TECHNICAL FIELD

The present disclosure relates to a yarn feeder and a yarn feeding arrangement. In particular, the present disclosure relates to a yarn feeder and a yarn feeding arrangement suitable for providing a heavy yam to a textile machine such as a rapier weaving machine.

BACKGROUND

A general development trend in weaving is that the speed of the textile machine is constantly being increased. This is also so for heavier yams such as jute and polypropylene.

When weaving with heavy yarns such as jute and polypropylene that is often used in for example carpets, some additional problems can occur. For example, braking of the yarn to achieve a correct yarn tension during weaving can become more problematic as described in EP3368458. EP3368458 describes how the braking can be modulated (varied) during weft insertion.

Another problem when feeding heavier yarns to a textile machine, is how to provide an efficient balloon brake device. Different solutions exist how to reduce or even avoid ballooning. For example, in EP 0686128 a combination of yam balloon brake element and yarn brake was introduced, a so-called flex brake. Also, brushes have been used to avoid ballooning from occurring.

Further, US 5, 509, 450 describes a device for feeding weft yarn to a weaving machine where a retainer moving around a storage drum is provided to provide a weft yarn feed that is adapted to the weft yarn insertion speed. There is a constant desire to improve yarn feeding to textile machines. Hence, there is a need for an improved yarn feeder.

SUMMARY

It is an object of the present invention to provide an improved yarn feeder and yarn feeder arrangement.

This object and/or others is/are obtained by the weft yarn feeding device as set out in the appended claims.

As has been realized by the inventors, existing devices for balloon braking do not provide a satisfactory result when feeding a heavy yarn such as jute to a textile machine. For example, if a brush brake is used, it can typically brake the balloon satisfactorily, but due to the nature of the heavy yam in combination with a high yam speed, the brush bristles wear out in very short time. The durability can be as short as a week, or sometimes even shorter which is not acceptable. If a so called flexbrake is used, it can stand wear better, however it will not brake the yarn balloon sufficiently unless an excessive force is applied. Such a high force will result in a yarn tension that is too high for a well working insertion into the weaving shed. For example, a too high yarn tension will result in that the yam grippers will lose the yarn due to the high yarn tension, or that the yarn breaks.

In order to enable braking of the yam balloon also for heavy yarns drawn at a high speed an eyelet rotating around the yarn storage of the yarn feeder at an output end section of the yarn feeder and in synchronization with the insertion speed of the weft yarn to the textile machine can be used. The rotation eyelet can be provided in a manner as described in the above-mentioned patent, US 5, 509, 450. Good synchronization can be obtained by providing a sensor adapted to provide a feedback signal indicative of the current yam consumption such that the eyelet is enabled to adjust rotation in accordance with the momentary yarn consumption of the weaving machine.

In accordance with the present invention, a yarn feeder for feeding yarn to a textile machine is provided. The yarn feeder comprises aa spool body for storing yarn to be fed to the textile machine. The spool body has a spool body axis. The yarn feeder further comprises an eyelet arranged radially displaced from the spool body and a motor for driving the eyelet in a circular motion co axially with the spool body axis. The yarn feeder also comprises a sensor arrangement arranged downstream the eyelet to provide a yarn consumption sensor signal indicative of the current weft yarn consumption of the textile machine. The motor is configured to be driven based on a pre-stored weft yarn insertion speed model of the textile machine and the yam consumption sensor signal. Hereby a yarn feeder that can feed yarn to a textile machine with efficient braking of the yam also when the yam is of a heavier type can be provided.

In accordance with one embodiment, the eyelet is located at the end of the spool body from which yarn is fed to the textile machine. Hereby an easy to implement rotation mechanism for the rotation of the eyelet can be provided.

In accordance with one embodiment, the sensor arrangement comprises a yarn buffer and a position sensor arranged to detect the position of the yarn buffer, wherein the position sensor is configured to output the position of the yam buffer, where the position of the yam buffer indicates the difference between the amount of yam fed to the yarn buffer and the amount of yarn drawn by the textile machine, such that the output signal of the position sensor is a signal indicative of the current yam consumption by the textile machine. Hereby a sensor arrangement that is easy to implement is obtained. Also, the provision of a yarn buffer can facilitate control of the yam feeder since it makes it possible to take up the extra yarn, or feed the yarn that is missing, in the actual insertion to the textile machine. In accordance with one embodiment, the yarn buffer comprises a pivoted spring-loaded arm and the position sensor is arranged to determine the position of the spring-loaded arm. Hereby a yam buffer that keeps the yarn stretched can be obtained.

In accordance with one embodiment, the yam feeder further comprises a controller configured to control the motion of the motor driving the eyelet using the pre-stored weft yarn insertion speed model of the textile machine and the yarn consumption sensor signal. Hereby the yarn feeder can be implemented as a compact unit with no need for external connections.

In accordance with one embodiment, the controller is configured to obtain a motor feedback signal with information about the position and or speed of the motor and to control the motion of the motor driving the eyelet also based on said motor feedback signal. Hereby a more refined control can be obtained in that the controller can base the control also on how the motor is actually driven.

In accordance with one embodiment, the controller is configured to operate in a feed forward control mode. Hereby it is made possible to operate the textile machine at high speed and high dynamics with regard to acceleration and retardation.

In accordance with one embodiment, the controller is configured to obtain and store the weft yarn insertion speed model in a separate learning phase. Hereby the weft yam insertion speed model can be made accurate since the model is derived directly from the actual textile machine.

In accordance with one embodiment, the controller is configured to operate a feedback control mode during the learning phase. The separate learning phase can be a slow-motion operation of the textile machine performed before operating the textile machine at full operational speed. Because the learning phase is run at a low speed it is possible to operate in a feedback mode and thereby fine tune the yam insertion speed model before operation at full speed which can be performed in feed forward mode.

In accordance with one embodiment, the controller is configured to continuously or periodically obtain the textile machine angle and to use the weaving machine angle when controlling the motion of the motor driving the eyelet. Hereby a good synchronization between the textile machine and the drive of the motor can be obtained.

In accordance with one embodiment, the yam feeder comprises a guide member journalled at the front end of the yam feeder, the guide member being connected to the eyelet and configured to guide weft yarn from the eyelet. The guide member can for example be a tube. Hereby a robust rotation of the eyelet can be obtained and at the same time yarn can be guided from the eyelet to a front output position.

The invention also extends to a system for feeding yarn to a textile machine and to a method for feeding yam to a textile machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

- Fig. l is a view illustrating a weft yam feeder,

- Fig. 2 is a view of a first set up with a weaving machine,

- Fig. 3 illustrates an alternative set up with a weaving machine,

- Figs. 4a - 4c illustrate weft yarn consumption sensors,

- Figs. 5 is a flow chart illustrating different steps performed when forming a weft yam buffer, and

- Fig. 6 is a view of a controller. DETAILED DESCRIPTION

In the following a weft yarn feeding arrangement for a textile machine will be described. In the Figures, the same reference numerals designate identical or corresponding elements throughout the several Figures. It will be appreciated that these Figures are for illustration only and are not in any way restricting the scope of the invention. Also, it is possible to combine features from different described embodiments to meet specific implementation needs.

In accordance with the invention an outgoing yam from the spool body of a yarn feeder is led through an eyelet that is arranged to rotate around the spool body and then the eyelet is controlled to follow the yarn speed corresponding to the current yam consumption of the textile machine. Hereby the yarn feeder can deliver the yam with low yam tension and without risking ballooning of the yarn when taken from the spool body to be fed to the textile machine. Also, the yarn tension can be kept low and at a controlled level within tolerance limits of the textile machine.

When producing a textile fabric, the textile machine can pull a determined length of yarn during each machine cycle. The yarn feeder delivers a determined length of yarn at each machine cycle. The length that is delivered from the yarn feeder is determined by a controller that controls the rotation of the eyelet. The rotation of the eyelet is controlled to be in synchronization with the pull speed of the textile machine. For example, a machine angle information can be provided to the controller (for example an encoder on the weaving machine main shaft can be used to read out and provide the textile machine angle). Alternatively, a synchronization signal such as a clock signal is provided to both the controller and the textile machine. The difference in yarn length between what the textile machine consumes and what the yam feeder delivers is determined and used as a feedback signal to fine tune the control of the rotating eyelet. In Fig. 1 a partial cross-sectional view of a yarn feeder 10 is shown. The yarn feeder comprises a spool body 12 onto which a yam 14 can be wound to be fed to a textile machine in the direction of the arrow of Fig. 1. The spool body 12 can have a central spool body axis 16 and is typically cylindrical in shape.

The yam feeder also comprises an eyelet 18 arranged radially displaced from the spool body 12 as seen from the spool body axis 16. The eyelet 18 is typically located at the end of the spool body 12 from which yam is fed to the weaving machine, i.e., at the downstream end of the spool body as seen in the direction in which yarn is intended to be fed to a textile machine. Thus, the eyelet 18 can rotate around the spool body take off end radially distanced therefrom.

Further, a motor 20, with or without a gearing, for driving the eyelet 18 in a circular motion co axially with the spool body axis 16 is provided. The eyelet 18 is advantageously driven in a plane perpendicular to the spool body axis 16. The motor 20 is configured to be driven based on a pre-stored weft yarn insertion speed model of the textile machine and a sensor signal indicative of the current weft yarn consumption of the textile machine. The motor 20 can advantageously be driven with feed forward control technology. The motor 20 can further comprise means for sensing the motor speed and or motor position. For example, an encoder can be provided on the motor shaft to enable read out of the rotation/position of the motor axis.

The motor 20 can be controlled by a controller 22. The controller 22 can be located on the yarn feeder as seen in Fig. 1, but could alternatively be located at a location apart from the yarn feeder and configured to provide control signals to the motor 20 via a wireline or by a wireless control signal. The motor 20 can advantageously be a controlled electrical motor, for example a vector-controlled permanent magnet (PM) motor. The controller 22 is configured to control the motor 20 such that the motor unwinds yam from the spool body 12 in synchronization with the current yarn consumption of the textile machine to which the yarn feeder feeds yarn. In accordance with one embodiment, the controller 22 can control the unwinding of yarn from the spool body by using a model of the weft yarn insertion speed pattern and a sensor signal indicative of the current weft yam consumption of a textile machine.

In accordance with one embodiment, the motor is further controlled by a motor feedback signal that provides information about the actual motor position or speed. The motor feedback signal can for example be provided by an encoder as set out above. Hereby a more accurate control of the motor drive can be achieved.

The eyelet 18 can be driven in different ways. In the embodiment of Fig. 1 a guide member 24 , here a flyer arm, is journalled in a front-end section of the yarn feeder 10. The guide member 24 is rotated around the spool body axis 16. The guide member 24 can in accordance with some embodiments be a tubular element. The eyelet 18 can be located at the outer end of the guide member 24 The guide member is connected to the motor 20 such that the motor rotates the eyelet around the spool body by rotating the guide member 24. The eyelet 18 can advantageously have an inside surface covered by a ceramic material or the eyelet 18 can be formed by a ceramic material to provide a surface for the yam with low friction and high wear resistance. The eyelet 18 can feed the yam from the spool body 12 to the guide element 24. In case the guide element is tubular, the yam is pulled off from the spool body 12, follows the inside of the tube and comes out at a frontal output section.

The eyelet 18 can be rotated in other ways and does not need to comprise a tubular element such as a hollow shaft. The eyelet can be supported in different ways as long as it can rotate around the spool body axis 16. The yarn can be guided in the free air or be supported at appropriate positions. The eyelet 18 can advantageously be placed at a radial distance and also in over the spool body 16 to reduce the risk that the weft yarn 14 wound on the spool body 12 slips off from the spool body front rim. In other words, the eyelet 18 can be rotated radially distanced from the surface of the spool body 12 and axially at a position coinciding with some section of the spool body 12. For example, the eyelet 18 can be located at a position axially upstream the front-end section of the spool body 12.

In Fig. 2, an exemplary set up with a textile machine in accordance with a first embodiment is shown. In Fig. 2, a yarn 14 is provided from a yarn storage 30 such as a bobbin. The yarn 14 is provided to a yarn feeder 10. The yarn feeder 10 comprises the spool body 12 and the motor 20 as depicted in Fig. 1. The yarn feeder further comprises a sensor arrangement 26 for providing a signal indicative of the current weft yarn consumption of a textile machine 40 arranged downstream the yam feeder 10 as seen in the direction of feeding the yarn 14.

In Fig. 2, the yarn 14 is fed in an angle relative to the textile machine 40. In Fig. 3 an alternative embodiment is shown, where yam 18 is fed in a straight line to the textile machine 40.

The sensor arrangement 26 can be implemented in various ways to provide a signal that indicates the actual (current) consumption of yarn of the textile machine. For example, the position of a spring-loaded arm can be determined and provided as a sensor signal indicative of the yarn consumption. The arm can be pivoted, but other implementations are possible such as using a linearly moving member or a member forming a yarn loop.

In Fig. 4a, a sensor arrangement 26 in accordance with one embodiment is shown. The sensor arrangement 26 comprises a pivoting arm 52. The arm 52 is spring loaded by a spring 54. A position sensor 56 is arranged to determine the position of the arm 52. In use, yam 14 is angled over the arm 52 in a way so that when the yam tension increases as a result of too little yarn provided by the feeder, the arm is moving against the spring force and when the yarn tension decreases as a result of too much yarn provided by the feeder, the sensor arm moves in the opposite direction. In other words, when yarn is consumed at a higher rate than provided, the arm will move against the load of the spring 54 and vice versa. Hereby the position of the arm 52 will indicate if the textile machine consumes more (or less) yam than fed by rotation of the eyelet 18.

The arm 52 forms a yarn buffer that can be used to compensate for small variations in yarn consumption of the textile machine 40 in relation to yarn fed via the rotating eyelet 18. By sensing the stroke of the yarn buffer, here the position of the arm 52, it is possible to provide a feedback signal indicative of the current weft yarn consumption of the textile machine. Hence, the position of a yarn buffer downstream the eyelet can be used to provide a feedback signal indicative of the current weft yarn consumption of the textile machine.

In one embodiment the weft yarn insertion speed model is compared with encoder signals from the rotating eyelet of the yam feeder and with the sensor signal from the yarn buffer, where the sensor signal from the yarn buffer represents the error in the control and is used to correct this error.

The use of a spring-loaded arm 52 has additional advantages. For example, the spring- loaded arm 52 will strive to keep the yam tension at a desired level. Also, the spring-loaded arm 52 acts as a yarn buffer to compensate for inaccuracies in the amount of yarn fed to the textile machine. The spring-loaded arm forming the buffer thus allows for the yarn to be kept stretched, without any slack, and it makes it possible to take up the extra yarn, or feed the yam that is missing, in the actual insertion to the textile machine. This is advantageous since the length of the insertions typically varies slightly from pick to pick.

As an alternative to a spring 54, other mechanisms can be used to provide a force on the arm 52. For example, an electromagnetic arrangement can be used. In such an embodiment the load on the arm can be controlled by controlling the current to the electromagnet.

Alternatively, a permanent magnet can be used or a pneumatic force such as a gas spring or compressed air cylinder can be used. The arm 52 of the sensor arrangement 26 can advantageously have a length sufficient to take up or release the yam length that is a result from errors in the control and the yam length that results from the speed steps when the textile machine takes and release the yarn. Typically, the arm 52 can have a length between 15 mm and 120 mm, in particular between 40 mm and 70 mm.

As set out above, the force of the buffer arm can in one embodiment be settable by for example a spring with variable force, or via an actuator for example an electric motor or electromagnet. The force can be settable to optimize a certain article, for example yams of different size and weight typically need different spring force to have optimized running conditions. The force can in one embodiment be settable also within each pick to obtain different yam tension in different zones of the insertion to the textile machine.

In Fig. 4b, an embodiment with a spring-loaded arm 52 in accordance with the setup of Fig.

2 is depicted. In the embodiment of Fig. 4b the spring-loaded arm is pivoted at an end section of the arm 52.

In Fig. 4c an embodiment with a spring-loaded arm 52 in accordance with the setup of Fig.

3 is depicted. In the embodiment of Fig. 4c the spring-loaded arm 52 is pivoted at a midsection of the arm 52.

In Fig. 5, a flow chart illustrating some steps when controlling the motor driving the eyelet in the above examples is shown. The example given is assuming that yam is fed to a rapier weaving machine but the method can be applied in a corresponding manner to other types of textile machines consuming weft yam at varying speed. First, in a step 501 the controller is provided with information relating to speed or position of the rapier(s) at different points in time during running of the rapier weaving machine. In step 501, a model of weft yam insertion speed, or position in relation to machine angle, in the textile machine during a machine cycle is formed. The actions in step 501 can be taken before start-up of the system and are not necessarily part of the control procedure. In accordance with one exemplary embodiment a learning procedure where the weaving machine is run at low speed (typically much lower than the full operational speed of the textile machine) is applied. In such a learning procedure a model is formed by determining the yam consumption rate at different weaving machine angles. By building a model of the yarn consumption rate at different weaving machine angles by running a learning procedure at slow rate before operating the weaving machine at full rate, an accurate model can be formed. Typically, a look-up table of relevant control data can then be pre-loaded to a controller before the weaving machine is set to run at full operational speed.

During the learning phase at low speed, the rotating eyelet can be controlled by the information from the sensor arrangement. A model of the weft insertion yarn motion, i.e., the weft yarn insertion speed in the weaving machine can then be determined by logging the speed of the rotating eyelet, that represents the speed of the yarn from the yam feeder, and the actual position of the yarn buffer, in relation to the textile machine angle.

The controller can be connected to the weaving machine to obtain the machine angle information. It is then not necessary to stop between machine cycles or run whole cycles. In a preferred embodiment at least one machine cycle (360 degrees) is run during the learning procedure.

In a preferred embodiment of the learning phase, the weaving machine is first run slowly where a feedback control from the sensor arrangement is possible to use. The data obtained of the yarn speed consumption behavior of the weaving machine is then saved to be later used to partly or fully run a feed forward control of the yam feeder at higher speeds.

An exemplary learning procedure when introducing a new yam or a new machine can be as follows: 1. The eyelet rotates so it follows the consumption of yarn and after one machine cycle the yarn feeder has released the yarn length that corresponds to one insertion to the textile machine. The sensor signal of the sensor arrangement obtained is used to control the rotating eyelet so it follows the insertion of the weaving machine and by comparing the amount of yam unwound by the rotating eyelet, the weaving machine angle and the sensor arrangement position, the motion of the yam in the yarn feeder is determined. A feed forward curve to be used by the control system is determined based on the detected motion of yarn in the yam feeder and used in the next step. If a higher precision is needed this can be repeated for several weaving machine cycles.

2. Step 1 is repeated in higher speed. Dynamic properties are obtained, and the controller makes compensation for dynamic properties. During step 2 the determined feed forward curve from step 1 can be used. Step 2 is needed in some cases, but in other cases it is possible to go directly to step 3.

3. The control system now has information enough to start weaving. An ILC (Iterative Learning Control) component in the controller can be used to compensate for the deviations that occur during running of the system. The use of ILC control of a system that work in a repetitive mode, which is the case for a textile machine. Other examples of systems that operate in a repetitive manner include robot arm manipulators, chemical batch processes and reliability testing rigs. In each of these tasks the system is required to perform the same action over and over again with high precision. This action is represented by the objective of accurately tracking a chosen reference signal r(t) on a finite time interval. The repetition allows the system to improve tracking accuracy from repetition to repetition, in effect learning the required input needed to track the reference exactly.

The learning process uses information from previous repetitions to improve the control signal ultimately enabling a suitable control action to be found iteratively. The internal model principle yields conditions under which perfect tracking can be achieved but the design of the control algorithm still leaves many decisions to be made to suit the application. A typical, simple control law is of the form:

Up+1 = Up + K * ep where Up is the input to the system during the p:th repetition, ep is the tracking error during the p:th repetition and K is a design parameter representing operations on ep. Achieving perfect tracking through iteration is represented by the mathematical requirement of convergence of the input signals as p becomes large whilst the rate of this convergence represents the desirable practical need for the learning process to be rapid. There is also the need to ensure good algorithm performance even in the presence of uncertainty about the details of process dynamics. The operation K is crucial to achieving design objectives and ranges from simple scalar gains to sophisticated optimization computations.

Next, in a step 503, the motor driven eyelet is controlled by the controller to unwind weft yarn from the spool body of the yam feeder in synchronization with the weft yarn insertion speed to the weaving machine. Since the weaving machine operates at high speed, the control algorithm used is advantageously a feed forward type of control where the control is based on the model of the weft yarn insertion speed pattern of the weaving machine obtained in step 1 (and 2).

Further, in a step 505, the controller obtains a feedback signal from the sensor indicative of the difference between the output speed of yam from the motor driven eyelet and the actual weft yam insertion speed in the weaving machine or some other related parameter such as the difference in length unwound by the eyelet and the length of yarn consumed by the textile machine. The feedback signal is used to fine tune the control of the motor driven eyelet. The controller can also obtain other input signals. The input to the controller for determining control data can in accordance with one embodiment be signals representing the state of the weaving machine. The signals can for example represent actual position (machine angle, machine encoder position), start in advance, speed ramp up, pattern, channel sequence or other signals representing events or motions in the weaving machine that could impact the insertion speed or sequence of the weft yarn. The signals can also be used to suppress an insertion if the weaving machine is performing a so- called pick finding. For example, the weaving machine can in accordance with one embodiment be run in slow motion or back and forth to remove a faulty pick. During such a procedure, the yarn feeding arrangement can be controlled to not release any yarn. Another example can be that the weaving machine moves in a special sequence to avoid start marks in the woven textile. Based on these movements and commands from the weaving machine, the controller 22 of the yarn feeder 10 can be configured to perform predetermined actions.

Also, signals from the motor driving the rotating eyelet can be obtained by the controller. The signals can for example be a signal representing the position and/or speed of the motor, for example a signal from a rotation/angle sensor such as an encoder. Other signals representing the state of the motor could also be used. Examples can here be the motor current or similar. The motor current provides information about the momentum of the motor that can be used to determine the acceleration of the rotating eyelet.

Further, signals indicative of the present (actual) weft yarn consumption can be obtained by the controller, for example signals from a sensor detecting the stroke of a yarn buffer placed between the output of the yarn feeder 10 and the textile machine.

Finally, in a step 507, the motor drive of the motor driven eyelet is adjusted based on the obtained feedback signal indicating said difference between the output speed of yarn from the motor driven eyelet and the actual weft yarn insertion speed in the weaving machine. Also, other input signals as obtained by the controller can be used as set out above. Hereby the synchronization of the movement of the eyelet and the weft yarn insertion speed can be maintained even when the weft yam insertion speed fluctuates between different insertions. In Fig. 6, a controller 22 for controlling the motor drive of the motor driving the eyelet is depicted. The controller 22 can comprise an input/output 81 for receiving input signals for parameters used for controlling the yam feeder as set out above. For example, the input signals can be various sensor signals from sensors of the yam feeder. For example, sensor signals can be provided from any type of sensor, e.g., optical sensors, mechanical sensors or capacitive sensors. Other types of input signals can also be provided such as encoder signals and the like as set out above.

Also, signals from the textile machine such as a rapier weaving machine can be input to the controller 22 and used to control the weft yam feeding arrangement. In particular, the weaving machine angle can be provided. The weaving machine angle can be used as a synchronization signal. The input/output 81 outputs motor control signal(s) to the controlled motors of the weft yarn feeding arrangement. The controller 22 further comprises a microprocessor that also can be referred to as a processing unit 82. The processing unit 82 is connected to and can execute computer program instructions stored in a memory 83. The memory 83 can also store data that can be accessed by the processing unit 82. The data in the memory can comprise pre-stored data relating to the textile machine 40. In particular for a rapier weaving machine, a model of the weft yarn insertion speed. Alternatively, rapier movements can be stored to form a model of the weft yarn speed into the rapier weaving machine. The computer program instructions can be adapted to cause the controller to control the motor accordingly. The controller 22 can be located at any suitable location. For example, the controller 22 can be integrated in the motor of the yarn feeder. The controller 22 can also be distributed at different locations either in the yam feeder or at a location outside the yarn feeder.

The above examples are for illustration only. Numerous modifications can be envisaged and the different embodiments can be combined to meet specific implementation needs.