• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method and a device for the optical detection of foreign fibers in a moving fiber strand (1), in particular a yarn, wherein light is emitted in the direction of the fiber strand and from the light reflected from the yarn, a brightness value (H (K)) of the yarn is determined and wherein the sanctity value is continuously checked for deviations from a mean brightness value (Hm (K)). According to the invention, a quotient of absolute deviation and a fixed value (Ho) specific to the fiber strand is formed, this quotient being used to evaluate the deviation.
    公开号:BE1018365A3
    申请号:E2009/0202
    申请日:2009-03-31
    公开日:2010-09-07
    发明作者:Olav Birlem
    申请人:Oerlikon Textile Gmbh & Co Kg；
    IPC主号:
    专利说明:

    Method and device for the optical detection of foreign fibers in a longitudinally moved fiber strand
    The invention relates to a method for the optical detection of foreign fibers in a longitudinally moved fiber strand, in particular a yarn, wherein Ficht is emitted in the direction of the fiber strand and from the yarn reflected light, a brightness value of the yarn is determined and wherein the brightness value continuously to deviations from a Brightness average is checked. The invention further relates to a device for carrying out the method.
    In the production or processing of fibers or yarns impurities, such as foreign fibers, the subsequent processing processes and the quality of the final product. Therefore, it is of great importance to detect the foreign fibers in order to obtain information about the quality of the fiber strand or to be able to initiate measures for their removal as soon as they are detected.
    For the detection of foreign fibers, in particular optical methods are used in practice, which are based on the different reflection behavior of fibers of different color or brightness. Such a method is described, for example, in the generic WO 93/19359. Here, a textile test material of the kind of a yarn, roving or ribbon is exposed to light, the light reflected from the test material is measured and closed from the change of the reflected light on the presence of an impurity. The test material is illuminated to at least two places and measured in addition to the reflection of the diameter of the test material or its change and derived from the reflection and from the diameter signal a quotient and continuously checked for deviations from an average. The average value can be determined adaptively by means of continuous averaging over larger lengths of the test material. The quotient described represents a brightness value of the test material.
    To determine the brightness value, there are many other methods in the prior art. For example, as described in DE 100 09 1 31 Al, the light emitted in the direction of the fiber strand can be adjusted as a function of the diameter, so that the light reflected by the fiber strand directly gives a brightness value.
    The deviation of the currently measured brightness value from a brightness mean value can be determined as an absolute deviation, ie as the difference between the measured value and the mean value. A better evaluation of the fibrous strand containing a foreign fiber is generally obtained by the use of a relative deviation, ie the quotient of absolute deviation and the mean brightness value.
    EP 0 877 1 08 A1 describes a method and an apparatus for cleaning yarn, wherein properties of the yarn are detected and yarn defects to be cleaned are defined by an adjustable cleaning limit. The properties of the yarn may be the thickness or mass of the yarn and the length of the yarn defects, as well as the color and structure of the yarn. For example, cleaning limits can be set for yarn defects such as thick or thin areas, foreign fibers, foreign substances or hairiness. An average value is formed for the respective measured values and from this the relative deviation to the mean value is determined. The relative deviation is compared with threshold values and classifies the error or initiates a clearing.
    The already cited WO 93/1 9359 describes that the trigger value found by the running mean value formation of the brightness
    Thresholds are assigned, the exceeding of which by the measuring signal in each case indicates a foreign fiber or another contamination.
    DE 100 57 1 70 A1 describes a method for determining impurities in flat structures, in particular fibers. In order to determine whether a given brightness value is increased in relation to the normal brightness value of the fabric, an average value of the brightness of the fabric is determined. Depending on this average, a threshold is set. If the determined brightness is above this threshold, an error location is displayed. The determined mean value can be multiplied by a factor to determine the threshold value. This factor can vary, depending on the type of fabric.
    In devices for the detection of foreign fibers, the signals are largely processed digitally today. That is, the analog signal of a sensor that detects the reflected light from the fiber strand is first converted into a digital signal and then further processed digitally in suitable control units.
    In the digitization of analog signals, not only a temporal quantization but also a value quantization takes place. Quantization into a finite number of quantization stages results in reduced resolution and quantization errors, that is, there is a difference between the original signal and the digital signal. The fewer discrete values available, the higher the resulting quantization noise; the signal-to-noise ratio decreases.
    The use of the above-described relative deviation from a mean value for checking the brightness value of a longitudinally moved fiber strand leads to large relative deviations in the case of dark yarn, that is to say with small mean brightness values. Conversely, in bright yarns, the relative deviations due to the larger divisor are rather small. As described above, in digital processing, only a limited number of discrete values are available to which the relative deviations that occur must be mapped. The large values with dark yarn lead to a low resolution of the digitized relative deviation and thus, according to the above explanations, to an undesired quantization noise.
    It is the object of the present invention to reduce the quantization noise in the digital determination of the brightness deviation and to enable a reliable evaluation.
    The object is achieved by the characterizing features of the method claim 1 and the device claim 4. Advantageous developments of the invention are the subject of the dependent claims.
    To solve the problem, a quotient of absolute deviation and a given, specific for the fiber strand fixed value is formed and this quotient is used to evaluate the deviation.
    By calculating the brightness deviation according to the invention, its value range can be adjusted for different yarn colors. As a result, the existing number of discrete values in the digital evaluation can be optimally utilized, and the quantization noise is reduced. At the same time, the relation to the brightness of the faultless yarn, unlike an absolute deviation, can be considered.
    On dark yarn, differently colored foreign fibers, in particular lighter foreign fibers, are perceived less well by the observer, so that larger differences can be permitted quantitatively. In the variance calculation according to the invention, by means of the fiber-strand-specific fixed value, a corresponding weighting can already be carried out, so that the threshold values for which an error location is recognized or not reached need not be adapted or at least not adjusted to the same extent as in the prior art. Thus, not only the occurring value ranges but also the permissible value ranges of the calculated deviation for different fiber types are adjusted. This also adapts the resolution within the permissible value range and thus reduces quantization errors altogether.
    In a preferred embodiment of the method according to the invention, the fixed value is changed when changing the yarn color.
    In a further preferred embodiment, the specific fixed value does not fall below a predetermined value.
    The object is further achieved by a device for the optical detection of foreign fibers, wherein a light source is adapted to emit light in the direction of the fiber strand, and a sensor is adapted to detect the light reflected from the yarn, and control means are provided which are formed to determine a brightness value of the yarn from the sensor signal and continuously check the brightness value for deviations from a brightness average. According to the invention, the control means are further configured to determine a quotient of absolute deviation and a predetermined fixed value specific to the fiber strand and to use this to evaluate the deviation.
    The invention will be explained in more detail with reference to an embodiment shown in the drawings.
    Show it:
    1 shows a device for the optical detection of foreign fibers.
    Fig. 2 is a schematic diagram of the calculation of the invention
    Brightness variation;
    Fig. 3 is a flowchart for determining the fixed value.
    Fig. 1 shows greatly simplified the basic structure of a device for optical detection of foreign fibers in a longitudinally moved fiber strand. The fiber strand 1 is moved in the direction of the arrow 7. A light source 2 emits light in the direction of the fiber strand 1. The light is reflected by the fiber strand 1 and detected by the sensor 3. The light source 2 is connected via a control line 6 and the sensor 3 via a control line 5 to a digital control unit 4. The control unit 4 continuously determines a brightness value of the fiber strand according to one of the known methods. Depending on which method is used to determine brightness, additional light sources or sensors are required.
    The control unit 4 determines at each sampling step k the brightness deviation AH (k) according to the method according to the invention. The calculation is shown graphically in FIG. By means of the adder 10, a continuously determined brightness value mean value Hm (k) is subtracted from the brightness value H (k) determined in the current sampling step k. The result is fed to the arithmetic unit 11. This multiplies the difference by the factor jj- or divides the difference
    Difference by the value Ho-Ho is a specific fixed value for the fiber strand and thus not dependent on the current sampling. According to the invention, the value AH (k) is calculated according to the following formula (i) for evaluating the deviation of the brightness value from a mean brightness value.
    (I)
    FIG. 3 shows a possibility of determining the fiber strand specific fixed value Fl0. The flowchart in FIG. 3 starts with the terminator 21. The operation 22 first of all sets a brightness value FT. The operation 23 determines from j samples of the flatness values a mean brightness value Hm (j) of the processed fiber strand by means of the equation (ii).
    (G)
    With the branch 24, the yarn mean Hm (j) is compared with the predetermined value Hi. If the average value Hm (j) is smaller than the predetermined value Hi, the operation 25 is executed. The operation 25 assigns the fiber strand specific fixed value Ho to the predetermined value Hi. If the average brightness value Hm (j) is not smaller than the predetermined value Hi, after the branch 24 the operation 26 follows. Thus, the previously determined average brightness value Hm (j) is assigned to the fixed value Ho. With the terminator 27, the determination of the fiber strand specific fixed value H0 is completed. In the event that the brightness average Hm (j) is greater than the predetermined value Hi, the fixed value Ho can also be replaced by the continuous average brightness value Hm (k). In other words, with bright yarns, one can maintain the known relative deviation and only use the fixed value for dark yarns whose brightness value is less than the predetermined value Hi.
    权利要求:
    Claims (4)
    [1]
    1. A method for the optical detection of foreign fibers in a longitudinally moved fiber strand (1), in particular a yarn, wherein light is emitted in the direction of the fiber strand and from the light reflected from the yarn, a brightness value (H (k)) of the yarn is determined and wherein the brightness value is continuously checked for deviations from a mean brightness value (Hm (k)), characterized in that a quotient of absolute deviation and a predetermined fixed value specific to the fiber strand (H0) is formed and this quotient is used to evaluate the deviation.
    [2]
    2. The method according to claim 1, characterized in that the fixed value (H0) is changed when changing the yarn color.
    [3]
    3. The method according to claim 1, characterized in that the specific fixed value (Ho) does not fall below a predetermined value (Hi).
    [4]
    4. A device for the optical detection of foreign fibers in a longitudinally moved fiber strand (1), in particular a yarn, and for carrying out the method according to one of claims 1 to 3, wherein a light source (2) is adapted to emit light in the direction of the fiber strand , and a sensor (3) is adapted to detect the light reflected from the yarn, and control means (4) are provided which are adapted to determine from the sensor signal a brightness value (H (k)) of the yarn and the brightness value (H (k)) continuously to check for deviations from a mean brightness value (Hm (k)), characterized in that the control means (4) are further adapted to a quotient of the absolute deviation and a predetermined, specific to the fiber strand fixed value (Ho) to be used and to evaluate the deviation.
    类似技术:
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    同族专利:
    公开号 | 公开日
    CH698764A2|2009-10-15|
    CN101556252A|2009-10-14|
    CH698764B1|2013-01-15|
    DE102008017258A1|2009-10-08|
    CN101556252B|2013-06-19|
    引用文献:
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    法律状态:
    2011-09-30| RE| Patent lapsed|Effective date: 20110331 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE200810017258|DE102008017258A1|2008-04-04|2008-04-04|Foreign fiber i.e. thread, detecting method for use in longitudinal moving fiber stand, involves forming ratio from absolute deviation and predetermined fixed value that is specified for fiber stand|
    DE102008017258|2008-04-04|
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