MXPA99005546A - Method and apparatus for processing tobacco - Google Patents

Abstract

A method for processing tobacco comprises threshing tobacco leaves to form a mixture of free lamina, clean stem pieces from which lamina has been completely or substantially completely removed and unclean stem pieces which have useful pieces of lamina attached thereto, sifting to separate the clean stem pieces from the unclean stem pieces and subjecting the unclean stem pieces to additional threshing by recycling the unclean stem pieces to the thresher. The apparatus for carrying out the method may comprise a sieve.

Description

METHOD AND APPARATUS FOR PROCESSING TOBACCO This invention relates to a method and an apparatus for processing tobacco.

In the tobacco industry, it is well known that in order to process tobacco in a form suitable for use in the manufacture of products, the stem of the tobacco must have been removed from the midrib of the rest of the leaf. tobacco (hereinafter referred to as the sheet). This process is generally referred to as threshing.

In current art, the most common leaf threshing process consists of: Feed the tobacco leaves on top of a threshing mill. The leaves are broken by the action of a rotating element, with radially protruding teeth, until they are small enough to pass through a screen fixed at the bottom of the mill. 2 . The hacked leaf is then classified using Ref.: 30581 an air flow in a vertical tower. The lighter material, without stem, rises with the flow of air and is removed from the threshing process. The heavier material, which contains stem falls, under the influence of gravity, down the tower, through the air. 3. This heavy material, which contains stem, is passed to a second threshing mill, and the process is repeated.

The total process usually has between four and six steps of threshing and sorting before all the leaves are removed the stem of the central rib.

At each step the opening size of the sieve at the bottom of the mill is reduced.

This process is illustrated by the flow diagram in Figure 1.

It can be seen from this description that it is not possible to reduce the number of screening steps in use in a process in this way using a recycling system.

The heavy stems would have no means of escape from the recycling and would accumulate in the process, overloading it quickly.

GB 740088, US 2697439, US 3046998 and US 3513858 each describe methods for recycling heavy stems with still adhering sheet. In each of the processes, an air classification system is used to separate the tobacco into three streams p. ex. , sheet, clean stems and stems with still attached foil. Classification systems for three air currents are relatively complicated.

US 3661159 describes the apparatus for removing the stem of tobacco leaves that separates the threshed leaves into light and heavy fractions.

The classification of threshed tobacco leaves into light and heavy fractions is also disclosed in EP-A-0707800, GB-A-2157411 and WO90 / 05034. The apparatus mentioned in WO90 / 05034 includes a screen for separating the larger particles after threshing but leads only to improvements in the classification systems. The present invention solves the problem of allowing the use of a recycling system in the processing of tobacco leaves without the need for a complicated classification system of three air streams.

According to the present invention, there is provided a method of processing tobacco comprising threading tobacco leaves in a thresher to form a mixture of free sheet, clean stem pieces from which the sheet has been completely or substantially completely removed. and pieces of unclean stems having useful pieces of sheet attached to it, sifting to separate the clean stem pieces from the unclean stem pieces and subjecting the unstained stem pieces to additional threshing by recycling the unclean stem pieces to the thresher The unclean stem pieces are recycled to the same thresher in which they were first produced by threshing the tobacco leaves.

The separation of the clean stem pieces from the unclean stem pieces could be carried out at any stage after the threshing step p. ex. , before or after the conventional separation (or classification) of the sheet of the stem-containing material.

Therefore, in a preferred embodiment, the free sheet is removed from the mixture before screening. The term sieving was used synonymously with the term screening in this specification.

In another preferred embodiment, the mixture of sheet, clean stem pieces-and uncleaned stem pieces is sifted to separate the clean stem pieces, the free sheet is removed after the unclean stem pieces which are then subjected to threshing additional.

The threshing of the tobacco leaves could be carried out by conventional methods well known in the art, the sieving of the milled tobacco could be carried out separately from the threshing step. Alternatively, threshing and sieving could be carried out together in a single piece of the apparatus. Such a threshing and sieving apparatus is described in the related European patent application no. 96309198.8 which is entitled "Apparatus and Process for Tobacco Threshing" and has the same presentation date as this application.

Preferably, the free sheet is removed from the mixture or stale pieces not cleaned by air classification which is a conventional technique well known to those skilled in the art.

Screening to separate the clean stem pieces from the unclean stem pieces (either mixed with or without pieces of free sheet) is carried out by using a sieve or similar device. The screen can be of any type known in the art, preferably it is a cascade type or rotary type with clean sides, which are less inclined for malfunction as a result of blocking the screen. The size of the screen used in the sieve will depend on the size and type of leaves to be processed, but commonly the size of the opening in the screen will be between 10 and 100 mm.

The type of screen used in the screen can be of any type known in the art.

The tobacco entering the process could optionally be cut into sections through the stem before threshing, usually referred to as cutting or striking contact, and the unclean stems could be cut into shorter lengths before being threshed with tobacco leaves not trite. The shorter stem length improves the screening of clean stems after they have been threshed.

The invention also provides the apparatus for processing tobacco comprising threshing means for threshing the tobacco leaves to form a mixture of free sheet, clean stem pieces from which the sheet has separated completely or substantially completely and the unclean stem pieces having useful pieces of sheet attached thereto, wherein the apparatus further comprises the screening means for separating the clean stem pieces from the unclean stem pieces and the means for returning the stem pieces not clean sifted to threshing medium. The screening medium is preferably a sieve. The means for returning unstained stem pieces to the threshing medium could comprise a conventional conveying device such as a conveyor belt.

By the term clean stem pieces, it is indicated that the stem pieces are not attached to useful sheet pieces that could relatively easily be separated from the stem in a threshing process. Similarly, the term "unclean stem pieces" refers to stem pieces that have useful sheet parts attached.

The nature of clean stem pieces will depend on the opening size of the sieve used in the sieve. When the opening size is low, the amount of sheet attached to the stems passing through the screen will be small, typically less than 1% of the total sheet entering the process. When the opening size is large, the amount of sheet attached to the stems that passes through the screen will be larger, up to 20% of the total sheet entering the process, but is preferably not more than 10% of the total of film that enters the process.

When the stems produced are clean or contain a very small amount of bound sheet, they can be removed from the threshing process and passed without further processing to a drying step or other process.

When the amount of blade still attached to the stems is greater or when totally clean stems are required for drying or further processing, they can be first passed to a final polishing process. The final polishing process may consist of any type of threshing process known in the art. Preferably, it consists of a simple conventional thresher and conventional single or extra conventional thresher, sorter and screen with a small opening screen as described in this application, or carried out using the apparatus described in related application no. 96309198.8.

Stems not clean, p. ex. , stems that are still attached to relatively large pieces of sheet, can be recycled to any of the previous threshing stages.

The main advantages of the present invention are as follows: 1) The number of unit processes in a threshing plant can be reduced. 2) The average sheet size produced from the process is larger. 3) Fewer fibers of stem and powder are produced in the process.

The first of these advantages arises from the recycling process using the preferred apparatus of the invention where up to 90% of the sheet can be removed in the first threshing stage, compared to less than 70% in a conventional one-step process.

The second of these advantages results from the fact that the invention allows the stems to be recycled with large pieces of bonded sheet, in a thresher with a large opening screen at the bottom of the mill. Then the large pieces of sheet that are free of stems have not been broken anymore to escape through the screen.

The third of the benefits arises from the effect of the process in reducing the number of times the stems have to pass through the thresher. Most stems will pass through a thresher only twice, or three times when a final polishing step is used, instead of the four to six times the stems go through a thresher in a conventional threshing process .

The threshing medium and sieving medium are preferably provided in a single combined sieving and screening device, as set forth in European patent application no. 96309198.8. the device comprises rotating separation means and a feeder comprising a pair of cooperating elements that rotate in the opposite direction to release the tobacco leaves to the separation means, the feeder and the separation means are arranged in such a way that, in the use , the tobacco leaves undergo shear forces as they pass between the elements rotating in the opposite direction to the rotary separation means which at least partially forces the leaf from the stem.

The separating means comprises radially extending arms. The arms could be in the form of continuous plates or spaced teeth (which can be straight, bent or curved) and could include parts that are capable of cutting tobacco leaves or are capable of boring the leaf and completely tearing the leaf.

The elements also preferably comprise radially extending arms which could also be in the form of straight, curved or bent continuous plates or spaced teeth, optionally including parts that are capable of cutting the tobacco leaves. Alternatively, the feeder elements could comprise a pair of rollers or could consist of a flexible membrane wound around a structure that allows varying amounts of sheets to be fed.

The arms could be flexible, inflexible or a mixture of fixed and flexible components.

The rotating elements and the separation means can take the same shape and could be of equal shape and size, differing only in their function dictated by their position in the device.

The separation means and the feeder are arranged at a relatively close distance from one another to subject the tobacco to the cutting forces that at least partially separate the sheet 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 part of the separation means is less than 100 mm. Cutting forces are experienced by the tobacco leaves as they are directed from the feeder to the rotary separation means. The tobacco leaves are preferably released to the rotary separation means substantially along a radius of the axis of rotation of the separation medium. The sheet is separated from the stem in the region where the leaves pass from being moved under the influence of feeding to move through the separation means and, as an expert will appreciate, the exact position of this region will vary depending on the particular configuration of the device and the rotation speed of its various rotating components. The cutting force can be considered, at least in certain circumstances, as increasing by the action of the cutting means in a part of the leaves while the feeder accommodates another part of the leaves.

Preferably, when the arms of the separation means and those of the elements consist of spaced teeth, the teeth are interengaged. With such an arrangement, the separation of the leaf from the stem is effected, to some degree, by the interaction of the separation medium and the feeder. When the teeth are interengaged, the distance between the teeth as they pass from one to the other is typically less than 100 mm.

The device preferably comprises a rotating drum in which the separating means and the feeder are arranged. The drum comprises a screen (eg, in its walls) which allows the cleaned stem pieces to be sifted and passed out of the drum. The screen can form all or only part of the side walls of the drum.

The drum preferably incorporates fins that exit internally to direct the tobacco leaves to the elements of the feeder. As the drum rotates, the fins collect the tobacco leaves so that the leaves travel in all directions from the inside of the drum until they fall (preferably only under the influence of gravity) in the feeder. The positioning of the feeder inside the drum and / or the speed of rotation of the drum are adjusted to ensure that an adequate amount of the tobacco leaves are released to the feeder as the drum rotates.

The separation means and the elements preferably rotate on axes that are parallel to the axis of rotation of the drum. Preferably, the axes of rotation are substantially horizontal or inclined from 0 to 10 ° (more preferably 2 ° to 6 °) to the horizontal.

The device may comprise more than one separation means (eg, two) and the extra separation means may be provided by one or more additional rotating elements. These additional elements could carry out a. degree of threshing and / or cutting of the tobacco leaves and could participate in the release of the partially threshed and / or untrimmed leaves to the feeder and / or to the separation means. The device could also comprise additional rotating elements that act solely to direct the sheet material within the separation means.

The separation medium and elements can converge as they approach the end of the drum outlet and take into account the reduced load that results from small particles being sifted out of the main flow. This also allows the amount of threshing that is carried out to increase toward the end of the drum outlet. This convergence can be achieved by varying the diameter of the separation means and / or the elements along their length. Adopting this method, an additional effect will be to increase the tangential velocity of the tips of the arm as the diameter increases and this will affect the threshing characteristics.

The diameters of the separation medium and the elements (as defined by the end of any of the radially projecting arms) are typically from 5 to 50% of the diameter of the drum.

The tangential velocity of the drum is preferably in the range of 0.04 to 0.5 m / s * - with the tangential velocity of the separation medium and the elements being 3 to 250 times (preferably 10 to 100 times) greater than that of the drum.

The rotating components of the device (different from the drum) can run at synchronized speeds to obtain true interengranado of the separation means and the rotating elements. Alternatively, the rotating components can run in such a way that they have different tangential speeds, thus establishing cutting actions between the various rotating components. The choice of rotational speed and mode of operation depend on the design of the rotating component and the drum protrusions used and this in turn depends on the nature of the sheets to be threshed and the required specification of the threshed material.

The invention will now be described, by way of example only, with reference to the accompanying examples where: Figure 1 is a flow diagram showing a conventional threshing process; Figure 2 is a flow diagram showing the process of one embodiment of the invention; Figure 3 is a flow chart showing the process of another embodiment of the invention; Figure 4 shows a cross-section through threshing and sieving device for use in a preferred embodiment of the apparatus of the invention; Figure 5 shows a cross-section through a device for use in a preferred embodiment of the apparatus of the invention; Figure 6 shows a cross section through another screening and sieving device for use in the invention; Figures 7 and 8 show perspective views of separation means suitable for use in the threshing-and sieving device; Figure 9 shows perspective views of three types of arm and / or teeth for use in the threshing and sieving device; Figure 10 shows a cross-sectional view of another separation means for use in the threshing and sieving device; Figure 11 is a side view of another separation means suitable for use in the threshing and sieving device; Y Figure 12 is a schematic representation of a preferred embodiment of the process of the invention.

Referring to Figure 1, the tobacco leaves are conditioned and subjected to a series of alternating threshing and sorting steps. The process shown in Figure 1 has five steps of threshing and sorting, each of the separation steps after the first is carried out in a threshing mill with a smaller opening in the screen of the bottom of the mill that the of the previous threshing stage. The free sheet obtained from the separation step is collected for drying-or further processing. Stem material remaining after the final sorting step will also be sent for drying or further processing.

Figure 2 illustrates the embodiment of the invention in which the mixture of sheet and stem-containing material is separated directly after threshing. The conditioned sheet is threshed and the resulting mixture is separated by screening to provide a fraction of screened tobacco and a large fraction of tobacco. Screening causes the stem pieces from which the sheet has been completely or substantially completely removed (eg, clean or nearly clean stems) to pass through the screened tobacco with the stem pieces having relatively large pieces of lamina attached to it (eg, unclean stems) that remain with the large tobacco. Both tobacco fractions are treated by air classification and "light" fractions (eg, lighter material) are sent for drying or further processing. The "heavy" (eg, the heavier material) of the screened tobacco, which includes pieces of clean or nearly clean stem, is sent for drying or further processing, optionally after polishing. The "heavy" ones of the large tobacco fraction contain the unclean stem pieces with relatively large pieces of sheet attached to it and are recycled for additional threshing. Thus, recycling becomes possible by separating clean stem pieces.

Figure 3 illustrates another embodiment of the invention in which the separation of the clean or nearly clean stem material is carried out after air separation of the threshed mixture. The tobacco leaf is conditioned, sieved and treated by means of separation with air to obtain "light" and "heavy" fractions. The "light" fraction contains mainly free sheet and the "heavy" fraction includes the material that contains stem. The "light ones" are sent for drying or additional processing. The "heavy ones" are separated by screening to provide a fraction of heavy screening and a large fraction of heavy. The heavy screen fraction contains pieces of clean or almost clean stem that are dried (optionally after polishing). The large heavy fraction contains unclean stem pieces that have relatively large pieces of sheet still attached and are recycled to the threshing process for the removal of these sheet pieces.

Referring to Figure 4, the drum 6 rotates about a substantially horizontal axis in a counter-clockwise direction. A series of raised tips (or fins) 7 are joined on the inner surface of the drum 6. The function of the tips 7 is to move the tobacco leaves to the upper side of the drum 6. The sheets are then stacked by rotating cooperating rotating elements. against 1 and 2 forming a feeder for the leaves. The elements 1, 2 contain arms radially extending the, 2 a running along the entire length of the drum. In an embodiment of the invention shown in Figure 4, the arms la, 2a are as shown in Figure 8. The sheets are forced between the elements 1, 2 where some tearing or cutting of the sheets could be carried out. The sheets are released from between the elements 1, 2 in the separation means 3 having arms 3a. The separating means 3 rotates in the same direction as the drum of the Figure, p. ex. , in the counter-clockwise direction, although it could rotate in the opposite direction. It is in this region of release of the leaves of the elements 1, 2 to the arms 3a of the separation means 3 that the main part of the screening is carried out according to the leaves that are still partially held by the elements 1, 2 are torn by the cutting action of the separation medium 3. The separation means 3 could also act to cut the leaves to some degree. The sheets threshed by the separation means 3, excluding any part of the threshed sheet that could have broth at the bottom of the drum 6, are piled between the separation means 3 and the element 4 which is located more on the periphery of the drum 6 ( in the direction of its rotation) and are forced into the second separation means 5 creating a second cutting zone inside the drum. The rotational direction of the rotating elements 1, 2, 4, the separation means 3, 5 and the drum 6 are indicated by the dotted arrows.

Another embodiment of the device is illustrated in Figure 5. Here the sheets are transported towards the upper part of the drum 10 in the fins 11 by means of the rotational movement of the drum 10 (counterclockwise in the Figure). The sheets are dragged in the space between the counter-rotating elements 13 and 13 which run along the drum 10 and cooperate to act as a feeder which directs the sheets in the separation means 14. The main function of the separation means 14 is to cut or tear the free blade from the stems of the leaves. The separating means 14 and the elements 12, 13 have bent arms 14a, 12a, 13a and are of the general design shown in Figure 7. An alternative design for the arms 14a, 12a, 13a is illustrated in Figure 10.

In Figure 6, the drum 20 rotates counter-clockwise and, in use, the flaps 21 transfer the tobacco leaves to the counter-rotating elements 22 and 23. The differentially-designed arms 22a and 23a of the elements 22 and 23, respectively, feed the leaves to the separation means 24 having arms 24a. The arms 24a interengage with the armrests 23a. The fixed element 25 captures the threshed tobacco as it leaves the separating means 24 and allows it to fall to the bottom on the inner surface of the drum 20.

In Figure 9, the arms la, 2a of the feeder and / or the separating means could have a flat edge. Alternatively, as shown for the arms 23a, 24a, the outermost edge of the arms could be narrowed to a point and could taper from one end to the other narrower end along the direction of the drum to assist in cutting the leaves.

The device could run continuously or in a batch process, for continuous operation, the tobacco leaves are fed at one end of the drum, the sheets are threshed along the length of the drum and the threshed leaves that have not passed to the outside of the drum (e.g., through the screens in its walls) come out of the drum at the other end. The passage of the sheets from one end of the drum to the other can be achieved by tilting the drum and, optionally, also the rotating components of the apparatus at an angle to the horizontal or by including a spiral screw 15 in the apparatus, as shown in Figure 9. The spiral screw may constitute the separation means and / or the rotating elements of the apparatus.

Alternatively, the transfer of the sheet material down the drum can be effected by arranging the fins helically inside the drum or the transfer can be caused by air currents acting on the sheet material.

To assist in the transfer through the drum, a fixed or rotating element running down the drum parallel to the separation means could be used to retard the tobacco leaving the separation means. The tobacco so delayed will then be able to fall under the influence of gravity on a lower portion of the surface of the drum. Preferably the tangential speed of the additional rotary element is similar to that of the drum (eg, ± 50% of the drum speed) and it is also preferred that the additional rotary element have a direction of rotation opposite to that of the drum.

Referring to Figure 12, the fresh conditioned tobacco is fed via the conveyor 31 into the threshing / sieving device 32. the threshed tobacco containing the unclean stems and the free sheet "too large to pass through the screens of the sieving is transported via 33 to the sorting system, 34, 36 and 37, the light free sheet is collected at the collection points 35 and 38, the unclean stems are recycled, via 39 and 40, returning to the conveyor 31 and feeding back to the threshing / sieving machine 32. The clean stems and the free sheet that is too small to pass through the sieving screens are collected on the conveyor 41 and transferred via 42 to the 43 sorter. light free sheet is collected at 44, and the clean stems are transported, via 45, to the polishing thresher 46, the polished stems and the remaining free sheet are transported, via 47, to the sorter 48, where the Mine remaining light is collected at 49, and the stems are collected in heavy polished 50.

The threshing / screening device 32 shown in Figure 12 can be replaced by a conventional thresher and screen operating together.

The apparatus shown in Figure 12 can be reduced by replacing the threshing / screening device 32 with a conventional thresher, removing item 41 to 45, introducing a screen 'after the sorter 37 after the stems are recycled via 39 and the stems clean are transported to the polishing thresher 46.

The following non-limiting example illustrates the invention.

EXAMPLE Using the apparatus illustrated in Figure 5 with separation elements - as shown in Figure 10 with a 50 mm mesh fitted as the drum screen, the whole tobacco leaf samples are processed in batches. Each sample after the first includes the recycled material from the previous sample. In this way it was possible to imitate the effects of continuous processing. By the fourth sample a steady-state condition had been reached p. ex. , the mass of material that leaves the process was equal to the mass of new material that entered the process. The mass of the recycle was 83% of the mass of new material that entered the process. The tobacco that passed through the screen was sorted and the portion containing the heavy stem was polished in a conventional threshing machine adapted with a round hole basket of 20 mm in diameter. The sheet recovered from the thresher was 5.9% of the total sheet recovered. The total sheet recovered from the process contained 84.4% greater than 12.7 mm and 5.1% less than 6.4 mm.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (11)

1. Method for processing tobacco, characterized in that it comprises threshing tobacco leaves in a thresher to form a mixture of free sheet, clean pieces of stem - from which the sheet has been completely or substantially completely removed and unclean stem pieces having useful parts laminated to the same, sift to separate the clean stem pieces from the unclean stem pieces and submit the non-cleaned stem pieces to additional threshing by recycling the uncleared stem pieces to the thresher.

2. Method as claimed in the claim, characterized in that the free sheet is removed from the mixture before sifting.

3. Method as claimed in claim 1, characterized in that the mixture is screened to separate the clean pieces from the, and the free sheet is removed after the non-clean parts.

4. Method as claimed in 3, characterized in that the threshing and sieving is carried out in a single step of the process

5. Method as claimed in claim 4, characterized in that the threshing and sieving is carried out in a device comprising separating and rotating means and a feeder comprising a pair of cooperating elements that rotate in a manner found to release the leaves of tobacco to the separation medium.

6. Method as claimed in any of claims 1 to 5, characterized in that the sheet is removed from the mixture or the stems pieces are not cleaned by air classification.

7. Apparatus for processing tobacco, characterized in that it comprises threshing means for threshing tobacco leaves in a thresher to form a mixture of free sheet, clean pieces of stem from which the sheet has been completely or substantially completely removed and pieces of stalk not cleaned they have useful pieces of sheet attached thereto, wherein the apparatus further comprises screening means for separating the clean stem pieces from the unclean stem pieces and means for returning the unclean stem pieces to the threshing medium.

8. Apparatus as claimed in claim 7, characterized in that the sieving means is a screen.

9. Apparatus as claimed in claim 7 or claim 8, characterized in that the means for returning unstained stem pieces screened to the tril-side means comprises a conveyor belt.

10. Apparatus as claimed in any of claims 7 to 9, characterized in that the threshing and sieving is carried out in a single device.

11. Apparatus as claimed in claim 10, characterized in that the device comprises rotary separation means and a feeder comprising a pair of cooperating elements that rotate in a manner found to release the tobacco leaves to the separation means.