EP0608001B1 - Ring spinning machine with a yarn tension sensor and use of a yarn tension sensor to control a ring spinning machine - Google Patents

Description

The present invention relates to a ring spinning machine a thread tension sensor, as well as the application of a Thread tension sensor for controlling a ring spinning machine.

It is the aspiration in the textile machinery industry that Monitor production on every spindle of a spinning machine to be able to. Has a thread break at a spinning position Loss of production and wage labor and can result in in certain cases also damage to the machine to lead. The main causes of thread breaks are for example, thin spots in the yarn, poorly maintained parts in the yarn formation process or incorrect setting of the Spinning machine.

Known thread monitoring devices register under other parameters such as the ballooning of the thread or the Speed of the rotor in a ring spinning machine, the changes over time in the thread thickness of the running thread or the cross section of the thread. Because of the high Such devices, however, will only incur manufacturing costs few machines used. The DE OS 29 19 836 discloses a thread break sensor which consists of a piezoelectric element that is on one part the thread guide is attached and its output signal to Finding a thread break is processed further.

By touching the thread guide with the spun threads occur at this high-frequency vibrations with mechanical vibrations of the ring spinning machine are mixed are. As can be read in DE-OS 29 19 836, is the frequency of the mechanical vibrations is about 1 kHz, while the thread guide vibrates at around 15 kHz. This the latter vibrations are in DE-OS 29 19 836 Finding broken threads evaluated in such a way that the natural vibrations compared to the mechanical ones Vibrations discriminated. More specifically, the two are Connection lines of the piezoelectric element with a Bandpass filter connected, which is the natural vibration component in the output signals of the piezoelectric element picks up, i.e. lets through. This natural vibration component is then amplified to a specific one Increased value. A rectifier filter converts the AC signals to DC signals. With A voltage comparator becomes a voltage range in which normal operation is guaranteed, and on The output of the comparator has a corresponding logic Output signal on (DE-OS 29 19 836, p. 10, lines 29 to p. 11, e.g. 6).

The thread sensor from DE-OS 29 19 836 is only in the Able to determine thread breaks, but not the Measure thread tension.

From the post-published EP-A-0 368 608 is a ring spinning machine known, at which the ring railway, on which the Runner revolves around the spindle, opposite the fixed one Ring bank can be driven via a ring motor. Due to the driveability the ring track is achieved that the relative speed between the rotating spindle and the rotating ring track adjustable and in particular can be reduced, thereby reducing the relative speed between spindle and rotor in certain operating states can be reduced so that the thread breakage risk Is decreased.

On the one hand, by controlling the ring speed faster starting of the spindles after a gradual Sequence program and secondly an overall higher operating speed of the spindles, because the in increased thread loads occurring in these operating conditions due to the reduced relative speed between Spindle and rotor can be reduced. The respective Thread loading is carried out by a thread tension sensor determined, with one for each yarn material certain, desired thread tension is selected, which should be observed during the entire spinning process.

The measured thread tension deviates from the desired thread tension down, so the speed of the ring track becomes changes that the measured thread tension value adjusted to the desired thread tension value. Exceeds the measured thread tension value has an upper limit or if it falls below a lower limit, the Spindle speed correspondingly reduced or increased until the measured thread tension value again below the upper one or is above the lower limit. To achieve and then maintaining the desired thread tension again only the speed of the ring track controlled.

From DE-A-37 18 924 is an automatic winder with several Known winding units, with which the spun on a spindle wound thread unwound from this spindle and on a package of a predetermined shape and one predetermined thread volume is wound up, in the thread existing defects are eliminated. The the spun Thread-bearing spindle is stationary in a spindle take-up point arranged so that a spindle drive, as a ring spinning machine has, does not exist is. The thread comes from the stationary spindle in the longitudinal direction withdrawn and led straight to the package. So while the thread on a winder too the package is guided without substantial elements to come into contact with the winding machine passes through Thread in a ring spinning machine a complex, constantly changing path, the thread simultaneously with the Guide eye, an anti-balloon ring and the runner underneath Friction is in contact.

The present invention has for its object a to provide improved ring spinning machine.

This object is achieved according to the invention by Features of claim 1 and by the features of claim 8.

The invention is based on the knowledge belonging to the invention that the output signal of the sensor is a complex analog signal which also contains, among other things, the speed of the rotor as a fundamental vibration in the course of the deflection of the thread guide as well as harmonic values of this fundamental vibration and the so-called thread noise. in addition to other vibrations such as the natural vibrations of the thread guides and vibrations induced by machine vibrations. Furthermore, the invention is based on the inventive finding that both the level of the rotor speed and the level of harmonic frequencies of the rotor speed are a function of the thread tension, so that an evaluation of the thread tension either at the fundamental frequency (f ₁ ) or at the harmonic frequencies ( f ₂ to f ₉ ) of the rotor speed is possible.

The evaluation of the sensor signal can therefore go that a comparison of the level of thread tension is carried out with a reference level. This reference level can vary from machine parameters such as Depending on the spindle speed, maintenance condition etc. The result this comparison can then be used to control the corresponding Machine are used, namely for control the spindle speed of a ring spinning machine in the sense of Adherence to a predetermined thread tension or one predetermined course of the thread tension over the Coping process.

It should be noted here that the amplitude the natural vibrations of the thread guide, which in the DE-OS 29 19 836 for obtaining the thread break signal is evaluated, practically independent of the thread tension and is therefore not an evaluation option for the Thread tension offers.

Particularly preferred variants of the invention are the subclaims 2 to 7 or 9 to 11.

In the case of the invention Ring spinning machine is preferably the thread guide as Thread guide eyelet, for example in the form of the known Sauschwanzerls trained. The thread guide eyelet can its holder be fixed by means of a leaf spring, the sensor is to be attached to the leaf spring. The Leaf spring itself is said to be essentially level be arranged parallel to the thread movement. But it is also possible instead of a leaf spring part of the Thread guide or the thread guide eyelet itself as a spring form, the sensor or sensors then on this spring part is or are attached.

The piezo sensors used in the prior art are piezo crystals that have a pronounced resonance have and thereby caused for the purpose of the invention are not sufficiently broadband.

A particular embodiment of the present invention is characterized in that the piezo film is a so-called PVDF film is the most inexpensive to get and is extremely thin. These piezo foils are very broadband and the use of such a piezo film advantageously does not lead to falsification of the measured vibrations.

It is also possible according to the invention, as in claim 5 specified for one or more thread tension sensors to provide a non-thread-bearing reference sensor, which is a signal dependent on machine vibrations emits, the thread tension signals with the reference signal can be compared and a difference value is formed can be. The reference signal can also be used as a threshold for the generation of binary thread break information be used. But it is also possible to use the Reference sensor loud environmental noises such as ultrasound from Recognize compressed air etc. and generated in the same period Declare thread tension information.

Fig. 1a

eine Seitenansicht einer Fadenführungsöse einer Ringspinnmaschine, wobei diese Öse mit einem Fadensensor ausgestattet ist,

Fig. 1b

eine Draufsicht der Ausführung gemäß Fig. 1a,

Fig. 2

eine schematische Darstellung einer Spinnstelle einer Ringspinnmaschine mit der Fadenführungsöse der Fig. 1a und 1b,

Fig. 3a

eine graphische Darstellung der zeitlichen Abhängigkeit der Auslenkung der Fadenführungsöse bei starker Fadenspannung,

Fig. 3b

eine Spektral-Darstellung der Auslenkung bei starker Fadenspannung,

Fig. 4a

eine graphische Darstellung der zeitlichen Abhängigkeit der Auslenkung der Fadenführungsöse bei schwacher Fadenspannung,

Fig. 4b

eine Spektral-Darstellung der Auslenkung der Fadenführungsöse bei schwacher Fadenspannung,

Fig. 5a, 5b und 5c

verschiedene elektronische Sensörsignalbearbeitungsmöglichkeiten,

Fig. 6

eine weitere Ausgestaltung eines Fadenspannungssensors, und

Fig. 7a

eine schematische Darstellung einer besonderen Ausführung einer Fadenführungsöse, die für die vorliegende Erfindung besonders geeignet ist, wobei die Führungsöse entsprechend den Fig. 1a und 1b eingebaut wird,

Fig. 7b

einen Querschnitt nach der Linie VIIb-VIIb der Fig. 7a,

Fig. 7c

einen Querschnitt nach der Linie VIIc-VIIc Fig. 7a,

Fig. 8

ein Blockschaltbild eines mitlaufenden Filters in SC-Ausführung,

Fig. 9

eine schematische Darstellung einer besonderen Ausführung eines Fadenspannungssensors,

Fig. 10a und 10b

zwei Möglichkeiten, die von einer Gruppe Fadenspannungssensoren enthaltenen Signale auszuwerten, um Fadenspannungssignale zu erzeugen, und

Fig. 11

eine Möglichkeit, die von einer Vielzahl von Sensoren erhaltenen Signale zu verarbeiten, um reine Fadenbruchsignale zu erzeugen.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing, in which:

Fig. 1a

2 shows a side view of a thread guide eye of a ring spinning machine, this eye being equipped with a thread sensor,

Fig. 1b

a plan view of the embodiment of FIG. 1a,

Fig. 2

1 shows a schematic representation of a spinning station of a ring spinning machine with the thread guide eye of FIGS. 1a and 1b,

Fig. 3a

a graphical representation of the time dependence of the deflection of the thread guide eyelet when the thread tension is high,

Fig. 3b

a spectral representation of the deflection with strong thread tension,

Fig. 4a

a graphical representation of the temporal dependence of the deflection of the thread guide eyelet when thread tension is weak,

Fig. 4b

a spectral representation of the deflection of the thread guide eyelet with weak thread tension,

5a, 5b and 5c

various electronic sensor signal processing options,

Fig. 6

a further embodiment of a thread tension sensor, and

Fig. 7a

2 shows a schematic representation of a special embodiment of a thread guide eyelet which is particularly suitable for the present invention, the guide eyelet being installed in accordance with FIGS.

Fig. 7b

7a shows a cross section along the line VIIb-VIIb in FIG.

Fig. 7c

a cross section along the line VIIc-VIIc Fig. 7a,

Fig. 8

a block diagram of a moving filter in SC version,

Fig. 9

1 shows a schematic illustration of a special embodiment of a thread tension sensor,

10a and 10b

two possibilities for evaluating the signals contained by a group of thread tension sensors in order to generate thread tension signals, and

Fig. 11

a way to process the signals received from a variety of sensors to produce pure thread break signals.

In order to facilitate the following explanations, referred to Fig. 2. Fig. 2 shows a side view a spinning station 10 of a ring spinning machine, in which a thread 12 leaves the outlet rollers 14, 16 of the drafting system and through the thread guide eyelet 18 and an anti-balloon ring 20 to one rotating on the ring track 21 of the ring bench 23 Ring traveler 22 leads, causing it to the rotating spindle sleeve 24 is wound up to a cop 26. Through the Rotation of the rotor thus turns the thread around the spindle sleeve led around that because of the centrifugal force Balloon trains through the anti-balloon or balloon containment ring 20 is limited and in the thread guide eyelet has its top. The friction and air resistance of the runner, the air resistance of the thread and the frictional resistance between thread and runner and between thread and balloon confinement ring generate a thread tension that is in place the thread guide is measurable.

This thread tension increases with increasing spindle speed.

Of particular interest is a spindle speed range between about 6000 rpm and 20,000 rpm, with the thread tension sensor, as described here, without further ado for spindle speeds or runner numbers (which only by 1 or 2% are lower than the spindle speeds and thus this can be equated) up to 30,000 rpm and higher are.

Touching the tensioned thread in the thread guide eyelet leads to frictional forces, both in horizontal as also work in the vertical direction.

In the embodiment of the thread sensor according to the invention shown become the horizontal components of this frictional force exploited due to the coefficient of friction the thread tension are proportional. This thread sensor is shown schematically in Figs. 1a and 1b. Here the thread guide eyelet 18 is so tapered in the rear part, that a bendable, resilient zone 30 with the shape of a Leaf spring is created. The leaf spring-like part 30 is on its end facing away from the thread guide eyelet into a clamping block 35 clamped and by means of this clamping block on Frame of the ring spinning machine on a longitudinal rod 37 of the ring spinning machine held. On the flat right side 34 of the bendable resilient zone of the leaf spring is a strain sensitive Sensor element 32 attached, which preferably consists of a PVDF piezo film. This slide gives about that Connection cable 36 a strain-dependent electrical signal to a downstream electronics (Fig. 5). The thread 12 runs essentially in a straight line from the pair of delivery rollers 14, 16 to the thread guide 18 and is due to the developing Balloons deflected on the thread guide. The rotation of the Runner 22 causes the thread to make a circular movement runs inside the thread guide, causing the on alternate the forces applied to the left and the right side of it. This will make the leaf spring 30 also bent to the left and to the right (L and R in Fig. 1b), so that the piezo film also executes an alternating movement and generates an alternating voltage. This changing movement is important for them How the sensor works.

Although in the embodiment according to FIGS. 1a, 1b and 2 Piezo film is arranged in a plane that the Includes the thread running direction before the thread guide, could Piezo film or the leaf spring, for example laterally to be arranged offset to the thread guide. This too Arrangement would for lateral deflection of the leaf spring lead to both sides.

There is also the possibility of the thread guide eyelet to be formed in one piece from shaped sheet metal as in FIGS. 7a, 7b and 7c. The one made of spring steel Guide eye is shaped so that it in the leaf spring part 32 originally straight or rectangular cross section (Fig. 7c) of the sheet metal strip at least essentially maintained. At the Transition into the actual eyelet 18 changes this cross section in an arcuate cross-section (Fig. 7b), so that the narrowest passage of the eyelet through the curved middle Area 18 'of the strip is formed while the edge areas farther from the center of the eyelet. By this low-cost training is the Always thread from the curved area 18 'of the strip guided, scraping the thread on the edges of the strip does not occur. The sheet metal strip can in the leaf spring part be wider than in the eyelet as indicated at 34 '.

3a first shows the temporal course 38 of FIG lateral deflection of the thread guide eyelet in strong Thread tension, and accordingly for an execution 1a and 1b. It can be seen that curve 38 according to FIG. 3a essentially represents a type of sine wave 40 a superimposed high-frequency oscillation 42 of a complex type. The sine wave corresponds to the speed of the ring traveler 22 and the superimposed vibrations contain information over all other vibrations that the thread guide eyelet is exposed.

If one carries out a spectral analysis of the sensor signal according to FIG. 3a, one obtains a result, as shown in FIG. 3b. Here you can clearly see the rotor speed f ₁ as a fundamental oscillation in the course of the deflection. The basic vibration is assigned harmonic vibrations f ₂ , f ₃ , f ₄ to f ₉ and the so-called thread noise, which ranges from f ₁₀ to f ₁₁ . The thread noise is caused on the one hand by the fibrous surface of the thread, and on the other hand by the constantly fluctuating cross-section of the thread (thinning or thickening).

Both the level of the speed f ₁ and the level of their harmonics f ₂ to f ₉ are a function of the thread tension. This makes a comparison between FIGS. 3a and 3b on the one hand and FIGS. 4a and 4b on the other hand clear.

From Fig. 4b you can see that the spectral composition the signal of the spectral composition of Fig. 3b very is similar, but the amplitudes are lower.

So there is an evaluation of the sensor signal in both Frequency ranges possible. The evaluation can go that the level of the thread tension is detected as a value, or that only a level comparison with a reference level becomes. This reference level can vary from machine parameters such as Depending on the spindle speed, maintenance condition etc. Of the Comparison with a reference level reduces the Thread tension information on a pure thread running or Thread breakage information, what the data transmission and Data evaluation effort significantly reduced. So it is possible to design a ring spinning machine so that at all Spinning positions only a thread break signal is generated, however the thread tension is also measured at some spinning positions becomes. The actual sensor is at all spinning positions same, only in the evaluation of the sensor signal there there is a difference.

The very broadband sensitivity of an invention Thread tension sensor, according to current investigations ranges from less than 1 Hz to more than 1 MHz, has to Consequence that not only the thread tension of the sensor signal incoming, but also machine vibrations, the majority from the range of spindle or rotor speed, but also of high-frequency components from the area of thread noise come. If a thread runs through the thread guide eyelet, do not disturb these machine vibrations because they are too are weak. In the event of a thread break, these come Vibration signals but appear and deceive a very weak thread tension signal.

Therefore, a reference sensor is attached to the machine who works under exactly the same conditions as that Thread tension sensor, i.e. he will also be on a thread guide attached, but on one that does not lead a thread. The signal from this reference sensor is similar processed like the signals from the thread-guiding sensors. Out the signal from the reference sensor is now the upper one Reference level won. The reference sensor delivers the Reference level for one or more thread break sensors. This eliminates local conditions that affect the noise level determine, taken into account. It is preferred for groups with 20 to 60 active sensors, one reference sensor each.

Possible versions of the signal evaluation electronics are in 5a to 5c.

5a, the signal present at terminal 52 the sensor is amplified with one or more amplifiers 54, with filter 56 of unwanted signal components exempt and then a rectifier / integrator 58 fed. The filter 56 can be a so-called moving Be a filter that controls a center frequency according to the respective rotor speed. This Center frequency can also be asymmetrical in the frequency pass band of the filter. A particularly preferred filter This type will be described later in connection with FIG. 8 described.

The output signal of the rectifier / integrator 58, the on terminal 60 is present, then the circuit shown in FIG. 5b supplied as an input signal. The circuit according to FIG. 5a is identified overall by the reference number 62.

5b shows the signal present at terminal 60 by means of an analog / digital converter 64 into a digital signal converted by a subsequent microcontroller 66 is analyzed to gain the thread tension. The Terminal 70 allows a reference voltage to the Analog / digital converter to apply, this reference voltage is obtained from the reference sensor mentioned above and for the purpose of comparison with the signal present at terminal 60 also by a circuit corresponding to circuit 62 is being prepared. The one generated by the microcontroller Thread tension signal is present at terminal 68 and can Machine control fed and here in controlling the speed of rotation of the Spindle drive are taken into account.

5c shows an alternative embodiment of the evaluation of the signal present at terminal 60 by a comparator 72, which compares it in analog form with a reference voltage U _Ref which is present at terminal 74 and, as mentioned above, from the reference sensor via a Circuit corresponding to the circuit 62 is obtained. The output signal of the comparator 72 is then further processed by a microcontroller 76 into a thread tension signal which can be tapped at the terminal 78. The thread tension signal can be displayed or evaluated in accordance with the thread tension signal present at terminal 68. 5c, the analog / digital conversion takes place in the microcontroller 76.

Both in FIGS. 5b and 5c, instead of applying a real-time reference voltage to the reference sensor, a predetermined reference voltage U _Ref can be used, which is either constant or whose level can be varied depending on machine operating states.

The. Fig. 6 shows an alternative evaluation, in particular can be used if a reference sensor 80, is attached to the machine as explained above, i.e. when a reference sensor 80 is attached to a thread guide that does not have a thread.

6 first shows a series of input terminals 52, 52.1, 52.2 to 52.n, each of which is the signal of a thread guiding sensor 32. Each terminal 52 to 52.n leads to a respective circuit 62 according to FIG. 5a and Output terminals 60, 60.1 to 60.n of these circuits 62 applied to an electronic switch 81, which in the Is able to use the signals successively or in a particular Order or in a selected order to a continue circuit 82, this further Circuit 82 either according to Fig. 5b, or 5c can be formed. the clamp 52.r carries the voltage from the reference sensor 80, which also by means of a circuit 62 corresponding to FIG. 5a is amplified, filtered or integrated. Like the arrow 84 shows the output signal of the reference sensor 80 associated circuit 62 the reference voltage for the Further processing circuit according to FIG. 5b or FIG. 5c.

In other words, the level of the reference sensor 80 becomes with the level of the thread guiding sensors 32, 32.1, 32.2 to 32.n compared. The difference is then considered pure Thread tension signal processed further, for example corresponding to Fig. 5b or 5c. The switch 62 is in Usually not designed as a mechanical switch, but as an electronic circuit, for example after a multiplexing process. 6 has an arrangement the advantage that only a complex evaluation circuit is required to receive signals from a variety of thread break sensors to further process thread tension signals.

In a ring spinning machine with several spinning positions, for example 1000 or 1200 spinning positions, becomes a piezo film sensor provided with each thread guide, so that a thread break signal from each of the total available spinning positions can be generated. In addition, the wiring made so that at certain spinning positions, for example every twentieth or fiftieth spinning position a possibility there is to measure the respective thread tension. On The machine will then have one or two thread guides per side provided that do not lead a thread, but which just like the other thread guides trained and also with Piezo film sensors are equipped to the above mentioned Generate reference signals.

A particularly preferred version of a moving Filters is shown in FIG. 8. It is here a block diagram showing the application of a filter in the SC version (SC means "switched capacitor"), which is preferably in the form of a chip, namely the Chip MF / 10 from National Semiconductors.

Since the pass band of the filter corresponds to the respective Rotor speeds is changed, it is necessary generate a frequency signal that corresponds to the rotor speed. It is known that the rotor speed is only slight is lower than the spindle speed of the ring spinning machine. With a ring spinning machine, the spindle speed can be reduced relatively easy to determine, so that instead the rotor speed the spindle speed as a guide for takes the filter. The generation of this frequency signal is shown in Fig. 8. The spindles are one Main motor 100 driven, via a so-called vertical shaft 102 and belts (not shown), each four spindles drive. The exact design of this drive is in the state well known in the art, e.g. Rieter ring spinning machines G5 / 1.

To a signal proportional to the spindle speed generate, is on the main shaft of the drive motor Tachometer generator 104 mounted. This essentially exists a gear 106 and an initiator or sensor 108, which counts the gaps 110 in the gear and one of the speed of the main engine dependent signal that is indicated in the drawing as "f-sensor". The exact The frequency of this signal depends on the number of teeth on the gear and the speed of rotation of the main motor.

After a translation between the main engine and the The spinning of the ring spinning machines takes place due to the intermediate drives, it is necessary that Multiply the frequency signal by a factor to the to reach the actual spindle speed. But even then the frequency of the signal can be increased even further since one a clock frequency required to control the filter 56 although proportional to the spindle speed or rotor speed is, but is about a hundred times higher in frequency. At a spindle speed of 12000 rpm, which is 200 Hz corresponds, for example, one needs a clock frequency of 20 kHz. The multiplier 112 in the drawing indicated circuit therefore receives the frequency signal of the Sensor at their input and delivers the desired higher Clock frequency f-clock at its output.

berechnet, wo n das Übersetzungsverhältnis Drehzahlspindel zu Drehzahlhauptmotorantrieb ist.The factor by which the input signal is multiplied to produce the clock frequency signal is given by the equation:

calculates where n is the ratio of the speed spindle to the speed main motor drive.

This clock frequency is then on a two-phase clock generator 114, which is part of the SC filter 56. With this two-phase clock generator, two around the phases τ1 and τ2 generated shifted signals, which serve over the lines shown as an arrow, two To operate the switch. These switches serve one purpose Condenser with the negative terminal from time to time another capacitor 122 provided with an operational amplifier 120 to connect. The rate at which the switches closed and opened at the same time determines the effective impedance of the capacitance at the input of the opamp what again defines the center frequency of the bandpass filter. Center frequency of the filter leads.

The amplified sensor signal coming from the amplifier 54 becomes therefore placed at the input of the filter, and the filtered signal the rectifier / integrator is then at the output of the filter 56 58 fed, according to the circuit 5a. The described type of thread tension measurement can be performed at all rotor frequencies that well above the fundamental vibration frequency of the thread guide, i.e. the natural vibration frequency of the thread guide eyelet Suspension system lies. This fundamental oscillation frequency is normally at about 10 to 20 Hz and the label "Significantly above" indicates frequencies that are at one Factor of about 4 to 10 or higher. So that can Thread tension measuring method according to the present invention Rotor speeds above 100 Hz, i.e. approx. 6000 rpm be used. Because such speeds are below those of interest Useful speeds of the spindles of the ring spinning machine this lower limit of the voltage evaluation in practice no restriction.

An advantage of an SC-type filter is that the bandwidth of the pass band of the filter is proportional is changed to the center frequency in that the quality Q of the filter remains at least essentially constant, which the signal evaluation benefits.

Important when using the sensor according to the present Invention is that it is in a plane on the attachment of the Thread guide is attached so that the orbital movement of the Thread within the thread guide to a deflection of the Suspension on both sides and therefore to a corresponding one Elongation and compression of the piezo film on both sides leads. In other words, the sensor should be in the form of Piezo film in a plane containing the thread running direction or a plane parallel to this can be arranged such that the suspension of the thread guide to elastic movements both sides, based on the direction of the thread. In the ring spinning machine, the thread running direction means for example the direction of the thread between the Delivery roller pair and the thread guide or the middle Direction of the thread within the thread balloon, with the the geometric axis of the thread balloon.

Finally, FIG. 9 shows a thread tension sensor which works differently than previously described.

9 schematically shows that the thread guide eyelet 18 is attached to a web 92 of a thread guide holder 94 via a first load cell 90. More specifically, the thread guide eyelet is attached to one end face of the load cell 90, while the other end face of the load cell is attached to the web 92. On the other side of the web 92 there is another force measuring cell 96, which is also fastened to the web 92 with its one end, while a compensation mass 98 with the mass m _{2 is} attached to the end of the force measuring cell 96 facing away from the web. The load cell 96 is therefore aligned with the load cell 90, but is arranged on the other side of the web 92. The thread guide eyelet 18 has a mass m ₁ . Due to the thread movement, vibrations of the thread guide eyelet are generated and these lead to vibrations of the web, which are denoted by a in the drawing. Vibrations of the thread guide holder 94 also lead to vibrations of the web. Due to the fluctuating acceleration of the masses m ₁ and m _2, these vibrations lead to fluctuations in the forces on the load cells 90 and 96, so that these deliver output signals U1 and U2 with corresponding fluctuations.

These voltages U1 and U2 can be represented mathematically as follows: U1 = C1 (A. M 1 + F) U2 = C2 (A. M 2nd ). Here A is the acceleration of the web 92 and F is the desired thread tension. C1 and C2 are constants. If you now subtract these two signals, you get ΔU = U1 - U2 = A (C1. M 1 - C2. m 2nd ) + C1. F. If C1. m 1 - C2. m 2nd = 0 is (adjustment), one can write ΔU ≈ C1. F.

In other words, F is approximately equal to ΔU divided by C1. After C1. m _{1 is} constant and ΔU can be measured directly, a signal for the thread tension has been obtained by means of the invention.

A thread tension sensor of the type described last is therefore characterized in that a thread guide eyelet via a load cell on one side of a web a thread guide bracket is attached that on the another load cell on the other side of the web attached and with the first load cell is aligned, one being the mass of the thread guide eyelet compensating mass attached to the second load cell and that the output signals of the two load cells are supplied to a differential circuit whose Output signal of the thread tension is proportional.

At this point it should be clarified that so-called PVDF piezo films available from various manufacturers are, for example from the US company PENNWALT Corporation under the name "KYNAR" (registered trademark). PVDF is an abbreviation for polyvinylidene fluoride, which leads to the Class of piezoelectric polymers. Piezo foils of this type, suitable for use with the present Suitable are invention are preferably broadband with a Quality factor Q striving towards zero.

10a shows a particularly preferred embodiment for the processing of signals from a group of sensors 52.1 to 52.n and by a reference sensor 52.r, by means of of a multiplexer that has 16 inputs. For this Reason n will normally have a maximum value of 15 and the further input is for the reference sensor used. In practice, therefore, a blind thread guide intended for each group of 15 real thread guides, i.e. of thread guides that actually have a thread on one Lead spinning station and the circuit according to Fig. 10a is for each group of 15 real thread guides can be duplicated.

The sensor signals, i.e. the signals from sensors 52.1 to 52.n are amplified before multiplexer 150, filtered and rectified by the circuit according to Fig. 5a. The individual channels, i.e. the signals from sensors 52.1 to 52.n and 52.r with the analog / digital converter 152 one after the other connected, the microcontroller 154 to the multiplexer Sensor address determined. The levels of the sensors 52.1 to 52.n are compared with the reference level from the reference sensor 52.r compared in terms of amount, the difference corresponds to Thread tension and can either be used as a reference or after corresponding calibration as an absolute value.

In this example, the components are according to the circuit Fig. 5a provided for each sensor and in the Integrated bracket for the sensor. However, this is something complex and FIG. 10b shows a further improvement, after which each sensor only a respective amplifier is assigned, and the filter and the analog / digital converter are arranged after the multiplexer.

In further detail, the signals from sensors 52.1 to 52.n and the reference sensor 52.r in an enhanced form Multiplexer fed. Microcontroller 154 gives that Multiplexer the sensor address to be switched through. Behind the signal is filtered in the multiplexer, for example by means of a circuit according to FIG. 8, and by the Analog / digital converter 152 converted into a digital signal. This signal is then sent to the microcontroller 154 fed. The system works, consisting of analog / digital converter and microcontrollers not fast enough so a rectifier 156 becomes between the filter and the A / D converter used, which means that no more frequencies up must be converted to 300 Hz and evaluated, but only frequencies of approx. 1 Hz have to be measured. At favorable design of the circuit can the individual Amplifier stages in / at the sensors are replaced by a single gain stage behind the multiplexer. The 10a and 10b describe circuit variants which the Allow thread tension measurement on all sensors.

In contrast, Fig. 11 deals with the finding whether the thread is broken at the respective spinning positions.

The sensor signals are processed in parallel here. they are again in groups 52.1 to 52.n together with one Reference sensor 52.r combined. In this case, the The total number of sensors in a group can be up to 32.

As can be seen from Fig. 11, the signals are first amplified, filtered and rectified and then they become in respective comparators, each of which is the comparator 72 5c correspond with the reference signal from the reference sensor 52.r compared. The output of the respective comparators 72 is actually a digital signal since the comparator only decides whether the level of one active sensor is higher or lower than the reference level from the reference sensor. All signals are sent to the microcontroller 154 connected to parallel (port) inputs. Of the The advantage of this variant is that a simple and poorly performing i.e. inexpensive microcontroller used can be (for example, type 80C31 from Intel). A Thread tension measurement is excluded here.

It can be seen that the output signals of each Microcontroller 154, each of a single sensor group are assigned, all with a serial data bus communicate, for example the type RS232 or RS485.

The microcontrollers are exemplary for all circuit variants (about 50 pieces per machine) over an advantageous serial data bus connected to a master controller, which, for example, also through the component (chip) 80C31 can be formed by Intel. This master controller is intended for the evaluation of thread information and represents the machine control or a process control compressed Data, possibly statistically evaluated, are available.

It can be advantageous for machines with more than 1000 spindles be when the microcontroller is on two serial data buses distributed, for example a data bus for each side the machine.

It should also be noted that combinations 10a, 10b and 11 are possible, and that it is also possible to use the sensor signals as yes / no information (Thread break information) in parallel or by multiplexer feed to the microcontroller, while one sensor per microcontroller group as a thread tension meter using an A / D converter (which is an integrated part of the microcontroller can be evaluated.

Claims (11)

1. A ring spinning machine with a spindle drive, with at least one spindle position (10) comprising a spindle (24), with a spindle drive (100) rotatingly driving the spindle (24), with at least one thread guide (18) for guiding the substantially unspun thread (12) from a thread supply unit (14, 16) to the spinning position (10), with at least one thread tension sensor (32) for producing a thread tension signal which is representative of the thread tension of the thread (12) supplied to the spinning position (10) and whose level is compared with a reference level which is dependent on machine parameters such as spindle speed, maintenance state and the like, so that the result of the comparison can be supplied to the machine control unit and can be considered in the control of the rotational speed of the spindle drive (100) in the sense of maintaining a predetermined thread tension or a predetermined course of thread tension over the cop building process.
2. A ring spinning machine as claimed in claim 1, characterized in that a thread tension sensor is provided for measuring the thread tension at specific spinning positions, e.g. at every twentieth or fiftieth spinning position.
3. A ring spinning machine as claimed in claim 1 or 2, characterized in that the thread tension sensor is combined with the thread guide of at least one of the spinning positions, thus avoiding additional stress on the thread.
4. A ring spinning machine as claimed in one of the claims 1 to 3, characterized in that the thread tension sensor can be attached to the suspension (30) of a thread guide (18), with the sensor supplying an electric signal representative of the oscillations induced by the thread movement in the thread guide.
5. A ring spinning machine as claimed in one of the preceding claims 1 to 4, characterized in that a reference sensor is provided which like the actual thread tension sensor (32) or actual thread tension sensors (32, 32.1., ......, 32.n) is subjected to the vibrations of the machine, but is hardly or not influenced by a running thread (12), and that the signal of the reference sensor (80) supplies a reference level (U_ref) for the thread tension sensor (32) or the other thread tension sensors (32, 32.1 ...., 32.n).
6. A ring spinning machine as claimed in one of the claims 1 to 5, characterized in that the thread tension sensor is a piezofoil whose plane is disposed at least substantially in a plane containing the direction of the thread course or a plane parallel thereto in such a way that the suspension of the thread guide performs elastic movements on either side, that a tracking filter (56) for filtering the control signal is provided whose passband is guided according to the frequency (f₁) of an element winding up the thread at an at least substantially constant quality in order to gain either the frequency (f₁) of an element (22) winding up the thread (12) and/or the harmonic (f₂ to f₉) of said frequency (f₁), and that a device (66, 76) for measuring the level of the filtered-out frequency or frequencies is provided whose output signal corresponds to the thread tension.
7. A ring spinning machine as claimed in one of the claims 1 to 3, characterized in that the thread tension sensor is realized in such a way that a thread guide eyelet (18) is attached by way of a force-sensing cell (90) to the one side of a bridge (92) of a thread guide fixing means (94), that on the other side of the bridge (92) there is attached a further force-sending cell (96) on the same and is in alignment with the first force-sensing cell (90), with a mass m₂, which compensates the mass m₁ of the thread guide eyelet (18), being attached to the second force-sensing cell, and that the output signals of the two force-sensing cells (90, 96) are supplied to a differential circuit whose output signal is proportional to the thread tension.
8. An application of a thread tension sensor for controlling the spindle speed of a ring spinning machine as claimed in one of the claims 1 to 7, with the level of the thread tension signal being compared with a reference level which depends on machine parameters such as spindle speed, maintenance state or the like, the result of the comparison being supplied to the machine control unit and during the control the adherence to a predetermined thread tension or a predetermined course of the thread tension is taken into account over the cop building process.
9. An application of a thread tension sensor as claimed in claim 8, characterized in that the thread tension sensor is a piezofoil whose plane is at least substantially disposed in a plane containing the direction of the thread course or a plane parallel thereto in such a way that the suspension of the thread guide performs elastic movements on either side, that a tracking filter (56) for filtering the control signal is provided whose passband is guided according to the frequency (f₁) of an element winding up the thread at an at least substantially constant quality in order to gain either the frequency (f₁) of an element (22) winding up the thread (12) and/or the harmonic (f₂ to f₉) of said frequency (f₁), and that a device (66, 76) for measuring the level of the filtered-out frequency or frequencies is provided whose output signal corresponds to the thread tension.
10. An application of a thread tension sensor as claimed in claim 8 or 9, characterized in that the thread tension sensor can be attached to the suspension (30) of a thread guide (18), with the sensor supplying an electric signal representative of the oscillations induced by the thread movement in the thread guide.
11. An application of a thread tension sensor as claimed in claim 8, characterized in that a thread guide eyelet (18) is attached by way of a force-sensing cell (90) to the one side of a bridge (92) of a thread guide fixing means (94), that on the other side of the bridge (92) there is attached a further force-sending cell (96) on the same and is in alignment with the first force-sensing cell (90), with a mass m₂, which compensates the mass m₁ of the thread guide eyelet (18), being attached to the second force-sensing cell, and that the output signals of the two force-sensing cells (90, 96) are supplied to a differential circuit whose output signal is proportional to the thread tension.

Images