EP3724385B1 - Drafting unit for a spinning machine comprising a compaction device, and method for compacting a fibre bundle - Google Patents

Description

The present invention relates to a drafting system with a device for compressing drafted slivers in a spinning machine and a corresponding method.

Drafting devices for spinning machines comprise at least two pairs of rollers between which a fiber structure is drawn due to the different speeds of the pairs of rollers. The pair of rollers after which the drafted fiber structure leaves the drafting system and is fed to a spinning device is referred to as the pair of exit rollers. The pair of output rollers consists of an output upper roller and an output lower roller, which form a nip through which the fiber strand is conveyed. Devices for compressing the stretched fiber structure are arranged after the exit roller pair, mechanical as well as pneumatic compression devices are used.

Generic devices are known in the prior art and are always used when a fiber sliver has to be compressed in a spinning machine after a stretching process. A corresponding device is described, for example, in EP 1 134 309 A1 . The compression device disclosed therein is of a pneumatic type and essentially consists of a suction shoe and a perforated transport means. In this case, a pressure element is applied to one of the rollers of the pair of output rollers, which forms a second nip point with the roller next to the nip point between the output top roller and the output bottom roller. The compression zone is located between the two clamping points and delimited by the suction shoe. On a Design and arrangement of the opening in the suction shoe is the EP 1 134 309 A1 not a.

A disadvantage of the proposed device is that in the compression zone the individual fibers of the fiber structure are to be bound into it and for this purpose the fibers are moved in their entire length without being held via the perforated transport means transversely to the conveying direction with the aid of an air flow, which can also lead to a loss of the stretching of the fiber structure determined by the drafting system. The fiber structure is conveyed by the transport means, the second clamping point only serves to prevent a yarn twist of the fiber structure from being able to propagate into the compression zone.

From the CH 694 021 A5 a method for compressing a drafted fiber structure in a compression zone following a pair of output rollers of a drafting system is known. The fiber structure is transported through the compression zone by means of a perforated, vacuum-extracted conveyor belt. When the fiber strand reaches the compression zone, it moves in the same direction as the means of transport. A sufficient quantity of the fibers in the fiber structure is still clamped by the pair of exit rollers during compaction. As a result, the front ends of the fibers of the fiber structure to be compressed do not dip into the perforations of the conveyor belt and thus lead to blockages. Due to the large distance between the clamping points and the great length of the suction slot below the conveyor belt, fibers are moved transversely to their longitudinal alignment and compress the entire fiber structure.

The object of the present invention is to achieve compression of the fiber structure by bundling the fibers and to create a device for this purpose which is characterized in that fibers are nestled against the fiber structure without moving the individual fibers transversely to the direction of travel via a transport means.

The object is achieved by a drafting system and a method with the features of the independent patent claims.

Proposed is a drafting system for a spinning machine for drafting a fiber structure with at least a first pair of rollers consisting of an upper roller and a lower roller, and with a second pair of rollers consisting of an output upper roller and an output lower roller, with a first nip point being formed by the first pair of rollers and a second nip point is defined by the second pair of rollers. The first nipping point and the second nipping point form a drafting field plane, which is traversed by the fiber structure in a running direction from the first nipping point to the second nipping point. The drafting system comprises a fiber compression zone downstream of the pair of output rollers for compression of the drafted fiber bundle, which has a pneumatic compression device with a fiber bundling zone and with a suction pipe wrapped around by a screen element and capable of being sucked out. The fiber bundling zone is delimited by the second nip and a third nip, the third nip being formed by the exit top roller and the screen element. The suction pipe has a slit-shaped suction opening with a length of 2.0 mm to 5.0 mm, which is arranged in the fiber bundling zone, the slit-shaped suction opening in the suction pipe being arranged from one end of the suction pipe facing the second clamping point in the direction of the third clamping point .

The ambient air sucked in through the suction opening means that individual fibers protruding from the fiber structure are moved to the suction opening and the fiber structure is thus bundled. Compared to conventional pneumatic compaction, in which the fiber structure is moved on a screen element transversely to its running direction and the fibers are thus pushed together, with fiber bundling only fiber parts or fiber ends protruding from the fiber structure are brought up to the fiber structure without the fiber structure being deflected from its running direction . In such a fiber bundling method, the fiber ends are guided to the fiber structure by a pneumatic suction flow and applied to the fiber structure in the third clamping point. The suction tube and thus the screen element are advantageously brought as close as possible to the second clamping point. As a result, fiber parts or fiber ends that protrude from the fiber structure are caught by the air flow immediately after leaving the second clamping point and placed against the fiber structure.

A distance from the second nip point to the third nip point along a surface of the output top roller is less than an average staple length of the fiber structure to be drawn. As a result, most of the fibers contained in the fiber structure are always held either in the second clamping point or in the third clamping point. The fiber bundle is transported in a defined manner from the second to the third clamping point. In the fiber bundling zone, only the fiber parts protruding from the fiber structure are brought into the fiber strand. The air flow ensures that fiber parts or fiber ends protruding from the fiber structure are guided to the fiber structure, with the fiber structure itself not being transported directly through the screen element, but instead passing through the fiber bundling zone held by the clamping points. As a result, the so-called hairiness of the fiber structure is eliminated and the hair is bound into the fiber structure. The constant clamping of at least one fiber end also prevents the fiber structure from losing or partially losing the stretching applied in the drafting system while passing through the fiber bundling zone.

The screen element is also driven by the output top roller through the third clamping point. The frictional drive of the screen element creates a slight slip, so that the screen element has a lower speed than the output roller pair. This circumstance also contributes to the fact that a bundling of the fiber structure or an integration of protruding fiber ends in the fiber structure becomes possible.

The suction opening is advantageously arranged in a flat surface of the suction tube in the fiber bundling zone. As an alternative to this, the suction opening can be arranged in a curved surface of the suction tube in the fiber bundling zone, the curvature being less than 0.04 1/mm. Such a design of the suction pipe in the fiber bundling zone minimizes the deflection of the fiber structure between the second and third clamping point.

The flat surface of the suction pipe is preferably inclined at an angle of 45° to 75°, preferably 62° to 65°, to a perpendicular to the direction of travel with respect to the plane of the drawing field. Correspondingly, with a curved surface of the suction tube, a tangent in the third clamping point on the curved surface of the suction tube is inclined to a perpendicular to the direction of travel by an angle of 45° to 75°, preferably 62° to 65° to the plane of the stretching field. The fiber bundle moves between the second and third clamping point through the fiber bundling zone over the screen element guided on the suction pipe. Due to the difference in speed between the second and third clamping point, the fiber bundle sags slightly. That means the fiber structure follows not exactly on the surface of the output top roller but moves in the direction of the suction pipe after leaving the second nip. With a corresponding inclination of the surface of the suction tube, this movement is absorbed in such a way that the protruding fiber ends can rest against the fiber structure due to the air flow.

Advantageously, a radial distance between the output bottom roller and the screen element lying against the suction pipe is 0.4 mm to 2.0 mm. By arranging the suction pipe or screen element as close as possible to the bottom exit roller, the fiber bundling zone, which is formed by the surfaces of the bottom exit roller and the top exit roller and the screen element or suction pipe, is closed in one plane. The ambient air sucked in through the suction opening is thus sucked in transversely to the running direction of the fiber structure. This can increase the bundling effect. In addition, the influence of the air flow caused by the rapidly rotating lower exit roller on the running direction of the fiber structure is deflected.

Furthermore, it is advantageous if the slit-shaped suction opening is arranged in a longitudinal extent inclined within ±15 degrees to the running direction. The arrangement of the slit-shaped suction opening in the running direction of the fiber structure is particularly preferred. The bundling of the fibers should not take place through a movement of the fiber structure transversely to its running direction. Only the fibers or fiber ends protruding from the fiber structure should be nestled against the fiber structure. A movement of the entire fiber structure transverse to the running direction is not necessary for this.

Advantageously, the suction pipe protrudes less than 5 mm beyond the third clamping point in a running direction of the sieve element. The shortest possible guidance of the fiber structure through the screen element after the third Terminal point results in advantages for the geometric arrangement of the subsequent spinning device. This also minimizes the risk of the fiber structure shifting laterally on the sieve element and thus damage to the previously bundled fiber structure.

Preferably, the top exit roller has a curtain opposite the bottom exit roller in the drafting field plane, viewed in the direction of travel. It is also advantageous if the curtain, measured in the drafting zone, is between 2 mm and 15 mm and/or the ratio of the diameter of the top roller to the diameter of the bottom roller is 1.4 to 2.5, preferably 1.79 for one diameter the output top roll of 50 mm and a diameter of the output bottom roll of 28 mm. The curtain of the upper exit roller opposite the lower exit roller enables the third nip to be located close to the second nip. The enlargement of the upper exit roller compared to the lower exit roller improves the spatial arrangement of the fiber bundling zone.

Furthermore, a method for compressing a fiber structure consisting of individual fibers in a spinning machine is proposed, with at least a first pair of rollers consisting of an upper roller and a lower roller, and with a second pair of rollers consisting of an output upper roller and an output lower roller, with a first nip point being formed by the first pair of rollers and a second nip point can be defined by the second pair of rollers, and the first nip point and the second nip point form a drafting field plane through which the fiber strand runs in a direction from the first nip point to the second nip point, and with a fiber compression zone downstream of the pair of output rollers for the compression of the stretched fiber structure, which has a pneumatic compression device with a fiber bundling zone and with a looped by a screen element and having a suckable suction tube, wherein the fiber bundling zone is delimited by the second nip and a third nip, wherein the third nip is formed by the exit top roller and the screen element. After the second clamping point, the fiber structure is guided through the sieve element via the suction opening to the third clamping point and the individual fibers are caught by the third clamping point before leaving the second clamping point, with fiber ends protruding from the fiber structure being laid against the fiber structure when the suction opening is passed. It is advantageous if the majority of the fibers are not transported from the second clamping point to the third clamping point by the sieve element without being clamped. Due to the arrangement of the suction opening immediately after the second clamping point, the protruding fiber ends are caught by the air flow after leaving the second clamping point and the fiber structure is created, while the front end of the corresponding fiber is already held by the third clamping point.

Preferably, by tilting the screen element against the running direction towards the drawing field plane, the fiber ends move through the free space in the fiber bundling zone after leaving the second clamping point before they meet the screen element. This makes it possible for the fiber ends to be moved freely from the fiber structure and therefore only small forces are required to apply protruding fibers or fiber ends to the fiber structure.

Figur 1

eine schematische Darstellung eines Längsschnittes einer Spinn-maschine nach dem Stand der Technik,

Figur 2

eine schematische Darstellung eines Längsschnittes einer erfindungsgemäßen Ausführungsform der Verdichtungsvorrichtung des Streckwerks und

Figur 3

eine schematische Darstellung einer Draufsicht in Richtung X nach der Figur 2.

Further advantages of the invention are described in the following exemplary embodiments. Show it:

figure 1

a schematic representation of a longitudinal section of a spinning machine according to the prior art,

figure 2

a schematic representation of a longitudinal section of an embodiment according to the invention of the compression device of the drafting system and

figure 3

a schematic representation of a plan view in direction X after the figure 2 .

figure 1 shows a schematic representation of a longitudinal section of a spinning machine according to the prior art, in particular a ring spinning machine. Shown are examples of individual components of the spinning machine, namely a drafting system 2 and a spinning device 14. The drafting system 2 consists of three pairs of rollers, an input roller pair 5, a pair of apron rollers 64 and an output roller pair 9. The pair of apron rollers 6 is formed by an upper roller 7 and a lower roller 8 The exit roller pair 9 is formed by an exit upper roller 10 and an exit lower roller 11. The two rollers of a roller pair are pressed against each other and form a nip at their point of contact, with the nip point K1 being formed by the upper roller 7 and the lower roller 8 and the nip point K2 being formed by the pair of exit rollers 9 is formed between the output top roller 10 and the output bottom roller 11. The fiber structure 1 entering the drafting system 2 runs through the drafting system 2 in the running direction 3 and is thereby clamped between the rollers of the roller pairs 3, 4 and 5 by the clamping points. Due to the different speeds of the roller pairs 3, 4 and 5, the fiber structure 1 is stretched. In this case, the clamping points K1 and K2 form a stretching field plane 4 . During the drafting, the fiber structure 1 is transported through the drafting system 2 at the same time. After leaving the drafting system 2, the drafted fiber structure 12 reaches a thread guide 13 and is then conveyed to the spinning device 14. The spinning device 14 consists essentially of a ring rail 18, which carries the spinning ring 16, and a spindle rail 19, on which the bobbin 17 is attached is. The fiber bandage 12 reaches the bobbin 17 via a runner 15. To spin the fiber structure 12, the bobbin 17 is set in rotation, with the result that the runner 15 is also set in rotation by the fiber structure 12 on the spinning ring 16. Due to the different rotational speed of the bobbin 17 and the rotor 15, the fiber structure 12 is rotated and a yarn is thereby formed which is wound onto the bobbin 17 by moving the ring rail 18 up and down.

figure 2 shows a schematic representation of a longitudinal section of an embodiment according to the invention of a compression device of the drafting system. The apron roller pair 6, consisting of an upper roller 7 and a lower roller 8 forms a first nip K1. The output roller pair 9, consisting of the output lower roller 10 and the output upper roller 11 forms a second nip K2. The fiber strand 1 to be drawn is guided in the running direction 3 by the pairs of rollers 6 and 9 through the drafting system. The pairs of rollers 6 and 9 form a drawing zone plane 4 through their clamping points K1 and K2. The upper exit roller 10 has a curtain A of preferably 10 mm in its arrangement opposite the lower exit roller 11 in the drafting zone plane 4 seen in the running direction 3 . In addition, the upper exit roller 10 has a diameter E which is greater than the diameter F of the lower exit roller 11, with a ratio of the diameter E of the upper exit roller 10 to the diameter F of the lower exit roller 11 preferably being 1.79. Because of these specific geometric relationships between the output top roller 10 and the output bottom roller 11, ideal conditions for the formation of a fiber bundling zone 20 are created.

A suction pipe 21 is arranged downstream of the pair of output rollers 9 . The suction tube 21 is wrapped by a sieve element 22 which is designed as an endless belt and is guided over a deflection 25 . Im shown In the exemplary embodiment, the screen element 22 forms a third clamping point K3 for the drawn fiber structure with the output top roller 10 . The shape of the intake manifold 21 is shown as a triangle by way of example.

Between the second nip point K2 and the third nip point K3, the drafted fiber strand passes through the fiber bundling zone 20. A nip length B is formed from the second nip point K2 to the third nip point K3 along a surface of the output top roller 10, which is less than an average staple length of the fiber structure 1 to be drawn. The suction pipe 21 has a suction opening 24 in this fiber bundling zone 20. The suction opening 24 is formed as a slit-shaped opening in the wall of the suction pipe 21. The suction pipe 21 is connected to a vacuum source (not shown), which causes air to be sucked out of the fiber bundling zone 20 via the suction opening 24 and thus also through the screen element 22 sliding over the suction opening 24 . The resulting air flow pulls the stretched fiber structure towards the screen element 22, with individual fibers or fiber parts protruding from the stretched fiber structure being conveyed to the suction opening 24 and thus clinging to the stretched fiber structure. During this clinging process, the individual fibers of the fiber structure are mostly held either by the second clamping point K2 or the third clamping point K3 due to the short clamping length B, so that only the free ends of the fibers are tied into the fiber structure. The arrangement of the slit-shaped suction opening 24 from one end of the suction tube 21 facing the second clamping point K2 in the direction of the third clamping point K3 also causes the fiber ends to be immediately gripped by the suction effect after leaving the second clamping point K2.

Furthermore, the suction tube 21 has a flat surface towards the fiber bundling zone 20 which is inclined at an angle α of 62° towards the drawing field plane 4 with respect to a perpendicular to the drawing field plane 4 . The screen element 22 which runs around the suction tube 21 is arranged at a distance C of 1.0 mm from the bottom roller 11 at the exit. This forms a fiber bundling zone 20 closed by the upper exit roller 10, the lower exit roller 11 and the suction pipe 21, so that the majority of the ambient air sucked in through the suction opening 24 is sucked in from the side, i.e. transversely to the direction of movement of the fiber structure, into the fiber bundling zone 20.

The screen element 22 is set in motion by the output top roller 10 via the resulting frictional force in the third clamping point K3, as a result of which the drafted fiber structure is fed from the fiber bundling zone 20 to the third clamping point K3. The compacted fiber strand 23 then leaves the screen element 22, and the aim is for the suction pipe 21 to overhang as little as possible beyond the third clamping point K3. The compacted fiber strand 23 is transferred to the spinning device 14 or to the thread guide 13 of the spinning machine that is upstream of the spinning device 14 (see FIG figure 1 ). The geometry of the suction pipe 21 makes it possible to maintain the inlet geometry necessary for the spinning device 14 to function properly, despite the additional arrangement of the compression device.

figure 3 shows a schematic representation of a plan view in direction X according to FIG figure 2 . In the illustration, the output top roller 10 is indicated, so that the screen element 22 running around the suction pipe 21 can be seen. A slit-shaped suction opening 24 with a length L is provided in the suction pipe 21 located below the sieve element 22 . The fiber structure 23 running over the screen element 22 shows protruding fiber ends in the area the end of the suction opening 24 which faces the bottom roller 11 at the exit. In the course of the suction opening 24 in the direction of travel 3 , the protruding fiber ends are applied to the fiber structure 23 by the action of the ambient air which is directed towards the suction opening 24 transversely to the direction of travel 3 .

Reference List

1

fiber bandage

2

drafting system

3

running direction

4

stretching plane

5

pair of input rollers

6

pair of apron rollers

7

top roller

8th

bottom roller

9

output roller pair

10

output top roller

11

exit bottom roller

12

Stretched fiber structure

13

thread guide

14

spinning device

15

runner

16

spinning ring

17

Kitchen sink

18

ring bank

19

spindle bank

20

fiber bundling zone

21

intake manifold

22

screen element

23

Compressed fiber structure

24

suction port

25

deflection

a

Angle of inclination of the intake manifold

A

Curtain exit top roller

B

distance between clamping points

C

Distance from bottom roller to suction tube

E

Diameter of exit top roller

f

Output bottom roll diameter

K1

First clamping point

K2

Second clamping point

K3

Third clamping point

L

Length slit-shaped suction opening

Claims (14)

1. A drafting system (2) for a spinning machine for drafting a fiber strand (1) having at least one first roller pair (6) consisting of a top roller (7) and a bottom roller (8) and having a second roller pair (9) consisting of a top output roller (10) and a bottom output roller (11), a first clamping point (K1) being defined by the first roller pair (6) and a second clamping point (K2) being defined by the second roller pair (9), and the first clamping point (K1) and the second clamping point (K2) implementing a drafting zone plane (4) transited by the fiber strand (1) in a running direction (3) from the first clamping point (K1) to the second clamping point (K2), and having a fiber condensing zone downstream of the output roller pair (9) for condensing the drafted fiber strand, comprising a pneumatic condensing device having a fiber bundling zone (20) and having a suctionable suction tube (21) enlaced by a lattice element (22), the fiber bundling zone (20) being delimited by the second clamping point (K2) and a third clamping point (K3), the third clamping point (K3) being defined by the top output roller (10) and the lattice element (22), characterized in that the suction tube (21) comprises a slit-shaped suction opening (24) having a length (L) of 2.0 mm to 5.0 mm, being disposed in the fiber bundling zone (20), wherein the slit-shaped suction opening (24) in the suction tube (21) is disposed in the direction of the third clamping point (K3) from an end of the suction tube (21) facing the second clamping point (K2), wherein a spacing (B) from the second clamping point (K2) to the third clamping point (K3) along a surface of the top output roller (10) is such that the individual fibers of the fiber strand (1) provided for drafting are captured by the third clamping point (K3) before leaving the second clamping point (K2) and wherein fiber ends protruding from the fiber strand (1) are applied to the fiber strand (1) when passing across the suction opening (24).
2. The drafting system (2) according to claim 1, characterized in that the suction opening (24) is disposed in a flat surface of the suction tube (21) in the fiber bundling zone (20).
3. The drafting system (2) according to claim 1, characterized in that the suction opening (24) is disposed in a curved surface of the suction tube (21) in the fiber bundling zone (20), wherein the curvature is less than 0.04 (1/mm).
4. The drafting system (2) according to claim 2, characterized in that the flat surface of the suction tube (21) is inclined by an angle (α) of 45° to 75° toward the drafting zone plane (4) relative to a perpendicular to the running direction (3).
5. The drafting system (2) according to claim 3, characterized in that a tangent at the third clamping point (K3) to the curved surface of the suction tube (21) is inclined toward the drafting zone plane (4) by an angle (α) of 45° to 75° relative to a perpendicular to the running direction (3).
6. The drafting system (2) according to any one or more of the preceding claims, characterized in that a radial spacing (C) between the bottom output roller (11) and the lattice element (22) contacting the suction tube (21) is 0.4 mm to 2.0 mm.
7. The drafting system (2) according to any one or more of the preceding claims, characterized in that the slit-shaped suction opening (24) is inclined to the running direction (3) in a longitudinal extent within ± 15 degrees of angle.
8. The drafting system (2) according to any one or more of the preceding claims, characterized in that the suction tube (21) protrudes less than 5 mm past the third clamping point (K3) in a running direction of the lattice element (22).
9. The drafting system (2) according to any one or more of the preceding claims, characterized in that the top output roller (10) comprises an offset (A) relative to the bottom output roller (11) in the drafting zone plane (4) as seen in the running direction.
10. The drafting system (2) according to claim 9, characterized in that the offset (A) as measured in the drafting zone plane (4) is between 2 mm and 15 mm and/or the ratio of the diameter (E) of the top output roller (10) to the diameter (F) of the bottom output roller (11) is between 1.4 and 2.5.
11. A ring spinning machine characterized in that at least one drafting system (2) according to any one of the claims 1 through 10 is provided.
12. A method for condensing a fiber strand (1) consisting of individual fibers in a spinning machine having at least one first roller pair (6) consisting of a top roller (7) and a bottom roller (8) and having a second roller pair (9) consisting of a top output roller (10) and a bottom output roller (11), a first clamping point (K1) being defined by the first roller pair (6) and a second clamping point (K2) being defined by the second roller pair (9), and the first clamping point (K1) and the second clamping point (K2) implementing a drafting zone plane (4) transited by the fiber strand (1) in a running direction (3) from the first clamping point (K1) to the second clamping point (K2), and having a fiber condensing zone downstream of the output roller pair (9) for condensing the drafted fiber strand, comprising a pneumatic condensing device having a fiber bundling zone (20) and having a suctionable suction tube (21) having a suction opening (24) and being enlaced by a lattice element (22), the fiber bundling zone (20) being delimited by the second clamping point (K2) and a third clamping point (K3), the third clamping point (K3) being formed by the top output roller (10) and the lattice element (22), characterized in that the suction tube (21) comprises a slit-shaped suction opening (24) having a length (L) of 2.0 mm to 5.0 mm and the fiber strand being guided through the lattice element (22) downstream of the second clamping point (K2) across the suction opening (24) to the third clamping point (K3), and that the individual fibers are captured by the third clamping point (K3) before leaving the second clamping point (K2), wherein fiber ends protruding from the fiber strand are applied to the fiber strand when passing across the suction opening (24).
13. The method according to claim 12, characterized in that the majority of fibers are not transported free of clamping by the lattice element (22) from the second clamping point (K2) to the third clamping point (K3).
14. The method according to claim 12 or 13, characterized in that the fiber ends are displaced through the free space in the fiber bundling zone (20) before impacting the lattice element (22) after leaving the second clamping point (K2) due to an inclination (α) of the lattice element (22) as seen opposite the running direction (3) against the drafting zone plane (4).

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