Yarn monitoring method

Abstract

The invention relates to a method for monitoring the quality of a yarn on a textile machine, wherein the yarn passes a monitoring unit of the textile machine, with the aid of which at least one measured variable (M) which is dependent on a physical parameter of the yarn is determined, and wherein the measured variable (M), or a variable derived therefrom, is evaluated with respect to the position thereof with regard to at least one reference value (R). According to the invention, it is proposed that the selection of the reference value(s) (R) takes place taking into account one or more characteristic variables of the yarn, said characteristic variables being yarn-specific and defined prior to evaluating the measured variable (M). Furthermore, a textile machine is proposed which comprises at least one monitoring unit for monitoring at least one physical parameter of the yarn, and at least one controller which is operatively connected to the monitoring unit. The textile machine is characterized in that the controller is configured to monitor the yarn quality according to one or more of the preceeding claims.

Claims

1. A method for monitoring quality of a yarn in a textile machine, comprising: passing the yarn through a monitoring unit of the textile machine and determining a measured variable that depends on one or more continuous physical characteristics of the yarn; evaluating the measured variable (which encompasses a variable derived from the measured variable) with regards to a reference value; before evaluating the measured variable, selecting the reference value based on one or more yarn-specific physical characteristic variables of the yarn; and wherein continuous yarn thickness is the yarn-specific physical characteristic variable of the yarn and the reference value is selected based on any one or combination of the following yarn characteristic variables: yarn hairiness, yarn material, yarn uniformity, yarn fineness, yarn stiffness, extent of yarn twist, or yarn tension.

2. The method as in claim 1, wherein the reference value is selected from a database that includes multiple reference values based on the yarn-specific physical characteristic variables of the yarn.

3. The method as in claim 1, wherein the measured variable varies as yarn thickness changes and is determined by an optical system that evaluates geometry of the yarn by a shadow the yarn casts.

4. The method as in claim 1, wherein the reference value is an individual value that serves as a target value of the measured variable, and the measured variable is evaluated based on deviation from the measured variable form the reference value.

5. The method as in claim 4, wherein the measured variable is evaluated based on whether it lies between a minimum value below the reference value and a maximum value above the reference value.

6. The method as in claim 4, wherein the reference value includes a first reference value that defines an admissible minimum value, and a second reference value that defines an admissible maximum value, wherein the measured variable is evaluated based on whether it lies between the first reference value and the second reference value.

7. The method as in claim 1, wherein the measured variable is continuously determined and evaluated.

8. The method as in claim 1, wherein the measured variable is determined as an absolute value.

9. The method as in claim 1, wherein the reference values are determined based on specific physical characteristics of a reference yarn, and the reference values and respective specific physical characteristics are correlated with each other and stored in a database.

10. The method as in claim 9, wherein the reference values are periodically checked and reset if the reference value exceeds a maximum value or falls below a minimum value.

11. The method as in claim 9, wherein before monitoring of the yarn, the references values correlated with the specific physical characteristics that determine the measured variable are downloaded from the database.

12. The method as in claim 11, wherein the database is stored in a control unit for the textile machine or in the monitoring unit.

13. A textile machine, comprising a monitoring unit for monitoring quality of a yarn produced by the textile machine in accordance with the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages of the invention are described in the following embodiments which show:

(2) FIG. 1 a method for generating a reference value,

(3) FIG. 2 a method for selecting a reference value from a database,

(4) FIG. 3 a possible chronological sequence of a measured variable.

DETAILED DESCRIPTION

(5) Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

(6) FIG. 1 depicts schematically a possible process for establishing and storing a necessary reference value in a database for executing the method according to the invention.

(7) First of all, a measured variable is defined that in the subsequent monitoring of yarn quality on a textile machine is recorded so it can serve as basis for quality assessment. For example, a power signal generated by a camera can be a measured variable, in which case the camera, in turn, can be designed to detect the geometry—especially the width—of the shadow, cast by the yarn when lit. Here, the magnitude of the measured variable therefore depends on the yarn's width (=spatial extension perpendicular to the yarn's longitudinal axis), i.e. the width of the yarn is monitored.

(8) After setting the measured variable, a reference value for the measured variable is defined. The reference value represents the value that the measured variable should take when yarn quality is perfect. Needless to say, additional or alternative reference values in form of admissible minimum and maximum values can also be defined, between which the measured variable should lie if yarn quality is perfect.

(9) So the reference values can always be retrieved from a database containing the reference values when a certain yarn should be manufactured or otherwise handled by the textile machine, the reference value(s) is/are not only stored as value(s) in the database. Rather, the linking with one or several yarn-specific characteristic variables with whose help the corresponding reference values can always be allocated to one yarn in particular takes place. Codes (e.g. alphanumeric ones) or other yarn-specific characteristic variables as well, such as yarn material, yarn twist, yarn weight related to the length, yarn hairiness, etc. can be used. Crucial is merely that once the reference values are set, they can still be assigned unmistakably to a certain yarn later.

(10) In other words, the solution according to the invention allows a certain yarn (e.g. cotton yarn with hairiness A, strength B and yarn count C) to be monitored always equally. Thus, whenever such a yarn should be monitored, the associated reference value is forwarded to the control of the textile machine or to its corresponding yarn monitoring units, so that the point of reference of the monitoring is always the same. If, additionally, the characteristic variable is measured by detecting absolute values, then the monitoring unit does not have to be recalibrated before each change of the yarn, as is customary in state of the art. Rather, yarn quality can be reliably monitored—especially in a reproducible way—always from the start.

(11) FIG. 2 shows a possible approach taken for selecting the correct reference value or corresponding minimum or maximum values.

(12) First, the characteristic variable(s) of the yarn to be monitored must be entered in the database, which, in the final analysis, provides the desired values linked to the characteristic variable(s). The reference value(s) is/are finally transferred to the control of the textile machine or its corresponding monitoring units and serve as basis for subsequent quality monitoring.

(13) As part of monitoring, the yarn's measured variable is finally determined by preferably measuring continuously a measured value that represents the measured variable and comparing it with the reference value. A measured variable that lies within predefined limits (admissible minimum value, admissible maximum value) indicates acceptable yarn quality. If the measured variable exceeds or does not reach the admissible values mentioned above, yarn quality no longer complies with specifications. In this case, either an alarm is emitted or—if the yarn is being monitored immediately after production—an intervention in the control of the respective production unit takes place. In the end, the goal can be to regulate the production parameters in such a way that the measured variable always lies within the above-mentioned limits.

(14) FIG. 3 finally shows a possibility to determine or adjust the reference value. Here, M (y axis) stands for the measured variable and t (x axis) for time.

(15) If there is still no reference value R for a certain yarn, then the type of measured variable M (e.g. the signal of a line scan camera that monitors yarn width) to be monitored later is established. Afterwards, the recording of the measured variable M is started while the corresponding yarn passes through the monitoring unit (t.sub.0: start of recording measured variable M). If yarn quality complies with specifications, the currently available magnitude of the measured variable M (or a value derived from it) in the point in time t.sub.1 is defined as reference value R.sub.1 and stored in the database, linking it with one or several typical characteristic variables of the yarn (hairiness, yarn count, yarn code and/or other variables that characterize a certain yarn). If a yarn with similar properties should later be monitored once again at a later point in time, then a reference value R.sub.1 is available that can be always be retrieved from the database.

(16) If subsequent yarn monitoring (in FIG. 3 it is exemplarily the point in time t.sub.2) determines that the measured variable M does not reach an admissible minimum value Mi.sub.1 (alternatively: exceeds an admissible maximum value Ma.sub.1), then it could be possible for the textile machine operator to check yarn quality. If the checking determines that quality still complies with specifications, then the reference value R can be corrected from the value R.sub.1 to the value R.sub.2. The corrected value is finally stored in the database (or the old values are overwritten by the corrected ones) together with a correspondingly corrected minimum value Mi.sub.2 and a correspondingly corrected maximum value Ma.sub.2.

(17) Afterwards, the new reference value R.sub.2 or the two reference values Ma.sub.2 and Mi.sub.2 finally serve as new reference variables that can be used for monitoring yarn quality.

(18) This invention is not limited to the embodiment shown and described. Variations within the framework of the patent claims are just as possible as a combination of the characteristics, even if they are shown and described in different embodiments.