn from said leaves are directly transferred to the subsequent drying and packaging processes,
- the portions of lamina attached to portions of rib, are passed through a line of beating (<NUM>) in several stages, in each of which the progressive separation of portions of the lamina from the remaining portions of lamina attached to portions of rib is caused, to obtain at the exit of said beating line (<NUM>) the almost total separation of the lamina from the rib of the leaves,
- the portions of lamina gradually separated from the portions of rib of the leaf are transferred to the subsequent drying and packaging processes,
- the pieces of rib coming out of the beating line (<NUM>) are transferred to the packaging.