Title of Invention	A METHOD AND DEVICE FOR PREVENTING MASS FLUCTUATIONS IN FIBRE MATERIAL
Abstract	The invention relates to a method and a device for preventing mass fluctuations in fibre material (1 which is processed in a spinning process using a rotor (10)to form a yarn (3) To this end, the mass fluctuations in the fibre material are detected in the immediate vicinity of the rotor and elements (6, 1, 12) which are drive-connected therewith, and are reduced by a control intervention.

Full Text

The invention relates to a method and a device for preventing mass fluctuations in fibre material which is processed in a spinning process using a rotor to form a yarn. In known rotor spinning machines, Whioh UiUally comprise a large number of spinning stations ■■ so-allied spinning boxes -, a common drive is provided for all important elements of the spinning box. This maana that the feed roller, the separating roller, th« rotor, the take-up roller and the splined cylinder in particular comprise a common drive having fixed relative rotational spaads. Consequently, the various rotational speeds can only be changed as a whole, for example in order to influence the quantity of yarn produced. As a result of influences of i this type, all spinning stations are usually monitored as a whole. A disadvantage of rotor spinning tnachinee of this type consists in that irregularities in the rttass of the supplied fibre strip can lead to irregularities in the spun yarn at the spinning station outlet. This can be prevented by ensuring that the supplied fibre strip is a regular as possible, i.e. exhibits no mass fluctuations over its length and cross section. However, this can only be achieved if influencing of this type is actually possible from an organisational point of view. If strips of, this type are bought for processing to form yarn, then this possibility does not exist. It is therefore the object of th» invehtioft to provide a method and a device for preventing maa® fluctuations in yarn, by means of which the irregtilarities in mass, which are present in the fibre material, can be reduced so that a yarn is produced from rotor spinning which is as uniform as possible. fhlm ob:3ect is atuained in that th« ma«» fluctuations in the £tbr« material are detected in th© immtdlate vicinity of the rotor siia §igm§iit§ which art driva-conmattd timrmith and are reduced by a control intervention. A control intervention of this type is used to control the supply of the said fibre material at the outlet point or its withdrawal at the outlet of the spinning process as a function of measured mass fluctuations, the fibre material firstly appearing as a fibre strip and then as yarn. In this respect, the rotor is driven at a relatively constant operating velocity. Control int«rvenfcions of this type are • achieved with the aid of a control circuit or a control process which directly influence the aohvarsion of unspun fibres to yarn or the elements which participate in this process. This can occur in that the relationship between the circumferential velocities of those elements drawing off fibres or yarn and those elements supplying fibre strip or fibres is changed in such a manner that no fibre accumulations build up and thin areas in the supplied fibre material are filled out. This is carried out in each case as a function of a measurement value. A measurement value which detects thick or thin areas of this type can be transmitted, for example, by a atrip measuring element which is arranged upstream of the feed roller, or by a yarn sensor arranged downstream of the rotor. In the first case, this results in an open control circuit, and in the second case a closed control circuit in cases wher® the control intervention is effected at the feed roller, for example. However, combined control methodfl with open and closed control circuits are also possible. A control means of this type preferably operates with digitiied signals and is ' divided into control modules and a oshtral unit, a control module being associated with tSob apihhing station and a central unit being associated With a plurality offspinning stations. In this case, the central unit manages, distributes and at the start transmits adjustment data or values, for example, which are compulsory for all spinning stations. The individual control modules operate exclusively for the associated spinning station and in response to control signals from the central unit. Asa result of the device according to the invention or the method according to the invention it is possible to compensate irregularities practically immediately before or during the conversion from fibre strip to yarn. Consequently, it can be assumed that fewer cleaning interventions need to be carried out in respect of the yam and that yarn with an improved and more uniform quality is obtained. On the other hand, it is also possible to process relatively poor, because irregular, fibre strip directly into good, regular yam. If it is intended to use this method and device especially for producing high-quality yam, to which end the fibre strip can firstly be evened out, for example by controlled stretching, and residual flaws in the yam can then be improved by cleaning to within narrow tolerances, then it is possible to carry out the individual interventions into the material flux - in the fibre strip, during spinning and during cleaning - with greater care or to specialise in particular flaw types or effects. A further advantage consists in that each spinning station of a spinning machine can now manufacture a separate yam number, since a different control signal containing the values which are to be observed can be made available to each spinning station using the control system according to the invention. Accordingly, the present invention provides a method for preventing mass fluctuations in fibre material which is processed in a spinning process using a rotor to form a yam, characterised in that the mass fluctuations in the fibre material are detected in the immediate vicinity of the rotor and elements which are drive-connected therewith, and are reduced by a control intervention. Accordingly, the present invention also provides a device for carrying out the method as herein above described, characterised in that the drive of an element, which is provided for conveying the fibre material in the area of a separating roller and the rotor, is connected to a control device and is controlled thereby. The invention is e7q}lained in further detail in the following with the aid of an example and with reference to the accompnying drawings, in which: Figure 1 is a schematic illustration of a spinning process with the elements involved therein and a control device, and Figures 2 to 8 each show a further embodiment of the control device. Figure 1 shows a fibre material flow, which is firstly-supplied as a fibre strip 1 to a apimiliig station 2, leaves the station as yam 3 and is wound onto a yarn bobbin 4. In between, the fibre strip 1 is supplied via a strip compressor 5 and a feed roller 6 to a separating roller 7, where the fibres of the fibres strip 1 are separated and received by the separating roller 7 with the aid of a feed trough 8. A fibre suction element 9 draws the fibres from the separating roller 7 again and Conveys them into a rotor 10, on whose wall a yarn forms, which is drawn off via a yam funnel 11, removed by a tak«-up roller 12 and supplied to the yam bobbin 4. The taka-u^ ro^liBr 12, the rotor 10 and the separating roller 7 are drivel via a drive line 13 and are rigidly connected to one anothei' for the drive. The feed roller 6, the separating roller 7 and the take-up roller 12 are elements which can bQ drive-connected to the rotor and are arranged in the vicinity thereof, since they cooperate directly with the rotor 10. All these elements form a drive for the fibre material. The elements described so far are known per se and are found in the spinning station or spinning box of a rotor spinning machine. In the first embodiment of the device according to the invention illustrated in Fig. 1, the feed roller 6 is connected via a drive line 14 to a control device 15. The control device 15 is also connected via lines 16, 17 to the strip compressor 5, which is conatrticttd in this case as a strip measuring element or is provided with a strip measuring element, and to a pulse transmitter 18, which can derive pulses from the drive line 13 which are proportional to the speed thereof. A further lin« 19 is used for the supply and a bus 20 is used as n cotifi|,eqtion with a central unit 21. I In this case, the control device 15 coifiprises a servomotor or control motor 22 and a gearing 23 for the drive line 14, as well as a computer or processor 24, an amplifier 25 and an evaluation unit 26 for processing signals for the control moEor 22. The processor 24 is designed for transforming a physical value into an electrical wignal. In conventional ° fashion, the processor 24 comprisai analogue/digital and digital/analogue converters, whicH are coiinected to inputs or outputs, and a microprocessor with a memory. ? The method of operation of the device siccording to Fig. 1 is as follows: In the strip measuring elertie|it in the strip compressor 5 the mass fluctuations in the fibre material 1 are detected and converted into an electrical signal, which is supplied via the line 16 to the evaluation unit 26. Here, the current measurement value is compared with threshold values, for example, which daterttiine a tolerance range for those measurement values which do not trigger a control process. Evaluated signals, preferably analogue signals, are supplied to the computer 24, where they are digitised, linearised, monitored according to predetermined standpoints, delayed and amplified. The computer 24 also has at its disposal a signal from the pulse transmitter 18, which indicates the current operating velocity of the other elements. On the basis of the input signal, i.e. the velocity and the momentary mass of the fibre strip, the computer 24 determines an output signal which it transmits to the amplifier 25, the signal representing a correction value or a control value which indicatea the new circumferential velocity of the feed roller 6. This correction value controls the rotational velocity of the control motor 22 and, via the gearing 23, also the rotational velocity of the feed roller 6. The control circuit illustrated in this case is therefore an open control circuit which is designed to produce uniform fibre loading of the separating roller 7. In this manner it can be assumed that a very loniform fibre flow reaches the rotor 10 via the fibre suction element 9. Figure 2 shows a device which comprises asaantially the same • elements as the device in Fig. 1, but in which the line 16 is connected to a tracer element 36, whiah replaces or supplements the feed trough 8. The traosr element 36 is spring-loaded and presses the fibre atrip 1 onto the feed roller 6. The fibre strip 1 deflects the tracer element 3 5 in proportion to the mass of fibre material 1 and this deflection is converted into an electrical signal. The signal processing is effected in now known manner in the control device 15. In the embodiment of the invention according to Figure 3, a differential or planetary gearing 27 ia provided as a gearing. This is connected via a dtive line 28 to^the drive line 13, so that the servomotor 22 iB only required to effect a rotational speed change in th€ drive line 14 for the feed roller 6. The mean rotational sp«®d, from which this rotational speed change is derived, i» supplied to the differential gearing 27 ,via the drive Una 28. Consequently, there is no need for a pulaa transmitter 18 as known from Fig. 1. In the embodiment according to Figure 4/ a yarn measuring element 29 is additionally arranged downstream of the rotor 10, at the outlet of the spinning statio|i 2. The yarn measuring element 29 can be arranged upstream (as illustrated in this case) or downstream o£ the take-up roller 12. The yarn measuring element 29 is a known element, which can scan the yarn optically or capacitively, for example. The yarn measuring element 29 is connected via a line 30 to an evaluation unit 32 in the control device 31. The evaluation unit 32 has the same function as the evaluation unit 26 in the control device 15 (Fig. 1). This design provides control behaviour as is known for combined open and closed control circuits, for example for stretching machines, from EP 0176661. The closed control circuit is formed in this case by the yarn measuring element 29, the line 30, the control device 31 and the drive line 14. The open control circuit is already known ttgm Figures 1 to 3. However, this embodiment can also operate in such a manner that the yam measuring element 29 is used for monitoring and therefore only monitors the quality of the control process in the open control circuit fitted between the strip compressor 5 and the feed roller 6. If the computer 24 determines that the quality of tha yarn is poor by comparing predetermined yarn flaw tolerances stored therein with the signal from the strip measuring element ;3i, then it can cause the spinning station to close dowi ot can cause a fault report or alarm signal to be transmitted. This can happen, for example, if the control circuit drifts, the measuring element is subjected to unusual Vibrations or if other disturbances occur. A further embodiment is known from Figure 5 in which the yam funnel 11 at the output of the rotor 10 comprises a , device for measuring the mass of the fibre material running through, the device transmitting a signal to the line 33. However, .a measurement of this type can only take place downstream of the take-up roller 12. The processing of the signals in the control device 31 is affected in known manner. 1 Figulres 5 and 7 each show only a oloaed control circuit 37, 38 respectively, which extends in thm embodiment according to Fig. 6 over the yarn funnel 11 and in the embodiment according to Fig. 7 over the independent: yarn measuring element 29. Figure 8 shows an embodiment in which the take-up -^elocity of the take-up roller 12 is influenced by a control intervention. To this end, the take-Up roller 12 is connected via a drive line 34 to the glaring 23. As soon as the yarn measuring element 29 detects a thin area, the take- up velocity is reduced. In the case of thick area being detected in the yam 3, the velocity is increased. These processes mean that the yam is taken up somewhat earlier or later than average from the rotor 10. Consequently, the site 35 at which the yarn is separated from the wall of the rotor 10 is also displaced. This embodiment is particularly suited in combination with a control circuit as already known, for example, from Fig. 1. Instead of taking place in the yarn measuring element 29, a measurement which forms the basis of the control for the take-up velocity of the yarn can also be carried out at the supply trough 1, as is now known. WE CLAIM; 1. A method for preventing mass fluctuations in fiber material (1) which is processed in a spinning process using a rotor (10) to form a yam (3), characterized in that the mass fluctuations in the fiber material are detected in the immediate vicinity of the rotor and elements (6,7,12) which are drive-connected therewith, and are reduced by a control intervention. 2. The method according to claim 1, wherein the velocity at which the fibre material is supplied at the start of the spinning process is influenced as a control intervention. 3. The method according to claim 1, wherein the velocity at which the fibre material is taken up at the end of the spinning process is influenced as a control intervention, 4. The method according to claim 1, wherein the control intervention is effected as a function of the mass of fiber material. 5. A device for carrying out the method according to claim 1, characterized in that the drive of an element (6, 12), which is provided for conveying the fiber material (1) in the area of a separating roller and the rotor (10), is connected to a control device (IS) and is controlled thereby. 6. The device according to claim 3, wherein a feed roller (6), which is arranged upstream of the separating roller (7), is provided as said element. 7. The device according to claim 5, wherein a take-up roller (12), which is arranged downstream of the rotor, is provided as said element. 8. The device according to claim 5, wherein an open (5,16,31,14,6) and a closed (29, 30,31,14,6) control circuit are provided. 9. The device according to claim 5, wherein an open (5, 16, 31, 14, 6) control circuit is provided with yam monitoring. 10. The device according to claim 5, wherein a closed (29, 30, 31, 14) control circuit is provided. 11. The device according to claim 5, wherein a yam sensor (29) with a computer (24) connected thereto is provided for monitoring the control process. 12. A method for preventing mass fluctuations in fiber material substantially as herein described with reference to the accompanying drawings. 13. A device for preventing mass fluctuations in fiber material substantially as herein described with reference to the accompanying drawings.

Documents:

1083-mas-1996 abstract.jpg

1083-mas-1996 abstract.pdf

1083-mas-1996 assignment.pdf

1083-mas-1996 claims.pdf

1083-mas-1996 correspondence others.pdf

1083-mas-1996 correspondence po.pdf

1083-mas-1996 description (complete).pdf

1083-mas-1996 drawings.pdf

1083-mas-1996 form-2.pdf

1083-mas-1996 form-26.pdf

1083-mas-1996 form-4.pdf

1083-mas-1996 form-6.pdf

1083-mas-1996 petition.pdf