CH348973A

CH348973A - Humidifying device for printing machines

Info

Publication number: CH348973A
Authority: CH
Inventors: Charles Clare Maurice
Original assignee: Charles Clare Maurice
Priority date: 1958-01-21
Filing date: 1959-01-15
Publication date: 1960-09-30

Description

Dispositif d'humidification pour machirres ä imprimer 0n sait que dans, les machirres, ä imprimer du type Offset 1'impression est obtenue par report ä partir dune plaque portee par un rouleau et qui comporte des surfaces imprimantes, sur lesquelles se fixe 1'encre, mais qui repoussent Feau et des surfaces non imprimantes, repoussant Fencre mais presentant un caractere hydrophile. En fonationnement, une certaine quantite d'eau doit etre fournie ä la plaque. Humidification device for printing jaws It is known that in offset type printing jaws, printing is obtained by transfer from a plate carried by a roller and which comprises printing surfaces, on which the ink is fixed. , but repel water and non-printing surfaces, repelling ink but exhibiting a hydrophilic character. In operation, a certain amount of water must be supplied to the plate.

Le dispositif humidificateur 1e plus couramment utilise comporte un rouleau molletonne oscillant entre, dune part, um rouleau rotatif dorrt la partie inferieure trempe dann un bac humidificateur et, d'autre part, um jeu de rouleaux associe ä la plaque. Ce jeu de rouleaux comprend generalement deux rouleaux molletonnes tangents ä la plaque et un rou- leau appele table ä mouiller , en contact avec ces deux rouleaux et que vient toucher p'eriodique- ment 1e rouleau oscillant. The most commonly used humidifier device comprises a fleece roller oscillating between, on the one hand, a rotating roller which holds the lower part soaked in a humidifier tank and, on the other hand, a set of rollers associated with the plate. This set of rollers generally comprises two fleece rollers tangent to the plate and a roller called the wetting table, in contact with these two rollers and which the oscillating roller periodically touches.

Ce dispositif humidificateur classique presente de nombreux inconvenients et, en particulier, il est com- pliqu6 et ne pennet pas de regler commodement Fin- tensit6 de 1'humidification 1e long de la plaque. 0n sait que, en effet, il faut fournir moins d'eau aux parties non imprimantes qu'aux parties imprimantes. This conventional humidifying device has many drawbacks and, in particular, it is complicated and does not allow convenient adjustment of the intensity of the humidification along the plate. It is known that, in fact, less water must be supplied to the non-printing parts than to the printing parts.

La presente invention a pour objet un dispositif d'humidificateur pour machirres, ä imprimer du type Offset qui est caracterise par une brosse rotative, des moyens pour impregner d'eau les soies de cette brosse, ainsi que par des moyens destines ä provo- quer une flexion progressive des soies de la brosse puis un redressement brutal de ces dernieres qui pro- jettent alors en fines gouttelettes 1e liquide dorrt elles ont ete impregnees. The subject of the present invention is a humidifier device for jaws, to be printed of the Offset type which is characterized by a rotating brush, means for impregnating the bristles of this brush with water, as well as means intended to cause a gradual bending of the bristles of the brush then a sudden straightening of the latter which then project fine droplets of the liquid in which they have been impregnated.

La projection peut se faire directement sur la plaque ou encore sur un rouleau mouilleur ou sur une table ä mouiller. 0n peut meine la faire sur un rouleau intermediaire, de preference molletonne, en contact avec la table ä mouiller. The projection can be done directly on the plate or on a dampening roller or on a dampening table. It can even be done on an intermediate roller, preferably fleece, in contact with the table to be wetted.

L'intensite de 1'humidification peut eire tres com- mod6ment reglee de plusieurs manieres, par exemple par variation de la vitesse de rotation de la brosse, par action sur la flexion que subissent les soies de celle-ci ou encore par modification de 1'espace offert aux gouttelettes pour s'echapper. En particulier, il est possible de modifier cet espace differemment dans 1e sens de la longueur de la plaque afin de mieux adapter RTI ID="0001.0272" WI="4" HE="4" LX="1205" LY="1687"> les quantites deau projetees ä Faire des sur- faces imprimantes et non imprimantes. The intensity of the humidification can be very conveniently regulated in several ways, for example by varying the speed of rotation of the brush, by acting on the flexion which the bristles of the latter undergo or by modifying the speed of rotation of the brush. space for droplets to escape. In particular, it is possible to modify this space differently in the first direction of the length of the plate in order to better adapt RTI ID="0001.0272" WI="4" HE="4" LX="1205" LY="1687" > the quantities of water projected to make printing and non-printing surfaces.

Le dessin represente, ä titre d'exemple, une forme d'execution de Fobjet de 1'invention. The drawing represents, by way of example, one embodiment of the object of the invention.

La fig. 1 est une vue schematique en coupe dun dispositif d'humidification. fig. 1 is a schematic sectional view of a humidification device.

La fig. 2 est une vue en coupe partielle selon II-II de la fig. 1 et ä plus grande echelle, montrant la constitution et 1e montage de la brosse. fig. 2 is a partial sectional view along II-II of FIG. 1 and on a larger scale, showing the construction and mounting of the brush.

La fig. 3 est une vue partielle, en el6vation et avec coupe selon III-III de la fig. 4, dune variante du dispositif d'humidification. fig. 3 is a partial view, in el6vation and with section along III-III of FIG. 4, of a variant of the humidification device.

La fig. 4 est une coupe selon IV-IV de la fig. 3. Dans 1e mode de realisation represente sur les fig. 1 et 2, 1e disposstif d'humidification comprend essentiellement un bac 1 de preference en matiere inoxydable. Ce bac peut etre ä fond plat ou curvili- gne. Il est, en tont cas, de forme allongee et de lon- gueur un peu plus grande que celle du cylindre 2 qui doit recevoir 1'eau. 11 est monte sur 1e bäti 3 de Ja machine parallelement ä Faxe du cyhndre 2 et 1e plus pres possible de co dernier sans toutefois 1e tou- cher. Avantageusement, un rebord la est pr6vu du cste du bac 1e plus proche du cylindre afin de re- cueillir les gouttelettes d'eau qui pourraient tomber du cylindre et de les ramener dans 1e bac. fig. 4 is a section along IV-IV of FIG. 3. In the first embodiment represented in FIGS. 1 and 2, the first humidification device essentially comprises a tray 1, preferably made of stainless steel. This tank can be flat-bottomed or curved. It is, in all cases, of elongated shape and of a length a little greater than that of the cylinder 2 which is to receive the water. It is mounted on the frame 3 of the machine parallel to the axis of the cylinder 2 and as close as possible to the latter without however touching it. Advantageously, a rim 1a is provided on the side of the tray 1e closest to the cylinder in order to collect the droplets of water which could fall from the cylinder and to bring them back into the tray.

Le bac 1 est uruni d'un trop-plein 4 reue ä une conduite 5 d'evacuation. 11 est alimente ä partir d'un reservoir 6 en charge, dont la tubulure de sortie 7 est munie d'un robinet B. Cette tubulure est raccor- dee ä une tubulure 9 que comporte 1e bac, la tubu- lure 9 aboutissant ä 1'interieur de ce bac ä un niveau ldgerement inferieur ä celui du trop-plein 4. Le r6ser- voir 6 comporte une ouverture 10 munie d'un obtu- rateur dtanche 11. The tank 1 is connected from an overflow 4 received to a pipe 5 for evacuation. 11 is fed from a reservoir 6 under load, the outlet pipe 7 of which is provided with a tap B. This pipe is connected to a pipe 9 which comprises the first tank, the pipe 9 leading to inside this tank at a level slightly lower than that of the overflow 4. The tank 6 comprises an opening 10 provided with a sealed shutter 11.

Pour remplir 1e reservoir, an ferme 1e robinet 8 et Fon enleve Fobturateur 11. Si 1'operateur oubliait de fermer 1e robinet, la presence du trop-plein empe- cherait tont debordement intempestif. To fill the tank, one closes the valve 8 and removes the stopper 11. If the operator forgets to close the valve, the presence of the overflow would prevent any untimely overflow.

En fonctionnement, Fobturateur bouche Forifice 10 et Je robinet 8 est ouvert. Le niveau du liquide 12 s'etablit ä la hauteur de Pouverture de la tubulure 9. Si 1e niveau du liquide dans 1e bac s'abaisse suffi- samment pour que la sortie de la tubulure 9 sofft de- couverte, de 1'eau s'ecoule du reservoir pour ramener 1e niveau ä sa valeur primitive. In operation, the shutter blocks the orifice 10 and the valve 8 is open. The level of the liquid 12 settles at the height of the opening of the tubing 9. If the level of the liquid in the tank drops sufficiently so that the outlet of the tubing 9 is uncovered, water will come out. flow from the reservoir to bring the level back to its original value.

Ce mode de reglage du niveau d'eau est bien connu. 11 est utilise en particulier dann certains types d'abreuvoirs. Tout autre dispositif d'alimentation ä niveau constant pourrait etre utilis6. This method of adjusting the water level is well known. 11 is used in particular dann certain types of drinkers. Any other constant level feeder could be used.

A Finterieur du bac 1 est prevue une brosse rota- tive 13 dopt la longueur est sensiblement egale ä celle du cylindre 2 ä humidifier. Inside tank 1 there is a rotating brush 13 whose length is substantially equal to that of cylinder 2 to be moistened.

La brosse 13 peut eire en üne Beule piece ou, de preference, en plusieurs trongons 13a enfiles sur un arbre 14. Ces trongons peuvent etre maintenus en place par serrage en bout, au moyen, par exemple, d'ecrous 15 (fig. 2) vissds sur des portees filetees 14a de Farbre. Ort peut au besoin prevoir une clavette 16 ou autre moyen destine ä les empecher de tourner par rapport ä Farbre (fig. 1). The brush 13 can be made in a single piece or, preferably, in several sections 13a threaded onto a shaft 14. These sections can be held in place by tightening at the end, by means, for example, of nuts 15 (fig. 2 ) screwed on threaded bearing surfaces 14a of the shaft. Ort can if necessary provide a key 16 or other means intended to prevent them from rotating relative to the shaft (fig. 1).

L'arbre 14 est port6 par des paliers 17 eux- memes fixes au bäti 3 de la machine. The shaft 14 is carried by bearings 17 themselves fixed to the frame 3 of the machine.

De preference, ces paliers sont aisement demon- tables et 1'arbre est uruni ä chacune de ses extr6mi- tes d'organes d'entrainement identiques, par exemple des pignons 18 susceptibles de cooperer avec un pignon d'entrainement 19 ä vitesse variable porte par 1e bäti 3. Preferably, these bearings are easily removable and the shaft is fitted at each of its ends with identical drive members, for example pinions 18 capable of cooperating with a variable-speed drive pinion 19 carrying by 1st frame 3.

0n peut ainsi, sans difficulte, retourner la brosse bout pour bout de temps ä. autre, ce qui permet d'evi- ter que les soies de la brosse ne se couchent ä l'usage. 0n can thus, without difficulty, return the brush end for end of time ä. another, thereby preventing the bristles of the brush from becoming bent during use.

Si cela est n6cessaire, des ouvertures 1b sont pre- vues dans 1e bac :1 pour laisser passer les extremites de Farbre de la brosse. If necessary, openings 1b are provided in tray 1 to pass the ends of the brush shaft.

Les soies 20 de la brosse rotative 13 peuvent etre en matiere quelconque, vegetale, animale, minerale ou synth6tique. Il suffit que ladite matiere sofft douee d'elasticite. 0n peut, par exemple, utiliser des fils ou rabans en metal tel que de 1'acier ou encore en matiere synthetique comme les produits de marques Nylon ou 1e Rylsan . The bristles 20 of the rotary brush 13 can be made of any material, vegetable, animal, mineral or synthetic. It suffices that said material be endowed with elasticity. It is possible, for example, to use wires or strips made of metal such as steel or else of synthetic material such as products of the Nylon or Rylsan brands.

Pour assurer la projection de gouttelettes d'eau sur 1e cylindre 2, an associe ä la brosse 13 un organe ddflecteur 21 dispose parallelement ä Faxe de la brosse et qui peut etre amene sur la trajectoire d6crite par les soies de cette derniere. To ensure the projection of water droplets on the first cylinder 2, an associates with the brush 13 a deflector member 21 arranged parallel to the face of the brush and which can be brought on the trajectory described by the bristles of the latter.

Lorsque ces soies approchent de 1'organe 21, elles se couchent et f1echissent progressivement puis, lorsqu'elles ont franchi ledit organe, elles se redres- sent brusquement gräce ä leur elasticite en projetant 1'eau dont elles sont imbibees sous forme de goutte- lettes Jans la direction du cylindre 2. When these bristles approach the organ 21, they lie down and sag progressively then, when they have crossed said organ, they straighten up suddenly thanks to their elasticity by projecting the water with which they are soaked in the form of droplets. Jans letters the direction of cylinder 2.

L'organe 21 peut etre realise et dispose de diver ses manieres. The member 21 can be made and available in various ways.

Sur la fig. 1, il est constitue par une reglette 21a portee par un axe 21b monte dans les parois lat6ra- les extremes du bac 1. 0n peut faire tourner Faxe 21b pour faire penetrer la reglette plus ou moins Jans la trajectoire des, soies de la brosse ou pour Fescamoter, la projection etant d'autant plus intense que la reglette penetre plus dans la trajectoire. In fig. 1, it is constituted by a strip 21a carried by an axis 21b mounted in the extreme side walls of the tray 1. Faxe 21b can be rotated to cause the strip to penetrate more or less in the path of the bristles of the brush or for Escamoter, the projection being all the more intense as the ruler penetrates more into the trajectory.

D'autres moyens peuvent eire prevus pour regler Fintensite de 1'humidification. Other means may be provided to adjust the intensity of the humidification.

Dans 1'exemple represente sur les fig. 1 et 2, 1e bac 1 est uruni ä 1'arriere d'un capot 22, par exem- ple de forme cylindrique, et qui peut eire fixe audit bac par simple emboitement ou de toute autre maniere convenable. In the example represented in FIGS. 1 and 2, the first container 1 is uruni at the rear of a cover 22, for example of cylindrical shape, and which can be fixed to said container by simple interlocking or in any other suitable way.

A 1'avant du capot 22 est pr6vu un 6cran mobile 23 comportant une paroi cylindrique 23a et des sec- teurs lateraux 23b artieules sur des tourillons 24 au capot 22. Un dispositif de r6glage 25, par exemple ä vis, permet de modifier la position angulaire de 1'6cran 23 pour definir une ouverture de sortie varia ble 26 ä 1'avant du bac. At the front of the cowl 22 is provided a mobile screen 23 comprising a cylindrical wall 23a and lateral sectors 23b hinged on pins 24 to the cowl 22. An adjustment device 25, for example a screw, makes it possible to modify the position angle of 1'6cran 23 to define a varia ble outlet opening 26 at the front of the tray.

En outre, Feoran 23 comporte des moyens qui permettent d'obturer partiellement certaines portions de 1'ouverture 26 dans 1e sens axial, en fonction des exigences de chaque cas particulier. Furthermore, Feoran 23 comprises means which allow certain portions of the opening 26 to be partially closed in the axial direction, depending on the requirements of each particular case.

Dans 1'exemple represente, ces moyens compor- tent des glissieres 27 disposees longitudinalement ä Favant de 1'ecran 23, ainsi que des volets 28 qui peu- vent etre inseres entre l'6cran 23 et les glissieres 27. Ces volets 28 sont de preference constitues par des plaquettes en matiere elastique, planes ou legerement incurvees, et qui se trouvent maintenues en place dans les glissieres du fait de leer elasticite. In the example represented, these means comprise slides 27 arranged longitudinally in front of the screen 23, as well as flaps 28 which can be inserted between the screen 23 and the slides 27. These flaps 28 are of preferably constituted by plates of elastic material, flat or slightly curved, and which are held in place in the slides due to leer elasticity.

Ort peut prevoir des volets 28 de dimensions dif ferentes. et les utiliser seuls ou simultanement aux endroits voulus selon 1e motif que comporte la plaque. Ort can provide flaps 28 of different sizes. and use them alone or simultaneously in the desired places according to the pattern that the plate has.

0n reconnait sur les fig. 3 et 4 les principaux organes du dispositif d6crit en regard des fig. 1 et 2, ä savoir un bac 1 de forme allongee monte paralle- lement au cylindre 2 ä hunüdifier sur 1e bäti 3 de la machine. 0n recognizes in figs. 3 and 4 the main organs of the device described with reference to FIGS. 1 and 2, namely a tray 1 of elongated shape mounted parallel to the cylinder 2 to be humidified on the frame 3 of the machine.

Ce bac est uruni d'un trop-plein 4 et alimente, ä niveau constant, par 1'interm6diaire dune tubu- lure 9. La brosse 13, cal6e Sur 1'arbre 14, peut etre mise en rotation dans 1e sens de la fleche f (fig. 4). This tray is uruni with an overflow 4 and fed, at a constant level, via a pipe 9. The brush 13, wedged on the shaft 14, can be rotated in the direction of the arrow. f (Fig. 4).

Les soies 20 de la brosse 13 sont reparties en couronnes 20a ; dann 1e pr6sent exemple, chaque couronne comporte un certain nombre de loquets 20b regulierement espacds 1e long de la piriph6rie de la brosse. The bristles 20 of the brush 13 are distributed in crowns 20a; In the present example, each ring has a number of regularly spaced latches 20b along the periph6rie of the brush.

Les couronnes 20a, equidistantes, sont d6ca16es p6ripheriquement de fagon que les divers loquets soient disposes selon des hdlices paralleles et ä grands pas. The crowns 20a, equidistant, are staggered peripherally so that the various latches are arranged according to parallel helices and with large pitches.

L'organe d6flecteur 21, dispos6 parallelement ä faxe de la brosse, est constitud par une barre md- plate, par exemple carree, mont6e dans les parois laterales du bar, 1 par 1'interm6diaire de tourillons excentr6s 30, ce qui permet d'amener ledit organe Sur la trajectoire d6crite par les loquets 20b lorsque la brosse tourne et de 1e ramener dann une position de repos hors de port6e des soies de la brosse. The deflector member 21, arranged parallel to the brush base, is constituted by a flat bar, for example square, mounted in the side walls of the bar, 1 by means of eccentric trunnions 30, which makes it possible to bring said member onto the trajectory described by the latches 20b when the brush rotates and bring it back to a rest position out of reach of the bristles of the brush.

Dans sa portion destinee ä etre amen6e Sur 1e trajet des loquets 20b, 1'organe 21 pr6sente, en regard de chaque couronne 20a, une entaille 31 dorrt les parois laterales convergent dans 1e sens du d6place- ment des soies. In its portion intended to be brought along the path of the latches 20b, the member 21 has, facing each crown 20a, a notch 31 where the side walls converge in the direction of movement of the bristles.

Dans 1e present exemple, la section des entailles 31 est triangulaire. Elle pourrait eire de toute autre forme, par exemple semi-circulaire. Les entailles 31 sont pratiqu6es obliquement dans la face considdr6e de 1'organe 21, afin que la section de 1'entaille dimi- nue au fur et ä mesure que les loquets 20b s'y ddplacent. In the present example, the section of the notches 31 is triangular. It could be of any other shape, for example semi-circular. The notches 31 are made obliquely in the considered face of the member 21, so that the section of the notch decreases as the latches 20b move therein.

Le fonctionnement du dispositif qui vient d'etre decrit est analogue ä celui du mode de r6alisation precedent. The operation of the device which has just been described is analogous to that of the preceding embodiment.

Lorsque la brosse est mise en rotation dans 1e sens de la fleche f, ses loquets viennent plonger dans la masse 12 d'eau ou autre liquide que contient 1e bac et se chargent d'eau. When the brush is rotated in the first direction of the arrow f, its latches are immersed in the mass 12 of water or other liquid contained in the first tank and are loaded with water.

Si 1'organe d6flecteur 21 occupe la position representee Sur la fig. 4, les loquets se trouvent pro- gressivement fldchis dann les entailles 31 et, lorsque les soies se redressent brusquement en quittant les entailles, elles projettent les gouttelettes d'eau dorrt elles dtaient chargdes, Sur la surface ä humecter, selon un faisceau 32 (fig. 4). If the deflector 21 occupies the position shown in FIG. 4, the latches are gradually flexed in the notches 31 and, when the bristles straighten abruptly on leaving the notches, they project the droplets of water from which they were charged, On the surface to be moistened, in a beam 32 ( Fig. 4).

Du fait de la pr6sence des. entailles ä largeur d6croissante, les extrem,it6s des loquets se trouvent resserr6es ä chaque passage et Fon dvite ainsi qu'un 6panouissement des loquets ne diminue ä la longue la capacite d'absorption d'eau de la brosse. Due to the presence of. notches with decreasing width, the extrem, it6s of the latches are tightened with each passage and Fon thus avoids that a 6épanouilment of the latches does not decrease in the long run the water absorption capacity of the brush.

Comme dann 1'exemple pr6c6dent, il est possible de r6gler 1'intensit6 de 1'humidification, tout 1e long de la brosse 13, gräce ä des obstacles mobiles dis- pos6s devant 1'organe dUlecteur 21. As in the previous example, it is possible to adjust the intensity of the humidification, all along the brush 13, thanks to movable obstacles arranged in front of the reader member 21.

A cet effet, une barre 33 est montde entreRTI ID="0003.0275" WI="4" HE="4" LX="996" LY="2503"> les flasques terminaux du bac 1, parallelement ä la brosse et au-dessus de celle-ci. La barre 33 est perc6e d'al6sages taraudU 34, dans lesquels sont engag & s des tiges filetfies 35 terminfies, dune Part, par un bouton molet6 36 et, d'autre part, par un Corps cylindrique 37. For this purpose, a bar 33 is mounted between RTI ID="0003.0275" WI="4" HE="4" LX="996" LY="2503"> the terminal flanges of tray 1, parallel to the brush and above it. The bar 33 is pierced with tapped bores 34, in which are engaged threaded rods 35 terminated, on the one hand, by a knurled knob 36 and, on the other hand, by a cylindrical body 37.

Dans 1e pr6sent exemple, ce Corps cylindrique possede un diamUre correspondant sensiblement ä la largeur occup6e par trois couronnes de loquets. Les Corps 37 sont disposds tout 1e long de la brosse et sont pratiquement tangents. En mancruvrant les bou- tons 36 an peut occulter les portions voulues du faisceau de pulv6risation. In the present example, this cylindrical body has a diameter corresponding substantially to the width occupied by three crowns of latches. Bodies 37 run the length of the brush and are substantially tangent. By turning the knobs 36 an can obscure desired portions of the spray beam.

La barre 33 sert avantageusement encore ä la fixation d'un volet <B>38,</B> par exemple en matiere plas- tique transparente permettant de clore la partie sup6- rieure du bac. Le volet 38 est fix6 ä la baue 33 gräce ä des vis 39. The bar 33 is also advantageously used for fixing a flap <B>38,</B> for example made of transparent plastic material making it possible to close off the upper part of the container. The flap 38 is fixed to the beam 33 by means of screws 39.

Claims

CLAIM Humidifying device for a printing machine of the offset type, characterized by a rotating brush, means for impregnating the bristles of this brush with water, as well as by means intended to cause a progressive bending of the bristles of the brush then a sudden straightening of the latter which then project, in fine droplets, the liquid coated them, have been impregnated. 1. Device according to claim, characterized in that the brush bathes by its lower part in a water tank arranged parallel to the cylinder and close to the latter and provided with a constant level feed device. .

2. Device according to claim, characterized in that the brush and the various accessories necessary for its assembly are symmetrical in order to allow easy reversal of the brush and thus prevent the bristles of the latter from lying down during use. .

3. Device according to claim, characterized in that the brush is associated with a floater member parallel to the axis of the brush and capable of being brought into the path of the bristles of the latter.

4. Device according to sub-claim 3, carao- t6ris6 in that the deflector organ is constituted by a rod, mounted on an eccentric axis and which 1'on can be rotated for the purpose of adjusting the spray of water.

5. Device according to sub-claim 3, characterized in that the bristles of the brush are arranged in peripheral crowns and, opposite each crown, the deflector member comprises a notch of decreasing width in the direction of movement of the brushes. bristles, so that they are tight ID="0003.0545" WI="13" HE="4" LX="1689" LY="2546"> deflector.

6. Device according to sub-claim 5, charac terized in that the deflecting member presents the bristles of the brush with a flat face in which the notches are made obliquely so that their depth decreases in the direction of movement of the bristles.

7. Device according to sub-claim 1, charac terized in that the water tank is provided, at its rear part, with a cover comprising a movable screen allowing adjustment of the width of the gap through which escapes projected water.

8. Device according to claim, characterized by obstacles. capable of intercepting the spray beam and which can be moved individually.

9. Device according to sub-claims 7 and 8, characterized in that the screen. mobile is arranged to receive removable flaps intended to mask a certain portion of the projection interval.

10. Device according to sub-claim 9, characterized in that the movable screen has a curved outer face on which slides are provided, and the removable flaps consist of flexible plates which can be inserted into these slides.

11. Device according to sub-claim 8, characterized in that the obstacles consist of cylindrical bodies mounted, via threaded rods, on a bar parallel to the brush.