EP3978661B1 - Screen apron - Google Patents

Description

The present invention relates to an endless screen belt for transporting a fiber structure to be compressed over a suction slot of a compression device of a spinning machine, which has a plurality of adjacent longitudinal filaments in the circumferential direction and a plurality of adjacent transverse filaments transversely to the circumferential direction, wherein there are gaps between adjacent longitudinal filaments and adjacent transverse filaments, which form free surfaces so that the screen belt is permeable to air.

A fiber structure stretched in a drafting system leaves the drafting system with a certain width and is then twisted into a thread with a relatively small diameter. The thread contains edge fibers that are not properly integrated into the twisted thread and thus contribute little to the strength of the thread. To increase the strength of the thread, a compression zone is arranged downstream of the drafting zone of the drafting system. In the compression zone, the fibers are compressed together, making the fiber structure narrower. The resulting thread is then more uniform, stronger and less hairy.

One of the ways to compress the fiber structure is a suction pipe that is wrapped around an endless, air-permeable sieve belt. The sieve belt slides over a suction slot in the suction pipe that is arranged at an angle to the running direction of the fiber structure. The running direction of the fiber structure essentially corresponds to the circumferential direction of the sieve belt. The fiber structure is transported on the sieve belt and compressed along a suction edge of the suction slot.

From the EN 10 104 182 A1 An air-permeable conveyor belt of this type is known for transporting a fiber structure to be compressed over a suction slot in a compression zone of a spinning machine. The conveyor belt is designed as a fabric belt and consists of longitudinal threads running in the direction of transport of the fiber structure and transverse threads running perpendicular to the direction of transport of the fiber structure. The clear distance between two longitudinal threads is greater than the clear distance between two transverse threads. The aim is to create a conveyor belt which, on the one hand, ensures a sufficiently large air flow and, on the other hand, prevents the suction of lost fibers as far as possible.

The disadvantage of this screen belt is that it wears out relatively quickly over the course of its use. In addition, the mobility of the fibers on the surface of the screen belt is limited in the transverse direction. Compressing the fiber structure at the suction edge can therefore be difficult.

From the CN111254529A A top apron of a drafting system of a spinning machine is known. This top apron has an inner ring layer and an outer ring layer that are inseparably connected to one another. The surface of the outer ring layer has an uneven texture, and the shape of the uneven texture is grainy and/or wavy. The properties of such a top apron of a drafting system that must be fulfilled are the opposite of the properties of a screen apron. While the fibers must be held in the top apron of the drafting system, they must be moved transversely to their longitudinal axis in a screen apron. In addition, the top aprons of a drafting system are not permeable to air.

The JP 2009185436 A describes a double apron drafting system with upper aprons and/or lower aprons as guide aprons, which are made of a fabric whose warp threads and weft threads each have a thickness of no more than 0.2 mm and whose outside is covered with a layer of rubber-elastic material that has a thickness of no more than 0.3 mm. These aprons are also not permeable to air and must guide the fibers so that the fibers do not change their position. In contrast, with a sieve apron, the fibers are moved transversely to their longitudinal direction and the sieve apron is vacuumed in order to give the fibers a hold on the sieve apron.

The object of the present invention is therefore to create a sieve belt which is wear-resistant and yet allows the fiber structure on the sieve belt to be moved very well transversely to the circumferential direction of the sieve belt.

The problem is solved by a sieve belt with the features of patent claim 1.

A sieve belt has an endless circumference for transporting a fiber structure to be compressed over a suction slot of a compression device of a spinning machine. A large number of adjacent longitudinal filaments are arranged in the circumferential direction of the sieve belt and a large number of adjacent transverse filaments are arranged transversely to the circumferential direction of the sieve belt. There are gaps between adjacent longitudinal filaments and adjacent transverse filaments, which form free surfaces, so-called sieve surfaces, so that the sieve belt is permeable to air. These gaps can also be called mesh width. According to the invention, the longitudinal filaments have a thinner cross-section than the transverse filaments.

In the screen apron according to the invention, the use of finer longitudinal filaments, which will generally be the weft filaments, and stronger transverse filaments, which will generally be the warp filaments, leads to significant advantages. With the stronger transverse filament, the screen apron has a larger wear volume. The reason for this is that the stronger transverse filament, which lies transversely to the circumferential direction of the screen apron or transversely to the transport direction of the fiber structure, rests on the suction pipe, while the longitudinal filament is so tensioned that it is not pressed onto the suction pipe even under the load of a pressure roller. Wear therefore occurs first on the thicker transverse filament. This increases possible wear times and the service life of the screen apron is extended accordingly. The finer longitudinal filament also maintains the necessary low bending stiffness of the screen apron. The screen apron continues to run around the small radii of the suction pipe without a gap. Another advantage is that the fibers lie mainly on the back of the stronger and more closely spaced transverse filaments. This makes it easier for the fibers of the fiber structure to be moved across the spinning direction and thus more intensively compressed. If anything, the fibers are less hindered in their transverse movement by the longitudinal filaments because of their greater distance.

A particular advantage of the invention is that the thinner longitudinal filament touches the suction pipe, if at all, with reduced contact force and only after the cross filaments have become worn after a certain period of operation. A screen belt consisting of both reinforced cross and reinforced longitudinal filaments could be advantageous in terms of wear, but it would have problems with the transverse displacement of the fibers and with the flexibility of the sieve belt in the circumferential direction and thus the gap-free nature between the suction pipe and the sieve belt, disadvantages which are avoided with the sieve belt according to the invention.

A particularly advantageous design of the screen apron is when the longitudinal filaments are arranged within areas formed by turning points of the transverse filaments. A type of covering surface on the screen apron is thus spanned by the transverse filaments. The thinner longitudinal filaments mean that the fabric can be manufactured in such a way that the longitudinal filaments, at least when new, are always at most at the level of the transverse filaments, but preferably below the transverse filaments. The longitudinal filaments are therefore not exposed to the transverse filaments. They are preferably below the transverse filaments, but at most in the same covering surface as the transverse filaments. They are thus largely protected from wear by the thicker transverse filaments. The screen apron therefore remains usable for longer and retains the property of good transverse mobility of the fibers on the screen apron for a long time.

It is advantageous if the longitudinal filaments meander less than the transverse filaments. This can also be referred to as incorporation or crimping. Incorporation is the ratio of the length of a filament incorporated into the fabric to its length when stretched. The smaller the incorporation, the more stretched the filaments are in the fabric. In this case, this means that the particularly advantageous screen apron has a smaller incorporation of the longitudinal filaments than the transverse filaments. The distance between the turning points of the longitudinal filaments is therefore smaller than the distance between the turning points of the transverse filaments. If the longitudinal filament is the weft filament, the screen apron is woven with a low weft incorporation. The longitudinal filament or weft filament meanders only very slightly or, if it runs essentially straight, hardly at all through the transverse filaments or the warp filaments. Minimal meandering is advantageous in order to obtain better slip resistance of the fabric.

It is also an advantage if the longitudinal filaments run essentially in a straight line. The longitudinal filaments are therefore not or hardly incorporated into the fabric. Although the stability of the transverse filaments relative to one another is reduced, the wear resistance and the ability of the fibers to be moved very easily transversely on the screen belt is improved. The reason for this is that the time until the transverse filaments are worn to the point where they are the same height as the thinner longitudinal filaments, or until the screen belt tears, is extended.

Furthermore, it is advantageous if the distance between adjacent longitudinal filaments is greater than the distance between adjacent transverse filaments. The close distance between the transverse filaments is compensated for in terms of the mesh size by the larger distance between the longitudinal filaments. Conversely, the free screen surface does not become too large due to the closer arrangement of the transverse filaments. If the screen surface is too large, the fibers would be sucked through more. It is therefore advantageous to create a screen surface which, on the one hand, ensures that the fibers adhere sufficiently to the screen belt, but on the other hand still allows the fibers to be moved sideways and, if possible, no fibers are sucked through the screen belt.

It is therefore advantageous if the free area between the longitudinal filaments and the transverse filaments, i.e. the screen area, is between 20% and 60%, preferably between 30% and 50% of the screen apron area. The suitable size of the screen area depends in particular on the type and size of the fibers of the fiber structure to be compacted.

It is also extremely advantageous if the cross filaments have a diameter that is between 10% and 80% larger than the diameter of the longitudinal filaments. Here too, the suitable diameter of the filaments depends, among other things, on the type and size of the fibers of the fiber structure to be compacted. In addition, the service life, i.e. the duration of the wear resistance of the screen belt, and the ability of the fibers to be moved can be influenced by this.

It is particularly advantageous if the screen belt has a plain weave or a twill weave. This makes the screen belt easy to manufacture. With a plain weave, the dimensional stability of the fabric is very good on the one hand and the adaptation to the suction pipe without a gap is very good on the other. This creates very good resistance to displacement and running stability. With the twill weave, running directions of the screen belt or different sides of the screen belt can be produced.

It also has advantages if the screen belt is antistatic. This can be done by coating the screen belt with an antistatic coating, for example with carbon. However, all or some of the filaments can also be made of antistatic material and woven into the screen belt.

It is particularly advantageous if imaginary surfaces that rest on the turning points of the transverse filaments are spaced apart from turning points of the longitudinal filaments, whereby the thinner longitudinal filaments are arranged at a distance between these surfaces. This creates a structure on the surface of the screen aprons that is particularly advantageous for the movement of the fibers during the compaction of the fiber band.

Figur 1

eine Seitenansicht auf ein Streckwerk einer Spinnmaschine mit einer Verdichtungseinrichtung,

Figur 2

eine Draufsicht auf eine Verdichtungseinrichtung mit einem Siebriemchen,

Figur 3

einen vergrößerten Ausschnitt auf ein Gewebe eines Siebriemchens,

Figur 4a

einen Schnitt durch ein Gewebe eines Siebriemchens in Umfangsrichtung des Siebriemchens und

Figur 4b

einen Schnitt durch ein Gewebe eines Siebriemchens quer zur Umfangsrichtung des Siebriemchens.

Further advantages of the invention are described in the following embodiments. It shows:

Figure 1

a side view of a drafting system of a spinning machine with a compacting device,

Figure 2

a top view of a compaction device with a sieve belt,

Figure 3

an enlarged section of a mesh of a sieve strap,

Figure 4a

a section through a fabric of a sieve belt in the circumferential direction of the sieve belt and

Figure 4b

a section through a fabric of a sieve belt transverse to the circumferential direction of the sieve belt.

In the following description of the embodiments, the same reference numerals are used for features that are identical and/or at least comparable in their design and/or mode of operation. Unless these are explained in detail again, their design and/or mode of operation corresponds to the design and mode of operation of the features already described above.

Figure 1 shows a schematic representation of a side view of a section of a drafting system 1 of a spinning machine, in particular a ring spinning machine with a compression device 2. The drafting system 1 comprises a pair of feed rollers 3, a pair of draft rollers 4 and a pair of output rollers 5. Each of the roller pairs 3, 4 and 5 is formed by an upper roller and a lower roller or a lower cylinder. The two Rollers of each roller pair 3, 4 and 5 are pressed against each other and form a clamping point K1, K2 and K3 at their point of contact for a fiber bundle 6 running into the drafting system 1, whereby the clamping point K1 is formed by the feed roller pair 3, the clamping point K2 by the drafting roller pair 4 and the clamping point K3 by the output roller pair 5. A thread clamping point K4 is formed by a pressure roller 7 which presses against a suction pipe 8 which can be suctioned. Due to the different speeds of the roller pairs 3, 4 and 5, the fiber bundle 6 is stretched. During the stretching, the fiber bundle 6 is simultaneously transported through the drafting system 1. After leaving the drafting system 1, the stretched fiber band 1 reaches the compression device 2 in which it is compressed.

The compression device 2 has a suction slot 9 between the clamping point K3 and the thread clamping point K4 on the suction pipe 8, on the edge of which the fibers of the fiber structure 6 are bundled or compressed. The stretched fiber structure 6 is transported in the transport direction T via the suction pipe 8 by means of a screen belt 10, which wraps around the suction pipe 8 and a deflection rod 11 in the circumferential direction U. The screen belt 10 is driven by the pressure roller 7. The pressure roller 7 is in turn set in rotation by means of elements not shown via the upper roller of the output roller pair 5. Negative pressure, which is present in the suction pipe 8 and sucks in the fiber structure 6 via the suction slot 9, also acts through the screen belt 10, which is permeable to air.

After the compacting device 2, the fiber structure 6, which forms a thread 12 after the clamping point K4, reaches a thread guide 13 and is guided further to a spinning device (not shown).

To open the drafting system 1, the upper rollers can be lifted from the lower rollers of the roller pairs 3, 4 and 5 as well as the pressure roller 7. For this purpose and to close the drafting system 1 again, a loading arm 14, to which the upper rollers and the pressure roller 7 are attached in a known manner, is moved about a pivot point D in the direction of arrow P.

Figure 2 shows a top view of the compaction device 2 with the sieve belt 10. The fiber structure 6 is transported together with the rotating sieve belt 10 in the circumferential direction U of the sieve belt or in the transport direction T of the fiber structure 6 via the suction pipe 8. The sieve belt 10 rests on the suction pipe 8 and slides over it. The sieve belt 10 is driven, as can be seen from Figure 1 visible, by the pressure roller 7, which is itself driven. The fiber structure 6 is sucked in the area of the suction slot 9 and compressed at an edge of the suction slot 9, which is inclined in relation to the transport direction T of the fiber structure 6. For this purpose, the screen belt 10 is permeable to air, so that the negative pressure in the suction pipe 8 can act on the fibers of the fiber structure 6 through the screen belt 10. In particular, the sliding contact of the screen belt 10 on the suction pipe 8 causes wear on the underside of the screen belt 10.

Figure 3 shows an enlarged detail of a fabric of a screen apron 10 according to the invention in plain weave. The fabric of the screen apron 10 has adjacent longitudinal filaments 15 and adjacent transverse filaments 16. Fibers 17 of the fiber structure 6 are shown schematically lying on the screen apron 10. The fiber structure 6 accordingly lies on the screen apron 10 in the transport direction T of the fiber structure 6. The fibers 17 are aligned lengthwise in the circumferential direction U of the screen apron 10.

Longitudinal filaments 15 and transverse filaments 16 are spaced apart from one another so that the sieve belt 10 is permeable to air by means of the resulting meshes. A distance AL between the longitudinal filaments 15 is greater than a distance AQ between the transverse filaments 16. The distance AL can be, for example, about 400 µm and the distance AQ, for example, 100 µm. A sieve surface 18 created in this way has rectangular meshes with the dimensions of the distances AL and AQ between the longitudinal filaments 15 and the transverse filaments 16. The small mesh size in the circumferential direction U or transport direction T results in a low fiber loss. The large mesh size transverse to the fiber direction enables a large volume flow of the suction air and a good compaction effect of the fiber structure 6. The free area between the longitudinal filaments 15 and the transverse filaments 16, the screen area 18, is in particular between 20% and 60%, preferably between 30% and 50% of the total screen apron area.

The longitudinal filaments 15 have a diameter DL which is significantly smaller than a diameter DQ of the transverse filaments 16. The transverse filaments 16 preferably have a diameter DQ which is between 10% and 80% larger than the diameter DL of the longitudinal filaments 15. For example, the transverse filaments 16 can have a diameter DQ of approximately 150 µm and the longitudinal filaments 15 can have a diameter DL of approximately 100 µm. This difference in diameter means that the sieve belt 10 rests on the suction pipe 8 essentially on the surfaces of the transverse filaments 16. The wear will therefore affect the transverse filaments 16 first. Only when these have been worn down to a height that is the same as the longitudinal filaments 15 will the longitudinal filaments 15 also be included in the wear.

Figure 4a shows a section through a fabric of a screen belt 10 in the transport direction T of the fiber structure 6 or in the circumferential direction U of the Sieve belt 10. The fibers 17 of the fiber structure 6 would accordingly lie along the plane of the drawing on the sieve belt 10. It can also be seen from this illustration that the diameter DL of the longitudinal filaments 15 is smaller than the diameter DQ of the transverse filaments 16. Accordingly, imaginary surfaces F, which rest on turning points WQ of the transverse filaments 16, are spaced from turning points WL of the longitudinal filaments 15. Accordingly, the underside of the sieve belt 10 essentially lies on the suction pipe 8 with the turning points WQ of the transverse filaments 16. On the top side of the sieve belt 10, the pressure roller 7 also essentially accesses the turning points WQ of the transverse filaments 16. The wear will therefore mainly occur on the transverse filaments 16, since the thinner longitudinal filaments 15, which also meander less, are spaced a distance a from these surfaces F and thus generally have no contact with the suction pipe 8 and the pressure roller 7. The distance AWL of the turning points WL from each other is therefore smaller than the distance AWQ of the turning points WQ from each other. The turning points WL are located between the two surfaces F.

In Figure 4b is a section through a fabric of a screen belt 10 transverse to the transport direction T of the fiber structure 6 or transverse to the circumferential direction U of the screen belt 10. The fibers 17 of the fiber structure 6 would thus lie perpendicular to the plane of the drawing on the screen belt 10. Here too, as in Figure 4a , it can be seen that the imaginary surface F resting on the turning points WQ is spaced a distance a from the turning points WL of the longitudinal filaments 15. This creates points of attack for the sliding of the screen belt 10 over the suction pipe 8 and for the drive by the pressure roller 7 essentially on the thicker transverse filaments 16. The thinner longitudinal filaments 15 are located on each side of the screen belt 10 at a distance a from the respective surface F. The thinner longitudinal filaments 15 are thus separated by the thicker Transverse filaments 16 are protected because they are not exposed to the transverse filaments 16 in the fabric of the sieve belt 10.

From the presentation of the Figures 4a and 4b It is also clear that the longitudinal filaments meander less than the transverse filaments. Depending on the design, meandering can even be largely eliminated altogether. The longitudinal filaments then run completely or at least almost straight.

The present invention is not limited to the embodiments shown and described. In particular, thickness and spacing ratios of the longitudinal filaments 15 and transverse filaments 16 other than those shown are possible. The incorporation of the longitudinal filaments 15 can also be more or less than shown in the embodiments. Despite the different diameters of the longitudinal filaments 15 and transverse filaments 16, it is also possible within the scope of the invention for the spacing a to be reduced to the value "0". This can be achieved by incorporating the longitudinal filaments 15 more deeply.

Modifications within the scope of the patent claims are just as possible as a combination of the features, even if they are shown and described in different embodiments.

List of reference symbols

1

Drafting system

2

Compaction device

3

Feed roller pair

4

Draft roller pair

5

Output roller pair

6

Fibre bandage

7

Pressure roller

8th

Intake manifold

9

Suction slot

10

Screen straps

11

Deflection rod

12

thread

13

Thread guide

14

Low-stress

15

Longitudinal filaments

16

Cross filaments

17

Fibers

18

Screen area

a

Distance

AQ

Distance between transverse filaments

AL

Distance longitudinal filaments

AWL

Distance

AWQ

Distance

DQ

Diameter of transverse filaments

DL

Diameter of longitudinal filaments

D

pivot point

F

Area

K1

Clamping point

K2

Clamping point

K3

Clamping point

K4

Thread clamping point

L

Running direction

P

Arrow direction

WQ

Turning point transverse filaments

WL

Turning point longitudinal filaments

Claims (10)

1. A sieve apron for transporting a fiber strand (6) to be condensed across a suction slit (9) of a condensing device (2) of a spinning machine, having an endless circumference, comprising a plurality of longitudinal filaments (15) disposed adjacent to each other in the circumferential direction (U), and a plurality of transverse filaments (16) disposed adjacent to each other perpendicular to the circumferential direction (U), and spacings (AL, AQ) being present between adjacent longitudinal filaments (15) and adjacent transverse filaments (16), forming open areas so that the sieve apron (10) is air-permeable, characterized in that the adjacent longitudinal filaments (15) have a thinner cross section than the adjacent transverse filaments (16).
2. The sieve apron according to the preceding claim, characterized in that the longitudinal filaments (15) are disposed within surfaces (F) formed by inversion points (WQ) of the transverse filaments (16).
3. The sieve apron according to any one or more of the preceding claims, characterized in that the longitudinal filaments (15) meander less than the transverse filaments (16), whereby a spacing (AWL) of the inversion points (WL) of the longitudinal filaments (15) is less than a spacing (AWQ) of the inversion points (WQ) of the transverse filaments (16).
4. The sieve apron according to any one or more of the preceding claims, characterized in that the longitudinal filaments (15) run substantially in a straight line.
5. The sieve apron according to any one or more of the preceding claims, characterized in that the spacing (AL) of adjacent longitudinal filaments (15) is greater than the spacing (AQ) of adjacent transverse filaments (16).
6. The sieve apron according to any one or more of the preceding claims, characterized in that the open area between the longitudinal filaments (15) and the transverse filaments (16) is between 20% and 60%, preferably between 30% and 50%, of the area of the sieve apron.
7. The sieve apron according to any one or more of the preceding claims, characterized in that the transverse filaments (16) have a diameter (DQ) between 10% and 80% greater than the diameter (DL) of the longitudinal filaments (15).
8. The sieve apron according to any one or more of the preceding claims, characterized in that the sieve apron (10) has a plain weave or a twill weave.
9. The sieve apron according to any one or more of the preceding claims, characterized in that the sieve apron (10) is antistatic.
10. The sieve apron according to any one or more of the preceding claims, characterized in that imaginary surfaces (F) contacting the inversion points (WQ) of the transverse filaments (16) are spaced apart from the inversion points (WL) of the longitudinal filaments (15), whereby the thinner longitudinal filaments (15) are disposed at a spacing (a) from said surfaces (F).

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