Patent Publication Number: US-6212737-B1

Title: Plant for processing fibers

Description:
The present invention concerns blowroom plants for opening and cleaning fibre material as well as corresponding methods and apparatus. The invention is applicable particularly, but not exclusively, in processing cotton fibres or fibres of similar staple length. 
     BACKGROUND OF THE INVENTION 
     STATE OF THE ART 
     It is the general goal of fibre processing in the blowroom to enhance production and the degree of cleaning and to process the material gently minimising losses of good fibre content. The problems involved have been mentioned often in the (patent) literature, see e.g. DE-C-3490510 (U.S. Pat. No. 4,512,060). 
     In principle, the fibre material is cleaned in the blowroom in at least one “cleaner” before being transferred to carding. As to the lay-out of cleaners, no consistent agreement prevails. There are tendencies, however, to unite the cleaning processes “in one single machine” as far as possible—see e.g. AT-C-231054, DE-A2939861 (U.S. Pat. No. 4,345,356) and DE-A-4039773 (U.S. Pat. No. 5,146,652). 
     A cleaning line delivers fibre material to a predetermined number (e.g. twelve) cards. The line must be laid out in such a manner that the maximum throughput demand by the cards associated thereto can be satisfied. As the processing capacity of the individual card increases, the processing capacity of the cleaning line is to be adapted accordingly (i.e. a reduction in the number of cards associated with a cleaning line is undesirable). 
     TECHNOLOGY 
     The following principles apply to the state of the art as well as to the present invention. 
     1. The “fine cleaning” process implies a high degree of opening (in other words: it is not possible to eliminate trash hidden inside fibre clusters). 
     2. A high degree of opening implies application of “nip feeding” (to be explained in the following). 
     3. A fine cleaning process using nip feeding at higher throughput rates implies closer settings if good results are to be achieved. Consequently nep generation (measuring value: nep count) and fibre damage (measuring value: short fibre contents) tend to increase. 
     4. If gentler cleaning is attempted (less intensive—without nip feed), risks are taken that small trash particles are eliminated insufficiently and that unnecessary losses of good fibres occur. A system (“cleaning diagram”) illustrating the corresponding compromises at the operating interface of the individual machine (or of the plant control) is given in EP-A-452676 (U.S. Pat. No. 5,361,458) and has been introduced to the market under the trade mark Varioset”. 
     5. Nip feed is harmless at relatively low throughput rates. Successful fine cleaners of the 60&#39;s and 70&#39;s were based thereon, as blowroom throughput rates were relatively low at that time. 
     Returning to the production conditions of the 60&#39;s and 70&#39;s, certainly is out of the question (compare the notes mentioned already concerning the increased processing capacity of the individual machines) but the idea can be taken up insofar as fine cleaning can be effected at a point where the fibre material flow has been subdivided already (e.g. for subsequent carding), e.g. in a card feed chute. 
     DE-A-2532061: 
     DE-A-2532061 concerns dedusting of cotton provided for processing on open end spinning machines. For this purpose, an additional cleaning point is provided in the feed chute, i.e. the fibre material has been cleaned already according to known principles. In other words, the fine cleaning machine was not planned to be dispensed with, and this actually was not done in practical application. 
     According to DE-A-2532061 processing in the feed chute is to be intense—opening to the individual single fibres—for ensuring that the dust is set free and can be eliminated. Furthermore the following points are to be noted: 
     1. In the year 1975 (priority date of DE-A-2532061) card production was relatively low. Thus, at that time, moving the basic cleaning operation into the feed chutes did not make sense as a total production corresponding to the processing capacity of the card room could be taken care of efficiently by a conventional cleaner. It did, however, make sense to transfer the intense opening action for dedusting purposes according to DE-A-2532061 into the feed chute (relatively small quantities of fibre material, as mentioned in the document). 
     2. In DE-A-2532061, no “co-operation” between the feed chute and the card is mentioned. 
     DEFINITIONS 
     The term “nip feed” in this description, where used in the following without an explanation, refers to “nip feed with subsequent cleaning function” in which arrangement the elimination of material is considered as an essential characteristic of the cleaning function. This definition is discussed briefly in the following. 
     The nip feed is important for the finer opening (the finer cleaning) favouring the fine cleaning process. The present invention, however, does not concern the opening process as such. Insofar as the intense opening action (resolving) must be provided for other purposes than cleaning (e.g. for mixing), it is not influenced directly by the present invention. The total stress load the material is subject to, however, is reduced if the present invention is applied, from which the application of nip feeding may benefit in connection with other functions than cleaning. 
     A plurality of embodiments of the present invention are described in the following with reference to illustrated design examples. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a copy of the FIG. 1 from EP-A-399315, 
     FIG. 2 is a copy of the FIG. 1 from CH 0935/96 dated Apr. 12, 1996, 
     FIG. 3 is a modification of the arrangement according to the FIG. 2 forming an apparatus according to the present invention, 
     FIG. 4 schematically shows two alternative design examples of a blowroom/carding room plant according to the present invention for processing cotton and/or chemical fibres, 
     FIG. 5 schematically shows a blowroom/carding room plant for processing blends of cotton and chemical fibres, 
     FIG. 6 is a diagram of the cleaning process in a blowroom comparing the process according to the present invention with processes in conventional blowrooms, 
     FIG. 7 illustrated diagrammatic curves of the corresponding nep count values, 
     FIGS. 8A through 8J show various nip feed arrangements, 
     FIG. 9 schematically illustrates a first possibility of realising the cleaning function in a feed chute according to the FIG. 3, 
     FIG. 10 schematically shows a further possibility, details being shown at an enlarged scale in FIG. 10A, 
     FIG. 11 a third possibility, and 
     FIG. 12 the fibre material feed arrangement with a feed chute according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to one or more presently preferred embodiments of the invention. One or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used on another embodiment to yield still a further embodiment. 
     A blowroom plant of a design known as such is shown in FIG.  1 . Fibre flocks are taken off from fibre bales  2  by means of a bale plucker  1  and are transferred via a conveying duct  3  to a first cleaning machine, e.g. a coarse cleaning machine  4 . In the conveying duct  3 , the quantity of flocks transported per unit time, e.g. in cubic meters per hour, can be determined using a measuring device  54 . In a plant of the type illustrated, however, this measurement is dispensed with, in which arrangement reserve storage devices (feed chutes) are provided on certain machines, as to be described for the card in the following with reference to the FIG.  2 . 
     The coarse cleaner  4  is not equipped with a feed chute but is laid out in such a manner that it can take up, process, and transfer further the maximum quantity that can be produced by the bale plucker  1 . The machine  4  is not provided with a nip feed arrangement, and a description of its function can be found e.g. in EP-A379726. In any case, trash is eliminated and the fibre flocks, already much reduced in their size (i.e. at least partially opened), are conveyed via a second conveying duct  5  to a second cleaning machine, e.g. a fine cleaning machine  6 , and are further opened and cleaned more intensely than in the first mentioned machine  4 . 
     Subsequently, the cleaned flocks are transferred via a further conveying duct  7  to a feed arrangement (a feed chute)  8 . From this feed arrangement  8  a fibre lap  9  is delivered via a slide  10  into a card  11 . In the FIG. 1, one single card only is shown. The total production delivered by a fine cleaning machine  6 , however, is subdivided in a suitable flock feed system (e.g. according to EP-A-311831 and/or U.S. Pat. No. 4,940,367) and delivered to a plurality of cards  11 . It can be assumed here that all cards  11  are identical and that the description of one individual card (with reference to the FIG. 2 in the following) thus applies to the others as well. 
     In the FIG. 1, many more elements are shown (e.g. the control system  53  for the plant) which are important for the invention according to EP-A-399315, but are irrelevant for the present invention. A further description of these elements here is dispensed with, reference being made to the above mentioned document. The present invention described herein is not restricted to a control arrangement of the type illustrated, however, alternative solutions being shown e.g. in DE-A-3237864 and in EP-A-497535. 
     In the FIG. 2, a revolving flat card known as such is shown schematically, e.g. the card type C50 produced by Maschinenfabrik Rieter. The fibre material delivered by the flock feed arrangement in flock form is fed into the feed chute  8 , is taken over by a licker-in  39  (also called taker-in) as a lap, is presented to a card cylinder  40  (also called main drum) and under co-operation of the card cylinder with a set of revolving flats  50  is opened further and cleaned. The revolving flats of the set of revolving flats  50  are guided, driven by a suitable drive system for the set of revolving flats, via deflecting rolls  56  along a closed path (in the direction of the rotation of the card cylinder or in the opposite direction). Fibres from the fibre web placed on the card cylinder  40  are taken off by means of a takeoff roll  43  and, by a delivery arrangement  80  consisting of various rolls, are formed into a fibre sliver  90 . This card sliver  90  is deposited by a coiler arrangement  13  in cycloid windings into a transporting can  111 . The card  11  is provided with its own programmable control arrangement  120  and also a suitable “operator interface”  210  (e.g. a keyboard, and a display respectively), is provided for data input and/or output of status reports. 
     In the FIG. 3 the card  11  is shown again with the feed chute  8  coordinated to it. The latter comprises an upper part (an infeed chute)  31  (compare also the FIG.  1 ), as well as a lower chute part (reserve chute)  34 . Fibre flocks from the lower chute part  34  are delivered by two delivery rolls  35  as a lap  9  mentioned before and are transferred by the feed roll  37  to the card  11 . 
     Between the upper chute part  31  and the lower chute part  34 , a supply device  32  is arranged (compare the FIG. 1) which feeds the flocks to an opening roll  33 . Devices of this type are well known in general. It now is proposed to adapt this device in order to create an apparatus according to the invention which permits substantial changes to be made in the parts of the plant arranged upstream. In principle, the supply device  32  and the opening roll  33 , together with the neighbouring portion of the housing of the chute, are transformed in such a manner that they function as a “fine cleaner”. 
     The function of this cleaner can correspond to well known principles, e.g. according to EP-A-419415 (U.S. Pat. No. 5,123,145) and/or EPA-481302, which represent more recent designs of the fine cleaner. These more modern machines permit intense cleaning action also at high throughput rates. It is not necessary, however, in an arrangement according to the FIG. 3, to apply such more modern principles, as the throughput rates in the feed chute of a card is relatively low at e.g. more than 70 kg/h, preferentially more than 100 kg/h, but far below 500 kg/h (production rate of a fine cleaner as applied today) compared to the throughput rates of a modern blowroom line. Fibre quantities of e.g. 100 kg/h and 200 kg/h can be satisfactorily cleaned according to the principles discussed e.g. in the older documents CH-C-464021, EP-A-108229 and/or EP-A-110017. 
     Adaptation in any case involves incorporation of elements at the circumference of the roll  33  permitting elimination of trash and impurities. In the FIG. 3 grid bars  102  are shown schematically with free spaces between them (not indicated specifically). The free spaces permit elimination of the trash into a collecting chamber  103  which can be connected to a suction system (not shown) for taking away the material eliminated. The connection to the suction system can be established continuously or, preferentially, intermittently. The present invention is not restricted to the application of the illustrated elements  102 . Eliminating elements e.g. of the form of “suction assisted knifes” are known which can be applied in the arrangement according to the FIG. 3 additionally or alternatively. 
     The feed device  32  represents a “nip feed” for the opening roll  33 , as explained in the introduction. This nip feed arrangement consists of a feed roll  321  and a through-shaped feed plate  322 . Many other forms of such nip feed arrangements also are known, as e.g. can be seen from EP-A-383246 and EP-A-470577 respectively, which also can be used in the newly proposed cleaning point. In a preferred arrangement which is schematically indicated in the FIG. 3, the nip feed arrangement is laid out as a “metering” kind of arrangement according to EP-A383246. This, however, does not constitute an essential feature of the present invention. 
     The arrangement according to the FIG. 3 is conventional as to the transfer of the lap from the chute to the card. The new cleaning point is applicable, however, also in other arrangements, e.g. where the chute  8  is connected to the card in such a manner that the intermediate rolls  35  can be dispensed with. Arrangements of this type are shown e.g. in DE-A-3733631, DE-A-3733632 and DE-A3734140. Also a plurality of licker-in rolls  39  could be provided as proposed e.g. in DE-A-4331284. 
     The present invention furthermore is not restricted to an application in a revolving flat card. Also e.g. fixed flat cards are known (see DE-A-4418377), which also can be equipped with a feed chute each according to the present invention. The present invention also can be applied in combination with so-called roller cards for processing long staple fibres. 
     The new cleaning point preferentially is incorporated into the chute control arrangement as shown schematically also in the FIG.  3 . This control arrangement as a rule comprises a control device  323  for a variable rotational speed motor  324  driving the feed roll  321 . The control device  323  is connected to a filling level sensor  325 , of which various types (optical or pressure sensitive sensors) are known, apt to fulfill this task, a further description thus not being required here. Using a suitable control algorithm, the filling level in the lower chute part  34  can be maintained within pre-settable tolerances. Also a sensor S can be provided at the delivery point which can be connected to the control device  323  in such a manner that the production of the cleaning point can be adapted to the throughput rate of the card. An arrangement of this type (for a feed chute without a Cr cleaning point) is known from DE-A-3625311 as well as from DE-A-3244619 (U.S. Pat. No. 4,535,511). 
     Also known according to the state of the art is a further alternative embodiment indicated in the FIG. 3, namely an arrangement in which a displacement or force sensor  326  is provided connected to the control device  323 . The sensor measures the displacement that has occurred on the feed plate  322  or the forces exerted thereupon in order to permit some kind of a “metered supply” (e.g. according to EP-A-383246) to be effected. 
     It now is possible to control the card  11  and its feed arrangement (from the feed chute  8 ) as a “unit” for which purpose of both machines can be integrated or interconnected. An arrangement of this type proves particularly advantageous in a combination with the present invention as in this arrangement the cleaning actions effected by the card itself and by the cleaning point coordinated to the card can be mutually adapted, e.g. according to the “VARIOset” principle which is explained in EP-A-452676 and which has been supplemented in the Swiss patent application CH 935/96 dated Apr. 12, 1996. 
     In principle, the newly proposed cleaning point can be designed in such a manner that it is capable of processing fibre material which has not passed a nip feed of any kind previously. In any case, the cleaning point is to be conceived in such a manner that material can be processed which has not passed previously through a cleaning point provided with a nip feed arrangement. A fibre material of this type (in the upper chute part  31 ) should show a nep count which is less than 50% higher than the nep count in the material laid down at the bale plucker. The short fibre contents of the material in the chute part  31  can be higher by less than 5% than the corresponding value in the previously mentioned raw material (measured according to the known and proven Almeter-measuring method). The following example should clarify the latter statement—if the short fibre contents; in the bale mix laid down is X% (e.g. 30%), the short fibre contents in the upper chute part  31  should not exceed (X+5%)—in the case considered &lt;35%. 
     The cleaning point provided in the chute  8  is not necessarily laid out for ensuring dedusting action, although dust always is eliminated (to a certain extent) where a suction action is applied. The newly proposed cleaning point should not be laid out in such a manner that opening to the individual single fibre is aimed at. Such an elevated degree of opening in the chute is undesirable. 
     Particularly if chemical fibres are to be processed, a coarse cleaning step (machine  4 , FIG. 1) possibly can be dispensed with altogether. In this case it may prove advantageous, however, to provide an additional opening point (possibly with a nip feed but without trash elimination) in the plant, e.g. in a blending machine (not shown in the FIG.  1 ). In any case, fine cleaning upstream from the card feed chute  8  (i.e. the machine  6 , FIG. 1) can be dispensed with. 
     In the FIG. 4, three blowroom machines  1 ,  4 ,  90  are shown arranged in a line followed by a card  11  of a group of cards supplied with fibre material from the blowroom line. The various machines illustrated are shown in different scales, the FIG. 4 aiming merely at explaining the processing steps. These steps first are described for the processing of a fibre blend consisting of 100% cotton, and in the following an alternative arrangement is described in which a fibre blend consisting of 100% chemical fibres is processed. The card  11  and its feed chute  8  are laid out as shown in the arrangement according to the present invention illustrated in the FIG.  3  and thus are indicated here in their outlines only. 
     The reference sign  70  refers to the swivel tower of a bale plucker  1 . The tower is pivotably mounted on a movable carriage  72  and supports a plucking arm  73  of known design plucking or milling off fibre flocks from the bales laid down (not shown in the FIG. 4, but compare bale  2  in the FIG.  1 ). The carriage  72  is arranged movable along rails  74  along a conveyer duct  75 , the bales mentioned before being laid down to one or the other side, or to both sides respectively, of the rails, in which arrangement the plucker arm  73  contacts the top surface of the bale. In the duct  75 , a transporting air stream is generated by suitable means (not shown). The arm  73  comprises at least one rotatable plucker or milling roll (not shown) which takes off the fibre flocks and supplies them via a connecting duct (not visible in the FIG. 4) in the tower to the conveyer duct  75 . The conveyer duct  75  is covered by an endless cover belt  76  which together with the carriage  72  moves in longitudinal direction of the duct  75 . At one end of the path of movement of the carriage, a control desk  77  is arranged. The bale plucker  1  according to the FIG. 4 in principle is of a conventional type, e.g. a “UNIFLOC” type machine, which is marketed world-wide by Maschinenfabrik Rieter, similar machines being offered by other textile machinery producers, which machines can be applied in this first processing step. 
     As indicated schematically by the arrow shown with solid lines, the conveyer duct  75  merges into the transporting duct  3  (comp. FIG. 1) which leads to the intake  81  of a coarse cleaner  4 . The stream of air/fibres then first flows through a dedusting zone  82  where a part  83  of the air stream is eliminated via a perforated wall  84 . The remaining flock/air stream is guided on a spiral path around a drum  16  which is provided with a beater  17 , in which arrangement part of the impurities carried on drop through grids  86  into a chamber  21  arranged below the grids. From this chamber  21  the collected impurities can be eliminated using a transporting suction action (not shown) via an air lock  88 . The intake opening for the fibre/air stream is provided at one axial end of the perforated drum  84  and an outlet is provided at the other end of the drum  84 . Further details concerning this machine are described e.g. in EP-C-381860, EP-C- 379726, EP-C-447966 and EP-C-455017, a machine of the type mentioned being marketed under the name “UNICLEAN”. The most important feature of this machine is, that in the second processing step the cotton flocks are cleaned in free flight (without being nipped or held back). Machines marketed by other manufacturers are conceived also for cleaning the flocks by beating them in free flight, in some of which arrangements a plurality of rolls (e.g. “Duorolls”) are arranged side by side. Machines of this type can be applied also in the second processing step in processing cotton fibres. 
     From the coarse cleaner  4 , the fibre flocks are conveyed by the pneumatic transporting system via the duct  5  (compare the FIG. 1) to a blending machine  90 . The machine  90  comprises a plurality (six in the design example illustrated) vertically arranged drop chutes  91  where the flocks are separated from the transporting air. All chutes are connected via a common inlet with the transporting duct  5  in such a manner that each chute  91  takes up fibres from the same supply batch. 
     The drop chutes  91  merge into a blending chamber  92  where the fibres are carried on by a horizontal transporting belt  93  against an inclined transporting means (e.g. a belt with needled slats)  94 . The transporting means  94  takes fibres from the blending chamber  92  and transfers them to a drop chute  95  in which arrangement rolls  96  co-operate with the transporting means in such a manner that fibre lumps are thrown back into the blending chamber, or are opened respectively. Owing to the different path lengths the fibres cover in the various chutes  91  and in the chamber  92  until they reach the transporting means  94  a phase shift occurs while the different “fibre portions” are transported as indicated schematically in the FIG.  4 . This phase shift results in a blending of the fibres which were taken off the bales in a sequence from different bales. The basic principle of the function of this machine has been described in CH-C-511951, a more modern version of this machine being marketed under the name of “UNIMIX”. Alternative solutions also in this case are proposed by other manufacturers for fulfilling the same function, which arrangements can be laid out in such a manner that a so-called doubling effect (e.g. according to DE-A-3151063) is achieved. Machines of this type are apt also to effect the third processing step (the blending step) according to the present invention. 
     The machines in the arrangement of the blowroom line described thus far with reference to the FIG. 4 all are of conventional design and their known effects remain unchanged. The chute  95 , however, is followed by a delivery unit  97  which in the plant illustrated must be changed according to the present invention as will be explained in the following. 
     In plants known thus far the unit  97  delivers flocks to a tube  98  merging into a pneumatic transporting system for transferring the flocks to a fine cleaner  6  (FIG.  1 ). The fine cleaner  6  often also serves as a feeder machine for the flock feed system to the card room (see duct  7 , FIG.  1 ). According to the present invention, however, no “fine cleaning machine” is provided as a separate blowroom machine. The delivery unit  97  thus must take over the function of a feeder machine, and the delivery tube  98  thus merges into a duct  100  via which the flocks are conveyed to all the cards of the group of cards coordinated to the feeder machine. In the FIG. 4 merely one card  11  of this group is shown, the continuation of the duct  100  supplying flocks to further cards being indicated. 
     The flock feeding system for the cards as such is not influenced by the present invention and thus is not explained in all details here. But the flock feeding system requires a control system, for which in the FIG. 4 a sensor  101  and a control unit  102  according to EP-C-303023 are shown, which unit  102  also receives signals from the cards and correspondingly regulates the feeder machine (delivery unit  97 ), which is indicated schematically with the circuit  103  and is explained in the above mentioned EP document. If the feeder machine is working according to the so-called stop-and-go mode, which is not relevant in the context of the present invention, the control system also can be laid out according to EP-C311831 in order to permit “stop-and-go optimising”. 
     The delivery unit  97  (as illustrated in the FIG. 4) itself represents an opening point as it comprises an opening roll  104  with a nip feed arrangement (in the form of a pair of feed rolls  105 ). In another known alternative design, the delivery unit  97  consists of a direct (by-pass) connection between the chute  95  and the tube  98  if the fibre material in process does not require opening action at this point. The delivery unit  97  in any case is laid out preferentially as a controllable unit which can take over the flock feeding function, as otherwise an additional feeding machine would have to be provided. The controllable unit also could consist of the chute  95  and the pair of feed rolls  105  (without the opening roll  104 ) in which arrangement the pair of feed rolls  105  delivers the fibres directly into the transporting air stream which is generated by suitable means (not shown) in the tube  98  and the duct  100  respectively. This signifies that the plant now can be laid out without a nip feed point being provided upstream of the card feed chute. 
     The delivery unit shown in the FIG. 4 being integrated into the blending machine of course could also be designed as a separate module which takes the fibres from the blending machine and delivers them in a controlled manner. 
     In processing chemical fibres (also called synthetic fibres), no cleaning of the material to eliminate impurities is required, i.e. the coarse cleaner  4  also is not required. In this case transfer can be effected from the duct  3  directly into the duct  5  which is indicated with the arrow  80  shown in dashed lines in the FIG.  4 . But in this case it proves advantageous to design the delivery unit  97  as an opening point. 
     In the FIG. 5, a blowroom plant is shown conceived in such a way that cotton and synthetic fibres can be blended and transferred to a card room (not shown in the FIG. 5) according to the present invention. The plant comprises a bale plucker  1 , a coarse cleaner  4  and a blending machine  90 , in a configuration which differs, however, from the one shown in the FIG.  4 . The duct  3  now is provided with a branching arrangement A (a controllable flap) via which flocks can be conveyed selectively to the coarse cleaner  4  (via the branch  3 X) or to the blending machine  90  (via the branch  3 Y). The working zone of the bale plucker  1  is subdivided into “blocks”, in which arrangement each block can be occupied by “its own” fibre (cotton or synthetic fibres, such as Polyester) type (for a process of this type compare e.g. EP-C-221306). 
     The flocks of the cotton fibre material(s) to be processed contain impurities which are to be eliminated as far as possible. The cotton flocks thus are conveyed to the coarse cleaner  4 . The flocks of the synthetic fibres to be processed on the other hand do not contain any particles to be eliminated. They thus are conveyed directly to the blending machine  90 . In order to operate in the manner cited (using only one bale plucker  1 ), the flap mentioned above is controlled as a function of the position of the plucker arm  71  relative to its working zone. The delivery unit  97  of the machine  90  comprises guide elements  107  which guide the fibre material from the chute  95  to the tube  98 , in which arrangement owing to the co-operation of the opening roll  104  with the pair of feed rolls  105 , this fibre material is opened, i.e. the flock size is reduced further. The delivery unit  97  in this case, however, does not serve as a feed machine for the card room, as the synthetic fibres are to blended in with the cotton fibres before being subject to the carding process. The latter processing step is effected in the blending machine  110  which works according to EP-A-628646, or EP-C-383246 respectively. 
     I The machine  110  comprises also a plurality of drop chutes (five in the example illustrated)  111  through  115  in which the flocks are separated from the transporting air stream. These chutes are not (as the chutes  91 , FIG. 4) connected to a common inlet, but they are provided each with a separate inlet  111 E,  112 E,  113 E,  114 E, and  115 E respectively. The chutes of the machine  110  thus can be individually supplied with fibres, in the illustrated example with five different types fibre. In order to simplify the illustration only two ducts  116 , and  117  respectively (one  116  for cotton, and the other  117  for synthetic fibres), are shown in which arrangement a separate feed duct could be coordinated to each chute  111  through  115 . If this duct, like the duct  117 , is connected to a blending machine  90 , a blending machine must be provided for each type fibre. An alternative design example comprising a blending machine  90 A connected to the duct  116  is indicated by the box shown with dashed lines, in which arrangement only one cotton fibre type can be supplied to the three chutes  111 ,  112 ,  113 . If blending upstream of the machine  110  can be dispensed with, it would be possible to send different types cotton fibre sequentially via a common duct  5 A to a chute  111 ,  112 ,  113  each, using a flap at the branching point AZ. In a case like this one, it proves advantageous to set the coarse cleaner  4  separately for each type fibre to be processed, e.g. according to EP-A-641870. Also in processing a single type cotton fibre the additional blending machine  90 A possibly could be dispensed with, if the three chutes  111 ,  112 ,  113  of the machine  110  together with the arrangement  120 ,  121  sufficiently take care of the blending action (with the help of doubling). These notes should make clear that the plant lay-out while being flexible still must be adapted to the actual requirements. 
     Each chute of the machine  110  is provided with a metering device  118  (indicated only on the chute  111 , the other chutes being identical) at its lower end. The function of this device  118  is described in EP-C-383246 and is not re-described herein. The metering devices  118  each build a fibre layer on a common transporting belt  119  which transports the material to a condensing device  120  which in turn compacts the fibre material into a lap composed of five layers. The lap is delivered to a (schematically indicated) opening unit  121  where again flocks are formed and delivered via a tube  123  on to a fan  124 . The air stream generated by the fan  124  can be used for carrying the fibre flocks on. The delivery unit  120 ,  121 ,  123 ,  124  as shown in this example serves as a feed machine for the card room. 
     The present invention thus provides a plant in which the flock feeding to the card room is effected by means of regulating the fibre material flow delivered by a blending machine which also is provided in EP-C-361276. The plant according to the present invention differs in many aspects from the one proposed in EP-C361276, e.g. in that: 
     in the feed unit a nip feed arrangement without an associated elimination of trash material can be provided, 
     no cleaning action is to be provided in the free flight of the flocks between the controllable feed unit and the card room, 
     a cleaning function can be performed in the card feed chute, 
     it is not necessary to take off excessive material from the upper part of the feed chute when the card is stopped. 
     These features can be applied individually or in any combination desired to a plant which differs in its structure as well as in its function from the plant according to EP-C-361276. 
     DEGREE OF CLEANING, NEP COUNT COURSE, DEGREE OF OPENING 
     In the FIG. 6 three diagrams A, B, C are shown which each display the course of the degree of cleaning in three different configurations of the blowroom processing line. Diagram A (upper diagram) corresponds to a blowroom plant (“blowroom I”) in which the cleaning function is concentrated in one single step. Diagram B corresponds to a blowroom processing line (“blowroom II”) in which the cleaning function is subdivided into a plurality of steps. Diagram C corresponds to a blowroom processing line (“blowroom III”) according to the present invention. Each of the diagrams starts out from a trash contents in the bales (stage B) in the order of 3%. In each of the diagrams, the stages coarse cleaning (G), blending (M), fine cleaning (F) and reserve chute (S, in the card feed chute) are listed even if in the blowroom plant I no coarse cleaner and in the blowroom plant III no fine cleaner are present. The diagram “curves” interconnect measured values, each measuring value representing the remaining trash contents at the delivery point of the stage concerned. In the FIG. 7 two diagrams are shown each of which displays the course of the nep count for the blowroom processing line  1 / 11 , and the blowroom processing line III respectively, each diagram starting out from an initial nep count value in the bales of the order of 250. The courses of nep count values being about equal for modern blowroom processing lines I and II, an average value for such blowroom processing lines merely is shown in the FIG.  7 . 
     The degree of opening is not displayed separately. But the course of the degree of opening approximately corresponds to the course of the nep count value. In other words, the nep count tends to increase with increasing degrees of opening, as it is “easier” to roll up well opened fibres into neps. Thus it is an advantage of the arrangement according to the present invention that the step of “fine opening” is effected relatively late in the process. The fibres thus can be transported via the transporting ducts in the form of rather coarse flocks which reduces nep formation in these ducts. 
     The nep count value also depends on the throughput quantity rates at the opening stage. Subdivision of the total quantity of fibre material to be processed to the card feed chutes before fine opening is effected thus presents an advantage in avoiding nep formation. 
     NIP FEED 
     In the following various examples of nip feed arrangements are discussed in more detail. These examples show the following common features: 
     FR  1  The fibre material to be processed is supplied in the form of a lap, e.g. layers of flocks. 
     This lap can be formed extending across the full working width. Its density should be as uniform as possible across the working width as well as in the longitudinal direction, but variations in density within pre-set limits, however, normally are unavoidable (under reasonable efforts), and thus the fibre material is supplied to an opening roll. 
     The material to be supplied in most cases is taken from a pneumatically transported flock stream, which requires separation of the flocks from the transporting air. Drop chutes have proven best suited for this purpose over the past thirty years. 
     FR 2  The feed speed is relatively low (e.g. lower than 0.5 m/s and typically lower than 0.1 m/s at supply rates ranging from 200 to 500 kg/h). 
     FR 3  The material to be supplied is taken through a nip line (or a nip zone respectively) which exerts a retaining force onto the material. The nip effect is to be distributed across the working width as uniformly as possible. The nip line can be created using various means as explained in the following with reference to the FIG.  8 . 
     FR 4  The fibre path between the nip line and the subsequent opening roll, or cleaning roll respectively, is shorter than 100 mm if fibres of a mean fibre length of up to 60 mm are to be processed. This parameter will be discussed in more detail in the following with reference to the FIG.  8 . Owing to the feature FR 4  good opening performance is ensured as the opening roll can pull fibres out of the material supply without tearing them. 
     The features FR 1  through FR 4  mentioned above equally apply to a nip feed arrangement provided in an opening unit as well as to one provided in a cleaning unit. Nip feeding or fine cleaning can be compared with the corresponding features of coarse cleaning: 
     GR 1  Fibre material is supplied in flock form, 
     GR 2  Supply speed is relatively high at &gt;5 m/s, 
     GR 3  Flocks are cleaned in free flight (not being retained, i.e. without a nip line). 
     In the FIGS. 8A through 8J different embodiments are shown schematically as examples of a feed device  32  with a nip feed arrangement. The various embodiments additionally are conceived as metering devices according to EP-B383246, which is not essential in the context of the present invention, however. If the metering function is not required in a specific case, the feed device can be simplified accordingly as measurement of the distance “X” in the nip feed gap, to be provided according to according to EP-B-383246, is not required here. Also, if metering is provided, it possibly is sufficient for an application in a card feed chute to measure a volume flow (rather than a mass flow). In cases of this type it is possible to dispense with particular measures aimed at maintaining constant density of the fibre material in the nip feed gap. 
     In the FIG. 8K then a simplified alternative solution (without metering) is shown. 
     In the illustrations given in the FIGS. 8A through 8K, the distance between the nip line and the point where the fibres are taken over (in the sense of EP-A419415) is given as “P” in each case. This distance (according to the feature FR 4  mentioned above) for processing “short staple fibres” (cotton and chemical fibres of corresponding staple lengths) is chosen smaller than 100 mm and preferentially ranging from 14 mm to 40 mm. The “cleaning parameter” P according to EPA-419415 can be adjustable in such a manner that the parameter can be adapted to the fibres to be processed. The parameter P can be rendered adjustable using a control system based on a set of characteristic curves of cleaning action according to EP-A-452676. 
     The arrangement of a metering device  32  with feed rolls  318 ,  320  and the opening roll  33  is shown in the FIG.  8 A. 
     The two side walls  156 ,  158  of the flock chute extend into close vicinity of the feed rolls  318 , and  320  respectively, and mutually diverge slightly in such a manner that formation of flock congestion is prevented. The flocks  160  in the chute  3  are taken over by the feed rolls  318 , and  320  respectively, which rotate in the direction of the arrows in opposite directions, and are compressed into a flock lap  162 . The opening roll  33  thereupon takes the flocks off from this lap and generates a flock stream  132 , which moves on in the direction of the arrow  164 . All flocks carried on by the feed rolls rotating at a rotational speed n are transported via a transporting gap the height x of which forms the smallest distance between the two feed rolls, the width of which gap corresponds to the working width of the feed rolls, or to the width of the side walls respectively of the chute. 
     The rotational axis of the feed roll  318  is designated  166 , and the rotational axis of the feed roll  320  is designated  170 . The rotational axis  166  of the feed roll  318  as well as the rotational axis  170  of the opening roll  33  are fixedly arranged in the flock feed chute. The rotational axis  168  of the feed roll  320  on the other hand is supported by two arms  172 , one of which only is visible in the Figure. The second arm  172  is arranged at the other face side of the feed roll  320  and is identical to the arm  172  shown. This arm  172  is supported on the opening roll  33  and thus can pivot about its rotational axis  170  in the directions of the double arrow  174 . As can be noticed, such pivoting movements result in a change in the distance x. 
     On the right hand side of the Figure a pre-tensioning device  176  is provided in the form of a pre-tensioning spring  178  which with one of its ends rests against a stop  180  fixedly located on the feed chute and with its other end rests against a stop  182  connected to the arm  172 . Between the stop  180  and the stop  182  a rod  184  extends which is adjustably arranged within the stop  182 . Of course at the other face side of the feed roll  320  a second pre-tensioning device is arranged which also exerts pressure onto the arm  172 . The two springs  178  thus tend to diminish the distance x. The minimum distance x is determined by a stop device  186  which cooperates with the arm  172  shown. A further stop device is provided at the other face side of the feed roll  320  and there cooperates correspondingly with the arm  172  arranged there. 
     During operation the distance x adjusts itself according to the pressure prevailing in the feed chute, to the density and the degree of opening of the flocks, and the force exerted by the springs  178 , in which arrangement the measure of the distance x can be checked by scanning the shifting movements of the rod  184  within the stop  182 . The rod  184  and the stop  182  thus are designed as a distance measuring device. 
     The metering method and the control action performed have been explained in EP-C-470577. 
     In the FIG. 8B an embodiment is shown which closely resembles the embodiment shown in the FIG. 8A, but in which the feed roll  318  no longer is driven separately but is arranged freely rotatable. This arrangement is based on the finding that the flock stream driven by the feed roll  320  exerts considerable friction forces onto the feed roll  318 , particularly if the surface of the feed roll  318  is not smooth but is provided with a surface structure which causes an increase in the coefficient of friction, these friction forces being entirely sufficient to drive the feed roll  318  at a surface speed corresponding to the speed of movement of the flock stream, and to the surface speed of the feed roll  320 . 
     Except for the change mentioned, the lay-out of the embodiment according to the FIG. 8B most closely resembles the embodiment according the FIG. 8A, for which reason the same reference signs are used to designate the same elements, and a separate description of these elements is not required. It will be sufficient to note that the rotational axis  166  of the feed roll  318  is fixedly arranged whereas the feed roll  320  is driven in the direction of transport. The inverse arrangement also would be possible, in which only the feed roll  318  is driven and the other feed roll  320  is laid out freely rotatable. 
     In the embodiment according to the FIG. 8C, the arrangement of the opening roll  33  and of the driven rotatable feed roll  320  remain unchanged, the same reference signs being used again for these elements. But the feed roll  318  is replaced by a fixedly arranged slide plate  300  which together with the feed roll  320  forms a feeding gap  302  the height of which is minimum at the point  304 . 
     In the embodiment according to the FIG. 8D, the slide plate  300  is replaced by a revolving belt  306  which is guided around two deflecting rolls  308  and  310 . The upper deflecting roll  308  is driven as shown in this example and rotatable about an axis  312 , namely in the direction of the arrow  314  at a speed at which the surface speeds of the belt  306  in the direction of the arrow  316  and the surface speed of the rotatable feed roll are equal. The arrangement of the rotatable feed roll and of the opening roll  33  correspond to the arrangement shown in the FIG. 8A, the same reference signs being used. This arrangement is not described further here for the sake of a shorter description. 
     In the case of a revolving belt  306 , provision of a deflecting roll in the lowest portion of the loop formed by the belt is not necessarily required. Instead, the belt can be guided over a triangular guide body  218 . In this design example it also is feasible not to drive the belt at all, as it can be moved under the influence of the friction forces exerted by the flock stream. In such a case it is desirable to provide a deflection roll  310  which is freely rotatable about the axis  220  in addition to the deflection roll  308  which in this case also is freely rotatable in order to keep the friction hindering free movement of the revolving belt as low as possible. The minimum height  304  of the feed gap  302  in this example also is located at the lower end of the revolving belt. 
     In the FIG. 8E, an embodiment is shown with a driven feed roll  320 . 2  and a fixedly arranged feed plate  322 . The feed roll  320 . 2  is rotatable in the direction of the arrow about the rotational axle  168 . 2 , and the rotational axle  168 . 2  at both its ends is supported by the corresponding arm  172 . 2  each, both arms  172 . 2  (one of which only is visible in the FIG. 8E) being linked at the upper end of the feed plate  322  to the rotational axle  324 . The feed gap  302  in this example shows its minimum height at the point  304 . This arrangement of the feed roll  320 . 2  permits changes in the minimum height to be effected at the point  304  by means of pivoting movements of the arms in the direction of the arrows  174 . 2 . The pre-tensioning arrangement  176 . 2  is designed according to the one shown in the FIG. 8A but extending from the top it rests against the lower end of the arms  172 . 2  and thus presses the feed roll in the direction of the feed plate  322 . 
     In the embodiment shown in the FIG. 8F, both feed rolls are replaced by revolving belts  306  and  326 . The arrangement of the belt  305  revolving about the deflecting rolls  308  and  310  exactly corresponds to the arrangement of the corresponding revolving belt  306  shown in the FIG. 8D, for which reason in this arrangement the same elements are designated by the same reference signs, and the arrangement is not described further here. The revolving belt  326  is laid out in similar manner, i.e. it revolves about an upper deflection roll  328  which is driven and which rotates about an axis  330 . The revolving belt  326  also is guided around a lower deflection roll  332  which rotates freely about a rotational axle  334 . Onto both ends of this axle  334  a pre-tensioning device  176 . 3  acts which is laid out substantially corresponding to the ones shown in the preceding Figures, an additional measure being taken, however, in that the elements  182  at both ends of the rotational axle are interconnected mutually via a solid rod  336  which ensures that the gap height at the narrowest point  304  of the feed gap  302  is maintained constant over the full axial length of the deflecting rolls  310 , and  332  respectively. A rod  336  of such type also can be incorporated also in the other embodiments shown. The rotational axle  330  of the deflecting roll  328 , as well as the rotational axle  334  of the roll  332  are mounted onto a common support member (not shown) pivotable about the axle  330 . 
     In this example either both revolving belts are driven at the same surface speed or if desired only the revolving belt  306  or the other revolving belt  326  is driven and the other belt can revolve freely. In the case in which freely revolving belts are provided, the lower deflection point preferentially is to be designed as a freely rotating roll. In the case of driven belts also deflecting bodies like e.g.  318  or  338  can be provided in which arrangement the deflecting body  318  can be arranged fixedly and the deflecting body  338  movably. In this arrangement the mobility of the deflecting body  338  is limited to a pivoting movement about the axis  330 . Also in this example the minimum height  304  varies during operation, and such changes in this distance are taken into account in the regulation of the surface speed of the driven revolving belt, or belts respectively. 
     In the FIG. 8G a further development of the embodiment according to the FIG. 8C is shown in which the rotatable feed roll  320  is replaced by a revolving belt  326  according to the FIG.  8 F. As the arrangement of the revolving belt  326  has been described extensively with reference to the FIG. 8F a further description of the same element can be dispensed with here. It should be noted, however, that the revolving belt  326  in this example definitely must be a driven belt. Also in this example the height  304  varies during operation, and the changes in this height are taken into account in the regulation of the surface speed of the revolving belt  326 . This revolving speed of course is pre-set just as in all the other embodiments in which revolving belts are applied, by regulation of the rotational speed of the driven deflection roll coordinated thereto, in the case shown the deflecting roll  328 . 
     In the FIG. 8H an embodiment is shown in which the feed roll  320 . 5  is driven in the direction of the arrow rotatably about a fixedly arranged rotational axis  168 . 5 . The feed roll  318  in this case is replaced by a spring -loaded feed plate  370 , i.e. the plate is pre-tensioned in the direction of the arrow  372  against the flock mass using a pre-tensioning device  176 . 5 . Guides  374  and  376  arranged below and above, and to both sides of, the plate  370  to ensure that the plate can move only in the direction of the arrow  372 . Also here the measuring device which transmits a signal reflecting a change in the distance  304  of the minimum height of the feed gap  302  is incorporated into the pre-tensioning device  176 . 5 . Instead of realising the spring loaded plate in the illustrated form, the plate itself cold be designed as a flat spring, in which case a separate measuring feeler would be required in order to check the changes occurring in the distance  304  during operation. 
     In the FIG. 8J a further development of the embodiment according to the FIG. 8A is shown in which both feed rolls  318 . 4  are to be arranged at fixed mutual distance set for a certain production rate m and are to rotate about fixedly arranged rotational axles  166 . 4  and  168 . 4  in rotational directions indicated by the arrows. The opening roll  33  in this arrangement rotates about the rotational axle  170  which also is arranged fixedly. 
     The rotational axle  168 . 4  of the feed roll  320 . 4  is supported at both its ends by plates  340  of substantially triangular shape as seen from the front side (one of which only being visible in the FIG. 8J) in which arrangement the two plates are interconnected by connecting rods (not shown). The plates  340  again are arranged pivotable about a fixed rotational axle as indicated by the double arrow  344 . During operation a fixed position of the triangular plates  340  and thus also of the rotational axle  168 . 4  of the feed roll  320 . 4  is chosen, however. Positioning is effected by means of a threaded spindle  346  which extends through a solid body  348  threaded inside. A hand wheel  350  which also can be replaced by a motor drive permits rotation of the threaded spindle  346  in such a manner that the position of the triangular plates  340  can be determined. As a corresponding spindle arrangement is provided also for the second triangular plate, which is not shown, the two spindle dries are to be mutually coupled which can be effected e.g. via the revolving belt  352 . 
     At the end of each of the threaded spindles  346  a yoke  354  is arranged, the legs  356  and  358  of which are arranged adjacent to one side each of an extension lobe  360  of the corresponding triangular plate  340 . Between each leg  356  and  358 , pressure force sensors  362  and  364  are provided which are connected to a computer via circuits (not shown). During operation the two feed rolls transport the fibre material through the feed gap  302  and via the point of minimum height  304  a force P acting onto the feed roll  320 . 4  tending to pivot the triangular plates  340  about the rotational axle  342 . No actual pivoting motion can occur as it is suppressed by the spindle and yoke arrangement. The pressure force gages  362  and  364  permit determination by means of the computer of the value of the force exerted, taking the geometric conditions into account. 
     The variations of this force correspond to the variations in density of the flock stream at the point  304  which are processed in the computer in order to regulate the rotational speed of the feed roll  320 . 4  and, if required, of the feed roll  318 . 4  in case this roll is driven also, or alternatively, in such a manner that the desired mass flow m soll  is maintained constant. 
     If the production rate of the chute is to be changed, this change can be effected either by merely changing the rotational speed of the feed roll  320 . 4  and possibly of the feed roll  318 . 4  as well. If, however a wider range of adaptability is to be created, the minimum height  304  can be adapted or set using the spindle  346  in such a manner that the changes in rotational speed of the feed rolls can be kept within pre-determined limits independently of the production rates desired for each application. 
     Finally it is to be mentioned that the embodiment shown in the FIG. 8J in which the distance  304  is maintained constant and in which the value of the force which tends to push the feed elements apart is measured, can be applied accordingly to all the other embodiments proposed instead of the pre-tensioned devices described. 
     Even if in the FIGS. 8B through 8G the pre-tensioning devices  176 ,  176 . 3  and  176 . 4  are shown in a form as the one shown in the FIG. 8A, it is evident that in practical application pre-tensioning devices preferentially are realised using gas pressure loaded springs or hydraulic devices, in order to maintain the pre-tensioning force constant independently of any changes in the minimum height  304 . 
     In such a manner, offsetting forces are generated which, also if conventional pressure springs are used, lead to a net force which results in a pre-tensioning force remaining unchanged, or slightly changed only, as the settings of the feed arrangement are adapted. 
     In all embodiments according to the FIGS. 8A through 8J plates are provided of course at the face sides of the feed devices, and of the opening roll respectively, limiting the mass of flock material, or the flock stream laterally at the sides of the feed gap. 
     In the FIG. 8K an arrangement according to EP-A-419415 is shown schematically with an opening roll  33  and a feed device  32  which comprises a feed roll  320  and a feed plate  300 . The directions of rotation of the rolls (indicated with arrows) cause a concurrent flow, i.e. the fibre material is carried away from the feed plate  300  by the roll  33  and after being taken over by the roll  33  is not carried back between the feed plate  300  and the surface of the roll  300 . The feed roll  320  is arranged relative to the roll  33  in such a manner that a condensing gap V is defined between the radius R of the roll  33  and the radius r of the roll  320  extending on the line connecting the two roll centres. The condensing gap V defines the “take-over point” where the fibre material is taken over by the roll  33 . 
     The feed plate  300  is arranged relative to the feed roll  320  in such a manner that a narrowest passage ES is defined. The distance “p” between the narrowest passage ES and the condensing gap V according to EP-A-419415 is to be adapted to the staple length of the material in process. Preferentially this is effected by adjusting the position of the feed plate relative to the roll  320  as indicated with the double arrow in the FIG.  8 K. The position of the feed plate  300  is adjusted preferentially by pivoting it about the rotational axis of the roll  320  in extending to the narrowest passage ES with respect to the radius r extending towards the point V. 
     FINE CLEANING 
     In the FIGS. 9,  10  and  11  each a possible realisation is shown of the cleaning function according to the FIG. 3 based on known devices already proposed for the fine cleaning stage. In all these Figures the reference sign  31  indicates the upper part of the chute (input chute), and the reference sign  32  indicates a feed device with a nip line, and the reference sign  33  indicates an opening roll (comp. FIG.  3 ). 
     The FIG. 9 is derived from the FIG. 1 of CH-C-464021. In the latter document a fine cleaning machine created in the  60   s  is described: A beater  33  provided with saw-tooth clothing  403  and supported in bearings in a housing  401  is supplied with coarsely opened fibre material from a chute  31  via a pair of condensing rolls  405  and a feed device  32  in the form of a pair of feed rolls  406 . Subsequently, as seen in the direction of rotation of the beater  33 , bars  407  are arranged equidistant and along about half the circumference of the beater and set closely to the circle swept by the beater (beater circle) under an angle of about 60°±10° with respect to the radius of the beater. The other bar surface extending also to the front edge encloses a small angle of about 0 to 2° with respect to the tangent of the beater. All the bars  407  forming the grid are arranged on a frame  412  which can be pivoted about a rotational axle  411  and which in its pivoted position, indicated with dash-dotted lines, makes room for the beater  33  to be moved out to the left hand side as shown in the FIG.  9  and to be replaced by another beater of a desired type, e.g. a beater provided with new or different clothing. On each grid bar  407  a guide plate is mounted providing a guide surface extending in tangential direction into close vicinity of the beater circle. This guide surface covers about half the distance between bars  407  to the next front edge. The position of each plate can be adjusted along its bar  407 . An increase in the distance of the plate from the beater circle results in more intense lifting of the fibre material off the clothing of the beater under the influence of centrifugal forces and thus results in more intense impacting on the next front edge of the following bar  407 . The impact imparted by this bar edge thus is directly influenced by the positioning of the guide plate and consequently also the degree of elimination of impurities is influenced without any changes being applied to the optimum position of the bars with respect to the beater circle once it has been established. 
     For application as an element of the present invention, the arrangement described in CH-C-464201 must be changed in such a manner that the beater at its side diametrically opposite the grid is provided with a cover  415  which joins the wall  416  of the lower chute part, an impacting edge being formed between the wall  416  and the cover  415 . This edge  417  can be formed by the wall portions  415  and  416 , or formed separately it can be mounted onto said wall portions. 
     The edge  417  serves for separating the fibre material from the roll  33  and for guiding it into the lower part of the chute. 
     In the FIG. 10 which is derived from EP-A-481302, a more modern embodiment according to the same principle is shown with a feed chute  31  delivering flock material into a converging gap formed between a blind drum  502  and a sieve drum  503  which sucks off air from the cotton material fed. This lap, from which the air has been bleeded, is guided via a take-off roll  504  into a further converging gap between a feed plate  322  and a feed roll  321 , and using this feed roll is supplied to an opening roll  33 . 
     This opening roll  33  takes over the fibres fed in by means of the teeth  508  provided on its surface (also called toothed clothing) in which process a layer of fibres guided by the teeth  508  is generated on its surface in the form of a fibre web. Owing to the relatively high circumferential speed of the opening roll and the resulting centrifugal force, this fibre web tends to be carried away from the teeth, and therefore the fibre layer before reaching the first grid bar module M 1 , depending on the distance between the feed roll  321  and a first grid bar module M 1 , is guided by means of a guide surface  541  arranged upstream (as seen in the direction D of rotation of the opening roll  33 ) of the first cleaning module M 1  and thus is prevented from being thrown off. The fibre layer subsequently is guided along a series of cleaning elements, or grid bar modules designated M 1 , M 2 . The grid bar modules M 1  are shown enlarged in the FIG.  10 A. The module M 1  consists of a grid bar  548  provided with flanges on its face side and with a separating edge  577  and a guide surface  576 , whereas the module M 2  consists of a clothing bar with a toothed clothing  549  (FIG.  10 ), provided with flanges  80  on its face side. The grid bars M 1 , M 2  are taken up in a grid element  509  as explained in the following. 
     After passing the last module M 1  the fibre layer placed on the teeth  508  of the opening roll  33  owing to the influence of the centrifugal force reaches an inlet  545  to the lower chute part. No guide elements being present at this inlet  545  radial outward movement of the fibres is not restricted. The tendency of the fibre material to move radially down (with respect to the roll  33 ) is assisted by an impact edge  547  similar to the impact edge  417  (FIG.  9 ). This edge can be formed by the wall portions  540  and  546  or, if formed separately, can be fixedly mounted thereon. The impurities eliminated drop into a collecting chamber  539 . 
     The grid  509  comprises two grid frames  509   a  (one of which only is visible in the FIG. 10) between which the grid bar modules M 1 , M 2  are mounted, in which arrangement the flanges of the grid bar modules rest against the inside surfaces of the grid frames. The grid frames  509   a  and thus the whole grid  509  are supported pivotably about a pivoting axis  510 . The grid can be designed adjustable also in the X and Y directions, movable e.g. by setting motors  521  and  522 . The grid frames  509   a  each are provided with a guide cam  511  presenting a guide surface  512  against which a guide  513  rests which is part of an adjusting mechanism  514 . 
     In the FIG. 10 a circle  533  marked with a dot represents a fixed connection of a pivoting lever  542  (designated only once in the FIG. 10) to a grid bar module M 1 , and at the same time represents a pivoting axle of the pivoting lever  542  and of the grid bar module, in which arrangement the grid bar module M 1  is pivoted about this pivoting axle  533  as the this pivoting lever  542  is pivoted. Fixation of the position of the module M 1  on the pivoting axle  533  is effected using a fixation screw  575  (FIG.  10 A). The other end of each pivoting lever  542  is pivotably linked by means of a link member  535  to a force transmitting lever  536  each. The last link member  535 , as seen in the direction of rotation of the opening roll  33 , pivotably links the preceding force transmitting lever  536  to a plunger  537  which in turn is connected with a stationary support member  539 . All force transmitting levers  536  being connected with each other via the link members  535 , the force transmitting levers  536  all simultaneously participate in the movement of the plunger  537  in such a manner that all grid bar modules, containing a fixed connection to the corresponding pivoting lever  542 , are pivoted. 
     In the FIG. 10 furthermore an empty circle designated  534  is shown, which indicates merely that the grid bar module M 2  at this point is not connected to the pivoting axle  533  and thus also is not connected to the pivoting lever  542 , and that the pivoting axles  533  and the pivoting levers  542  are required only for ensuring that the force transmission via all force transmission levers  536  functions properly. The fixedly mounted grid bar module M 2  is fastened to the grid frame  509   a  by means of a screw  543 . The screw  543  in this arrangement is guided in a guide slot provided in the grid frame  509   a  extending in radial direction with respect to the rotational axis of the opening roll  33  in such a manner that the position of these grid bar modules can be changed within this guide slot. 
     In the FIG. 10A two grid bar modules  579  are shown in an enlarged illustration, with a set angle γ1 and a free angle α1. The set angle γ1 is enclosed between a guide surface  574  and the beater circle  544  represented in the FIG. 10A as a straight line, whereas the free angle α1 is enclosed between the beater circle  544  and the guide surface  576  shown simplified as a straight line in the FIG.  10 A. The guide surface  574  serves as a guide for the trash loosened from the fibre web. From the FIG. 10A it furthermore can be seen that the pivoting axle  533  is located, as seen in the Figure, in the left hand corner of the grid bar module, i.e. on the side of the grid bar module containing the knife edge  575 . Owing to this arrangement the free angle α1 and the distance  131  are changed as the grid bar module is pivoted about the rotational axis of the pivoting axle  533 , whereas the distance A 1  remains virtually unchanged in such a manner that the distance A 1  as set by adjusting the position of the grid  509  is influenced negligibly merely by the pivoting movement mentioned. 
     In the FIG. 11 an embodiment is shown which is derived from the one shown in the FIG. 4.1 of EP-A-419415 with two separating blades and three guide elements in the place of grid bar modules. On an outermost circumference of an opening roll  33  provided with a toothed surface, on the so called beater circle, the fibre web to be cleaned is moved through the cleaning stage in the direction of the arrows indicated in bold lines. The lap, seen in the direction of transport, which already before reaching this cleaning stage has been exposed to the action of the centrifugal force, and in which therefore trash particles have been concentrated, first passes under a guide element  580 . The guide element protrudes into the transporting path and deflects the lap towards the inside, i.e. against the action of the centrifugal force and thus further reinforces the radial separation of the lap into impurities and fibres. After the guide element, seen in the direction of transport, a separating blade  581  follows. The lap passes under this separating blade and thereby is split into a fibre portion and a trash portion. Upon the separating blade, seen in the direction of transport, a second guide element  582  follows, then a second separating blade  583 , followed by a third guide element  584 . 
     In order to adjust the group of guide elements and separating blades for processing fibres of different origin or of blends, the following parameters can be set: 
     the distance p 1  between the separating blades  581  and  583  and the beater circle S, 
     the distance p 5  between the guide elements  580 ,  582  and  584  and the beater circle S, 
     the distance p 6  each between a guide element  580 , or  582  respectively, and a separating blade  583 , 
     In the FIG. 11 also three levers  42 ,  44 , and  46  are shown, using which the three distances mentioned can be set with the help of a motor drive. As the lever  584  is pivoted about an axis B as indicated in the schematic illustration with dash-dotted lines, the whole device moves away from the beater circle, i.e. p 7  and p 5  increase by the same amount. The positions of the lever  584  and of the separating blades  581  and  583  indicated represents the position closest to the beater circle. 
     As the lever  585  is pivoted about an axis C as indicated with dash-dotted lines in the Figure, the guide elements  580 ,  582  and  584  move in the direction of the lap transport without any change occurring in the radial position of these elements nor of the separating blades  581  and  583  relative to the beater circle S. 
     Expressed in other words, the guide elements  580 , and  582  respectively, move up to the separating blades  581 , and  583  respectively, in such a manner that the distance p 6  decreases. The position in which the lever  586 , the guide elements  580 ,  582  and  584 , and the separating blades  581  and  583  are shown in the Figure represents the situation in which the distance p 6  reaches its maximum. 
     Variant embodiments of the design example of the inventive apparatus shown in the FIG. 11 can differ in that: 
     the first guide element  580  is not provided, 
     after the third guide element  584  a third separating blade is installed, i.e. that the separating device consists of three pairs of a guide element and a separating blade each, 
     the complete cleaning stage comprises more than three pairs of a guide element and a separating blade each. 
     The opening roll  33  can be provided with a saw-tooth clothing, but it also could be designed as a needled roll. The stream of fibre material leaves the roll  33  in the same manner as described with reference to the embodiments according to the FIGS. 9 and 10 and drops into the lower chute part which substantially extends downward below the opening roll  33 . Along the circumference of the opening roll  33 , as seen in the direction of its rotation, between the chute part  31  and the lower chute part, elements are provided each performing one or the other of the following functions: 
     limit the fibre flow with respect to the opening roll, 
     separate material (especially impurities) from the material flow, 
     enhance the opening effect, whereby openings between these elements permit elimination of impurities. 
     The embodiments shown in the FIGS. 9 through 11 all function according to the same principle that the fibre stream moves along a curved path while material from the (radially) outer layers are separated and eliminated. The degree of opening can be adapted to the cleaning function in such a manner that the impurities can “migrate” radially towards the outside in such a manner that impurities rather than good fibres tend to be separated. 
     After the fibre stream has left these separating elements, it can be conveyed directly into the lower chute part. Further processing (e.g. using a sieve drum) and transporting are not required—such measures would result in nep formation (due to the enhanced degree of opening effected by the fine cleaning stage). 
     In a plant according to the present invention dedusting can be effected at any point where transporting air is eliminated from the system, e.g. at the intake of the coarse cleaner  4  as described with reference to the FIG. 4, but also in the upper chute part  31  (compare sieve drum  405 , FIG. 9, or  503  respectively, FIG.  10 ). Provision of a dedusting stage after the opening roll  33  thus it not required, i.e. the fibre stream can be conveyed, as mentioned before, from the opening roll  33  directly to the lower chute part. This statement also applies to the application of the blowroom plant in connection with a spinning method (e.g. rotor spinning) particularly susceptible to dust, and to fine trash particles respectively. It also is known that a spinning preparation plant can be provided with a dedusting machine (compare U.S. Pat. No. 4,637,096)—an arrangement of that type can be applied also in combination with present invention described herein. 
     In the preferred embodiment, the cleaning device in the feed chute comprises one single opening roll  33 . Cleaning devices are known, however, (e.g. DE 4039773) which contain a “roll series”, i.e. a plurality of rolls provided with clothing each, in which arrangement each roll is provided with at least one element which eliminates impurities from the fibre stream. “Multiple roll cleaners” of such type also can be applied in a “cleaner chute” according to the present invention, even if they do not promise substantial advantages compared to a single roll arrangement according to the preferred solution. 
     FIG. 12 shows schematically a feed chute  8  with a cleaning module RM according to this invention, e.g. according to one of the FIGS. 9,  10  and  11 . The lower part  34  of the chute forms a fibre batt W from which fibres are fed to a licker-in V by means of a feed roll SW and a feed shoe SM. More than one licker-in can be provided, as indicated by the circles V 2  and V 3  in dotted lines. Reference VM indicates a drive motor provided for the licker-in V (and possibly also for the additional lickers-in V 2 , V 3 ). Reference VA indicates a trash eliminating element in the licker-in module and the box VAS represents schematically an operating means for adjusting the element VA relative to the licker-in V. 
     The licker-in V together with its trash eliminating element VA forms an opening and cleaning device (a cleaning unit). Various units are known to be capable of fulfilling the requirements, see for example DE 4039773 or EP 618318. Both the cleaning module RM in chute  8  and the cleaning unit in the card infeed can now be connected with the card control  120  (see also FIG.  1 ), so that the can be adjusted together or independently of each other. The adjustment can be effected for example in co accordance with EP-B-452676 (or its equivalent U.S. Pat. No. 5,181,295). 
     The invention according to the present invention can also be combined with the invention according to the U.S. patent application claiming priority from Swiss patent applications 934/96 and 935/96, each dated Apr. 9, 1996 (inventors Jürg Faas and Christian Sauter). The content of that U.S. application is therefore incorporated in the present application by reference. 
     It should be understood by those skilled in the art that various modifications and variations can be made in the invention without departing from the scope and spirit of the invention. Ilt is intended that the present invention cover such modifications and variations as come within the scope of the claims and their equivalents.