Yarn sensor assembly

Abstract

Described are, among other things, a yarn sensor assembly (10) comprising a yarn deflection element (16) configured to move in response to a yarn (50) pressing on the yarn deflection element (16). The sensor assembly comprises a first sensor (30) of a first type configured to produce a first output signal responsive to the position of the yarn deflection element (16), where the first output signal is indicative of a first yarn condition, and a second sensor (40) of a second type, where the second sensor is of a different type than the type of the first sensor, and where the second sensor is connected to the yarn deflection element (16) and configured to produce a second output signal responsive to the vibration of the yarn deflection element (16), and where the second output signal being indicative of a second yarn condition.

Description

The present disclosure relates to a yarn sensor assembly.BACKGROUNDIn textile machines, such as weaving machines, knitting machines, tufting machines, warping machines, winding machines and also other types of textile machines, different sensors for detecting and monitoring different yarn conditions during the production of a textile are typically used. The type of yarn condition can vary between different textile machines.For example, in modem weaving machines a filling detector is typically provided. The task for a filling detector is to supervise the insertion of a weft yarn (also called filling) in a weaving machine. Thus, during insertion the weft yarn into the weaving machine, the yarn can break, or the rapier on a rapier weaving machine can lose the yarn. The task for a filling detector is to sense the motion of yarn. There should be motion of the weft yarn during the whole insertion, all the way until the yarn has reached the other side of the weaving machine. When the yarn does not reach the other side of the weft, it is important to detect this. At a yarn break or a rapier losing the yarn, it is hence essential to stop the machine very fast, even before next yarn insertion is started, to not have a defect in the woven fabric produced by the weaving machine.Also, on other textile machines used to produce a textile like knitting machines, warping machines, winding machines and tufting machines there is a need to supervise that the yarn moves as specified and is not broken or entangled.A filling detector is traditionally based on a piezo sensor. A piezo sensor detects vibrations in the yarn that occurs when the yarn is sliding over a ceramic eyelet. A piezo sensor generates small changes in electrical charge in the piezo element when compressed or released. Such sensors are known from for example EP1157150.The filling detectors can traditionally be configured in two ways. Either as a combined set (an array) of eyelets at the input to the weaving machine, or as single sensors, one for each insertion channel. The single sensor is commonly placed on the outlet side of the weft yarn feeders, and the array sensors are placed on the weaving machine itself.Modem weaving machines also in some cases have a yarn tension sensor. The task for a yarn tension sensor is to monitor the tension of the weft yarn during insertion of yarn into the weaving shed. The information from the measured yarn tension can be used to control a yarn brake in a closed or open loop control system. It can also be used to monitor the weaving process and optimize settings, notify the operator or provide information for use in a machine learning system, or an AI system. Yet another use is to enable transfer of settings from one weaving machine to another, or from a setting card when repeating a setting at a later point in time. To serve these demands, the yarn tension sensor needs to be of absolute type and fast. It is then important that all yarn tension sensors give the same output signals for the same actual yarn tension within a narrow tolerance. The yarn tension sensor must also be stable in time, and have no or only very limited drift in time and by temperature. In other words, at a yarn tension of for example 20 cN, all yarn tension sensors for a complete system must show for example 20 cN / - 1 cN, independent from changes in environment and age of the yarn tension sensors.Similar to the above, a yarn tension sensor is commonly used in other types of textile machines such as knitting machines, warping machines and tufting machines.A yarn tension sensor is traditionally based on a thin plate or pin that is bent by the yarn when the weft yarn is deflected over the edge of the plate (or pin). The sensing element can be of for example strain gauge type. This type of yarn tension sensor is known from for example EP1766355.Further, in some applications two tasks can be combined in one device.For example, SE520804 and SE517299 describe combined sensors. Here a piezo sensor is used for both detecting yarn brakes and yarn tension for a sewing machine. Other examples are BE1014762,. EP1377513, DE102004026859 and US4228828.There is a constant desire to improve yarn feeding to textile machines. Hence, there is a need for an improved yarn sensor assembly to be used when feeding yarn to a textile machine.SUMMARYIt is an object of the present invention to provide an improved yarn sensor assembly.This object and / or others is / are obtained by the yarn sensor assembly as set out in the appended claims.As has been realized by the inventors, existing set ups for determining and / or monitoring different yarn conditions when feeding yarn to a textile machine can be improved.For example, both the filling detector and the yarn tension sensor as used in many textile machines are based on yarn deflection to provide an output signal. Each deflection of the yarn will however generate extra yarn tension which in turn increases the risk of yarn brake or a rapier losing the yarn. Each yarn deflection also generate dust from the yarn which is another disadvantage. For example, both a yarn tension sensor and a filling detector need a deflection of 10 to 20 degrees and if both are used, it results in a combined deflection of about 20 to 40 degrees.As a result, the use of both yarn tension sensors and filling detectors on the same machine is today strongly limited due to the negative impact from the extra deflection on the yarn, and from the high cost of two sensors / detectors.However, existing solutions to combine two functions in one sensor with only one deflection point are not possible to use in textile machines where an absolute reading is demanded, and no phase in the machine cycle where a zero setting can be made exists. This is for example the case for most textile machines including but not limited to weaving machines, knitting machines, warping machines and tufting machines.There have been attempts to combine the two tasks in one sensor. However, as has been realized existing devices cannot be used in textile machines where an absolute reading is demanded.For example, SE520804 and SE517299 describe combined sensors. Here a piezo sensor is used for both detecting yarn brakes and yarn tension for a sewing machine. A sewing machine differs from most other textile machines like weaving machines, knitting machines and winding machines. In a sewing machine each machine cycle to generate a stitch contains a phase where the yarn tension is zero, that is the yarn is not generating any force on the sensor. As the principle of a piezo sensor is that it changes the electrical charge when compressed or released, the change in charge can be used as an indication of the mechanical force, i.e. yarn tension only as a difference in load from one point in time to another. In a sewing machine where the load is zero in each machine cycle this works. In other textile machines however, the yarn tension is never zero during running. In for example weaving, the yarn tension varies during the insertion and is also present during beat up and when other yarns are inserted during the weaving pattern. Consequently, as the yarn tension is never released to zero tension, the yarn tension signal from a piezo sensor will drift away when used in a weaving machine. Further, a piezo sensor is very difficult to use as an absolute yarn tension sensor. It can only give an indication of the absolute yarn tension with a rather big variation from sensor to sensor. As described above, in most textile machines like weaving an absolute sensor is typically required. Accordingly, US4228828, using two different piezo sensors to detect yarn motion and yarn tension will also not provide an absolute yarn tension signal and consequently not fulfill the needs of a modem textile machine like a weaving machine.Further, as has been realized, generating a yarn motion signal from a yarn tension sensor based on strain gauge or other principles like Hall sensor, capacitor sensor, optical sensor as described in BE1014762, which describes a sensor that combines yarn tension and yarn movement with a single signal emitter, is associated with problems. Thus, due to the principle of bending or moving a plate or pin with a relatively big moving mass, the sensor is too slow to detect a stop in yarn motion and stop the textile machine in time to prevent an error in the textile fabric.Other known solutions combining two sensors in one housing are also associated with problems. For example, in EP1377513 each of the two sensor pins needed here, both need a deflection angle. Therefore, the sum of yarn deflection will be doubled and the same problem as with two separate sensors is present.In accordance with the present invention a yarn sensor assembly is provided. The yarn sensor assembly comprises a yarn deflection element configured to move in response to a yarn pressing on the yarn deflection element. The yarn sensor assembly further comprises a first sensor of a first type configured to produce a first output signal responsive to the position of the yarn deflection element where the first output signal being indicative of a first yarn condition. The yarn sensor assembly also comprises a second sensor of a second type, where the second sensor is of a different type than the type of the first sensor, the second sensor is connected to the yarn deflection element and configured to produce a second output signal responsive to the vibration of the yarn deflection element caused by the yarn motion, such that the second output signal is indicative of a second yarn condition. Hereby detection of multiple yarn conditions with a low angle of deflection of the yarn and at the same time an absolute reading of a yarn deflection element can be obtained. Further, a compact design and lower cost can be obtained as many parts are common for a plurality of sensors.In accordance with one embodiment, the first sensor is configured to output a signal indicative of yarn tension. Hereby a useful implementation of the yarn sensor assembly can be provided.In accordance with one embodiment, the first sensor is of an absolute type. Hereby, accurate reproduction of yarn conditions such as yarn tension can be obtained.The first sensor can for example be a Hall type sensor. The Hall type sensor can be configurable. For example, parameters such as zero setting, linearization, temperature compensation and range can be set in the Hall type sensor itself.In accordance with one embodiment the first sensor is a strain gauge type sensor.In accordance with one embodiment, the second sensor is configured to output a signal indicative of yarn motion. The second sensor can be a piezo type sensor.In accordance with one embodiment, the second sensor is an accelerometer type sensor.In accordance with one embodiment, the yarn deflection element is suspended by at least one elastic member.In accordance with one embodiment, the second sensor is placed at a non-moving part of the yarn deflection element.In accordance with one embodiment, the yarn deflection member is movable in two dimensions.BRIEF DESCRIPTION OF THE DRAWINGSThe 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 sensor assembly in a perspective view,- Fig. 2 is a side view of a yarn sensor assembly,- Fig. 3 is a cross sectional view of a yarn sensor assembly,- Fig. 4 is a partial view in perspective of some components of a yarn sensor assembly, and - Fig. 5 illustrates configuration of a Hall sensor,- Fig. 6 is a view illustrating a two-dimensional yarn sensor assembly in a perspective view.DETAILED DESCRIPTIONIn the following a yarn sensor assembly is 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, a yarn sensor assembly comprising one single yarn deflection element and two sensors of different types is provided. The yarn deflection element can move in response to a pressing force and the position of the yarn deflection element can be determined by a first sensor and vibrations in the deflecting element can be determined by a second sensor. For example, one sensor specialized for yarn motion and one sensor specialized for yarn tension. The detector for yarn motion can for example be of piezoelectric type, as is known from filling detectors today. It can also be an accelerometer, interferometer etc. The sensor for yarn tension can be of strain gauge type, or Hall sensor type, or optical or laser type, or any other suitable type of sensor for determining the position of the yarn deflection element.In Fig. 1, an exemplary yarn sensor assembly 10 is shown in a perspective view. The yarn sensor assembly 10 comprises a housing 20. The housing 20 can be suspended by at least one elastic member. The yarn sensor assembly 10 further comprises a first guiding eyelet 12 at a first end of the yarn sensor assembly 10 and a second guiding eyelet 14 at the opposite side of the yarn sensor assembly 10. The sensor assembly 10 further comprises a yarn deflection element 16. The yarn deflection element is configured to move when a yarn 50 is applying a pressing force onto the yarn deflection element 16. For example, the yarn deflection element 16 can be a bendable plate such as a metal plate, ceramic plate, or a spring biased member that can move when pressed upon.For example, when a yarn 50 is positioned through the first guiding eyelet 12, over the yarn deflection element 16 and out via the second guiding eyelet 14, the yarn 50 can be under tension and then apply a pressing force onto the yarn deflection element 16.In Fig. 2, a side view of the yarn sensor assembly 10 is shown. In Fig. 2, there is tension on the yarn 50 running over the yarn deflection element 16 such that the yarn deflection element is bent. The bending (movement) of the yarn deflection element 16 can be sensed by a first sensor 30 of the yarn sensor assembly 10. Thus, the first sensor 30 can be used to determine the position of the yarn deflection element 16. The position of the yarn deflection element 16 corresponds to the pressure force placed on the yarn deflection element 16 by the yarn 50. The pressure force is in turn related to the tension of the yarn 50 that runs over the yarn deflection element 16.In Fig. 2, the first sensor 30 is of a Hall type. When the first sensor 30 is of a Hall type a magnet 32 can be provided on the yarn deflection element 16. The magnet can advantageously be located where the movement of the yarn deflection element 16 is the largest such as on the tip of the yarn deflection element 16 in the exemplary embodiment of Fig. 2. The first sensor can also be of some other type that can detect a position or movement of the yarn deflection element 16 such as a strain gauge type, or optical or laser type of sensor.Further, as the yarn 50 runs over the yarn deflection element 16, a pressure force will be applied onto the yarn deflection element 16 by the tension of the yarn 50. The yarn 50 will then be deflected over the yarn deflection element 16 to provide the pressure force. To reduce the wear from the yarn 50, a contact member 18 can be provided on the yarn deflection element 16. The contact element 18 can typically be provided on the tip of the yarn deflection element 16 or where the yarn 50 contacts the yarn deflection element 16. The contact element 18 can for example be made of a ceramic material or some other wear resistant material with low friction against the yarn 50.In Fig. 3, a cross-sectional view of the yarn sensor assembly 10 of Fig. 2 is depicted. In Fig. 3, a second sensor 40 is shown. The second sensor 40 is connected to and can typically be placed on the yarn deflection element 16. In accordance with one embodiment the second sensor 40 is placed on a non-moving part 16a of the yarn deflection element 16. For example, as is shown in Fig. 3, the yarn deflection element 16 can be fixed at one section and be movable in an end section. In such an embodiment, the yarn deflection element 16 can be configured to bend at a fulcrum. By placing the second sensor 40 on a nonmoving part of the yarn deflection element 16, the second sensor 40 will not add to the moving mass of the yarn deflection element 16. The second sensor 40 can be configured to generate an output indicative of vibrations in the yarn deflection element 16. The second sensor 40 can for example be a piezo type sensor or an accelerometer, or an interferometer or a similar sensor that can be used to detect vibrations.In Fig. 4, a partial view in perspective of the yarn sensor assembly 10 is shown. In Fig. 4, the yarn deflection element 16 is shown suspended by at least one elastic member. In the embodiment of Fig. 4 two elastic members 22, 24 are provided. In accordance with the embodiment Fig. 4, one elastic member 22, 24 is located at each side of the yarn deflection element 16. Further, in accordance with the embodiment shown in Fig. 4, the elastic members 22, 24 can be located on the non-moving part 16a of the bendable element. The elastic members 22, 24 can be formed by a material softer than other parts holding the yarn deflection element 16 of the yarn sensor assembly 10 so as act to reduce or remove vibrations not originating from the yarn deflection element 16. The elastic members 22, 24 are provided to remove vibrations from the environment, such that the second sensor 40 only detects yarn vibrations caused by the yarn 50 running over the yarn deflection element 16 and not ambient vibrations. In some embodiments, the second sensor 40 can be located on a part of the yarn sensor assembly that holds the yarn deflection element 16. In such an embodiment, it can be advantageous to suspend the housing 20 that holds the deflection element 16 by elastic member(s).Thus, the yarn sensor assembly 10 comprises two sensors 30, 40 and a yarn deflection element 16 configured to move in response to a yarn 50 having a yarn tension running on the yarn deflection element 16. A first sensor 30 can be of a first type and configured to produce a first output signal responsive to the bending of the yarn deflection element 16. The output signal from the first sensor 30 can be indicative of a first yarn condition.The yarn sensor assembly 10 further comprises a second sensor 40 of a second type. The second sensor is of a different type than the type of the first sensor, and the second sensor is connected to the yarn deflection element 16 and configured to produce a second output signal responsive to vibration of the yarn deflection element 16, the second output signal being indicative of a second yarn condition.The first sensor 30 can advantageously be of absolute type. Thus, the sensor 30 is in accordance with some embodiments of a type that provides an unambiguous position or measurement value of the yarn deflection element 16, which does not require any referencing or recalibration. It can further advantageously be designed to give a consistent and accurate reading of the absolute position or value it is measuring, even after a power loss and other events. When using such a sensor of an absolute type the same yarn tension can then typically give the same reading independent of different ambient conditions, such as ambient temperature, heating, aging and similar conditions. One type of sensor that can be used to fulfill such requirements is a Hall sensor 30.The first yarn sensor 30 can be a Hall sensor. In accordance with some embodiments, the Hall sensor 30 can be a programable Hall sensor. In other words, the Hall sensor is configurable into different configurations. The programable Hall sensor 30 can be configured to perform calibration of the Hall sensor. Hereby calibration can be made faster, easier and without introducing other components.In accordance with one exemplary embodiment one or more of the following steps are performed in a calibration procedure. The steps are illustrated in Fig. 5.First, in a step 501, the gain or range is set to a predetermined value, for example 25 mT (milli Tesla) to have a start value in the calibration procedure. Also, in order to check the mechanics of the yarn tension sensor a test force / a set of test forces can be applied on the mechanical element, here the yarn deflection element 16, used to determine yarn tension. For example, a low or no force such as 0 cN and a higher force such as 200 cN can be applied. It is checked that the output signal for the applied test forces is at acceptable levels as set by some pre-determined reference value. If not, it is determined that that the mechanics used is mal-functioning and the procedure can output an error signal indicating a mechanical mal function.Next, in a step 503, temperature compensation is set according to pre-determined values defined in lab tests. The Hall sensor typically has an inbuilt temperature sensor that can provide for a temperature compensation. A temperature compensation coefficient can be set in a temperature compensation step. The temperature compensation coefficient can advantageously be determined in advance. For example, a lab test for a number of Hall sensors can be performed in order to determine a pre-determined temperature coefficient that can be applied to all Hall sensors when in use. In other words, some average value for the temperature coefficient can be applied to all Hall sensors instead of an individual temperature coefficient for each Hall sensor.Then, the calibration can be performed in a step 505. In the calibration, the output signal from the Hall sensor is calibrated to be between two predetermined output voltage levels (V) for two specified loads. For example, 0 V for 0 load and 4 V for 200 cN. To have a high accuracy in the calibration it is preferred to use calibration points at, or close to, the min and max levels for the sensor. In other words, using the whole measuring range of the sensor in the calibration. In Step 505 different parameters can be set. For example, the sensing range of the Hall sensor can be configured. For example, the end points such as the minimum yarn tension, typically zero and the maximum yarn tension. In other words, calibration of end points can be performed by performing calibration of sensing range end points. Here zero tension can be set to minimum output voltage. For example, 0g is set to IV, and maximum tension is set to maximum output voltage. For example, 200g is set to 4V.Next, in a step 507, a linearization can be performed. In the liberalization procedure linearization of the output signal between sensing range end points can be performed. Here, a number of data points can be entered to compensate for the not linear behavior of the Hall sensor. For example, the deviation from a straight line can be measured and compensation values calculated and tested, either in lab environment and used for a plurality of Hall sensors or measured in a calibration equipment during production. For example, a plurality of forces of different magnitudes are applied during the process and the response from the Hall sensor is checked. To have a good linearization at least two data points are used and preferably more than two such as at least five data points. For example, the forces 0, 50, 100, 150, 200 cN can be applied in the above example. Typically, specific values for each sensor can then be used. By this calibration process, an absolute yarn tension sensor is obtained.In Fig. 6, a yarn sensor assembly 31 according to another embodiment is shown. In the embodiment of Fig. 6, the yarn sensor assembly 31 comprises a yarn deflection member formed as an eyelet 41. The eyelet 41 can for example be made of a ceramic material to increase wear resistance and reduce friction. The eyelet 41 can be suspended in two dimensions in a plane. For example, springs 42 can be provided to suspend the eyelet such that the eyelet 41 can move in any direction in a two-dimensional space.The position of the eyelet 41 can be determined by some kind of position sensor. In the embodiment of Fig. 4, two Hall sensors 43, 44 are provided for the eyelet 41. Magnets 46, 47 can be provided on the eyelet 41 to enable the Hall sensors to determine the position of the eyelet 41. The two Hall sensors 43, 44 are configured to determine the position in two different dimensions, respectively. The combined position as given by the Hall sensors 43,44 then give the two-dimensional position of the eyelet 41. The position of the eyelet corresponds to the force applied onto the eyelet by the tension of a yarn that runs through the eyelet 41.In such an embodiment, the yarn 50 can enter the eyelet 41 from any angle depending on the position of a yarn feeder in relation to yarn sensor assembly 31. The eyelet 41 is mounted in a plane that allows the eyelet 41 to move in the same direction as the force caused by the yarn tension acts.The movement of the eyelet 41, and thus the yarn tension, is measured with the appropriate sensor(s) in two dimensions (X & Y). The resultant of the forces gives a measure of the yarn tension.To measure the yarn tension, suitable distance / position sensors can be used, such as Hall sensors / magnets as in the embodiment of Fig. 6. Other sensors that can be envisaged comprise but is not limited to, optical sensors (one or two-dimensional), inductive or capacitive sensors. Alternatively, the force / deflection in the spring element that holds the yarn eyelet can be measured with, for example, a strain gauge.Further, a second sensor 48 for detecting vibrations can be fixed onto the eyelet. The vibrations can be used to determine yarn motion. The second sensor 48 for detecting vibrations can for example be a piezo sensor. The yarn sensor assembly 31 can act as both a yarn tension sensor and yarn motion sensor, where the yarn deflection member 41 can move in two-dimensions.Using the yarn sensor assembly 10, 31 as described herein can enable detection of multiple yarn conditions with a low angle of deflection of the yarn and can at the same time enable an absolute reading of a bendable element 16 in order to enable accurate reproduction of yarn conditions such as yarn tension. Further, a compact design and lower cost can be obtained as many parts are common for a plurality of sensors. Yet another advantage with the yarn sensor assembly as described herein is that the threading up of a new weft yarn after a yarn break will be faster as only one sensor device instead of two have to be threaded.The yarn sensor assembly as described herein can be either made as a single yarn sensor assembly and placed for example at the outlet of a yarn feeder, or as a multiple yarn sensor arrangement comprising a plurality of yarn sensor assemblies placed for example at the weaving machine before the filling presenters, typically at the same position as the filling detector today are normally placed in a conventional set-up.The above examples are for illustration only. Numerous modifications can be envisaged and the different embodiments can be combined to meet specific implementation needs.

Claims

1. A yarn sensor device (10, 31) comprising:- a yarn deflection element (16, 41) configured to move in response to a yarn (50) pressing against the yarn deflection element (16, 41),- a first sensor (30, 43, 44) of a first type, configured to generate a first output signal dependent on the position of the yarn deflection element (16, 41), the first output signal being indicative of a first yarn condition, characterized by- a second sensor (40, 48) of a second type, the second sensor being of a different type than the first sensor, the second sensor being attached to the yarn deflection element (16, 41) and configured to generate a second output signal dependent on the vibration of the yarn deflection element (16, 41), the second output signal being indicative of a second yarn condition.

2. The yarn sensor device (10, 31) according to claim 1, wherein the first sensor (30, 43, 44) is configured to output a signal indicative of yarn tension.

3. The yarn sensor device (10, 31) according to claim 1 or 2, wherein the first sensor (30, 43, 44) is of absolute type.

4. The yarn sensor device (10, 31) according to claim 2 or 3, wherein the first sensor (30, 43, 44) is a Hall-type sensor.

5. The yarn sensor device (10, 31) of claim 4, wherein the Hall-type sensor is a configurable Hall sensor.

6. The yarn sensor device (10, 31) according to claim 2 or 3, wherein the first sensor (30, 43, 44) is a strain gauge type sensor.

7. The yarn sensor device (10, 31) according to any one of claims 1-6, wherein the second sensor (40, 48) is configured to emit a signal indicative of yarn movement.

8. The yarn sensor device (10, 31) of claim 7, wherein the second sensor (40, 48) is a piezotype sensor.

9. The yarn sensor device (10, 31) of claim 7, wherein the second sensor (40, 48) is an accelerometer type sensor.

10. The yarn sensor device (10, 31) according to any one of claims 1-9, wherein the yarn deflection element (16) is suspended from at least one elastic element (22, 24).

11. The yarn sensor device (10) according to any one of claims 1-10, wherein the second sensor (40) is located at a non-moving part (16a) of the yarn deflection element (16).

12. The yarn sensor device (10) according to any one of claims 1-11, comprising a yarn sensor housing (20) suspended from at least one elastic element.

13. The yarn sensor device (31) according to any one of claims 1-9, wherein the yarn deflection element (41) is movable in two dimensions.