Combing machine and method for operating a combing machine

Abstract

The invention relates to a combing machine having a plurality of combing heads (20), wherein at least one lap strip (4) is unwound from a lap roll (1) at each combing head (20) and is fed to a feed cylinder (7) and a nipper assembly (5), the noils are combed out and removed by suction from the lap strip (4) by means of a fixed and cylindrical comb (9, 8), and the fiber web created is formed by means of a trumpet (15) into a fiber strip which is drawn with the other fiber strips from the other combing heads to form a single fiber strip. The invention is characterized in that a first pair of draw-off rollers (10, 12) and a second pair of draw-off rollers (11, 13) are arranged downstream of the nipper assembly (5) and carry out a pilgrim step movement, the rotational movement thereof being changeable in size and time profile by means of at least one drive independently from the movement of the nipper assembly so that a conveying path of the formed fiber web (14) is variably adjustable in the forward and reverse conveyance. The invention also relates to a method for operating a combing machine.

Description

[0001] The present invention relates to a combing machine and a method for operating a combing machine according to the preamble of independent claims 1 and 10.

[0002] Combing machines are used to comb unwanted short fibers, nits, and trash particles from cotton wool or fiber ribbons using multiple combing heads. The resulting combed fiber webs are then fed to a common drawing unit. There, the fiber webs are merged and drawn to create a single fiber ribbon with predetermined properties, which is typically deposited in a can. The cotton wool or fiber ribbons are fed to a reciprocating gripper by a feed roller. In the retracted position, the gripper is closed and holds a protruding end section of the cotton wool in the form of a fiber beard. This protruding fiber beard is then combed out by the round comb located below the gripper.The tongs are then moved to a forward, open position, whereby the tear-off rollers, through a backward rotation, convey a previously combed-out fiber strand with its rear end towards the front end of the cotton held by the tongs. The fiber strand combed out by the round comb lies on this rear end and is drawn together into the clamping point of the tear-off rollers, as the tear-off rollers reverse their direction of rotation. During this rotation, in which the angle of rotation is approximately twice that of the preceding reverse rotation, the fiber strand is torn from the cotton in the tong assembly. The rear end of the torn fiber strand is then pulled through the fixed comb.

[0003] This process creates individual, non-connected fiber strands of specific lengths, dependent on the fiber stack. During soldering, two fiber strands are overlapped by at least the nearest pair of tear-off rollers to form a continuous fiber web. Each fiber web formed in this way is then used to create a fiber ribbon. To prevent the combed and soldered nonwoven fabric from tearing, as it undergoes a continuously repeated stepping motion due to the tear-off rollers, a material reserve is created in a nonwoven basin. This basin acts as a stabilizing zone for the nonwoven fabric.

[0004] The fiber strips run individually towards the tape table. They are then deflected by deflection elements, typically by 90°, and guided across the tape table to the drawing unit, where they are stretched to the desired strip number. Depending on the positioning of the deflection elements, the solder joints are further adjusted when the strips are joined.

[0005] One cycle of a back-and-forth rotation of the tear-off rollers of the respective comb head per combing cycle is a pilgrimage step, due to which the tear-off rollers transport the fiber material out of the comb head by a certain conveying distance per combing cycle.

[0006] The conveying distance, or the effective removal of the combed fiber material from the respective combing head of the combing machine per combing cycle, has been a constant, non-adjustable value for all combing machines from all manufacturers for decades, amounting to approximately 25 mm per combing cycle. This 25 mm corresponds to the average staple length of the most common cotton varieties. The conveying distance is determined by the difference between the rotation angles of the tear-off rollers in the transport or conveying direction of the soldered fiber web from the combing head and against this conveying direction. This results from a tear-off curve, i.e., the movement pattern of the tear-off rollers per combing cycle. Therefore, the conveying distance is the same or similar for all known combing machines and is not adjustable.

[0007] The conveying path is typically implemented by a complex gearbox that generates the stepping motion of the stripping rollers. This ensures that the same change in the angle of rotation, or the same path along the circumference of the stripping roller, is always executed during a combing cycle. The only possible modification to the stripping roller movement, and thus the only possible influence on the combing process in the area of ​​the stripping roller movement, is to shift the soldering point and thus shift the constant stripping roller movement in parallel with the other elements of the combing head.

[0008] The soldering point is the moment when a fiber strand is attached to the preceding one. To adjust the soldering point, the movement of the first pair of tear-off rollers must be shifted relative to the gripper movement when the gripper movement reaches its forward dead center, i.e., when the distance between the lower gripper plate and the clamping point of the first pair of tear-off rollers is minimal (écartement). This soldering point shift is adjusted, for example, to the material to create a homogeneous fiber mass. The fleece of the combing machine thus consists of small, overlapping individual fiber strands, similar to roof tiles, and is therefore periodically uneven. Depending on the combing speed, the overlap length of the individual fiber strands is determined by the combing action.

[0009] The solder joints cause irregularities and represent a periodic defect, recognizable, for example, in the CV values ​​of the combed fiber and in the spectrogram as chimney-like peaks at approximately 30–75 cm. To compensate for these irregularities, it is known to achieve optimal overlap of the fiber strands by adjusting the combing machine. These adjustments include coordinating the break-off point and the point at which the fiber strand protruding from the gripper reaches the clamping lines of the break-off rollers (soldering point shift of the break-off roller movement). By adjusting the timing of the gripper movement, the fiber strands are overlapped more or less closely.

[0010] Furthermore, the fleece can be peeled off eccentrically to compensate for unevenness in the combed surface. This causes the solder lines to align diagonally, leading to a partial compensation of the periodic error.

[0011] In addition to these qualitative effects, the soldered nonwoven fabric is very sensitive due to the solder joints. Depending on the fiber material and the combing cycles, more or less pronounced thin and thick patches develop along the length of the nonwoven. Furthermore, defects can occur in the nonwoven, even resulting in holes. Even with optimally selected settings on the combing machine (soldering timing, pressure of the tear-off rollers, etc.), the described phenomena in the nonwoven fabric cannot always be avoided, and some quality losses remain that must be accepted, or the production output or the combing cycles on the combing machine must be reduced.

[0012] Often, holes or weak points in the nonwoven fabric require very complex measures to address, especially if production cannot or should not be reduced. This can be achieved, for example, by feeding significantly heavier slivers to the combing machine and, in some cases, increasing the feed rate at the combing machine to produce a heavier, more stable nonwoven. This necessitates changes in the spinning line well before the combing machine. This might involve, for instance, producing coarser draft slivers and a coarser sliver feed at the winding machine to enable the production of significantly coarser slivers within the permissible distortion limits of the winding machine's drafting unit.

[0013] EP 0374723 A2 proposes replacing the inert gearbox for the piling step of the stripping rollers with electric motors. The drive impulses of the electric motors are synchronized with the rotation of the circular comb roller. This automatically synchronizes the piling step movement with the gripper unit.

[0014] WO 91 / 11548 A1 describes the geared arrangement of the tear-off rollers, whose rotary movement can be controlled, but depending on the round comb.

[0015] EP 2397585 A2 describes a gear arrangement in which the gripper assembly is indirectly coupled to the stripping rollers and the round comb via a shaft. The soldering point can be adjusted, but not independently of the gripper movement.

[0016] CN2923746Y discloses a drive concept consisting of a motion sensor 1+2, a stepper motor driver 3, and a stepper motor with drive wheel 4+5, which can improve the movement path of the driven tear-off rollers. It does not disclose how this is achieved.

[0017] CN200410092436 shows two tear-off rollers, each controlled separately by its own drive motor. Since the tear-off rollers are synchronized with the index positions of the main drive, their adjustment cannot be made independently of the gripper unit.

[0018] EP 2671979 A2 describes the adjustment of the tear-off roller movement independently of the movement of the gripper unit.

[0019] Besides the disadvantage of having to adjust the entire spinning line, additional disadvantages arise at the combing machine. These include, for example, a lower quality combing when very coarse bobbins are fed into the machine, resulting in quality losses.

[0020] To distinguish the invention from the prior art, two further definitions are necessary: ​​The écartement is the smallest distance between the lower clamping plate and the clamping point of the subsequent tear-off roller pair.

[0021] The feeding amount is the distance by which the feeding cylinder advances the cotton tape or fiber tapes into the clamp when feeding from cans with each comb movement, for example by 6 mm.

[0022] The purpose of the invention is to address the aforementioned disadvantages.

[0023] This problem is solved by the subject matter of independent claims 1 and 10. Advantageous further developments are specified in the dependent claims.

[0024] The invention relates to a combing machine with several combing heads, wherein at least one wadding strip is unwound from a wadding roll at each combing head and fed to a feed cylinder and a gripper unit, the combed fibers are combed out of the wadding strip and vacuumed up by means of fixed and round combs, and the resulting fiber pile is formed into a fiber sliver which is stretched with the other fiber slivers from the other combing heads to form a single fiber sliver. Instead of the wadding strip, at least one fiber sliver can also be fed to the gripper unit from a can.

[0025] The invention includes the technical teaching that a first pair of tear-off rollers and a second pair of tear-off rollers are arranged after the gripper unit, which perform a stepping motion, the size and timing of which can be changed independently of the movement of the gripper unit by means of at least one drive, so that a conveying path of the formed fiber pile can be variably adjusted in forward and reverse delivery.

[0026] The invention is based on the understanding that by changing the conveying path of the fiber pile during forward and reverse feeding by the tear-off rollers, the overlap length of the fiber strands is altered, resulting in a more stable and dense fiber pile. Particularly at high combing rates, the fiber pile can become thin, unstable, and perforated, which impairs the quality of the subsequent combed sliver. The change in conveying path is independent of the movement of the gripper unit and the movement of the circular and fixed combs, so the movement kinematics of the combing machine remain unchanged. Only the overlap length of the fiber strands changes, thereby altering the formation of the fiber pile. The set écartement and the feed rate of the combing machine remain unchanged.Only by varying the size and timing of the rotational movement of the tear-off rollers during a comb cycle can the fiber pile be made denser or lighter.

[0027] The drive(s) can be controlled by a controller, which is designed to adjust the rotational movement of the tear-off rollers based on the average fiber length or the micronaire value of the supplied wadding. Inputting the fiber quality into the controller simultaneously allows for selection of the tear-off roller rotation. The average stack length can be used as a criterion to adjust the overlap of the fiber strands. Alternatively, the micronaire value can be used as a criterion for the overlap size. Another value for setting the conveying path can be the desired CV value of the fiber strand. All three values ​​can be stored in the controller as selection criteria with corresponding data, and a pre-selected tear-off curve of the tear-off rollers can be controlled via the drives.The result is a stable fiber pile that shows no tendency towards irregularities or holes.

[0028] Preferably, the first pair of tear-off rollers and the second pair of tear-off rollers are driven by a common drive. This drive operates independently of the other kinematics of the combing machine and can be controlled by the control system. Both pairs of tear-off rollers can be driven synchronously and their movement can be variably adjusted.

[0029] Preferably, both pairs of tear-off rollers can each have a separate drive. The drives are designed to be synchronized to generate the same resulting forward movement. For example, this makes it possible to operate the second pair of tear-off rollers slightly slower for a short period so that the soldered fiber strands between the pairs of tear-off rollers are briefly compressed against each other.

[0030] In a further supplementary or alternative embodiment, the control system can be configured to adjust the rotational movement of the tear-off rollers depending on the number of comb cycles. High comb cycles tend to produce a heavier fiber web, since the stepping motion, with its continuous forward and backward delivery of the fiber web, exerts forces on it that can loosen or destroy the soldered fiber strands within the structure.

[0031] Preferably, the control system can be configured to access data from different fiber qualities in order to suggest or automatically adjust an optimal curve for the movement of the stripping rollers to the operator. This allows the customer's experience in spinning preparation to be utilized, and the preferred fiber quality with the desired settings to be saved. Alternatively, the combing machine operator can access empirical data from the machine manufacturer. The operator can also adjust and vary the conveying path based on their own experience.

[0032] Preferably, the formation of the fiber web can be supported by arranging a pair of take-off rollers and subsequently a pair of table calender rollers after the tear-off rollers. Either the take-off rollers or the table calender rollers can have their own drive, the take-off speed of which can be adjusted to the changing conveying path of the take-off rollers. This allows the take-off speed of the fiber web to be adjusted and the tension on the fiber web to be influenced in order to smooth out the fiber web waves in the nonwoven bowl.

[0033] In an advantageous embodiment, an adjustable tension can be exerted on the fiber web formed by the tear-off rollers between the take-off rollers and the take-off rollers or the table calender rollers. This adjustable tension can be achieved by an individual drive for the take-off rollers or the table calender rollers, allowing for flexible adjustment of the take-off speed of the fiber web or fiber strip.

[0034] If the take-off rollers have their own drive, tension can be applied to the fiber web formed by the tear-off rollers. The individual drive of the take-off rollers has the further advantage that the fiber web wave in the nonwoven bowl can be influenced at this point by applying tension (without stretching) to the fiber web. The speed of the take-off rollers can thus be adjusted, at least semi-automatically or fully automatically, to the changing conveying path of the take-off rollers and / or the number of comb cycles. This results in more stable running behavior of the fiber web in the nonwoven bowl.

[0035] If only the take-off rollers or only the table calender rollers have their own drive for adjusting the take-off speed, these are preferably coupled to each other in terms of drive technology.

[0036] Preferably, the tension can be adjusted by the control system depending on the rotational movement of the take-off rollers and / or the number of comb cycles. Alternatively, the tension between the take-off rollers and the table calender rollers can also be achieved by changing the rotational speed of the table calender rollers. Since the table calender rollers are usually rigidly connected to the combing head's gearbox and a constant tension exists between the take-off rollers and the table calender rollers, the tension on the fiber web can be changed either with change gears, with a flexible, variable-speed belt drive, or by converting to individual drives.

[0037] The inventive method for combing a cotton sliver with a combing machine having several comb heads provides that a cotton sliver is unwound from a cotton roll at each comb head and fed to a feed cylinder and a gripper unit. Using fixed and circular combs, combed fibers are removed from the cotton sliver and vacuumed up, and the resulting fiber pile is formed into a fiber sliver.

[0038] The invention is characterized in that a first pair of tear-off rollers and a second pair of tear-off rollers are arranged downstream of the gripper unit, the rotational movement of which can be adjusted independently of the movement of the gripper unit in terms of both magnitude and timing. This allows the conveying path of the fiber web formed by the tear-off rollers to be variably adjusted in both forward and reverse feeding.

[0039] According to the invention, the generation of the tear-off curve is flexibly adjustable, specifically in which range of the tear-off roller movement the forward or reverse feed, and thus the effective conveying path of the fiber web, is modified. Different priorities can be set when designing the curves for the tear-off roller movement. For example, the technologically relevant area of ​​engagement of the fixed comb can remain unchanged. Alternatively or additionally, the reversal points for the change in the direction of rotation of the tear-off rollers can remain unchanged. The tear-off roller movement can be adjusted so that the rest of the combing process is not affected and error-free operation with the other elements, such as the gripper unit, round comb, and fixed comb, is ensured. For example, a change in the tear-off roller movement with a lower effective fiber take-off in combination with an earlier start to the return feed of the fiber web, e.g.,A modified reversal point ensures that the circular comb cannot grasp or touch the returned fiber pile. In addition to these technological advantages, the change in the conveying path is independent of the movement of the gripper unit and the movement of the circular and fixed combs, so the movement kinematics of the combing machine remain unchanged. Only the overlap length of the fiber strands changes, which allows for modification of the fiber pile formation. The set écartement and the feed rate of the combing machine remain unchanged. The fiber pile can be made denser or thinner simply by varying the size and timing of the rotational movement of the break-off rollers during a comb cycle.

[0040] According to the invention, the rotary movement of the tear-off rollers depends on the mean fiber length or is adjusted to the micronaire value of the supplied wadding tape or to the desired CV value of the fiber tape.

[0041] This allows the overlap of the fiber strands and thus the formation of the fiber nap to be optimized, depending on the quality of the fiber processed.

[0042] Additionally or alternatively, the rotational movement of the tear-off rollers can be adjusted depending on the number of comb cycles. Due to the stepping motion and the associated forward and backward delivery of the fiber web, the forces acting on the fiber web increase with the number of comb cycles. Thus, at high comb cycles, a heavy fiber web can be produced, which prevents the soldered fiber strands in the structure from being loosened or damaged.

[0043] In an advantageous embodiment, at the beginning of a combing cycle (for example, at the start of the gripper closing and the beginning of the gripper's return movement), the rotational movement of the tear-off rollers can be increased or decreased. This can be achieved by changing the rotation angle of the tear-off rollers and / or by changing the acceleration, which alters the curve. The reversal points for the change in the direction of rotation of the tear-off rollers can remain unchanged, thus minimizing the impact on the rest of the combing process. In this way, if the tear-off roller movement is changed, resulting in a lower effective fiber take-off in combination with an earlier start to the return of the fiber pile (e.g., by changing the reversal point), it can be ensured that the round comb cannot grasp or touch the returned fiber pile.

[0044] Preferably, the rotational movement of the tear-off rollers can be increased or decreased towards the end of the fixed comb's engagement. This ensures that the technologically relevant engagement area of ​​the fixed comb remains unchanged.

[0045] Alternatively or additionally, tension can be applied to the fiber web formed after the tear-off rollers. This tension can be adjusted depending on the rotational movement of the tear-off rollers and / or the number of comb cycles. The technical effect is that, due to changes in the conveying path of the tear-off rollers, the fiber web can become lighter or heavier, which is visible as an enlarged or reduced irregular fiber web wave on the nonwoven bowl.

[0046] A change in the conveying path of the tear-off rollers results in a change in the mass of the fiber strip, so that an adjustment of the stretching in the stretching unit of the combing machine or in a subsequent control section can be made.

[0047] Further features and advantages of the invention will become apparent from the following description of preferred embodiments. These show: Figure 1: A schematic side view of a combing head of a combing machine according to the prior art; Figure 2a: A first fiber pile consisting of individual compound fiber strands; Figure 2b: A further fiber pile consisting of individual compound fiber strands; Figure 3: A diagram showing a movement of the first pair of tear-off rollers according to the invention; Figure 4: A diagram showing a further movement of the first pair of tear-off rollers according to the invention; Figure 5: A diagram showing a further movement of the first pair of tear-off rollers according to the invention; Figure 6: A diagram showing a further movement of the first pair of tear-off rollers according to the invention; Figure 7: A detailed view of the area of ​​a combing head after the tear-off rollers.

[0048] The following are, with reference to the Figs. 1 to 2b the state of the art and in the Figures 3 to 7Preferred embodiments of the combing machine according to the invention are explained. Identical features in the drawing are identified by the same reference numerals. It should be understood that the drawing is simplified and, in particular, not to scale.

[0049] In Figure 1A combing head 20 according to the prior art is shown, of which at least eight are mounted on a combing machine. For the sake of clarity, the exemplary embodiment is shown and described using only one combing head 20, wherein the details shown are installed on each of these combing heads, except for the common drive units and the tape storage. The combing head 20 consists, among other things, of two winding transport rollers 2, 3, on which a wadding roll 1 with a winding sleeve rests and from which the wadding tape 4 is unwound by a tensile load from a feed cylinder 7. The winding transport rollers 2, 3 can be driven individually or both together. The design of the winding transport rollers 2, 3, whether they are only rotating and not driven, or individually or both driven, is not relevant to the invention.

[0050] The wadding strip 4 is transferred to a feed cylinder 7 of a gripper unit 5. The gripper unit 5 is movable back and forth via levers and is driven by a shaft 6, which is connected to a gearbox 17. The gearbox 17 is driven by a motor 18. According to the prior art, the motor 18 and gearbox 17 are connected to a control unit 19, via which the combing process can be adjusted with parameters not further specified. According to the illustrated example, the gripper unit 5 is in a forward position and transfers the combed-out fiber strand to a subsequent pair of tear-off rollers 10, 12, the first in the fiber transport direction. A circular comb 8 is rotatably mounted below the gripper unit 5, which combs out the fiber strand presented by the closed gripper via its comb segment. The circular comb 8 is also driven by the gearbox 17.A ratchet wheel (not shown) is mounted on the feed cylinder 7. This ratchet wheel is rotated incrementally by the reciprocating motion of the gripper unit 5 via a pawl (also not shown), thereby feeding the wadding strip 4 to the gripper jaws for combing. During operation, the wadding strip 4 is continuously unwound by the rotational movement of the wadding roll 1 over the winding transport rollers 2, 3 and reaches the feed cylinder 7. The wadding is then fed via the feed cylinder 7 to the gripper jaws of the gripper unit 5 for combing and subsequently discharged to the first pair of tear-off rollers 10, 12 in the fiber transport direction. The discharged fiber strand is drawn through the fixed comb 9 and soldered to the preceding fiber strand. The resulting fiber pile 14 is transferred via a second pair of tear-off rollers 11, 13 in the fiber transport direction.The resulting fiber web 14, consisting of individual soldered pieces of fiber roving, is guided over a fleece bowl 22 and drawn by take-up rollers 16 into a funnel 15, where it is formed into a fiber ribbon 21. Subsequently arranged table calender rollers 23 draw off the fiber ribbon 21 and, together with the fiber ribbons also formed at the other combing heads, feed it to a drafting unit (not shown) of the combing machine. The fleece emerging from the drafting unit of the combing machine is gathered into a fiber ribbon, the so-called combing machine ribbon, and transferred to a ribbon tray for placement in a can.

[0051] In this state of the art, the gripper unit 5 is moved into a forward, open position, whereby the tear-off rollers 10, 12, by means of a reverse rotation, convey a previously combed-out fiber strand with its rear end section towards the front end section of the cotton wool clamped by the gripper. The tear-off rollers 11, 13 perform the same movement, so that the fiber pile 14 is moved back a short distance. The fiber strand combed out by the round comb 8 lies onto this rear end section and is drawn together with it into the clamping point of the tear-off rollers 10, 12, as the tear-off rollers 10, 12 and 11, 13 reverse their direction of rotation again. During this rotation, in which the angle of rotation is approximately twice that of the preceding reverse rotation, the fiber strand is torn from the cotton wool located in the gripper unit 5. The rear end of the torn fiber beard is pulled through the fixed comb 9.The stripping rollers 10, 12, 11, 13 perform a stepping motion, retracting an end piece of the fiber strip removed during the previous comb pass during a return rotation. The beginning piece of the fiber strip is placed onto this end piece and, after a reversal of rotation, soldered together by the pressure of the two stripping rollers 10, 12. The stripping rollers 10, 12, 11, 13 must not only change their direction of movement twice during each comb pass, but also rotate a shorter distance on the return stroke than on the forward stroke. If the following description only describes the rotation of the first pair of stripping rollers 10, 12, the person skilled in the art knows that the second pair of stripping rollers 11, 13 also performs the same rotation simultaneously, since otherwise the soldered fiber strips would be compressed or stretched between the pairs of stripping rollers.

[0052] In Figure 2aA cross-section of a uniform fiber mat 14 is shown, composed of individual fiber strands. The fiber strands, with length LFB, can be arranged as parallelograms that overlap by length LÜ. The fiber mat 14 shown here is very uniform, unlike the fiber mat of Figure 2b , which has a large number of alternating thin and thick spots.

[0053] The tear-off rollers 10, 12, 11, 13 are typically driven by rotating the lower tear-off rollers 10, 11 using an electric motor or by being coupled to the gearbox 17. The upper tear-off rollers 12, 13 are pressed against their respective tear-off rollers 10, 11, analogous to the upper rollers of a drafting unit, and rotate along with them due to the resulting frictional connection.

[0054] The tear-off rollers 10, 11 of two immediately adjacent comb heads 20 can be rotationally connected to each other via a shaft. This means, for example, that only one of the tear-off rollers 10 needs to be driven.

[0055] The tear-off rollers 10, 11 can be individually or in pairs (i.e., per combing head 20) equipped with their own drive, independent of the other driven components of the combing machine. This allows the movement sequence of the tear-off rollers 10, 11 to be changed per combing cycle (= tear-off curve) without altering the movement sequence of, for example, the gripper unit 5.

[0056] This drive mechanism allows the movement sequence of at least the tear-off rollers 10, 12 to be specifically adjusted with regard to their conveying path. The combed fiber web 14 emerging from the second pair of tear-off rollers 11, 13 is deposited onto a nonwoven tray 22 (not shown here) and guided by means of take-off rollers 16 through a hopper 15, which transforms the combed fiber web 14 into a fiber ribbon 21.

[0057] The Figures 3 to 6The diagrams show an original tear-off curve AK1 (dashed line) and a modified tear-off curve AK2 (solid line) according to the invention for the first pair of tear-off rollers 10, 12. The corresponding angle of rotation of the first pair of tear-off rollers 10, 12, which can range from -150° to +150°, is shown on the left ordinate of the diagrams. As previously explained, the tear-off rollers 11, 13 perform the same rotational movement, although this is not explicitly mentioned again below. Instead of the angle of rotation, the corresponding conveying path of the tear-off rollers 10, 12 could also be shown here. This path is shown above scale 0 in the material transport direction away from the gripper unit 5 and below scale 0 in the opposite direction towards the gripper unit 5. The abscissa shows a complete combing cycle at 24 nips / min in the range from 0 to 2.5 s.Any desired time could be entered here, corresponding, for example, to a combing cycle of 1 nip / min up to the currently achievable 650 nips / min. Alternatively, the index position of the drive motor of the tear-off rollers could be entered here, from, for example, 0 to 40, whereby the starting point can be shifted as desired, for example, to index position 24. In the diagrams, the movement of the gripper unit 5 and the associated opening and closing movement are shown on the abscissa in the upper section. The engagements of the fixed comb 9 and the circular comb 8 are shown in gray in the time sequence.

[0058] In the original tear-off curve AK1, the tear-off rollers 10 and 12 rotate at t = 0 s, the start of a combing cycle, at a rotation angle of 0°, until they come to a standstill or the first reversal point U11 of the rotation at t = 0.8 s in the material transport direction. At the first reversal point U11, the tear-off rollers 10 and 12 have rotated by 90°.

[0059] From the reversal point U11, the tear-off rollers 10 and 12 rotate against the material transport direction, i.e., back towards the gripper unit 5. Shortly thereafter, the fiber strand clamped in the gripper unit 5 is combed out by the round comb 8. The tear-off rollers 10 and 12 continue to rotate against the material transport direction to take over the fiber strand clamped by the gripper unit and convey the fiber back. From the reversal point U2, which corresponds to a rotation angle of -135°, they change their direction of rotation again in the material transport direction, which feeds the gripper unit 5 via the wadding belt 4. Until the end of the combing cycle with t = 2.5 s, the tear-off rollers 10 and 12 rotate again in the material transport direction to a rotation angle of 120°, at which point the end of the fiber strand is combed out by the fixed comb 9.

[0060] The changed AK2 deceleration curve in Figure 3The combing cycle starts at a rotation angle of 30°, accelerates more rapidly, and reaches the first reversal point U21 at a rotation angle of 118° at t = 0.6 s. From there, the first pair of tear-off rollers 10, 12 rotates back more quickly and, from a rotation angle of 90° at t = 0.85 s, rotates identically to the tear-off curve AK1. At the start of the engagement by the fixed comb 9, the tear-off roller movement AK2 is unchanged from the tear-off roller movement AK1; the curves are perfectly parallel, only running with a modified—in this case, reduced—conveyor path. The tear-off rollers perform exactly the same rotational movement, whereby the curve with the reduced conveying path AK2 conveys less material but returns more. The motion function only differs after the fixed combing, because the return delivery begins earlier due to the earlier reversal point U21.

[0061] The advantage according to the invention lies in a modified conveying path, reduced in this exemplary embodiment by, for example, 6.25 mm, compared to the original tear-off curve AK1. The exemplary reduced conveying path given here corresponds to the circumference of the tear-off roller with the associated angle of rotation. This achieves a material return before the start of the circular combing process, which allows the overlap length LÜ of the fiber beards to be adjusted to the mean fiber length. For example, the mean fiber length is 25 mm for medium-staple cotton and 32 mm for long-staple cotton. Depending on the staple length of the fibers, the overlap length LÜ of the individual fiber beards, which together form the fiber pile 14, would vary considerably with the same conveying path. As a result, the fiber pile 14 can exhibit thin and thick areas ( Figure 2b), which make the fiber pile 14 very uneven. By changing the break-off curve movement to adapt the conveying path to the average stack length of the fibers to be combed, a more stable fiber pile 14 can be produced at high combing ratios, which has a beneficial effect on the resulting fiber band at each combing head and on the combing quality. In addition, the effective conveying path can be adapted to the micronaire value of the fiber material. With a coarse fiber material with a micronaire value > 4.3, a more stable fiber pile 14 can be produced by reducing the conveying path. The soldering point remains unchanged. Only the overlap length LÜ changes due to the altered conveying path. Thus, the drive components for the gripper unit can continue to be used unchanged. Only by adapting orBy changing the rotational movement of the first pair of tear-off rollers 10, 12, the overlap length LÜ of the fiber strands is adjusted to the mean stack length of the fibers or to the Micronaire value. This change is made exclusively via the drives of the first pair of tear-off rollers 10, 12, which can preferably be driven by individual drives or servo drives.

[0062] During the rotation of the tear-off rollers 10, 12 in the material transport direction, the gripper unit 5 first moves backward, and then forward. When the tear-off rollers 10, 12 rotate backward against the material transport direction, the gripper unit 5 moves forward, receiving the cotton tape at t = 1.9 s. This corresponds to the reversal point U2. At different times and positions of the gripper unit 5, both the fixed comb 9 and the circular comb 8 are engaged. Between t = 1.5 s and t = 2.3 s, the gripper unit 5 moves against the material transport direction, i.e., backward, before again conveying the cotton or fiber tape in the material transport direction. According to the modified tear-off curve AK2 compared to tear-off curve AK1, the tear-off rollers 10, 12 rotate forward by a smaller angle than in the tear-off curve AK1.The AK2 tear-off curve reduces the conveying distance of the tear-off rollers 10, 12 by 6.25 mm compared to the AK1 tear-off curve in the example shown. This change results from the altered rotation angle of, for example, 30° of the AK2 tear-off curve in combination with the tear-off roller diameter. Due to the modified curve shape, 6.5 mm less fiber material is conveyed per comb clearance in this example.

[0063] In the exemplary embodiment of the Figure 4 The original detachment curve AK1 is identical to the detachment curve AK1 from the Figure 3 The modified breakaway curve AK2 exhibits a rotation angle that is 30° smaller in each combing cycle and accelerates more slowly than in the embodiment of the Figure 2and reaches the first reversal point U21 with a rotation angle of 90° at t = 0.8 s, which is identical to the reversal point U11 of the original break-off curve AK1. From this reversal point, the break-off curve AK2 is again identical to the break-off curve AK1. Here, too, the conveying distance is reduced by 6.25 mm per comb stroke compared to the original trajectory of the rotation of the break-off rollers 10, 12. This reduced conveying distance occurs in the final phase of the fixed combing, when the effect of the fixed comb 9 has already diminished. The subsequent curve trajectory for the change between forward and reverse movement remains unchanged. The conveying in the material flow direction is lower in the final phase of the fixed combing, but the return of the fibers is the same, resulting in an overall shorter conveying distance.

[0064] In Figure 5The AK2 break-off curve exhibits a different and steeper profile than the AK1 break-off curve only in the range of 0s to 0.5s. After completion of the fixed combing process, the AK2 break-off curve follows the same profile as the AK1 break-off curve. While the absolute conveying distance of the break-off curves remains unchanged, this steeper profile of the AK2 break-off curve allows for optimization of the fiber beard overlap.

[0065] In Figure 6 The breakaway curve AK2 exhibits a modified and flatter profile than the breakaway curve AK1 only in the range of 2.2s to 2.5s. This change also results in a shortened conveying path of, for example, 4 mm, which corresponds to a reduced rotation angle of 20°. In this embodiment, however, the change in the breakaway curve AK2 occurs at the beginning of the intensive fixed combing phase, during which the curve AK2 diverges from the original curve AK1 with a shallower slope.

[0066] All embodiments have in common that, despite the changed movement of the tear-off rollers 10, 12, the soldering time remains unchanged.

[0067] Changing the conveying path of the tear-off rollers 10 and 12 allows for a change in the overlap length LÜ of the fiber strands forming a fiber pile 14, enabling a more stable and dense pile. Particularly at high comb clearances, the fiber pile 14 can become thin, unstable, and perforated, impairing the quality of the subsequent combed strip. This change in conveying path is independent of the movement of the gripper unit 5 and the movement of the circular and fixed combs 8, 9, so the movement kinematics of the combing machine remain unchanged. Only the overlap length LÜ of the fiber strands changes, thereby altering the formation of the fiber pile 14 by making it denser or thinner – for example, depending on the average stack length. Since the feed rate to the gripper unit remains constant, the density of the fiber pile 14 is influenced by varying the conveying path of the tear-off rollers 10, 12.The different conveying paths of the tear-off rollers 10, 12 can be varied, for example, depending on the cotton quality to be processed (average staple length) and / or the number of combing cycles to be achieved, and stored in the control of the combing machine.

[0068] By entering the cotton quality to be processed, the operator can be prompted to select the appropriate tear-off curve or conveying path length, or these can be set automatically. According to the invention, the conveying path of the fiber bundle can be increased or decreased by changing the curve of the tear-off rollers of the tear-off roller pairs, thus influencing the formation of the fiber pile 14. Preferably, different tear-off curves with different effective conveying paths are stored in a database or program, which is accessed by a control system that is either part of the combing machine or coupled to it. The stored tear-off curves can be user-selectable. Alternatively, the user can enter data such as production, fiber data, combing cycle count, and the like. Based on this information, the control system can select the appropriate tear-off curve or suggest it to the operator.Alternatively, an automatic curve selection can be achieved using a neural network. During training, the combing machine can set the break-off curve(s) of preferably all comb heads, and a user inputs the quality of the combed and stretched fiber ribbon. The control system then attempts to find the optimal settings.

[0069] At high comb cycles, the delicate fiber layer 14 in the nonwoven bowl 22 is often a production-limiting factor before ribbon formation. The piling motion of the machine moves the fiber layer 14 back and forth, causing holes to form in the fiber layer 14 due to the acceleration forces, and / or tearing at the thin points, thus preventing ribbon formation. At high comb cycles, the conveying path can be reduced, increasing the overlap of the fiber strands in length and resulting in a very thick fiber layer 14 – with the same feed quantity. This produces a heavier fiber layer 14 that is significantly more stable. Alternatively, with an average fiber stack length of, for example, 32 mm (25 mm is the average), the conveying path can be increased if this is compatible with the comb cycle.

[0070] Instead of reducing the size of the conveyor path of the tear-off rollers, it is also possible to increase it. This is advantageous when the combed fiber sliver is intended to contain only relatively long fibers. Ideally, the conveyor path is always chosen to correspond to the average fiber length, e.g., 25 mm for medium-staple cotton or 32 mm for extra-long-staple cotton.

[0071] Alternatively or additionally, the conveying path can be adjusted to the micronaire value of the fiber material. For example, with coarse fiber material (e.g., micronaire value > 4.3), a more stable fiber pile 14 and thus a shorter effective conveying path can be helpful.

[0072] Shortening the conveying path also offers the advantage of energy savings for the combing machine, as this is particularly energy-intensive due to the stepping motion at the turning points U1 and U2 of the curves. The energy demand of the drives also increases with the number of comb cycles. Depending on the ideally selected conveying path, the curves can be specifically generated to achieve good technological results with low energy consumption.

[0073] According to the invention, the generation of the tear-off curve is flexibly adjustable, specifically in which range of the tear-off roller movement 10, 12 the forward or reverse delivery, and thus the effective conveying path of the fiber web 14, is changed. Different priorities can be set when designing the curves for the tear-off roller movement 10, 12. For example, the technologically relevant area of ​​engagement of the fixed comb 9 can remain unchanged. Alternatively or additionally, the reversal points for the change in the direction of rotation of the tear-off rollers 10, 12 can remain unchanged. The tear-off roller movement 10, 12 can thus be adjusted so that the rest of the combing process is not affected and error-free operation with the other elements, such as the gripper unit 5, the rotary comb 8, and the fixed comb 9, is ensured.For example, if the tear-off roller movement 10, 12 is changed with a lower effective fiber take-off in combination with an earlier start of the return delivery of the fiber pile 14, e.g. by a changed reversal point, it can be ensured that the round comb 8 cannot grasp or touch the returned fiber pile 14.

[0074] In Figure 7 The area downstream of the tear-off rollers of a combing head on each combing machine is shown. The web hopper 15 is located downstream of the take-off rollers 16 and upstream of the table calender rollers 23. After the second pair of tear-off rollers 11, 13, of which the second upper tear-off roller 13 is visible, the fiber web 14 is settled on or in the web bowl 22. Due to changes in the conveying path of the tear-off rollers, the fiber web 14 can become lighter or heavier, allowing the delivery or take-off speed downstream of the last pair of tear-off rollers 11, 13 to be adjusted.

[0075] The subsequent pair of take-off rollers 16 can preferably have an individual drive that reacts to the changed conveying path and thus to the changed mass of the fiber web 14, for example by taking it off more slowly when the mass of the fiber web 14 is higher, since the feed amount to the gripper unit 5 remains unchanged. After the take-off rollers 16, the fiber web 14 is formed into a fiber strip 21 by the belt hopper 15, and the fiber strip 21 is conveyed by the table calender rollers 23 onto the conveyor belt of the combing machine. A change in the conveying path of the take-off rollers results in a change in the strip mass of the fiber strip 21, so that an adjustment of the drawing can be made at the common drawing unit of the combing machine for all fiber strips or in a subsequent regulating section if the combed fiber strip with a strip mass of 5 to 10 ktex is to be processed further.The tension on the fiber web 14 in the nonwoven bowl 22 can be varied via an individual drive of the take-up rollers 16. The individual drive of the take-up rollers 16 has the further advantage that the fiber web wave in the nonwoven bowl 22 can be influenced at this point by applying tension (without stretching) to the fiber web 14 in the nonwoven bowl 22. The speed of the take-up rollers 16 can thus be adapted, at least semi-automatically or fully automatically, to the changing conveying path of the take-up rollers and / or the number of comb cycles. This results in more stable running behavior of the fiber web 14 in the nonwoven bowl 22.

[0076] The speed of the table calender rollers 23 can then be adjusted to a change in the rotational speed of the take-off rollers 16, which in turn also draw off the fiber strip 21 faster or slower. Since the table calender rollers 23 are usually rigidly connected to the combing head's gearbox and there is a constant tension between the take-off rollers 16 and the table calender rollers 23, the rotational speed can be changed either with change gears, with a flexible belt drive with variable speed, or by converting to individual drives.

[0077] Alternatively, only the table calender rollers 23 can have a variable drive with which the take-off speed of the fiber strip 21 can be adjusted due to the reduced or increased fiber mass.

[0078] The invention allows the intervention required for nonwoven quality to occur locally, precisely where it is needed, i.e., directly at the fiber nap formation / soldering stage. The feeding of the cotton roll 1 or the fiber strip from cans to the combing machine and the actual combing process (comprising feeding, feeding, tensioning, rotary and fixed combing, drawing, and can discharge) advantageously remain unchanged. The drawing process can, for example, be directly adjusted to compensate for the change in strip mass (lighter or heavier) resulting from adjustments to the conveying path. This can be done in the drawing unit of the combing machine itself and / or in a subsequent section. Furthermore, the take-off speed of the take-off rollers 16 or table calender rollers 23 can be adjusted as needed.

[0079] Any necessary increase or decrease in fleece weight, and thus individual comb head weight, can be adjusted directly in the drafting unit of the combing machine. Ideally, this keeps the output quantity of fiber sliver into the can per unit of time and the overall production of the combing machine unchanged. Furthermore, unlike geared machines, there is no need to intervene at much earlier process steps or adjust the entire spinning line.

[0080] A constant tension is typically maintained between the last tear-off rollers 11, 13 and the take-off roller 16, and between the take-off roller 16 and the table calender rollers 23. If the conveying path is varied, the speed of these rollers can be adjusted accordingly. The compensation for the altered individual comb head strip formed from the respective fiber pile 14, and thus the draft at the combing machine's drafting unit, can be achieved directly via a warpage adjustment at the drafting unit. It is also conceivable to shift this compensation, at least partially, to subsequent process steps such as a downstream control section. Another alternative, in the case of a significantly altered conveying path and the resulting very heavy strips, is to adjust the width of the combing machine's drafting unit. Reference sign

[0081] 1 Cotton winding 2 Winding transport roller 3 Winding transport roller 4 Cotton belt 5 Clamping unit 6 Shaft 7 Feeding cylinder 8 Rotary comb 9 Fixed comb 10 First lower tear-off roller 11 Second lower tear-off roller 12 First upper tear-off roller 13 Second upper tear-off roller 14 Fiber web 15 Hopper 16 Take-off rollers 17 Gearbox 18 Motor 19 Control 20 Combing head 21 Fiber belt 22 Nonwoven bowl 23 Table calender rollers AK1, AK2 Tear-off curve L Ü Length Overlap LFB Length Fiber beard U1 1 , U2, U2 1 Rotation reversal point of the tear-off rollers

Claims

1. Combing machine having a plurality of combing heads (20), wherein at each combing head (20) at least one lap sliver (4) is unwound from a lap roll (1) and supplied to a feed cylinder (7) and a nipper unit (5), the noils are combed out of the lap sliver (4) by means of top comb and circular comb (9, 8) and are removed by suction, and the resulting fibre web is shaped to form a fibre sliver, which is drawn with the other fibre slivers of the other combing heads to form a single fibre sliver, wherein there are arranged downstream of the nipper unit (5) a first pair of detaching rolls (10, 12) and a second pair of detaching rolls (11, 13) which perform a pilgrim step movement and the rotational movement of which can be changed in terms of extent and in terms of profile over time, independently of the movement of the nipper unit (5), by means of at least one drive, so that a feed distance of the fibre web (14) that is formed is variably adjustable in terms of forward and / or backward delivery, characterized in that the drive or drives are controlled by means of a controller, the controller being configured to adjust the rotational movement of the detaching rolls (10, 12; 11, 13) in dependence on the mean fibre length or to the micronaire value of the fed lap sliver or to the desired CV value of the fibre sliver (21).

2. Combing machine according to claim 1, characterised in that the first pair of detaching rolls (10, 12) and the second pair of detaching rolls (11, 13) are driven by a common drive.

3. Combing machine according to claim 1, characterised in that each pair of detaching rolls (10, 12; 11, 13) is driven by means of a separate drive, the drives being configured to be synchronised in order to generate the same resulting forward movement.

4. Combing machine according to any one of claims 1 to 3, characterised in that the controller is configured to adjust the rotational movement of the detaching rolls (10, 12; 11, 13) in dependence on the nip rate.

5. Combing machine according to claim 1, characterised in that the controller is configured to access the data of different fibre qualities in order to suggest to the operator or to automatically set an optimal curve for the movement of the detaching rolls (10, 12; 11, 13) on the basis of those data, wherein the experience of the customer in spinning preparation can here be used, and the preferred fibre quality with the desired settings can be stored, or the operator of the combing machine can refer to empirical data of the manufacturer of the machine, or the operator can set and vary the feed distance on the basis of his own experience.

6. Combing machine according to any one of the above-mentioned claims, characterised in that, downstream of the detaching rolls (10, 12; 11, 13) in the material transport direction, there are arranged a pair of delivery rolls (16) and, thereafter, a pair of table calender rolls (23), either the delivery rolls (16) or the table calender rolls (23) having their own drive.

7. Combing machine according to claim 6, characterised in that the delivery rolls (16) and the table calender rolls (23) are coupled with one another in terms of the delivery speed.

8. Combing machine according to claim 6, characterised in that the delivery speed of the delivery rolls (16) or of the table calender rolls (23) is adjustable by the controller in dependence on the rotational movement of the detaching rolls (10, 12; 11, 13) and / or the number of nips.

9. Method for combing a lap sliver (4) by means of a combing machine having a plurality of combing heads (20), wherein at each combing head (20) a lap sliver (4) is unwound from a lap roll (1) and supplied to a feed cylinder (7) and a nipper unit (5), noils are combed out of the lap sliver (4) by means of top comb and circular comb (9, 8) and are removed by suction, and the resulting fibre web (14) is shaped to form a fibre sliver (21), wherein there are arranged downstream of the nipper unit (5) a first pair of detaching rolls (10, 12) and a second pair of detaching rolls (11, 13), the rotational movement of which is adjusted in terms of extent and in terms of profile over time independently of the movement of the nipper unit (5), so that the feed distance of the fibre web (14) formed by the detaching rolls (10, 12; 11, 13) is variably adjustable in terms of forward and / or backward delivery, characterised in that the rotational movement of the detaching rolls (10, 12; 11, 13) is adjusted in dependence on the mean fibre length or to the micronaire value of the fed lap sliver or to the desired CV value of the fibre sliver (21).

10. Method according to claim 9, characterised in that the rotational movement of the detaching rolls (10, 12; 11, 13) is adjusted in dependence on the nip rate.

11. Method according to claim 9 or 10, characterised in that the rotational movement of the detaching rolls (10, 12; 11, 13) can be changed in different regions of the nip so that the feed distance of the fibre web (14) formed by the detaching rolls (10, 12; 11, 13) is variably adjustable in terms of forward and / or backward delivery.

12. Method according to claim 9, characterised in that, at the end of the engagement of the top comb (9), the rotational movement of the detaching rolls (10, 12; 11, 13) is increased or reduced.

13. Method according to any one of claims 9 to 12, characterised in that the delivery speed of the fibre web (14) downstream of the detaching rolls (10, 12; 11, 13) is adapted to the changed feed distance.

14. Method according to claim 13, characterised in that a tension is generated on the fibre web (14), which tension is adjustable in dependence on the rotational movement of the detaching rolls (10, 12; 11, 13) and / or the number of nips.

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