GB2358878A

GB2358878A - Apparatus for feeding slivers to a spinning machine including drive motors whose speeds are jointly adjustable

Info

Publication number: GB2358878A
Application number: GB0102592A
Authority: GB
Inventors: Guenter Duda
Original assignee: Truetzschler GmbH and Co KG
Current assignee: Truetzschler GmbH and Co KG
Priority date: 2000-02-03
Filing date: 2001-02-01
Publication date: 2001-08-08
Anticipated expiration: 2021-02-01
Also published as: ITMI20010122A1; FR2804694A1; FR2804694B1; GB2358878B; CN1265040C; DE10004604B4; JP4620264B2; DE10004604A1; JP2001234436A; CH695316A5; CN1319688A; GB0102592D0

Abstract

An apparatus for feeding slivers to a spinning machine - e.g. an autoleveller draw frame - includes sliver cans 5, mounted at a feed table 6 (creel), out of which slivers 7 are drawn over driven feed rollers 8 and at least two adjustable speed drive motors 17 which are connected to a common converter 18 - e.g. a frequency converter or a direct current (d.c.) converter - the speeds of the motors being jointly adjustable. The apparatus disclosed permits compensation for load-dependent variations in speed in a simple manner. Also described is a method for controlling a feed arrangement for a spinning machine which includes the step of adjusting at least two drive motors, fed by a common converter, to be substantially the same as a desired speed.

Description

A 1 1 2358878 Apparatus for feedinQ slivers to a sipinning machine The

invention relates to an apparatus for feeding slivers to a spinning machine, especially a draw frame, for example, an autoleveller draw frame.

DE 198 09 875 describes an apparatus in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds are provided. A drive motor having speed control means is associated with each feed roller at the feed table of the draw frame, so that the circumferential speed of the feed rollers is individually adjustable. Where there are several variable-speed drive motors. different circumferential speeds can be set.

It is an aim of the invention further to improve such a machine, and in particular to provide a machine in which load-dependent variations in speed can be substantially compensated for in a simple manner.

The invention provides an apparatus for feeding slivers to a spinning machine, comprising a feed table having a plurality of driven feed rollers over which the slivers can be drawn out of respective sliver cans, the 1 2 - apparatus further comprising at least two drive motors having adjustable speeds, wherein said drive motors are connected to a common converter, the speeds of said drive motors being jointly adjustable.

The measures according to the invention, in particular in the case of a draw frame, enable load-dependent variations in speed to be substantially compensated for or avoided in a simple manner. Although threephase induction motors have a load-dependent speed characteristic on account of slip, the risk inherent is avoided. Within the feed table, in this of a wrong draft the slivers should not exhibit any inadmissible deviations from the entry tension, f irstly in relation to one another and secondly with regard to the different spacing between the feed rollers and the entry roller pair of the downstream drafting arrangement. According to the invention, despite loading, a desired speed (target speed) of the drive motors can be realised almost completely, or entirely, so that wrong drafts are avoided. On transfer of the driving power of the feed rollers to the slivers, differences in friction imposed by the fibre material are additionally compensated for. Although in practice the frictional force decreases from cotton (which may contain lubricants, sticky substances and so on) through mixtures of cotton and synthetic fibres to 3 pure synthetic fibres (which have a smooth surface), reliable and effective transfer of the driving power to the slivers is achieved by the measures in accordance with the invention, regardless of the fibre material being processed. It is a particular advantage that the configuration of the apparatus is very simple.

At least two drive motors are advantageously associated with the feed rollers of the feed table of the draw frame. A drive motor is advantageously associated with each feed roller. Advantageously, at least one drive motor is associated with the feed rollers and at least one drive motor is associated with the roller pairs of the drafting arrangement for the preliminary draft. The drive motor is preferably a frequency-controlled, three-phase asynchronous motor. The drive motor is advantageously a three- phase synchronous motor. By the nature of the system, there are no speed variations with this motor. The drive motor is preferably a reluctance motor. During runup (acceleration), this motor behaves like a three-phase asynchronous motor, and subsequently (during operation) like a synchronous motor, so that no speed correction is required. The drive motor is advantageously a power converter-controlled d.c. motor. The feeding converter in this case generates a speed -proport i onal voltage. The 4 drive motor is preferably a geared motor. The drive motor is advantageously an internal-rotor motor (standard motor) The drive motor is preferably an external-rotor motor (friction-drum motor). The feeding converter advantageously generates a speed-determining voltage of variable magnitude and frequency. The converter is preferably a frequency converter. The converter is advantageously a d.c. current converter. The converter preferably has a set-point adjuster, for example, a potentiometer, selection of the set-point being by control device. A speed sensor, for example, a tachometer generator, is advantageously present. Several speed sensors, for example, tachometer generators, are preferably present, downstream of which there is an averaging device.

One drive motor is advantageously equipped with a speedproportional transducer. one roller, for example, a feed roller, is preferably equipped with a speed-proportional transducer. The one drive motor or the one roller, here acting for all drive motors or rollers in use, is equipped with the transducer. The transducer is advantageously connected to the converter and influences the output voltage and/or frequency of the converter, such that variations from a desired value are kept to a minimum. More than one actual speed value sensor is preferably :D present, in order to determine a mean actual speed of several rollers and/or drive motors. The calculated mean speed variation advantageously influences the frequency and/or the output voltage of the feeding converter. The drive motor is preferably a d.c. motor, the feeding converter generating a speed-proportional voltage. The speed-proportional voltage is advantageously additionally regulated by an actual speed value sensor. The desired speed value is preferably formed proportional to the speed of the drafting arrangement entry roller. Drive motors having the same speed characteristic are advantageously used for driving the feed rollers. The speeds of the drive motors for the feed rollers are preferably the same or virtually the same. At the same or virtually the same speed of the drive motors for the feed rollers, different circumferential speeds of the feed rollers are advantageously achieved in the working direction.

The invention includes a further advantageous arrangement for feeding slivers to spinning machines, especially draw frames, for example, autoleveller draw frames, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having 1 6 - adjustable speeds are provided, in which case the drive motors are uncontrolled asynchronous motors, are fed by a common converter and the speeds thereof are jointly adjustable. In accordance with a further advantageous apparatus for feeding slivers to spinning machines, especially draw frames, for example, autoleveller draw frames, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds are provided, the drive motors are uncontrolled d.c. motors, are fed by a common converter and the speeds thereof are jointly adjustable.

The invention also provides an apparatus for feeding is slivers to a spinning machine, especially a draw frame, for example, an autoleveller draw frame, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds are provided, wherein the drive motors are fed by a common converter and the speeds are jointly adjustable such the drive motors have negligible or no variations from a desired speed.

1 - 7 Moreover, the invention provides a method for controlling a feed arrangement for a spinning machine, in which a plurality of slivers are drawn out of respective sliver cans over respective feed rollers, and the speeds of at least two drive motors fed by a common converter are jointly adjusted so as to be substantially the same as a desired speed.

Certain illustrative embodiments of the invention will be described in detail hereinafter with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic side view of a draw f rame having an embodiment of the apparatus in accordance with the invention, in which a drive motor (internal-rotor motor) is associated with each feed roller at the feed table,

Fig. 2 is a plan view of the feed table shown in Fig. 1 with externalrotor motors; Fig. 3 is a plan view of a draw frame as shown in Fig. 1 including a further embodiment in accordance with the invention, in which a drive motor is associated with the feed rollers and a drive motor is associated with the roller pairs of the drafting arrangement for the preliminary draft; - 8 U Fig. 4 is a schematic view of a draw frame arranged as an autoleveller draw frame, together with a block diagram; Fig. 5 is a block diagram of a speed regulating means of the drive motors for the feed rollers of a feed table, in which a tachometer generator is connected to one feed roller, and a common converter is provided; Fig. 6 is a block diagram of a speed regulating means of the drive motors for the feed rollers of a feed table, in which a tachometer generator is connected to each feed roller, and an averaging device and common converter are provided; Figs. 7a and 7b are graphs showing the speed regulation in the case of three load-dependent asynchronous motors for feed rollers.

With reference to Fig. 1 a draw frame, for example, of the kind known as an HSR (trade mark) manufactured by Tratzschler GmbH & Co KG, has an entry region 1, a measuring region 2, a drafting arrangement 3 and a sliver lay region 4. In the entry region 1, three spinning cans Sa to 5c (round cans) of a draw f rame having two rows of cans (see Fig. 2) are arranged beneath the sliver feed table 6 (creel), and the supply slivers 7a to 7c are drawn off over feed rollers 8a to 8c and supplied to the drafting arrangement 3. A co-rotating top roller 9a to 9c is - 9 associated with each driven feed roller 8a to 8c. In the region of the feed table 6 there are six roller pairs 8, 9 (Fig. 2), each consisting of a top roller and a feed roller. Slivers 7a to 7c are lifted out of the spinning cans 5a to Sc and guided on the f eed table 6 to the draw frame. After passing through the drafting arrangement 3, the drawn sliver enters a revolving plate of a can coiler and is laid in coils in the delivery can 11. The feed table 6 extends as far as the draw frame over the region of the entire sliver feed apparatus. Via the sliver feed apparatus, a sliver 7 is drawn from each spinning can 5 in direction B, and the feed to the draw frame is effected through a respective sliver entry point, each of which comprises a roller pair 8a, 9a; 8b, 9b; 8c, 9c (roller feed). In the region of each lower roller 8a to 8c there is a respective guide element 10a, 10b, 10c for guiding the slivers 7. The reference letter A denotes the running direction of the slivers 7a, 7b and 7c from the feed rollers towards the drafting arrangement 3. The slivers 7a to 7c are squeezed between the roller pairs 8, 9. Especially at a high drawing-off speed, the slivers drawn out of the spinning cans Sa. to 5 oscillate above the cans 5a, to 5c in a balloon-like form. After running through the feed rollers 8a to 8c, the slivers 7a to 7c are steadied in 1 - transit. The direction of rotation of the feed rollers 8a to 8c and of the top rollers 9a to 9c is denoted by the curved arrows C, D. Arranged downstream of the feed table 6 at the entry to the draw frame there is a driven roller arrangement, for example, two bottom rider rollers 12 and, arranged side by side, three top rider rollers 13. Each feed roller 8 is driven by its own drive motor 17a to 17f, which is in the form of an internal-rotor motor (standard motor), for example, a f requency- controlled three-phase asynchronous motor. The drive motors 17a to 17f are all connected up to a common converter 18, for example, a frequency converter, having a set-point generator 19. The feed rollers 8a to 8c are of the same diameter, for example mm. The speeds n of the motors 17a, 17b and 17c decrease in the working direction A, that is, nj > n2 > n3 (motor 17a has speed nj, motor 17b has speed n2, motor 17c has speed n3) The speeds ni, n2 and n3 are predetermined by the open loop and closed loop controlling system 20, for 3 that is to say, U, = 282 m/min, U2 = 267 m/min, U3 = 251 m/min.

The same applies to the drive motors 17d, 17e, 17f (Fig.

2). In this way, the circumferential speeds U of the feed rollers decrease in the working direction A. It is therefore possible to set the circumferential speeds U,, U2, example, nj = 900 min-', n = 850 min n = 800 min 11 U3 Of the feed rollers 8 in such a say that the entry tension of all slivers 7 is made the same or virtually the same in the desired manner. Alternatively, all the drive motors 17a to 17c (and the drive motors 17d to 17f not illustrated in Fig. 1) can have the same speed n, hence producing an economical embodiment. To provide a (slightly) decreasing circumferential speed U of the feed rollers 8a, to 8c (and 8d to 8f) in the working direction A, the outer diameters d of the feed rollers 8a to 8c (and 8d to 8f) are correspondingly different.

In the embodiment of Fig. 2, on each side of the feed table 6 a row of three spinning cans 5 is set up so that they are parallel to one another. In operation, a sliver can be drawn off from all six spinning cans Sa to 5f simultaneously. Alternatively, the procedure in operation can be such that sliver is drawn off only on one side, for example, from the three spinning cans Sa to 5c, whilst on the other side the three spinning cans 5d to 5f are being exchanged. Furthermore, on each side of the feed table 6 there are three feed rollers 8a to 8c and 8d to 8f respectively arranged one behind the other in the working direction A. Two feed rollers in each case are arranged coaxially with respect to one another. The feed rollers 8a to 8f are each driven by their own variable-speed - 12 electric motor 17a to 17f. The electric motors 17a to 17f are connected up to a common electrical open loop and closed loop controlling system 40 (see Fig. 4), for example, a microcomputer. In Fig. 2, the drive motors 17a to 17f associated with the feed rollers and which are in the form of external-rotor motors (friction-drum motors) are connected up to the common converter 18. The drive motors 17a to 17f expediently have the same speed n. To achieve a (slightly) decreasing circumferential speed U in the working direction A, the outer diameters of respective pairs 8a and 8d, 8b and 8e, and 8c and 8f of feed rollers are different. Alternatively, when the drive motors 8a to 8f have the same outer diameter, drive motors of different speeds n are selected.

According to the diagrammatic illustration of a further embodiment in Fig. 3, eight feed rollers 8 are present, each of which is associated with a spinning can (not shown). All feed rollers 8 are driven by a common drive motor 17, for example, a three-phase synchronous motor, mechanical transmission elements (not shown) such as toothed belts, toothed belt wheels, gears and the like being provided between the feed rollers 8 and the drive motor 17. Different bevel gears enable a uniform drafting tension to be achieved. The drive of the f eed table 6 C (creel) is effected by a variable-speed drive motor 17. In the drafting arrangement 3, the bottom rollers III and II of the roller pairs 111/28 and 11/27 for the preliminary draft are driven by the variable-speed drive motor 20. drive motors 17 and 20 are jointly connected up to the converter 18 and are fed by the converter 18.

With reference to Fig. 4, a draw frame, for example, a draw frame of the kind manufactured by Tratzschler GmbH & Co KG and known as the HSR (trade made), comprises a drafting arrangement 3, upstream of which is arranged a drafting arrangement inlet 2 and downstream of which is arranged a drafting arrangement outlet 4. The slivers 7, coming from cans (see Figs. 1 and 2), enter the sliver guide 21 and, drawn by the draw-off rollers 22, 23 are transported past the measuring element 24. The drafting arrangement 3 is designed as a 4-over-3 drafting arrangement, that is, it consists of three bottom rollers I, II, III (the bottom delivery roller I, the middle bottom roller II and the bottom entry roller III), and four top 20 rollers 25, 26, 27, 28. The drawing of the composite sliver 71 comprising several slivers 7 takes place in the drafting arrangement 3. The draft comprises the preliminary draft and the main draft. The roller pairs 28/111 and 27/11 form the preliminary draft zone and the - 14 roller pairs 27/11 and 25, 26/1 form the main draft zone. At the drafting arrangement outlet 4, the drawn slivers reach a web guide element 29 and are drawn by means of the draw-off rollers 30, 31 through a sliver funnel 32 in which they are condensed to one sliver 711, which is subsequently laid in cans (see Fig. 1, position 11).

The draw-off rollers 22, 23, the bottom entry roller III and the middle bottom roller II, which are mechanically coupled, for example, by way of toothed belts, are driven by the variable-speed motor 20, wherein it is possible to set a desired value. (The associated respective top rollers 27 and 28 co-rotate) The delivery bottom roller I and the draw-off rollers 30, 31 are driven by the main motor 33. The variable-speed motor 20 and the main motor 33 each have their own governor 34 and 35 respectively.

Regulation (speed governing) is effected in each case by way of a closedloop control circuit, a tachometer generator 36 being associated with the governor 34 and a tachometer generator 37 being associated with the main motor 33. At the drafting arrangement inlet 2, a variable, proportional to the mass, for example, the cross-section of the fed-in slivers 7, is measured by the measuring element 24 at the inlet, which measuring element is known, for example, from DE-A44 04 326. At the drafting arrangement outlet 4, the cross-section of the exiting sliver 711 is recorded by a measuring element 38 at the outlet associated with the sliver funnel 32, which measuring element is know, for example, from DE-A-195 37 983. A central (open loop and closed loop controlling system a icrocomnuter with microprocessor processor 40 ), for example, transmits an adjustment of the desired variable for the variable speed motor 20 to the governor 34. The measured variables of the two measuring elements 24 and 38 are communicated to the central processor 40 during the drafting operation. The desired value for the variable-speed motor 20 is determined in the central processor 40 from the measured variables of the measuring element 24 at the inlet and from the desired value for the cross-section of the exiting sliver 711. The measured variables of the measuring element 38 at the outlet serve for monitoring the exiting sliver 711 (delivered sliver monitoring). By means of this control system, it is possible to compensate for variations in the cross-section of the fed-in slivers 7 by appropriate adjustments to the drafting process and evening-out of the sliver 711 by the inventive measures can be achieved in that wrong drafts of the slivers 7 can already by reduced or avoided in the region of the feed table 6. Associated with the central computer unit 40 of the machine is a memory 39, 16 - where the or certain signals of the open loop and closed loop controlling system are filed for evaluation. Furthermore, connected up to the processor 40 is a function converter 41, for example, a level converter, computer or the like, which is electrically connected to the converter 18 for the variable-speed electric motors 17a to 17f. The speed of the electric motors 17a to 17f is set on the basis of desired values pre- settable in the memory 39 for the set-point generator 19. The common converter 18 changes the speed of the drive motors 17 and 20 simultaneously with a change in the feed, for example, when the machine accelerates or decelerates, and also when there is a change during continuous operation. Variation in the speed of the drive motor 20 (regulating motor) for regulation, which is comparatively small and serves for correcting the thickness of the sliver 71, is effected additionally.

In the embodiment of Fig. 5, three drive motors 17a, 17b and 17c for feed rollers 8a, 8b and 8c are present, the feed roller 8c, acting for all feed rollers, being connected by way of a shaft 44 to a tachometer generator 43 as speed - proportional sensor. The tachometer generator 43 is connected to the frequency converter 18, to which the set-point generator 19 is connected. The drive motors 17a to 17c are arranged downstream of the frequency converter 18. Via the input of the actual speed into the frequency converter 18, the tachometer generator 43 influences the output voltage and the frequency of the frequency converter 18 (f eed converter) in order to keep to a minimum any variation in the speeds of the drive motors 17a to 17c from a desired speed value, which is pre-set by the speed setter 19.

In a further embodiment, shown in Fig. 6, a tachometer generator 43a, 43b, 43c is connected up to a respective drive motor 17a, 17b, 17c, for example, a frequency controlled asynchronous motor (three-phase induction motor); downstream of the tachometer generators there is a common averaging device 44, which is connected up to the frequency converter 18. The drive motors 17a. to 17c are connected downstream of the frequency converter 18. The frequency converter 18 has a set-point generator 19 for the desired speed value ndesi,d, which is connected to the open loop and closed loop control system 40. The desired speed value ndesired is formed proportional to the speed of the 20 drafting arrangement entry roller III (see Fig. 4). A mean actual speed nmean Of several feed rollers 8a to 8c is determined by the several tachometer generators 43a to 43c (actual speed value sensors) and the averaging device 44. The calculated mean speed variation influences the frequency and/or the output voltage of the feed converter 18. Figures 7a and 7b show examples of the mode of operation of the construction shown in Fig. 6. Corresponding to Fig. 7a, the actual speed values measured by the tachometer generators 43a to 43c are: n, = 470 rpm for feed roller 8a, n2 = 460 rpm for feed roller 8b, and n3= 480 rpm for feed roller 8c. Determined by their construction, on being loaded the three- phase asynchronous motors 17a to 17c modify their speed nj, n2, n3 respectively in dependence on the load. This variation from the desired speed ndesired is known as slip. From the actual speeds nj, n2, and n3 a mean speed nm,an = 470 rpm is calculated by the averaging device 44 and compared in the converter 18 with the desired speed ndesired = 500 rpm. The output voltage and/or frequency is correspondingly adapted and f ed into the drive motors 17a, 17b and 17c, which hence reach new actual speed values: n11 = 500 rpm for feed roller 8a, n'2 = 490 rpm for feed roller 8b and n'3 = 510 rpm for feed roller 8c. The level of the actual speeds is jointly shifted from n to n, The new actual speeds n'2 and n'3 vary only slightly from the desired speed value ndesired, the actual speed n11 is the same as the desired speed value ndesired- In this way the load-dependence is 19 - largely, that is, almost completely, compensated for in a simple manner.

Synchronous motors, which do not need sensors (tachometer generators), can also be used. Regulation is not necessary in this case, because three-phase synchronous motors have no slip. All drive motors 17a to 17f are jointly adjustable in operation by the converter 18 to a desired speed, for example, ndesired = 500 rpm, by way of the set-point generator 19.

If d.c. motors are used as drive motors, then regulation is required (analogous to Figs. 5 and 6) in order largely to compensate for the load dependence.

According to the invention, load-dependent variations in speeds are compensated for in a simple manner, the drive motors are fed by a common converter and the speeds are jointly adjustable, consequently producing a loadindependent speed of the drive motors.

Claims

1. An apparatus for feeding slivers to a spinning machine, comprising a feed table having a plurality of driven feed rollers over which the slivers can be drawn out of respective sliver cans, the apparatus further comprising at least two drive motors having adjustable speeds, wherein said drive motors are connected to a common converter, the speeds of said drive motors being jointly adjustable. 10

2. An apparatus according to claim 1, in which the arrangement is such that said drive motors are jointly adjustable so as to more closely correspond to a desired speed.

3. An apparatus according to claim 1 or claim 2, in which is the arrangement is such that said drive motors are jointly adjustable so as to be substantially the same as said desired speed.

4. An apparatus according to any one of claims 1 to 3, in which at least two drive motors are associated with the feed rollers of the feed table of the spinning machine.

5. An apparatus according to claim 4, in which a drive motor is associated with each feed roller.

6. An apparatus according to any one of claims 1 to 5, in which at least one drive motor is associated with the feed 1 - 21 rollers and at least one further drive motor is associated with roller pairs of a preliminary drafting zone downstream of the feed rollers.

7. An apparatus according to any one of claims 1 to 6, in which at least one said drive motor is a frequency controlled, three-phase asynchronous motor.

8. An apparatus according to any one of claims 1 to 7, in which at least one said drive motor is a three-phase synchronous motor.

9. An apparatus according to any one of claims 1 to 8, in which at least one said drive motor is a reluctance motor.

10. An apparatus according to any one of claims 1 to 10, in which at least one said drive motor is a power converter-controlled d.c. motor.

11. An apparatus according to any one of claims 1 to 10, in which at least one said drive motor is a geared motor.

12. An apparatus according to any one of claims 1 to 11, in which at least one said drive motor is an internal-rotor motor (standard motor).

13. An apparatus according to any one of claims 1 to 12, in which at least one said drive motor is an external-rotor motor (friction-drum motor).

in 16 in 17 in 10 of 18 poi 19 in 20

14. An apparatus according to any one of claims 1 to 13, in which the feeding converter generates a speed determining voltage of variable magnitude and/or frequency.

15. An apparatus according to any one of claims 1 to 14, which the converter is a frequency converter.

An apparatus according to any one of claims 1 to 14, which the converter is a d.c. current converter.

An apparatus according to any one of claims 1 to 16, which the converter has a set-point generator selection the set-point being by control device.

An apparatus according to claim 17, in which the set nt generator is a potentiometer.

An apparatus according to any one of claims 1 to 18, which a speed sensor is present.

An apparatus according to claim 19, in which several speed sensors are present, downstream of which there is an averaging device.

21. An apparatus according to claim 19, in which the or each speed sensor is a tachometer generator.

22. An apparatus according to any one of claims 1 to 21, in which one drive motor is equipped with a speed proportional transducer.

23 23. An apparatus according to any one of claims 1 to 22, in which one feed roller is equipped with a speedproportional transducer.

24. An apparatus according to claim 22 or claim 23, in which the or each transducer is connected to the converter and the speeds of the drive motors can be so influenced by the frequency and/or output voltage of the converter that variations from a desired value (ndesi,,,d) are kept to a minimum.

25. An apparatus according to any one of claims 1 to 24, in which a plurality of actual speed value sensors are present, in order to determine a mean actual speed of a plurality of rollers and/or drive motors.

26. An apparatus according to claim 25, in which the arrangement is such that the calculated mean speed variation influences the frequency and/or the output voltage of the feeding converter.

27. An apparatus according to any one of claims 1 to 26, which includes a d.c. motor, the feeding converter being arranged to generate a speed -proportional voltage.

28. An apparatus according to claim 27, in which the speed- proportional voltage is additionally controlled by an actual speed value sensor.

1 '.

24

29. An apparatus according to any one of claims 1 to 28, which comprises a driven drafting arrangement for receiving slivers from the feed rollers.

30. An apparatus according to claim 29, in which the arrangement is such that a desired speed value is formed proportional to the speed of an entry roller of the drafting arrangement.

31. An apparatus according to any one of claims 1 to 30, in which drive motors having the same speed characteristic are used for driving the feed rollers.

32. An apparatus according to any one of claims 1 to 31, in which the arrangement is such that the speeds of the drive motors for the feed rollers are the same or substantially the same.

33. An apparatus according to any one of claims 1 to 32, in which the arrangement is such that, at the same or substantially the same speed of the drive motors for the feed rollers, different circumferential speeds of the feed rollers are achieved in the working direction.

34. An apparatus for feeding slivers to spinning machines, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds A are provided, wherein the drive motors are uncontrolled asynchronous motors, are fed by a common converter and the speeds are jointly adjustable.

35. An apparatus for feeding slivers to spinning machines, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted on a feed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds are provided, and wherein the drive motors are uncontrolled d.c. motors, are fed by a common converter and the speeds are jointly adjustable.

36. An apparatus according to claim 34 or claim 35, which is further in accordance with any one of claims 1 to 33.

37. An apparatus for feeding slivers to a spinning machine, especially a draw frame, for example, an autoleveller draw frame, in which the slivers are drawn out of spinning cans over a plurality of driven feed rollers mounted at a f eed table and are conveyed to a driven drafting arrangement, wherein at least two electric drive motors having adjustable speeds are provided, and wherein the drive motors are fed by a common converter and the speeds are jointly adjustable such the drive motors have negligible or no variations from a desired speed.

0 0,

38. An apparatus for feeding slivers to a spinning machine, the apparatus being substantially as described herein with reference to and as illustrated by any one of Figs. 1 to 6, 7a and 7b.

39. A draw frame comprising an apparatus according to any one of claims 1 to 38.

40. An autoleveller draw frame comprising an apparatus according to any one of the claims 1 to 38.

41. A method for controlling a feed arrangement for a spinning machine, in which a plurality of slivers are drawn out of respective sliver cans over respective feed rollers, and the speeds of at least two drive motors f ed by a common converter are jointly adjusted so as to be substantially the same as a desired speed.