WO2006030158A1

WO2006030158A1 - Scutching device

Info

Publication number: WO2006030158A1
Application number: PCT/FR2005/050736
Authority: WO
Inventors: François Asselin; Thierry Goujon
Original assignee: Centrale Liniere Cauchoise; Terre De Lin
Priority date: 2004-09-14
Filing date: 2005-09-13
Publication date: 2006-03-23
Also published as: FR2875244A1; EP1789612B1; ATE447054T1; DE602005017408D1; FR2875244B1; EP1789612A1

Abstract

The invention relates to a scutching device, comprising transport means for stems in a transport direction (X), essentially perpendicular to the orientation of the stems, with at least one gripping and driving means (60), for said stems and at least one breaker unit (30), comprising at least one pair of fluted superimposed breaker rollers (31-35). The invention is characterised in that for each breaking unit (30), the upper and lower rollers of each pair of breaking rollers (31-35) are driven in rotation in a synchronised manner, the flutes of the upper roller engaging without contact between two flutes of the lower roller.

Description

Scutching device

The invention relates to the technique of scutching flax or any other cellulosic fiber that can be dyed, such as a bast fiber, such as hemp, kenaf, jute or ramie.

In known manner, the scutching operation, or shelling, is intended to mechanically treat, after retting, the flax stems to separate the fibers (or tow) from the other parts of the plant (the head, containing the straw and the sponge). seed, and the woody parts of the stem or shoots). These fibers are then combed to further remove shives and short fibers or tow, before clearing long fibers having the qualities required for their subsequent use, especially in spinning.

Conventionally, this scutch comprises firstly a scraping step during which a steel tooth comb will separate the capsule from the stem or straw.

Then there is a grinding step followed by a turbining step.

Grinding refers to the step during which the cohesion of the rod is broken by grinding between pairs of rotating corrugated rollers arranged in meshing, and whose axes are parallel to the rods advancing in sheet, in order to break the lignin and allow the extraction of shives.

The turbining effects this separation between the fibers and the shackles by the shocks generated by means of steel blades movable in rotation along an axis perpendicular to the direction of the rods and which strike successively all the portions of the rods.

More particularly, the present invention relates to the improvement of the operation of extraction of shives, namely woody waste linseed, to allow an increase in the amount of this waste, namely a decrease in fiber loss.

Indeed, it is understood that the grinding operations and turbinage generate shocks and intense shear stresses on the stem of flax, these very violent operations are considered until now as necessary to remove the shingles, given the very important mechanical strength of flax fibers. However, this method causes breaks in the long fibers, which generates the short fibers called tows, which must be separated from the intact long fibers, which reduces the extraction efficiency of long fibers. The latter reaches about 20% whereas the total amount of fibers contained in the stems is estimated at 30%.

It is therefore an object of the present invention to allow the separation between the shives and the fibers of the flax stems, while reducing the rate of rupture of the fibers, and this in order to keep at the end of scutching a maximum of long fibers.

For this purpose, the present invention provides a device for scutching flax or any other plant whose stem contains cellulosic fibers that can be separated by scutching, comprising, in the usual manner,: - transport means rods in a direction d drive substantially perpendicular to the orientation of the rods, which comprise at least one gripping and driving assembly of said rods, and - at least one grinding unit comprising at least one pair of corrugated superposed grinding rollers. Typically, in the scutching apparatus according to the present invention, for each grinding unit, the upper and lower rollers of each pair of grinding rollers are rotated synchronously, the splines of the upper roll being meshing, without contact, between two grooves of the lower roller.

With this essential arrangement, it is understood that the grinding of the rods without the risk of breaking by pinching the rods at a location corresponding to a contact between the flutes, which would contribute to break fibers along their length and what would be detrimental in terms of output fiber output.

Overall, thanks to the arrangement according to the present invention, it is possible to improve the extraction efficiency of the fibers of the flax stems in a simple and effective manner.

Advantageously, for each pair of grinding rollers, the lower roll is movable in a substantially vertical tilting movement between a low position spaced from the roll upper of the corresponding pair, and a high meshing position with said upper roll: in this way, by controlling the lower roll rather than the upper roll, one can avoid gripping problems in case of jamming or when the control of the relative position of the rollers is inoperative and that it is desired to spread the rollers.

In particular, preferably, said lower roller is made movable by an assembly formed of a pneumatic cylinder and a lever arm, the presence of a pneumatic cylinder making it possible to very easily release the gap between the lower and upper rollers. .

In addition, preferably, said assembly is associated with an adjustable stop against which said assembly bears in said meshing position, whereby it ensures the absence of contact between the grooves of the upper roller and the grooves of the lower roller. . In addition to the aforementioned essential arrangement, preferably, the splines are shaped so that when a groove of the upper roll meshes between two splines of the lower roll, there is a substantially constant gap between said groove of the upper roll and said two grooves of the lower roller.

Thus, it is understood that a constant maximum stress is exerted on the fibers for a given pair of grinding rollers and, preferably, also for all pairs of grinding rolls.

According to a preferred embodiment, the size of the grooves of the grinding rollers decreases from upstream to downstream along the scutching device.

In this way, by reducing as the progress of the rods in the scutching device the size of the grooves of the grinding rollers, grinding is also carried out more and more finely, which allows to take off the shoots at deeper of the stem. This gradual decrease in the size of the flutes can be achieved in different ways.

According to another preferred arrangement, said scutching device comprises at least three successive grinding units and at least three gripping and driving assemblies, each grinding unit comprising at least three pairs of grinding rollers disposed upstream to downstream and each grinding unit being associated with one of said gripper and drive assemblies, and said successive gripping and driving assemblies have laterally offset drive directions between a gripper assembly and a drive and the next.

This arrangement, which provides for a succession of several scutching units, each comprising a grinding unit and a cleaning unit located downstream, makes it possible to carry out the crushing and cleaning steps in succession successively and several times, so that the waste is disconnected from the fibers by a grinding step are removed as the fibers by the subsequent cleaning step before the rods are again subjected to a grinding step, etc .; and this several times in order to result in fully cleaned fibers of the shives, while having kept a maximum of intact fibers, that is to say unbroken. Preferably, from one milling unit to the next, each milling unit comprises rollers whose groove size is smaller than in the milling unit which precedes it, according to the drive and upstream direction. downstream. This arrangement can be achieved with, for each of said grinding units, rollers whose grooves are substantially the same size in a grinding unit considered, but a size smaller than that of the grooves of the rollers of the preceding grinding unit. This arrangement can also be obtained with grinding units which comprise rollers having, for the same grinding unit, different spline sizes, possibly with the same size between the last roll of the upstream grinding unit and the first roll of the grinding unit. downstream milling unit that succeeds him.

According to another preferred arrangement, said gripping and driving assembly comprises a pair of endless moving belts, flat and toothed, coming into contact with one another to clamp a section of the rod to train during the movement of the belts.

In this way, the retention of the rods is carried out very simply, without exerting on them too great localized pressure at the location of the section of the rod clamped between the moving belts, as may be the case with the prior art devices that use conveyor belts with a U-section.

Preferably, for each scutching unit, the linear running speed of the toothed belts is adjusted according to the linear speed of rotation of the pitch diameter of the splines of the grinding rollers.

Also, advantageously, the smallest grooves have, in section, a shape of M: this shape facilitates during crushing the folding (shearing) of the entire thickness of the rods to facilitate the breakage of cohesion between the shives and fibers.

According to a further preferential arrangement, the scutching device according to the present invention further comprises, downstream of the grinding unit and in an area situated above said gripping and driving assembly, a fiber cleaning unit comprising means for projecting fluid and / or particles downwards towards the rods, whereby the waste separated from the rods by the grinding unit is extracted from the rods which are retained in the said gripping assembly and training.

In this way, it is understood that by the presence of said fiber cleaning unit operating by projection, the fibers of the rods are cleaned by the fact that the shins which have been separated from the fibers during the preceding grinding step, are, thanks at this projection, "peeled" and separated fibers to be driven by the flow of fluid and / or particles that is projected, and then are driven by gravity or by Venturi effect or in any recovery system.

This solution also has the additional advantage of being simple to implement, and particularly compact.

The fluid may be a liquid or a gas and the particles will be in particular abrasive particles such as sand or fine shot.

Preferably, said projection means comprise at least one nozzle for blowing air under high pressure, the air being sent at a pressure preferably of between 1 and 10 bar, ie between 100,000 and 1,000,000 Pa, and advantageously between 4 and 7 bars, or between

400,000 and 700,000 Pa. Preferably, said projection means comprise at least one projection nozzle of sand, shot, seeds and / or other particles.

According to a preferred arrangement, said projection means are located at least on either side of said gripping and driving assembly, and this in order to clean the rods over their entire length, except the zone of the rod situated in said assembly gripping and training.

Other advantages and characteristics of the invention will become apparent on reading the following description given by way of example and with reference to the appended drawings in which:

- Figure 1 is a partial view in projection from one side of a linen scutch device according to the invention;

- Figure 2 is a schematic top view of the flax scavenger device of Figure 1, comprising five scaler units offset transversely one after the other along two parallel lines;

- Figure 3 a side view of a portion of the scutching device of Figure 1, in the form of one of the scutching units;

- Figure 4 shows from above the portion of the scutching device visible in Figure 3;

- Figure 5 is a partial view, in simplified perspective, of the portion of the scutching device visible in Figures 3 and 4, showing the treatment of flax stems;

FIGS. 6A, 6B and 6C each show, in projection from the side, a pair of grinding rollers provided with splines, each pair of grinding rollers having splines of different size;

FIGS. 7A, 7B and 7C show in an enlarged manner meshing without contact between the two rolls of the pairs respectively illustrated in FIGS. 6A, 6B and 6C;

- Figure 8 shows, in projection from the downstream end, a scutching unit and in particular the fiber cleaning unit, and

FIG. 9 is an enlarged partial view of the fiber cleaning unit of FIG. 8. FIGS. 1 and 2 show an embodiment of a linen scutch 10 according to the present invention. In the case of this particular embodiment shown, the linen scutching device 10 comprises, in the longitudinal direction X, five linseed scutching units 11, 12, 13, 14 and 15.

These five flax scutching units 11 to 15 operate on an identical principle shown in FIG. 5, each of these scutching units 11 to 15 having the same visible structure in FIGS. 3 and 4 which will be described in more detail below. .

In all of these Figures 1 to 5, the direction of advance of the flax rods is from the left to the right forming respectively the upstream and downstream.

Each of the scraping units 11 to 15 has a generally identical structure formed of four main parts comprising from upstream to downstream respectively:

an inlet zone 20, a grinding unit 30,

a fiber cleaning unit 40, and

an exit zone 50.

As can be seen in FIGS. 1 and 2, the outlet zone 50 of the scutching unit 11 is situated, in the longitudinal direction X, of the entry zone 20 of the scutching unit 12 which is located downstream of the previous scutching unit 11.

Indeed, the scutching units 11, 12, 13, 14 and 15 are successively arranged one after the other in the longitudinal direction X while being offset transversely in the Y direction with respect to the neighboring scutching unit. that all the sections of the stem of the plant are treated as will be exposed hereinafter. Each scraping unit 11 to 15 is traversed by a drive system 60 with an endless double belt 61 and 62.

As shown in Figure 3, the two endless belts 61 and 62 are notched flat belts forming a closed loop around two pulleys 63 (65) and 64 (66). The two loops delimited by the belts 61 and 62 are arranged one above the other so as to wedge between them a web 100 of linen stems (see FIG.

4) which remains sandwiched between the portions of the belts 61 and 62 which are in close contact with one another and which form a gripping zone 60a. More specifically, the flax stems are held by the belts 61 and 62 which have relief facing faces in the form of a notch.

As can be seen more precisely in FIG. 2, between two successive scutching units (for example the units 11 and 12), the outlet area 50 of the first scutching unit 11 being disposed next to (along the longitudinal axis X ) of the entry zone 20 of the following scutching unit

12, it is provided by a transverse shift (in the Y direction) of the drive system of the two successive scutching units having the two belts 61 and 62, a continuity of transport of the linen web.

100 between the drive system 60 of the scutching unit 11 to the drive system 60 of the following scutching unit 12 which hold respectively the flax stems at two adjacent sections of these stems, which sections are located in the central part of the flax stem as can be seen in Figure 4 which is partially shown a sheet 100 of flax stems.

The inlet zone 20 of each scutching unit 11 to 15 has the double-belt drive system 61 and 62 shown above, so that this entry zone 20 only ensures the advancement of the ply 100 of the stems. linen.

Referring to FIGS. 3 and 4, the grinding unit 30 of each scooping unit 11 to 15 is equipped with five pairs 31 to 35 of superposed fluted grinding rolls.

More specifically, referring to the first pair of grinding rolls 31, it comprises an upper grinding roll 31a and a lower grinding roll 31b whose axes are respectively disposed above and below the zone 60a of toothed belts 61 and 62, each of these rollers 31a and 31b being itself (see Figure 4) formed of a section 31bl located on one side of the gripping zone 60a and a section 31b2 located on the other side of the gripping zone 60a.

In this way, it is understood that the processing of the linen web 100 is carried out simultaneously to the right and left of the drive system 60 in order to carry out the grinding, at each pair of grinding rollers 31 to 35 along the entire length of the stems of linen, with the exception of the section of the flax stems which is held between the belts 61 and 62.

It is therefore understood that at each scutching unit 11 to 15, the sheet 100 of the flax stems passes successively in several (in this case five) pairs of grinding rollers 31 to 35 which perform the crushing and folding woody parts of the flax stalk (or shives) in order to separate them from the fibers that one wishes to isolate and keep in the least altered way possible.

In practice, during this grinding treatment, as it appears in FIG. 5, the sheet 100 of linen stem initially forming a fairly coherent set of rods parallel to each other, successively becomes more flexible so that the stems of linen, as and progress in each pair of grinding rollers 31, 32, 33 ..., relax and hang on both sides of the gripping area 60a. Therefore, the central section of each rod is held between the belts 61 and 62 while the ends of the rods are located further back and are still locked between the grinding rollers. The treatment of the central portion of the rods being effected, on either side of the belts 61 and 62, at the rate of advance of the belts 61 and 62, while the ends of the rods being free, they follow this treatment slightly backwards. (upstream in the longitudinal direction X) of the central part of the rod.

In Fig. 5 there are shown only three pairs 31 to 33 of grinding rolls for grinding unit 30 while Figs 1 to 4 illustrate scraping units 11 to 15 which each have five pairs 31 to 35 grinding rolls. .

Thus, generally according to the present invention, each scutching unit may comprise a number of pairs of grinding rolls that are identical or different from each other, the number of pairs of grinding rolls of each scutching unit may vary from three to five (or more) pairs of grinding rollers.

Conventionally, the pairs of grinding rollers used for scutching flax are rolls with teeth or gear splines coming into contact with one another, one of the two rollers of the lower and upper rollers being leading, the other being led. Instead of this known structure, it is provided according to an essential feature of the present invention, pairs 31-35 grinding rollers which mesh without contact as can be seen in Figures 6A to 6C and 7A to 7C. Considering, for example, FIG. 6A, there is shown a pair 36 of coarse-grained grinding rollers 36a whose profile is in the form of a broken bow or a clipped head warhead. According to the particular feature of this essential arrangement, as shown in FIGS. 6A-6C and 7A-7C, which respectively illustrate the engaged position of the pair of grinding rollers 36, 37 or 38, the flutes 36a (37a or 38a) of the upper roll are never in contact with the flutes 36a (37a or 38a) of the lower roll.

The gap e at the meshing between the flutes of the upper grinding roll and the lower grinding roll being as far as possible substantially constant as is apparent from Figs. 7A to 7C.

FIGS. 6B and 7B show a pair 37 of medium-sized fluting rollers 37a which have another shape: the flutes 37a are sectional in the form of a crenel whose sides are slightly convex and slightly inclined in the direction from the head of the groove.

In Figs. 6C and 7C a third type of grinding roll is shown: the pair 38 is composed of two small groove milling rolls 38a whose section has an M-shaped outline. Between two small grooves 38a the grinding roll 38 has a W-shaped contour corresponding to a longitudinal groove (see Fig. 7C).

It will be noted that in all cases, the grinding rollers have, between their grooves 36a, 37a or 38a, a recess (a groove) of complementary shape to that of the grooves.

In order to achieve the synchronous rotation movement of the upper and lower rollers of all pairs of rollers 31 to 35 composing a scutching unit, for example the scutching unit 11 of FIG. 3, a single motor 39 realizes the setting in motion five pairs of grinding rollers 31-35 by means of a single transmission belt 39a. In addition, this transmission belt 39a constitutes even the drive means of the two belts 61 and 62 of the drive system 60 for transporting the web 100 of the flax stems.

In this way, it is understood that it ensures, for each scraping unit 11 to 15, a synchronous drive of all the grinding rollers and the gripping zone 60a for a regular and synchronous advance of the web 100 of rods flax at the same scutching unit 11 to 15.

According to a particular arrangement, in order to place the lower and upper rollers of a pair of grinding rollers in meshing, it is the lower roll which is moved upwards by means of a pneumatic jack which actuates an arm lever which makes it possible to adjust the pressurization of the jack and therefore the stress exerted on the lower roll when it is placed in the meshing position with the upper roll. Thus, in the event of a problem (blockage or other), if the control of the pneumatic cylinder is faulty or is no longer activated, the lower rollers are then in their low position, which corresponds to a safety situation avoiding, for example, injuries. by pinching between the rollers of the same pair. In order to be able to precisely adjust the spacing between each roller of a pair of upper and lower grinding rollers, an adjustable stop device associated with the assembly consisting of the pneumatic cylinder and the aforementioned lever arm is provided, for each pair of grinding rollers. From the foregoing, it is understood that the realization of meshing without contact between the upper and lower grinding rollers of the same pair avoids exerting shear forces along the flax fibers.

In addition, the actuation by pneumatic jack of the high position of the lower grinding roller of each pair of grinding rollers makes it possible to exert an adjustable and constant pressure on the linen ply 100, which makes it possible to compensate the extra thicknesses. during the advance of this sheet 100 of flax stems and this to avoid "stuffing" at a pair of grinding rollers. Also, it should be noted that the linear scrolling speed of the drive belts 61 and 62 is adjusted according to the speed linear rotation of the pitch diameter of the grooves of the grinding rollers to prevent fiber tearing or displacement of the rods in the drive belts 61 and 62.

It is also understood that the drive belts 61 and 62 being flat belts, they hold the stems of flax fibers flat, which minimizes the breaks of the fibers, and this in order to preserve the integrity of the fibers as much as possible their length.

This essential arrangement for producing the grinding rollers with non-contact meshing is advantageously combined with a gradual reduction in the size of the grooves of the grinding rollers as the flax stems progress in the scutching device. linen 10.

Three sizes of splines, such as those illustrated in FIGS. 6A to 6C and 7A to 7C or more of different sizes with intermediate sizes, either with identical shape or with different shapes, may be used. In the case of the choice of different shapes for the flutes, the larger flutes will preferentially have the shape of the flutes 36a of FIGS. 6A and 7A, the medium flutes will preferably have the shape of the flutes 37a of FIGS. 6B and 7B and the flutes of FIGS. grooves of the smallest size will preferentially have the shape of the grooves 38a of the figures

6C and 7C.

For each scutching unit it is possible to use grinding rollers having the same size of grooves or already several different sizes as one moves in longitudinal direction X, upstream downstream along the unit. of scutch considered.

Grinding rollers having different fluting sizes from one scutching unit to another may also be used or using for the last pair of grinding rolls of an upstream scutch unit a flute shape identical to that of the first pair of grinding rollers of the scutching unit placed directly downstream.

The fiber cleaning unit 40 is now described which is used according to a preferred feature of the present invention. For this purpose, each flaxseed unit 11 to 15 (see Figures 1 and 4) has a fiber cleaning unit 40 disposed downstream of the grinding unit 30.

This fiber cleaning unit 40 is intended to separate the shives from the fibers in the case of shives which have not already fallen by themselves during the shredding treatment which has previously been carried out in the grinding unit 30 of the shredder. the same scutching unit 11 to 15.

To do this, each grinding unit comprises (see FIGS. 8 and 9) according to a preferred embodiment two nozzles 42 for blowing air under pressure arranged vertically above and on either side of the gripping zone 60a. of the drive system 60, downstream of the grinding unit 30. The jet of high pressure air is sent under a pressure of between 1 and 10 bar (100,000 to 1,000,000 Pa) and preferably between 4 and 7 bars (between 400,000 and 700,000 Pa).

Alternatively or combined, this high-pressure air flow can contain high-speed percussionants such as sand, grit, seeds, pebbles, etc.

When only a jet of air under high pressure is used, preferably an air flow guide box 44 comprising (see FIGS. 8 and 9) is used, lateral panels inclined convergently downwards toward a funnel. collection 46 at which we can provide a separate suction to increase the Venturi effect.

It is also expected to collect the snails upstream of the cleaning unit 40, namely under the grinding unit 30 and under the inlet zone 20 by means of a collection hopper 70 at the bottom of which is disposed a suction system with motor and auger.

Thanks to a scutching device in accordance with the various provisions presented in the description of the figures, it results in a scutching of the linseed stems making it possible to very significantly increase the yield of the long fibers by up to 25% and more, compared with the 20% obtained according to the prior art and 30% of fibers contained in the stems of flax.

It is understood that this result makes it possible to very significantly improve the extraction efficiency of the flax fibers from the stems, and this in particular thanks to the fact that, for each grinding unit 30, the upper rollers 31b and lower 31a each pair of grinding rollers (31-35) are rotated in a synchronized manner, the splines of the upper roller 31b meshing, without contact, between two grooves of the lower roller 31a.

In addition, when, preferably, cleaning is performed on each scutching unit, after grinding, grinding is facilitated on the next scutching unit. Such cleaning is advantageously achieved by means of downward projection of a fluid and / or particles, which perform the extraction of waste liners, and in particular cleaning the rods by air blasting under pressure (and / or percussive) between each grinding step.

Claims

1. Apparatus for scutching (10) flax or any other plant whose stem contains cellulosic fibers that can be separated by scutching, comprising: - means for transporting rods in a driving direction (X) substantially perpendicular to the orientation of the rods, which comprise at least one gripping and driving assembly (60) of said rods, and - at least one grinding unit (30) comprising at least one pair of grinding rollers (31-35) superimposed grooved, characterized in that, for each grinding unit (30), the upper (31b) and lower (31a) rollers of each pair of grinding rollers (31-35) are rotated in a synchronized manner, the grooves of the upper roll (31b) meshing, without contact, between two grooves of the lower roller (31a).

2. scutching device (10) according to claim 1, characterized in that for each pair of grinding rollers (31-35), the lower roller (31a) is movable in a substantially vertical tilting movement, between a low position spaced apart from the upper roller (31b) of the corresponding pair, and a high meshing position with said upper roller (31b).

3. scutching device (10) according to claim 2, characterized in that said lower roller (31a) is made movable by an assembly formed of a pneumatic cylinder and a lever arm, said assembly being associated with a stop adjustable against which said assembly bears in said meshing position, whereby it ensures the absence of contact between the grooves of the upper roller (31b) and the grooves of the lower roller (31a).

A scutching device (10) according to any one of the preceding claims, characterized in that the splines are shaped so that when a groove of the upper roll (31b) meshes between two splines of the lower roll (31a) there is a substantially constant gap (e) between said upper roll groove (31b) and said two lower roll grooves (31a).

5. scutching device (10) according to any one of the preceding claims, characterized in that the size of the grooves of the grinding rollers (31-35) decreases from upstream to downstream along the scutching device (10).

6. scutching device (10) according to any one of the preceding claims, characterized in that it comprises at least three successive grinding units (30) and at least three sets of gripping and driving (60), each grinding unit (30) having at least three pairs of grinding rollers (31, 32, 33) arranged upstream to downstream and each grinding unit (30) being associated with one of said grasp and drive assemblies (60 ), and that said successive gripping and driving assemblies (60) have laterally offset driving directions between a gripping and driving assembly (60) and the following.

7. scutching device (10) according to claim 5 or 6, characterized in that from one grinding unit (30) to the other, each grinding unit (30) comprises grinding rollers (31-35) whose spline size is smaller than in the grinding unit (30) which precedes it, in the direction of drive (X) and upstream downstream.

A scutching device (10) as claimed in any one of the preceding claims, characterized in that said gripping and driving assembly (60) comprises a pair of endless, flat and toothed endless belts (61, 62), contacting one against the other to clamp a section of the rod to drive it during the movement of the belts (61, 62).

9. scalling device (10) according to claim 8, characterized in that, for each scutching unit, the linear speed of the toothed belts (61, 62) is adjusted according to the linear speed of rotation of the pitch diameter grooves of the grinding rollers (31-35).

10. Device for scutching (10) according to any one of the preceding claims, characterized in that the smallest splines have, in section, a form of M.

11. scalling device (10) according to any one of the preceding claims, characterized in that it further comprises, downstream of the grinding unit (30) and in an area above said gripping assembly and driving (60), a fiber cleaning unit (40) comprising means for projecting (42) downwards a fluid and / or particles towards the rods, whereby the waste is separated from the rods by the grinding unit (30) are extracted from the rods which are retained in said gripping and driving assembly (60).