IT202100017966A1 - MOTORIZED POSITIVE YARN FEEDER WITH SELECTABLE OPERATING MODE, AND YARN FEEDING EQUIPMENT USING THE SAME. - Google Patents

Description

MOTORIZED POSITIVE YARN FEEDER WITH MODE SELECTABLE OPERATION, AND YARN FEEDING APPARATUS USING THE SAME.

DESCRIPTION

The present invention relates to a motorized positive yarn feeder with operating mode. operating selectable, and a yarn feeding apparatus utilizing the same.

As is known, in a generic yarn feeding process, several yarns can be fed towards a weaving machine from respective motorized yarn feeders of the so-called "positive" type.

This type of power supply? equipped with a motorized spool on which the yarn ? wound repeatedly (e.g., 3 or 4 wraps) so as to adhere to it by friction. By rotating the spool, the yarn unwinds from an upstream reel and is fed to a downstream textile machine.

Are power supplies known which operate according to a mode? so-called ?controlled voltage? operation. A power supply like this? described, for example, in EP1710334B1.

In this case, the yarn tension is continuously monitored by a tension sensor which can be integrated into the power supply itself. A unit? control, also possibly integrated in the power supply, modulates the speed? of the spool based on the signal received from the tension sensor, in order to stabilize the tension of the yarn fed to the weaving machine on a fixed value or on a profile set by the user, to the advantage of the quality? of the boss.

The mode? normally controlled voltage operating? preferred for workings containing designs or patterns (Jaquard) because, due to the design, the quantity? of yarn taken from the textile machine varies in a way that is difficult to predict during the production of the garment.

As known, power supplies that work at controlled voltage are not able to guarantee that the amount of water supplied to the textile machine is of correct yarn. In fact, the voltage, although controlled in the vicinity? of the exit point of the yarn from the feeder, pu? vary before the yarn reaches the weaving machine, due to the friction between the yarn and the various yarn guide rings along the way, the effects of friction being of course not subject to control.

It follows that the different influences of the friction between one yarn and another cause differences in the length of the yarns supplied by the different feeders, with possible defects in the garment.

In order to control the quantity? of yarn supplied, feeders are also known which operate according to a mode? so-called ? at speed? controlled?. A power supply like this? described, e.g., in EP1491673A1.

In this case, the power supply ? set to control the speed? of yarn feeding in order to stabilize it on a fixed value or on a profile set by the user.

The mode? operational at speed? normally controlled? preferred for smooth workmanship, that is to say, without designs or patterns (Jersey), since? the speed regulation? of rotation of the spools as a function of the speed? of rotation of the weaving machine allows to obtain uniform garments without the so-called "barring".

As known, the devices that work at speed? controlled are less affected by friction, but are subject to other drawbacks.

In particular, yes? found that even a minimum error in the regulation of the speed? produces a progressive accumulation of the error in the regulation of the position of the spool, since? from the mathematical point of view the position, as well known, ? given by the integral of the velocity?.

Therefore, in the long run, the error in the position of the spool translates into a large error in the quantity - intended as ?length? -of yarn fed with respect to the real request of the textile machine.

For this reason, Jersey processes are often performed using the so-called positive feeders with mechanical drive, in which the rotation of the spool is? impressed directly by the textile machine through a belt transmission system designed according to a predefined transmission ratio. This system ensures that the length of yarn delivered by the feeder always corresponds exactly to the length required by the weaving machine, so to improve the quality? of the garment in terms of uniformity. In this case we normally speak of operation ?in mechanical axis?.

However, belt-driven feeders are not able to work in mode. voltage controlled and also the operation in the mechanical axis, albeit satisfactory in terms of quality? of production, has big limits in terms of versatility? and possibility? adjustment (eg, to vary the transmission ratio it is necessary to replace the pulleys of the belt drive system with others of a different diameter) as well as? of flexibility? and simplicity? line setup.

Am I otherwise? known, e.g., from US3858416, EP2067886B1, EP2572023B1 and EP2809838B1, power supplies able to operate both in mode? voltage-controlled both in mode? at speed controlled, which can use different switching logics from one mode? to the other.

However, these power supplies are all affected by the aforementioned problems of inaccuracy of power supplies operating at higher speeds. controlled, in relation to the accumulation of the error in the quantity? of yarn sold.

In the light of the above, the main purpose of the present invention is to create a motorized positive yarn feeder in which the mode? operative more suitable is selected according to the type of processing, with a more? precise and reliable with respect to known solutions in terms of length of yarn supplied with respect to the length of yarn required by the weaving machine.

Another purpose? that of realizing a yarn feeding apparatus using the yarn feeders according to the invention.

The aforementioned purposes and other advantages, which ones will be more? clearly from the continuation of the description, are achieved by a yarn feeder having the characteristics disclosed in claim 1, while the dependent claims define other advantageous characteristics of the invention, albeit secondary.

Will you describe? now in greater detail the invention, with reference to some of its preferred but not exclusive embodiments, illustrated by way of non-limiting example in the attached drawings, in which:

Fig. 1 schematically illustrates a multiplicity? yarn feeders according to the invention while feeding yarn to a weaving machine;

Fig. 2 schematically shows in greater detail one of the yarn feeders of Fig. 1 as it feeds yarn to the weaving machine, according to an embodiment of the invention;

Fig. 3 ? a view similar to Fig. 2 , illustrating an alternative embodiment of the invention;

Fig. 4 ? a graph illustrating the trend of tension over time in a first phase, with the yarn feeder operating in a first mode? operational;

Fig. 5 ? a graph illustrating the trend of tension over time in a second phase, with the yarn feeder still operating in the first mode? operational;

Fig. 6 ? a graph illustrating the trend of tension over time in the second phase, with the yarn feeder operating in a second mode? operational;

Fig. 7 ? a graph illustrating the trend of tension over time in a third phase, with the yarn feeder still operating in the second mode? operational;

Fig. 8 ? a flowchart describing a first criterion for automatic switching between two different modes? operational; Fig. 9 ? a flowchart describing a second criterion for automatic switching between two different modes? operational.

As illustrated in Fig. 1, a yarn feeding apparatus comprises a series of motorized positive yarn feeders 10 which feed respective yarns Y to a generic weaving machine TM.

Each of the feeders 10 comprises a motorized spool 12 on which the yarn Y is wound repeatedly (e.g., 3 or 4 wraps) so as to adhere to the spool by friction. By rotating the reel 12, the yarn Y unwinds from an upstream reel S and is fed to the downstream weaving machine TM.

The power supply 10 ? equipped with a control unit CU connected to receive a position signal of the reel 12 from means for measuring the position 16 and a tension signal of the yarn output from the feeder 10 from a tension sensor 20, which can? be advantageously incorporated in the feeder 10.

According to the invention, the unit? of control CU ? programmed to work selectively in one mode? position control operation, in which it receives a position signal qTM from the textile machine TM and, on the basis of the signal received from the position measuring means 16, controls the position of the reel 12 in a closed loop according to a transmission ratio that can be set electronically with respect to the position of the textile machine TM, or in a modality? operational voltage control, in which it controls the speed in closed loop? of the spool 12 on the basis of the signal received from the tension sensor 20, so as to stabilize the tension of the yarn Y on a tension reference value or a tension profile that can be set by the user.

With reference now also to Fig. 2, the textile machine TM ? equipped with an encoder E to generate the position signal of the qTM textile machine through a TMC communication unit. The latter converts the signal generated by the encoder E into a signal suitable for transmission on a communication line, in this embodiment, a serial communication line L to which all the power supplies 10 are connected.

The signals generated by the position measuring means 16 and by the voltage sensors 20 of the various power supplies 10 can advantageously be monitored by the operator via a central control system (not shown) connected to the serial communication line L.

The position signal qTM is multiplied in a multiplier block RB according to a transmission ratio (typically less than 1, e.g., 1/100 depending on the geometric characteristics of the machine and the feeder) that can be set by the user U, in so as to generate a multiplied position signal of the qTMR textile machine.

The position measuring means 16 can comprise a further encoder EF, or a group of Hall sensors or other systems capable of generating signals as a result of the rotation of the reel.

The unit? of control CU comprises a block of conversion of the position POS that converts the signal of the second encoder EF in a signal of position of the spool qR, and a block of conversion of the speed? VEL which converts the signal of the second encoder EF into a speed signal? of the wR spool.

The multiplied textile machine position signal qTMR and the spool position signal qR are compared in a first subtractor node NP of a position control loop PL to generate a position error qE.

Is the position error qE converted into a speed reference? w through a first proportional-integrative controller PI1.

The speed reference? w and the speed signal? of the spool wR are compared in a second node subtractor NV of a ring of control of the speed? VL to generate an error speed? wE.

The speed error? wE is converted into a current reference I by a second proportional-integrative controller PI2.

In this embodiment, the spool 12 ? driven by a three-phase electric M motor. The three current signals supplying the motor M are converted into an equivalent quadrature current signal IR through a current conversion block CUR.

The current reference I and the equivalent current signal IR are compared in a third subtractor block N1 of a current control loop IL, so as to generate a current error IE.

The current error IE is converted into a voltage reference V through a third proportional-integrative block PI3.

The voltage reference V is sent to regulation and actuation means which, in this embodiment, comprise a pulse width modulator PWM which controls the electric voltage supplied to the motor M via a Mosfet MOS bridge.

The transmission ratio can? be entered directly by the user or calculated by the unit? of control CU, on the basis of geometric considerations, in a calculation block CR as a function of the length of yarn that the user U wishes to be inserted at each machine revolution.

Thanks to the control in the position of the spool carried out according to the embodiments described above, the feeder always delivers exactly the quantity of yarn absorbed by the weaving machine, as if the feeder and the weaving machine were connected by a mechanical transmission (mechanical axis control). There? allows to avoid the accumulation of error that is found in the known systems in which, to control the quantity? of fed yarn, you control the speed? of the spool.

In one aspect of the invention, does the system switch between the two modes? machining (position control and voltage control) on user command. In this case, the unit? control CU can? be provided with a user interface (not shown) to make the selection.

Alternatively, or in addition, the unit? control CU can? be programmed to automatically switch between position control and voltage control, and vice versa, upon the occurrence of pre-set conditions related to voltage measurement.

In particular, Fig. 4 illustrates the trend of the voltage over time during a processing of the Jersey type, in which the feeder 10 operates in mode? control in position. At this stage, the unit? control unit CU continues to monitor the instantaneous voltage with a relatively large band, e.g., between 500Hz and 1000Hz.

A first criterion, schematically illustrated in the flow diagram of Fig. 8, can provide that the system starts in mode? control in position (block 110) and continue to monitor the voltage (block 112). If the system, at block 114, starts detecting a series of periodic voltage peaks, as illustrated in Fig. 5, thus highlighting the a withdrawal of discontinuous yarn by the textile machine (eg, during the creation of a design) the unit? of control CU switches automatically in the mode? voltage control (block 116), which will act? so as to reduce the positive and negative voltage peaks, as shown in Fig. 6.

Yarn tension continues to be monitored at block 118.

If, during controlled voltage operation, the system, at block 120, detects that the peaks have ceased, as illustrated in Fig. 7, thus highlighting the again a continuous withdrawal of yarn by the textile machine, the unit? of control CU switches back to the mode? control in position.

According to a different criterion to automatically switch from the mode? control in position to the mode? of voltage control, schematically illustrated in the flow chart of Fig. 9, a minimum threshold and a maximum threshold of the average voltage measured are set.

The system starts in mode? control in position (block 210) and continues to monitor the voltage (block 212). If the system, at block 214, detects that the average voltage ? output from the threshold range, the unit? of control CU switches automatically in the mode? voltage control (block 216) in order to bring the average voltage within the predetermined threshold range.

Yarn tension continues to be monitored at block 218.

If during controlled voltage operation, at block 220, the system detects that the voltage ? returned to the threshold range, the unit? of control CU switches back to the mode? control in position.

Otherwise, at block 222 the unit? The CU checks whether a pre-set limit (e.g. a time limit or a pre-set number of attempts) has expired.

If the limit has not expired, the unit? control continues to operate in mode? voltage control.

If the limit is reached, the unit? control CU can? generate an alarm (block 224) and possibly stop the weaving machine.

According to a still different criterion, the unit? control CU can? be programmed to operate in mode? tension control when the position signal qTM of the textile machine TM indicates that this ? stops, and operate in mode? of position control when the textile machine TM ? in movement. This criterion is particularly advantageous as it allows the operator to knot the yarns when the textile machine is working. stop.

In an advantageous embodiment of the invention, the feeder 10 is also enabled to carry out recovery phases in which it rotates in the opposite direction to that of feeding to keep the yarn Y under tension when the textile machine TM temporarily interrupts the withdrawal or returns part of the yarn previously withdrawn.

In this case, the unit? control CU could be programmed to work in mode? of control in position in phase of alimentation and in modality? tension control in the recovery phase, during this last phase bringing the yarn tension back to a pre-set value. When, after the recovery phase, the textile machine TM starts picking up yarn Y again, the unit? of control CU recommutes automatically in the modality? control in position.

The circumstance that the weaving machine is moving can? be deduced from the movement of the encoder E on board the textile machine TM.

The yarn withdrawal condition by the TM textile machine can? be deduced from the instantaneous voltage measured by the voltage sensor 20. In particular, while the device works in mode? control in position, during which it follows the movement of the encoder E of the textile machine TM, the unit? control CU can? be programmed to interpret a sudden drop in instantaneous tension as an interruption in thread withdrawal, even if the TM weaving machine ? still moving. In this situation, as previously mentioned, the unit? of control CU switches automatically in the mode? tension control by recovering yarn to restore the desired tension.

At this stage, the unit? control CU can? also check the position of the spool 12 and, if it detects a positive movement greater than a quantity? pre-established (for example, the take-up quantity plus 2 or 3 rounds), recognizes that the feeder has started to give yarn back to the machine and therefore switches back to the pre-established mode. control in position.

A further criterion for switching between the two modes? operational consists in controlling the variation of position effected by the spool 12 while the feeder works in mode? voltage control and, when this variation of position ? positive and close (according to pre-established thresholds) to the change in position required by the position reference ?TMR, go back to work in modality? control in position.

The yarn recovery function is particularly advantageous for textile machines equipped with so-called striping or ?Striper? devices.

Advantageously, the voltage reference to be used during operation in mode? voltage control (both in the supply phase and, possibly, in the recovery phase), pu? be recalculated during operation in mode? control in position based on an average voltage measured in this phase. In particular, during operation in mode? control in position, pu? a deviation of the average voltage measured from the desired one may occur due to friction. Therefore, in mode voltage control, to compensate for the effects of friction ? the average voltage value to be used as a reference for the voltage should be the updated one.

The realization of Fig. 3 differs from the previous one for the only fact that the speed regulation ring? ? absent. Therefore, of this realization it will not be? repeated the description and the elements equivalent to the embodiment of Fig. 2 are indicated by the same reference with the addition of a prime.

In the embodiment of Fig. 3, the position error qE' is converted directly, through a proportional-integrative derivative block PID', into a current reference I' which, similarly to the previous embodiment, is compared with the equivalent current signal IR ' in the subtracting node NI' to generate the current error IE'.

Yes ? It has been found in practice that the yarn feeder according to the invention allows to select the mode? operational both manually and automatically according to the switching criterion considered pi? suitable for the type of processing.

In particular, the mode control in position allows you to control the consumption of yarn, in terms of length of yarn supplied with respect to the length of yarn required by the weaving machine, in a much more efficient way. precise and reliable compared to the known solutions in which the speed is controlled? of the spool.

The power supply according to the invention, in mode? voltage control, has a precision and reliability? in the supply of yarn (in terms of length of yarn supplied per machine revolution) comparable to that of mechanical feeders operated by mechanical transmissions, with the advantages deriving from the electric drive in relation to the greater flexibility? adjustment (eg, of the transmission ratio) and the greater simplicity? in setting up the line.

Besides that, the possibility to alternate, on manual and/or automatic, the mode? of control in position (for workings without drawings and/or fantasies) and the modality? voltage control (for workings with drawings and/or patterns), makes the feeder according to the invention much more? versatile in relation to the different types of processing for which pu? be used.

Another advantage of the feeder according to the invention ? that of facilitating the calibration phase of the needle stroke of the textile machine.

As known, in fact, the calibration of this run requires the execution of a sample garment, during which a quantity must be supplied yarn constant per machine revolution. In this phase, the operator adjusts the stroke of the needles by attempts in order to equalize the tensions of all the yarns downstream of the feeders.

because this procedure requires a high precision in the supply of yarn in quantity? constant, until today it has given satisfactory results only with the use of mechanical positive feeders.

However, these power supplies are obviously devoid of voltage sensors, so that? the operator must use a portable reference instrument.

The device according to the invention , being equipped with its own voltage sensor, allows to carry out the adjustment in a more efficient way. practical and fast. In fact, the operator, through the central control system can? monitor the tensions of all the yarns in real time and possibly act only on the yarns that deviate most from the desired tension. The latter can be advantageously an average tension calculated by the central control system, and the yarns with too high or low tension can be graphically highlighted so as to facilitate their identification by the operator.

This system is evidently much more? advantageous how much greater? the number of yarns fed to the weaving machine.

Also, the voltage sensor can? recognize when the machine interrupts or resumes picking up the yarn, synchronizing with the processing of the machine. There? allows the feeder to be used to deliver the yarn to textile machines equipped with ruler devices (or stripers) that are able to stop and resume the consumption of some of the yarns while the textile machine ? in movement.

Furthermore, the tension sensor allows to detect yarn breakage in case the recovery system is present. In fact, in the event of yarn breakage, will the tension suffer? a sudden fall and the feeder will start? to rotate in the opposite direction in order to bring the tension back to the desired level.

When? There? does not occur within a set period, the unit? control can? be programmed to interpret this circumstance as a consequence of yarn breakage and generate a relative alarm.

Some preferred embodiments of the invention have been described, but the person skilled in the art will naturally be able to make various modifications and variations within the scope of the claims.

In particular, ? by itself It is clear that the different embodiments and the different operating criteria described above, pertaining to programming aspects, can be implemented simultaneously and selected by the user according to specific needs.

Furthermore, the expert in the field will be able to come up with different or modified criteria than those described for automatic switching between modes? operational. For example, the unit control could start in mode? voltage control and switch in the mode? control in position when? detects a substantially constant voltage without peaks from the beginning.

Again, the power supply may make use of motors of types other than those described herein, e.g., brushless DC motors, permanent magnet synchronous motors, single-phase DC brush motors, asynchronous motors, stepper motors, etc. others, which can still be driven by means of Mosfet bridges and PWM technique, or other technologies such as transistors or Mosfets operating as linear amplifiers.

Claims (16)

1. Yarn feeder, comprising a spool (12) on which ? suitable for repeatedly winding a yarn (Y), said reel (12) being driven in rotation by a motor (M) to take said yarn (Y) from a reel (S) and feed it to a textile machine (TM), a 'unit? control (CU) being connected to receive a position signal of the spool (12) from position measuring means (16) and a tension signal of the yarn delivered by the feeder (10) from a tension sensor (20), characterized by the fact that this unit? of control (CU) ? programmed to work selectively in one mode? position control system, in which it receives a position signal (qTM) from the textile machine (TM) and, on the basis of the signal received from said position measuring means (16), controls the position of the spool (12) in a closed loop according to a transmission ratio that can be set electronically with respect to the position of said textile machine (TM), or in a mode? voltage control, in which it controls the speed in closed loop? of said spool (12) on the basis of the signal received from the tension sensor (20), so as to stabilize the tension of the yarn (Y) on a tension reference value or a tension profile that can be set by a user. 2. Yarn feeder according to claim 1, characterized in that said unit? of control (CU) includes: - a multiplier block (RB), in which said position signal (qTM) is multiplied according to said transmission ratio to generate a multiplied position signal of the textile machine (qTMR), - a position control loop (PL), in which said multiplied position signal of the textile machine (qTMR) is compared with a spool position signal (qR) to generate a position error (qE), which is converted into a speed reference? (w) through a first proportional-integrative controller (PI1), - a speed control loop? (VL), in which the speed reference? (w) is compared with a speed signal? of the spool (wR) to generate an error speed? (wE) which is converted into a current reference (I) via a second proportional-integrative controller (PI2), - a current control loop (IL), in which the current reference (I) is compared with an equivalent current signal (IR) of the motor (M) to generate a current error (IE), which is converted into a voltage reference (V) via a third proportional-integrative block (PI3), e - regulation and actuation means (PWM, MOS) able to control the rotation of the motor (M) on the basis of said voltage reference (V). 3. Yarn feeder according to claim 1, characterized in that said unit? of control (CU') includes: - a multiplier block (RB') in which said position signal (qTM') is multiplied according to said transmission ratio to generate a multiplied position signal of the textile machine (qTMR'), - a position control loop (PL'), in which said multiplied position signal of the textile machine (qTMR') is compared with a spool position signal (qR') to generate a position error (qE'), which is converted into a current reference (I') via a proportional-integrative-derivative (PID') controller, - a current control loop (IL'), in which said current reference (I') is compared with an equivalent current signal (IR') of the motor (M') to generate a current error (IE') , which is converted into a voltage reference (V') via a proportional-integrative block (PI3'), e - regulation and actuation means (PWM', MOS') able to control the rotation of the motor (M') on the basis of said voltage reference (V'). 4. Yarn feeder according to claim 2 or 3, characterized in that said motor (M, M') ? of the three-phase type and said unit? (CU, CU') comprises a current conversion block (CUR, CUR') able to calculate in quadrature said equivalent current signal (IR, IR') from the three current signals which supply said motor (M, M '). 5. Yarn feeder according to one of claims 1-4, characterized in that said unit? (CU, CU') comprises a calculation block (CR, CR') suitable for calculating said transmission ratio as a function of the yarn length that the user (U, U') wishes to be inserted at each machine revolution . 6. Yarn feeder according to one of claims 1-5, characterized in that said unit? of control (CU) ? equipped with a user interface to manually select between these modes? operational. 7. Yarn feeder according to one of claims 1-6, characterized in that said unit? of control (CU) ? programmed to continuously monitor the yarn tension and automatically switch between these modes? operational upon the occurrence of pre-established conditions related to voltage measurement. 8. Yarn feeder according to claim 7, characterized in that said unit? of control (CU) ? scheduled for: - start in this mode? control in position (110), - switch to mode? voltage control (116) upon detection of a series of periodic voltage peaks (114), - switch back to said mode? control in position (110) upon cessation of said periodic voltage peaks (120). 9. Yarn feeder according to claim 7, characterized in that said unit? of control (CU) ? programmed for: - start in mode? control in position (210), - switch to mode? voltage control (216) when? the average voltage goes outside a pre-established threshold range (214), in order to bring the average voltage back within said threshold range, - if the voltage returns within the threshold range within a pre-set limit (220, 222), switch back to said mode? control in position (210), - if the voltage does not return within the threshold interval within said pre-set limit (220, 222), generate an alarm (224). 10. Yarn feeder according to claim 7, characterized in that said unit? of control (CU) ? programmed to operate in mode? voltage control when said position signal (qTM) indicates that said textile machine (TM) ? stops, and operate in mode? control in position when said textile machine (TM) ? in movement. 11. Yarn feeder according to one of claims 1-10, characterized in that ? enabled to carry out recovery phases in which it rotates in the opposite direction to that of feeding to keep the yarn (Y) under tension when said textile machine (TM) temporarily interrupts picking up or returns part of the picked up yarn. 12. Yarn feeder according to claim 11, characterized in that said unit? of control (CU) ? programmed to work in mode? of control in position in phase of alimentation and in modality? tension control in the recovery phase, during this last phase bringing the yarn tension back to a pre-set value. 13. Yarn feeder according to claim 12, characterized in that said unit? of control (CU) ? programmed to generate a yarn breaking alarm when, in the recovery phase, it fails to bring the tension back to a desired level within a pre-set time. 14. Yarn feeder according to one of the claims 1-13, characterized in that said voltage reference value is recalculated during operation in mode? control in position based on an average voltage measured in this phase. 15. Yarn feeding apparatus, characterized in that it comprises: - at least one yarn feeder according to one of claims 1-14, e - a textile machine (TM) adapted to transmit said position signal of the textile machine (qTM) to said unit? controller (CU) via a communication unit (TMC) and a communication line (L). 16. Yarn feeding apparatus according to claim 15, characterized in that it comprises a central control system connected to said communication line (L) for monitoring the signals generated by said position measuring means (16) by an operator.