EP0799915B2 - Method and apparatus for the sliver regulation in a carding machine - Google Patents

Description

The invention relates to a method and a device for belt regulation for a card, that is, a machine having a provided with a set drum (also called Tambour), wherein the clothing of the drum with distributed around the circumference of the drum working elements (eg Wanderdekkel ) works together to achieve a carding effect. Such a machine also includes a supply of material, e.g. with a breeze - also called licker-in - and a speed-controllable feed roller and a so-called outlet, which comprises a pick-up, which takes over a fiber fleece from the drum and passes it on.

The invention relates to a method and apparatus for controlling a card during a so-called "transient" phase, i. during a period where the discharge speed changes. Examples of such phases are the run-up phase during start-up, the braking phase when stopping and the corresponding acceleration phases (positive and negative) during can change.

State of the art

A general device for controlling, among other things, the speeds of the feed roller and the pickup is described in US-A-4530134. The document discloses a device that monitors important operating parameters of a card and continuously controls and regulates speeds, for example of feed roller and pickup, based on a fixed program. Such a possible regulation is described by document FR-A-2515695. Here a PI controller is described in which the control time constant of the controller is set as a function of the take-off speed or the feed speed.

The conventional procedure when starting or braking will be described below with reference to the figures. This procedure serves as an example of a "transient" phase, the other transient phases proceed accordingly.

1. 1. Es war nicht möglich, diesen instabilen Faserfluss einer Regulierung zu unterwerfen, und
2. 2. die zeitlichen Veränderungen im Faserfluss könnten zu einem Bandbruch führen, was das erneute Einfädeln (mit anschliessender transienter Phase) erforderte.

However, this process, which is still conventional today, is known to lead to an "unstable" fiber flow, in particular in the discharge part of the card. This has so far led to two unfavorable effects:

1. 1. It was not possible to subject this unstable fiber flow to regulation, and
2. 2. The temporal changes in the fiber flow could lead to a band break, which required the re-threading (with subsequent transient phase).

The basic object of the invention is to improve the controlled process during a transient phase such that tape breaks can be avoided.

A secondary object (the preferred solution) is to improve the process so that regulation can also be used during the transient phase.

The solution of the basic task is specified in claim 1.

Fig. 1

schematisch eine bekannte Karde mit Sensoren für die Bandregulierung

Fig. 2

schematisch eine Bandregulierung

Fig. 3

schematisch ein Messorgan am Einlauf (an der Speisewalze)

Fig. 4

eine seitliche Ansicht des aus Stufenwalzen gebildeten Messorgans am Auslauf

Fig. 5

Querschnitt eines Messorgans am Auslauf

Fig. 6

schematisch den Auslauf der Karde nach Fig. 1 mit einem Sensor für die Auslaufgeschwindigkeit des Kardenbandes

Fig. 7

drei Diagramme, wobei das Diagramm (i) den Stand der Technik und die Diagramme (ii) und (iii) zwei Ausführungen der Erfindung darstellen.

Fig. 8

ein Zeit/Geschwindigkeitsdiagramm für den Anlaufvorgang verschiedener Walzen der Karde nach Fig. 1

Fig. 9

eine schematische Darstellung der Wirkung der Totzeit in einer Karde nach Fig. 1

Fig.10

ein Zeitdiagramm zur Erklärung des Verlaufes vom Bandgewicht beim Hochlaufen aus dem bzw. beim Tieflaufen in den Kriechgang

Fig.11

ein erstes Arbeitsprinzip nach der Erfindung

Fig.12

ein weiteres Arbeitsprinzip nach der Erfindung

The invention will be explained in more detail with reference to embodiments shown in the drawings. Showing:

Fig. 1

schematically a known card with sensors for belt regulation

Fig. 2

schematically a belt regulation

Fig. 3

schematically a measuring element at the inlet (at the feed roller)

Fig. 4

a lateral view of the measuring element formed by step rollers at the outlet

Fig. 5

Cross section of a measuring device at the outlet

Fig. 6

schematically the outlet of the card of FIG. 1 with a sensor for the discharge speed of the card sliver

Fig. 7

three diagrams, wherein the diagram (i) represent the prior art and the diagrams (ii) and (iii) represent two embodiments of the invention.

Fig. 8

a time / speed diagram for the starting operation of various rollers of the card of FIG. 1

Fig. 9

a schematic representation of the effect of dead time in a card according to Fig. 1st

Figure 10

a time chart to explain the course of the band weight when running up from the or during deep running in the crawlspace

Figure 11

a first working principle of the invention

Figure 12

another working principle of the invention

In Fig. 1 is a known Wanderdekkelkarde, eg the card C50 of the Applicant, shown schematically. The fiber material is fed in the form of dissolved and purified flakes in the hopper 20, taken from a Briseur 32 (Fig. 3) (also called licker) as Wattenvorlage, a Tambour (or drum) 40 passed and by the cooperation of the drum with one Hiking lid set 52 dissolved and cleaned. The covers of the traveling lid set 52 are guided by a suitable drive system of the revolving flat unit via deflection rollers along a closed path (in the same direction or in opposite directions to the direction of rotation of the spool). Fibers from the web located on the spool 40 are removed by a pickup 70 and formed into a sliver 90 in a run-out section 80 consisting of different rolls. This card sliver 90 is deposited by a sliver tray (not shown) in a transport can in cycloid turns.

That from the card to the next processing stage, e.g. a band supplied should be possible evenly. Therefore, a band regulation is required. This will be explained below with reference to Figures 2 to 6.

Figure 2 shows schematically a computer 4 with input and output signals. Signals are input from two sensors B5 and B6, which will be explained in more detail below, as well as signals which include, among other things, the speed of the card sliver at the exit (Va) and various data, e.g. Set targets for tape weight. The basic principle of conventional belt regulation is based on two measures, namely a "long-term" regulation and a regulation with "short-term addition" at the inlet, where disturbances at the time of feeding are to be compensated. According to this invention, a third measure is taken, but will be explained in more detail after an explanation of the conventional system.

As can be seen from FIG. 1, a sensor B5 which is arranged on a feed trough 6B detects the unevenness of the weight of the incoming wadding pattern. These correspond to the deflections of the pivotally mounted feed trough with respect to the feed roller 6A (see also FIG. 3). The sensor B5, as shown in Fig. 1, the computer 4 provides a cross-sectional signal dependent 6. The electronics influenced by the signal 7 via a control unit 8, the drive motor (not shown) of the feed roller 6A and thus the speed of the feed roller.

The further sensor B6 shown in FIG. 1 scans the outgoing card sliver and delivers an electrical signal 2 dependent on the band weight to the regulation (the computer) 4. Through a funnel 13, see FIG. 5, the card sliver leaving the sliver draws off the clamping point of two step rollers 11, 12 out. The lower roller 12 is driven, the upper roller 11 is vertically movable via a spring-loaded lever. This roller is driven by the outgoing card sliver and the stroke of the roller 11 (shown from the distance L between the axes of the two rollers in Fig. 4), corresponds to the thickness of the card sliver. After a band break, the new band must be threaded through the funnel 13 between the rollers 11, 12 and forwarded to the tape tray again. This is done at a relatively low, constant delivery speed (in the "crawl").

An actual value is read in as input signal 2 to the computer 4 independently of the exit speed and compared with the previously entered the electronics band weight target value, cf. also Fig.2. The speed of the feed roller is influenced accordingly by the control in order to keep the weight of the strip in the outlet constant.

The sensor B5 provides readings used by the computer 4 for the "short term addition", while the sensor B6 provides readings used by the computer 4 to realize "long term regulation". In the context of long-term regulation, the "dead time" of the controlled system must be taken into account, i. the time that elapses after a change is made to the feed roller until the corresponding effect appears at the measuring point (at sensor B6). This dead time is so long in the card that the long-term regulation is used only for "number keeping" (to avoid drift).

The dead time from the feed roller 6A to the measuring point B6 is only of secondary importance in connection with this invention. However, there is a corresponding (somewhat shorter but nevertheless significant) dead time from the feed roller 6A to the transition point from the drum 40 to the pickup 70. The latter dead time is of central importance in connection with the invention. It will be described in the description of FIGS. 8 and 9 used.

The outward speed is controlled by a control loop as the setpoint changes (i.e., during a transient phase, e.g., during run-up). This serves to adjust the speed of the discharge motor 50 in Fig. 6 accordingly. The initiator (Figure 1) on the step rollers 11,12 provides the computer 4 pulses. These are converted into the speed at the outlet (Vauslauf). This speed is compared with a predetermined discharge speed, see Fig. 2. The resulting control value 60 is given to the frequency converter 30 in Figure 6.

The known belt regulation works only after the operating state has been reached, provided that this state requires a discharge speed greater than 50 m / min. Below 50 m / min, as well as during startup and deceleration, is automatically switched to the unregulated operation, i. the short-term supplement and the long-term regulation are inactive. At this point, the invention begins. It relates to a belt regulation for use during the run-up and down-stroke phases of the exit speed. The invention will be explained below with reference to the diagrams of FIGS. 7, 8 and 9.

In all three diagrams of Fig. 7, the curve of the ratio of the rotational speed of the pickup 32 relative to the feed roller 6A is shown, and (as an example) when starting the card from standstill.

The first two sections of the plot are the same in all diagrams (i), (ii) and (iii), i. at the first acceleration (section a) to the end of the creep phase (section b), where threading takes place at constant (low) exit speed. In all three cases, a constant ratio between the speed of the feed roller and that of the pickup has been chosen. In the prior art (Diagram i), the same ratio is maintained during further acceleration from the crawl to the operating speed (Section c).

In Fig. 7 (ii), for the time being, in section c, there is a "jump-like" change (with a "kink") in said ratio, e.g. because the run-up of the pickup is delayed compared to the run-up of the feed roller. In FIG. 7 (iii), in section c, there is no sudden, but a steady change in the ratio, which has a tendency to drop for the time being (slower start-up of the pickup when simultaneously triggering the run-up of both rolls).

It should be noted that in all three diagrams, the said ratio is the same when operating speed is reached, since it represents an important technology parameter (the basic distortion of the machine). In the diagrams (ii) and (iii) the sections (c) can not be linear, because after the decrease at the beginning of this section the final target Z can only be achieved by a bent or a curved course.

Fig. 8 is a timing chart for the process of increasing the speeds of a card in the so-called pass-through phase, e.g. in the phase where the different rollers have not yet reached their operating speed after switching on the machine. The curves S and A show the increasing speed of the feed roller 6A and the pickup 70, curves T and V the increasing speed of the drum 40 and the licker-in 32.

The above-mentioned passage phase is e.g. on the abscissa between the time values T2 and T3 for the feed roller and the customer can be seen. Also a braking process represents a passage phase, such. For example, on the above-mentioned abscissa between time values T4 and Te for the drum and the licker-in.

Further, Fig. 8 shows the order in which the individual rolls of a card are usually turned on. First, the drum 40 (drum) is turned on, see curve T, then simultaneously the pickup 70 and the feed roller 6A, see curves A and S. From the earlier patent application of the applicant EP-A-701 012 it is known in the card a separate Asynchromotor for the feed roller 6A, another for the drum 40 (from this also Briseur and revolving lid are driven) and a separate Asynchromotor for the outlet 80 (inclusive customer 70) to provide. Furthermore, it can also be seen from the diagram of FIG. 8 that at the time T2 on the abscissa, in which the feed roller and pickup start, the drum and the licker-in are already at (or at least in the vicinity of) the operating speed. Moreover, it can be seen from the comparison of curves A and S that the rate of rise of the pickup is greater than that of the feed roll before the two rolls have reached their respective stable operating speeds. However, it has a linear (proportional) relationship between the speed of the feed roller and that of the pickup. Further, in the curves S and A, a short time interval (the creep pause) TA, TB can be seen, in which the speeds of the pickup and the feed roller remain constant. This time interval is needed in a through phase for threading, i. the insertion of the card sliver between the trigger and the funnel 13 (Figure 6) after a band break.

As will now be explained with reference to FIGS. 9 and 10, the dead time between the feed roller 6A and the pickup 70 has the result that in a card according to FIG. 1 during the startup phase, also called the acceleration phase, the band quality is poor, in particular The tape is much thinner than necessary, so there is a risk of tape breakage. Fig. 9 shows schematically and simplified the effect of the dead time in the formation of a card sliver from a template during a transient phase. With I, II and III, the sections of fiber flow are shown on the feed roller (6A), the licker-in and the drum (32, 40) and the spout (80). In order to simplify the illustration and explanation, the effect of warpage (i.e., roll-to-roll speed differences) in Fig. 9 has been neglected. The effects shown are only those of the speed changes during the run-up.

The feed roller applies to the licker-in and spool a non-woven fabric (from a cotton pad) having a thickness D at any time during start-up, eg, at time Tw (FIG. 8). 9 now represents a "snapshot" of the fiber flow through the card at the same time Tw. Because of the already mentioned dead time Tz from the feed roller 6A to the transition between the drum 40 and the pickup 70 at the time Tw corresponds to the thickness of the fiber layer the transition point to the customer not D but D1 (D ₁ <D). This lower thickness corresponds to the nonwoven, which was delivered from the feed roller at an earlier time Tw-Tz to the licker-in 32, but only at time Tw at the point of transition to the taker 70 is effective. At time Tw-Tz, the pickup (as shown in Figure 8) ran at such a speed that it could pick up and pass a layer of fiber corresponding to the thickness D1 from the drum. At time Tw, he is already running at a higher speed. The already fast turning Buyer "tries" to take more material than it is provided. This forms at the outlet of a thin band whose weight is below the intended weight, see the course of the curve K2 in Fig. 10. A similar (but reversed) problem arises in the deceleration phase, see. right side of the diagram in Fig.10, where a too thick card sliver is produced, as will be explained in more detail below.

A significant reason for the weakening of the band is therefore in the delay time (called control technology "dead time"), which (on average) needs a fiber to get from the feed roller to the customer.

FIG. 10 shows a ramp-up and -brake curve K1 for the speed of the belt and a curve K2 for the belt thickness. The left-hand ordinate indicates the speed VA of the belt, on the right-hand ordinate the belt weight in ktex, on the abscissa the time of the belt Start-up procedure or the braking operation. Furthermore, the setpoint or set value for the strip thickness is entered. As can be seen, this results for the run-up, i. from an outfeed speed of the belt in the range of 15 m / s up to the operating speed, an undesired band formation, where a below-target band is produced. The right-hand side of the diagram shows that an undesired (too thick) belt is also produced during the braking process. These problems should u. a. be eliminated with the present invention.

Two variants of the solution are proposed, which are explained with reference to FIGS. 11 and 12. In these figures, only the solutions for the run-up are shown, and these solutions can be adapted to the low-speed.

The first embodiment provides a mutual adjustment of the speeds of the rollers at the inlet and outlet. In other words, the ramp-up of the speed of the pickup 70 in the outlet is shifted from the run-up of the speed of the feed roller 6A in the inlet such that the pickup 70 starts to run up at a later time. Thus, the feed roller 6A will be able to deliver more material to the drum 40 in the critical period of run-up. It is thereby prevented that at any time when removing a web from the Trommeloberfäche thereon is a layer of material with a smaller thickness than that which corresponds to the effective effective speed of the pickup at the same time. Rather, there will be a layer of material of sufficient thickness so that no thinned web is transferred to the customer. FIG. 10 shows the delay with curves VE and VA. Curve VE shows the increase in speed at the inlet, curve VA the increase in speed at the outlet. The speed VE begins to increase at the time TI until it reaches its intended size (during normal operation of the machine) at the time TIII. On the other hand, the velocity VA begins to increase at a later time TII and thus attains its intended size at a later time TIV. This results in a delay Tl, Tll on the abscissa t. As previously explained in explanation of Fig. 8, the adjustment of the speeds of the two rolls starts first at time TI (not at time T0), since the time period T0-TI is required for threading the flock in the hopper area.

The process described above is carried out by the computer 4, as shown in FIGS. 1 and 2, at the time TI a signal 7 to the drive motor of the feed roller and at a later time TII a signal 60 to the drive motor 50 of the pickup goes. In order to avoid repetition, reference is made to the band regulations described in more detail in the description of FIGS. 1 to 5. This procedure already described is programmed in advance in the computer 4 and supplied to the user with a software package.

A further embodiment (FIG. 12) of the invention is based on the fact that in the critical phase the speed (VE) of the feed roller 6A is accelerated more strongly than the VA of the pickup 70. This process is explained in more detail with reference to FIG. 12. Unlike the process shown in Fig. 11, the influence of the speed of the two rollers at the inlet and outlet begins at the same time TG. While the speed of the feed roller is rising sharply at this time, on the other hand, the acceleration of the pickup in the time interval TG-TG1 becomes relatively slow, i.e., slower. It only starts to rise sharply at time TG1. Furthermore, it can also be seen from this diagram that the regulation of the feed roller is carried out at an outfeed speed of the belt of about 0.15 m / min and that of the pickup at a speed in the range of about 15 m / min. This process is carried out in such a way that go from the computer 4 at the same time TG signals 7 and 60 to the drive motors of the two rolls. The slopes of the two driving curves are preprogrammed.

As already indicated, the processes according to FIGS. 11 and 12 can also be adapted to the deceleration phase. According to a solution according to FIG. 11, the deceleration of the feed roll speed required for the deceleration is triggered at an earlier point in time than the corresponding step for the outlet 80 takes place. According to a solution according to Figure 12, the computer 4 triggers the deceleration of the pickup 70 (the spout 80) at the time when the deceleration of the feed roller begins, the slope of the "braking curve" for the feed roller is higher than the slope of the brake curve for the Spout is selected.

Another application of the invention will now be explained.

The rollers of the outlet 80 are coordinated so that the at the transition from the Drum 40 to 70 formed fiber fleece at the transition to the subsequent roll (take-off roll) practically completely removed from the customer and then forwarded as a nonwoven until this web is folded into a ribbon 90. The rollers of the inlet are matched to one another in a corresponding manner, so that the fiber fleece drawn from the feed roll 6A from the original wadding is passed on as a fleece at each transition until the fibers reach the drum 40.

• der Dicke des Faserbelages auf der Trommel 40, und
• der Umfangsgeschwindigkeit des Abnehmers 70 im Verhältnis zur Umfangsgeschwindigkeit der Trommel 40.

The process at the transition point drum / customer runs but different. At this point, only a portion of the fibers passes to the pickup 70, the others continue with the drum (see EP Patent Application No. 97810074.1 dated 12.2.97). The basis for the band weight Faserbelag on the customer depends on many factors, of which only two are of importance, namely

• the thickness of the fiber layer on the drum 40, and
• the peripheral speed of the pickup 70 in relation to the peripheral speed of the drum 40th

The thicker the fiber coating on the drum, the thicker the fiber coating on the pickup (given otherwise operating parameters). The lower the ratio of the peripheral speed of the pickup to the peripheral speed of the drum (given otherwise operating parameters), the thicker the fiber coating on the pickup.

A predetermined tape weight requires a corresponding web thickness on the picker. In order to ensure this, the two mentioned parameters must be matched to one another, as was explained with reference to FIGS. 9 and 10 for the case of run-up. In that case, the over-fast taker has distorted and "thinned" the "few" fibers provided to him, which can lead to a tear. A "too slow" turning down causes a congestion in the fiber flow, which can lead to a blockage.

Assuming now, the coasting speed must first be lowered from the value for the normal operation to a lower value at a predetermined time Tk, and then increased again to the operation speed, e.g. to carry out a can change. At a certain point in time, the setpoint for the exit velocity is reduced according to a predetermined "deceleration ramp", causing an immediate deceleration of the doffer 70. However, the drum 40 continues to run at an undiminished speed (peripheral speed). In addition, the drum 40 still supplies a fiber layer to the pickup 70 fed from the feeding roller 6A at a timing (Tk-Tz, see Fig. 8). The speed of the feed roller is of course also discontinued at the time Tk. However, this change can cause nothing at the transition to the customer at the time because of the dead time.

The result is a significant thickening of the fiber layer on the pickup, resulting in a noticeable increase in belt weight.

If the long-term regulation remains switched on and the change in the weight of the band is detected, it will further slow down the speed of the feed roller to reduce the supply of fiber to the drum (causing a dilution of the fiber coating on the drum). Because of the already mentioned dead time, the influence of the reduced supply only appears with a delay on the drum surface - meanwhile, however, the speed of the pickup according to the braking ramp has decreased even further. The weight of the band is still too high (despite the use of regulation).

At the end of the can change process, the discharge speed is increased again, to bring the card back to the target production (operating state) again. The ratio of the peripheral speed of the pickup as compared to the peripheral speed of the drum is increased, the pickup takes a lower proportion of the fiber web from the drum, which pulp is thinned from the mentioned reasons to the operating condition. The thickness of the fiber coating on the customer decreases again. The long-term control can not effectively counteract this effect because of the dead time. In addition, the control algorithm of the long-term controller (realized in the software or programming of the computer 4) normally contains an integral part. So far, fiber flow changes during a transient phase have interacted with this integral part of the algorithm in such a way that the occurring error is increased for the time being before it can subsequently be corrected. The long-term control has thus far been switched off during run-up and slow-down phases (i.e., during transient phases), since it does not correct the variations in the band weight, but rather makes compensation more difficult.

• die Faserzufuhr durch die Drehzahl der Speisewalze beeinflusst werden kann,
• die "Totzeit" (die Zeitverzögerung zwischen einer Drehzahländerung und der Speisewalze und dem entsprechenden Einfluss an der Übergabestelle Tambour/Abnehmer) feststellbar ist, und
• der Zeitpunkt einer Sollwertänderung für den Abnehmer in der Computersteuerung "vorbekannt" (vorprogrammiert) ist.

The adverse effects arise in a conventional change in the discharge speed, because such a change immediately leads to a change in the ratio between the peripheral speeds of the drum and the pickup, resulting in a change in the band weight given otherwise operating parameters. However, it is not possible to change the other relevant parameters "immediately". According to this invention, the fiber supply to the drum is now to be "pre-controlled" to reduce the undesirable effects. This can be accomplished because:

• the fiber supply by the speed of the feed roller can be influenced
• the "dead time" (the time delay between a change in speed and the feed roller and the corresponding influence at the transfer point Tambour / customer) is detectable, and
• the time of a setpoint change for the customer in the computer control is "known" (preprogrammed).

By the precontrol of the fiber supply, the thickness of the fiber layer on the drum is changed in time so that the subsequent influence of a (transient) change of the discharge speed on the band weight (on the removal of fibers from the drum) is at least partially compensated. The exact feedforward characteristic must be determined (empirically) depending on the details of the card design, i. depending on the effective dead time feed roller ⇒ delivery point as well as on the effective change of the "collective power" of the pickup at a given change in its speed. Since these factors themselves may depend on other operating parameters (eg on the effective number of operations of the drum) (see for example DE-C-3143285), at most additional effects in the programming must be taken into account, whereby the complexity of the system should preferably not be unnecessarily increased ( only those parameters should be taken into account which exert a noticeable influence).

By means of this precontrol, it is readily possible to improve the fiber flow during the transient phases in such a way that strip breaks can be avoided. However, the invention also makes possible a further improvement - the fiber flow can be stabilized in such a way that the long-term regulation no longer causes a disturbing effect even in the case of a transient phase, but rather improves the band uniformity. The computer 4 can therefore be programmed so that the long-term regulation is already switched on during startup (after completion of the creeper) and remains switched on when braking to a corresponding discharge speed. The long-term regulation remains active during the can change.

An improvement in band uniformity may e.g. be achieved by the fact that the long-term regulation can be switched on from a discharge speed of about 35 m / min.

The present invention is by no means limited to the embodiments mentioned above only by way of example. In particular, it is not limited to the run-up from the crawlspace, the deceleration to a standstill or the can change. Basically, the controller (computer) 41 may be programmed to detect an imminent transient phase (e.g., via a change in the ramp rate setpoint) and initiate a corresponding feedforward control of the fiber flow by controlling the feed roll speed.

Claims (12)

1. A method for controlling a card comprising a doffer and a feed roll each having a controlled drive, characterised in that the speeds of the feed roll and the doffer are controlled by means of a pre-programmed procedure on a computer, whereby a nonlinear profile of the relationship between the speed of the feed roll and that of the doffer is effected during at least one transient phase (c) and in this way, the dead time, i.e., the time delay between a change in speed of the feed roll and the corresponding influence on the transfer point from the cylinder to the doffer is taken into account with regard to the avoidance of sliver breaks, wherein the transient phase (c) comprises:

   a. a run-up phase from a creep feed after threading in the slubbing during start-up of the card or

   b. low running and the subsequent run-up, in particular during a can change.
2. A card comprising a doffer (70), a feed roll (6A), a drive each for the doffer and the feed roll and a controller (4) for the two drives which controls the speeds of the feed roll and the doffer by means of a pre-programmed procedure on a computer in such a manner that said controller brings about a nonlinear profile of the relationship between the speed of the feed roll (6A) and that of the doffer (70) during at least one transient phase (c) and in this way, the dead time, i.e., the time delay between a change in speed of the feed roll and the corresponding influence on the transfer point from the cylinder to the doffer is taken into account with regard to the avoidance of sliver breaks, wherein the transient phase (c) comprises:

   a. a run-up phase from a creep feed after threading in the slubbing during start-up of the card or

   b. low running and the subsequent run-up, in particular during a can change.
3. The card according to claim 2, characterised in that the nonlinear profile effects a pre-control of the fibre flow with regard to a preceding change in the delivery speed during the transient phase.
4. The card according to one of claims 2 to 3, characterised in that a sensor (B6) is provided for the sliver weight and the fibre supply is controlled by a regulator depending on the measured values of this sensor.
5. The card according to claim 4, characterised in that the regulator operates according to a regulating algorithm which comprises an integral fraction.
6. The card according to claim 4 or 5, characterised in that the regulator is inactivated by the controller (4) at delivery speeds below a predefined limit.
7. The card according to claim 6, characterised in that the regulator is activated during a transient phase.
8. The method according to claim 1, characterised in that the increase in the speed of the doffer is delayed with respect to the feed roller.
9. The method according to claim 8, characterised in that the delay is effected from the creep speed, e.g. at a sliver delivery speed in the range of 15 m/min.
10. The card according to claim 4, characterised in that tuned signals are issued to the drive motor of the feed roller (6A) and the doffer (AU) from the computer (4).
11. The card according to claim 10, characterised in that a signal for changing the speed of the feed roll (6A) is only issued to the feed roll drive at time TI and a signal is then issued to the doffer (AU) at time TII.
12. The card according to claim 10, characterised in that a signal for influencing the speed of the feed roll (6A) and the doffer (AU) is issued at the same time, wherein the speed of the feed roll (6A) is varied substantially at this time and the strong acceleration or deceleration of the doffer is delayed by the time interval TG-TG1.

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