EP3464691B1 - Yarn forming element for a pre-spinning machine and pre-spinning machine equipped therewith - Google Patents

Description

The present invention relates to a yarn-forming element for a roving machine, with which roving can be produced from a fiber structure with the aid of compressed air, the yarn-forming element comprising an inlet opening for the fibers of the fiber structure, and the yarn-forming element having an outlet for the outlet of the roving machine during operation the fiber structure in the region of the inlet opening of the yarn formation element and has a discharge channel connecting the inlet opening and the outlet.

In addition, a roving machine for producing a roving from a fiber structure with at least one spinning station is proposed, the spinning station having a whirlpool chamber with an inlet opening for the fiber structure and a yarn-forming element extending at least partially into the whirlpool chamber, and the spinning station having air nozzles directed into the whirlpool chamber via which air can be introduced into the vortex chamber in a predetermined direction of rotation in order to impart a rotation in said direction of rotation to the fiber structure fed via the inlet opening in the region of an inlet opening of the yarn-forming element.

Roving machines with corresponding spinning positions are known in the prior art and are used to produce a roving from an elongated fiber structure. The outer fibers of the fiber structure are wound around the inner core fibers with the help of a turbulent air flow generated by the air nozzles inside the turbulence chamber in the area of the inlet opening of the yarn-forming element and thus form the core fibers that are decisive for the desired strength of the yarn. This creates a roving with a real twist, which is finally discharged via a discharge channel from the vortex chamber and z. B. can be wound onto a sleeve.

From the EP2767624A1 a spinning position of an air jet spinning machine for spinning a fiber structure to produce a yarn is known. The spinning position points a pair of delivery rollers and a spinneret, the spinneret having a yarn-forming element and a fiber-guiding element. The fiber guide element has a beginning facing the pair of delivery rollers and an end facing away from the pair of delivery rollers. The fiber structure is fed to the spinneret with the pair of delivery rollers and introduced into the spinneret through the fiber guide element, and then a yarn is formed from the fiber structure by the yarn-forming element.

From the DE102012108613A1 a spinning position of a roving machine for producing a roving from a fiber structure is known. The spinning station has a turbulence chamber with an inlet opening for the fiber structure and a yarn-forming element that extends at least partially into the turbulence chamber.

In general, within the meaning of the invention, the term roving (other designation:
Lunte) to understand a fiber structure, in which at least a part of the fibers around a inner core are wound. This type of yarn is characterized by the fact that, despite having a certain strength that is sufficient to transport the yarn to a subsequent textile machine, it is still capable of being drawn. The roving can thus using a default device, z. B. the drafting system, a textile machine processing the roving, for example a ring spinning machine, before it is finally spun into a conventional yarn.

In the area of the inlet of the spinneret of the spinning station in which the roving is produced, a fiber guide element is usually arranged, via which the fiber strand is guided into the spinneret and finally into the area of the yarn-forming element, with the yarn-forming elements generally being elongated structures with a internal discharge duct find use.

In the area of the end face of the yarn-forming element surrounding the inlet opening, compressed air is introduced into the turbulence chamber via the air nozzles, so that ultimately the named rotating turbulence air flow results from the appropriate alignment of the air nozzles. As a result, individual outer fibers are separated from the fiber structure leaving the fiber guide element or are pulled out of the fiber structure a little and folded over the end face of the yarn-forming element. As they progress, these fibers rotate on the surface of the yarn-forming element. As a result, the rotating fibers are wound around the core fibers by the forward movement of the inner core fibers of the fiber structure, thereby forming the roving.

In addition to the geometry of the vortex chamber and the strength and alignment of the individual air flows formed by the air nozzles, the geometry of the yarn-forming element also plays a decisive role in the quality of the roving.

The object of the present invention is therefore to propose a yarn-forming element and a roving machine equipped with it, which enables the production of a roving of particularly high quality.

The object is achieved by a yarn forming element and a roving machine with the features of the independent patent claim.

According to the invention, the yarn-forming element is characterized in that it comprises an end face surrounding the inlet orifice, which at least partially has the shape of a truncated cone, with the top surface of the truncated cone being arranged between the base of the truncated cone and the outlet of the yarn-forming element. As usual, within the scope of the present invention, the top surface of the truncated cone is understood to be the flat and circular surface of the truncated cone with the smaller radius and the base surface is understood to be the flat and circular surface of the truncated cone with the larger radius. A corresponding truncated cone is shown in Figure 3a .

The yarn-forming element thus has an end face that is at least partially conical or funnel-shaped, with the funnel or cone or the above-mentioned truncated cone tapering in the direction of the outlet of the yarn-forming element. Such a shape is produced, for example, by countersinking.

The stated shape of the area surrounding the inlet opening results in an end face which, in a top view, surrounds the discharge channel in a ring shape and which, due to the funnel effect, ensures that the roving enters the discharge channel gently. It has been shown that the formation of the above-mentioned twisted fibers is improved as a result and the quality of the roving, in particular its uniformity, increases.

In order to prevent slubs in the roving (which can be caused, for example, by contamination of the fiber structure or by bundling of the roving) being pulled too far into the discharge channel, it is proposed according to the invention that the angle between a generatrix of the truncated cone and its cone axis has a magnitude that is less than 90° and greater than 70°. The cone axis is the axis of rotation of the truncated cone. The generating line is a line that lies on the lateral surface of the truncated cone and is in a plane with the axis of the cone runs. Also in this context Figure 3a referenced, showing a corresponding truncated cone.

In other words, the end face should therefore have the shape of a relatively flat truncated cone, the height of which should be only between 2% and 20% of the diameter of the base area. If a slub of the roving reaches the area of the end face, which is thicker than the inner diameter of the discharge channel, the slub area in the area of the end face of the yarn forming element or the frustoconical section gets caught and can thus be easily removed.

In addition, the frustoconical area of the end face should merge directly into the discharge channel, so that the diameter or the cross-sectional shape of the discharge channel in this area corresponds to the diameter or the shape of the top surface of the truncated cone.

In addition, there are advantages if the discharge channel has a longitudinal axis and the longitudinal axis and said cone axis run parallel or collinear to one another. The discharge duct is preferably rotationally symmetrical, in which case the longitudinal axis would correspond to the axis of rotation of the discharge duct. The stated mutual arrangement of the longitudinal axis and cone axis ensures that a plane resting on the end face of the yarn-forming element runs perpendicular to the longitudinal axis of the discharge channel, along which the roving moves in the direction of the outlet of the yarn-forming element.

There are particular advantages if the discharge channel has an inner diameter in a region adjoining the inlet opening or the truncated cone, the amount of which is 4 mm to 12 mm, preferably 6 mm to 8 mm. If the specified diameter limits are observed, a particularly advantageous air flow occurs in the area of the inlet opening of the yarn-forming element, which causes only part of the outer fiber ends to be caught and wrapped around the actual fiber core with the desired strength. On the other hand, if the diameter is less than 4 mm, one gradually arrives in the range of the conventional Air spinning is known and results in a relatively strong yarn that is only partially suitable as a roving. If, on the other hand, a diameter of more than 12 mm is selected, the air pressure of the air supplied via the air nozzles must be significantly increased in order to ensure the necessary turbulent flow within the turbulence chamber, since part of the incoming air leaves the turbulence chamber via the inlet opening of the yarn-forming element without going to the contribute to vortex formation.

However, a particularly advantageous roving can only be produced if the diameter deviates significantly from the values known from conventional air-jet spinning, which are between 0.5 and a maximum of 2.0 mm the centrally arranged core fibers are looped (thus providing the roving with a protective twist), with the proportion and strength of the wrapping fibers being only so high that the desired drafting of the roving is still possible in the course of the subsequent spinning process on a subsequent spinning machine.

It is also advantageous if the yarn-forming element has a cylindrical wall with a cylindrical outer surface and a cylindrical inner surface delimiting the discharge channel in the area of the inlet opening, the inner surface and the outer surface running concentrically. The yarn-forming element therefore has at least one cylindrical section with a constant wall thickness in the area adjoining the end face.

It is also advantageous if the entire end face of the yarn-forming element, which connects the outer surface and the inner surface, has the shape of a truncated cone. The section of the yarn-forming element that has the inlet opening thus preferably has three surface sections, namely a surface section formed by the outer surface of the yarn-forming element, a surface section formed by the inner surface adjoining the inlet opening (and at least partially delimiting the discharge channel), and a surface section formed by the end face. which has the shape of a truncated cone.

It can also bring advantages if the transition area between the end face and the discharge channel and/or the transition between the end face and an outer surface of the yarn-forming element is not sharp-edged, but rounded. The radius of the rounded portions, which should have a ring shape in a plan view of the end face of the yarn-forming element, should be between 0.1 mm and 2.0 mm. As a result, the fibers of the fiber structure are exposed to lower mechanical loads than in the case of correspondingly sharp-edged transitions.

It is also advantageous if the yarn-forming element has a chamfer in the area of the end face, which also has the shape of a truncated cone. The bevel should preferably merge into the outer surface of the yarn-forming element and be spaced apart from the discharge channel by a frustoconical area on the end face of the yarn-forming element. In particular, it is advantageous if the base of the truncated cone forming the bevel is arranged between the top surface of this truncated cone and the outlet of the yarn-forming element. The chamfer should thus form a truncated cone which is inverted with respect to the truncated cone described in claim 1. In particular, it is advantageous if the base of the truncated cone adjoining the discharge channel corresponds to the top surface of the truncated cone formed by the chamfer. The two truncated cones therefore advantageously merge directly into one another.

It is advantageous if the bevel encloses an angle β with a longitudinal axis of the discharge channel, the amount of which is between 20° and 70°, preferably between 30° and 60°. Furthermore, in a longitudinal section of the yarn-forming element, the bevel should enclose an angle of between 70° and 90° with the further frustoconical region mentioned in claim 1. If the chamfer is arranged between the discharge channel and the further area of the end face of the yarn-forming element, which forms a truncated cone, the stated angle should be greater than 140° and smaller than 180°.

There are particular advantages if the end face has at least one second frustoconical region in addition to a first frustoconical region, the second frusto-conical region surrounding the first frusto-conical region in a plan view of the end face of the yarn-forming element. For example, such an embodiment can be realized in that the cylindrical end of the yarn-forming element, which also includes the inlet opening, is first machined with a countersink in such a way that the area mentioned in claim 1, which has the shape of a truncated cone, is created and then the transition area is provided with an annular chamfer between the face of the yarn-forming element and the outer surface of the yarn-forming element.

It is particularly advantageous if the second frustoconical area directly adjoins the first frustoconical area, with both frustoconical areas preferably running concentrically to one another. It is conceivable in this context that the base of the first frustoconical area forms the top surface of the second frustoconical area. Furthermore, it is advantageous if the diameter of the top surface of the first frustoconical area is smaller than the top surface of the second frustoconical area.

It is also advantageous if the smallest angle between a generatrix of the first frustoconical area and a longitudinal axis of the discharge channel has a different, preferably smaller, amount (e.g. 50° to 80°) than the smallest angle between a generatrix of the second frustoconical region and said longitudinal axis of the flue (which should be greater than 70° and less than 90°).

In any case, the yarn-forming element according to the invention is characterized in that at least a part, e.g. B. an annular region of an end face of the yarn-forming element, preferably the entire end face thereof, is inclined inwardly in the direction of the discharge channel in a longitudinal section of the yarn-forming element.

Finally, the present invention relates to a roving machine for producing a roving from a fiber structure with at least one spinning station, the spinning station having a turbulence chamber with an inlet opening for the fiber structure and a yarn forming element extending at least partially into the vortex chamber. The spinning station also includes air nozzles directed into the whirl chamber, via which air can be introduced into the whirl chamber in a predetermined direction of rotation, in order to impart a rotation in said direction of rotation to the fiber structure fed via the inlet opening in the region of an inlet opening of the yarn-forming element. As a result, a roving with the properties already described can be produced from the fiber structure. In order to finally be able to wind the roving onto a sleeve, the yarn-forming element has an outlet for the outlet of the roving and a discharge channel connecting the inlet opening and the outlet, through which the roving passes before exiting via the outlet.

According to the invention, it is now provided that the yarn-forming element is designed according to the previous or following description, with the individual features being able to be implemented in any combination, provided that this does not result in any contradictions.

Figur 1

eine Vorspinnmaschine in der Seitenansicht,

Figur 2

einen Ausschnitt einer bekannten Spinndüse einer Vorspinnmaschine,

Figur 3a

einen Kegelstumpf,

Figur 3b

einen Ausschnitt eines erfindungsgemäßen Garnbildungselements im Längsschnitt,

Figuren 4a bis 7b

einen Ausschnitt weiterer Ausführungsformen erfindungsgemäßer Garnbildungselemente im Längsschnitt, und

Figur 8

einen Ausschnitt einer weiteren Spinndüse einer Vorspinnmaschine.

Further advantages of the invention are described in the following exemplary embodiments. They show, each schematically:

figure 1

a roving machine in side view,

figure 2

a section of a known spinneret of a roving machine,

Figure 3a

a truncated cone,

Figure 3b

a section of a yarn formation element according to the invention in longitudinal section,

Figures 4a to 7b

a detail of further embodiments of yarn formation elements according to the invention in longitudinal section, and

figure 8

a section of another spinneret of a roving frame.

figure 1 shows a schematic view of a section of a roving machine. If required, the roving machine can have a drafting system with several, each around a rotary axis 23 rotatable drafting system rollers 21 (only two of the six drafting system rollers 21 are provided with a reference number), the drafting system being supplied with a fiber structure 1, for example in the form of a doubled draw frame sliver, during the spinning operation.

Furthermore, the roving frame shown comprises one or more spinning nozzles 22 arranged adjacent to one another, each with an internal turbulence chamber 15 (see FIG figure 2 ), in which the fiber structure 1 or at least some of the fibers of the fiber structure 1 is provided with a twist (the precise mode of operation of the spinneret 22 is described in more detail below).

In addition, the roving machine can comprise a take-off device 24 with a plurality of interacting take-off rollers 31 and a winding device 25 downstream of the take-off rollers 31, with the aid of which the spinneret 22 can be fed via an outlet 4 (which at the same time is the outlet 4 of the, for example, in figure 2 closer shown discharge channel 5 forms) leaving roving 2 can be wound onto a sleeve 32 to form a coil, in which case a traversing element 20 can be used. The roving machine according to the invention does not necessarily have to have a drafting system, as is shown in figure 1 is shown. The take-off rollers 31 are also not absolutely necessary.

In any case, the roving machine according to the invention works according to an air spinning process. To form the roving 2, the fiber strand 1 is guided into the turbulence chamber 15 of the spinneret 22 via an inlet opening 16, in which a so-called fiber guide element is preferably arranged (see also figure 2 ). There it is rotated, ie at least a part of the free fiber ends of the fiber structure 1 is caught by an air flow which is generated by air nozzles 18 correspondingly arranged in a turbulence chamber wall 26 surrounding the turbulence chamber 15 . Some of the fibers are pulled out of the fiber structure 1 at least a little and wound around the tip of a yarn-forming element 17 protruding into the eddy chamber 15 . Due to the fact that the fiber structure 1 is pushed through an end face 6 of the yarn-forming element 17 in the area of the end face 6 pointing in the direction of the inlet opening 16 arranged inlet opening 3 of the yarn-forming element 17 is drawn off from the turbulence chamber 15 via a discharge channel 5 arranged within the yarn-forming element 17, the free fiber ends are finally also pulled in the direction of the inlet opening 3 and thereby wrap around the centrally running core fibers as so-called winding fibers - resulting in a roving 2 having the desired twist. The draw-off channel 5 should also have an inside diameter D, the amount of which is in the above-mentioned range.

In general, it should be made clear at this point that the roving 2 produced is a yarn with a relatively small proportion of twisted fibers, or a yarn in which the twisted fibers are wrapped relatively loosely around the inner core, so that the Roving 2 remains draftable. This is crucial because the roving 2 produced has to be drafted again on a subsequent textile machine (e.g. a ring spinning machine) using a drafting system in order to be able to be further processed into a conventional yarn that can be processed into a fabric, for example on a weaving machine.

With regard to the air nozzles 18, it should also be mentioned at this point, purely as a precaution, that they should generally be aligned in such a way that they jointly generate a rectified air flow with a uniform direction of rotation. The individual air nozzles 18 are preferably arranged rotationally symmetrically to one another. It should also be pointed out that the inclination of the air nozzles 18 in relation to the longitudinal axis L of the discharge channel 5 can be selected within certain limits. For example, the air nozzles 18 could run perpendicular to the longitudinal axis L mentioned (see in figure 2 air nozzle 18 shown on the left). Of course, a certain inclination is also conceivable, so that the angle between a central axis (not shown) of the air nozzle 18 and the longitudinal axis L deviates from 90° (see in figure 2 air nozzle shown on the right 18). In general, the inclination of all air nozzles 18 should be the same. The representation in figure 2 was therefore only chosen to show in principle that generally different inclinations of the air nozzles 18 are conceivable.

While figure 2 an already known Garnbildungselement 17 with a perpendicular to Longitudinal axis L of the discharge channel 5 extending end face 6 shows are the Figures 3b to 7b Exemplary embodiments of yarn-forming elements 17 according to the invention can be seen, whereby for reasons of clarity only the area of the end face 6 surrounding the inlet opening 3 and a piece of the adjoining wall 30 of the yarn-forming element 17 are shown.

Like now, for example Figure 3b shows, the yarn-forming element 17 according to the invention is characterized in that said end face, which is part of the wall 30 of the yarn-forming element 17, is inclined slightly inward. In other words: The yarn-forming element 17 comprises an end face 6 surrounding the inlet opening 3, which has the shape of a truncated cone 27 at least in sections, with the top surface 7 of the truncated cone 27 being arranged between the base 8 of the truncated cone 27 and the outlet 4 of the yarn-forming element 17.

With regard to the terminology used in connection with the truncated cone 27 is on Figure 3a referred, from which it can be seen that the top surface 7 is the circular surface with the smaller radius and the base surface 8 is the circular surface with the larger radius. Finally, the lateral surface 29 is the surface that connects the base surface 8 to the top surface 7 . The generatrices 28 are the lines that lie on the lateral surface 29 and run in a plane with the cone axis K, which in turn represents the axis of rotation of the truncated cone 27 .

As the individual embodiments according to the Figures 3b to 7b as can be seen, the yarn-forming element 17 according to the invention has an end face 6 which, at least in sections, has the above-mentioned truncated cone shape, with the Figure 3b Angle α shown between the longitudinal axis L of the discharge channel 5 and any surface line 28 of the truncated cone 27 has an amount that is greater than 70 ° and less than 90 °. Said area thus forms a relatively flat cone, which also has only a slight funnel effect.

The frustoconical area preferably forms the entire end face 6 of the Yarn-forming element 17, which surrounds the inlet opening 3 and which connects the inner surface 19 of the yarn-forming element 17, which delimits the discharge channel 5, and an outer surface 10 of the same, which preferably runs concentrically with said inner surface 19 (at least in a first area adjoining the end face 6). A corresponding version is in Figure 3b shown.

It is also conceivable that the transition 11 between the end face 6 of the yarn-forming element 17 and the aforementioned outer surface 10 of the same is rounded ( Figures 4a and 4b ). Alternatively or additionally, the transition area 9 between the end face 6 of the yarn-forming element 17 and the discharge channel 5 can also be rounded ( Figure 4b ).

The Figures 5a and 5b show solutions in which the end face 6 of the yarn-forming element 17 comprises, in addition to the area mentioned having the shape of a truncated cone 27 , a further area which also has the shape of a truncated cone 27 . The end face 6 therefore preferably comprises a first frustoconical area 13 and a second frustoconical area 14.

Preferably, the angle ε between a surface line 28 of the first frustoconical area 13 and the longitudinal axis L of the discharge channel 5 is greater than the angle δ between a surface line 28 of the second frustoconical area 14 and the longitudinal axis L of the discharge channel 5 ( Figure 5b ). In some cases, however, the opposite design can also be advantageous, as shown in Figure 5a is shown.

The Figures 6a and 6b show that the end face 6 of the yarn-forming element 17 can also be partially formed by a chamfer 12, the angle β between a surface line 28 of the truncated cone 27, which is described by the chamfer 12, and the longitudinal axis L of the discharge channel 5 preferably in the already in the range mentioned in the general description. In principle, the chamfer 12 forms the second frustoconical region 14 described above.

Furthermore, the Figures 7a and 7b can be seen that the shape of the outer surface 10 of the yarn-forming element 17 and/or the shape of the inner surface 19 of the yarn-forming element 17 may deviate from the shape of a cylinder and/or have gradations.

Finally shows figure 8 A detail of a cross section through another spinneret 22. In addition to air nozzles 18, which serve to form the already described turbulent air flow during normal operation and thus after a piecing process, the spinneret 22 also includes one or more piecing air nozzles 33, via which (likewise) Compressed air can be introduced into the vortex chamber 15.

In other words, it is advantageous if the spinning nozzle 22 has special piecing air nozzles 33 which are fed with compressed air exclusively or together with the air nozzles 18 during a piecing process. The piecing process is the initial sequence of roving production, in which the fiber structure 1 is introduced into the previously empty eddy chamber 15 and twisted there to form a roving 2 . The roving section thus formed is taken over by a corresponding take-off device 24 after leaving the take-off channel 5 and is brought into contact with a rotating sleeve 32 while the supply and twisting of the fiber structure 1 continues. This is followed by normal operation of the spinneret 22 , in which further roving 2 is continuously produced from the supplied fiber structure 1 and drawn off from the spinneret 22 .

While it can be advantageous to apply compressed air only to the air nozzles 18 during normal operation and only to the piecing air nozzles 33 during the piecing process (both should enclose different angles with the longitudinal axis L of the draw-off channel 5), it can also be advantageous if the piecing air nozzles 33 are also subjected to compressed air during normal operation. In particular, the piecing air nozzles 33 should be inclined relative to the longitudinal axis L of the offtake duct 5 in order to be able to generate an air flow that extends at least a little way into the offtake duct 5 (the angle between the longitudinal axis L and a central axis of the piecing air nozzles 33 or their direction vectors should therefore deviate from 90°). This ultimately prevents air from flowing through the discharge channel 5 in the direction of its inlet opening 3 counter to the direction of movement of the roving 2 .

The present invention is not limited to the illustrated and described embodiments. Modifications within the scope of the patent claims are possible.

Reference List

1

fiber bandage

2

roving

3

Yarn forming element inlet mouth

4

Yarn forming element outlet

5

culvert

6

Front side of the yarn formation element

7

Top surface of the truncated cone

8th

base of the truncated cone

9

Transition area between the end face of the yarn formation element and the discharge channel

10

Outer surface of the yarn forming element

11

Transition between the face of the yarn-forming element and the outer surface of the same

12

chamfer

13

first frustoconical area

14

second frustoconical area

15

vortex chamber

16

inlet opening

17

yarn forming element

18

air nozzle

19

inner surface of the yarn-forming element delimiting the drainage channel

20

oscillating element

21

drafting roller

22

spinneret

23

Axis of rotation of the drafting system roller

24

trigger device

25

spooling device

26

vortex chamber wall

27

truncated cone

28

surface line of the truncated cone

29

lateral surface of the truncated cone

30

Wall of the yarn forming element

31

pull-off roller

32

sleeve

33

piecing air nozzle

a

Angle between a surface line of the truncated cone and its cone axis

β

Angle between the chamfer and a longitudinal axis of the flue

δ

Angle between a generatrix of the second frustoconical portion and the longitudinal axis of the flue

ε

Angle between a generatrix of the first frustoconical portion and a longitudinal axis of the flue

D

Inside diameter of the flue

L

Longitudinal axis of the culvert

K

cone axis

Claims (10)

1. A yarn-forming element (17) for a roving machine, with which a roving (2) can be produced from a fiber structure (1) with the help of compressed air,

   - wherein the yarn-forming element (17) comprises an intake opening (3) for fibers of the fiber structure (1), and

   - wherein the yarn-forming element (17) has an outlet (4) for the emergence of the roving (2) produced from the fiber structure (1) in the area of the intake opening (3) of the yarn-forming element (17) during operation of the roving machine and having a draw-off channel (5), which connects the intake opening (3) and the outlet (4),

   characterized in that
   the yarn-forming element (17) comprises a front end (6), which surrounds the intake opening (3) and has a truncated cone shape (27) in at least some sections,

   - wherein the cover surface (7) of the truncated cone (27) is arranged between the base surface (8) of the truncated cone (27) and the outlet (4) of the yarn-forming element (17), and

   - wherein the angle (α) between a lateral line (28) of the truncated cone (27) and its cone axis (K) has a value less than 90° and greater than 70°.
2. The yarn-forming element (17) according to the preceding claims, characterized in that the draw-off channel (5) has a longitudinal axis (L), and the longitudinal axis (L) and the aforementioned cone axis (K) run parallel or colinear to one another.
3. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the draw-off channel (5) has an inside diameter (D) in an area adjacent to the intake opening (3), the amount being 4 mm to 12 mm, preferably 6 mm to 8 mm.
4. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the yarn-forming element (17) has a cylindrical wall (30) with a cylindrical outside surface (10) and a cylindrical inside surface (19) bordering the draw-off channel (5) in the area of the intake opening (3), wherein the inside surface (19) and the outside surface (10) run concentrically, and wherein the entire front end (6) of the yarn-forming element (17) connecting the outside surface (10) and the inside surface (19) has a truncated cone shape (27).
5. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the transition region (9) between the front end (6) and the draw-off channel (5) and/or the transition (11) between the front end (6) and an outside surface (10) of the yarn-forming element (17) is/are rounded.
6. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the yarn-forming element (17) has in the area of the front end (6) a chamfer (12), which is also in a truncated cone shape (27), wherein the base surface (8) of the truncated cone (27) forming the chamber (12) is arranged between the cover surface (7) of this truncated cone (27) and the outlet (4) of the yarn-forming element (17).
7. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the chamfer (12) forms an angle (β) with the longitudinal axis (L) of the draw-off channel (5), this angle amounting to between 20° and 70°, preferably between 30° and 60°.
8. The yarn-forming element (17) according to any one of the preceding claims, characterized in that the front end (6) has at least one second truncated cone region (14) in addition to a first truncated cone region (13), wherein the second truncated cone region (14) surrounds the first truncated cone region (13) in a top view of the front end (6) of the yarn-forming element (17).
9. The yarn-forming element (17) according to the preceding claim, characterized in that the second truncated cone region (14) is connected directly to the first truncated cone region (13) wherein both truncated cone regions preferably run concentrically to one another.
10. A roving machine for producing a roving (2) from a fiber structure (1) having at least one spinneret,

    - wherein the spinneret has an eddy chamber (15) with an intake opening (16) for the fiber structure (1) and a yarn-forming element (17) extending at least partially into the eddy chamber (15), and

    - wherein the spinneret comprises air jets (18) directed into the eddy chamber (15), by means of which air can be introduced into the eddy chamber (15) in a predetermined direction of rotation in order to impart a twist in the aforementioned direction of rotation to the fiber structure (1) fed through the intake opening (16) in the region of an intake opening (3) of the yarn-forming element (17),

    characterized in that
    the yarn-forming element (17) is designed according to any one of the preceding claims.

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