MXPA99002878A - Low inertia positive feeder for elastomer threads and procedure for food - Google Patents

Abstract

The present invention relates to a yarn feeder device, in particular, for elastic yarns, comprising: a tensioning device that exerts a force on the yarn in the longitudinal direction of the yarn, arranged to stretch the yarn with a defined tension value a yarn feeder wheel around which the stretched yarn can be rolled and received in a few turns, so that the thread tension existing before the yarn feeder wheel does not affect the yarn tension existing after the wire feeder wheel, or it affects little, and a motor coupled in actuator form with the wire feeder wheel that is energized, independently of the tensioning device, depending on the current thread consumption, and regardless of the thread tension, in a segment that follows the wire feeder wheel, said device being characterized in that it comprises a yarn tension sensor for detecting the yarn tension, which is disposed between the tensioning device and the yarn feeder wheel, and the yarn tension is adjusted by means of a controllable yarn brake as a function of the yarn tension value established by the yarn tension sensor.

Description

LOW INERTIA POSITIVE ALLOYER FOR ELASTOMER THREADS AND PROCEDURE FOR FOOD DESCRIPTIVE MEMORY The invention relates to a positive feeder, provided, in particular, for delivery to yarn consumption positions with yarn requirements that vary abruptly in time and elastic yarns. The elastic yarns or yarns vary their length in correspondence with the tension to which they are subjected, where possible very large variations in length can be recorded. For example, elastomeric yarns are used that stretch up to 7 times their length, or more. Therefore, the quantity of yarn delivered depends to a large extent on the tension at which the yarn is fed. While in many cases it is sufficient that the tension of elastic yarn is kept constant within preset limits, there is a series of application cases in which it is essential that a pre-established amount of yarn is fed in a fixed time interval. The amount of yarn is defined, for example, by a length of yarn with a pre-established yarn tension. If the yarn is very elastic, the feeding of a defined quantity can not be guaranteed. While in some cases the yarn requirement is constant over time, there are many application chaos in which the thread requirement varies a lot temporarily. These are, for example, flat knitting machines, similar knitting machines, circular knitting machines with sampler, machines for stockings, etc. In these machines, a woven knitted fabric or a knitted fabric in which the elastic yarn is woven together with one or more inelastic yarns, called hard, must often be made. This must be done in many cases in mass proportions, ie with a pre-set amount of hard yarn a corresponding amount of elastic yarn should be positively fed, as far as possible, with the same velocity profile. Due to the different yarn qualities, this is relatively complicated. It was found that a synchronized feeding in the amount of hard and soft yarns is relatively complicated, at least when consumption is variable. DE 38 25 034 discloses a yarn feeding apparatus for variable yarn consumption. The yarn feeder apparatus has a yarn feeder driven by a stepping motor whose outer periphery is defined by six wire arms. Before the yarn feeder wheel, with reference to the yarn displacement, a yarn brake is arranged. The thread feeder is followed by a thread tension sensor, for the regulation of the stepper motor and, therefore, the quantity of thread. The wire feeder device acts on the wire feed with constant tension. DE 42 06 607 A1 discloses a yarn feeding apparatus which acts on feeding variable amounts of elastic yarns over time. The wire feeder has a motor with armature on disk, linked to a wire feeder wheel. It is wrapped by the thread to be fed. In front of the wire feeder wheel, a wire brake is arranged in a fixed manner and contains a permanent magnet for the generation of the braking effect, or an electromagnet for the adjustable generation thereof. In order to control and maintain the thread tension constant, a wire tension sensor is installed behind the wire feed wheel which controls the motor with armature on disk. The yarn feeder device acts on the supply of elastic yarns with more or less constant tension, but not on the positive feeding of pre-established yarn quantities. By means of EP 0 499 380 A1 it is known to feed elastic yarns to a yarn consumption position with constant yarn consumption. The feeder device The yarn comprises two yarn feeder devices that operate independently from each other and which the yarn passes successively. Initially it is driven by a wire feeder that separates the yarn from the yarn bobbins. The wire feeder wheel is driven by an electric motor commanded in correspondence with the wire tension picked up by a wire tension sensor coupled with the wire feeder wheel. The wire is thus fed with a more or less constant tension to two wheels or feeder rollers that are in contact with each other by friction, being driven with a fixed speed and, thereby, delivering constant yarn quantities. In this way, constant quantities of yarn are fed to a yarn consumption position in which the elastic yarn is combined with a hard yarn. This device is not equipped to feed variable amounts of yarn over time. Furthermore, DE-AS 1585111 discloses a yarn feeding device for feeding yarns to a knitting machine with a constant yarn speed and, at the same time, with constant tension. This thread feeder device has two conical rollers driven in the same way, which are wrapped successively by the yarn. The thread crosses here a thread guide for each roller, which establishes with what diameter the thread is wound and unwound. By means of the differentiated fixing of the two unwinding diameters, it is possible to achieve that the yarn is initially separated from the bobbin with a small roller diameter and then taken by the next roller with a larger diameter, so that the yarn is strongly stretched in the two rollers. In the sector following the second roller, the yarn tension is again attenuated, thereby taking advantage of the hysteresis effect of the twisted yarn. This effect of hysteresis observed in twisted yarns leads to the yarn scarcely being shortened in the stress-free state, after the second roller. In this state it can be processed better. This device and the method were developed especially for the processing of constant amounts of twisted yarns with hysteresis effect.

From this, the object of the invention is to create a yarn feeding apparatus with which defined and variable quantities of elastic yarns can be fed to yarn consumption positions. Furthermore, it is an object of the invention to indicate a corresponding method. These objectives are solved by a wire feeder according to the attributes of claim 1 of the patent or a method according to claim 16 of the patent. The yarn feeder apparatus according to the invention has a tensioning device which confers a defined tension to the yarn coming from a bobbin. The wire feeder operates, on the input side, commanded by voltage, and on the output side, commanded by quantity. A yarn tension at least relatively constant is generated between the tension device and the positive feeder device. Tension variations caused by the influence of factors external to the yarn feeder device, such as variable friction in the yarn eyelets that are in the path to a yarn consumption position, are kept away in the field of yarn consumption. travel located between the tension device and the positive feeder device. In this way, yarn feeding can be carried out in defined quantities, independently of the frictional influences existing after the wire feeder. This is valid, in particular, with variable yarn consumption over time. Here, the conditions of yarn displacement are a function of speed. The separation of the yarn displacement sector following the yarn feeder device from the set tension path enables a controlled and correct time-variable yarn feed. The tensioning device can be arranged here with a non-linear force-path relationship, as is produced in the elastic threads. The usual elastic threads, such as elastomer thread, have large stretches with small variations in force in the field of small forces. However, as the tensile force or force increases in the longitudinal direction, the length variations become smaller and smaller. When the yarn reached its maximum stretch, a new increase in the strength does not bring about an appreciable stretch in the yarn. If the force is removed, the thread returns widely to its original length. This property generally makes it difficult to feed pre-established amounts of yarn. The tensioning device present in the yarn feeding apparatus according to the invention avoids this problem because it stretches both the yarn, that a variation of tension in the yarn hardly influences the length thereof. The yarn is fed in this stretched state to the yarn feeder wheel, driven by an electric motor in correspondence with the current yarn requirement, and, thus, independently of the yarn tension to be adjusted, delivering the desired amount of yarn. thread. A supply of defined quantities is also known as positive feed and is the opposite of wire feeding devices that supply yarn with consistant (reduced) tension and are called negative feeders.

The wire feeder wheel is driven by a motor, independently of the tensioning device. With this, the tensioning device can be developed in order to generate a high thread tension, independently of the operation of the wire feeder wheel. The tensioning device can be, for example, a kind of wire brake that works independently of the speed of travel of the thread. For example, it can be a friction brake, in which the thread is braked by friction elements on which it slides. If the yarn brake generates a more or less constant yarn tension, a relatively large yarn tension range can be accepted without the amount of yarn fed greatly varying thereby. This is a consequence of the fact of tensioning the thread up to its maximum limit. The tensioning device can also bealternatively, a regulated wire brake which, for example, is adjusted according to the thread tension between the wire brake and the wire feeder wheel. In this way it is possible to compensate for the frictional influences that occur, for example, before the wire feeder. In addition, in many cases the ability of the apparatus to react to sudden variations in feeding requirements is improved. Surprisingly, an improvement of the dynamic properties of the yarn feeder apparatus with the tensioning device both regulated and unregulated is possible. When the yarn feeder is accelerated, the tensioned yarn behaves like a hard yarn in front of the yarn feeding wheel, with which stretches are produced with the voltage variations that can modify the amount fed. The regulating steps prior to the yarn feed wheel hardly or do not affect the accuracy from the point of view of the amount of yarn fed, in particular, during the transition stages when accelerating or decelerating the yarn feeder wheel. Different types of construction are taken into account for the wire brake. For example, it is possible to use a simple friction wire brake with two holding plates. These can be pressed together by a spring or magnets. For this purpose, an electromagnet or other electrically commandable means are also suitable, for example, by the regulator loop. Instead of the wire brakes, a separate wire feeder wheel having its own drive motor can also be provided as a wire tension. This second yarn feeder wheel has the task of separating the yarn from a reel and feeding it, in a stretched state with a defined tension, to the yarn feeder wheel located later, referring to the ction of yarn displacement; while the upper thread feeder wheel is coupled with a motor which operates preferably commanded by tension, the motor of the lower thread feeder wheel preferably operates commanded by quantity. This is valid, correspondingly, for the embodiment with regulated brake mentioned above. In this way, with the yarn feeder apparatus according to the invention, a positive supply of elastic yarns corresponding to the yarn requirements variable in time is possible. Thread tensioners can be dispensed with after the wire feeder wheel, wrapped by the stretched thread. While the tensioning device can operate in a fixed or regulated manner by means of the thread tension, the thread feeder wheel following the tensioning device, in the direction of yarn displacement, is preferably operated with an open command chain . This enables the reaction free of regulation oscillations at modified yarn tension requirements. In addition, the positive feed can be started as soon as or before a sudden increase in yarn requirement occurs, i.e. before tension variations are picked up in the yarn path between the yarn feeder wheel and the position of thread consumption. The yarn feeder apparatus is preferably coupled to a command unit, or has one that commands the motor of the yarn feeder wheel with the rotational speed corresponding to the desired yarn feed. The data can be obtained by the command unit, for example, by means of a sample data memory. In flat knitting machines it may be practical to deduce the yarn requirement from the movement of the yarn guide, captured, in the simplest case, with light barriers, limit switches or the like. In addition, it may also be practical to determine the elastic yarn requirement by measuring the speed of movement of another yarn, for example, a hard yarn to be processed by the considered machine. For this purpose, a measuring device for the yarn displacement speed can be provided, coupled with the command unit. This then makes it possible to feed the elastic yarn to a yarn consumption position in a form, for example, strictly proportional in quantities with respect to another yarn. The sensor device is, for example, a measuring wheel wrapped by the other thread (hard thread) and is supported on the axis of an encoder. In addition, the command unit may be coupled to the tensioning device, in order to regulate it. For example, the control unit is coupled with the corresponding electric brake adjustment devices or with the motor of a corresponding wire feeder wheel, arranged between the tensioning device and the wire feeder wheel. Further details of suitable embodiments of the invention can be seen in the drawing of the description and in the subclaims. Exemplary embodiments of the invention are illustrated in the drawing. There they show: fig. 1 a schematic representation of the principles of a first embodiment of the yarn feeder device, for feeding elastic yarns to a flat knitting machine, fig. 2 a simplified embodiment of the wire feeder device according to FIG. 1, and fig. 3 a modified embodiment of the yarn feeder device.

DESCRIPTION OF THE INVENTION The wire feeder device illustrated schematically in FIG. 1 acts by feeding an elastic thread 1, from a reel 2, to fabric positions 3 of a flat knitting machine 4. The fabric positions 3 are constituted by individual needles 5, before which it passes, coming and going (arrow ), a thread guide 6. The thread guide 6 is fed with both the elastic thread and a hard thread 11. It is separated from another corresponding coil 12. The feeding of the hard yarn can be carried out positively by means of a feeder not illustrated in more detail (yarn feeder apparatus), or the pulling effect of the needles 5 during the weaving process. The fed or separated amount of yarn 11 here establishes the size of the mesh. The amount of yarn is not constant in time. In the investment sectors of thread guide 6, thread consumption is briefly interrupted. In addition, the yarn consumption in the round trip is different from at least when the distance between the thread guide 6 and the devices to be fed in the back and forth movements of the thread guide varies. In the feeding of the elastic yarn 1, the yarn feeder device 14, to which a tensioning device 15 and a yarn feeding wheel 16, operated by an electric motor 17, is engaged. The yarn 1 repeatedly wraps the yarn feeder wheel 16. and is dragged by the 'same exempt from landslides. The yarn feeder wheel thus establishes the quantity of yarn fed to the yarn guide 6. In order to fix it for the stretched state of the yarn 1, the yarn 1 is stretched by the tensioning device 15 almost to its maximum value, but at least up to a value in which there are almost no variations in length with variations in force. In order to achieve this, both the envelope brake 15 and the electric motor 17 are coupled with a command unit 18 which sets both the speed of rotation of the motor 17 and the effect of the tensioning device 15. The tensioning device 15 presents a speed adjusting device 19, in the drive of which two support rods 21, 22 are eccentrically housed. The thread 1 surrounds these support rods 21, 22 at an angle which is a function of the rotational position of the adjusting device of speed of rotation 19 and, therefore, comandable by means of the command unit 18. Between the tensioning device 15 and the wire feeding wheel 16 there is arranged a wire tension sensor 24 which captures, here, the thread tension. The wire tension sensor 24 provides its measured value or its data to the control unit 18, which, for example, can be configured as a microprocessor. The command unit 18 receives a pre-set value for the tension of the yarn 1, by means of an input device not illustrated here in greater detail. It may be stored in a memory cell 25, illustrated in FIG. 1. The preset value is set at a value at which the yarn almost reached its limit stretch. During the operation of the yarn feeder device 15, the command unit 18 commands the tensioning device 15 so that the yarn 1 separated by the tensioning device 15 reaches the desired high preset tension. When a deviation is detected by the wire tension sensor 24, the command unit 18 commands the tensioning device 15 accordingly. On the other hand, the motor 17 of the wire feeder wheel 16 is commanded in correspondence with the actual yarn consumption . In order to determine the same, a measuring device 26 to which a wire roller 27 and, for example, an incremental angle generator 28, on whose axis the roller is supported, is disposed in the path of the hard thread 11. yarn 27. The yarn roll 27 is wrapped by the hard yarn 11, and rotates according to its speed. In this way, the angle generator 28 captures the wire speed and emits the corresponding signal, through a line not illustrated here in greater detail, to an input 31 of the regulating unit 18. Another input 32 of the regulating unit 18 is connected to the wire tension sensor 24 and receives therefrom a voltage signal of thread. The sample data or other command data, which characterizes the amount of elastic yarn to be fed, are delivered to another input 33 of the command unit 18. A first output 34 of the command unit 18 commands the engine 17 , while a second outlet 35 is connected to the tensioning device 15 and regulates it. The yarn feeding apparatus 14 described hereinabove operates as follows: In its operation, the yarn guide 6 of the flat knitting machine 4 is moved back and forth, transversely to the woven band, with a stroke determined by the width of the same. For this, the fabric positions constituted by the needles 5 must be fed with the same or corresponding quantities of elastic yarn 1 and hard yarn 11. Through the input 33, the command unit 18 obtains at least information about the direction of travel of the thread guide 6. In the ideal case, the command unit 18 also receives information about the speed of the thread guide 6. It can be determined by measuring the position or speed, or it is available it as a fixed or pre-established value. From the speed of the thread guide 6 and its direction of movement, the command unit 18 determines the stretch or shortening generated during the displacement of the thread guide 6 of the path considered for the thread 1 and the thread 11. The speed of the wire 1 captured by the measuring device 26 is a speed that is obtained from the variation of the length of the thread path and the thread consumption in the needles 5. In the command unit 18 the path proportion decreases with the path length variation or can be determined from the speed of travel of the thread guide, in order to determine the actual yarn consumption from the measured yarn travel speed, calculating it adequately. From this value, the command unit 18 determines the amount of elastic yarn required by the needles 5, for example, as a fixed ratio with the amount of hard yarn to be processed by the needles 5. For this, the command unit 18 adds the amount of yarn obtained by stretching or arranging the path of yarn 1, with the correct sign. By means of the value thus obtained, command pulses are formed for the motor 17, with a speed of rotation corresponding to the amount of wire fed. At the same time, and independently of this process, the command unit 18 regulates, by means of the tensioning device 15, the yarn tension before the yarn feeder wheel 16 at a defined value, the same being so high that the yarn Elastic 1 stretches almost completely and behaves roughly like a hard thread. In an alternative embodiment, illustrated in fig. 2, the tensioning device 15 is formed by a wire brake 41, which operates without regulation. The wire brake 41 has, for example, two disc-shaped plates 42, 43, which act as braking elements and are placed on a bolt 44, being pressed together by a spring 45. The wire 1 is clamped between the plates 42, 43 and can be slid with friction through them. The yarn brake 41 is fixed in a fixed manner at a yarn tension value so high that the yarn 1 is stretched almost completely between the yarn brake 41 and the yarn feeder wheel 16, essentially independently of its travel speed . Consequently, the wire tension sensor 24 and the corresponding input 32 are omitted in the command unit 18. In the rest, this embodiment of the wire feeder device 14 coincides, in its structure and operation, with the wire feeder device described (fig. 1 ). That is why the same references are used and reference is made to the preceding description. Another modified embodiment of the wire feeder device is shown in FIG. 3. The differences lie again in the tension device 15; in the rest, reference is made to the previous description, which is still valid. The tensioning device 15 of the wire feeder device 14 according to FIG. 3 presents a wire feeder wheel 51 which is supported on the shaft of another drive motor 52. The wire feeder wheel 51 essentially resembles the wire feeder wheel 16 and is wrapped, as the previous one, one or more times by the thread 1. Between the wire feeder wheels 51, 16 there is arranged a wire tension sensor 24, connected to the input 32 of the command unit 18. It commands now, instead of the adjusting device 19. , to drive motor 52, so as to separate yarn 1 from spool 2 and feed it to yarn feeder wheel 16, thus adjusting the desired high yarn tension until the yarn is stretched. For this "the command unit 18 emits a corresponding command pulse at its output 35. The advantage of this embodiment lies in the rapid establishment, between the two yarn-feeding wheels 52, 16, of the defined yarn tension, and in decoupling the yarn tension from external factors in this thread path after the positive feeder, if necessary, this can proceed without the rotation of the yarn feeder wheel 16 when the yarn feeder wheel 52 is commanded in reverse A yarn feeding device for feeding elastic (soft) yarns to a yarn consumption position with variable yarn requirements over time has a command unit which determines or receives the current yarn requirement. with a rotational speed according to this requirement, the wire reaches, through a tensioning device, the wire feeder wheel. so that the yarn is stretched in a defined manner. In this way, a fixed coordination of the desired amount of wire feed and the speed of rotation of the wire feeder are possible.

Claims (3)

1. NOVELTY OF THE INVENTION CLAIMS 1. - Thread feeding device [14], in particular, for elastic threads, characterized in that it comprises: - a tensioning device [15] that exerts a force on the thread in the longitudinal direction thereof, equipped to stretch the thread with a defined tension , - a wire feeder recess [16] which is wrapped by the stretched yarn [1] and accommodates it with few turns, and the yarn tension existing before the yarn feeder wheel [16] does not affect or affect the existing thread tension after the wire feeder wheel [16], - a motor [17] coupled in drive form to the wire feeder wheel [16] and commanded, independently of the tensioning device, depending on the yarn consumption and independently of the thread tension [1] existing in a sector that follows the thread feeder wheel [16].
2. 2. Wire feeding apparatus according to claim 1, characterized in that the tensioning device [15] is a wire brake [41] that generates the wire tension essentially independently of the speed of movement of the wire.
3. 3. Wire feeding apparatus according to claim 1, characterized in that a wire tension sensor [24] is arranged between the tensioning device [15] and the wire feeder wheel [16], for capturing the tension of the wire tensioner [16]. thread, and the thread tension is adjusted by means of a thread brake [21, 22] comandable as a function of the thread tension value set by the thread tension sensor [24]. 4, - Wire feeder device according to claim 2 or 3, characterized in that the wire brake [22, 23] is a friction brake with a fixed or adjustable load on its friction elements. 5. Wire feeding apparatus according to claim 4, characterized in that, for loading the friction elements, a force-generating device [19] is provided, electrically commutatable and linked in its effect to at least one of the elements 6.- Wire feeder apparatus according to claim 2 or 3, characterized in that the wire brake [21, 22] is a casing brake with at least one enclosing element, whose casing angle is affected by a device of adjustment [18]. 7. Apparatus for feeding yarn according to claim 6, characterized in that, for the adjustment of the wrapping angle, a device [19] is provided, electrically commutatable and linked in its effect to at least one wrapping element. 8. Wire feeding apparatus according to claim 3, characterized in that, before the wire tension sensor [24], there is arranged a wire feeder wheel [51] linked to an actuator device wrapped by the thread [1] and whose The rotational speed is controlled or regulated by the wire tension sensor so that a wire tension sensor [24] provides essentially constant wire tension. 9. - Wire feeder apparatus according to claim 8, characterized in that the actuator device is a motor [52]. 10. Wire feeding apparatus according to claim 1, characterized in that motor of the wire feeder wheel [16] is commanded, between the wire feeder wheel [16] and the thread consumption position, independently of the thread tension. 11. Wire feeding apparatus according to claim 1, characterized in that the wire feeder apparatus [14] has a command unit [18] or is connected to a command unit that commands the motor [17] depending on the amount of yarn desired. 12. Wire feeding apparatus according to claim 11, characterized in that the command unit [18] is connected to a sample data memory. 13. Wire feeder device according to claim 11, characterized in that the command unit [18] is linked to a sensor device [26], for capturing the speed of movement of one or several other wires [11], which preset the elastic yarn requirement [1]. 14. Wire feeding apparatus according to claim 13, characterized in that the sensor device [26] has a measuring roller [27] and an angle generator [28]. 15. Wire feeding apparatus according to claim 11, characterized in that the command unit [18] is linked to the tensioning device [15], in order to regulate the thread tension in accordance with a pre-established value. 16. Process for feeding elastic yarns with pre-established and variable yarn quantities in time, characterized in that it comprises the following steps: the yarn is stretched to a defined value after its separation from a spool, at least one index that characterizes the amount of yarn currently required, - after stretching, the yarn is driven, in the stretched state, to a feeder device equipped to feed the drawn yarn in accordance with the index. 17. Yarn feeder device according to claim 16, characterized in that, after its separation from the bobbin, the yarn is stretched to a value in which an increase in force does not result in other reversible increases in the length of the yarn. thread.