Abstract:
A device for measuring the feed motion of a finishing belt includes a movable contact section for contacting the finishing belt, wherein a movement of the finishing belt can be transferred to the contact section, and a sensor device including a sensor and a reference section cooperating with the sensor, wherein the reference section or the sensor is motionally coupled with the contact section.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of European Patent Application, Serial No. 10 191 368.9, filed Nov. 16, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a device for measuring the feed motion of a finishing belt. 
         [0003]    It is known to provide sensors for monitoring a belt transport in systems for finish-machining of substantially cylindrical workpiece surfaces. 
         [0004]    However, there is still a need to provide an improved device for measuring the feed motion of a finishing belt which enables a precise measurement of the feed motion of the finishing belt with high reliability. 
       SUMMARY OF THE INVENTION 
       [0005]    According to one aspect of the present invention, a device for measuring a feed motion of a finishing belt includes a movable contact section contacting the finishing belt, wherein a movement of the finishing belt is transferred to the contact section, and a sensor device having a sensor and a reference section cooperating with the sensor, wherein the reference section or the sensor is motionally coupled with the contact section. 
         [0006]    The device according to the invention has, on one hand, a contact section which is movably driven by moving the finishing belt and, on the other hand, the movement of the contact section is motionally coupled with the reference section, which cooperates with an, in particular, stationary sensor or with a sensor which cooperates with an, in particular, stationary reference section. Preferably, the reference section is motionally coupled with the contact section and the sensor is stationary. 
         [0007]    By providing both a contact section and a reference section, the movement of the finishing belt is transferred to the contact section independent of the function of the sensor device. In this way, the movement of the finishing belt can be particularly reliably transferred to the contact section. With the sensor device, which is provided separately from the contact section, a particularly precise measurement of the feed motion of the finishing belt can be performed. It is sufficient that the contact section is motionally coupled with the reference section or with the sensor. 
         [0008]    According to an advantageous feature of the present invention, continuously changing sensor signals may be generated with the sensor device. For example, the sensor device may generate analog signals depending on the cooperation with the reference section. These can be transformed into digital signals, if needed. 
         [0009]    According to another advantageous feature of the present invention, the sensor device may be a distance measuring device or a gap measuring device. For example, a path traveled by the reference section or by a portion of the reference section may be measured with the sensor device; or a gap between the reference section and the sensor or between a portion of the reference section and the sensor may be measured. With both embodiments, the relative position between the reference section and the sensor can be reliably and precisely measured. By motionally coupling the reference section or the sensor with the contact section, a movement of the contact section and hence of the finishing belt can be inferred from the movement of the reference section or of the sensor. 
         [0010]    According to yet another advantageous feature of the present invention, a particularly simple device for measuring the feed motion of a finishing belt may be constructed by moving the contact section and the references section in synchronism with each other. This further improves the precision of the device. 
         [0011]    According to yet another advantageous feature of the present invention, the structure becomes particularly simple by forming the reference section and the contact section from the same component or by employing an assembly having components that are prevented from moving relative to each other. A movement of the reference section or of the sensor then advantageously corresponds directly to a movement of the contact section. 
         [0012]    According to still another advantageous feature of the present invention, the contact section and the reference section may be rotatable about a common rotation axis. In this way, a compact device may be constructed which makes it possible to drive the contact section by rotatably feeding the finishing belt about a rotation axis, with the reference section then also rotating about the same rotation axis. 
         [0013]    According to another advantageous feature of the present invention, the contact section may be formed in the shape of a circular-cylindrical contact surface. The position and the path of the finishing belt are then independent of a rotation position of the contact section. 
         [0014]    According to an advantageous feature of the present invention, the reference section may be a reference surface having different radii of curvature along its extent. In this way, continuously changing sensor signals and hence a particularly precise measurement of the feed motion of the finishing belt may be produced in a particularly simple manner. 
         [0015]    According to another advantageous feature of the present invention, the structure of the device may be simplified by forming the reference surface as a cam disk. In another embodiment, the reference surface of the cam disk may represent a radially outwardly oriented surface. 
         [0016]    According to another aspect of the invention, an apparatus for finish-machining a workpiece includes the aforedescribed device for measuring the feed motion of a finishing belt and a drive device for feeding the finishing belt from a finishing belt supply to at least one workpiece processing location. With an apparatus of this type, the device according to the invention for measuring the feed motion of a finishing belt can also be used to determine that a finishing belt supply has been depleted and/or that a finishing belt is torn. For this purpose, the states of the device for measuring the feed motion of the finishing belt and of the drive device can be matched to one another and monitored. 
         [0017]    According to an advantageous feature of the present invention, the apparatus for finish-machining a workpiece may have a signal output device for outputting a warning signal which can be triggered when the device for measuring the feed motion of the finishing belt produces a constant sensor signal, although the drive device is active. In this way, a signal may be provided to the operating personnel of a finishing apparatus to indicate that a finishing belt supply has been depleted and/or that a finishing belt is torn. 
         [0018]    The activity of the drive device may also be monitored, for example, by monitoring the operating state of a drive motor which unwinds the finishing belt from a finishing belt supply via corresponding drive elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0019]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0020]      FIG. 1  shows a front view of an embodiment of an apparatus for belt-finishing processing of a workpiece according to the invention, wherein the apparatus includes a device for measuring the feed motion of a finishing belt; 
           [0021]      FIG. 2  an enlarged view of the device according to  FIG. 1 ; and 
           [0022]      FIG. 3  a side view of the device according to  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0024]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown an embodiment of an apparatus according to the invention, indicated with the reference symbol  10 , for finish-machining of a workpiece. The apparatus  10  includes a machine frame  12  and two arms or claws  14  and  16 , respectively, which are pivotable about their respective associated pivot axes  18  and  20 . Separate drives may be provided for pivotally driving each of the arms  14  and  16 ; or a common claw drive can be provided, wherein the movement of the arms  14  and  16  is coupled with one another, for example via a coupling member  22  which transfers a pivot motion of one of the arms  14  to the other arm  16 . 
         [0025]    The free ends  24  and  26  of the arms  14  and  16  include pressure elements  28  and  30  connected with the arms. The pressure elements  28  and  30  have curved contour surfaces  32  and  34  which are adapted to the circumference of a workpiece  36  to be finish-machined. The workpiece  36  can be rotated or pivoted about a workpiece axis  38 . Optionally, the workpiece may also be driven in an oscillating motion, meaning oscillating back and forth, in the direction along the workpiece axis  38 . 
         [0026]    The apparatus  10  further includes a supply  40  for a finishing belt  42 , the path of which is indicated by a dashed-double dotted line. The supply  40  may be, for example, a roll on which the finishing belt is wound up and from which the finishing belt can be unwound. 
         [0027]    Starting from the supply  40 , the finishing belt  42  passes through a device  44 , which is described in more detail below, for measuring the feed motion of the finishing belt  42  in an feed motion direction  46 . The finishing belt  42  is then diverted by a deflection roller  48  and fed to a first workpiece processing position  50  which extends along part of the circumference of a surface  52  of the workpiece  36  to be machined and along the contour surface  34 . At the exit of the workpiece processing position  50 , the finishing belt  42  is guided, in relation to the workpiece axis  38 , approximately radially outwardly to a deflection roller  54 . From the deflection roller  54 , the finishing belt  42  then reaches a second workpiece processing position  56  along part of the circumference of the surface  52  of the workpiece  36  and along the contour surface  32 . The finishing belt then moves from the exit of the workpiece processing position  56  to an additional deflection roller  58  and from there to a collector  60  for the spent finishing belt. 
         [0028]    For driving the finishing belt  42  in the feed motion direction  46 , a drive device  62  is provided which is located, when viewed in the feed motion direction  46 , after the last workpiece processing position  56  and which pullingly drives the finishing belt  42 . For this purpose, for example, two drive rollers  64  are provided, which frictionally contact a front side  66  and a backside  68  of the finishing belt and unwind the finishing belt  42  from the finishing belt supply  40  by rotating the drive rollers  64 . 
         [0029]    For belt-finishing machining of the workpiece  36 , a fresh belt section is supplied to the workpiece processing position  50 , causing a belt section of corresponding length to be supplied to the finishing belt collector  60 . While the workpiece  36  is machined, the workpiece  36  is rotatably driven by a conventional (unillustrated) drive for rotation about the workpiece axis  38 . If desired, the workpiece  36  is additionally driven with an oscillating motion in a direction parallel to the workpiece axis  38 . The front side  36  of the finishing belt  42  is provided with a material effective for finishing, which is pressed by the contour surfaces  32  and  34  of the pressure elements  28  and  30  against the surface  52  of the workpiece. 
         [0030]    When the finishing belt  42  is spent in the region of a workpiece processing position  50  and/or  56 , fresh finishing belt  42  is pulled in by the drive device  62 . The length of the pulled-in finishing belt  42  is measured with the device  44  described below (see  FIGS. 2 and 3 ). 
         [0031]    The device  44  includes a component  70  which is supported for rotation about a, in particular stationary, rotation axis  72 . 
         [0032]    The component  70  includes a contact section  74  for contacting the finishing belt  42 . The contact section  74  is formed by a circular-cylindrical contact surface  76  which is surrounded along a portion of its circumference by the finishing belt  42  and which contacts the backside  68  of the finishing belt  42 . For providing a wrap angle, additional deflection rollers  78  and  80 , respectively, are arranged at the inlet and exit of the device  44 . 
         [0033]    The component  70  includes a reference section  82  which is arranged, when viewed along the rotation axis  72 , next to the contact section  74  and which can be rotated together with the contact section about the rotation axis  72 . The reference section  82  is formed in the shape of a cam disk  84  which can be rotated about the rotation axis  72 . 
         [0034]    The cam disk  84  has at its periphery a radially outwardly oriented reference surface  86 . The gap between the reference surface  86  and the rotation axis  72  varies, when viewed in the rotation direction, between a smallest gap  88  and a largest gap  90 . Accordingly, a particular gap between the reference surface  86  and the rotation axis  72  is associated with each possible rotation position of the component  70 . In this way, a stationary sensor  92  can measure different gaps between the reference surface  86  and an effective sensor area  94  depending on the rotation position of the component  70 . 
         [0035]    The sensor  92  and the reference section  82  together form a sensor device  96 . In the illustrated exemplary embodiment, the sensor device  96  is a distance measuring device. 
         [0036]    Wherein the finishing belt  42  is unwound from the finishing belt supply of  40  in the feed motion direction  46 , the finishing belt transfers is motion to the contact surface  76 . The component  70  is hereby rotated about the rotation axis  72 , causing the gap between the reference surface  86  and the effective surface  94  of the sensor  92  to change commensurate with the rotation. The size of this change corresponds with a corresponding feed path of the finishing belt  42 . 
         [0037]    When the component  70  has reached a rotation position illustrated in  FIGS. 2 and 3 , wherein the effective surface area  94  of the sensor  92  measures a jump from the smallest gap  88  between the reference surface  86  and the rotation axis  72  to the largest gap  90  between the reference surface  86  and the rotation axis  72 ; subsequently, this rotation position is measured a second time, accompanied by a feed motion of the finishing belt  42  according to a length which corresponds to the circumference of the circular-cylindrical contact surface  76 . The spacing between the effective surface  94  and the reference surface  86  changes continuously commensurate with the continuously changing gap between the reference surface  86  and the rotation axis  72 , allowing the measurement of a feed motion of any length with the highest possible precision. 
         [0038]    For supplying fresh finishing belt to the workpiece processing positions  50  and  56 , the arms  14  and  16  are pivoted radially outwardly from their position indicated in  FIG. 1 , with respect to the workpiece axis  38 , about the pivot axes  18  and  20 , so that the contour surfaces  32  and  34  are no longer pressed against the workpiece surface  52 . In this state, the drive device  62  can be controlled so as to pull in the finishing belt  42 . The state of the drive device  62  can also be determined. If the drive device  62  is active and if simultaneously the device  44  fails to measure a feed motion of the finishing belt  42 , then it can be concluded that the finishing belt  42  is torn or that the finishing belt  42  has been completely unwound from the finishing belt supply  40 . In this situation, a warning signal, for example in form of a warning light, can be outputted with a signal output device (not shown in the drawing). 
         [0039]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0040]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: