Improvements relating to the processing of tobacco leaves.

The present invention relates to the processing of tobacco leaf material for the manufacture of smoking products.

Tobacco leaves of the types used in the manufacture of cigarettes and similar smoking products include a leaf parenchyma, a longitudinal main rib (rib) and veins extending from the main rib. The main rib and the important veins are considered together, in what follows, as a rib. The rib has physical properties which differ significantly from those of the parenchyma and according to a very old practice it is customary to separate the rib from the parenchyma during a preliminary stage in the treatment of tobacco leaves, the rib and the parenchyma then being treated independently and differently.

The separation of the material constituting the rib from that constituting the parenchyma is generally carried out by means of a complex and large threshing plant comprising a number, for example eight, threshing machines arranged in series, with sorting units arranged between neighboring threshing machines.

As is well known, the material of the separate rib or a part thereof is often re-added, after an appropriate reduction in dimensions, to the parenchyma, after this parenchyma has been subjected to another treatment. The rib material is often desirable in the tobacco mixture in order to improve its filling value.

It is an object of the invention to provide an improved method for processing the tobacco leaf material to give a product suitable for use in smoking products such as cigarettes and cigars for example.

We sought to simplify the entire tobacco manufacturing process from the leaf to the product to be smoked.

It has surprisingly been found that it is possible to use a mill to work simultaneously on the rib and the parenchyma to produce a usable product by being incorporated into smoking products. Although it is known that it has been proposed to use a disc mill to reduce the particle size of the rib material by itself, there is no known use of a single mill, wherein a complete sheet is supplied to the mill so as to make it possible to obtain a particulate material which is capable of being used for the manufacture of smoking products without the need for practically an additional process of dimension reduction. However, it has been found that it is possible to use a mill with a complete sheet, as defined below, in order to produce a mixture of particulate parenchyma material and practically intact rib material, the material of the parenchyma having a dimension making it suitable for use, practically without any additional reduction in dimension, in the manufacture of smoking products. Thus, for example, the material of the parenchyma can be supplied to a machine for manufacturing commercial cigarettes such as for example the Molins Mk 9 machine.

By complete sheet is meant complete or substantially complete sheets or alternatively sheets which have been reduced in size by a reduction process, for example by chopping or slicing, which does not entail a significant separation of the parenchyma and the rib. The leaves or leaf portions have generally been hardened and may have been subjected to other more or less usual treatments.

There have been many prior proposals for processing tobacco leaves to obtain a filler for cigarettes and similar smoking products. Examples can be found in the following patents:

Federal Germany

954 136

New Zealand

139 007

Britain

1855/2134; 413,486; 2,026,298; 2,078,085; 2,118,817; 2,119,220 and 2,131,671

United States

173; 68,597; 207,140; 210,191; 250,731; 358,549; 360,797; 535,134; 2,184,567; 3,026,878; 3,128,775; 3,204,641; 3,690,328; 3,845,774; 4,195,646; 4,210,157; 4,248,253; 4,323,083; 4,392,501; 4,582,070; 4 696 312 and 4

706 691.

According to one aspect of the present invention, the subject of the present invention is a process for treating the material of a tobacco leaf in which the tobacco, as a complete leaf, as defined above, is fed through a mill, the arrangement of this mill and the conditions of treatment being such that the mill leaves a product which is a mixture comprising flakes of parenchyma and pieces of rib almost intact, the parenchyma fraction of this product requiring virtually no additional reduction in size to make the parenchyma fraction suitable for incorporation into smoking products.

According to another aspect of the invention, the subject of the invention is a product comprising a mixture of parenchyma particles and pieces of rib which are practically intact, this mixture resulting from the feeding of a complete tobacco leaf, such as defined above, through a mill.

We can supply the mill, together with the i

complete tobacco leaf, additional parenchyma in the form of parenchyma strips.

According to another aspect of the invention, the subject of the invention is a process for treating the material of a tobacco leaf, with a view to obtaining a filling material 20 for a smoking product, in which the tobacco in the form of a complete sheet, as defined above, through a passage delimited by coextensive parts of first and second grinding elements, movable relative to each other, of a mill, from an inlet of this passage to an outlet of this passage remote from the inlet, so as to obtain, at the location of this outlet, a product consisting of a mixture of parenchyma particles and intact rib pieces, the parenchyma particles and the rib pieces being separated, so that the fraction of the parenchyma particles, free of rib pieces, constitutes the filling material. Preferably the outlet opening of the passage is located in the marginal zone of the coextensive parts.

It has been found that the fraction of the rib of the products according to the invention is easily separated from the fraction of the parenchyma. This separation can be achieved, for example, by air sorting.

Advantageously, a gravity feed system is used to supply the material from the sheet to the inlet of the mill.

In some cases it may be advantageous to inject steam at low pressure, for example at a pressure of one bar, into the mill.

The feeding of the sheet material in the direction of the mill can be assisted by maintaining, at the point of the outlet for the product from the mill, a reduced air pressure, for example by using a current or by maintaining a high air pressure at the point where the product enters the mill.

Preferably the feeding of the material from the sheet to the mill should be a continuous feeding. It is advantageous for the feed rate to be substantially constant.

The material of the sheet which is supplied to the mill can be, for example, a Virginia tobacco material dried with hot air, a mixed material of the American tobacco type or even a material dried in air.

According to another aspect of the invention, this relates to a filling material for a smoking product, this filling material being a fluid material consisting of parenchyma particles, the form factor of approximately 70% at least. particles, free of dust, of this material being at least 0.5.

The expression form factor is defined below.

According to another aspect of the invention it relates to a method of manufacturing cigarettes in which the material of a tobacco bale is reduced to provide a discrete whole sheet, as defined above, the whole sheet is brought to pass through a mill so that, from this mill, a product is produced which is a mixture comprising flakes of parenchyma and lengths of rib practically intact, the parenchyma and rib flakes from this mixture are separated, and the parenchyma fraction is passed to a cigarette making machine.

Since the humidity level (of the rib fraction) is relatively low, there is less need for drying the product leaving the mill, which can lead to appreciable savings in terms of equipment and the cost of energy.

A smoke modifying agent, such as for example a tobacco wrapper, can be applied to the material of the tobacco leaf before or after the treatment of this leaf by a process according to the invention.

The materials of the parenchyma in the form of particles obtained according to the invention can be subjected to a process of expansion of tobacco. Examples of expansion processes which could be employed are described in English patents Nos. 1,484,536 and 2,176,385.

It has been found that the moisture content of the whole leaf is generally the main factor which determines, on the one hand, whether intact pieces of rib are produced or, on the other hand, whether particles of rib are produced and that, surprisingly, a sudden transition from one product to another occurs for a relatively precise degree of humidity.

The humidity level at which this transition occurs will be considered below as the transition humidity level.

The transitional humidity level of a tobacco to be ground is easily determined by a simple experiment before the production operation. For a complete sheet of Virginia tobacco it has been found that the transitional humidity level is appreciably 18% when this leaf is ground in a Quester SM11 mill. In other words in this case it is necessary, for a mixture of parenchyma particles and pieces of intact rib to be produced from the mill, that the average degree of humidity is less than 18%. Preferably the humidity level chosen should not have a value much below the transitional humidity level. Thus, for example, in the case where the transitional humidity level is 18%, an average humidity level for food of 16% could be chosen.

Heat can be applied to tobacco to be ground. If heat is applied, for example by subjecting the material to microwave radiation, the value of the transition humidity level tends to be lowered.

The material of the leaf treated by the process according to the invention may be of a single quality of tobacco or else a mixture of materials of the leaves of several qualities of tobacco.

Since a mill used in implementing a method according to the invention is notably more compact than a conventional threshing plant, with its plurality of threshing machines and sorting units and the network of pipelines associated extended air, using the present invention, an investment cost saving is achieved compared to the use of a conventional threshing plant. There is also a saving in terms of the energy consumed. In addition, the savings in investment and energy costs are also increased as a result of the simplification of the primary processing section of the leaf in the tobacco factory. It so happens that by using the present invention there are appreciable savings in the overall treatment of the tobacco leaf, that is to say in the treatment which begins with the tobacco leaf as received from the plantation and which ends with the manufacture of cigarettes or other smoking products.

It should be noted that not only does the invention provide methods for obtaining a mixture of discrete parenchyma particles and discrete rib pieces, without the need to provide a plurality of sheet processing machines arranged in series, but still the invention provides methods which can be easily implemented without requiring a recirculation of the product to achieve an additional reduction in size of the parenchyma fraction of the mixture. In other words, a single pass operation can be easily performed.

The mills which are used in carrying out the methods according to the invention are preferably of the type in which a material flow circuit extends between opposite faces of first and second sheet reducing elements and in across these faces, so that a shearing action is exerted on the tobacco while this tobacco follows the flow circuit of the material. It is advantageous for at least one of the sheet reducing elements to have a discoid shape and in this case it is advantageous for the discoid element or each discoid element to comprise, on its active face, projections extending radially, in generally linear ribs. Preferably the two sheet reducing elements have a discoid shape. Mills which include two sheet reducing elements in the form of discs are, for example, the Bauer model 400 and the Quester model SM11. During operation of the Bauer model 400 mill the two discs are driven in opposite directions while in operation of the Quester model SMll mill one disc is rotated while the other disc remains stationary. A number of discs are available for the Bauer 400 mill, each of these discs being provided with a particular design of projections on its active face. The Bauer plates indicated by 325 and 326 are suitable for implementing the invention.

During the operation of disc mills for the simultaneous grinding of the parenchyma and the rib, the determining factors which intervene on the particle size of the fraction of the parenchyma of the product, are the relative rotational speed of the discs, the dimension of the interval between the discs and the configuration of the grinding projections provided on the active faces of the discs.

It has been found that mills or mills of the type employing an impact action, such as hammer mills, are generally not suitable for performing the desired grinding action.

A Robinson finger mill was examined (model designation - Sentry M3 Impact Disrupter). This mill comprises a rotary disc and a disc-shaped stator, these two elements being provided with circular rows of fingers extending perpendicular to the opposite faces of the two elements. The fingers of one element are nested within the fingers of the other element. The limited experience drawn from the use of the Robinson finger mill has shown that such a mill could be used for practicing the methods according to the invention.

Any aging step can be envisaged with regard to the complete sheet as defined above or else the reduced size material produced by the mill.

The fractions of the parenchyma separated from the products of the invention are fluent materials and generally have a natural slope angle of not more than about 45 ° or even a slope angle of not more than about 35 °, compared to the horizontal plane, when they have a usual humidity level for the manufacture of cigarettes, that is to say 13%.

It has also been observed from the materials of the parenchyma that the form factor of at least about 70% of the constituent particles of parenchyma, free from dust, is at least 0.5. The form factor of at least about 80% of the dust-free particles can be at least 0.5.

We have :

Form factor = 4zrx Area (Perimeter)²

The form that gives the maximum value for the form factor, that is, one, is a circle.

It has further been observed that generally the Borgwaldt filling value of fractions of the parenchyma separated from products obtained by the methods according to the invention is lower than that of the usual, comparable chopped smoking tobacco. However, it has been found, surprisingly, that the firmness of cigarettes comprising, as the majority proportion of the filling agent, such a fraction of the separate parenchyma is comparable to that of control cigarettes consisting of usual smoking tobacco.

The invention can provide parenchyma materials which can be transmitted to a machine for manufacturing smoking products without being subjected to an additional reduction in particle size beforehand or which require only, at most to a lesser extent, such reduction additional particle size. This does not of course mean that a minor proportion of heavy particles and / or a proportion of minor dust cannot be removed from the material of the parenchyma before incorporating this material into smoking products.

When incorporated into cigarettes having been fed to a cigarette manufacturing machine, the parenchyma materials obtained according to the invention have an appearance similar to that of the usual cigarette filling material which is thus incorporated into these cigarettes .

The usual chopped filler which is used in the manufacture of cigarettes is a non-flowing, matted material with long strips. For this reason, the supply unit for cigarette manufacturing machines includes carding means which are used to untangle the filling material. Because the materials of the parenchyma obtained according to the invention are fluid materials, not entangled, consisting of parenchyma particles, the carding means or at least certain elements thereof can be eliminated when the materials in question are incorporated in the cigarettes.

If a process for treating a complete tobacco leaf according to the invention is carried out in a tobacco growing region, the material of the leaf can be what is called a green leaf, i.e. -to say a hardened leaf material as received from the tobacco plantation. However, if the leaf material is to be processed at a tobacco factory remote from the tobacco growing region, it may be convenient to subject the tobacco to a so-called re-drying process. A drying process is used to ensure that the material of the sheet is at a sufficiently low humidity level that it can be adapted for transport and storage at the factory, without there being any deterioration in its qualities.

The use of a complete tobacco leaf as a raw material for the preparation of a filling material for a smoking product, without it being necessary to provide a prior step of separation between the parenchyma and the rib, provides an economic advantage since the whole leaf can be expected to be less expensive to purchase than the separate rib and parenchyma from a threshing plant.

Common procedures can be applied to the materials of the parenchyma obtained according to the invention, in the same way as those applied to a material of the parenchyma treated in the usual manner. For example materials of the parenchyma produced by a process according to the invention can be mixed, in a well known manner, with another smoking material or other materials in any ratio deemed desirable but preferably at least the main part of the smoking material of the resulting mixture consists of a material of the parenchyma obtained according to the invention. Smoking materials which can be incorporated into a mixture, include tobacco, reconstituted tobacco and tobacco substitutes.

At least two materials of the parenchyma obtained according to the invention can be mixed.

In the mixture of a filling material for an American type cigarette, one can mix, 1 ° the fraction of the parenchyma of the product obtained by subjecting a complete sheet of Burley tobacco to a process according to the invention and, 2 ° the product obtained by submitting a Virginia tobacco leaf, having a humidity level higher than the transitional humidity level, in a grinding operation such that the product obtained consists of a fluid mixture of parenchyma particles and rib particles.

The rib fraction of a product according to the invention can be treated, after its separation from the parenchyma fraction, according to conventional steam treatment methods or else it can be discarded.

Various embodiments of the present invention will be described below, by way of nonlimiting examples, with reference to the appended drawing in which:

Figure 1 is a block diagram illustrating a conventional processing of a whole tobacco leaf dried with hot air.

FIG. 2 is a block diagram illustrating the treatment, according to the invention, of a whole tobacco leaf dried with hot air.

FIG. 3 is a histogram giving the relation between the values ​​of the form factor of the particles, (along the horizontal axis), and the frequency of appearance, measured in units of a million (along the vertical axis), in the case of a conventional cigarette parchment filling with chopped parenchyma.

Figure 4 is a histogram giving the same information as that of Figure 3, but in the case where the filling material of a cigarette is a product according to the invention.

Each form factor value represented along the horizontal axes of the histograms of FIGS. 3 and 4 is the upper value of a unit range. So the value

0.4, for example, means that the range extends from the smallest value above 0.3 to a maximum of 0.4.

FIG. 5 is a dispersion diagram giving the relationship between the length of the particles in millimeters (along the horizontal axis) and the form factor (along the vertical axis), in the case of the usual filling material making object of figure 3.

FIG. 6 is a dispersion diagram giving the relationship between the length of the particles in millimeters (along the horizontal axis) and the form factor (along the vertical axis), in the case of the filling material which is the subject in Figure 4.

FIG. 7 shows a mass of usual filling material which is the subject of FIGS. 3 and 5.

FIG. 8 shows a mass of filling material according to the invention which is the subject of FIGS. 4 and 6.

In Figure 1 the reference numerals indicate the following steps:

I - Conditioning / drying

2 - Desanding

- Conditioning

- Threshing

- Coast

- Drying

7 - Packaging

- Coast

- Conditioning

- Mixed

II - Lamination

12 - Hash

- Coast treatment with water

- Drying

- Parenchyma

- Drying

- Packaging

- Parenchyma • 19 - Packaging

- Mixed

- Hash

- Drying

- Mixing and Adding

- Storage of chopped tobacco

- Manufacture of cigarettes

Steps 1-4, 5-7 and 15-17 take place in the tobacco growing region while steps 8-14, 18-22 and 2325 take place in a cigarette factory, such a factory being usually far from the tobacco growing region.

The process performed in steps 8-14 and 1822 constitutes the primary processing section of the factory sheet, this section being sometimes called the primary processing department (DTP). Steps 8-14 are commonly considered to constitute a coast line, while step 18-22 constitutes a parenchyma line.

The word Addition in step 23 relates to the possible addition of other smoking materials in the process of mixing coastline and parenchyma products. Examples of such additional smoking materials are expanded tobacco and reconstituted tobacco.

The input material in step 1 is the whole leaf of green tobacco.

The whole process, from step 1 to step 25, can be changed in detail, but Figure 1 illustrates a typical typical processing of a tobacco leaf to provide a cigarette filler.

In FIG. 2, the numerical references have the following meanings:

- Conditioning / drying 10 27 - Desanding

- Drying

- Packaging

- Complete sheet

- Conditioning

32 - Mixed

- Grinding

- Drying

- Mixing and Adding

- Buffer storage

37 - Manufacture of cigarettes

- Hash

- Coast to water treatment process

- Drying

- Broken parenchyma

42 - Drying

- Mixing and Adding

- Buffer storage

- Manufacture of cigarettes.

Steps 26-29 take place in the tobacco growing region while steps 30-45 take place in a cigarette factory.

The conditioning steps are carried out so as to avoid or practically avoid the elimination of components which can be extracted with water.

The input material in step 26 is the whole leaf of green tobacco.

We will now give details of tests relating to

1'invention.

TEST # 1

The tobacco leaf used in this test was a whole green leaf of single quality, air-dried Canadian tobacco, which was purchased in bales from the plantation with a moisture content of approximately 18%. The bales were sliced ​​using a guillotine slicer in order to provide large sheet portions according to the above definition of the complete sheet, the majority of these portions having a width ranging from about 10 cm to about 20 cm.

The whole sheet thus obtained, having a humidity level of about 18%, was fed by gravity, with a flow rate of 150 kg / h, to a Quester disc mill (model SM11). The rotating disc of the mill was driven at a speed of 1000 revolutions per minute. The rotating disc and the fixed disc or plate which were the standard elements for the SM11 model, included, on their opposite active faces, a design of projections in the form of linear ribs, extending radially.

The mill operated with a nominal interval between discs of 0.15 mm, then with increments of 0.15 mm in the interval between discs until a nominal interval between discs of 0.9 mm was reached. Steam was supplied to the interior of the mill at a pressure of 1 bar.

The product obtained, for each setting of the interval between the discs, was constituted by a mixture of parenchyma particles and lengths of intact rib. In each case the particle size of the parenchyma fraction was judged to be such that this fraction of the parenchyma, after separation of the lengths of rib, was suitable for the manufacture of cigarettes on a conventional cigarette making machine. The rib pieces were clean, that is to say without residual portions of parenchyma remaining attached to it.

TEST # 2

Test No. 1 was repeated except that the nominal intervals between the disks were 0.9, 1.2, 18 and 2.1 mm. The products obtained from the five passes were again formed by a mixture of parenchyma particles and lengths of intact coast. As the interval between the discs was increased, the particle size of the parenchyma fraction increased and it was judged that at least in the passes made with the longest intervals between the discs, some reduction in an additional dimension of the parenchyma fraction would be necessary to make this fraction of the parenchyma suitable for feeding a cigarette manufacturing machine. For the larger settings of the interval between the discs some of the rib pieces had residual portions of parenchyma attached.

TEST # 3

Test No. 1 was repeated with the complete sheet conditioned so as to have a humidity level of 20% and with a feed rate of 330 kg / h. Passes were made with nominal disc gap settings of 0.30 mm and 1.20 mm. When the nominal interval was 0.30 mm, the product obtained was made up of an intimate fluid mixture of parenchyma particles and rib particles. However, the product obtained when the nominal gap between disks was 1.20 mm, was in accordance with the invention and it consisted of a mixture of 10 parenchyma particles and intact rib lengths. It was thus concluded that the value of 20% for the humidity level was below the value of the transition humidity level under the conditions of the experiment, with an interval between discs of 1.20 mm.

TEST # 4

Test No. 1 was repeated with the material of the complete sheet conditioned at a degree of humidity of 21% and with an interval between discs of 1.05 mm. The product obtained was in accordance with the invention and it consisted of a mixture of parenchyma particles and intact rib lengths.

TEST # 5

This test was carried out as in the case of test No. 4 except that the material of the complete sheet was conditioned to a degree of humidity of 24%. The product obtained was made up of an intimate fluid mixture of parenchyma particles and rib particles. It was concluded that the value of 24% for the humidity level was greater than the value for the transitional humidity present.

TEST # 6

The tobaccos used in this trial were three grades of Zimbabwe leaf tobacco, air-dried and re-dried. Each grade was sliced ​​into bales, and the full sheets of the three grades were mixed and conditioned to a target moisture level of 22%. The mixture was then fed, with a nominal flow rate of 300 kg / h, to a disc mill of the Bauer model 400 type, with an interval between discs of 2.54 mm and with a drive speed of 700 revolutions per minute for each of the two discs. The two discs had, on their active faces, a design of protrusions in the form of linear ribs, extending radially.

The product thus obtained was a mixture of parenchyma particles and intact rib lengths. The parenchyma fraction has been found to be suitable for making cigarettes on a common cigarette making machine.

TEST # 7

A 100 g sample of material from the chopped parenchyma of standard American tobacco, screened with hot air, was screened using a screen test apparatus comprising a housing in which are arranged one above the other. five sieves extending horizontally. The nominal openings of the mesh of the sieves are respectively, from top to bottom, of 1.98, 1.40, 1.14, 0.81 and 0.53 mm. The sieve test apparatus comprises reciprocating means intervening to move the housing and the sieves therein in reciprocating motion. The 100 g sample of tobacco was distributed uniformly over the upper sieve and the reciprocating means were put into operation for 10 minutes, and after this period of time the fractions of material found on the four sieves were recovered higher. The fraction on the lowest sieve and the fraction that passed through the lowest sieve formed fine dust and were discarded.

0.5 g subsamples of the four recovered fractions were distributed over respective flat surfaces such that each parenchyma particle was spatially separated from the other particles. Each of the subsamples was then subjected to geometric analysis using a Magiscan Model 2 image analyzer supplied by Joyce-Loebl. The analyzer was adjusted to obtain data relating to the area of ​​the particles (two dimensions), their length (largest linear dimension) and the length of their perimeter.

From the data thus obtained, a histogram was produced relating the form factor of the particles to the frequency of appearance (FIG. 3) and a dispersion diagram linking the length of the particles to the factor of

<td colspan="3">20 shape (Figure 5).</td><td colspan="3">TEST # 8</td>

<td></td><td>We have</td><td>submitted,</td><td>to the procedure</td><td>of</td><td>detailed sieving</td>

<td>in</td><td>tested</td><td>n ° 7, a</td><td>sample of</td><td>100g</td><td>of a fraction of</td>

parenchyma of a product according to the invention, obtained by grinding a whole leaf of American tobacco, dried in hot air, with a humidity of 18%, in the mill

Quester with an interval between discs of 0.3 mm. We analyzed geometrically, as in the case of test No. 7, four 0.5g sub-samples from the four upper sieves, that is to say free of dust.

From the data thus obtained we have plotted 1¹ form factor / frequency histogram and the length / form factor dispersion diagram which constitute Figures 4 and 6 respectively.

A comparison between the histograms of Figures 3 and 4 shows that the parenchyma fraction of the product according to the invention (Figure 4) has characteristics clearly different from those of the current chopped parenchyma (Figure 3). In this regard it can be noted, for example, that in the case of chopped parenchyma, about 80% of the material, after removal of the dust, has a form factor of 0.5 or less while in the case of the parenchyma obtained according to the invention about 90% of the material, has a form factor of 0.5 or higher.

The clearly distinct characteristic of the two materials also appears clearly from the comparison of FIGS. 5 and 6.

TEST # 9

In a 125 ml laboratory beaker, common chopped parenchyma from a mixture of three qualities of Zimbabwe tobacco, re-dried, with a moisture content of approximately 12.5%, was placed without applying any compression pressure external to the material in the beaker. The beaker was then turned over on a flat horizontal surface and the beaker was removed by lifting it vertically. The resulting mass of chopped parenchyma appears as shown in Figure 7. As can be noted, the natural slope angle of the material is about 90 ° relative to the horizontal plane.

TEST # 10

Test No. 9 was repeated using a parenchyma material obtained according to the invention, applied to a mixture of whole leaves of the same three qualities of Zimbabwe tobacco having a moisture content of approximately 12.5%. The mass of resulting material is as shown in FIG. 8. The natural slope angle is then about 33 ° relative to the horizontal plane.

A comparison of Figures 7 and 8 clearly highlights the very different characteristics of the usual parenchyma and the parenchyma obtained according to the invention.