Comber and method for operating a comber

Abstract

The invention relates to a combing machine and a method for combing fibers, comprising a combing machine with a plurality of combing heads (20), wherein at least one sliver (4) is unwound from a lap (1) on each combing head (20) and fed to a feed roller (7) and a nipper mechanism (5), the combing noil is combed out of the sliver (4) and sucked off by means of a top comb and a circular comb (9, 8), and the fiber layer produced is formed into a fiber strip by means of a trumpet (15), which fiber strip is drawn together with the other fiber strips of the other combing heads into a single fiber strip. The invention is characterized in that a first pair of separating rollers (10, 12) and a second pair of separating rollers (11, 13) are provided after the nipper mechanism (5), wherein the first pair of separating rollers (10, 12) is configured to perform a back-and-forth rotary motion for the purpose of the joining and separating process of fiber tufts to the fiber layer (14), and the second pair of separating rollers (11, 13) is configured to perform a constant rotary motion, so that a sag (32) of the fiber layer (14) is formed between the pairs of separating rollers (10, 12 and 11, 13), the length of which changes over the course of a combing cycle.

Description

Technical Field

[0001] The invention relates to a combing machine and a method for operating a combing machine. Background Art

[0002] In conventional combing processes, such as the Hermann combing process, cotton is pulled from a roll and fed to a nipper by means of a feed roller. In the retracted position, the nipper is closed and secures the leading end section of the cotton protruding from the nipper, which forms a fiber clump. The fiber clump protruding from the nipper is combed out by a circular comb positioned below the nipper. The nipper then moves to a forward, open position, where the detaching roller rotates backward, feeding the previously combed fiber clump with its trailing end section toward the leading end section of the cotton clamped by the nipper. The fiber clump combed out by the circular comb is placed onto the trailing end section and, together with it, is drawn into the clamping position of the detaching roller as the detaching roller changes its direction of rotation. This rotation angle is approximately twice as large as with the previous backward rotation, and the fiber clump is now separated from the cotton in the nipper mechanism. In this process, the trailing end of the separated fiber clump is pulled through the top comb.

[0003] In this case, the detaching rollers perform a pilger-style motion, in which they return the end of the fiber tuft removed during the previous combing cycle during counter-rotation. The beginning of the fiber tuft is placed onto this end, and after the direction of rotation is reversed, the two rollers engage the ends through pressure. Not only must the detaching rollers change their direction of movement twice during each combing cycle, but they also rotate over a shorter path during the return stroke than during the forward stroke. This type of detaching roller motion is often achieved by using eccentric discs, cam discs, or cam grooves, which are robustly connected to the nipper movement via a transmission mechanism. With combing heads connected side by side and combing cycles exceeding 400 times per minute, this back-and-forth pilger-style motion of the detaching rollers places significant loads on the shafts, causing significant vibrations in the comber and requiring a large amount of energy. The drive motors for the detaching rollers must be highly efficient and require a powerful servo inverter to power them. The constant acceleration and deceleration result in high power losses, which are reflected in the energy consumption of the combing machine and, at combing cycles exceeding 500 per minute, the electric motors must be water-cooled. Consequently, the motors are quite expensive.

[0004] WO2013 / 182260A1 discloses a combing machine having a drive device for generating a pilger-type motion for a detaching roller of the combing machine. The combing machine comprises a first electric motor rotating in a uniform motion and a second electric motor equipped with operating means that are subjected to a unidirectional motion law with acceleration and deceleration phases. The first and second motors are always engaged and rotate continuously in the same direction. In this case, their rotational motion is combined by a differential device, thereby achieving a pilger-type composite motion on the detaching roller. In order to increase the degree of freedom in the design of the motion curve of the detaching roller and to achieve higher efficiency of the combing machine, the second electric motor is a servo motor, which converts the uniform motion of the first electric motor into a non-uniform rotational motion and is connected to an electronic control and / or regulation device. Summary of the Invention

[0005] Starting from this known prior art, the object of the present invention is to provide a combing machine and a method for combing out short fibers, with which the aforementioned disadvantages are reduced.

[0006] The present invention relates to a combing machine having multiple combing heads, wherein at least one sliver is unwound from a cotton roll on each combing head and fed to a feeding roller and a nipper mechanism, combing waste is combed out and sucked out from the sliver by means of a top comb and a circular comb, and the resulting fiber layer is deformed into a fiber sliver by means of a bell mouth, which is stretched into a single fiber sliver together with other fiber slivers from other combing heads.

[0007] The present invention includes the following technical teachings: a first pair of detaching rollers and a second pair of detaching rollers are arranged after the nipper mechanism. The first pair of detaching rollers is configured to perform a reciprocating rotational motion for the purpose of joining and separating the fiber tufts from the fiber layer, while the second pair of detaching rollers is configured to perform a constant rotational motion, thereby forming an overhang of the fiber layer between the paired detaching rollers. The length of this overhang varies within a combing cycle. This overhang forms a material buffer for the fiber layer that compensates for the different rotational motions and rotational speeds of the detaching roller pair without damaging the fiber tufts joined to the fiber layer. The overhang must be long enough to avoid tensile stress or drafting on the joined fiber layer. This depends on the feed rate and the diameter of the detaching rollers. Thus, the first pair of detaching rollers can maintain a pilger-like motion, thereby maintaining the conventional combing process, including the nipper motion and transmission. Only the motion and drive of the second pair of detaching rollers, which have a constant direction of rotation, are varied. The motor for the second pair of detaching rollers can be made smaller and not provided with water cooling, which makes the combing machine cheaper and more energy-efficient.

[0008] Accordingly, the combing process according to the present invention is designed such that a fiber clump is separated from the sliver by a back-and-forth rotational motion and joined to the fiber layer by means of a first pair of detaching rollers arranged after the nipper mechanism, wherein a second pair of detaching rollers, which is located downstream in the fiber transport direction, performs a rotational motion that remains constant in the fiber transport direction, wherein the length of the overhang of the fiber layer formed between the pairs of detaching rollers varies within a combing cycle. Due to the different rotational directions and speeds of the pairs of detaching rollers, a material buffer is generated by the overhang, which makes it possible to maintain the same rotational direction of the second pair of detaching rollers, even though the first pair of detaching rollers continues to perform a pilgrimage motion and the movement of the second pair of detaching rollers is therefore in the opposite direction.

[0009] The rotational movement of the second pair of detaching rollers is preferably constant throughout all combing cycles. Therefore, a simpler drive motor can be used for the second pair of detaching rollers, designed as a servomotor with significantly lower drive power. Because the final forward movement of the detaching roller pairs must be absolutely identical in order not to exhaust the overhang, the drive motors of the first and second pairs of detaching rollers must operate synchronously. However, the drive motors for the second pair of detaching rollers can be of a simpler design, have lower power, and lack active cooling.

[0010] Alternatively, the rotational movement of the second pair of detaching rollers during one combing cycle can be non-uniform while rotating in the same direction. The second pair of detaching rollers can vary their rotational speed while rotating in the same direction, thereby maintaining a constant length of the overhang between the paired detaching rollers. This reduces pulsations in the length of the overhang between a maximum and a minimum.

[0011] The overhang of maximum length is preferably formed at a first reversal point of the first pair of detaching rollers, from which the pair of detaching rollers moves the fiber layer counter to the fiber transport direction again towards the nipper arrangement.

[0012] Preferably, an overhang of minimum length is formed at the second reversal point of the first pair of detaching rollers, from which the pair of detaching rollers moves the fiber layer away from the nipper arrangement again in the fiber transport direction. In this case, the difference in the rotation angle between the two pairs of detaching rollers is still so great that no tensile load or drafting acts on the fiber layer between the two pairs of detaching rollers.

[0013] In a preferred embodiment, the overhang is formed at the start of the combing process by keeping the first pair of detaching rollers stationary and the second pair of detaching rollers rotating counter to the fiber transport direction. The uncombed sliver is first guided downstream of the second pair of detaching rollers by a nipper mechanism and then, through the bell mouth, to the delivery rollers. Only then can the overhang be formed by controlling the comber. After starting the comber, the uncombed fiber sliver must be removed according to its length.

[0014] Alternatively, the second pair of detaching rollers can be stationary or only rotate slowly in the fiber transport direction, and the first pair of detaching rollers only conveys the uncombed sliver in the fiber transport direction until the second pair of detaching rollers receives the sliver and forms an overhang. In this case, the speed difference between the first and second pairs of detaching rollers is very important when the direction of rotation remains unchanged.

[0015] After the overhang is formed, the first pair of detaching rollers conveys the fiber layer in the fiber transport direction, and the second pair of detaching rollers reverses its rotation direction and also conveys the fiber layer in the fiber transport direction.

[0016] The formation and position of the overhang can preferably be improved by a device in which the overhang is formed between the upper detaching rollers or between the lower detaching rollers by means of an air flow. At combing cycles exceeding 500 times per minute, the formation of the overhang is a highly dynamic process, in which small disturbances (e.g. due to fibers sticking to the detaching rollers) can interrupt the process or the resulting fiber layer can be uneven or damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further measures that improve the invention are explained in more detail below together with the description of preferred exemplary embodiments of the invention with reference to the drawings.

[0018] In the picture:

[0019] Figure 1 shows a schematic side view of a combing head of a combing machine according to the prior art;

[0020] Figure 2a A motion diagram and a motion graph showing the detaching roller in the initial position according to the present invention;

[0021] Figure 2b A motion diagram and a motion graph showing the movement of the detaching roller during the formation of the overhang or buffer portion according to the present invention;

[0022] Figure 2c The movement diagram and movement curve diagram of the detaching roller after the overhang or buffer portion is formed according to the present invention are shown.

[0023] Then refer to Figure 1 The prior art is described and the combing machine according to the invention is described. Figures 2a to 2c In the figures, identical features are provided with the same reference numerals. It should be understood that the figures are only simplified and, in particular, not to scale. DETAILED DESCRIPTION

[0024] exist Figure 1 , a combing head 20 according to the prior art is shown, wherein at least eight combing heads are installed on a combing machine. For the sake of clarity, this embodiment shows and describes only one combing head 20, wherein, apart from the common drive unit and sliver coiler, the details shown here are installed on each of these combing heads. The combing head 20 also includes two lap transport rollers 2, 3, on which a cotton lap 1 with a winding tube is placed and from which the sliver 4 is unwound by a feed roller 7 under tensile load. The lap transport rollers 2, 3 can be driven individually or together. The design of the lap transport rollers 2, 3, whether they are only rotated without being driven, or driven individually or together, is not relevant to the present invention.

[0025] The sliver 4 is transferred to the feed roller 7 of the nipper mechanism 5. The nipper mechanism 5 can be driven back and forth via a lever via a shaft 6, which is connected to a transmission mechanism 17. In the illustrated example, the nipper mechanism 5 is in the forward position and delivers the combed fiber clump to the first pair of detaching rollers 10, 12, which follow in the direction of fiber transport. A circular comb 8 is rotatably mounted below the nipper mechanism 5. This circular comb, via its needle bar, combs out the fiber clump provided by the closed nippers. The circular comb 8 is also drive-connected to the transmission mechanism 17. A ratchet (not shown) is attached to the feed roller 7. This ratchet is gradually rotated by a pawl (also not shown) due to the reciprocating motion of the nipper mechanism 5, thereby feeding the sliver 4 to the nipper jaws for combing. During operation, the sliver 4 is continuously unwound due to the rotational motion of the lap 1 passing over the lap transport rollers 2, 3 and reaches the feed roller 7. Next, for combing out, the cotton is fed to the nip of the nipper mechanism 5 by the cotton feed roller 7 and then handed over to the first pair of detaching rollers 10, 12 in the direction of fiber transport. The fiber bundle handed over here is finally pulled through the top comb 9 and joined with the previous fiber bundle. The fiber layer 14 thus produced is handed over by the second pair of detaching rollers 11, 13 in the direction of fiber transport. The fiber layer 14 produced here is composed of the individual joined fiber bundles, which are pulled out from the bell mouth 15 by the sliver delivery roller 16 and transformed into a fiber strip 21, and are fed to the drafting mechanism (not shown) together with the fiber strips formed in the same way on the other combing heads. The fiber layer combed out by the drafting mechanism is combined into a fiber strip, the so-called combed sliver, and is transferred to the coiler to be coiled in the can.

[0026] In the prior art, the nipper mechanism 5 is moved into the forward, open position, where the detaching rollers 10, 12 rotate backward, conveying the previously combed fiber clump with its trailing end section toward the leading end section of the cotton clamped by the nippers. The detaching rollers 11, 13 perform the same movement, causing the fiber layer 14 to move back slightly. The fiber clump combed from the circular comb 8 is placed onto the trailing end section and, together with it, is drawn into the clamping position of the detaching rollers 10, 12, as the detaching rollers 10, 12 and 11, 13 change their direction of rotation again. During this rotation, the angle of rotation is approximately twice as large as during the previous backward rotation, and the fiber clump is now separated from the cotton in the nipper mechanism 5. In this case, the trailing end of the separated fiber clump is pulled through the top comb 9. In this case, the detaching rollers 10, 12, 11, 13 perform a Pilgerschrittbewegung, in which, during counter-rotation, they return the end of the fiber tuft removed in the previous combing cycle. The beginning of the fiber tuft is placed on this end, and after the direction of rotation is reversed, they are joined by the pressure of the two detaching rollers 10, 12. In each combing cycle, the detaching rollers 10, 12, 11, 13 not only have to change their direction of movement twice, but also rotate a shorter distance when returning than when advancing.

[0027] Figure 2aThe left-hand view shows the initial state of the movement of the detaching rollers 10, 12 and 11, 13 according to the invention, wherein the sliver 4 clamped by the nipper mechanism 5 enters the first pair of detaching rollers 10, 12 in the direction of fiber transport (arrow) and is arranged as a taut fiber layer 14 between the pairs of detaching rollers 10, 12 and 11, 13. This initial state is introduced once at the beginning or each time the combing machine is started. In the associated movement diagram on the right, the rotation angle of the detaching rollers is plotted as the ordinate and the time as the abscissa. For example, in the movement diagram, the combing machine is operated at 20 combing cycles per minute, so that one combing cycle lasts 3 seconds. In the value range of 1 to 3, a complete combing cycle 30 is carried out. This means that in the motion diagram, the rotational movement of the pairs of detaching rollers 10, 12 and 11, 13 in three combing cycles 30 is shown on the abscissa from 0 to 10, and the start of the combing machine with the overhang 32 or buffer formed is shown in the range from 0 to 1. With a combing cycle of 500 strokes / min, 75 combing cycles are shown in 9 seconds, with the same graph division. These combing cycles have the same curve path. The movement of the second pair of detaching rollers 11, 13 in the direction of fiber transport is drawn with a solid line, and the movement of the first pair of detaching rollers 10, 12 is drawn with a dashed line. At an abscissa value of 0, the rotation angle of the two pairs of detaching rollers 10, 12 and 11, 13 is 0°. In this initial state, the detaching rollers 10, 12 and 11, 13 are stationary.

[0028] Figure 2b The buffer or overhang 32 forming the fiber layer 14 between the pairs of detaching rollers 10, 12 and 11, 13 is shown. In this case, the first pair of detaching rollers 10, 12 is stationary and does not rotate, while the second pair of detaching rollers 11, 13 is rotated by approximately -150° in this view, so that the overhang 32 is formed because its length exceeds the total spacing of 60 mm between the detaching rollers 10, 12 and 11, 13. Figure 2bIn the embodiment shown, at a rotation angle of 150°, an overhang 32 with a length of approximately 33 mm is currently formed. This position is shown in the motion diagram at a value of 0.5 s. The size of the overhang 32 depends on the rotation angle of the detaching rollers 11, 13 and their diameters and can vary depending on the type of comber. The adjustment of the return amount of the detaching rollers 11, 13 (i.e., how much the second pair of detaching rollers 11, 13 rotates) also depends on the cotton feed rate set at the nipper mechanism 5 and can therefore be varied. In this embodiment, the outer diameter of the lower rollers 10, 11 is approximately 25 mm, and the outer diameter of the upper rollers 12, 13 is approximately 24.5 mm. In this case, only the detaching rollers 10 and 11 are driven, while the detaching rollers 12 and 13 are pressed onto the lower rollers 10 and 11 and are driven by the lower rollers through friction.

[0029] exist Figure 2c In the example, the buffer or overhang 32 is formed almost entirely by the fiber layer 14. This is sufficient to begin the combing process. The overhang 32 can reach up to 60 mm when the detaching rollers 11, 13 return 270° and thus hangs down between the detaching rollers 10, 12 and 11, 13 in the illustrated form. The length of the overhang 32 then increases briefly and reaches its maximum value at the difference in rotation angle between the first reversal point U1 of the detaching rollers 10, 12 and the continued rotational movement of the detaching rollers 11, 13. The arrow in the movement diagram precisely indicates the reversal point of the rotational movement of the detaching rollers 11, 13 or the starting point of the renewed rotational movement of the detaching rollers 10, 12, which are still stationary but now begin to rotate. The overhang 32 of the fiber layer 14 serves to compensate for the different rotational directions of the detaching roller pairs 10, 12 and 11, 13, specifically to compensate for the reversal of the first pair of detaching rollers 10, 12 in order to separate and subsequently join the fiber tufts counter to the direction of fiber transport. As can be seen from the motion diagram, the first pair of detaching rollers 10, 12 still performs a conventional pilgrim motion according to the prior art, whereas the second pair of detaching rollers 11, 13 performs a linear rotation motion at a constant speed after the direction reversal.

[0030] The rotational movement of the detaching rollers 10, 12 from the abscissa value 1s to the first reversal point U1 is in the fiber transport direction (arrow), that is, toward the detaching rollers 11, 13. This pulls the sliver 4 through the detaching rollers 10, 12 and compresses the joined fiber bundle. Starting from the first reversal point U1, the rotational direction of the detaching rollers 10, 13 is reversed, counter to the fiber transport direction. This moves the combed-out end of the fiber bundle, or in this illustration, the sliver 4, toward the nipper mechanism 5 to begin a new joining process. The rotational movement of the detaching rollers 10, 12 returns to approximately 270°, and the overhang 32 or buffer is reduced, so that the fiber layer 14 is arranged almost straight between the detaching rollers 10, 12 and 11, 13. This is indicated by the second reversal point U2, as the spacing in the movement curve between the detaching rollers 10, 12 and 11, 13 is minimal. After the second reversal point U2, the detaching rollers 10, 12 rotate again so that the fiber layer 14 is transported in the fiber transport direction (arrows), and the overhang 32 increases again until the end of the combing cycle 30, at which point the fiber clump is joined and subsequently separated from the nipper mechanism 5. The size or length of the overhang 32 is represented by the outer circumference of the detaching rollers 10, 11, using the vertical arrows between the curves of the detaching rollers 10, 12 and the detaching rollers 11, 13, as shown by the rotation angle difference 31. This motion diagram shows that the detaching rollers 10, 12, with their steep curves, experience considerable acceleration and deceleration, i.e., continuously change speed and direction of rotation (Piercing). In this exemplary embodiment, the detaching rollers 11, 13 rotate only in one direction at a constant speed during the combing process. Only at the start of the combing machine, at the beginning of combing, do the detaching rollers 11, 13 rotate backward to form the first overhang 32.

[0031] The detaching rollers 11, 13 can be operated at varying speeds while maintaining the same direction of rotation. During the return of the detaching rollers 10, 12 between the first reversal point U1 and the second reversal point U2, the detaching rollers 11, 13 can rotate more slowly, and from the second reversal point U2 onwards, they can rotate more quickly again. Ultimately, however, the embodiment disclosed here represents a more energy-efficient form of operation for the detaching rollers 11, 13.

[0032] exist Figure 2b and Figure 2c The overhang 32 or buffer of the fiber layer 14 shown here hangs downward between the detaching rollers 10 and 11. Depending on the air flow, the overhang 32 can also form between the detaching rollers 12 and 13. Air blowing from above or below between the pairs of detaching rollers 10, 12 and 11, 13 can promote the formation of the overhang, because the spacing between the pairs of detaching rollers 10, 12 and 11, 13 is relatively small.

[0033] The advantage of the present invention is that only the first pair of detaching rollers 10, 12 performs a pilgrimage motion, while the second pair of detaching rollers 11, 13 performs a constant rotational motion. This reduces the power consumption of the second pair of detaching rollers 11, 13, thereby reducing the energy consumption of the combing machine. For the second pair of detaching rollers 11, 13, water cooling of the drive motor can be omitted, and the drive motor can be designed with significantly lower drive power.

[0034] To prevent the overhang 32, which serves as a material buffer, from accumulating or being removed, the two detaching roller pairs 10, 12 and 11, 13 must execute the same final forward motion, i.e., the same final rotation angle. Depending on the design of the comber, the overhang 32 can also be designed to be smaller than in the described embodiment. This can be influenced by the spacing between the detaching roller pairs 10, 12 and 11, 13, their diameters, the feed rate, and other factors.

[0035] According to the present invention, the second pair of detaching rollers 11, 13 rotate in the same direction after the overhang 32 is formed, i.e., they rotate in a constant direction. This rotational movement can preferably be at the same speed (constant, constant rotational movement) to achieve better energy savings. However, the rotational movement of the second pair of detaching rollers 11, 13 can also vary in speed, which can have a positive impact on the formation of the overhang and make the resulting fiber layer 14 more uniform.

[0036] Reference Signs List

[0037] 1 cotton roll

[0038] 2 Lap transport rollers

[0039] 3 Lap transport rollers

[0040] 4 tampons

[0041] 5. Clamp mechanism

[0042] 6-axis

[0043] 7 Feed roller

[0044] 8. Circular Comb

[0045] 9 Top Comb

[0046] 10 separation rollers

[0047] 11 Separation roller

[0048] 12 separation rollers

[0049] 13 Separation roller

[0050] 14 fiber layers

[0051] 15 flared mouth

[0052] 16 delivery rollers

[0053] 17 Transmission mechanism

[0054] 18 motors

[0055] 19 control device

[0056] 20 combed heads

[0057] 21 fiber strips

[0058] 30 combing cycles

[0059] 31 Rotation angle difference

[0060] 32 Overhang

[0061] U1 first reversal point

[0062] U2 Second inversion point

Claims

1. A combing machine having a plurality of combing heads (20), wherein: At least one sliver (4) is unwound from a cotton roll (1) on each combing head (20) and fed to a feeding roller (7) and a nipper mechanism (5), combed noil is combed out and sucked out from the sliver (4) by means of a top comb and a circular comb, and the resulting fiber layer is transformed into a fiber strip by means of a bell mouth (15), which is stretched together with other fiber strips from other combing heads into a single fiber strip, characterized in that a first pair of detaching rollers and a second pair of detaching rollers are provided after the nipper mechanism (5), wherein the first pair of detaching rollers is configured to perform a back-and-forth rotational motion for the joining and separation process of the fiber bundle to the fiber layer (14), and the second pair of detaching rollers is configured to perform a rotational motion in a constant rotational direction, thereby forming an overhang (32) of the fiber layer (14) between the first pair of detaching rollers and the second pair of detaching rollers, the length of the overhang varying within one combing cycle.

2. The combing machine according to claim 1, characterized in that The second pair of detaching rollers is designed to transport the fiber layer (14) with a constant, unchanging rotational motion.

3. The combing machine according to claim 1, characterized in that The first pair of detaching rollers is designed to form an overhang (32) of maximum length at a first reversal point (U1), from which the pair of detaching rollers moves the fiber layer (14) back toward the nipper mechanism (5) in the opposite direction of the fiber transport direction.

4. The combing machine according to claim 1, characterized in that The first pair of detaching rollers is designed to form an overhang (32) of minimum length at a second reversal point (U2), from which the pair of detaching rollers moves the fiber layer (14) away from the nipper mechanism (5) again in the fiber transport direction.

5. The combing machine according to claim 1, characterized in that At the beginning of the combing process, the first pair of detaching rollers is stationary and the second pair of detaching rollers performs a rotational movement opposite to the fiber transport direction, thereby forming an overhang (32) between the first pair of detaching rollers and the second pair of detaching rollers.

6. The combing machine according to claim 5, characterized in that After the overhang is formed, the first pair of detaching rollers is configured to convey the fiber layer (14) in the fiber transport direction, and the second pair of detaching rollers is configured to reverse the direction of rotation and convey the fiber layer (14) in the fiber transport direction.

7. The combing machine according to claim 1, characterized in that The second pair of detaching rollers is designed to run at different rotational speeds or velocities with a constant direction of rotation.

8. The combing machine according to claim 1, characterized in that Each pair of detaching rollers is driven by means of a separate servomotor, wherein these servomotors are synchronized in order to produce the same final forward movement.

9. The combing machine according to any one of claims 1 to 8, characterized in that An overhang (32) is formed between the lower detaching roller in the first pair of detaching rollers and the lower detaching roller in the second pair of detaching rollers or between the upper detaching roller in the first pair of detaching rollers and the upper detaching roller in the second pair of detaching rollers by means of a device for conveying air between the first pair of detaching rollers and the second pair of detaching rollers.

10. Method for combing a sliver (4) using a combing machine having a plurality of combing heads (20), wherein: On each combing head (20), a cotton strip (4) is unwound from a cotton roll (1) and fed to a cotton feeding roller (7) and a nipper mechanism (5), combed noil is combed out and sucked out from the cotton strip (4) by means of a top comb and a circular comb, and the resulting fiber layer (14) is transformed into a fiber strip (21) by means of a bell mouth (15), characterized in that a first pair of detaching rollers and a second pair of detaching rollers are arranged after the nipper mechanism (5), wherein the first pair of detaching rollers detach the fiber bundle from the cotton strip (4) and join it to the fiber layer (14) by means of a back-and-forth rotational motion, wherein the second pair of detaching rollers performs a rotational motion along the fiber transport direction in a constant rotational direction, wherein the length of the overhang (32) of the fiber layer (14) formed between the first pair of detaching rollers and the second pair of detaching rollers changes within one combing cycle.

11. The method for combing according to claim 10, characterized in that The rotational movement of the second pair of detaching rollers is constant throughout all combing cycles (30).

12. The method for combing according to claim 10, characterized in that The rotational movement of the second pair of detaching rollers is non-uniform within one combing cycle (30).

13. The method for combing according to claim 10, characterized in that The overhang (32) of maximum length is formed at the first reversal point (U1) of the first pair of detaching rollers, from which the pair of detaching rollers moves the fiber layer (14) back toward the nipper mechanism (5) counter to the fiber transport direction.

14. The method for combing according to claim 10, characterized in that At the second reversal point (U2) of the first pair of detaching rollers, an overhang (32) of minimum length is formed, from which the pair of detaching rollers moves the fiber layer (14) away from the nipper mechanism (5) again in the fiber transport direction.

15. The method for combing according to claim 10, characterized in that At the beginning of the combing process, an overhang (32) is formed in that a first pair of detaching rollers is stationary and a second pair of detaching rollers performs a rotational movement counter to the fiber transport direction.

16. The method for combing according to claim 14, characterized in that As the formation of the overhang is completed, the first pair of detaching rollers conveys the fiber layer (14) in the fiber transport direction, and the second pair of detaching rollers reverses the direction of rotation and conveys the fiber layer (14) in the fiber transport direction.

17. Method for combing according to one of claims 10 to 16, characterized in that An overhang (32) is formed between the lower detaching roller in the first pair of detaching rollers and the lower detaching roller in the second pair of detaching rollers or between the upper detaching roller in the first pair of detaching rollers and the upper detaching roller in the second pair of detaching rollers by means of air flow.

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