EP3153612A1 - Method for preparing a yarn end for spinning on to a rotor spinning device of a rotor spinning machine and rotor spinning machine - Google Patents

Abstract

In a method for preparing a yarn end (9) for piecing on a rotor spinning device (2) of a rotor spinning machine (1) with a with a lid (4) closable and via a vacuum channel (8) acted upon by a negative pressure rotor housing (3), with a in the rotor housing (3) rotatably mounted and spinning during the spinning operation at an operating speed spinning rotor (5) and with a discharge nozzle (7), the yarn to be prepared (9) is inserted into the vacuum channel (8) and by a separation structure (10) of open edge of the spinning spinning rotor (5) interrupted and thereby prepared for piecing. The spinning rotor (5) is driven during the interruption of the yarn end (9) with a defined Garnendenvorbereitungsdrehzahl, wherein the Garnendenvorbereitungsdrehzahl either equal to the operating speed of the spinning rotor (5) or less than the operating speed of the spinning rotor (5). A corresponding rotor spinning machine (1) has a control unit (17), by means of which the rotor spinning device (2) according to one of the preceding claims is operable.

Description

The present invention relates to a method for preparing a yarn end for piecing on a rotor spinning device of a rotor spinning machine, wherein the rotor spinning machine with a lid closable and acted upon by a vacuum duct with a negative pressure rotor housing, a rotatably mounted in the rotor housing and rotating during the spinning operation at an operating speed Spinning rotor and a discharge nozzle has. In the methods, the yarn end to be prepared is introduced into the vacuum channel of the rotor spinning device and interrupted by a separating structure of the open edge of the spinning spinning rotor and thereby prepared for piecing. Furthermore, the invention relates to a corresponding rotor spinning machine with at least one such rotor spinning device.

In order to be able to start the spinning process when spinning on a rotor spinning machine or to be able to resume the spinning process after interrupting the spinning process, for example due to a yarn breakage, a quality cut or after the rotor spinning machine has stopped, a yarn end must always be prepared for the piecing process. For this purpose, it is necessary to aufzufasern the yarn end to align the individual fibers of the yarn end for the piecing and free of short fibers. The yarn end prepared for piecing must then be returned to the spinning rotor with a length as precisely as possible, in order to be able to reconnect with the fiber material deposited there.

To prepare yarn ends for piecing, for example, it has become known in the prior art to prepare the yarn end pneumatically. The yarn end is exposed to an air flow which acts in the tangential, axial and / or radial direction of the yarn end.

From the DE 196 53 389 A1 it has also become known to prepare the yarn end by means of a needles or saw teeth occupied, rotating roller. By means of such a roller, it is possible to open in the rotor yarn typically existing abdominal ligaments, which can hinder the pneumatic Garnendenpräparation. Following the opening of the abdominal ligaments, in turn, a pneumatic Garnendenpräparation is performed.

From the DE 10 2012 110 926 A1 It has also been known to prepare the yarn end by means of the edge region of the spinning spinning rotor. The yarn is brought to this at least partially open rotor housing in the vicinity of the open edge of the spinning rotor. The spinning rotor is now set in rotation and the lid of the rotor housing closed, so that the yarn end is now pressed against the open edge of the rotor and cut. The edge of the spinning rotor is provided for this purpose with a roughening or abrasive. According to another embodiment, the yarn is introduced into the closed rotor housing, wherein a single driven rotor is displaced in its axial direction. After insertion of the yarn end, the rotor is in turn shifted back into its operating position and set in rotation so that the run-up of the rotor results in an interruption of the yarn end. By means of this type of yarn preparation, troublesome abdominal bandages can be opened and the yarn end preparation can be carried out directly at the spinning position. However, there may be differences in the quality of Garnendenaufbereitung in terms of length and fuzziness of the yarn end.

The object of the present invention is therefore to propose a method for yarn end preparation and a corresponding rotor spinning machine, by means of which even in various applications a good and uniform yarn end preparation can be achieved.

The object is solved with the features of the independent claims.

In a method for preparing a yarn end for piecing on a rotor spinning device, wherein the rotor spinning device has a closable with a lid and acted upon by a vacuum duct with a negative pressure rotor housing, a rotatably mounted in the rotor housing and rotating during the spinning operation at an operating speed spinning rotor and a take-off nozzle , the yarn end to be prepared is introduced into the vacuum passage of the rotor spinning device and is interrupted by a separation structure of the open edge of the spinning spinning rotor and thereby prepared for piecing. The spinning rotor is driven during the interruption of the yarn end with a defined Garnendenvorbereitungsdrehzahl. The yarn end preparation speed is either equal to the operating speed of the spinning rotor or less than the operating speed of the spinning rotor.

By driving the spinning rotor during the interruption of the yarn end with a defined speed is achieved that the yarn ends are always interrupted under the same conditions with a defined separation speed, so that even with different applications, the yarn ends are prepared and frayed with a largely constant length of yarn. By driving the spinning rotor with a comparison with the operating speed reduced Garnendenvorbereitungsdrehzahl it also leads to a very gentle separation of the yarn end, which is thereby fanned very evenly. Due to the uniform, reproducibly good resolution of the yarn ends, the success rate of piecing process can be increased, so that overall, the machine efficiency increases. At the same time, the yarn end, which has been processed optimally, also produces a good and reproducible yarn end Quality of the piecing received, so that the yarn quality can be improved overall.

A rotor spinning machine with at least one rotor spinning device with a closable with a lid and acted upon by a vacuum channel with a negative pressure rotor housing, with a rotatably mounted in the rotor housing spinning rotor and a discharge nozzle, wherein an edge of the spinning rotor, a separation structure for interrupting and preparing a in the vacuum channel introduced yarn end for piecing, includes for carrying out the method for yarn end preparation, a corresponding control unit. By means of the control unit, it is possible to drive the spinning rotor during the interruption of the yarn end with a defined Garnendenvorbereitungsdrehzahl, which is less than the operating speed of the spinning rotor.

It is advantageous if the Garnendenvorbereitungsdrehzahl less than 80%, preferably less than 65% and more preferably less than 55% of the operating speed and is preferably less than a piecing speed of the spinning rotor. Too fast a severing of the yarn end, in which sufficient fuzz can be achieved, is thereby avoided. In addition, especially with a Garnendenvorbereitungsdrehzahl of less than 55% of the operating speed and safety aspects are taken into account when the Garnendenvorbereitung is performed at partially open rotor housing.

According to a development of the invention, it is advantageous if the cover of the rotor housing before insertion of the yarn end in the vacuum channel in an intermediate position, in particular a semi-open position is transferred, and the yarn to be prepared yarn is introduced with the spinning rotor and semi-open rotor housing in the vacuum channel. Thereafter, the spinning rotor is rotated and driven at the yarn end preparation speed for the predetermined period of time, the yarn is interrupted. Only after the interruption of the yarn end, the lid is finally transferred to a closed position. The cover of the rotor housing is for this purpose at least in a closed position, an open position and an intermediate position, in particular a semi-open position, brought or between these positions back and forth feasible.

According to an advantageous development of the method, the yarn end prepared for piecing is already returned to the fiber collecting groove of the spinning rotor by closing the lid or moving the lid from the intermediate position to the closed position. However, it is also possible to provide the yarn length to be returned to the spinning rotor in the usual way by a short-term drive of the take-off direction of the rotor spinning device against the regular take-off direction.

For a good and reproducible Garnendenvorbereitung it is also advantageous if the spinning rotor is each driven for a predetermined period of time with the defined Garnendenvorbereitungsdrehzahl for Garnendenvorbereitung. The predetermined period of time is determined in such a way that, on the one hand, a reliable severing of the thread end within this period of time can be assumed and, on the other hand, the piecing process can be continued quickly in order not to adversely affect the machine efficiency. In order to achieve optimal yarn end preparation for all applications on the rotor spinning machine, it is also advantageous if the predetermined period of time is set depending on a type of yarn produced and / or a type of spinning rotor.

According to an advantageous development of the method, in the event of a plannable interruption of the spinning operation, devices involved in yarn production, at least one feed device and one winding device, are braked in a controlled manner until they come to a standstill such that the yarn end retains its position after the controlled braking within the rotor spinning device. especially located within the hood. It can thus be avoided in the case of a plannable interruption of the spinning operation, the emergence of the yarn end on the bobbin with the following elaborate thread search. The controlled shutdown of the rotor spinning device is particularly advantageous in connection with the Garnendenvorbereitung through the open edge of the spinning rotor, since the yarn completely in its regular yarn course and can be sucked directly from its end position within the rotor spinning device or within the discharge nozzle in the vacuum channel, which continues to contribute to an increase in machine efficiency.

An advantageous development of the method provides that the yarn end unwound after controlled braking against its regular take-off direction of a coil is inserted into the vacuum channel of the rotor spinning device and rewound until a faulty piece of yarn is completely sucked into the vacuum channel, and then the yarn end is prepared for piecing. In the case of a quality cut, the defective piece of yarn can thus be sucked, separated and disposed of directly through the vacuum channel. In this case, the yarn end preparation for the re-spinning can be carried out at the same time as the cutting of the defective piece of yarn.

For rewinding the yarn end, the winding device and the extraction device are advantageously driven counter to their regular direction of rotation, the extraction device being driven at a higher speed than the winding device. The amount of speed refers to the peripheral speed of the take-off device or the winding device and thus to the speed at which the yarn is transported. Due to the faster drive of the take-off device, the yarn to be spooled is subjected to a tensioning distortion, whereby sticking of the yarn on the spool and any possible back-loops caused thereby can be avoided. In a rotor spinning machine, it is there advantageous if the winding device is provided for rewinding with a soft start control.

For controlled braking of the devices involved in yarn production, it is also advantageous if the spinning rotor is first brought from its operating speed to a braking speed which is lower than the operating speed and driven for a predetermined period of time with the braking speed. Only then is the spinning rotor braked to a standstill. Thus, even during the controlled deceleration, a regular yarn can still be produced or at least the length of a faulty yarn piece produced during the controlled braking can be reduced. It is particularly advantageous if the Abbremsdrehzahl is equal to or less than the piecing speed of the spinning rotor, as this prevail essentially the same operating conditions as during piecing.

In addition, it is advantageous if, after the transfer of the lid into the intermediate position and before the insertion of the yarn end into the vacuum channel, the spinning rotor is subjected to a cleaning, in particular a pneumatic cleaning. The advantage here is that the cleaning of the spinning rotor can also be done in the intermediate position and thus time can be saved, which in turn benefits the machine use effect. In addition to a pneumatic cleaning, of course, a mechanical cleaning by means of a brush or a scraper is possible.

After a particularly advantageous development of the rotor spinning machine, the vacuum level in the vacuum channel is adjustable. Thus, in the yarn end preparation process, an adjustment of the vacuum level to the type of yarn produced can be made. For example, in yarns which are more difficult to suck in, the vacuum level can be increased.

It is likewise advantageous if the vacuum level in the vacuum channel is increased at least briefly before the yarn end is introduced into the vacuum channel. The insertion of the yarn end into the vacuum channel can be facilitated thereby.

In order to reliably perform the interruption of the yarn end, it is also advantageous if the yarn end is preferably moved oscillating in its longitudinal direction during its interruption by means of a take-off device of the rotor spinning device. In addition to supporting the separation process, the length of the prepared yarn end can also be adjusted by means of the movement of the yarn end.

If, for a plannable interruption of the spinning operation, the rotor spinning device or the devices involved in the yarn production brakes controlled, it is advantageous if the yarn is fixed at standstill of the rotor spinning device by means of a withdrawal tube or a clamping device in the spinning device, in particular in the drawing-off nozzle. For this purpose, the rotor spinning device has for this purpose, preferably with respect to the regular take-off direction of the yarn, a draw-off tube downstream of the draw-off nozzle and / or a clamping device arranged downstream of the draw-off nozzle. Slipping out of the yarn end of the rotor spinning device can thus be avoided even when turned off spinning device and not effective negative pressure.

According to a development of the rotor spinning machine, it is advantageous if a cover element is arranged on the rotor housing, which at least partially covers a gap between the rotor housing and the cover in the intermediate position of the cover. It is thereby possible, even with partially open lid in the rotor housing maintain a vacuum level.

For a reliable interruption of the yarn end and the preparation of the yarn end for piecing, it is also advantageous if the spinning rotor of the rotor spinning device is provided in at least a portion of its edge, preferably in two opposite portions of its edge, with a toothing or knurling. Due to the fact that only small portions of the edge are provided with the separation structure, any negative effects of the separation structure on the spin result and on the energy requirements of the spinning rotor can be largely avoided.

According to another advantageous embodiment of the rotor spinning machine, the input region of the vacuum channel is provided with at least one wear protection device, in particular a wear protection ring. Wear marks due to the action of the sucked yarn end can be avoided.

Figur 1

eine Rotorspinnvorrichtung einer Rotorspinnmaschine in einer schematischen, geschnittenen Übersichtsdarstellung,

Figur 2

eine Detaildarstellung eines Rotorgehäuses der Rotorspinnvorrichtung in einer schematischen, geschnittenen Darstellung nach einer Unterbrechung des Spinnprozesses,

Figur 3

das Rotorgehäuse der Figur 2 nach dem Einsaugen eines Garnendes,

Figur 4

eine Detaildarstellung des Rotorgehäuses nach der Garnendenvorbereitung,

Figur 5

eine Detaildarstellung des Rotorgehäuses nach dem Rückliefern des Garnendes in die Fasersammelrille und

Figur 6

eine Draufsicht auf den offenen Rand eines Spinnrotors mit einer Trennstruktur.

Further advantages of the invention will be described with reference to the embodiments illustrated below. Show it:

FIG. 1

a rotor spinning device of a rotor spinning machine in a schematic, sectional overview representation,

FIG. 2

a detailed representation of a rotor housing of the rotor spinning device in a schematic, sectional illustration after an interruption of the spinning process,

FIG. 3

the rotor housing the FIG. 2 after sucking in a yarn,

FIG. 4

a detailed representation of the rotor housing after Garnendenvorbereitung,

FIG. 5

a detailed view of the rotor housing after the return of the yarn end in the fiber collecting groove and

FIG. 6

a plan view of the open edge of a spinning rotor with a separation structure.

FIG. 1 shows a rotor spinning device 2 of a rotor spinning machine 1 in a schematic sectional view. The rotor spinning device 2 has a rotor housing 3 in the usual manner, in which a spinning rotor 5 is rotatably mounted and rotates during operation of the rotor spinning device 2 at an operating speed. The spinning rotor 5, a fiber material to be spinned F via a feed device 12 and a resolving device 21, where it is dissolved in individual fibers, supplied and stored in a fiber collecting groove 6 of the spinning rotor 5 in the form of a fiber ring. From there, it is bound in the end of the yarn G produced in the rotor spinning device 2. The yarn produced in the spinning rotor 5 is likewise withdrawn via a draw-off nozzle 7 by means of a draw-off device 11, which in the present case is formed by two draw-off rolls, and wound onto a reel 14 by means of a winding device 13. The rotor housing 3 is connected via a vacuum channel 8 to a central vacuum channel 22 of the rotor spinning machine 1 and is thereby acted upon by a spinning vacuum. The rotor housing 3 is closed during the spinning operation by means of a cover 4.

In the lid 4, the trigger nozzle 7 and, as shown in the present illustration, a trigger tube 16 is arranged. However, the withdrawal tube 16 is not absolutely necessary, and instead of the withdrawal tube 16, only one twist-blocking element can be provided, which can also be formed integrally with the withdrawal nozzle 7. However, the withdrawal tube 16 is advantageous in order to fix the yarn G in the event of an interruption of the spinning operation within the rotor spinning device 2, as will be explained below. As shown, the cover 4 of the rotor housing 3 part of a pivot housing, which also covers the opening device 21 and possibly other devices of the rotor spinning device 2. However, it can also, as in the Fig. 2-5 shown, a separate cover 4 may be provided for the rotor housing 3.

The cover 4 is presently shown in solid lines in a closed position I. From this, the lid in an intermediate position II (shown in dashed lines) can be converted, in which both a cleaning of the spinning rotor 5 and a Garnendenvorbereitung and rewinding a faulty piece of yarn can take place. Furthermore, the lid 4 can be transferred to an open position III, in which it is possible to manually clean the spinning rotor 5 or remove it from the rotor spinning device 2.

The rotor spinning device 2 shown in the present case also has a yarn monitoring device 15, by means of which at least one parameter of the finished spun yarn G is monitored. If a yarn defect is detected by the yarn monitoring device 15, the spinning process is interrupted and the already produced yarn G is rewound to some extent in order to be able to remove the defective yarn piece.

Furthermore, the rotor spinning device 2 or the rotor spinning machine 1, a control unit 17, by means of which the various devices of the rotor spinning device 2 are controlled both during normal operation and during piecing. In the present case, the winding device 13, the yarn monitoring device 15, the take-off device 11, the spinning rotor 5 and the feed device 12 are signal-transmitting connected to the control unit 17, as shown by the dotted lines.

The preparation of a yarn end 9 for piecing is now based on the FIGS. 2 to 5 shown. The method for preparing a yarn end 9 is first for a piecing after a planned interruption of Spinning operation with a controlled shutdown of the rotor spinning device 2 described. Such planned interruptions take place, for example, for maintenance purposes, for bobbin replacement, before the rotor spinning machine 1 is shut down or in the event of the detection of a yarn fault. In this case, the devices involved in yarn production of the rotor spinning device 2, which in the present case the feed device 12, the trigger device 11 and the winding device 13 include controlled so slowed to a stop that the yarn G does not tear and runs on the coil 14, but up to Interruption of the spinning process is further produced. The yarn end 9 is thus after the interruption of the spinning process at a defined position. In order to facilitate the preparation of the yarn end 9 for piecing, in the present case the devices 11, 12, 13 are braked such that the yarn end 9 is located inside the draw-off nozzle 7.

In FIG. 2 the rotor spinning device 2 or the rotor housing 3 is shown in a situation in which the spinning process has just been interrupted and the yarn end 9 is located inside the draw-off nozzle 7. The cover 4 of the rotor housing 3 is still closed at this time. However, the method for preparing a yarn end 9 for piecing is also applicable in the case of an unplanned interruption of the spinning operation, for example by a yarn breakage. In this case, the yarn end 9 runs on the spool 14 and from there either by an operator or by an automatic maintenance device which can be arranged to be movable or stationary on the rotor spinning machine 1, and in the rotor spinning device 2, in this case through the exhaust pipe sixteenth , to be led back. After the yarn end 9 has been sucked into the rotor spinning device 2, it is also approximately in the position shown. Of course, both after a planned and after an unplanned interruption of the spinning operation, it is also possible for the yarn end 9 to be located at another point within the rotor spinning device 2, for example inside the withdrawal tube 16. Especially advantageous however, for the following sucking of the yarn end 9, the position within the drawing nozzle 7.

Now that the yarn end 9 is located at the defined position within the discharge nozzle 7, it can be inserted into the vacuum channel 8, which in FIG. 3 is shown. For this purpose, the cover 4 is moved from its closed position I into its intermediate position II, so that the yarn end 9 can be sucked into it by the action of the negative pressure in the vacuum channel 8. In order to maintain a sufficient negative pressure in the rotor housing 3 even in the intermediate position II, in the present case a cover element 18 is arranged on the rotor housing 3 which at least partially covers the gap 19 between the rotor housing 3 and the cover 4 located in the intermediate position II. Furthermore, at the in FIG. 3 illustrated negative pressure channel 8 a wear protection device 20 can be seen. This is presently designed as a wear protection ring made of a metal, which is inserted into the inlet region of the vacuum channel 8 at the transition to the rotor housing 3 in order to protect it from being cut by the yarn G during suction.

In order to provide the additional yarn length required for the suction, the yarn G is meanwhile removed from the spool 14, in the present case by means of the draw-off device 11, against the regular withdrawal direction AR (see FIG. Fig. 1 ). The yarn end 9 now takes the in FIG. 3 shown course, in which it is held securely due to the negative pressure in the vacuum channel 8. The yarn end 9 lies directly next to the open edge of the spinning rotor 5 or touches it straight so that now the yarn end preparation can be made.

Optionally, 9 may be performed before sucking the yarn end still a rotor cleaning. For this purpose, for example, through the open gap 19 between the cover 4 and the rotor housing 3, a blowing nozzle (not shown) are introduced into the rotor housing 3 to the fiber collecting groove 6 of the spinning rotor 5 blow out. However, in particular in the case of a controlled interruption of the spinning process, this is not absolutely necessary, since due to the gradual reduction of the feed hardly fibers in the fiber collecting groove 6 can deposit.

In order to interrupt the yarn end 9 and to prepare for piecing, the spinning rotor 5 is now set in rotation and driven for a certain period of time with a defined Garnendenvorbereitungsdrehzahl. While the spinning rotor 5 is operated at an operating speed between about 80,000 rpm and 170,000 rpm, it is advantageous for yarn end preparation to provide a much lower yarn end preparation speed between 20,000 and 50,000 rpm per minute. In this way, on the one hand a secure interruption of the yarn end 9 and on the other hand sufficient fibrillation and alignment of the fibers can be ensured. On the other hand, if the yarn preparation speed is too fast, the yarn end 9 may be severed too quickly and thus insufficient yarn end preparation. The period of time during which the spinning rotor 5 is driven for yarn end preparation may preferably be preset depending on the kind of the fiber material F used and the kind of the yarn G produced. Usually, the time for successful preparation of the yarn end 9 is about 5 seconds, but for more difficult to cut yarns G, such as coarse yarns, the time may be more than 5 seconds.

According to the example shown in the present case, it is further provided to move the yarn end 9 at least briefly during yarn preparation in its longitudinal direction by means of the take-off device 11, on the one hand to assist in interrupting the yarn end 9 and, on the other hand, to ensure a sufficient length of the prepared yarn end 9. The extraction device 11 is driven to oscillate, depending on the type of yarn G and the desired length of the prepared Yarn 9 a movement between 2 mm and 10 mm can be performed.

Now that the yarn end 9 has been successfully interrupted by the open edge of the spinning rotor 5 and prepared for piecing, it takes the in FIG. 4 shown position. The separated yarn end 9 was sucked through the vacuum channel 8 and the central vacuum channel 22 of the rotor spinning machine 1 and disposed of, while the newly formed yarn end 9 is now ready for piecing, which later with reference to FIG. 5 is described.

Similarly, yarn end preparation occurs upon detection of a yarn defect by the yarn monitoring device. This is, as previously based on the FIG. 2 described, the rotor spinning device 2 controlled stoppages, so that the yarn end 9 in the in FIG. 2 is shown position. As described above, the yarn end 9 is sucked back into the vacuum channel 8 with return of the yarn G and is located in the in FIG. 3 position shown. In order to separate out the defective piece of yarn from the yarn G, the yarn G will continue to be opposite to the regular withdrawal direction AR (see FIG FIG. 1 ) unwound from the spool 14 and continuously sucked into the vacuum channel 8 until the defective piece of yarn is completely sucked into the vacuum channel 8. The safe suction of the complete, faulty piece of yarn can be ensured, for example, by the number of revolutions of the take-off rolls of the take-off device 11.

For rewinding the defective piece of yarn, preferably the take-off device 11 is driven somewhat faster relative to the peripheral speed or the transport speed of the yarn G than the winding device 13, so that the yarn G is kept under tension and so-called back-loops, a rear winding of the yarn Garnes G when rewinding, can be avoided. For the safe sucking To support the yarn end 9 in the vacuum channel 8, the winding device 13 is preferably provided with a soft start control, so that the spool 14 and thus the yarn G is not jerky, but gradually accelerated. It is therefore also advantageous if the speed of the yarn G is adjustable during rewinding. As a result, yarns G, which are more difficult to introduce into the vacuum channel 8 due to their structure or diameter, can be rewound at a slower speed. It may therefore also make sense that the negative pressure level in the vacuum channel 8 is adjustable. This makes it possible, the vacuum level, for example, for sucking the yarn ends 9 both for Garnendenvorbereitung and for rewinding to eliminate a yarn defect, to increase in the short term or to adapt to the nature of the yarn G. For example, in yarns which are relatively difficult to sever, the level of vacuum can be increased to keep these yarns taut and to facilitate interruption by means of the open edge of the spinning rotor.

Now that the defective piece of yarn is completely sucked into the vacuum channel 8, the take-off device 11 and the winding device 13 are stopped and the spinning rotor 5 in turn driven at the Garnendenvorbereitungsdrehzahl to prepare the yarn end 9. The yarn end 9 takes again in the FIG. 4 shown course.

In order to spin the yarn end 9 again, according to a particularly advantageous embodiment, it is only necessary to transfer the lid 4 from the intermediate position II back into the closed position I. The yarn end 9 is hereby dropped into the fiber collecting groove 6 of the spinning rotor 5 and can connect to the existing there due to the already re-starting feed fibers. The possibly required additional length of the yarn end 9 can be provided by changing the position of the yarn end 9 when closing the lid 4. However, it is also possible, a required additional yarn length to provide by a short-term drive of the trigger device 11 against the regular withdrawal direction AR.

For piecing the spinning rotor 5 is operated in a conventional manner with a reduced compared to the regular operating speed Anspinndrehzahl, which may for example be about 60% to 80% of the operating speed. As a result, during the run-up of the drives, the fiber feed, the yarn formation and the yarn take-off can be better coordinated with each other. After the successful piecing, finally, the regular spinning process can be started, whereby the spinning rotor 5 is accelerated to its regular operating speed.

FIG. 6 finally shows a plan view of the open edge of a spinning rotor 5, which is equipped with separation structures 10 for breaking and preparing a yarn end 9 for piecing. In the present case, the edge of the spinning rotor 5, arranged opposite one another, has two partial areas of its length, which are provided with a separating structure 10. The separation structure 10 is in each case formed by a knurling with a plurality of adjacent notches. However, other embodiments of the separation structure 10 are also possible.

By means of the described method, it is possible to reproducibly achieve a very good yarn preparation even in different applications as well as in different types of rotor. In particular, the length of the prepared yarn end 9 is subject to extremely small fluctuations. In addition, a very uniform resolution of the yarn end and orientation of the fibers can be achieved by the separating structure 10, in particular in connection with the movement of the yarn end 9 in its longitudinal direction, so that piecers of high quality can be produced. It is particularly advantageous that all of the described processes from the rotor cleaning, the sucking of the yarn end 9 to the rewinding of a defective Garnstücks in the intermediate position II of the lid. 4 can be carried out, whereby a considerable time savings can be achieved.

LIST OF REFERENCE NUMBERS

1

Rotor spinning machine

2

Rotor spinning device

3

rotor housing

4

cover

5

spinning rotor

6

Fiber collecting groove of the spinning rotor

7

navel

8th

Vacuum channel

9

yarn

10

separation structure

11

off device

12

feeder

13

spooling device

14

Kitchen sink

15

Garnüberwachungseinrichtung

16

draw-off tube

17

control unit

18

cover

19

gap

20

Wear protective device

21

dissolver

22

central vacuum channel

I

closed position

II

Half open position

II

open position

AR

withdrawal direction

DR

regular direction of rotation

F

fiber material

G

yarn

Claims (15)

Method for preparing a yarn end (9) for piecing on a rotor spinning device (2) of a rotor spinning machine (1) with a rotor housing (3) which can be closed with a cover (4) and acted upon by a negative pressure channel (8) with a negative pressure, with one in the Rotor housing (3) rotatably mounted and spinning during the spinning operation at an operating speed spinning rotor (5) and with a take-off nozzle (7), wherein in the process the yarn end (9) to be prepared in the vacuum channel (8) is introduced and by a separating structure (10 ) is interrupted the open edge of the rotating spinning rotor (5) and characterized vorbereitetet for piecing, characterized in that the spinning rotor (5) during the interruption of the yarn (9) is driven with a defined yarn ends preparation speed, the yarn ends preparation speed equal to the operating speed of the Spinning rotor (5) or less than the operating speed of the spinning rotor (5) Preferably, the yarn end preparation speed is less than 80%, preferably less than 65%, and more preferably less than 55% of the operating speed, and is preferably less than a piecing speed of the spinning rotor (5). Method according to the preceding claim, characterized in that the cover (4) of the rotor housing (3) before the insertion of the yarn end (9) in the vacuum channel (8) in an intermediate position (II) is transferred to prepare the yarn end (9) standing spinning rotor (5) is inserted into the vacuum passage (8), the spinning rotor (5) is rotated and driven for a predetermined period of time with the Garnendenvorbereitungsdrehzahl, wherein the yarn end (9) is interrupted, and only after the interruption of the yarn end (9) the lid (4) is transferred to a closed position (I), preferably the predetermined period of time during which the spinning rotor (5) is driven at the Garnendenvorbereitungsdrehzahl , is adjusted depending on a kind of the produced yarn (G) and / or the spinning rotor (5). Method according to one of the preceding claims, characterized in that in the event of a plannable interruption of the spinning operation on the yarn manufacturing involved devices, at least one feed device (12) and a winding device (13) are controlled slowed down to a standstill that the yarn end (9 ) is located after the controlled braking of the devices within the rotor spinning device (2), in particular within the draw-off nozzle (7). Method according to the preceding claim, characterized in that the yarn end (9) unwound after controlled braking against its regular withdrawal direction (AR) of a coil (14), in the vacuum channel (8) of the rotor spinning device (2) is inserted and rewound, until a defective piece of yarn is completely sucked into the vacuum channel (8), and then the yarn end (9) is prepared for piecing, preferably for rewinding the yarn end (9) the winding device (13) and the take-off device (11) counter to their regular direction of rotation (DR) and against the regular withdrawal direction (AR) are driven and the trigger device (11) is driven at a higher speed than the winding device (13). Method according to one of the preceding claims, characterized in that for the controlled braking of the spinning rotor (5) first of its operating speed to a braking speed, which is lower than the operating speed is brought and is driven for a predetermined period of time with the Abbremsdrehzahl and only then decelerated to a stop, preferably wherein the Abbremsdrehzahl is equal to or less than a piecing speed of the spinning rotor (5). Method according to one of the preceding claims, characterized in that after the transfer of the lid (4) into the intermediate position (II) and before the insertion of the yarn end (9) of the spinning rotor (5) is subjected to a cleaning, in particular a pneumatic cleaning. Method according to one of the preceding claims, characterized in that a vacuum level in the vacuum channel (8) during the preparation of the yarn end (9) is adjusted, in particular depending on a type of yarn produced (G) is set and / or the negative pressure level in the vacuum channel (8) is at least briefly increased before the introduction of the yarn end (9) in the vacuum channel (8). Method according to one of the preceding claims, characterized in that the yarn end (9) during its interruption by means of a take-off device (11) is moved in its longitudinal direction. Method according to one of the preceding claims, characterized in that the yarn end (9) at standstill of the rotor spinning device (2) after controlled deceleration by means of a take-off tube (16) or a clamping device in the rotor spinning device (2), in particular in the draw-off nozzle (7). , is fixed. Rotor spinning machine (1) with at least one rotor spinning device (2) with a rotor housing (3) which can be closed with a cover (4) and acted upon by a vacuum channel (8) with a negative pressure, with a spinning rotor (5) rotatably mounted in the rotor housing (3) and with a draw-off nozzle (7), one edge of the spinning rotor (5) having a separating structure (10) for breaking and preparing a yarn end (9) for piecing introduced into the vacuum channel (8), characterized in that the rotor spinning machine (1) and / or the rotor spinning device (2) has a control unit (17) by means of which the rotor spinning device (2) according to one of the preceding claims is operable. Rotor spinning machine according to the preceding claim, characterized in that the cover (4) of the rotor housing (3) in a closed position (I), an open position (III) and an intermediate position (II) can be brought, preferably on the rotor housing (3) a Covering element (18) is arranged, which in the intermediate position (II) of the lid at least partially covers a gap (19) between the rotor housing (3) and the lid. Rotor spinning machine according to one of the two preceding claims, characterized in that a vacuum level in the vacuum channel (8) is adjustable. Rotor spinning machine according to one of claims 10 to 12, characterized in that an input region of the vacuum channel (8) is provided with at least one wear protection device (20), in particular a wear protection ring. Rotor spinning machine according to one of claims 10 to 13, characterized in that the spinning rotor (5) in at least a portion of its edge, preferably in two opposite Part areas of its edge, with a toothing or knurling as a separation structure (10) is provided. Rotor spinning machine according to one of claims 10 to 14, characterized in that the rotor spinning device (2) with respect to the regular take-off direction (AR) of the yarn one of the trigger nozzle (7) downstream vent tube (16) and / or one of the trigger nozzle (7) downstream clamping device for the yarn.

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