CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the priority of German Application No. 100 57 699.0 filed Nov. 21, 2000, which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to an apparatus for measuring the tension of sliver composed of cotton fibers, chemical fibers or the like, as it runs in a draw frame. Upstream of the draw frame a creel is situated below which coiler cans are positioned from which sliver is withdrawn. Downstream of the creel, as viewed in the direction of sliver advance, a rider roll assembly and a sliver guide with transporting rolls are provided, followed downstream by input rolls of the draw unit of the draw frame. The slivers running into the draw frame from the coiler cans are in a tensioned condition at least in the zone between the transport rolls and the input rolls of the draw unit.  
           [0003]    The sliver tension effected by the transport rolls is derived from the ratio of the circumferential speed of the lower input roll of the draw unit to the circumferential speed of the transport rolls. A setting of the transport roll tension is feasible by means of the transmission gearing associated with the transport rolls. The transport roll tension should be set in such a manner that the slivers between the transport rolls and the lower input roll of the draw unit run with the smallest possible tension which still ensures that the slivers do not undulate as they run on the sliver guide table. Further, when setting the tension, it should be taken into consideration that a satisfactory spread of the sliver is ensured. The tension setting is based on a table in which the different transmission gears are associated with a respective transport roll tension; such table is based empirically for different fiber materials. For the same transmission gear a different transport roll tension may result in case an assortment (fiber lot) change occurs. In practice, the run of the slivers is visually observed and based on such observation, an appropriate transmission gear is selected. In addition, the quality of the drafted sliver at the output of the draw unit is taken into consideration.  
           [0004]    It is a disadvantage of the above-outlined conventional arrangement that the tension setting requires substantial experience and does not make possible a precise determination of the transport roll tension.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to provide an improved apparatus of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, makes possible a precise determination of the transport roll tension and a setting for different fiber lots.  
           [0006]    This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the draw frame includes a transport roll pair for simultaneously guiding a plurality of slivers running in an advancing direction; and a series of drafting roll pairs spaced from one another in the advancing direction. One of the drafting roll pairs is a first drafting roll pair as viewed in the advancing direction. The first drafting roll pair is positioned downstream of the transport roll pair. A measuring device is contacted by the running slivers and includes a pressure-sensitive member exposed to a force derived from the running slivers for emitting, a signal representing the force; and a deflecting arrangement for deflecting the running slivers for causing them to be partially trained about the deflecting arrangement to exert to the pressure-sensitive member a pressing force proportional to a tension of the slivers prevailing upstream and downstream of the pressure-sensitive member.  
           [0007]    The measures according to the invention make possible a precise determination particularly of the transport roll tension and thus provide for an optimal setting of such tension even in case of a fiber lot change. In this manner, tension values are determined for the most important materials. Therefore, the actual measured value for the tension draft may be compared with the determined, desired value and the machine operator may receive an indication whether the correct tension values have been selected.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 a  is a schematic side elevational view of a draw frame incorporating the invention.  
         [0009]    [0009]FIG. 1 b  is a partial, schematic top plan view of the construction shown in FIG. 1 a.    
         [0010]    [0010]FIG. 2 a  is a sectional side elevational view of a preferred embodiment of the invention.  
         [0011]    [0011]FIG. 2 b  is a fragmentary sectional front elevational view of the construction shown in FIG. 2 a.    
         [0012]    [0012]FIG. 3 is a side elevational view of another preferred embodiment of the invention.  
         [0013]    [0013]FIG. 4 is a schematic side elevational view of a draw unit, incorporating the embodiment of FIG. 3 and showing a block diagram of the electronic draw frame control. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    [0014]FIG. 1 shows a draw frame DF which may be an HSR model manufactured by Trüttzschler GmbH &amp; Co. KG, Monchengladbach, Germany. The draw frame has an input region  1 , a measuring region  2 , a draw unit  3  and a sliver coiling unit  4 . In the input region  1  two side-by-side extending rows of coiler cans are arranged, of which one row of three coiler cans  5   a ,  5   b  and  5   c  are shown underneath a creel  6 . The slivers  7   a ,  7   b  and  7   c  withdrawn from the respective coiler cans are guided by supply rolls  8   a ,  8   b  and  8   c  and introduced into the draw unit  3 . Each driven supply roll  8   a ,  8   b  and  8   c  is associated with a respective upper roll  9   a ,  9   b  and  9   c  co-rotating with the supply rolls. As shown in FIG. 1 b , the second row of coiler cans (not visible in FIG. 1 a ) is associated with additional supply rolls  8   d ,  8   e  and  8   f , each cooperating with a respective, non-illustrated upper roll similar to the rolls  9   a - 9   c . The six slivers  7   a - 7   f  withdrawn from the coiler cans are guided to the draw frame proper along the creel  6 .  
         [0015]    After the slivers have been drawn and combined into a single drafted sliver  10  in the draw unit  3 , the sliver  10  is deposited in coils into a receiving coiler can  11  by a rotary head of the coiler unit  4 .  
         [0016]    In the region underneath each roll pair  8   a ,  9   a , etc. which crush the respective slivers  7   a - 7   f , a non-illustrated guide for each sliver is provided. The advancing direction of the slivers is designated at A. Particularly at high withdrawing speeds the slivers balloon and swing above the oiler cans. The slivers are quieted after passing the supply rolls  8   a - 8   f . Downstream of the creel  6 , at the input of the draw frame a driven roll assembly is provided which is composed, for example, of two lower rider rolls  12   a ,  12   b  and three upper rider rolls  13 . Each supply roll  8   a - 8   f  is connected to a drive.  
         [0017]    With reference to FIGS. 1 a ,  1   b  and  4 , in the draw unit  3  the length portion  7 ′″ of the slivers  7   a - 7   f  is exposed to the transport roll tension in the region between the cooperating transport rolls  15 ,  16  and the cooperating input rolls  26 , III. The apparatus  17  structured according to the invention is disposed in this region such that the length portions  7 ′″ of the slivers  7   a - 7   f , as they run in the direction A, press down on the apparatus  17 . The length portion  7 ′ of the slivers  7   a - 7   f  extends between the respective supply rolls  8   a - 8   f  on the one hand and the rider rolls  12   a ,  12   b ,  13  on the other hand, while the length portions  7 ″ of the slivers  7   a - 7   f  extend between rider rolls  12   a ,  12   b ,  13  on the one hand and the cooperating transport rolls  15 ,  16 , on the other hand. The length portions  7 ′,  7 ″ and  7 ′″ are all exposed to controlled tensions.  
         [0018]    The supply rolls  8   a - 8   f  all have the same diameter, for example, 100 mm. The rpm decreases in the working direction A from supply roll to supply roll and is predetermined by a control and regulating device  38 . As a result, the circumferential speed of the supply rolls decreases in the working direction A. The circumferential speed of the supply rolls is set such that the tension of the running slivers  7   a - 7   f  has the desired magnitude. The supply rolls  8   a - 8   f  are rotated by non-illustrated drives or transmission mechanisms. The supply rolls  8   a - 8   f  are conventional, two-part constructions. As shown in FIGS. 1 a  and  1   b , the slivers  7   a - 7   f  run from the creel  6  to the intake region  1  through the rider roll assembly  12 ,  13 , the sliver guide  14  which includes a measuring device with the transport rolls  15 ,  16 , the tension-sensing apparatus  17  (to be described in detail later), the draw unit  3 , the sliver guide  27 , the sliver trumpet  30  provided with calender rolls  28 ,  29  and the coiler head which deposits the sliver in the coiler can  11 .  
         [0019]    [0019]FIG. 2 a  and  2   b  illustrate an embodiment of the apparatus  17  according to the invention. A table-like frame  42  is provided whose plate  42   a  is supported by two legs  42   b ,  42   c  on a fixed machine component  41 . In the region of the two ends of the plate  42   a  two rotary deflecting rollers  44  and  45  are arranged in a series as viewed in the working direction A. On the upper face of the plate  42   a  a support element  20  is secured which holds a small-displacement measuring member  19 , for example, a piezoelectric element which functions as a force take-up device. Opposite the supporting element  20  the measuring element  19  cooperates with a frame-like pressing element  18  composed of a supporting element  43  contacting the measuring member  19  and a rotary deflecting roller  46  secured to the upper region of the supporting element  43 . The length portions  7 ′″ of the slivers  7   a - 7   f  emerging from the transporting rolls  15 ,  16  are deflected, as they run underneath a deflecting roller  44 , from a horizontal position to proceed upwardly at an oblique angle to the deflecting roller  46  and then, running above the deflecting roller  46 , the slivers are deflected at an angle to proceed downwardly to a deflecting roller  45  and are, as they run underneath the deflecting roller  45 , reoriented into a horizontal direction. The slivers exert, via the deflecting roller  46  and the supporting element  43 , a pressing force on the measuring element  19 .  
         [0020]    In operation, first the frame  42  is set on the draw frame cover  41  so that the length portions  7 ′″ of the slivers  7   a - 7   f  remain unaffected. Thereafter the frame-like supporting element  43  is passed within the frame  42  under the length portions  7 ′″ and above the force take-up device  19  and is positioned and immobilized on the frame  42 . The measuring process may be activated when the intended delivery speed is reached. To eliminate the effect of the free sliver length, the weight of the input portion of the sliver and the loop-around friction, the slivers are deflected by the rotatable rollers  44 ,  45  and  46  and thus the length of the raised sliver portion is defined. The extent of draft and the output number of the input weight are known data inputted into the control device, so that the sliver weight may be subtracted from the tensioning force.  
         [0021]    According to the embodiment of the sensor device  17 ′ shown in FIG. 3, a supporting element  43 ′ has a rounded upper face directly engaged by the running sliver which, due to its tensioned state, presses down with a force P on the measuring member  19  counter-supported by the supporting element  20  secured to the machine frame  41 . The measuring member  19  is disposed between the support element  20  and the pressing element  18 . This embodiment is void of deflecting rollers which characterize the embodiment of FIGS. 2 a  and  2   b . The device  17 ′ is inserted underneath the sliver and the measuring process may be activated when the intended delivery speed is reached.  
         [0022]    While the tension-sensing device  17  or  17 ′ was described as being positioned to contact the sliver length portions  7 ′″ between the transport rollers  15 ,  16  and the input drafting roll pair  26 , III, it is to be understood that instead or additionally, the tension sensing device  17  or  17 ′ may be disposed between the supply rolls  8   a - 8   f  on the creel  6  and the rider rolls  12   a ,  12   b ,  13  to contact the sliver length portions  7 ′ and/or between the rider rolls  12   a ,  12   b ,  13  and the transport rolls  15 ,  16  to contact the sliver length portions  7 ″.  
         [0023]    Turning to FIG. 4, the draw unit  3  of the draw frame has an input  21  and an output  22 . The length portions  7 ″ of the slivers  7   a - 7   f  are moved through the measuring member  14  as they are pulled by the transport rolls  15 ,  16 .  
         [0024]    The draw unit  3 , in which the drafting of the slivers occurs, is a 4-over-3 construction, that is, it has a lower output roll I, a lower middle roll II and a lower input roll III as well as four upper rolls  23 ,  24 ,  25  and  26 . The draft is composed of a preliminary and principal draft. The roll pairs  26 , III and  25 , II constitute the preliminary drafting field whereas the roll pair  25 , II and the roll assembly  23 ,  24 , I constitute the principal drafting field. The drafted slivers reach, at the draw unit output  22 , a sliver guide  27  and are, by means of calender rolls  28 ,  29 , pulled through a sliver trumpet  30  in which the slivers  7   a - 7   f  are combined into a single sliver  10  which is subsequently deposited in a coiler can  11 .  
         [0025]    The transport rolls  15 ,  16 , the lower input roll III and the lower mid roll II which are mechanically interconnected, for example, by a toothed belt, are driven by a regulating motor  31  rotated by a desired rpm value which may be inputted. The respective upper rolls  26  and  25  are driven by friction by their respective lower rolls. The lower output roll I and the calender rolls  28 ,  29  are driven by a main motor  32 . The regulating motor  31  and the main motor  32  are provided with a respective regulator  33  and  34 . The rpm regulation occurs by means of a closed regulating circuit in which tachogenerators  35  and  36  are connected with the regulating motor  31  and the main motor  32 , respectively. At the draw unit input  21  a mass-proportionate magnitude, for example, the cross section of the slivers is measured by the input measuring organ  14 . At the draw unit output  22  the cross section of the exiting sliver  10  is measured by an output measuring member  37  integrated in a sliver trumpet  30 .  
         [0026]    A central computer unit  38  (control and regulating device), for example, a microcomputer with microprocessor, transmits a setting of the desired value to the regulator  33  for the regulating motor  37 . The measured values of the measuring organ  14  are transmitted to the central unit  38  during the drafting process. From the measured magnitudes determined by the measuring organ  14  and from the desired value for the cross section of the exiting sliver  10 , the central unit  38  determines the setting value for the regulating motor  37 . The measured values determined by the output measuring member  27  serve for monitoring the discharged sliver  10 . With the aid of such a regulating system fluctuations in the cross section of the inputted slivers are compensated for by means of a suitable regulation of the drafting process and thus an evening of the sliver  10  may be achieved.  39  designates an inputting device and  40  designates schematically the drive for the supply rolls  8   a - 8   f . The measuring element  19  of the measuring device  17  is also connected with the control and regulating device  38  to receive, from the measuring device  17 , electric signals x which represent the pressure which the running sliver exerts on the measuring element  19 . Such a pressure is a function of the tension of the running sliver upstream and downstream of the measuring device  17 . In the control and regulating device  38  the tension force exerted on the running sliver is computed from the signals x. The resulting signals are stored in a memory  47 . In this manner tension values for the most important materials [N/ktex input] are stored. As a result, the actual measured tension value may be compared with the inputted tension values and thus the machine operator may receive an indication whether the correct tension values were selected.  
         [0027]    While the invention is described in conjunction with a regulated draw frame, it is to be understood that the invention may find application in a non-regulated draw frame as well.  
         [0028]    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.
A draw frame includes a transport roll pair for simultaneously guiding a plurality of slivers running in an advancing direction; and a series of drafting roll pairs spaced from one another in the advancing direction. One of the drafting roll pairs is a first drafting roll pair as viewed in the advancing direction. The first drafting roll pair is positioned downstream of the transport roll pair. A measuring device is contacted by the running slivers and includes a pressure-sensitive member exposed to a force derived from the running slivers for emitting a signal representing the force; and a deflecting arrangement for deflecting the running slivers for causing them to be partially trained about the deflecting arrangement to exert on the pressure-sensitive member a pressing force proportional to a tension of the slivers prevailing upstream and downstream of the pressure-sensitive member.