Abstract:
An apparatus for measuring the thickness of a plurality of side-by-side running slivers includes a supporting surface guiding the side-by-side running slivers thereon in a single plane; a holding member; and a plurality of sensor elements movably secured to the holding member to be movable in a direction transverse to the plane. Each sliver is contacted by a separate sensor element for causing excursions thereof by thickness fluctuations of the running sliver. Each sensor element is yieldingly pressed against a respective sliver, and each sensor element cooperates with the supporting surface for pressing the running slivers against the supporting surface. An adding device adds the excursions of the sensor elements, and a transducer converts the excursion values into electric pulses.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of German Application No. 197 40 816.8 filed Sep. 17, 1997 and German Application No. 198 19 728.4 filed May 2, 1998, which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for measuring the thickness of a running sliver bundle in a drawing frame. A sliver guide is arranged at the inlet of the drawing unit of the drawing frame for the sliver bundle which is composed of side-by-side inputted slivers. The slivers are guided in a single plane through a measuring member which includes a biased, movable, mechanically contacting sensor element which, in cooperation with a counterface, forms a constriction through which the slivers pass after being densified thereby. The positional changes of the sensor element in response to thickness fluctuations of the running sliver bundle formed of the slivers are converted into electric control pulses by a transducer. 
     According to a known device which measures the thickness of a sliver bundle and which includes a sliver guide for guiding the sliver bundle at the drawing unit inlet, the walls of the device converge at least partially conically to gather the slivers inputted in one plane. Further, a roll pair is arranged downstream of the sliver guide. The slivers again diverge downstream of the roll pair. The sliver thickness measuring device has a biased, movable sensor element which forms a constriction with a stationary counterface for the throughgoing sliver bundle as outlined above. The sliver thickness is sensed as the densified slivers are guided in the sliver guide side-by-side, while the roll pair withdraws the sensed slivers. 
     It has further been proposed to densify the side-by-side arranged slivers from above across the width of the sliver bundle. For this purpose the sensor element, in addition to a sensing and densifying motion in the direction of the slivers, also executes a pivotal motion about an axis which is parallel to the running direction of the slivers and thus the sensor element is able to detect that, for example, slivers of unlike thickness are arranged side-by-side. The movable sensor element has a slide face by means of which the slivers are, in their side-by-side relationship, densified and pressed against the stationary counterface. Disadvantageously, in such an arrangement the thickest sliver determines the distance between the sensor element and the counterface, and even a small thickened location in one of the slivers results in a greater distance. The slivers on either side of such a thickened location are thus pulled out of the thus-obtained clearance without having been submitted to thickness sensing. 
     SUMMARY OF THE INVENTION 
     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, ensures a significantly improved detection of the thickness fluctuations of the slivers and makes possible a more accurate guidance thereof. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for measuring the thickness of a plurality of side-by-side running slivers includes a supporting surface guiding the side-by-side running slivers thereon in a single plane; a holding member; and a plurality of sensor elements movably secured to the holding member to be movable in a direction transverse to the plane. Each sliver is contacted by a separate sensor element for causing excursions thereof by thickness fluctuations of the running sliver. Each sensor element is yieldingly pressed against a respective sliver, and each sensor element cooperates with the supporting surface for pressing the running slivers against the supporting surface. A summation device adds the excursions of the sensor elements, and a transducer converts the excursion values into electric pulses. 
     By means of the invention according to which all slivers are individually measured for thickness at the inlet of the drawing frame, a differentiated summation result may be obtained in which the thickness of each individual sliver is taken into account. In this manner the evening of thickness fluctuations of all slivers is significantly improved, eventually resulting in a more uniform drawn sliver, and thus an improved yarn may be manufactured. 
     The invention includes the following additional advantageous features: 
     All sensor elements are connected with a holding member which is biased by a force-exerting member and to which the sum of the displacements of the individual sensor elements is applied. 
     The sensor element is biased by a spring or the like. 
     The sensor elements are constituted by leaf springs. 
     The leaf springs are cantilevered. 
     The counterface is the circumferential surface of a rotating roll. 
     The measuring member is arranged upstream of the sliver guide. 
     The measuring member is integrated in the sliver guide. 
     The sensor elements are connected with a rotatably or shiftably supported holding member which is biased by a force-exerting member and to which the sum of the displacements of the individual sensor elements is applied and wherein the end of the sensor elements includes a securing region fixedly connected with the holding member and further wherein the sensor elements form a moving means for the rotary of shifting motion of the biased holding member and the sensing region is formed by the other end of the sensor elements. 
     The sensor elements are leaf springs. 
     The sensor elements lie against the end face of a feed table. 
     A clearance is provided between the free ends of the sensor elements and the free end of the feed table. 
     The feed table or the feed roll are supported in a movable, spring-biased manner; the biasing springs are harder than the springs constituting the sensor elements. 
     The feed table is stationarily held relative to the direction of excursion of the sensor elements. 
     One end of the sensor elements may lift off the holding member. 
     An abutment is provided for limiting the excursion of the sensor elements. 
     The leaf springs are arranged parallel to one another. 
     The leaf springs are soft in the direction of the displacement of the feed table. 
     The leaf springs are stiff in the direction oriented from the feed table to the holding member. 
     The holding member is a longitudinal beam. 
     The holding member extends parallel to the feed roll. 
     The holding member is resistant to torsion forces. 
     At the end face of the holding member at least one torsion bar is disposed in an axial direction. 
     The holding member is supported in a rotary bearing at least at one end thereof. 
     A measuring element detects the rotary motion of the holding member. 
     The measuring element is an inductive path sensor. 
     The measuring element includes expansion strips. 
     In an apparatus in which the thickness variations are mechanically sensed over the width of the sliver bundle by the individual sensor elements, the thickness deviations are summarized by the common holding member by means of forming an average value. 
     The inputted fiber quantity for the drawing frame is altered as a function of the deviation of the actual value (average value) from a desired value. 
     The sensor elements are situated above the rotary roll forming a counter surface. 
     The leaf springs extend into the bight between two cooperating rolls between which the slivers pass. 
     The feed roll is stationarily supported. 
     The holding member is a hollow extruded member. 
     The extruded holding member is of aluminum or an aluminum alloy. 
     The holding member is provided at its end faces with a radially extending axle such as a bar or a pin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side elevational view, with block diagram, of a regulated drawing frame incorporating the invention. 
     FIG. 2 a  is a schematic sectional front elevational view of a preferred embodiment of the invention comprising a plurality of sensor elements and a stationary counterface. 
     FIG. 2 b  is a schematic side elevational view of the construction shown in FIG. 2 a.    
     FIG. 3 a  is a schematic perspective view of another preferred embodiment including a plurality of sensor elements and a rotary counterface. 
     FIG. 3 b  is a schematic side elevational view of the structure shown in FIG. 3 a.    
     FIG. 4 is a schematic side elevational view of a variant of the construction shown in FIGS. 3 a  and  3   b.    
     FIG. 5 is a schematic perspective view of yet another preferred embodiment of the invention including two cooperating transporting rolls. 
     FIG. 6 a  is a schematic top plan view of a preferred embodiment including a sliver guide with an integrated measuring device. 
     FIG. 6 b  is a sectional front elevational view of the embodiment of FIG. 6 a.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a drawing frame  1  which may be an HSR model manufactured by Trützschler GmbH &amp; Co. KG. The drawing frame  1  has a drawing unit  2  flanked upstream and downstream by a drawing unit inlet  3  and a drawing unit outlet  4 , respectively. The slivers  5  are withdrawn from coiler cans and enter a sliver guide  6  and are thereafter pulled therethrough by cooperating withdrawing rolls  7 ,  8  to cause the slivers  5  to run past the measuring member  9 . The drawing unit  2  is a four-over-three drawing unit, that is, it has a lower output roll I, a lower mid roll II and a lower input roll III as well as four upper rolls  11 ,  12 ,  13  and  14 . In the drawing unit  2  a drawing (stretching or drafting) of the sliver bundle formed of a plurality of slivers  5  takes place. The drawing unit has preliminary and principal drawing fields. The roll pairs  14 /III and  13 /II constitute the preliminary drawing field while the roll pair  13 /II and the roll unit  11 ,  12 /I form the principal drawing field. At the drawing unit outlet  4  the drawn slivers  5  reach a sliver guide  10  and are pulled through a sliver trumpet  17  by means of withdrawing rolls  15 ,  16  and are combined by the sliver trumpet  17  into a sliver  18  which is subsequently deposited into coiler cans. 
     The withdrawing rolls  7 ,  8 , the lower intake roll III and the lower mid roll II which are coupled to one another mechanically, for example, by a toothed belt, are driven by a regulating motor  19  with a pre-inputted desired value. The upper rolls  14  and  13  are driven by friction from the respective lower rolls III and II. The lower output roll I and the withdrawing rolls  15 ,  16  are driven by a main motor  20 . The regulating motor  19  and the main motor  20  are provided with a respective regulator  21  and  22 . The rpm regulation is effected by means of a closed regulating circuit in which a tachometer  23  is coupled with the regulating motor  19  and a tachometer  24  is coupled with the main motor  20 . At the drawing unit inlet  3  a magnitude of the sliver which is proportional to the sliver mass, such as its cross section, is measured by the inlet measuring member  9 . At the drawing unit outlet  4  the cross section of the exiting sliver  18  is determined by a sliver outlet measuring organ  25  associated with the sliver trumpet  17 . 
     A central computer unit  26  (control-and-regulating device), such as a microcomputer or a microprocessor transmits to the regulator  21  a setting of the desired magnitude for the regulating motor  19 . The measuring magnitudes of the two measuring members  9  and  25  are applied to the central computer unit  26  during the sliver drawing process. The central computer unit  26  determines the desired value for the regulating motor  19  from the measuring values of the inlet measuring member  9  and from the desired value for the cross section of the exiting sliver  18 . The measuring 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 a suitable regulation of the drawing process and thus an evening of the outputted sliver  18  may be achieved. 
     According to FIGS. 2 a  and  2   b , a plurality of side-by-side arranged sensor elements  30  are provided which are displaceable in the direction of the arrows B and C perpendicularly to the plane in which the slivers  5  lie. With one end of each sensor element  30  a respective spring  31  is associated which, at its other end, is secured to a throughgoing stationary holding member  32 . With each sensor element a transducer, such as an inductive path sensor is associated which converts the excursions of the sensor elements  30  into electric signals which are applied to a common electric adding device  34 . The summation signal  35  is used for regulation as shown in FIGS. 1 and 3 b . A throughgoing stationary slide element (supporting surface) such as a slide strip faces the other end of the sensor elements  30 . The slivers  5  pass between the sensor elements  30  and the slide element (counterface)  36 . Downstream of the measuring device  9  two cooperating driven rotary transport rolls  37  and  38  are arranged. In this manner, the thickness of all slivers  5  is individually measured at the inlet of the drawing frame, and a summation signal  35  is formed from the individual measuring signals. 
     According to FIGS. 3 a  and  3   b , the sensor elements  30  are formed by a plurality of side-by-side arranged leaf springs (measuring plates) which are affixed at one end to a common summation holder member  39  such as a summation beam, a measuring lever or the like. The other, free end of the leaf springs  30  is pressed against the respective slivers  5 . The mechanical summation holder member  39  is at both ends rotatably supported in bearings  40 ,  41  and is biased by a spring  42  in a clockwise direction as viewed in FIGS. 3 a  and  3   b . Further, with the summation holder member  39  a sensor  43  is associated which, according to FIG. 3 b , applies an electric summation signal to a regulator  44  connected to a drive motor  45  which rotates a roll  46 . The roll  46  which rotates in the direction F forms a movable counterface (supporting surface) for all the leaf springs  30 . Between the holder member  39  and the roll  46  a throughgoing feed table  47  is disposed for pivotal motion about a support  48  biased clockwise by a spring  49 . The slivers  5  are pulled in between the nip defined by the roll  46  and the feed table  47 . At the output side of the nip the slivers  5  are sensed for thickness by the leaf springs  30  which are movable in a direction indicated by the arrows E and D. This embodiment needs only a single sensor  43  sensing the rotary displacement of the summation element  39 . 
     According to FIG. 4, the roll  46  is associated with a guide roll  50  which rotates in the direction G and which serves for guiding and advancing the slivers  5 . 
     Turning to FIG. 5, the roll  46  is associated with a transporting roll  37 . The rolls  37 ,  46  rotate in the direction of the respective arrows H and I and define a bight, terminating in a nip through which the slivers  5  pass. The leaf springs (sensors)  30  extend into the bight and press on the slivers  5  from above, while the rotating upper face of the roll  46  serves as a counterface (supporting surface). 
     FIGS. 6 a  and  6   b  show an embodiment where the measuring device  9  is integrated in the sliver guide  6  having lateral walls  6   a  and  6   b  and a bottom wall  6   c . The leaf springs  30  cantilevered to the summation holding member  39  press down on a respective sliver  5  with their other, free end. This arrangement makes possible to sense a varying number of slivers, for example, instead of the shown eight slivers, only six slivers may be sensed. The lateral walls  6   a ,  6   b  cause the slivers to laterally converge, that is, the sliver bundle is laterally densified independently from the number of the slivers  5 . With each sliver  5  a respective sensor element  30  may be associated so that an individual measuring of the slivers  5  is achieved. It is, however, also feasible to associate a plurality of sensor elements  30  with a single sliver  5  or to assign a single sensor element  30  with more than one sliver  5 . The summation holding member  39  serves in each instance for adding the excursions of the sensor elements  30 . In this manner, a differentiated summation is achieved. 
     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.