CN111699144B

CN111699144B - Method, system and compensator device for feeding a yarn to a processing machine

Info

Publication number: CN111699144B
Application number: CN201980011856.XA
Authority: CN
Inventors: 蒂齐亚诺·巴雷亚; 马西莫·托马佐利
Original assignee: BTSR International SpA
Current assignee: BTSR International SpA
Priority date: 2018-02-06
Filing date: 2019-02-04
Publication date: 2022-07-22
Anticipated expiration: 2039-02-04
Also published as: TW201936477A; EP3749603A1; JP7181947B2; EP3749603B1; WO2019155346A1; JP2021512834A; US20210070582A1; IT201800002452A1; TWI780300B; CN111699144A

Abstract

A method, system and compensator apparatus for feeding a yarn to a processing machine, comprising the use of an apparatus for feeding a yarn to a textile machine operating in a discontinuous manner or with alternate action, and of an apparatus for compensating for variations in the yarn as it is fed or pulled by the textile machine, said compensator apparatus comprising a movable compensation device which performs this compensation so as to maintain a constant tension on the yarn even when the aforesaid variations in the case of feeding or pulling the yarn occur, said compensation device being rigid and connected to an electric actuator whose control unit is able to detect, when there is a variation in yarn feeding or pulling, the displacement of said compensation device with respect to a predetermined rest position and to return said compensation device to the rest position after such a variation. It is provided to continuously detect the yarn tension and to operate the electric actuator to maintain this tension at a constant value.

Description

Method, system and compensator apparatus for feeding a yarn to a processing machine

The object of the present invention is to provide a method for feeding a yarn to a machine for processing it according to the present invention. The invention also aims at a system and compensator apparatus according to the invention.

Constant-tension yarn feeders have long been known for feeding yarns or wires to textile machines for producing finished manufactured articles (for example knitwear or socks) or for processing the yarns, which can be used in combination with other yarns (for example machines for preparing the yarns for subsequent use).

In particular, known are devices for feeding yarns of the type able to feed yarns (including metal wires) or (textile/technical) yarns at constant tension. The device operates according to the known closed-loop control principle, which is implemented by the known constant-tension yarn feeder. The method of control ensures that the yarn or wire is regularly fed under constant tension irrespective of the feed speed of the yarn and irrespective of variations in the tension of the yarn at the introduction port of the constant tension yarn feeder; all this, whether the variation in tension is due to the gradual emptying of the yarn bobbin or whether such variation is due to tears or additional tension produced by the irregular unwinding of the yarn.

Known constant tension yarn feeders of the above-mentioned type are targets in the name of the same applicant, for example EP 1492911; this prior art document describes a feeder comprising: a tension sensor; an actuator or motor acting on the feed wheel or pulley; and a control unit (or electronic device) able to evaluate the tension of the yarn measured by the above-mentioned sensor by comparing it with a desired working tension (or set point). On the basis of this comparison, the control unit acts on the motor to modify or keep constant the tension of the yarn fed to the textile machine (for producing the manufactured product or processing the yarn itself) by braking or feeding the yarn on a pulley connected to the motor.

Also known are devices and systems (and methods of implementing these devices or systems) for feeding yarn to textile machines in the following manner: this way is discontinuous or, according to it, the yarn moves with at least one first condition and at least one second condition for feeding or drawing, different from each other, by the textile machine. These different feed conditions always follow one another.

As an example, a constant tension yarn feeder is known, which comprises: devices capable of measuring in real time the tension of the yarn being controlled, such as load cells; a pulley on which the yarn can be wound in one or more turns; an electric motor that drives the pulley to rotate; and control electronics which regulate the rotation speed of the motor and therefore of the pulley as a function of the measured tension of the yarn, so as to keep the measured tension in correspondence with a predetermined and programmable value, which may be a function of the operating phase of the textile machine. The rotation of the motor is generally controlled in two directions, the first to feed the yarn to the machine and the second to recover the yarn from the machine during the stop or reversal phase, in order to prevent the yarn from becoming loose and to keep it at the desired tension all the time.

With this type of feeder, the yarn can be picked up directly from the device from the bobbin and wound onto a pulley. Obviously, in order to ensure a high quality of constant controlled tension, there must be no slippage between the yarn and the pulley; only in this case can the control electronics actually calculate exactly the speed to be set for the motor associated with the pulley in order to keep the tension at the desired value.

In applications where the take-up ratio of the machine is constant or without large discontinuities, this type of feeder device is capable of keeping the measured tension constant as the feeding conditions (variable yarn tension at the feeder intake, variation in the feeding speed, etc.) vary. Obviously, in such working conditions, the feeder is able to perfectly keep the measured tension in line with the set value, thanks to the absence of slipping, and at the same time to accurately measure the amount of yarn feed, another essential parameter for ensuring the quality of the finished product.

However, known solutions of the above type do present operational limits when the take-up rate of the textile machine changes suddenly. In this type of application, the speed at which the yarn is drawn by the textile machine varies very rapidly, for example when following the selection of a needle in the machine; in this case, if the motor that rotates the pulley does not have the necessary output power to follow these pull variations, tension peaks occur on the yarn when the pull increases and slack occurs when the pull decreases.

These defects in the tension control (peaks and slacks) can lead to quality problems of the garments produced (presence of stop marks due to incorrect tensions in the production process) or to yarn breakage (due to tension peaks) or to yarn falling from the operating devices of the textile machine (for example needles) (due to slacks).

The problem is clearly that the greater the tension, the less elastic the yarn, which helps compensate for the lack of power in the motor response.

Various solutions for this type of problem are known, for example from EP 2262940 in the name of the same applicant, a feeder system comprising a compensator device connected upstream of the feeding device (of the type described above) and helping to overcome the above-mentioned limitations by acting together with the yarn. After the yarn has been wound onto the pulley of the feeder, the system requires routing the yarn to the movable arm of the compensator device and then redirecting it to the load cell of the feeder. In this way, the compensator device is located within the control cycle (tension measured with respect to the speed of the feed pulley) to ensure that the yarn tension remains constant as a function of the position of the movable arm.

In other words, according to the above-mentioned prior art document, the movable arm acts as a compensator device between the pulley (on which the yarn is deposited) and the tension detection device (load cell), and is able to compensate for variations in the following conditions: in this condition, the yarn is fed or drawn as it passes through each condition in which it is drawn by the textile machine. This is to maintain the yarn tension at a constant predetermined value even if there is any variation in the conditions under which the yarn is fed to the textile machine.

The movable arm of the known solutions is configured with a spring (for example a helical spring) whose terminal portion comprises an eyelet (for example a ceramic eyelet) for the passage of the yarn, to allow the arm to perform its compensation function.

When using the compensator device, the operator adjusts (manually or electronically) the spring force so that the end portion of the compensator device, through which the yarn extends during the working phase, is located on average in the center of the angular working sector. In this way, if the pulling of the textile machine varies, one of the following situations can occur:

during the period when the pulley motor cannot follow (compensate) the pull-up sharp increase due to its limited power, the compensation arm will drop, allowing the motor time to accelerate and reduce the tension peak leaving the feeder;

during the period when the motor cannot follow the drastic reduction of the pulling due to its limited power, the compensation arm will rise, allowing the motor time to slow down and reducing the tension slack leaving the feeder.

It is clear that the ability to compensate for tension peaks and yarn slack is closely related to the dynamics of the system (spring force) and the amplitude of the angular sector in which the arm can move.

It should also be noted that the above-mentioned prior art document provides the possibility of measuring the position of the compensating arm, which the control electronics of the feeder uses to increase or decrease the speed of the pulley, and the possibility of adjusting the force of the spring by means of an electronic actuator, so that the spring works automatically without the operator needing to adjust the force manually.

This known solution, although functioning very well, still has limitations, as described below.

The compensator device of the known system operates in practice as a balancer and the force of the spring is adjusted manually or automatically to ensure that the force of the spring is able to compensate the tension in the feed yarn, keeping its end portion in the centre of the angular sector of movement. The lighter the spring (by weight), the more force will be correctly calculated and the more the responsiveness of the system will be increased. However, it is clear that the force of the spring is also associated with an operating tension limit within which the device can operate effectively.

For example, if a spring is calibrated for a particular application (e.g., 10g) for medium and high tension, the force of the spring must be calculated accordingly; conversely, when the working tension is low, the selected force will constitute the operational limit of the device.

The known compensator devices therefore have the great limitation that the spring must be dimensioned according to the desired working tension, which makes the system inflexible, or that the spring must be dimensioned differently by the operator, or that the entire compensator device must be dimensioned differently as the working tension changes, which is of course not always possible.

In addition, since the end portion of the compensation arm is part of the spring, the compensation arm is also subject to bending due to the force of the yarn, which makes the reading of the position of the compensation arm inaccurate and therefore difficult to use as a predictive signal to anticipate any compensating action performed by the device to modify the conditions under which the yarn is pulled; it is also difficult to maintain the spring in a particular position because the spring is flexible.

Finally, the compensation capacity, in particular the compensation capacity during the relaxation phase, is closely related to the length of the arm and the amplitude of the angular sector; therefore, such compensation capability is limited.

US 4752044 relates to a yarn feeding device with electronic tension control. The device comprises a housing on one side of which is positioned a rotating device on which is wound a yarn directed towards the textile machine, said yarn having previously acted upon with braking means associated with such a housing. At the outlet from the rotating device, the yarn passes through a fixed eyelet and then through an eyelet at the end of a movable guide arm forming an integral part of the known yarn feeder apparatus; at the outlet of the eye of the movable guide arm, the yarn acts together with another fixed eye before leaving the device.

When the yarn feed slows down due to the variations of the yarn drawn by the textile machine, the yarn guide arm is intended to form a reserve of yarn F on the outlet side of the rotating device and, therefore, downstream of the rotating device.

The yarn guide arm may be attached directly to a permanent magnet dc electric motor contained in the housing of the device, or it may act together with a rod which in turn is an integral part of the device and driven within said housing by the electric motor. In both embodiments, the electro-optical signal sensor detects the angular position of the guide arm and emits the following signals: this signal represents the feed yarn tension and, at the same time, the angular position of this arm and therefore the size of the yarn reserve produced downstream of the rotating device.

The (direct current) electric motor forms an electromagnetically controlled sensor which exerts a carefully predetermined and adjustable control force on the guide arm. This force is equal to the tension exerted by the yarn on the eyelets of the guide arms.

The force can be adjusted by means of a potentiometer in an electric circuit comprising a power supply unit for powering the dc electric motor. In this circuit, a compensation signal is defined which is applied to the control input of the aforementioned power supply, said signal being set (and therefore having a constant value) so as to correspond to a specific yarn tension.

In this way, the power supply unit controls the direct current motor to define an equilibrium position of the guide arm which can be maintained when subjected to the force of the yarn

More specifically, under normal operating conditions, the guide arm occupies a certain equilibrium angular position between the two stop pins, between which the arm can only move angularly. The force exerted by the yarn through the eyelets attached to the arms is balanced by the force exerted by the dc motor on the rod or the arm itself.

If the yarn feed condition changes, for example if the textile machine reduces the use of yarn, the guide arm moves angularly with respect to the initial rest position, generating an electrical signal corresponding to the change in position by the above-mentioned sensor. The signal is transmitted to a device that controls the apparatus. The device acts on the feed of the actuator, which controls the rotating means to act on the feed rate of the yarn until the guide arm returns to a predetermined equilibrium position in which the tension of the yarn is compensated by a control force exerted by a lever acting on the aforementioned arm, generated by an electric motor connected to the lever, or the tension of the yarn is equal to the force generated directly on the movable arm by the motor, which acts together with the movable arm.

Thus, by means of the movement of the guide arm, the known solutions are able to detect a variation of the feeding condition of the yarn, which variation is compensated by a corresponding action of the rotating feeder device. In this solution, the guide arm is directly or indirectly subjected to the action of an electric motor whose function is merely to counteract the variation in the yarn tension in order to keep the guide arm in a rest position. However, the guide arm and the actuator acting directly or indirectly with it have an entirely passive function, which is merely the following function of the actuator of the rotating device: this action causes the arm to stay in the equilibrium position or to return to the equilibrium position after the arm has moved angularly between the fixed pins (attached to the housing of the device). Such guide arms are always subjected to a predetermined force and can only compensate for limited variations in the yarn tension due to limited movement between the fixed pins.

WO 2005/111287 describes a yarn feeder apparatus comprising a sensor capable of reading the tension of a yarn being fed to a textile machine and a rotary feed device controlled by an electric motor. The movement of the device is controlled by a microprocessor unit which regulates the speed of the device according to the tension of the yarn detected by a tension sensor. The sensor is located at the free end of the rigid arm which moves against the resistance element when the yarn changes its tension at the outlet of the rotary device and passes over an idle roller or pulley associated with the free end of the movable arm. The opposition to the movement of the arm can be achieved by means of a spring or carriage which moves along a track associated with the feeder device.

The rotating means and the movable rigid arm are integral parts of the known feeder device.

In the working condition, the yarn is wound at least once on the rotating means before passing through the pulley at the end of the rigid arm. The movement of the yarn causes the arm to rotate in a direction following the yarn feed direction and this rotation is counteracted by a counter-element (spring or carriage), the action being regulated by the operator. The tension sensor detects the yarn tension, compares the detected value with a fixed value, and then adjusts the speed of the rotating device to keep the yarn tension close to the desired value. The movement of the rigid arm prevents any sharp increase in yarn tension due to the backward movement, thus preventing yarn breakage.

Furthermore, the movement of the rigid arm is limited to a predetermined angular sector.

In both known solutions of the above two prior art documents, the device in US 4752044 or the device in WO 2005/111287 is an element incorporated into the compensation device and is not separable or can not be constructed independently. The result is a high complexity of implementation of the known solution, as well as a great difficulty and high cost in performing any maintenance work.

Methods and systems according to the background art of this document are described in WO 2013/064879 in the name of the applicant.

The above prior art document describes a metal wire feeder apparatus comprising: a body having a wire brake; one or more pulleys controlled by their respective motors on which the wire is wound; a wire passing through the compensator member and the tension sensor before reaching the operating machine. The control electronics are able to continuously measure the wire tension to match it to a predetermined value by a first control cycle acting on the electric motor and a second control cycle acting on the compensation member.

The compensator member also comprises a compensating arm having a free end that acts together with the wire and which in turn can rotate freely about a pin fixed on a bracket associated with the body. The arm can then be moved within the body of the predetermined angular sector by approaching or moving away from the tension sensor (defined by the load cell).

The compensation arm is associated with a spring which is connected on one side to a support fixed to the body of the apparatus and on the other side to the compensation arm by means of a movable carriage which is moved by means of an electric stepper motor by means of archimedes or headless screws.

Thus, the compensation arm is not directly connected to the electric motor, but the electric motor drives and moves the compensation arm by interposing other components, each of which has a respective inertia.

The compensation arm is associated with a position sensor connected to the control unit, which is therefore able to measure the position of the arm within a predetermined angular sector.

Thus, the compensation arm is able to oppose the sliding of the wire in a dynamic manner rather than in a static manner: the control unit may in fact vary the position of the carriage to which the spring is attached (acting on the electric motor), effecting a variation in the force exerted by the spring on the arm, and bringing the arm to the desired position within a predetermined angular sector. In this way, the compensation arm keeps the wire perfectly tensioned all the time on the load cell or tension sensor, in particular during the phases in which the wire is not fed to the textile machine.

The compensating arm also creates a reserve of metal wire from which the machine can extract it during unexpected speed variations.

The prior art document in question then describes a feeder device which is equipped, as an integral and inseparable component, with a compensating arm which can move freely within a predetermined angular sector.

The control system of the device knows the position of the arm and can define, by means of the electric motor and the spring system(s), the force to be applied according to the measured tension or the read position, closing two possible control cycles, a second cycle related to the tension (the first cycle being the one related to the motor connected to the pulley) and a possible second cycle for the position of the arm.

It should be noted, however, that the force applied to the arm is managed by a spring system and a movable carriage driven by an electric stepping motor for varying the fulcrum of the lever, and thus the force exerted by the lever on the wire.

Even in this prior art document, the problems indicated for the system described in EP 2262940 above still apply.

In fact, the ability to compensate for tension peaks and slacks of the wire of the device, which is the object of WO 2013/064879, is closely related to the dynamics of the system (spring force, moving carriage and motor) and the amplitude with which the compensating arm can move in the angular sector.

Furthermore, even in the prior art document, the compensating arm operates in practice as a balancer, and the force of the spring is automatically adjusted so that it can compensate the tension of the feeding wire, keeping the end portion of the compensating arm in the centre of the angular sector of movement.

Finally, the compensation capacity, in particular of the relaxation phase, is closely linked to the length of the compensation arm and to the amplitude of the angular sector; this compensation capability is therefore limited.

In addition, the known feeder device incorporates a compensator member inseparably. The result is a heavy component with insignificant size.

It is an object of the present invention to provide an improved method and system for controlling the feeding of a discontinuous feed yarn, comprising a yarn feeder associated with a device for compensating for variations in the yarn pulled by a textile machine.

In particular, the object of the present invention is to provide a system of the above-mentioned type with a compensator device to be inserted in a control loop (tension measured with respect to the speed of the feeding pulley) when feeding the yarn to the textile machine, overcoming the limitations of the existing solutions.

Another object is to provide a method of the above-mentioned type which can actively or dynamically compensate for any variation in the tension to which the yarn is subjected during the following process: such feeding is interrupted during the aforementioned discontinuous process of feeding the yarn to the textile machine, during the phase of feeding the yarn to the textile machine and during the phase of moving the yarn back from the textile machine, during both phases.

A further object of the present invention is to provide a self-contained compensator device, suitable for use in a system of the above-mentioned type, which does not change its dynamic characteristics with respect to the set working tension, thereby making the device flexible and easy to use.

Another object is to provide a compensator apparatus of the above-mentioned type which allows to accurately measure the position of the compensating device and which can also operate in a predictive manner when the yarn is subjected to tension variations at the beginning of the different phases of the discontinuous process of feeding to the textile machine.

A further object is to provide a compact compensator device which can also be applied as an additional element to a feeder device, which enables the system to which it belongs to recover more yarn during the relaxation or reversal phases of the textile machine than what is possible with the known systems.

These and other objects, which will be apparent to those skilled in the art, are achieved by a method, a feeder system and a compensator apparatus according to the present invention.

For a better understanding of the invention, by way of non-limiting example only, the following drawings are attached, in which:

figure 1 shows a front view of a compensator device according to the invention associated with a known feeder device for controlling the tension of a yarn fed to a textile machine;

FIG. 2 shows a side view of the apparatus shown in FIG. 1;

figure 3 shows a perspective view of a compensator apparatus according to the invention and the feeder apparatus of figure 1;

FIG. 4 illustrates a front perspective view of a compensator apparatus according to the present invention;

FIG. 5 shows a side view of a compensator apparatus according to the invention;

figures 6 to 8 show the compensator apparatus in three different positions of use, viewed from above;

figure 9 shows a view from below of a compensator apparatus according to the invention; and

10A-10C illustrate different block diagrams relating to the use of a system according to the invention;

fig. 11A to 11C show the tension profile of a yarn guided to a textile machine in the following cases, respectively: the case where the device targeted by the invention does not operate (fig. 11A), and both the case where the system according to the invention operates in passive-dynamic mode (fig. 11B) and in active-predictive mode (fig. 11C).

With reference to the above-mentioned figures, in which corresponding parts have the same reference numerals, and in particular with reference to figure 1, a compensator device according to the invention is generally indicated with 1 and is associated with (or on the side of) an end 2A of a feeder device or a simple feeder 2, known per se, to feed a yarn F (shown in broken lines in figure 1) to a textile machine T with constant tension. The yarn F may also be a metal wire and may be delivered to an operating machine such as a winder. In contrast to the feeder 2, the device 1 is a complete and easily identifiable element from the point of view of construction and use.

The feeder 2 has: a tension sensor 3, a pulley 4 (or equivalent yarn storage means) driven by its own electric motor (not shown), and a control unit or electronic device 60, the control unit or electronic device 60 preferably having a microprocessor known per se (see fig. 10A to 10C). The control unit or electronic device is able to evaluate the tension in the yarn detected by the sensor 3 as it is fed to the textile machine, compare it with a predetermined value (or set point value), and check and regulate the tension of the yarn (if it differs from the desired value) which is constantly acting on the electric motor and therefore on the pulley 4. This feeder 2, with its components 3, 4, is of known type and operating manner and will therefore not be described further.

As mentioned above, the feeder allows to feed the yarn with constant tension to a textile machine, which is a production unit of the finished product or a machine that processes the yarn.

According to the invention, device 1 and feeder 2 define a feed system for yarn F.

The compensator device 1 according to the invention is capable of acting with the yarn after it has passed the pulley 4. The compensator device is thus within the yarn tension control loop, as can be observed from fig. 1 and is clearer from the description of the method according to the invention. Thanks to the invention, it is possible to improve the dynamic performance of the feeder system, so that it is able to immediately compensate for sudden changes in yarn take-up (positive and negative), thus enabling the pulley motor to change to a new speed for feeding the yarn according to new take-up requirements, without generating positive or negative tension peaks in the final yarn tension.

The presence of the compensator device 1 in the control cycle always ensures that the tension of the yarn leaving the feeder 2 is always the same as the set value.

Compensator 1 is a stand-alone device compared to feeder 2 and comprises an electric motor 8, electric motor 8 being for example a dc brush motor, preferably with very low inertia to increase power. In the embodiment of the invention provided by way of example, the motor 8 directly drives a drive shaft having two portions projecting from opposite sides of the motor itself. In the figures, a first portion of the drive shaft is indicated with 7 (see fig. 7 to 9), and a second portion, indicated with 10, can be observed in fig. 9; the motor is also inserted into the body 11 of the device. The rigid arm 13 (and thus to the drive shaft itself) is mechanically attached to the first part of the drive shaft. At the ends 14 of the arms 13 there is an annular body 16 (or one of other shapes) of ceramic (or other material) around which the yarn is passed.

As mentioned, the electric motor 8 preferably has a very low inertia to allow the arm 13 to move rapidly under the force of the yarn and therefore to compensate for this movement rapidly without causing tension peaks in the yarn itself.

However, in the case of motors with very low inertia (preferred) and limited inertia, if drawn by the yarn F, the arm 13 can rotate freely (rotate the motor) about the axis M (or the drive shaft axis); in each case, the arm has a zero or initial rest position (as observed for example in fig. 6) which is adopted when the yarn F is drawn by the textile machine without tension variation and without interruption. Other compensating positions of the arm are also possible, as described below.

The assembly of arm 13 and motor 8 (i.e. essentially device 1) can be operated in two different modes: passive-dynamic mode or active-predictive mode.

In passive-dynamic mode, the motor causes the arm 13 (attached to the drive shaft) to be pulled by the yarn and to move from its rest position, also causing the rotation of the motor itself. However, the motor acts after said movement to return the arm 13 to the rest position. In this mode or mode of operation, the motor operates essentially as a "dynamic" spring whose force (which acts on the arm 13) can be programmed by programming and/or controlling the motor torque.

However, this force is not predetermined and fixed (as in the solution in US 4752044), but can be varied, i.e. at various stages of the production process, it can be automatically adjusted to adapt to variations in the yarn tension set value, to always keep the arm in its predetermined position, regardless of the set yarn operating tension for each particular stage in the production of the finished product. This enables the motor 8 to oppose and oppose the force that moved the arm 13 (to which the motor is always directly connected) away from the rest position, thereby holding the arm in its rest position (for example the position at "3 o' clock" in fig. 6).

The opposite force variability or the action of the motor on the arm 13 will be described below.

In the active-predictive mode, the motor 8 can act in advance (in the "predictive" mode) as soon as the motor 8 detects a variation in the yarn tension (detected by the sensor 3) due to a variation in the operating phase of the machine. In this case, the motor 8 moves the arm 13 carried by the drive shaft to a compensation position capable of compensating for the variations in tension: if the tension variation tends to increase, the motor 8 moves the arm to a compensation position at "6 o 'clock" in figure 7, if this variation tends to decrease in the yarn tension (because the textile machine has stopped or slowed yarn drawing), the motor will move the arm 13 to a compensation position at "12 o' clock" in figure 8. This allows the yarn tension to be kept constant, regardless of the operating and production phases of the textile machine T.

Fig. 11A to 11C show tension curves in the following cases: a situation in which the motor-arm assembly or device 1 is disabled (fig. 11A), a situation in which the motor-arm assembly or device 1 is in a passive-dynamic mode (fig. 11B), or a situation in which the motor-arm assembly or device 1 is in an active-predictive mode (fig. 11C).

In the figure, curves or lines F, K, W and Y define respectively the set yarn tension (curve F during the production operation), the measured yarn tension (curve K), the set point position for the arm 13 (curve W) and the actual position of the arm 13 (curve Y). In the figure, time is plotted on the abscissa and the ordinate is plotted for the measured tensions F and K and the position values for W and Y.

As can be seen by comparing the figures, the measured yarn tension has a distinct peak and variation when the device 1 is disabled compared to the other cases in fig. 11B, 11C. As can also be seen by comparing fig. 11B and 11C, the variation of the yarn tension is more limited when the device 1 is active in the active-predictive mode. Finally, in fig. 11C it can be seen that the rest position of the arm 13 (curve W) is not predetermined, but follows the variations in the yarn tension; this rest position is also "followed" by the "current" position of the arm during the compensation performed by the device 1.

The second portion 10 of the drive shaft supports a magnet 18, which magnet 18, together with the arm 13 associated with the motor 8, is free to rotate about its axis M within a specific circular sector (causing the drive shaft to rotate). Alternatively, the assembly comprising the arm 13 and the magnet 18 can rotate freely, forming a complete cycle around the rotation axis M (axis of the drive shaft); in other words, both the arm 13 and the magnet 18 are splined to the drive shaft so that both rotate freely or within an angular sector about the axis M in the same way. This makes it possible to immediately know the position of the arm 13 by detecting the position of the magnet.

For this purpose, around the magnet there is a position detector 19, for example one or more linear hall sensors 20, which position detector 19 is able to generate a position signal which is addressed to, for example, a control unit 70 of the compensator device 1. Thanks to the hall sensor data, this unit 70 is able to convert the rotation of the motor into two sinusoids (sine and cosine) offset by 90 °, from which it is possible to obtain the absolute position of the shaft and, therefore, of the arm 13 acting with the yarn, the arm 13 being rigidly attached to the shaft and to the magnet 18 in real time.

In one embodiment, the control unit also advantageously comprises (known per se) a system to drive the electric motor in order to control the rotation speed and the applied torque of the electric motor.

Preferably, provision is also made for a real-time data exchange between the control electronics 60 of the feeder 2 and the control unit 70 of the compensator device 1, in order to be able to set the required torque for the motor of this device 1 and then to control the motor to rotate and read the motor position (and therefore the position of the arm 13) in a direct and instantaneous manner. The torque setting is dynamic and not fixed, since it depends on the set yarn tension or the yarn tension detected by the sensor 3.

The information exchange may be performed in one of the following ways: through any serial bus, through digital or PWM signals, or through analog signals.

It is therefore clear that the feeder 2, through its control electronics, which functions together with said compensator device 1, is able to know in real time the position of the arm 13 and to adjust the torque/displacement/speed exerted on the motor of the compensator device 1 in a safe and instantaneous manner. This is due to the direct connection between the drive shaft and the arm or due to the direct action of the motor on the arm.

By suitably managing the received position signal of the arm 13 and suitably controlling the motor used on the arm, the feeder system for yarns F according to the invention is therefore able to close the second control cycle for the position of the arm 13 in an almost instantaneous manner as a function of the set tension, so as to keep the arm in a desired position, for example in its central position ("3 o' clock"). This is to compensate for the movement of the yarn and the variations in its tension associated with the various operating phases of the textile machine.

Referring to fig. 10A, 10B, the system may be implemented in different ways:

1. the compensator device 1 has its own control unit 70, which control unit 70 is intended to receive from the control electronics 60 of the feeder 2a rest position reference (represented by block 80 in figures 10A and 10B), which is the position the arm must maintain when the tension of the yarn F is set or detected to change. The control unit 70 functions with means (magnet 18) for measuring the position of the arm 13 and for driving the motor 8 (blocks 81 and 82). The control unit thus closes the control cycle for the position of the arm 13.

2. Alternatively and preferably, the control electronics 60 of the feeder 2 receive data from the magnet 18 relating to the position of the arm 13 and thus set a torque value for the motor 8 to close the control cycle for the arm position (based on the set or detected yarn tension). In this case, the drive means for the motor 8 can be located in the control unit 70 of the compensator device 1, to which the feeder transmits a reference, or in the electronics 60 of the feeder 2 (as described below). This solution is preferred because the control electronics 60 of the feeder 2 not only knows the position of the arm, but also directly the measured yarn tension (the yarn being connected to the tension sensor 3), which can then be used to optimize the performance of the system. For example, if this electronic device detects an increase in the tension of the yarn due to a sudden demand for yarn by the textile machine T, the electronic device may decide to automatically change the position setpoint for the arm 13, for example by moving the arm from "3 o 'clock" to "6 o' clock". This is consistent with the above-noted active-predictive mode of operation of the motor 8 and arm 13 assembly.

This function also allows a further reduction of the peak tension, since not only the low inertia of the motor 8 is utilized, but also the power of the motor 8 is utilized to compensate for this situation. Obviously, the same applies to the phase of sudden slowing down of the pulling. Indeed, all of this can be observed from FIG. 11C and the previously mentioned comparison with FIG. 11B.

By continuously reading the position of the arm 13 (depending on the tension detected in the yarn F), and by suitably controlling the torque of the motor acting with the arm 13, the electronics of the feeder system (i.e. the control unit 70 of the compensator device 1 or the control electronics 60 of the feeder 2 as described above) are able to maintain the position of the compensating arm 13 at a desired value. By applying a force directly to the arm equal and opposite to the feed tension of the yarn by means of the drive shaft, this torque value will therefore allow the arm 13 to remain balanced in its rest position, for example at 3 o' clock. This does not have any delay in the action of the arm 13, as occurs in the solution of WO 2013/064879.

Thus, an increase or decrease in the yarn tension will cause the arm 13 to move from its equilibrium position, always keeping the yarn at the set working tension, for example as indicated below:

a) in the event that an increase in the set yarn tension is required during processing, the arm 13 obviously tends to fall (moving towards the "6 o' clock" position in fig. 7) and the system electronics reading this change in position (i.e. the control unit 70 of the apparatus 1 or the control electronics 60 of the feeder 2) will calculate a new torque to be applied to the motor 8 to return the arm 13 to the rest position;

b) in the event that a reduction in the set yarn tension is required during processing, the arm 13 obviously tends to rise (moving towards the "12 o' clock" position in figure 8) and the control unit or electronics of the feeder reading this change in position will calculate a new torque to be applied to the motor 8 to return the arm 13 to the rest position.

Since the arm 13 is attached to the drive shaft, the feeder electronics will thus be able to automatically, quickly and accurately control the position of the compensating arm 13, enabling the operator to modify the working tension at will during the process, for example to create a tension gradient (such as a gradient pressure of a medical sock or the like) during the production cycle for the finished product. Each change in tension involves a change in the motor torque applied to the arm 13, the arm 13 will always adopt a rest position (for example "3 o' clock"), or return to a rest position, so as to keep constant the "current" tension of the yarn, or the tension drawn by the yarn during the particular feed phase required by the particular production phase.

In other words, the feeder system is provided with a control unit (device 1 or feeder 2) incorporating, for example, a microprocessor, which controls the operation of a motor that directly drives the arm 13. However, when the drawing or feeding conditions of the textile machine vary with a continuous variation of the tension of the yarn through the annular body 16 supported by the arm 13, this arm, and the drive shaft connected to it, can first move freely about the axis M (causing the motor to rotate).

Any change in the position of the arm 13 (relative to a predetermined reference or rest position, e.g. "3 o' clock") is detected by the control unit of the feeder system by means of a signal from the position detection device 19. These data are provided to an electronic control unit (60, 70) for the feeder system to close the control loop.

In particular, control unit 70 of device 1 is able to detect how much (the angle) arm 13 has moved from the reference position, and, on the basis of this value, control electronics 60 of feeder 2 can monitor, vary and control the supply of power to the motor of pulley 4, so that the motor varies its rotational speed to compensate for the angular movement of arm 13 with respect to the reference position. In this way, feeder 2 uses the information about the position of arm 13 to predict the change (acceleration/deceleration of pulley 4), further improving the quality of the conveying tension. This is consistent with the "active-predictive" mode of operation described above.

Also in this case (as in the case of EP 2262940) the compensator device 1 will therefore act as a "balancer", and the electronics of the feeder system will calculate in real time the torque to be applied to the motor 8 acting together with the arm 13, thereby keeping the arm 13 always in a balanced position in a fully automatic manner. Depending on the "current" tension of the yarn F (obviously in order to maintain a predetermined tension).

Controlling the position of the arm 13 in this way will also produce a compensating effect on the delivery tension, which will result in a complete elimination or drastic reduction of the tension peaks and slacks of the yarn itself. In fact, when the textile machine T suddenly increases the demand for yarn F and the motor power driving pulley 4 is insufficient to compensate for this variation, arm 13 tends to descend (moving towards the "6 o' clock" position) to increase the quantity of yarn F fed into machine T; until the motor of pulley 4 reaches the necessary rotation speed to eliminate or reduce the tension peaks. At this point, the arm will automatically return to its initial or rest position.

Conversely, when the textile machine T suddenly reduces the demand for yarn F and the motor power driving pulley 4 is insufficient to compensate for this variation, arm 13 tends to rise (moving towards the "12 o' clock" position in fig. 8) to reduce the amount of yarn F fed into machine T; until the motor of pulley 4 reaches the necessary rotation speed to eliminate or reduce the yarn slack. At this point, the arm will automatically return to its initial or rest position (fig. 6).

In its first embodiment, the rest position of the arm 13 is within the range of motion of the compensation means or arm 13 with two extreme positions (i.e. 6 o 'clock and 12 o' clock).

Also, knowing the position of compensating arm 13 precisely and in real time, the electronics of feeder 2 can use this information to accelerate or decelerate the rotation of pulley 4 to shorten the time to stabilize to the new ideal speed, so as to obtain and maintain a constant preset value of the tension of yarn F, further limiting the amplitude of the tension peaks or slackening of yarn F.

Also, knowing precisely and in real time the position of the compensating arm 13 and the value of the tension measured by the sensor 3 during transients (pulling variations), the feeding system can vary the driving force of the motor 8 acting with the arm 13 to reduce more the variations in the delivery tension of the feeder 2; for example:

i) during the sudden acceleration phase, the arm 13 will tend to fall (moving towards the "6 o' clock" compensation position in fig. 7) and the measured yarn tension will tend to rise; in this case, the electronics of the feeder system may decide to:

1) interrupting or reducing the action of the closing of the cycle controlling the position of the arm 13, so that the yarn can lower the arm 13 until the yarn tension is within the predetermined limit, thus using this interval to move the arm from 3 o 'clock to 6 o' clock as a stock of the yarn F to be fed;

2) the working set point of the arm 13 is automatically set at a lower position to supply more yarn F to the textile machine T until a critical condition is overcome.

ii) during the sudden deceleration phase, the arm 13 will tend to rise (moving towards the "12 o' clock" compensation position in fig. 8) and the measured tension will tend to fall; in this case, the feeder system may decide to:

1) the closing of the position control cycle is interrupted or its action is reduced so that the arm 13 can recover the yarn F until the yarn tension is within the predetermined limit, thus using this interval to move the arm from 3 o 'clock to 12 o' clock to recover the excess feed yarn.

2) The working set point or rest position of the arm 13 is automatically set at a higher position to supply less yarn F to the textile machine T until a critical condition is overcome.

The set point or reference value for the position control cycle of the compensating arm 13, heretofore considered to be a value of for example "3 o' clock" (fig. 6), can instead be variable and suitably dynamically managed by the feeder electronics, in order to be provided for example to a possible subsequent feeding phase; for example, during the phase in which the yarn is slowed down by means of the textile machine and then stopped, the setpoint can automatically reach the 12 o' clock position, so that there is more yarn F stock to feed the next restart acceleration, further reducing the next peak.

In another embodiment of the invention (already included in the figures), there is also a drum or drum 26 associated with the compensation arm 13, on which drum or drum 26 the yarn is deposited during the recovery phase, thus increasing the quantity of yarn F stored, since the amplitude of the angular rotation sector has been increased, in which case the compensation arm will no longer be constrained between 6 and 12 o' clock, but can rotate freely about the rotation axis M.

The drum on which the yarn is deposited can be attached to the arm 13 or freely rotate on bearings that allow it to rotate independently. The diameter of the drum determines the maximum amount of yarn F that can be recovered from the device 1/feeder 2 system. The drum portions therefore have different sizes depending on the number of yarns F that need to be recovered on the drum portion. The drum may be cylindrical, semi-cylindrical or of variable cross-sectional shape.

The compensator device can operate without a mechanical stop preventing its rotation beyond the arc of 6 to 12 o' clock, allowing the arm 13 to rotate about the axis without restriction during the recovery phase. In this case, the arm 13 is free to deposit on the drum 16 a greater quantity of yarn stored during the recovery phase, which will then be fed back to the textile machine on the next restart.

This results in a double "reservoir" of yarn, i.e. a drum 26 in addition to the pulley 4.

Thanks to the invention, a single "system" can work at even very different feed tensions, without the operator having to take any action. This system is able to compensate for sudden changes in feed without producing tension peaks or slackening of the yarn and to recover, to a small extent, a greater quantity of yarn F than in the solutions previously described in the state of the art.

Various embodiments of the present invention have been described. Other embodiments are of course possible. For example, the annular ceramic body on the arm 13 may be replaced by a body made of any other material having sliding properties suitable for the application. In addition, the use of a dc motor with brushes is described herein, but it is apparent that any type of electric motor or actuator (brushless, stepper, etc.) as well as pneumatic motor or actuator may be used.

The use of an encoder with a hall sensor to detect rotation of the drive shaft has been described, but any encoder commercially available may be used, or the hall sensor may be incorporated into the motor; in this case, it is not necessary to protrude the drive shaft from both side portions of the motor.

In addition, the arm 13 is rigid, although it may have its own minimum flexibility to further dampen the compensation effect, this flexibility being due to the material of manufacture or the cross-section of the arm. Further, the compensating arm is described as rotating, but it may be replaced by an arm following linear motion that moves longitudinally through positions equivalent to 6 o ' clock, 3 o ' clock, and 12 o ' clock using a linear actuator or motor.

Finally, the presence of a control unit for the device 1 has been described, which functions together with the control electronics for the feeder 2. Obviously, this control unit may be a control unit for the feeder 2 (that is to say it may be part of the control electronics of the feeder) and automatically functions when the body 11 of the device 1 is attached to the feeder 2, automatically recognizing the presence of the device 1 (the presence of the body 11 being detected by a suitable connector, not shown, by which the control unit functions with the motor of the device 1 and with the encoder or position sensor means for the drive shaft associated with the arm 13). This solution is shown in fig. 10C.

The invention is not only suitable for feeding textile yarns, but also for feeding metal wires.

Such modifications are also to be considered as included within the scope of the invention as defined by the appended claims.

Claims

1. Method for feeding a yarn (F) comprising metal wires to a processing machine with constant tension, said feeding being carried out in a discontinuous manner, i.e. with a series of stages in which the yarn (F) is moved with at least a first condition and at least a second condition of feeding or drawing by the processing machine that are different from each other, said conditions following each other in time, said feeding being performed by a yarn feeder apparatus (2), said yarn feeder apparatus (2) having: a tension detection device (3); a yarn accumulating device (4), said yarn accumulating device (4) being driven by its own electric motor; and a control device (60), said control device (60) being connected to said tension detection means (3) and to said accumulation means (4) and being able to act on said accumulation means (4) according to a tension value obtained from said tension detection means (3), a compensator apparatus (1) being provided in association with said feeder apparatus (2), said compensator apparatus (1) acting with said yarn (F) coming from said accumulation means (4) before acting with said tension detection means (3), said compensator apparatus (1) being able to compensate for a change in the feeding or drawing condition of said yarn (F) when transitioning between each first feeding or drawing condition and each second feeding or drawing condition following said first feeding or drawing condition, this enabling said control device (60) for said feeder apparatus to act on said accumulation means (4) to change said change The deposit means (4) acting on the yarn and keeping the value of the tension detected by the tension detection means (3) constant and equal to a set value over a period of time, the constant tension being maintained also during the phase of variation of the feeding conditions due to the interaction between the yarn and the compensator apparatus (1), the compensator apparatus (1) comprising a movable compensation means (13) supporting a body (16), the movable compensation means (13) being able to act together with the yarn (F) at one free end, being able to move from a predetermined rest position in the feeding direction of the yarn (F) when the yarn passes from a less drawn condition to a more drawn condition, but when the yarn (F) passes from a more drawn condition to a less drawn condition, -moving in opposite directions, -the movable compensation means (13) returning to the rest position at the end of such a drawing variation, characterised in that it is provided to control the movement of the movable compensation means (13) by means of a corresponding first electric motor (8) of the movable compensation means (13) itself, the first electric motor (8) being directly and rigidly attached to the movable compensation means (13) and being able to directly control the movement of the movable compensation means (13), -the movable compensation means (13) being controlled according to the tension set or detected by the yarn (F) and the position measured during each stage of the yarn feeding to the processing machine, -the movable compensation means (13) being rigid.

2. Method according to claim 1, characterized in that the movable compensation means (13) and the first electric motor (8) which directly and strictly controls it in motion are operated in a passive-dynamic mode, the movable compensation means (13) being able to move freely with the first electric motor (8) under the action of the force of the yarn (F) but after such movement to return to the rest position by means of the first electric motor (8), the first electric motor (8) generating a torque when the yarn is fed to the processing machine which is able to keep the movable compensation means (13) for the yarn (F) in the rest position.

3. Method according to claim 1, characterized in that said movable compensation means (13) and the relative first electric motor (8) controlling it in motion are operated in an active-predictive mode, said first electric motor (8) moving said movable compensation means (13) from said rest position to a compensation position in correspondence of said tension variation of the yarn (F) once detected.

4. Method according to claim 1, characterized in that a continuous control of the first electric motor (8) of the compensator apparatus is provided by an electronic control unit connected directly or indirectly to the tension detection means (3).

5. Method according to claim 1, characterized in that the movable compensation means (13) is arranged to rotate around a fixed axis (M) of a drive shaft, thereby rotating the first electric motor (8) rigidly attached to the movable compensation means (13) or moving the movable compensation means (13) along the compensator apparatus (1).

6. Method according to claim 1, characterized in that provision is made for depositing a yarn (F) on the compensator apparatus (1) in addition to depositing a yarn on the depositing device (4) of the feeder apparatus (2).

7. A method according to claim 5, characterized in that the movement of the movable compensation means (13) is limited or not limited in angle.

8. System for feeding a yarn (F) comprising a metal wire to a processing machine with constant tension, said feeding being carried out in a discontinuous manner, i.e. with a series of stages in which the yarn (F) is moved with at least a first condition and at least a second condition of feeding or drawing by the processing machine different from each other, said conditions following each other in time, operating according to the method of claim 1 and comprising a feeder device (2) for the yarn, said feeder device (2) having: a tension detection device (3); a yarn accumulating device (4), said yarn accumulating device (4) being driven by its own electric motor; and a control device (60), said control device (60) being connected to said tension detection device (3) and to said storage device (4) and being able to act on said storage device (4) according to the tension obtained from said tension detection device (3); -a compensator device (1) is provided associated with the feeder device (2), said compensator device (1) acting with the yarn (F) leaving the accumulation means (4) before acting with the tension detection means (3), said compensator device being able to compensate for variations in the feeding or pulling conditions for the yarn (F) when transitioning between each first feeding or pulling condition and a second feeding or pulling condition following the first feeding or pulling condition, which enables the control means (60) for the feeder device to act on the accumulation means (4) to vary the effect of the control means (60) and the accumulation means (4) on the yarn and to keep the value of the tension detected by the tension detection means (3) constant and equal to a set value over a period of time, said constant tension being maintained even during the phase of variation of the feed conditions due to the interaction between the yarn and the compensator apparatus (1), the compensator apparatus (1) comprising a movable compensation device (13), the movable compensation device (13) being movable from a predetermined rest position in the feed direction for the yarn (F) when the yarn passes from a condition of less drawing to a condition of more drawing by the processing machine, but the movable compensation device (13) being movable in the opposite direction when the yarn (F) passes from a condition of more drawing to a condition of less drawing, the movable compensation device (13) returning to the rest position at the end of such a drawing variation, characterized in that the movable compensation device (13) is a rigid arm carrying a terminal body (16) and being able to act together with the yarn (F), the rigid arm is directly and rigidly connected to its own first electric motor (8), the first electric motor (8) directly controlling the rigid arm in motion according to the tension set or detected in the yarn (F), the rigid arm being located between the yarn accumulating device (4) and the tension detecting device (3), but separate from the tension detecting device (3).

9. A system according to claim 8, characterized in that the rest position of the movable compensation means (13) is within a range of motion of the movable compensation means having two limit positions, or the rest position of the movable compensation means (13) is defined within a circular path of the movable compensation means about an axis (M), the circular path being not limited in angle.

10. System according to claim 8, characterized in that position detection means (19) are provided to determine the spatial position of the rigid arm, said position detection means (19) being associated with a drive shaft of the first electric motor (8) which also rigidly carries the rigid arm.

11. System according to claim 10, characterized in that an electronic control unit is provided for the first electric motor (8) of the compensator apparatus (1), connected to the position detection means (19) and able to detect by means of the position detection means (19) the movement of the movable compensation means (13) with respect to the predetermined rest position and by means of the control of the first electric motor (8) the movement of returning the movable compensation means (13) to the predetermined rest position, the movable compensation means (13) being rigidly and directly attached to the first electric motor (8), the electronic control unit being directly or indirectly connected to the tension detection means (3), when the yarn (F) is fed to the processing machine, the electronic control unit controls the first electric motor (8) as a function of the detected tension in the yarn (F).

12. System according to claim 11, characterized in that the electronic control unit is associated with the compensator apparatus (1) and is connected to the control device of the feeder apparatus (2) or is part of the control device for the feeder apparatus (2).

13. System according to claim 8, characterized in that the compensator device (1) is a separate component from the feeder device (2), the compensator device (1) being removably attached to the feeder device (2) and located on one end (2A) or one side thereof, the compensator device (1) being fully automatic with respect to the feeder device (2), but the compensator device (1) being tightly connected to the feeder device when connected thereto.

14. The system according to claim 8, characterized in that said compensator apparatus (1) has means (26) rotating about its own axis and capable of receiving a yarn (F) when winding it in at least one of the feed or the draw conditions of the working machine.

15. Compensator apparatus adapted for use with a feeder apparatus (2), said feeder apparatus (2) being for feeding a yarn (F) comprising a metal wire at a constant tension to a processing machine, said processing machine being operated in a discontinuous manner, said compensator apparatus (1) being part of a system according to claim 8, said compensator apparatus (1) having a movable compensation device (13), said movable compensation device (13) being able to act together with said yarn (F) before said yarn (F) leaves said feeder apparatus (2), said movable compensation device (13) being defined by a rigid arm rigidly associated with means for actuating the movement of said rigid arm, said rigid arm acting together with said yarn (F) in a movable manner, when said yarn passes from a condition of less drawing to a condition of more drawing by said processing machine, said rigid arm being movable from a predetermined rest position in the feed direction of the yarn (F), but when the yarn (F) passes from a condition of more drawing to a condition of less drawing, said rigid arms moving in opposite directions, position detection means (19) being provided, said position detection means (19) being able to detect movements made with respect to said rest position, said position detection means (19) being connected to a control unit capable of directly or indirectly detecting the tension in the yarn (F) and controlling actuator means according to the tension set or detected, such that the rigid arm returns to the rest position after movement relative to the rest position, characterized in that the compensator device is a separate device compared to the feeder device (2) and is located on the side of the feeder device (2).

16. Compensator apparatus according to claim 15, characterized in that the means for actuating the movement of the rigid arm is a first electric motor (8), the first electric motor (8) being directly connected to the rigid arm by its drive shaft to rapidly compensate for any rapid movement of the rigid arm, which, when drawn by the yarn (F), is freely rotatable about the axis (M) of the drive shaft and which returns to the rest position by the action of the first electric motor.

17. Compensator apparatus according to claim 16, characterized in that the first electric motor (8) has a very low inertia.

18. Compensator apparatus according to claim 15, characterized in that it comprises a rotating device (26), the rotating device (26) being able to receive the yarn on the rotating device (26) when the processing machine is stopped or when the processing machine is in a phase of returning the yarn to the feed processing.