GB2463353A

GB2463353A - Apparatus for correcting a measurement of textile sliver thickness

Info

Publication number: GB2463353A
Application number: GB0915365A
Authority: GB
Inventors: Thomas Schmitz; Johannes Bossmann
Original assignee: Truetzschler GmbH and Co KG
Current assignee: Truetzschler GmbH and Co KG
Priority date: 2008-09-12
Filing date: 2009-09-04
Publication date: 2010-03-17
Anticipated expiration: 2029-09-04
Also published as: CN101671873B; JP5529474B2; IT1395159B1; DE102008047156A1; BRPI0903294A2; CH699464A2; GB0915365D0; GB2463353B; CH699464B1; BRPI0903294B1; JP2010065370A; CN101671873A; BRPI0903294B8; ITMI20091463A1

Abstract

An apparatus for or on a spinning room preparation machine for correcting a measurement signal relating to the thickness of at least one textile fibre sliver, which signal is obtained from a pair of sensing rolls 7, 8, one of the sensing rolls 7 is arranged in fixed position and the other sensing roll 8 is force-loaded and arranged to be movable away from the fixed sensing roll. A periodic error value caused by non-circularity and/or eccentricity of the pair of sensing rolls 7, 8 is detectable, the pair of sensing rolls being connected to a displacement sensor 64 and a rotational angle transmitter which send their signals to a signal processing means and the output of the processing means delivers the corrected measurement signal. In order that the concentricity error can be detected and corrected simply and quickly, it is possible to establish touching contact between the circumferential surface of the fixed sensing roll 7 and the sensing roll 8 that is movable and the sensing rolls 7, 8 are rotatable while in touching contact.

Description

Apparatus for or at a spinning room preparation machine, especially a carding machine, draw frame, combing machine or flyer, for correcting a measurement signal The invention relates to an apparatus for or at a spinning room preparation machine, especially a carding machine, draw frame, combing machine or flyer, for correcting a measurement signal relating to the thickness of at least one textile fibre sliver, which signal is obtained from a pair of sensing rolls.

The measurement of fibre sliver thicknesses, espe-cially for the purposes of levelling out irregularities in one or more fibre sliver(s) introduced into a spinning room preparation machine, is customary in practice. Such measurement is also desirable at the exit from the machine for quality control of the drafted material. In addition to the said quality control, measured values relating to the density or thickness of the fibre sliver are also used for shutting down the machines if pre-specified mass variation values are exceeded and therefore a high-quality product is no longer being obtained.

In a known apparatus (DE 44 14 972 Al), the thickness of a fibre bundle, for example consisting of at least one fibre sliver or a fibre web, is measured using a pair of sensing rolls. The pair of sensing rolls is so configured that one rotatable sensing roll is stationarily arranged and the other rotatable sensing roll is arranged so as to be pivotable relative thereto. The two sensing rolls are biased by a spring. The pivotable sensing roll is deflected according to the thickness of the fibre sliver guided between a pair of sensing rolls. The angle of the deflection is converted into an electrical signal, the measurement signal. Such a pair of sensing rolls is used, for example, upstream of a drafting mechanism. The pair of sensing rolls advantageously is of mechanically simple construction and is robust and accordingly economical.

During operation of a pair of sensing rolls it can happen that the measurement signal is falsified. In the case of a pair of sensing rolls in the form of a mechanically operating sensor it is known that the measurement signal is influenced as a result of tolerances in the case of the sensing rolls and tolerances of the sensing roll bearings.

Departures from the ideal geometry of a sensing roll body can manifest themselves in changes in cross-section over the length of the cylindrical roll body. Likewise, departures from central bearing of the sensing rolls can result in eccentricity. The tolerances in the geometric dimensions of the sensing rolls are superimposed on the tolerances from the bearings of the sensing rolls. Those tolerances result in an error in the measurement signal which is not to be underestimated. It is a periodic error which is operative with each revolution of a sensing roll.

For correction of the erroneous measurement signal of the pair of sensing rolls it is proposed that the appearance of a periodic error value in the measurement signal of the fibre sliver caused by non-circularity and/or eccentricity of the pair of sensing rolls be detected and stored as an error value, position-related in respect of a revolution of the sensing rolls, and that during operation of the sensing rolls the stored error value be used within the revolution cycles for correction of the current measurement signals at the same position. The registering of the concentricity error is therefore carried out in the measurement signal, that is to say it is detected with fibre material in the roll nip. It is assumed that, in the event of a sufficiently large number of measurements, on the basis of normal distribution the sliver error adds up to zero and only the concentricity error of the roll is left over. For the case where the measured values do not follow normal distribution, in this process an error remains. An additional problem is that the amount of apparatus required is large. In particular, the electronics system is equipped with assemblies for forming an average value from a large number of revolutions, there being formed the set of values of the measurement signals averaged over a large number of revolution cycles.

Furthermore, the elasticity and irregularity inherent in the fibre material passing through the roll nip results in undesirable variations which in each case are in addition to the non-circularity of the sensing rolls. The concentricity error is detected indirectly. Finally, for measurement of the concentricity error a large number of roll revolutions is necessary, which is time-consuming.

It is an aim of the invention to provide an apparatus of the kind described at the beginning which avoids or mitigates the mentioned disadvantages and which, in particular, enables the concentricity error to be detected and corrected in a simple way and within a short space of time.

The invention provides an apparatus for or at a spinning room preparation machine for correcting a measurement signal relating to the thickness of at least one textile fibre sliver, which signal is obtained from a pair of sensing rolls, wherein one of the two sensing rolls is arranged in fixed position and the other sensing roll is force-loaded and arranged so as to be movable away from the fixed sensing roll, the apparatus further comprising: a displacement sensor; a rotational angle transmitter; and an electrical signal-forming means; wherein touching contact between the circumferential surface of the fixed sensing roll and the movable sensing roll can be established and the sensing rolls are rotatable while in touching contact, the appearance of a periodic error value caused by non-circularity and/or eccentricity of the pair of sensing rolls during rotation being detectable by means of said displacement sensor and the electrical signal forming means forming a signal that is correctable in dependence upon the information received from the displacement sensor and the rotational angle transmitter.

Because the concentricity error is detected directly, that is to say without fibre material, with the rolls touching one another, it is possible to effect correction in a simple way and within a short space of time. Advant-ageously, the contours of the circumferential surface of the two rolls are scanned directly by touching contact. As a result of the measures taken according to the invention, the concentricity error can be completely or almost completely eliminated in an elegant way. The concentricity error is detected directly in the machine and calculated out of the measurement signal by the control means.

Advantageously, it is possible to form position-related measurement signals of the deflection of the path of the movable sensing roll in the event of changes in the spacing between the centre points of the sensing rolls.

Advantageously, it is possible to form the position-related measurement signals for at least one revolution of the sensing rolls. Advantageously, it is possible to form the position-related measurement signals of the deflection of the path in the event of a change in the contour of the circumferential surface of at least one sensing roll.

Advantageously, to determine the deflection caused by the non-circularity of the sensing rolls there is used a standard roll that does not depart from a desired value.

Advantageously, one of the two sensing rolls is mounted so as to be rotatable or pivotable. Advantageously, the movable sensing roll is arranged to be pressed against the fixed sensing roll by means of a force means.

Advantageously, the movable sensing roll or the holding element for the movable sensing roll is associated with an electrical signal-forming device. Advantageously, the fixed sensing roll or the holding element for the fixed sensing roll is associated with an electrical signal-forming device. Advantageously, the at least one revolution of the sensing rolls for determination of the periodic error value is arranged to be carried out manually. Advantageously, the at least one revolution of the sensing roll for determination of the periodic error value is arranged to carried out using a motor.

Advantageously, in the event of non-circularity of at least one sensing roll it is possible to generate a periodic error value in the measurement signal of the deflection of the path of the movable sensing roll when in touching contact with the fixed sensing roll.

Advantageously, the deflection of the path of the movable sensing roll caused by non-circularity of at least one sensing roll can be converted into an electrical measurement signal by an electrical signal-forming means.

Advantageously, a signal-processing means responds to the electrical measurement signal of the deflection of the path of the movable sensing roll when in touching contact with the fixed sensing roll. Advantageously, by means of the electronic signal-processing means the periodic error value contained in the electrical measurement signal can be detected. Advantageously, the periodic error value, position-related in respect of one revolution of the sensing rolls, can be stored in a memory of an electrical control and regulation device. Advantageously, the stored error value can be used during operation of the sensing rolls in a correction element of the electronic control and regulation device for correction of the current measurement signal, at the same position, of the variations in the density of the fibre material.

Advantageously, the electrical signal-forming means is able to deliver the electrical measurement signal of the deflection of the path of the movable sensing roll when in touching contact with the fixed sensing roll to an A/D converter. Preferably, the A/D converter is connected to the electrical control and regulation device.

Advantageously, the rotational angle transmitter is coupled to the movable sensing roll. Advantageously, the rotational angle transmitter is connected to the electrical control and regulation device. Advantageously, the rotational angle transmitter is integrated in the control and regulation device.

Advantageously, the sensing rolls are in compulsory operative connection with one another, for example by means of a toothed belt coupling or the like.

Advantageously, the sensing rolls can briefly be moved into direct contact with one another for the purpose of detecting non-circularity. Advantageously, the sensing rolls can be rotated slowly during detection of non-circularity. Said slow rotation is at a speed slower than the speed of rotation during operation of the machine.

Advantageously, the stop element (spacer) can be moved away for bringing the sensing rolls into contact with one another. For example, for moving away of the stop there can be used a pneumatic cylinder, actuating drive, magnetic switch or the like. Advantageously, the stop is spring-loaded. Advantageously, the force exerted by the sensing rolls is reduced to a minimum amount during the touching contact. Advantageously, the force-applying element is able to exert a very low force during detection of non-circularity (touching contact) and a high force during operation (contact in the fibre material) Advantageously, during the concentricity error measurement the force of the pneumatic cylinder can be increased in order to overcome the force of the spring-loaded stop. In certain embodiments, the pair of sensing rolls comprises a groove roll and a tongue roll. In certain other embodiments, the pair of sensing rolls comprises two stepped rolls. Advantageously, the stop, after the concentricity error measurement, is capable of generating a normal spacing between the circumferential surfaces of the sensing rolls (roll nip). Advantageously, a non-contact-making spacing sensor is provided for measuring the spacing from a counter-surface (scanning surface) associated with the holding element for one sensing roll.

Advantageously, the spacing sensor is associated with the holding element for the other sensing roll.

Advantageously, the spacing sensor and the counter-surface are arranged on the sides of the holding elements that face one another. Advantageously, the spacing sensor is integrated in the holding element for a sensing roll.

Advantageously, the counter-surface is associated with the holding element for one sensing roll, the spacing sensor is associated with the holding element for the other sensing roll, and the spacing sensor and the counter-surface are arranged on the sides of the holding elements that face one another. In one embodiment, the spacing sensor is in fixed position and the counter-surface is displaceable relative to the spacing sensor. In another embodiment, the spacing sensor is displaceable and the counter-surface is in fixed position relative to the spacing sensor.

In certain embodiments, the spacing sensor is capable of detecting a change in induction. For example, the spacing sensor may be an inductive proximity initiator.

In further embodiments, an optical spacing sensor (distance-measuring sensor) may be used. In yet further embodiments, the spacing sensor is an analog sensor.

Advantageously, the spinning room preparation machine is an autoleveller carding machine, a carding machine having an autoleveller drawing mechanism, a combing machine having an autoleveller drawing mechanism, or a draw frame.

Advantageously, detection of the sliver mass of a moving fibre bundle is provided at a spinning room preparation machine having a plurality of successive drawing elements for drafting the fibre sliver. Advantageously, the spacing sensor is arranged at the intake and/or outlet of a drafting mechanism of the spinning room preparation machine. In certain embodiments, the axes of the sensing rolls are arranged horizontally. In certain other embodiments, the axes of the sensing rolls are arranged vertically. Preferably, the axes of the sensing rolls are arranged parallel to one another. Advantageously, the bias of the movably mounted holding element for the spacing sensor is effected by and is adjustable by mechanical, electrical, hydraulic or pneumatic means, for example by means of springs, weights, inherent resilience, loading cylinders, magnets or the like.

The invention also provides a spinning room preparation machine, especially a carding machine, draw frame or combing machine, especially for use of the apparatus according the invention, having at least one spacing sensor for measuring non-circularity of a pair of sensing rolls. Preferably, at least one sensing roll is driven. In certain embodiments, the two sensing rolls, acting simultaneously as draw-off rolls, are arranged directly downstream of the funnel-shaped sliver guide means, web guide means or the like. Preferably, the spacing sensor detects the spacings from a counter-element located opposite the sensor surface. Advantageously, the circumferential surfaces that are directly in touching contact with one another during the concentricity error detection are in touching contact with the fibre material during operation. Preferably, more than one revolution of the sensing rolls is provided for concentricity error detection and a device for forming an average value is provided in the electronics system.

The invention also provides an apparatus for or at a spinning room preparation machine, especially a carding machine, draw frame, combing machine or flyer, for correcting a measurement signal relating to the thickness of at least one textile fibre sliver, which signal is obtained from a pair of sensing rolls, wherein one of the two sensing rolls is arranged in fixed position and the other sensing roll is force-loaded and arranged so as to be movable away from the fixed sensing roll, and the appearance of a periodic error value caused by non-circularity and/or eccentricity of the pair of sensing rolls is detectable, the pair of sensing rolls being connected to an electrical signal-forming means (displacement sensor) and a rotational angle transmitter which send their signals to the input of an electronics system, and the output of the electronics system delivering the corrected measurement signal, in which touching contact between the circumferential surface of the fixed sensing roll and the movable sensing roll can be established by exertion of force on the fixed sensing roll by the movable sensing roll and the sensing rolls are rotatable while in touching contact.

Certain illustrative embodiments of the invention are described in greater detail below with reference to the -10 -accompanying drawings, in which: Fig. 1 is a diagrammatic side view of an autoleveller draw frame with an apparatus according to the invention; Fig. 2 is a diagrammatic side view of a carding machine drawing mechanism with an apparatus according to the invention; Figs. 3a, 3b are side views of an embodiment according to the invention with a fixed sensing roll and a pivotable sensing roll in the production position (Fig. 3a) and during concentricity error measurement (Fig. 3b) Fig. 3c is a view from below of the fixed sensing roll and pivotable sensing roll of Fig. 3a; Fig. 4 is a partial side view of a pivotable sensing roller with an adjustable stop operable by means of a pneumatic cylinder; Fig. 5 is a partial side view of a pivotable sensing roller with an adjustable stop operable by means of an actuating drive; Fig. 6 is a side view of a further embodiment in which loading of the movable draw-off roll is effected by means of a pneumatic cylinder and a spring-loaded stop; Fig. 7 shows another embodiment having a bearing housing, which is movable in -11 -rotation, for the movable sensing roll with an associated push crank; Fig. 7a is a detail of the apparatus according to Fig. 7 with an adjustable stop, the position of the stop having been displaced to the rear so that the sensing rolls are in touching contact with one another in accordance with Fig. 8; Fig. 8 is a perspective view of the co-operating pair of sensing rolls consisting of a fixed sensing roll and a movable sensing roll in direct contact and their respective fixed and movable bearings; and Fig. 9 i s an illustrative block circuit diagram of a device for correcting the non-circularity of the sensing rolls.

With reference to Figure 1, a draw frame 1, for example a ID 03 draw frame made by Trdtzschler GmbH & Co. KG of Manchengladbach, Germany, has a drawing mechanism 2, upstream of which is an intake 3 of the drawing mechanism and downstream of which is an exit 4 from the drawing mechanism. The fibre slivers 5, coming from cans (not shown), enter the sliver guide 6 and, drawn by the draw-off rolls 7, 8, are transported past the measuring element (spacing sensor 9) . The drawing mechanism 2 is designed as a 4-over-3 drawing mechanism, that is to say it consists of three lower rolls I, II, III (I delivery lower roll, II middle lower roll, III intake lower roll) and four upper rolls 11, 12, 13, 14. Drafting of the fibre sliver combination 5' from a plurality of fibre slivers 5 is carried out in the drawing mechanism 2. Drafting is -12 -composed of preliminary drafting and main drafting. The roll pairs 14/111 and 13/11 form the preliminary draft zone and the roll pairs 13/11 and 11, 12/I form the main draft zone. The fibre sliver combination 5' is drawn out in the preliminary draft zone and the fibre sliver combination 5' is drawn out in the main draft zone. The drawn-out fibre slivers 5' reach a web guide 10 in the exit 4 from the drawing mechanism and, by means of the draw-off rolls 15, 16, are drawn through a sliver funnel 17, in which they are combined to form one fibre sliver 18, which is then deposited in cans. Reference letter A denotes the work direction.

The draw-off rolls 7, 8, the intake lower roll III and the middle lower roll II, which are connected to one another mechanically, for example by toothed belts, are driven by the control motor 19, it being possible, in the process, for a desired value to be specified. (The associated upper rolls 14 and 13, respectively, revolve by virtue of the motion of the lower rolls.) The delivery lower roll I and the draw-off rolls 15, 16 are driven by the main motor 20. The control motor 19 and the main motor 20 each have their own controller 21 and 22, respectively. Control (speed-of-rotation control) is carried out in each case by means of a closed control loop, a tachogenerator 23 being associated with the control motor 19 and a tachogenerator 24 being associated with the main motor 20. At the intake 3 of the drawing mechanism, a variable proportional to the mass of the fibre slivers 5 fed in, for example their cross-section, is measured by an intake measuring element. At the exit 4 from the drawing mechanism, the cross-section (thickness) of the delivered fibre sliver 18 is ascertained by an exit measuring element (spacing sensor 25) associated with the draw-off rolls 15, 16. A central computer unit 26 (control -13 -and regulation device), for example a microcomputer with a microprocessor, sends a setting for the desired value for the control motor 19 to the controller 21. The measurement values of the two measuring elements 9 and 25 are sent to the central computer unit 26 during the drawing process.

The desired value for the control motor 19 is determined in the central computer unit 26 from the measurement values of the intake measuring element 9 and from the desired value for the cross-section of the delivered fibre sliver 18. The measurement values of the exit measuring element 25 are used for monitoring the delivered fibre sliver 18 (delivered sliver monitoring) and for on-line determination of optimum preliminary drafting. By means of this control system, it is possible for variations in the cross-section of the fibre slivers 5 fed in to be compensated, and for the fibre sliver to be made more uniform, by appropriately regulating the drafting process.

Reference numeral 27 denotes a display monitor, 28 an interface, 29 an input device and 30 a pressure bar. The measurement values from the measuring element 25, for example variations in the thickness of the fibre sliver 18, are sent to a memory 31 in the computer 26.

In each case, the draw-off rolls 7, 8 at the intake of the draw frame and the draw-off rolls 15, 16 at the exit have a double function; they serve for drawing off the respective fibre sliver combination Sly and 18 and, at the same time, sense the respective fibre sliver combination 51V and 18. The cross-section or the mass of the fibre sliver 18 passing through the roll nip a between the draw-off rolls 15, 16 during operation can be detected using, for example, an apparatus as shown in Figures 3a to 3c.

Equally, it is possible to use the apparatus shown in Figures 3a to 3c for detecting the cross-section or the mass of the fibre sliver combination 5' (consisting of a -14 -plurality of fibre slivers) passing through the roll nip a between the delivery rolls 7, 8.

The draw-off rolls 7, 8 and/or the draw-off rolls 15, 16 may be configured for detecting a concentricity error in the manner according to the invention.

Fig. 2 shows an arrangement in which, between a carding machine, for example a TC 07 carding machine made by Trdtzschler GmbH & Co. KG, and the coiling plate 35, a carding machine drawing mechanism 36 is arranged above the coiling plate 35. The carding machine drawing mechanism 36 is designed as a 3-over-3 drawing mechanism, that is to say it consists of three lower rolls I, II, III and three upper rolls 37, 38, 39. At the intake of the drawing mechanism 36 there is arranged an intake funnel 40 and at the exit from the drawing mechanism there is arranged an exit funnel 41. Downstream of the exit funnel 41 are two draw-off rolls 42, 43, which rotate in the direction of the curved arrows and draw off the drawn-out fibre sliver 44 from the exit funnel 41. The delivery lower roll I, the draw-off rolls 42, 43 and the coiling plate 35 are driven by a main motor 45, and the intake and middle lower rolls, respectively III and II, are driven by a control motor 46.

The motors 45 and 46 are connected to an electronic control and regulation device (not shown) . The cross-section and/or mass of the fibre sliver 44 passing through the roll nip between the draw-off rolls 42, 43 is/are determined using the spacing sensor 47 -in accordance with the apparatus shown in Figures 3a, 3b. The spacing sensor 47 is connected to the electronic control and regulation device (not shown), which can correspond to the central computer unit 26 (see Fig. 1) . Reference letter B denotes the work direction. The draw-off rolls 42, 43 are configured for detecting the concentricity error in the manner according to the invention.

-15 -Figures 1 and 2 show an embodiment in which the fixed sensing roll 7, 15, 42 (or the bearing housing 52 for the fixed sensing roll 15 according to Figures 7 and 8) is associated with an electrical signal-forming device 9, 25, 47, respectively, in the form of a spacing sensor 57 in Fig. 7 and 8.

In the embodiment of Figures 3a, 3b, there are a fixed sensing roll 7 and a pivotable sensing roll 8, which according to Fig. 3c are in the form of tongue (sensing roll 7) and groove (sensing roll 8) rolls. Between the circumferential surface 8' in the base of the groove of the sensing roll 8 and the circumferential surface 7' on the periphery of the sensing roll 7 there is a spacing a through which the fibre material passes during operation.

There is a pivotable holding element 60 in the form of a single-armed lever 60 which is mounted by one end so as to be rotatable or pivotable on a fixed pivot bearing 61 in the direction of arrows L, M. The journal 8a of the sensing roll 8 is mounted on the lever arm 60. A compression spring 62 is supported by one end on the portion 60a of the lever arm 60, the other end of which is supported against a fixed bearing 63. The other portion 60b of the lever arm 60 is associated with, as displacement sensor, an inductive displacement transducer 64 which is electrically connected to an electronics system (see Fig. 9). On the side of the lever arm 60a facing the fixed sensing roll 7 there is a stop element 65 (see Fig. 3a) which provides for the spacing a between the sensing rolls 7 and 8 during operation.

For registering a concentricity error of the sensing roll 7 and/or the sensing roll 8, the stop element 65 according to Figure 3b is moved away (in a manner not described) so that touching contact between the circum-ferential surface 7' of the fixed sensing roll 7 and the -16 -circumferential surface 8' in the base of the groove of the movable sensing roll 8 is established as a result of the pressure exerted by the compression spring 62. The sensing rolls 7 and 8 are then turned through one complete revolution about their shafts 7a and 8a, respectively, for example manually or using a motor (in a manner not described) . In the event of non-circularity of one or both sensing rolls 7, 8, the movable sensing roll 8 and there-with the lever arm 60 is deflected accordingly in the opposite direction to or in the direction towards the compression spring 62. That deflection of the path, which the plunger anchor 64a also undergoes in the same way, changes the induction in the plunger coil 64b, so that an electrical signal is sent to the electronics system (see Fig. 9) via the lead 66. Data relating to the angular position of the rolls 7, 8 can be provided by a rotational angle transmitter (not shown) In the embodiment of Fig. 4, an adjustable stop 65 is provided by means of a pneumatic cylinder 72. The stop 65 is displaceable in the direction of arrows I, K. In the embodiment of Fig. 5, the stop 65 is adjustable with an actuating drive 72 in the direction of arrows I, K. The actuating drive 72 can be realised, for example, by a motor, a toothed wheel with a toothed rack or the like.

In the embodiment of Fig. 6, the loading of the movable sensing roll 7 is provided by a pneumatic cylinder 74 which is articulated on the lever arm 60a. The lever arm 60b is associated with a stop 65 which is force-loaded by a spring 75 (compression spring) Figures 7, 8 show a device for continuously registering the cross-section and/or mass of a fibre sliver combination (shown in Figures 1 and 2) comprising at least one fibre sliver, with a pair of sensing rolls -17 - 15, 16 (shown in Figures 1 and 2) . The shafts (not shown) belonging to the shaft ends 15a and 16a, respectively, are rotatably mounted in rolling-element bearings 50 and 51, respectively, which are in turn mounted in bearing housings 52 and 53, respectively. The bearing housing 52 is immovable whereas the bearing housing 53 is arranged so as to be movable in rotation (pivotable) about an immovable rotary bearing 54 in the direction of arrows C, D. The rotary bearing 54 is fixed to an immovable support 49. The bearing housing 53 that is movable in rotation is loaded and biased by means of a spring 55, one end of which rests against an abutment 56. By this means, the bearing housing 53 and, together with it, the sensing roll can be moved away on a substantially straight path.

Integrated into the immovable bearing housing 52 is an inductive (non-contact-making) analogue spacing sensor 57, the sensor surface 57a of which is located opposite that surface 53' of the bearing housing 53 which faces it, there being present between the sensor surface 57a and the surface 53' in the operating state a variable spacing a, for example about 1 mm, which is measured by the spacing sensor 57. By this means, one of the rolls -the roll 15 -is immovable and the other roll -the roll 16 -is arranged so as to be movable away therefrom on a substantially straight path. The bearing housing 52 and the support 49 are immovably mounted on the machine frame (not shown) . In the opened state (out of operation, not shown), the spacing b is, for example, about 11 mm.

Reference numeral 70 denotes a push crank for the purpose of opening, reference numeral 58 denotes the lead of the spacing sensor 57 and reference numerals 48a, 48b denote two toothed belt wheels for driving the sensing rolls (by way of a toothed belt which is not shown) . In the opened state (out of operation, not shown), the spacing is, for -18 -example, about 11 mm. Reference numeral 70 denotes a pushing crank for the purpose of opening, reference numeral 58 denotes the lead of the spacing sensor 57 and reference numerals 48a, 48b denote two toothed belt pulleys for driving the sensing rolls 15, 16 (by way of a toothed belt not shown) . The toothed belt coupling results in synchronous running of the sensing rolls 15, 16.

For registering a concentricity error of the sensing rolls 1 and/or sensing roll 16, the stop element 59 according to Fig. 7a is drawn back from the surface 53' of the pivotable bearing housing 53 in direction G by means of an adjusting screw 71, with the result that between the end face 59' of the stop element 59 and the surface 53' there is a spacing b and at the same time, in accordance with Fig. 8, touching contact between the circumferential surface 15' of the fixed sensing roll 15 and the circum-ferential surface 16' of the movable sensing roll 16 is established as a result of the pressure exerted by the compression spring 55. The spacing a (operational state) between the bearing housings 52 and 53 is thereby reduced to the spacing a' (see Fig. 7a) . The sensing rolls 15, 16 are then slowly turned through one complete revolution by means of the toothed belt wheels 48a, 48b with a toothed belt (not shown), for example by means of the main motor 20. The spacing sensor 57 detects the changes in the spacing a' resulting from non-circularity and sends corresponding electrical pulses to the electronics system (Fig. 9) by way of the lead 58.

An apparatus according to the invention having the arrangements shown in any of Figures 1 to 8 can be arranged at the intake and/or at the outlet of a drawing mechanism that is a component of, for example, a carding machine, a draw frame, a combing machine, a flyer or some other spinning room preparation machine.

-19 -The curved arrows, for example 7b, 8b (Fig. 3b), indicate the directions of rotation of the rolls.

Fig. 9 shows a block circuit diagram of an arrangement illustrative of arrangements that may be used for an apparatus of the invention, especially any of those shown in Figs. 1 to 8. There are connected to the control and regulation device 26 (electronics system) the spacing sensor 57 (optionally by way of a digital-analog converter not shown) and a rotational angle transmitter 72. In the control and regulation device 26 (microcomputer having a microprocessor) there is a memory 73 and a correction element 74. The spacing sensor 57 is connected to the memory 73 and the correction element 74, and the rotat-ional angle transmitter 72 is connected to the correction element 74. During operation, the correction element 74 delivers corrected signals to the control motor 19.

Reference numeral 75 indicates a switch-over device which takes care of the switching-over from the teach-in phase (without fibre material) to the operational phase (with fibre material) According to the invention, the concentricity error is detected directly in the machine and calculated out of the measurement signal by the control means 26. For that purpose, the rolls are briefly moved into direct contact with one another and slowly rotated. The measuring system present for sliver measurement determines the departure from concentricity caused by the rolls, shafts and bear�ngs. The data are taken up by the control means 26 and taken into account in the sliver measurement.

The rolls are brought into contact with one another, for example, by moving away of the stop during the concentricity error measurement. After the concentricity error measurement, the stop can be brought into effect again in order to ensure that the normal spacing between -20 -the rolls is as small as possible. The moving away can be effected, for example, by means of a pneumatic cylinder, an actuating drive or a magnetic switch or by means of a spring-loaded stop.

In order that the two rolls touching one another during the concentricity error measurement do not suffer any damage, the calendering pressure can be reduced to a minimum amount during the measurement. That can be effected, for example, by means of a pneumatic cylinder which generates a small force during the concentricity error measurement and otherwise a large force. The force of the pneumatic cylinder could also be increased during the concentricity error measurement in order to overcome the force of the spring-loaded stop.

That concentricity measurement can be effected in regular cycles, so that the change in the concentricity error caused, for example, by roll exchange, wear or soiling, is detected continuously. In that way, exact sliver measurement in the long term can be ensured.

Claims

-21 -Cia iins 1. An apparatus for or at a spinning room preparation machine, for correcting a measurement signal relating to the thickness of at least one textile fibre sliver, which signal is obtained from a pair of sensing rolls, wherein one of the two sensing rolls is arranged in fixed position and the other sensing roll is force-loaded and arranged so as to be movable away from the fixed sensing roll, the apparatus further comprising: a displacement sensor; a rotational angle transmitter; and signal processing means; wherein touching contact between the circumferential surface of the fixed sensing roll and the movable sensing roll can be established and the sensing rolls are rotatable while in touching contact, the appearance of a periodic error value caused by non-circularity and/or eccentricity of the pair of sensing rolls during rotation being detectable by means of said displacement sensor and the signal processing means forming a measurement signal that is correctable in dependence upon the information received from the displacement sensor and the rotational angle transmitter.
2. An apparatus according to claim 1, in which it is possible to form position-related measurement signals of the deflection of the path of the movable sensing roll in the event of changes in the spacing between the centre points of the sensing rolls.
3. An apparatus according to claim 1 or claim 2, in which it is possible to form measurement signals relating to at least one revolution of the sensing rolls.
4. An apparatus according to any one of claims 1 to 3, in which it is possible to form position-related -22 -measurement signals of the deflection of the path in the event of a change in the contour of the circumferential surface of at least one sensing roll.
5. An apparatus according to any one of claims 1 to 4, in which to determine the deflection caused by the non-circularity of the sensing rolls, there is used a standard roll that does not depart from a desired value.
6. An apparatus according to any one of claims 1 to 5, in which one of the two sensing rolls is mounted so as tobe rotatable.
7. An apparatus according to any one of claims 1 to 6, in which the movable sensing roll can be pressed against the fixed sensing roll by a force means.
8. An apparatus according to any one of claims 1 to 7, in which the displacement sensor is associated with the movable sensing roll or the holding element for the movable sensing roll.
9. An apparatus according to any one of claims 1 to 8, in which the displacement sensor is associated with the fixed sensing roll or the holding element for the fixed sensing roll.
10. An apparatus according to any one of claims 1 to 9, in which the at least one revolution of the sensing rolls for determination of the periodic error value can be carried out manually.
11. An apparatus according to any one of claims 1 to 10, in which the at least one revolution of the sensing roll for determination of the periodic error value can be carried out using a motor.
12. An apparatus according to any one of claims 1 to 11, in which in the event of non-circularity of at least one sensing roll it is possible to generate a periodic error value in the measurement signal of the deflection of the -23 -path of the movable sensing roll when in touching contact with the fixed sensing roll.
13. An apparatus according to any one of claims 1 to 12, in which the deflection of the path of the movable sensing roll caused by non-circularity of at least one sensing roll can be converted into an electrical measurement signal by an electrical signal-forming means.
14. An apparatus according to any one of claims 1 to 13, in which the signal-processing means responds to the electrical measurement signal of the deflection of the path of the movable sensing roll when in touching contact with the fixed sensing roll.
15. An apparatus according to any one of claims 1 to 14, in which the electronic signal-processing means is an electronic processor in which a periodic error value contained in the electrical measurement signal can be detected.
16. An apparatus according to any one of claims 1 to 15, in which the periodic error value, position-related in respect of a revolution of the sensing rolls, can be stored in a memory of an electrical control and regulation device.
17. An apparatus according to claim 16, in which the stored error value can be used during operation of the sensing rolls in a correction element of the electronic control and regulation device for correction of the current measurement signal, at the same position, of the variations in the density of the fibre material.
18. An apparatus according to any one of claims 1 to 17, in which the displacement sensor is able to deliver to an A/D converter an electrical measurement signal of the deflection of the path of the movable sensing roll when in touching contact with the fixed sensing roll.

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19. An apparatus according to claim 18, in which the A/D converter is connected to the electrical control and regulation device.
20. An apparatus according to any one of claims 1 to 19, in which the rotational angle transmitter is coupled to the movable sensing roll.
21. An apparatus according to any one of claims 1 to 20, in which the rotational angle transmitter is connected to an electrical control and regulation device to which the measurement signal is supplied.
22. An apparatus according to claim 21, in which the rotational angle transmitter is integrated in the control and regulation device.
23. An apparatus according to any one of claims 1 to 22, in which the sensing rolls are in compulsory operative connection with one another, for example by means of a toothed belt coupling.
24. An apparatus according to any one of claims 1 to 23, in which the sensing rolls can temporarily be moved into direct contact with one another for the purpose of detecting non-circularity.
25. An apparatus according to any one of claims 1 to 24, in which the sensing rolls can be rotated slowly during detection of non-circularity.
26. An apparatus according to any one of claims 1 to 25, in which a stop element that prevents the sensing rolls from contacting one another in operation is removable for bringing the sensing rolls into contact with one another.
27. An apparatus according to claim 26, in which for removal of the stop there can be used a pneumatic cylinder, actuating drive, or magnetic switch.
28. An apparatus according to claim 27, in which the stop is spring-loaded.

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29. An apparatus according to any one of claims 1 to 28, in which the force exerted by the movable sensing roll on the fixed sensing roll is reduced to a minimum amount during the touching contact.
30. An apparatus according to any one of claims 1 to 29, in which said force-loading is effected by a force-loading element that is arranged to exert a lower force during detection of non-circularity and a higher force during operation.
31. An apparatus according to any one of claims 1 to 30, in which during the concentricity error measurement the force applied by the force-loading element can be increased in order to deflect a spring-loaded stop that, in operation, is arranged to prevent the sensing rolls from contacting one another.
32. An apparatus according to any one of claims 1 to 31, in which the pair of sensing rolls comprises a groove roll and a tongue roll.
33. An apparatus according to any one of claims 1 to 31, in which the pair of sensing rolls comprises two stepped rolls.
34. An apparatus according to any one of claims 1 to 33, comprising a stop means that, after the concentricity error measurement, is capable of generating a normal spacing between the circumferential surfaces of the sensing rolls.
35. An apparatus according to any one of claims 1 to 34, in which the displacement sensor comprises a non-contact-making spacing sensor arranged for measuring the spacing from a counter-surface associated with the holding element for one sensing roll.
36. An apparatus according to claim 35, in which the spacing sensor is associated with the holding element for the other sensing roll.

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37. An apparatus according to claim 36, in which the spacing sensor and the counter-surface are arranged on the sides of the holding elements that face one another.
38. An apparatus according to claim 36 or claim 37, in which the spacing sensor is integrated in the holding element for a sensing roll.
39. An apparatus according to any one of claims 35 to 38, in which the counter-surface is associated with the holding element for one sensing roll, the spacing sensor is associated with the holding element for the other sensing roll, and the spacing sensor and the counter-surface are arranged on the sides of the holding elements that face one another.
40. An apparatus according to any one of claims 1 to 39, in which the displacement sensor comprises a spacing sensor in fixed position, a counter-surface being displaceable relative to the spacing sensor.
41. An apparatus according to any one of claims 1 to 40, in which the displacement sensor comprises a spacing sensor that is displaceable and a counter-surface in fixed position relative to the spacing sensor.
42. An apparatus according to any one of claims 1 to 41, in which the displacement sensor is capable of detecting a change in induction.
43. An apparatus according to claim 42, in which the displacement sensor is an inductive proximity initiator.
44. An apparatus according to any one of claims 1 to 41, in which the displacement sensor comprises an optical spacing sensor.
45. An apparatus according to any one of claims 1 to 44, in which the displacement sensor comprises an analog sensor.
46. An apparatus according to any one of claims 1 to 45, in which the spinning room preparation machine is an -27 -autoleveller carding machine, a carding machine having an autoleveller drawing mechanism, a combing machine having an autoleveller drawing mechanism, or a draw frame.
47. An apparatus according to any one of claims 1 to 46, in which the at least one textile sliver comprises a sliver mass of a moving fibre bundle that is detected on a spinning room preparation machine having a plurality of successive drawing elements for drafting the fibre sliver.
48. An apparatus according to any one of claims 1 to 47, in which there is a first said displacement sensor arranged at the intake of a drawing mechanism of the spinning room preparation machine, and/or a second said displacement sensor arranged at the outlet of the drafting mechanism.
49. An apparatus according to any one of claims 1 to 48, in which the axes of the sensing rolls are arranged horizontally.
50. An apparatus according to any one of claims 1 to 48, in which the axes of the sensing rolls are arranged vertically.
51. An apparatus according to any one of claims 1 to 50, in which the axes of the sensing rolls are arranged parallel to one another.
52. An apparatus according to any one of claims 1 to 51, in which the bias of a movably mounted holding element comprising the displacement sensor is effected by and is adjustable by mechanical, electrical, hydraulic or pneumatic means.
53. An apparatus according to any one of claims 1 to 52, in which the circumferential surfaces that are directly in touching contact with one another during the concentricity error detection are in touching contact with the fibre material during operation.
54. An apparatus according to any one of claims 1 to 53, -28 -in which more than one revolution of the sensing rolls is provided for concentricity error detection and a device for forming an average value is provided in the signal processing means.
55. An apparatus for or at a spinning room preparation machine for correcting a measurement signal relating to the thickness of fibre material, the apparatus being substantially as described herein with reference to and as illustrated by any of Figs. 1, 2, 3a to 3c, 4, 5, 6, 7, 7a, 8 and 9.
56. A spinning room preparation machine comprising an apparatus according to any one of the preceding claims.
57. A spinning room preparation machine according to claim 56, in which at least one sensing roll is driven.
58. A spinning room preparation machine according to claim 56 or claim 57, in which the two sensing rolls, acting simultaneously as draw-off rolls, are arranged directly downstream of a funnel-shaped sliver guide means or web guide means.
59. A spinning room preparation machine according to any one of claims 56 to 58, in which the displacement sensor comprises a spacing sensor for detecting the spacing from a counter-element located opposite the sensor surface.
60. A method for correcting errors of circularity and/or concentricity in a pair of sensing rolls of a textile machine between which, in operation, fiber material is conveyed and sensed, comprising bringing the circumferential surfaces of the rolls into contact with one another, rotating the rolls whilst maintaining them in contact with one another, monitoring displacement of the rolls relative to one another and simultaneously monitoring the angular position of the rolls, generating a measurement signal in dependence on the displacement and angular position measurements, and using said measurement -29 -signal for correction of at least one operating setting of the textile machine during operation.
61. A method according to claim 60, in which the rolls are decelerated from their normal operating speed before the rolls are brought into contact and are accelerated to their normal operating speed after said monitoring.