Abstract:
A method of directly determining setting values for an application point of regulation in a draw unit for drafting sliver, includes the following steps: obtaining a plurality of measured values of a quality-characterizing magnitude, such as a CV value, of the drafted sliver portion; utilizing the measured values for formulating a function having a minimum constituting an optimal application point of regulation for controlling the draw unit; determining the optimal application point of regulation in a pre-operational run of the draw unit; obtaining several measured values of a quality-characterizing magnitude based on an un-drafted sliver portion and determining the function between the quality-characterizing magnitudes and application points of regulation from measured values at the un-drafted sliver portion and at the drafted sliver portion.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the priority of German Application No. 100 41 893.7 filed Aug. 25, 2000, which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to a method of directly determining setting values for the application point of regulation in a regulated draw frame for slivers. The control system of the draw frame in which the extent of draft of the sliver may be set has at least one preliminary control system for changing the draft of the sliver. Based on the drafted sliver, a number of quality-characterizing measured values, such as CV values may be sensed and utilized for formulating a function whose minimum represents an optimum application point of regulation for the control of the draw frame. The optimized application point of regulation may be determined in a pre-operational test run or a setting run of the draw frame.  
           [0003]    The application point of regulation is an important setting magnitude in a draw frame to produce slivers with a high sliver uniformity, that is, with a small CV value.  
           [0004]    In a known system, during a pre-operational setting run, the sliver is drafted between the mid rolls and the output rolls of the draw unit and is withdrawn by calender rolls which are adjoined by a measuring device for the CV value of the drafted sliver. In the pre-operational setting run a plurality of CV values are determined which represent a quality-characterizing magnitude for the drafted sliver. Based on such measured values, a function is formulated whose minimum value corresponds to a value which promises to be the best adaptation of the regulation actual sliver. The plurality of measured values which are plotted and based on which the function is formulated, are in each instance measured for a different setting value of the regulation. Thus, for the definition of the function to be evaluated, each incremental value of an incrementally changing parameter, for example, the application point of regulation of the “electronic memory”, has to be associated with one of the measured values. It is a disadvantage of this system that the quality of the un-drafted sliver (input quality) introduced into the draw unit cannot be taken into consideration. It is a further drawback that only one certain CV value is considered.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to provide an improved method of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, ameliorates the determination and setting of the optimal application point of regulation at the regulating system of a draw unit.  
           [0006]    These objects and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of directly determining setting values for an application point of regulation in a draw unit for drafting sliver, includes the following steps: obtaining a plurality of measured values of a quality-characterizing magnitude, such as a CV value, of the drafted sliver portion; utilizing the measured values for formulating a function having a minimum constituting an optimal application point of regulation for controlling the draw unit; determining the optimal application point of regulation in a pre-operational run of the draw unit; obtaining several measured values of a quality-characterizing magnitude based on an un-drafted sliver portion and determining the function between the quality-characterizing magnitudes and application points of regulation from measured values at the un-drafted sliver portion and at the drafted sliver portion.  
           [0007]    The optimal application point of regulation (optimal dead period or delay) is determined by the draw frame itself by using the steps according to the invention. Based on the CV values of the sliver measured on line, the draw frame control system determines the optimal application point of regulation, that is, the machine optimizes itself. By utilizing the CV values of both the un-drafted and the drafted sliver the application point of regulation is determined more accurately, since effects of the incoming sliver too, such as those caused by thickness changes, are taken into consideration. Further, a more rapid determination of the application point of regulation is feasible.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic side elevational view of a regulated draw frame including a system for practicing the invention.  
         [0009]    [0009]FIG. 1 a  is a block diagram of a separate preliminary control device.  
         [0010]    [0010]FIG. 2 is an enlarged schematic side elevational view of one part of the FIG. 1 structure, illustrating the principal drafting field with indication of the principal drafting point.  
         [0011]    [0011]FIG. 3 is a diagram illustrating the effect of the application point of regulation on the on-line CV value.  
         [0012]    [0012]FIG. 4 illustrates a visual representation of an automatic determination of the optimal application point of regulation. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    [0013]FIG. 1 illustrates a draw frame  1  which may be, for example, an HSR model manufactured by Trützschler GmbH &amp; Co. KG, Mönchengladbach, Germany.  
         [0014]    The draw frame  1  includes a draw unit  2  having an upstream draw unit inlet  3  and a downstream draw unit outlet  4 . The slivers  5  are taken from non-illustrated coiler cans and are introduced into a sliver guide  6  which includes a measuring member  9  and from which they are withdrawn by calender rolls  7 ,  8 .  
         [0015]    The draw unit  2  is a 4-over-3 construction, that is, it is formed of a lower output roll I, a lower middle roll II and a lower input roll III as well as four upper rolls  11 ,  12 ,  13  and  14 . The draw unit  2  drafts the sliver  5 ′, composed of a plurality of slivers  5 , in a preliminary and principal drafting field. The roll pairs III, 14  and II, 13  constitute the preliminary drafting field whereas the roll assembly II, 11 , 13  and the roll pair I, 12  constitute the principal drafting field. The roll pair II, 13  is immediately followed by a pressure bar  30 . The drafted slivers  5  are introduced in the draw unit outlet  4  into a sliver guide  10  and are, by means of calender rolls  15 ,  16 , pulled through a sliver trumpet  17  in which the slivers are combined into a single sliver  18  which is subsequently deposited in coiler cans. The direction of the sliver passing through the draw frame  1  is designated at A.  
         [0016]    The calender rolls  7 ,  8 , the lower input roll III and the lower middle roll II which are mechanically coupled to one another, for example, by means of a toothed belt, are driven by a regulating motor  19  to which a desired rpm value may be applied. The respective upper rolls  14  and  13  are driven by the respective lower rolls by friction. The lower output roll I and the calender rolls  15 ,  16  are driven by a principal motor  20 . The regulating motor  19  and the principal motor  20  each have a respective regulator  21 ,  22 . Each rpm regulation occurs by means of a closed regulating circuit which includes a tachogenerator  23  connected with the motor  19  and the regulator  21 , as well as a tachogenerator  24  connected with the motor  20  and the regulator  22 .  
         [0017]    At the draw unit inlet  3  a mass-proportionate magnitude, for example, the sliver cross section is measured by the inlet measuring organ  9  which is known, for example, from German patent document DE-A-44 04 326. At the draw unit outlet  4  the cross section of the exiting sliver  18  is sensed by an outlet measuring member  25  which is associated with the sliver trumpet  17  and which is known, for example, from German patent document DE-A-195 37 983. A central computer unit  26  (control and regulating device), for example, a microcomputer with microprocessor, transmits a setting of the desired value to the regulator  21  for the regulating motor  19 . The measured values from both measuring members  9  and  25  are transmitted to the central computer unit  26  during the drafting process. The desired rpm value for the regulating motor  19  is determined by the central computer unit  26  from the measured values sensed by the intake measuring member  9  and from the desired value for the cross section of the exiting sliver  18 . The measured values of the outlet measuring member  25  serve for monitoring the exiting sliver  18 . With the aid of such a regulating system fluctuations in the cross section of the inputted slivers  5  may be compensated for by suitable regulation of the drafting process to obtain an evening of the sliver. A monitor  27 , an interface  28 , an inputting device  29  and a memory  31  are also connected to the computer  26 .  
         [0018]    While the preliminary control system may be integrated into the central computer unit  26  as shown in FIG. 1, according to FIG. 1 a , a separate preliminary control system  33  may be provided which is connected between the computer unit  26  and the regulator  21 . The computer unit  26  changes the application point of regulation R of the preliminary control system  33 .  
         [0019]    The measured values, for example, thickness fluctuations of the sliver  5 , obtained from the measuring member  9  are applied to the memory  31  with a variable delay. As a result of such a delay the change in the draft of the sliver in the principal drafting field according to FIG. 2 occurs at a moment when the sliver region measured earlier by the measuring member  9  and deviating from the desired value is situated in the principal drafting point  32 . When such a sliver region reaches the principal drafting point  32  the respective measured value is called from the memory  31 .  
         [0020]    The distance between the measuring location of the measuring member  9  and the drafting location at the principal drafting point  32  is the application point of regulation R.  
         [0021]    The apparatus according to the invention makes possible a direct determination of the setting values for the application point of regulation R. A plurality of measured values of the sliver thickness for different lengths of the exiting sliver  5 ′″ (drafted sliver) are taken from the measuring member  25  in the sliver trumpet, and three CV values (CV 1 m , CV 10 cm , CV 3 cm ) are calculated as quality-characterizing magnitudes. In a similar manner the measuring member  9  in the sliver guide  6  takes thickness measurements of a determined length of the un-drafted sliver  5 , and from these measured magnitudes quality-characterizing CV values (CV in ) are calculated. The determination of the CV values occurs preferably for four application points of regulation R. Expediently, in each instance two application points of regulations R are selected on the one side and two application points of regulation R are selected on the other side of the optimal application point of regulation R opt . In each instance a quality-characterizing number QK is determined by calculation from the CV values of the un-drafted sliver  5  and the drafted sliver  5 ′″. Further, a function between the numbers QK and the corresponding application points of regulation R are calculated in the computer  26  and displayed on the screen  27  (FIGS. 3 and 4). A polynomial of the second degree is determined from the four values of the application point of regulation R and the respective quality-characterizing numbers QK, and subsequently the minimum of the curve is calculated. The minimum point of the function corresponds to the optimum application point of regulation R opt  (see FIG. 4). In this manner, based on the drafted sliver  5 ′″, several measured values of three different CV values and based on the un-drafted sliver  5 , several measured values of a CV value are utilized, and those CV values which correspond to one another in relation to the application point of regulation R are combined to a quality number QK. Based on several quality numbers QK a function is formulated by computation, whose minimum point corresponds to the optimum application point of regulation R opt .  
         [0022]    During operation, in a setting run or test run, as a first step a predicted first value for the application point of regulation, for example, R −5  is set. This value is preferably an empirical value. Inputting may occur by the inputting device  29  or by calling the data from a memory. Subsequently, the following steps are taken:  
         [0023]    The sliver quality measured on-line for each setting of an application point of regulation is determined in each instance over a sliver length of 250-300 m.  
         [0024]    The measurements for optimizing the application point of regulation are performed on a sliver length without coiler can exchange; this may occur, for example, while the draw frame is at a standstill between the individual application points of regulation R.  
         [0025]    The determination of the on-line measured sliver quality is effected based on the following quality values:  
         [0026]    Output sliver quality: CV 3 cm , CV 10 cm , CV 1 m  (determined, for example, by a sensor arrangement  25  at the draw frame outlet  4  which may be a SLIVER-FOCUS model manufactured by Trutzschler GmbH &amp; Co. KG).  
         [0027]    Input sliver quality is described by CV in  (this is performed at the sensor device  9 ).  
         [0028]    From the above different quality values a quality-characterizing number QK is determined by the following formula:  
         
       QK=CV 
       3 cm 
       +CV 
       10 cm 
       +CV 
       1 cm 
       −CV 
       in  
     
         [0029]    With the above quality-characterizing number a sliver quality is sufficiently determined:  
         [0030]    QK high→bad quality  
         [0031]    QK low→good quality.  
         [0032]    Based on the QK equation, the natural scattering of the individual values is reduced and outlier values are not evaluated beyond what they are worth. The formation of a mean value leads to more exact predictions, and the influence of the regulation for both long and short wavelengths is taken into consideration. Even the influence of the input quality (sliver  5 ) is taken into consideration in the computation.  
         [0033]    The QK values which are computed from the real CV values obtained during tests are utilized for developing steps 4, 5, 6, 7 and 8 described below.  
         [0034]    The course of the quality curve above the application point of regulation R is always symmetrical to the minimum value of the curve (FIG. 3), that is, in case of an optimum application point of regulation R=0, the CV value deterioration at −4 is of the same extent as at +4. The functional relationship is described based on the symmetry by a polynomial of the second degree.  
         [0035]    Preferably, the region between −5 and +5 is to be considered so that the quality differences are sufficiently substantial and, at the same time, the level of the application point of regulation remains realistic.  
         [0036]    Reductions of three to four values for the application point of regulation R yield sufficient locations of reference (four pieces):  
         [0037]    −5 −4 −3 −1 0 1 2 3 4 5  
         [0038]    A polynomial of second degree (symmetrical course) is determined, with the aid of numerical solution process, from the four values for the application point of regulation R and the respective QK values.  
         [0039]    Thereafter, by means of numeric processes the minimum of the curve is determined.  
         [0040]    Such a minimum value is the optimum application point of regulation R in the then applicable machine setting and given fiber material (FIG. 4).  
         [0041]    By visual observation (monitor screen  27 ) an automatic determination of the application point of regulation may be displayed for the operator in a reproducible manner (FIG. 4).  
         [0042]    A number of different CV values of different sliver length portions are compared with one another and in addition to the output quality (sliver  5 ′″), the input quality too, is taken into consideration as an important quality characteristic. Further, the principal drafting point is calculated from the minimum of a polynomial of the second degree, that is, a symmetrical course. Based on an algorithm, several different CV values are combined to a quality-characterizing number QK. From the application points of regulation R and the corresponding quality-characterizing numbers a function is constructed by approximation. The minimum is calculated from the resulting function course. The determination is effected during pre-operational test run or setting run. The optimum application point of regulation R opt  is taken over prior to beginning of the regular production by the control system  26 ,  33  and a consistency inquiry is performed, possibly with error reports, and the result is reproducibly shown to the operator in a graphical representation. Four quality-characterizing numbers QK are obtained for determined application points of regulation R. These four quality-characterizing numbers are stored in a memory and based thereon a function curve is approximated. Only thereafter is the minimum of the function curve calculated. For each quality-number a few meters of sliver are delivered. The quality-characterizing magnitude (CV value) is determined between the delivery roll and the location of sliver deposition (output) as well as the measuring device  9  at the draw unit input  3 . The test run is performed during the charging of one coiler can. Between the four application points of regulation R (reference locations) the draw frame is stopped. The defined four application points of regulation R have different distances from one another.  
         [0043]    The automatic optimization according to the invention of the application point of regulation has, among others, the following advantages:  
         [0044]    Faster optimization of the application point of regulation;  
         [0045]    Optimization is performed with economy of material;  
         [0046]    No need to utilize laboratory equipment or Uster-testers;  
         [0047]    CV values for the optimization are no longer distorted by effects such as coiler can deposition, climatic influences, and the like. In this manner, a better optimization result is achieved;  
         [0048]    Realization of a “self-optimizing draw frame”;  
         [0049]    Effective utilization of the machine control system (computer  26 );  
         [0050]    By means of the automatic optimization the optimum application point of regulation may be found even if the data of the working memory and the data of the mechanical setting do not agree with one another; and  
         [0051]    Knowledge transfer for performing at the manual optimization to the utilizer (operator) is dispensed with.  
         [0052]    By virtue of the automatic determination of the application point of regulation (principal drafting point) not only the sliver uniformity but also, to the same extent, the CV values of the yarn quality may be improved. This was found in wool spinning products and PES/BW mixtures.  
         [0053]    The invention was explained in connection with a regulated draw frame  1 . It is to be understood that it may find application in other machines which include a regulated draw unit  2 , such as a carding machine, a combing machine and the like.  
         [0054]    It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.