Abstract:
A permanently excited magnetic hysteresis brake ( 1 ) comprises a support roller ( 7 ) rotatable about a fixed axle ( 9 ), a magnetic element ( 3 ), a hysteresis element ( 2 ) and an adjusting device for adjusting the position of the magnetic element ( 3 ) and hysteresis element ( 2 ) relative to one another and for adjusting the braking torque acting via the support roller ( 7 ) on the yarn ( 5 ). The magnetic hysteresis brake ( 1 ) has only one single mechanically acting actuator ( 18 ) for adjusting the braking torque. Both the adjustment of the braking torque to the desired value for the operation of the brake ( 1 ) and the adjustment of the braking torque when calibrating the brake ( 1 ) are carried out by actuation of this one actuator ( 18 ). The structure and handling of the magnetic hysteresis brake ( 1 ) can be simplified thereby. The magnetic hysteresis brake ( 1 ) can be used to maintain a uniform thread tension on textile machines.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of German patent application 10 2006 007 924.8, filed Feb. 21, 2006, herein incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a method for adjusting the braking torque of a permanently excited magnetic hysteresis brake by means of a mechanically acting actuator and a permanently excited magnetic hysteresis brake for carrying out such method.  
         [0003]     Hysteresis brakes allow a uniform tension to be maintained without acting on the yarn with a friction which can damage the yarn. The yarn passes through the magnetic hysteresis brake at a predetermined speed. The yarn is thus guided via a roller, with it completely or partially looping the roller and being acted upon by the braking action of the magnetic hysteresis brake. The braking torque is independent of the rotational speed.  
         [0004]     Hysteresis brakes are used in the textile industry, for example in the production of twisted yarn or the winding of yarn on bobbins.  
         [0005]     German Patent Publication DE 19705290 A1 describes a permanent magnet-excited hysteresis brake with a roller, a hysteresis ring and a magnetic ring provided with magnetic poles. The hysteresis ring is rotationally fixed to the roller. The magnetic ring is fastened to a support part, which is axially displaceably mounted relative to the hysteresis ring by means of an adjusting device. The adjusting device comprises a thread attachment on the support part and a threaded spindle on an adjusting ring, which is axially fixed, but rotatable. By rotating the adjusting ring, the magnetic ring is displaced relative to the hysteresis ring. The displacement brings about a change in the braking torque of the hysteresis brake. The axial arrangement of the roller is adjusted by means of a central screw, which presses the roller against a central axial spring. The rotation of the screw allows a basic adjustment of the immersion depth of the magnetic ring in the hysteresis ring and therefore a calibration of the hysteresis brake. With the hysteresis brake from German Patent Publication DE 19705290 A1 it is necessary for the adjustment of the braking torque for the operation and for the adjustment of the braking torque during the calibration, to keep in readiness and actuate two different adjusting devices.  
       SUMMARY OF THE INVENTION  
       [0006]     Proceeding from the aforementioned prior art, the invention is based on the object of improving the magnetic hysteresis brake for the adjustment of the braking torque.  
         [0007]     This object is achieved by a method for adjusting a braking torque of a permanently excited magnetic hysteresis brake by means of a mechanically acting actuator. According to the invention, both the adjustment of the braking torque to a desired valued for the operation of the magnetic hysteresis brake and the adjustment of the braking torque when calibrating the magnetic hysteresis brake can be carried out by means of actuation of the same actuator.  
         [0008]     The invention further provides a permanently excited magnetic hysteresis brake for carrying out such method, utilizing a support roller, which can be rotated about a fixed axle, with at least one magnetic element and at least one hysteresis element. The magnetic element and the hysteresis element are separated from one another by an air gap. An adjusting device enables adjustment of the position of the magnetic element and hysteresis element relative to one another. Therefore, the torque with which the support roller is acted upon as a braking torque can be adjusted. The adjusting device comprises an actuator which can be rotated about the axle. According to the invention, the magnetic hysteresis brake has only a single actuator, with which the braking torque can be adjusted both for the operation of the magnetic hysteresis brake and during the calibration of the magnetic hysteresis brake.  
         [0009]     The additional components such as separate actuators and adjusting devices for the calibration required in the previously known magnetic hysteresis brake for adjusting the braking torque to a desired value for the operation of the magnetic hysteresis brake are dispensed with in the magnetic hysteresis brake according to the invention and the costs for them are saved. Handling of the magnetic hysteresis brake is simplified.  
         [0010]     If the actuator has a scale and the magnetic hysteresis brake comprises a cover, which carries a marking, and if the scale and the marking are arranged such that they cooperate as a display device, precise and reproducible adjustment of certain braking torques is possible.  
         [0011]     The magnetic hysteresis brake advantageously has a connection between the cover and the axle, which is released or fixed as a function of the respective adjusting process. To adjust a braking torque for the calibration process, the connection is released and the actuator and the cover are rotatable together about the fixed axle. To adjust a braking torque for operation, the cover is rigidly connected to the axle, while the actuator can be rotated relative to the now fixed cover. Thus it is possible in a simple manner to carry out the adjustment of the braking torque in the two adjusting processes with only a single actuator.  
         [0012]     A screw connection is a simple and reliable connection, which can be released with little effort, between the cover and the axle.  
         [0013]     In a coupling, which is preferably configured as a latching connection, between the lid and actuator, the force exerted by the coupling is large enough to entrain the cover when adjusting a braking torque for the calibration process when the actuator is rotated about the fixed axle, so no rotation takes place between the actuator and cover. The force which can be exerted by the latching connection is small enough when adjusting or setting a braking torque for operation to be able to rotate the actuator by hand relative to the cover, which is rigidly connected to the fixed axle. Owing to the coupling, the actuator remains locked in the respectively adjusted position with respect to the cover. An adjusting ring as an actuator allows a compact configuration of the magnetic hysteresis brake.  
         [0014]     The hysteresis element is preferably rigidly connected to the support roller and the magnetic element is fastened to a holder, which is rotationally fixed with respect to the fixed axle and displaceable relative to the hysteresis element by means of the adjusting device in the axial direction of the fixed axle. The actuator and the holder advantageously have a thread in each case, and the threads mesh with one another in such a way that a rotation of the actuator brings about an axial displacement of the holder.  
         [0015]     In an alternative embodiment, the hysteresis element is rigidly connected to the support roller and the magnetic element is fastened to a holder which is coupled so as to be rotatable about the fixed axle and rotationally fixed to the actuator and which is displaceable by means of the adjusting device relative to the hysteresis element in the axial direction of the axle. The adjusting device advantageously comprises a cam disc which is carried by the axle and has at least one ramp, the holder being supported on the ramp and the cam disc being configured and arranged such that a rotation of the holder brings about an axial displacement of the holder. The surface of the ramp preferably extends helically about the axle. In the use of a cam disc, in comparison to a thread, a significantly lower adjusting force is required.  
         [0016]     These known embodiments allow reliable and precise adjustment of the braking torque of the magnetic hysteresis brake and are a simple and space-saving with regard to structure.  
         [0017]     If the air gap between the magnetic element and the hysteresis element lies in a plane transverse to the fixed axle, a compact arrangement of the hysteresis ring and magnetic ring is possible.  
         [0018]     The magnetic hysteresis brake according to the invention can be produced in a compact and economical manner and allows simple handling. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The invention will be described in more detail with the aid of the figures, in which:  
         [0020]      FIG. 1  shows a longitudinal section through a magnetic hysteresis brake according to the invention,  
         [0021]      FIG. 2  shows a cross-section A-A through the magnetic hysteresis brake of  FIG. 1 ,  
         [0022]      FIG. 3  shows a perspective view of the cross-section of  FIG. 2 ,  
         [0023]      FIG. 4  shows a perspective view of the end face of the magnetic hysteresis brake of  FIG. 1 ,  
         [0024]      FIG. 5  shows the magnetic hysteresis brake according to the invention set up for the calibration process,  
         [0025]      FIG. 6  shows the longitudinal section through a magnetic hysteresis brake with a cam disc.  
         [0026]      FIG. 7  shows the cam disc of  FIG. 6  in a perspective view. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]      FIG. 1  shows the operating position of the magnetic hysteresis brake  1  according to the invention. The magnetic hysteresis brake  1  has a hysteresis element configured as a hysteresis ring  2  and a magnetic element  3 . The hysteresis ring  2  and the magnetic element  3  are spaced apart from one another by an air gap  4 .  
         [0028]     The spacing a between the hysteresis ring  2  and magnetic element  3  can be changed by means of an adjusting device. The smaller the spacing a, the greater is the braking torque, with which the magnetic hysteresis brake  1  acts on the running yarn  5 . The running yarn  5  lies in one or, as shown in  FIG. 1 , in a plurality of loops on the casing tube  6 , which is rotationally fixed to the support roller  7 . The support roller  7  is rotatably mounted by means of two ball bearings  8  on the axle  9 . A uniform thread tension, which depends on the adjusted braking torque with regard to its level is provided for the running yarn  5 . The fixed axle  9  can be fastened by a screw connection by means of a threaded bore  10  to a stationary machine part of a textile machine, such as, for example a support arm or a frame part. The hysteresis ring  2  is rigidly connected by gluing to the support roller  7 . The magnetic element  3  comprises a pole disc  11  and permanent magnets configured as round magnets  12 , which are fixed to the pole disc  11 . The round magnets  12  are symmetrically arranged about the axle  9 , as shown in  FIGS. 2 and 3 . The magnetic element  3  is fastened to a holder  13  by means of screws  14 . The holder  13  is axially displaceable on the axle  9 . A feather key  15  secures the holder  13  against rotation on the axle  9 . The holder  13  has an inner thread  16 , which engages in the thread of a threaded spindle  17 . The threaded spindle  17  is part of an actuator configured as an adjusting ring  18 . The adjusting ring  18  is rotatable on the axle  9  and not axially displaceable thereon. An axial movement of the adjusting ring  18  is prevented, on one side, by the step  19  of the axle  9  and, on the other side, by the cover  20 . Both the cover  20  and the adjusting ring  18  consist of plastics material. In the view of  FIG. 1 , the cover  20  is fixed at the free end of the axle  9  by means of a hexagon socket screw  21 . The adjusting ring  18  has a scale  22  and can be rotated relative to the cover  20 . By means of a latching, the respective position of the adjusting ring  18  can be reproducibly adjusted. The cover  20  comprises flutes  24  which are arranged circumferentially similar to an internal ring gear. A resilient tongue  23  of the adjusting ring  18  engages in the flutes  24 . The coupling, adjusting ring  18  and cover  20 , are coupled with the latching connection, which is formed by the engagement of the resilient tongue  23  in the flutes  24 . The resistance with which the coupling counteracts the manual rotation of the adjusting ring  18  is slight and easy to overcome. The tongue  23 , on ending the rotation of the adjusting ring  18 , in each case latches in a flute  24 . The latching allows an exact reducibility of the selected adjustment of the breaking torque. The scale  22 , together with a marking arrow  25  applied to the cover  20 , forms a display device. The marking arrow  25  shows the level of the respectively adjusted braking torque on the scale  22 .  FIG. 1  represents the operating state of the magnetic hysteresis brake  1 , in which the braking torque of the magnetic hysteresis brake  1  can be adjusted to a desired value. For adjustment, the adjusting ring  18  is rotated such that the marking arrow  25  points to the desired value on the scale  22 . If the adjusting ring  18  is adjusted anti-clockwise in the view of  FIG. 4 , the holder  13  in the view of  FIG. 1  is displaced to the left by this rotation via the threaded spindle  17  and the inner thread  16 . The spacing a, which represents the width of the air gap  4  between the round magnets  12  and the hysteresis ring, thus becomes smaller, the slip power of the magnetic hysteresis brake  1  increases and the braking torque of the magnetic hysteresis brake  1  becomes larger. Accordingly, the braking torque on rotation of the adjusting ring  18  in the clockwise direction becomes smaller as the displacement of the holder  13  now increases the spacing a.  
         [0029]     Most parts of the magnetic hysteresis brake  1  are surrounded and protected by the tubular casing tube  6 .  
         [0030]      FIG. 5  shows the magnetic hysteresis brake  1  in the state prepared for the calibration process. In order to calibrate the magnetic hysteresis brake  1 , a specific torque or braking torque is input for a specific scale position, for example the position  1 . The specific torque or braking torque is, for example, 1 Ncm for the position  1 . The adjusting ring  18  is now adjusted such that the marking arrow  25  points to the position  1  of the scale  22 . The hexagon socket screw  21 , which has until now fixed the cover  20  on the axle  9 , is then released until the cover  20  can be rotated about the axle  9 . If the adjusting ring  18  is now rotated, the spacing a between the magnetic element  3  and hysteresis ring  2  and therefore the braking torque generated by the magnetic hysteresis brake  1  is changed. The connection configured by the flutes  24  of the cover  20  and the resilient tongue  23  of the adjusting ring  18  as a latching device engages with a limited force on the cover  20 . This force is, however, sufficient to synchronously also entrain the cover  20  upon a rotation of the adjusting ring  18 . While the braking torque changes owing to the rotation of the adjusting ring  18 , the selected adjustment of the marking arrow  25  is retained at the determined position (position  1  in the example given above). The braking torque input for this position to calibrate the magnetic hysteresis brake  1  is adjusted precisely with the aid of a torque measuring apparatus, not shown. The hexagon socket screw  21  is tightened again and the cover  20  is fixed on the axle  9 . The allocation of the input torque to the determined position is fixed in this manner. The input torque can be reproduced by adjustment to this position. The magnetic hysteresis brake  1  is therefore calibrated and prepared for operation.  
         [0031]     In an alternative implementation of the calibration process, the cover  20  is initially not yet fitted. With the aid of a torque measuring apparatus, the input braking torque is adjusted by rotating the adjusting ring  18 . The cover  20  is then placed on the free end of the axle  9  in such a way that the marking arrow  25  points to-the position of the scale  22  corresponding to the braking torque. If the value of the adjusted braking torque is, for example 5 Ncm, the marking arrow points to the position  5  of the scale  22 . By tightening the hexagon socket screw  21 , the cover  20  is fixed to the axle  9  and the magnetic hysteresis brake  1  calibrated.  
         [0032]      FIG. 6  shows a magnetic hysteresis brake  26 , which has a cam disc  27 , in the operating position. The magnetic hysteresis brake  26  comprises a hysteresis element configured as a hysteresis ring  28  and a magnetic element  29 , which are axially spaced apart from one another by an air gap  30 . The magnetic element  29  is fastened to a holder  37 . The axial spacing between the hysteresis ring  28  and magnetic element  29  can be adjusted by means of an adjusting device using the cam disc  27 . The running yarn, not shown, lies in one or more loops on the casing tube  31 . The casing tube  31  is rotationally fixed to the support roller  32 , which is rotatably mounted by means of two ball bearings  33  on the axle  34 . The hysteresis ring  28  is rigidly connected to the support roller  32 . The magnetic element  29  comprises a pole disc  35  and permanent magnets configured as round magnets  36 , which are fixed on -the pole disc  35 . The axle  34  fixed by means of a screw, not shown, screwed into the threaded bore  38 , for example on a support arm or a frame part of a textile machine has a peripheral collar  39 . The axle  34  carries the cam disc  27 , the holder  37  and an actuator configured as an adjusting ring  40 .  
         [0033]     A cover  41  is fixed by means of a hexagon socket screw  42  to the free end of the axle  34  opposing the threaded bore  38 . The cover  41  carries a marking and the adjusting ring  40  carries a scale in the manner shown in  FIG. 4 . The scale of the adjusting ring  40 , together with the marking applied to the cover  41  forms a display device. The adjusting ring  40  is rotatably mounted on the axle  34 . As long as the cover  41  is fixed by means of the hexagon socket screw  42 , the adjusting ring  40  is not axially displaceable. The holder  37  is rotationally fixed to the adjusting ring  40  by a nose  43  of the adjusting ring  40 , which engages in a groove  44  of the holder  37  but is, however, axially displaceable with respect to the adjusting ring  40  and rotatable about the axle  34 . In this case, the holder  37  rests, under the action of the magnetic force, between the round magnets  36  and the hysteresis ring  28  with the cam  45  on the surface of the inner ramp  46  and with the cam  47  on the surface of the outer ramp  48  of the cam disc  27 . The surface of the inner ramp  46  and the surface of the outer ramp  48  of the cam disc  27  extend helically around the axle  34  or around the centre line  53  as shown in  FIG. 7 . The cam disc  27  is rotationally fixed to the axle  34  by means of the journals  49 ,  50  and is axially supported under the action of the magnetic force applied by the holder  37  against the collar  39  of the axle  34 . The stops  51 ,  52  limit the adjustment path of the cams  45 ,  47  on the surface of inner ramp  46  and the surface of the outer ramp  48  of the cam disc  27 .  
         [0034]     To adjust a specific torque or braking torque, the adjusting ring  40  is rotated about the centre line  53 . On rotation of the adjusting ring  40  and the holder  37  rotationally fixed thereto, the holder  37  rotates relative to the cam disc  27 , with the journals  49 ,  50  sliding on the surface of the inner ramp  46  and the surface of the outer ramp  48  as on an oblique plane and the holder  37  being displaced in the direction of the centre line  53  on the axle  34 . If the adjusting ring  40  is rotated in the clockwise direction viewed from the left in the view of  FIG. 6 , the axial spacing between the hysteresis ring  28  and the magnetic element  29  or the air gap  30  increases and the torque or braking torque acting on the yarn becomes smaller. In the case of a rotation in the opposite direction, the holder  37  is axially moved by the magnetic force acting as a restoring force and the air gap  30  becomes smaller. The air gap  30  which has become smaller leads to a greater torque or braking torque. To calibrate the magnetic hysteresis brake  26 , the procedure is similar to the calibration process already described in conjunction with the design of the magnetic hysteresis brake  1 . The cover  41  is initially fixed by means of the hexagon socket screw  42  on the axle  34 . The adjusting ring  40  is adjusted such that the marking of the cover  41  points to a specific position of the scale of the adjusting ring  40 . The inner socket hexagonal screw  42  is now released until the cover  41  can be rotated about the axle  34 . By rotating the adjusting ring  40 , the braking torque generated by the magnetic hysteresis brake  26  is changed. A connection configured as a latching device between the adjusting ring  40  and cover  41  also rotates the cover  41  synchronously when the hexagon socket screw  42  is released, so the selected adjustment of the marking is maintained at the specific position. The torque or braking torque input for this specific position is precisely adjusted with the aid of a torque measuring device, not shown. The hexagon socket screw  42  is tightened again and the cover  41  is fixed on the axle  34  again. The allocation of the input torque or braking torque to the specific position has now taken place and the magnetic hysteresis brake  26  is calibrated.  
         [0035]     The mechanical device present in a magnetic hysteresis brake according to the invention for changing the braking torque is thus suitable both to adjust the braking torque to a desired value for the operation of the magnetic hysteresis brake and to adjust the braking torque during calibration.  
         [0036]     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many. embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.