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Title:
Yarn feeder with electrically settable yarn brake
Document Type and Number:
WIPO Patent Application WO/2017/138857
Kind Code:
A1
Abstract:
Described are, among other things,methods and devices that set a reference position for a braking element (16) used in a yarn feeder(10). The methods and devices as described herein makes it possible to know exactly the position when the braking of the yarnstarts to act and thereby establish a reference position that is known by a system that then sets the desiredbraking force electronically based on the reference position. Hereby it is possibleto have a predictable and repeatable electrically set braking force without making use of a downstream yarn tension sensor.

Inventors:
JOSEFSSON, Pär (Polonäsgränd 67, Borås, 507 65, SE)
HALVARSSON, Björn (Storgatan 78, Ulricehamn, 523 31, SE)
Application Number:
SE2017/050045
Publication Date:
August 17, 2017
Filing Date:
January 19, 2017
Export Citation:
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Assignee:
IRO AKTIEBOLAG (Box 54, Ulricehamn, 523 22, SE)
International Classes:
D03D47/34; B65H59/06
Domestic Patent References:
2002-02-07
Foreign References:
EP0534263A11993-03-31
EP0652312A11995-05-10
EP0707102A21996-04-17
US6322016B12001-11-27
EP1059375A12000-12-13
Attorney, Agent or Firm:
SANDSTRÖM & SANDSTRÖM IP AB (Boda, Sigtuna, 193 91, SE)
Download PDF:
Claims:
CLAIMS

1. A yarn feeder (10) comprising a yarn braking element (16, 30) cooperating in a flexible manner with a spool body (18) of the yarn feeder for providing a braking force acting on a yarn withdrawn from the spool body when forced against the spool body, the braking force being controllable by an electrically driven motor (20) or an actuator (35) for driving the yarn braking element towards respectively from the spool body the yarn feeder being characterized by

- means adapted to determine a reference position of the yarn braking element where the yarn braking element reaches contact with the spool body.

2. The yarn feeder according to claim 1, further comprising an input device (6) for receiving a manual input signal representing the reference position when the yarn braking element reaches contact with the spool body as determined by an operator.

3. The yarn feeder according to claim 1, wherein said means adapted to determine a reference position of the yarn braking element is a distance/position sensor adapted to automatically detect when said reference position is reached. 4. The yarn feeder according to claim 1, wherein said means adapted to determine a reference position of the yarn braking element is a sensor adapted to detect a drive current increase of the motor or actuator occurring when said reference position is reached.

5. The yarn feeder according to claim 1, wherein said means adapted to determine a reference position of the yarn braking element is a sensor adapted to detect a deformation of the brake element or an element attached to the brake element, occurring when said reference position is reached.

6. The yarn feeder according to any of claims 1 - 5, further comprising a memory for storing the reference position.

7. The yarn feeder according to any of claims 1 - 6, further comprising a movement sensor or a position sensor adapted to sense the movement or position caused by the electrically driven motor/actuator in relation to said reference position.

8. A control system (1) for controlling the yarn tension in at least one yarn feeder according to any of claims 1 - 7, the control system comprising a central controller (2) adapted to electrically set a desired braking force of each of said at least one yarn feeders based on a determined reference position.

9. The system of claim 8, wherein a look-up table for storing reference positions is located in said central controller.

10. The system of claim 9, wherein the system is adapted to up-date the look-up table based on input received from anyone of said at least one yarn feeder.

Description:
Yarn feeder with electrically settable yarn brake

TECHNICAL FIELD

The present disclosure relates to a yarn feeder. In particular the present disclosure relates to control of a brake element in a yarn feeder for textile machines to electronically regulate the tension of the yarn taken from the feeder.

BACKGROUND

Yarn feeders are used to eliminate yarn tension variations to ensure high quality and also to supply the correct amount of yarn to a textile machine, e.g. a shuttleless weaving machine or knitting machine. Hereby textile quality and productivity of the textile machine can be increased.

One feature of a yarn feeder is to provide a suitable yarn tension for the yarn fed to a weaving machine, e.g. a rapier weaving machine. The yarn tension applied can be provided in different manners. For example, a frustum-conical braking element can be used that cooperates with the spool body rim to create an essentially constant braking force, see EP 0 534 263. The force that the braking element exercises can alternatively be controlled by an electro-magnetic actuator to continuously vary over time to take into account desirable variations in the required braking force as is for example described in EP 0 652 312. Also, the braking force applied can be controlled by an electric motor, such as a step motor, see EP 0 707 102. It is further possible to use a yarn tension sensor to keep the braking force desirably constant alternatively desirably varying over time.

There is a constant desire to provide improved yarn feeders. 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. This object and/or others are obtained by the yarn feeder as set out in the appended claims.

The use of an electrically settable braking force is advantageous since the setting can be made remotely. However, existing systems require the use of a downstream yarn tension sensor for feedback of the achieved, actual yarn tension. The use of such a yarn tension sensor can in many systems result in a system that is too expensive. Also the use of such a yarn tension sensor will lead to a deviation of the yarn over the probe of the tension sensor resulting in added tension that can negatively impact the yarn and/or the quality of the fabric produced by the textile machine. Hence, it would be advantageous to be able to provide a yarn feeder that can be remotely controlled without having to use a downstream yarn tension sensor and its feedback information.

However, such a system would require that the electrically settable brake has at least one known reference value that can be used as a reference position for a device used to control the braking force.

In accordance with a first aspect of the invention there is provided a system and a method whereby a reference position for an electrically settable yarn brake is provided. The use of a reference position makes it possible to remotely set the braking force without having to use a downstream yarn tension sensor.

In accordance with a second aspect of the invention the system and method used to obtain said reference position for an electrical settable yarn brake is configured to be used during start up of a system for a textile machine, having a downstream yarn tension sensor, in which system there can be a need to determine a start value for the setting of the yarn tension, before any feedback information from the yarn tension sensor is received.

In accordance with one embodiment a yarn feeder comprising a yarn braking element cooperating in a flexible manner with a spool body of the yarn feeder is provided. The yarn braking element will provide a braking force acting on a yarn withdrawn from the spool body, when forced against the spool body. The braking force is controllable by an electrically driven motor or an actuator for driving the yarn braking element towards respectively from the spool body. The yarn feeder further comprises means, such as a reference position determinator, adapted to determine a reference position of the yarn braking element where the yarn braking element reaches contact with the spool body.

In accordance with one embodiment an input device for receiving a manual input signal representing the reference position when the yarn braking element reaches contact with the spool body, as determined by an operator, is provided.

In accordance with one embodiment the means adapted to determine a reference position of the yarn braking element is a distance/position sensor adapted to automatically detect when said reference position is reached.

In accordance with one embodiment the means adapted to determine a reference position of the yarn braking element is a sensor adapted to detect a drive current increase of the motor or actuator, occurring when said reference position is reached. In accordance with one embodiment the means adapted to determine a reference position of the yarn braking element is a sensor adapted to detect a deformation of the brake element or an element attached to the brake element, occurring when said reference position is reached. In accordance with one embodiment a memory for storing the reference position is provided in the yarn feeder. In accordance with one embodiment a memory for storing the reference position is provided in a unit remote from the yarn feeder. In accordance with one embodiment the yarn feeder comprises a sensor adapted to sense the movement or position caused by the electrically driven motor/actuator in relation to said reference position.

In accordance with another aspect a control system for controlling the yarn tension in at least one yarn feeder as set out above is provided. The control system comprises a central controller adapted to electrically set a desired braking force of each of said at least one yarn feeders. The control is based on a determined reference position.

In accordance with one embodiment a look-up table for storing reference positions is located in the central controller. In accordance with one embodiment the system is adapted to up-date the look-up table based on input received from anyone of said at least one yarn feeder.

The invention also extends to methods for controlling a yarn feeder in accordance with the above and to a computer program product that when executed on a computer causes the computer to execute a program implementing the method.

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. 1 is a view illustrating a yarn feeder,

- Fig. 2, is a view of a detail of a yarn feeder, - Fig. 3 is a view illustrating a system for controlling the yarn tension for a number of yarn feeders, and - Fig. 4 is a flow chart illustrating steps performed when controlling yarn tension.

- Fig. 5 is a view of an alternative braking means.

- Fig. 6 is illustrating a yarn feeder with an electronic yarn tension actuator.

- Fig. 7 is illustrating an alternative execution of a yarn feeder with an electronic yarn tension actuator.

DETAILED DESCRIPTION

In Fig 1, a yarn feeder 10 is depicted. In the yarn feeder 10 of Fig. 1 an extension arm 12, usually called top cover in the field of yarn feeders, is arranged extending from a housing 14 for example as described in US 5,947,403. The yarn feeder 10 comprises a yarn braking element 16, which is shown in Fig. 1 in its braking position. The yarn braking element 16 can for example be a frustum conical element 16, but can be also be of another type or shape. The braking element can be made of a plastic material such as PEEK or PET. The braking element 16 can be or be arranged flexible. The flexible manner in which the braking element cooperates with the spool body can be achieved in different ways. The flexibility can be achieved by having the braking element 16 suspended by springs and/or the braking element can be made, at least in part, of a flexible/elastic material that is deformed when the braking element is forced against the spool body or the flexibility can be provided in some other manner. The flexible action of the braking element cooperating with the spool body can hence be of any conventional type and is not discussed in more detail herein. The yarn braking element 16 cooperates in a customary manner with the withdrawal rim of the spool body 18. The yarn braking element 16 can thus be moved back and forth along an axis A to control the braking force applied to a yarn withdrawn from the yarn feeder 10. In one embodiment the yarn braking element 16 can be attached to the extension arm 12 via, an along the axis A slidable brake element holder 27 provided at the extension arm 12.

In Fig. 1, the yarn braking element 16 is in the braking position in which it is axially pressed with a predetermined, settable axial force against the spool body 18. This position can be changed by running a motor of a brake motor assembly 20 to vary the contact pressure of the yarn braking element 16, by making the brake element holder 27 move along the axis A in a manner known per se.

In order to enable an electrically controlled setting of the brake force without the use of a downstream yarn tension sensor, a reference position in which the position of the braking element corresponds to a known braking force needs to be established. In accordance with one embodiment a position where the braking force just starts to act is established. In such a position there will be a braking force, but the braking force will have a very small magnitude that will not impact the yarn tension in any significant way. Such a position can be called a 0-position of the braking element or initial braking position. In other words, this is the position where the braking element just comes into contact with the spool body. This position can be saved in a memory to establish a reference position that can be used when electrically controlling the braking force. The memory can be located in the yarn feeder or it can be located at another position such as in a control system arranged separately or integrated in the textile machine.

A number of methods can be used to determine such an initial braking position. In accordance with one first embodiment, the initial braking position can be determined manually. For example, a thin instrument (not shown in the drawings), e.g. an ordinary gauge in the form of a thin sheet of metal or plastic, typically about 0.1 mm thick or less can be placed in the gap between the braking element 16 and the spool body 18. The braking element 16 is then driven towards the spool body 18 by for example actuating a pushbutton 5 and when the braking element squeezes the instrument between the braking element and the spool body so that it no longer can be removed without use of an additional force, a manual command is given into the memory by actuating a 0-setting pushbutton 6 to set the initial braking position. The initial braking position can also be set by simply visually looking at the braking element 16 when it precisely reaches the spool body 18 and set the initial braking position into the memory accordingly. There can also be a pushbutton 7 to move the brake holder 27 in direction from the spool body. In an alternative execution, the pushbuttons 5, 6 and 7 can be located at the Human Machine Interface (HMI) on a central control unit, for example in the machine terminal of a textile machine.

In a second embodiment, a sensor is provided to detect a movement of the braking element 16 when the motor 20 is run to move the braking element towards the spool body. When the braking element 16 does not move anymore but the motor 20 still runs, this indicates that the braking element has hit the spool body and the initial braking position can be set as the position when the sensor first detects no movement with the motor still running. The sensor can be any type of sensor that detects a movement. The sensor can for example be of optical type, sensing the distance between the movable braking element holder and the cone. The sensor can also be of the magnet - Hall sensor type, or an inductive sensor. A sensor insensitive for dust is typically advantageous.

In Fig. 2, showing a detail of the yarn feeder 10 of Fig. 1, a possible setup with such a movement sensor is depicted. In Fig. 2 a Hall sensor 25 is used together with a permanent magnet 24. The Hall 25 sensor is located at the moving brake element holder 19 and the magnet 24 is attached to the braking element 16. As alternative the Hall sensor can be located at a fixed location on the yarn feeder 10 and the permanent magnet 24 is attached to the moveable braking element 16.

In a third embodiment the motor torque of the motor 20 used to move the braking element 16 is monitored. When the motor torque increases this signals that the braking element 16 has precisely reached the spool body 18 and started to stretch some elastic element of the braking element such as the springs 26 shown in Fig. 2. The position where the motor torque starts to increase is set in the memory as the initial braking position.

In a fourth embodiment a sensor that detects deformation of an elastic part of the braking element 16 can be used when determining the initial braking position. In such an

embodiment a sensor is provided to sense when some part of the braking element starts to be deformed and use that moment as having precisely reached the initial braking position. For example, if the braking element 16 is provided with springs 26 that are stretched when the braking element hits the spool body a sensor sensing that the spring 26 is stretched can be used to set the initial braking position.

In Fig. 5 a further embodiment of the Hall sensor - permanent magnet type of solution is depicted. In the embodiment according to Fig. 5 another type of braking element is used. The braking element 30 is of a type known for example in EP 0963335 and is made of an elastomer, for example polyurethane. The Hall sensor 32 is located at a fixed location of the yarn feeder 10, and the permanent magnet 31 is attached to the brake element 30.

In Fig. 6 a further embodiment is shown. In accordance with the embodiment shown in Fig. 6 an actuator 35, for example an electromagnet or electrical motor, is used to apply the braking force to a brake holder 38 which in turn transfers the force via the springs 26 to the braking element 16. The actuator 35 can be position-controlled and has a

movement/position sensor, for example a Hall sensor 36 co-acting with a permanent magnet 37. When the actuator starts to move to apply force, both the Hall sensor 36 and the Hall sensor 25 detect movement. When the braking element 16 comes in contact with the spool body 18 the Hall sensor 25 detects that the permanent magnet 24 is not moving anymore, while the Hall sensor 36 of the actuator 35 still detects movement, and this is then used as the indication that the 0-position of the braking element is reached.

Fig. 7 shows a further embodiment. In the embodiment of Fig 7an actuator 35, for example an electromagnet or electrical motor, is used to apply the braking force to the brake holder 38 which in turn transfers the force via springs to the braking element 16. The actuator can be position-controlled and has a movement/position sensor, for example a Hall sensor 36 and a permanent magnet 37. When the actuator starts to move to apply force the Hall sensor 36 detects movement. When the braking element 16 comes in contact with the spool body 18, the current used to drive the actuator 35 will increase. A sensor, for example in the drive circuit, is used to monitor the drive current and is correlating the actual current with the actual position of the actuator, detected by the Hall sensor 36 and the permanent magnet 37. When the drive current starts to increase this is then used as the indication that the 0- position of the braking element is reached.

When a reference position such as the initial braking position (0-position of the braking element) has been determined, the desired braking force is then set based on this reference position. In accordance with one embodiment the desired braking force is set as a percentage of the maximum force applicable. The desired braking force can in accordance with another embodiment be set in relation to the range of movement when the motor or actuator drives the braking element towards (and from) the spool body.

For example, in case the motor is a stepper motor, the number of steps relative to the reference position can be used to control the braking force. In accordance with another example, when the motor is a DC motor, an encoder or another sensor can be used to detect the rotation of the motor respectively the axial movement of the brake element holder 27, thus determining the braking force and thereby the yarn tension. Either the sensor is of absolute type, or a relative type of sensor. In case of relative type of sensor, a homing position can be needed and provided.

An alternative to an encoder is to have a rotating magnet and two Hall sensors with a relative position between each other, e.g. 90 degrees inter-distance can be used. This will form two sinusoidal signals 90 degrees separated, thus providing a good angle sensor. One can typically extract up to 10-15 positions per revolution with good resolution for this system. Another type of sensor that can be used in a similar manner to generate the corresponding functionality is a so called rotary magnetic sensor chip.

Knowing the case- specific parameters it is possible to set the desired yarn tension based on the found and stored initial position value (0-position of the braking element) without the use of a downstream yarn tension sensor. This can for example be done using a look-up table that has desirable values (set-values) for various combinations of yarn

tension/yarn/weaving machine type, width and speed/braking element/ type of yarn feeder (or any desired sub-set of such parameters). By locating the look-up table in a central control system it is possible to remotely control a number of yarn feeders from one single location.

In Fig. 3, a control system 1 for controlling the yarn tension of a number of yarn feeders 10 is depicted. The control system comprises a central controller 2 connected to each of the yarn feeders 10 of the system. The controller 2 can comprise a memory 3 storing a look-up table as set out above and a control unit 4 adapted to control the braking force of the yarn feeders 10 to which it is connected either by wire or wirelessly. Hereby it is obtained that the yarn tension for a number of yarn feeders can be set remotely from a single central location. For example, if one particular setting of the yarn tension yields a good

performance of the textile machine, this setting can be saved in the look-up table and reused for other yarn feeders running the same "textile application". Thus, in some embodiments the system is adapted to apply a self-learning algorithm that saves useful settings for one machine and enables re-use of that setting for the same machine or for a machine having the same configuration. The controller and/or the memory can in one embodiment be located in the weaving machine or knitting machine, and the weaving machine terminal (HMI) can be used to monitor and enter settings.

In Fig. 4 a flow chart illustrating some procedural steps that can be performed when controlling the yarn tension in accordance with the teachings hereinabove is shown. First, in a step 401, the braking element is driven towards the spool body in a state where there is no braking force. Next, in a step 403, a position is determined when the braking element just reaches the spool body and thus makes contact with the spool body. The position determined in step 403 is saved as a reference position, in a step 405. Then, the braking force, and thereby the yarn tension is controlled by measuring how an electrically driven motor or actuator drives the braking element in relation to said reference position in a step 407.

By using the methods and devices as described herein it is made possible to know exactly the position when the braking of the yarn starts to act and thereby establish a reference position that is known by a system that then sets the desired braking force electronically based on the reference position. Hereby it is possible to have a predictable and repeatable electrically set braking force without making use of a downstream yarn tension sensor.