EP0110745A1 - Method and apparatus for the mechanical treatment of vegetal fibres, especially for flax scutching - Google Patents

Abstract

1. Process for treating a web (1) of vegetable fibres driven in continuous manner in an average reference plane (1'), characterized in that an intensive hammering action is exerted on the web substantially perpendicularly to said average plane (1') followed by a scraping action along the fibres.

Description

The invention relates to mechanical treatments of plant fibers with a view to refining them. The invention relates more specifically to the scutching of flax, which aims to separate the textile fibers from the wood fibers contained in flax straws, which have most often been previously ripped.

Flax scutching traditionally comprises two successive operations: grinding and scutching proper, these two operations being carried out continuously on automated installations. The crushing is carried out by passing flax straws, arranged in a continuous sheet, between fluted metal cylinders: the straws spread horizontally are pinched between two belts which hold and move the sheet: the fluted cylinders, having 18 to 25 teeth depending on the manufacturers, are placed perpendicular to the direction of the belts and so that the horizontal plane in which the ply is located passes between the sets of two cylinders placed one above the other, the upper cylinder exerting pressure on the lower cylinder. Before entering between the cylinders, the sheet passes through a tie-down which has the effect of orienting the straws in the direction of advancement of the belts; thus the straws are crushed between the grooved cylinders in the direction of their length.

This method of grinding by fluted cylinders has many drawbacks. The modification of the direction of the straws by interlocking leads to heterogeneous grinding, since the straws are present between the cylinders in the longitudinal direction over part of their length, but also in the transverse direction over another part. Furthermore, the straws are most often between the cylinders in the form of irregular bundles, and it is understandable that the action of the cylinders, between which a constant pressure is exerted, being a function of the quantity of straw, the presence of irregular bundles leads to a new heterogeneity of grinding. These disadvantages are perfectly illustrated by the wear of the grooved cylinders, which one can note that it is very irregular and by the same amplifies the preceding defects.

The actual scutching is carried out after grinding on the linen tablecloth, one end of which is pinched between two belts which hold and move the tablecloth. Blades, called knives, fixed to the periphery of two rotating drums and turning in opposite directions, beat the tablecloth and eliminate the woody part of the flax straws. The actual scutching operation must compensate for irregularities due to prior grinding.

However, a new process for treating flax straw has been found in order to separate textile fibers from wood fibers, the technical result of which is akin to scutching. This process allows in a single operation to carry out the grinding under improved conditions of regularity and all or part of the scouring proper. For the rest of the description, we will use the generic term scutching to define the technical result thus obtained. The scouring process in a single operation according to the invention eliminates the drawbacks observed in the conventional process implementing the two grinding and scouring operations proper.

The method according to the invention for treating a sheet of plant fibers continuously entrained in a mean reference plane, is characterized in that an intensive hammering action is exerted on the sheet substantially perpendicular to said mean plane, followed scraping action along the fibers.

The intensive hammering according to the invention involves repeated energetic shocks, and is perfectly distinguished from the threshing obtained by the knives of the rotary drums mentioned above, or by the blades of the rotor of document FR-A-1 213 423. In these known devices, the beating members strike the sheet practically tangentially, and are rather intended to put the latter in vibration. In contrast, intensive hammering perpendicular to the mean plane of the ply (the ply can, moreover, leave this mean plane under the action of said hammering) aims at a grinding effect of the fibers, supplemented by the subsequent scraping.

Advantageously, the ply moves between a fixed block and a mobile block, the latter exerting the intensive hammering action.

Advantageously, the movable block also exerts the scraping action.

Advantageously, the ply is hammered and scraped by common members carried on the movable block, which is driven in rotation.

The invention also relates to equipment intended to implement the aforementioned method. This material comprises, in addition to a means for continuously driving the ply of fibers in a mean reference plane, means for intensive hammering of the ply in a direction substantially perpendicular to its mean plane, and means for scraping the fibers along of these.

Advantageously, the intensive hammering and scraping means are constituted by common members carried by a movable block.

Advantageously, the movable block is driven in a rotational movement.

Advantageously, the rotary block comprises at the periphery one or more hammers, the block being arranged with respect to the ply so that the hammers arrive substantially perpendicular to the mean plane of the ply to strike it.

Advantageously, the hammers are mounted movable on axes carried by the rotary block and parallel to its axis of rotation.

When the movable block is rotated, the hammers, by centrifugal force, are oriented towards the outside of the block. Each hammer strikes the straw sheet which moves between a fixed block and the movable block. This arrangement of hammers makes it possible to allow excess thicknesses, or even foreign bodies such as stones. One can conceive of other types of retraction of hammers (for example, fixed hammers with radial elasticity).

Advantageously, the movable block is placed in an enclosure of approximately cylindrical shape, so that each hammer, after having struck the sheet of straws, slides on the surface of these and pursues a progressive scouring action. An opening is provided at the bottom of this enclosure for the recovery of scutching by-products.

Advantageously, the continuous sheet of flax straw, held between two conveyor belts, falls vertically (thus defining the mean plane of the sheet) and moves between the two blocks; the fixed block is a metal rod in contact with the straw, at an angle to it, so that, in the direction of movement of the sheet, the first end is at the lowest level of the straw and the second end is at the level of the lower part of the conveyor belt.

Advantageously, the movable block rotates around an axis of rotation substantially contained in the mean plane of the ply, and oblique with respect to the direction of advance thereof.

A scutching assembly according to the invention comprises a succession of several materials composed of fixed blocks and mobile blocks, between which is a known mechanism for turning straws. This set allows you to dye the feet of the flax straws and then the heads or vice versa.

The invention will be better understood using an embodiment described below and illustrated by Figures 1, 1a, 2, 3 and 4, Figure 1 being a side view of a scutching assembly , Figure 1a being a top view of the same scutching assembly, Figures 2 and 3 two cross sections of the scutching material respectively at the planes AA 'and BB', line 4 showing an alternative embodiment of the figure 3.

The flax straws 1 are formed in the form of a continuous ply, pinched approximately a third of its length between two belts, one male 2, the other female 3. The belts are driven in a continuous movement of the order of 40 meters per minute, causing the displacement of the layer of straws through the scutching set. This assembly is constituted by the succession of two scutching installations 4 and 4 'acting on the straw feet, a known mechanism 5 for turning straws and two scutching installations 6 and 6' acting on the straw heads, the same collecting device 7 recovering all of the by-products at the bottom of the various scutching installations.

Each scutching installation comprises a fixed block 8, which is a rigid metal rod, mounted obliquely to the sheet of flax straws, in contact with the latter, the end 8a of this rod being at the lowest level of the straw to be dyed, the end 8b being at the height of the lower part of the conveyor belt. For straws whose height to be scuffed h is of the order of 800 mm, the length of the metal rod 8 is 1500 mm. Each scutching installation also comprises a movable block 9, rotatable about an axis 10 parallel to the direction of the fixed block 8, this axis 10 being substantially in the vertical mean plane 1 'of the ply; said movable block comprises a set of six hammers 11 arranged symmetrically and mounted free around their axis 12, this axis also being parallel to the direction of the fixed block 8: each of these hammers is a metallic body, asymmetrical (fig. 2 and 3 ) or symmetrical (fig. 4), having a rounded end 13. During the rotation by the drive of a motor not shown, of the movable block 9, the hammers are oriented under the action of centrifugal force so that the heaviest part is at the periphery and that the end 13 strikes the flax straws at 14, along the line where they are located between the rod 8 and the movable block. Each of the six hammers described above can itself be broken down into a number of hammers aligned individually free around the same axis, of reduced length, of the order of 50 mm. The weight of each hammer is 200 grams, the rotating block rotates 600 revolutions per minute.

Thanks to the location of the axis 10, the hammers arrive substantially perpendicular to the mean plane l ′ of the ply and exert on it a hammering that is all the more intensive as the ply is kept near the impact by the bar. 8. This results in a shearing effect favorable to the desired result.

It should be observed that the advantageous results of the treatment of the invention are linked to the localized impact effect imparted by each hammer. An excessive increase in the number of hammers leads to poorer results, probably because the action of many hammers then approaches the continuous crushing obtained in conventional grinding.

The fixed rod 8 is extended by a curved bearing surface 15 which has a profile calculated so that the rounded end 13 of the hammer 11, after striking the flax straws 1 at 14, continues its race by scraping said straws which are theoretically pressed against the internal wall of this curved surface 15 (fig. 3). Said surface therefore has an approximately cylindrical profile whose axis of symmetry is the axis of rotation of the movable block 9.

Although certain fibers can behave as indicated above and stick to the wall 15, the stroboscopic observation of materials in operation has shown that the flax rod, once it has been struck by the hammer 13, has rather tendency to come to marry the contour of hammers under the effect of a complex aerodynamic phenomenon. Also, as shown in Figure 4, there are provided anti-barbs 16 to prevent the rods from wrapping around the axes 12. This aerodynamic phenomenon is positive because it results in a much more energetic scraping and therefore a more thorough scutching.

At the lower part of the movable block 9 and in the extension of the curved surface 15 are evacuated the scour byproducts: shives, dust which are thus eliminated.

So each flax straw, moving in the direction of the arrow S and entering the scutching installation 4, first undergoes the action of the hammers at the lowest level of the feet. A hammer striking the straw to the right of the end 8 a of the fixed block 8; the same straw is then struck by another hammer, while the conveyor belt has itself moved, the point of impact of this second hammer not being therefore identical to the first and moving along the rigid and oblique rod 8. Consequently, when the same straw has passed through the entire scutching installation 4, its entire available length below the pinching point of the belts which has been struck by the succession of individual hammers.

This scutching action is adjustable at will, for the same speed of movement of the ply, as a function of the speed of rotation of the movable block 9, and also of the choice of shape, weight and number of individual hammers. Furthermore, for a given adjustment of the machine, the scouring action is uniform over the entire length of the straws.

To obtain sufficient removal of the wood fibers, it is more often necessary to carry out several operations of the type described above and therefore to have several scouring installations in series. After the scutching of the feet of the flax straws, the tablecloth is turned over according to a technique traditional in the linen trade, in an appropriate device 5. Finally the scutching operation continues at the head of the flax straws in one or more scutching installations.

FIG. 1a illustrates the example of a scutching assembly successively comprising two scutching installations 4 and 4 ′ for scutching the feet of flax straws, the turning device 5 and two scutching installations 6 and 6 ′ for the scutching of the heads of flax straws. In installations 4 'and 6', the fixed 8 and mobile 9 blocks are arranged relative to each other, unlike their arrangement in installations 4 and 6; in this way, the impact of the hammers 13 of installations 4 and 6 on the straw layer occurs on one of the faces of the sheet, while it occurs on the other face in installations 4 'and 6'. This particular arrangement makes it possible to increase the regularity of scutching.

It should also be noted, and this is an additional advantage of this form of the invention, that the evacuation of scouring by-products by the collector placed at the bottom of each scouring installation requires very little d energy, taking into account the fan effect caused by the mobile block in rotation: the shives and dust are projected towards said collector.

The example which has just been described and which is the best embodiment known to date is not restrictive of the other variants of the invention, such as that in which the movable block is driven not by a rotary movement but alternative.

As said at the beginning of this memoir, the invention does not only concern the treatment of flax, even if it provides in the case of the latter, particular advantages (the fact, for example, that the first machine for treating the line can remove flaxseeds, traditionally carried out on a stand-alone machine before scutching). The invention also applies to the treatment of hemp, etc.

Claims (11)

1. Method for treating a sheet (1) of vegetable fibers driven continuously in a reference mean plane (1 ′), characterized in that an intensive hammering action is exerted on the tablecloth substantially perpendicular to said mean plane (1 ') followed by a scraping action along the fibers. 2. Method according to claim 1, characterized in that the ply moves between a fixed block (8) and a movable block (9), the latter exerting the action of intensive hammering. 3. Method according to claim 2, characterized in that the movable block (9) also exerts the scraping action. 4. Method according to any one of claims 2 or 3, characterized in that the ply is hammered and scraped by common members (11) carried on the movable block (9), which is rotated. 5. Treatment equipment for implementing the method of any one of claims 1 to 4, comprising means (2,3) for continuously driving the fiber web in a reference mean plane (1 ′) , characterized in that it comprises means (11) of intensive hammering of the ply (1) in a direction substantially perpendicular to its mean plane (1 '), and means (11) for scraping the fibers along those -this. 6. Equipment according to claim 5, characterized in that the intensive hammering and scraping means are constituted by common members (11) carried by a movable block (9). 7. Equipment according to claim 6, characterized in that the movable block (9) is driven in a rotational movement. 8. Equipment according to claim 7, characterized in that the rotary block (9) comprises on the periphery one or more hammers (11), the block (9) being disposed relative to the ply (1) so that the hammers ( 11) arrive substantially perpendicular to the mean plane (1 ') of the sheet to strike it. 9. Equipment according to claim 8, characterized in that the hammers (11) are mounted movable on axes (12) carried by the rotary block (9) and parallel to its axis of rotation (10). 10. Equipment according to any one of claims 7 to 9, characterized in that the movable block (9) rotates around an axis of rotation (10) substantially contained in the mean plane (1 ') of the sheet, and oblique to the direction of advancement thereof. 11. Equipment according to any one of claims 6 to 10, characterized in that it comprises a fixed support means (15) cooperating with the movable block (9) for scraping the fibers.

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