Abstract:
A finishing device for finishing a surface of a workpiece includes a finishing belt, and a guide unit for guiding the finishing belt. The guide unit has a cup-shaped guide surface which bounds a receiving zone for the workpiece and along which the finishing belt is guided or guidable between an entry zone and an exit zone. The guide unit includes at least two separate guide members which have each a surface area, with the surface areas of the guide members jointly defining the guide surface and being movable relative to one another.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of European Patent Application, Serial No. EP 10166872.1, filed Jun. 22, 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 
     The present invention relates to a finishing apparatus for finishing a surface of a workpiece. 
     It would be desirable and advantageous to provide an improved finishing apparatus to obviate prior art shortcomings. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a finishing device for finishing a workpiece surface includes a finishing belt, and a guide unit for guiding the finishing belt, the guide unit having a cup-shaped guide surface which bounds a receiving zone for the workpiece and along which the finishing belt is guided or guidable between an entry zone and an exit zone, wherein the guide unit includes at least two separate guide members which have each a surface area, with the surface areas of the guide members jointly defining the guide surface and being movable relative to one another. 
     The guide members of a finishing apparatus according to the present invention can thus be moved independently from one another. As a result, the respective surface areas of the guide surface can be configured of particularly large dimensions and at the same time are able to act upon the finishing belt along their course with evenly distributed contact pressures so that the finishing belt can be pressed along its course about the workpiece surface to be treated evenly against the workpiece surface. As a consequence, the effective area of the finishing belt is enlarged while at the same time the contact pressure and thus the material removal capacity are increased. 
     According to another advantageous feature of the present invention, the guide members can be configured so as to be movable between an idle position and an operative position, with the guide surface extending in the idle position of the guide members between the entry zone and the exit zone over a first circumferential angle which permits introduction of the workpiece into the receiving zone and discharge of the workpiece from the receiving zone, and with the guide surface extending in the operative position of the guide members for treating the workpiece over a second circumferential angle which is greater than the first circumferential angle. The provision of a first smaller circumferential angle ensures that the workpiece can more easily be introduced into the receiving zone and withdrawn therefrom. The second greater circumferential angle enables an enlargement of the effective area of the finishing belt, thereby realizing a particularly high material removal capacity. 
     According to another advantageous feature of the present invention, the first circumferential angle can be equal to or smaller than 180° so that a workpiece to be treated can be introduced into the receiving zone and withdrawn therefrom free of undercuts. As a result, the finishing apparatus is easy to handle. 
     According to another advantageous feature of the present invention, the second circumferential angle may be greater than 180°. Currently preferred is a circumferential angle of more than approximately 200°. This results in a particularly large-area guide surface with a great wrap-around angle (equals the second circumferential angle), accompanied by a high material removal capacity. When at the same time the first circumferential angle is smaller or equal 180°, workpieces can be introduced free of undercuts into the receiving zone despite the substantial wrap-around angle during treatment. 
     The presence of a wrap-around angle or second circumferential angle of greater than 180° meets highest standards with respect to roundness. In addition, it is possible to work on not only rotation-symmetrical, e.g. cylindrical, workpiece surfaces but also on workpiece surfaces which in circumferential direction have only segments that are rotation-symmetrical. Such workpiece surfaces may, for example, be provided on balancer shaft bearings which have a part-cylindrical section and a flat section, as viewed along their circumference. Such workpiece surfaces may also be labeled as half-seat or part-seat as opposed to a full seat. By wrapping such a workpiece surface with a second circumferential angle of greater than 180°, undesired migration and/or tilting of such a workpiece surface with components of the guide unit is prevented. 
     According to another advantageous feature of the present invention, the guide unit has a maximum of two separate guide members. These guide members have neighboring surface areas which are however not connected and may each extend over a circumferential angle of greater than 90°. 
     According to another advantageous feature of the present invention, a holder can be provided to movably support at least one of the guide members. This results in a particularly simple construction of the guide unit. Currently preferred is a movable support of all guide members of the guide unit on the holder. 
     According to another advantageous feature of the present invention, a holder can be provided to swingably support at least one of the guide members. Currently preferred is a swingable support of all guide members of the guide unit on the holder. This configuration results in an especially suitable geometry, useful for treating workpieces that have at least one rotation-symmetrical section. Advantageously, the pivot axes may be oriented in substantial parallel relationship to a workpiece axis of a workpiece received in the receiving zone. 
     According to another advantageous feature of the present invention, the at least one of the guide members can be swingable about a first axis, and the workpiece in the receiving zone is defined by a second axis in parallel relationship to the first axis, with the first and second axes defining a plane which intersects at least in approximation in midsection the surface area of the at least one of the guide members. In this way, the contact pressure is evenly distributed. 
     According to another advantageous feature of the present invention, a force-application mechanism may be provided for holding the guide members in the idle position. This is beneficial because the guide members can be kept, without influence by a workpiece, in their idle position, accompanied with the first, i.e. smaller, circumferential angle. This greatly simplifies introduction of a workpiece to be treated into the receiving zone. 
     According to another advantageous feature of the present invention, the guide members can be transferred from the idle position to the operative position by the workpiece surface when the workpiece is placed in the receiving zone. This is advantageous because it eliminates the need for the provision of a principally conceivable but more complex drive to implement the transfer of the guide members from the idle position to the operative position. Thus, the workpiece surface to be treated can be utilized to press against the finishing belt which in turn is pressed against the surface areas of the guide members. This means that the guide members are transferred from the idle position to the operative position solely by the force applied by the workpiece, possibly in opposition to the action of an afore-mentioned force-application mechanism. 
     According to another advantageous feature of the present invention, the guide surface may have at least one area which yields elastically in a radial direction so as to be malleable. As a result, the workpiece surface can be treated in a particular gentle manner. The elastic resilience may be realized for example by making the surface areas of the guide surface of elastically malleable material, such as elastomer. 
     According to another advantageous feature of the present invention, at least one of the guide members can be supported in an elastically yielding manner in a radial direction. In this way, the spatial position of a bearing axis of a guide member can be adjusted, at least slightly, to effect a particularly gentle and very precise treatment of the workpiece surface. 
     A finishing apparatus according to the present invention is applicable for finishing a rotation-symmetrical workpiece surface, which may be cylindrical or spherical. A finishing apparatus according to the present invention may also be applicable for finishing a segment of a rotation-symmetrical workpiece surface, as viewed in a circumferential direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       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: 
         FIG. 1  is a side view of a finishing apparatus with a guide unit, shown schematically; 
         FIG. 2  is a perspective illustration of the guide unit of  FIG. 1 ; 
         FIG. 3  is a plan view of the guide unit, taken along the line III-III in  FIG. 2 ; and 
         FIG. 4  is a side view of a variation of a guide unit. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     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. 
     Turning now to the drawing, and in particular to  FIG. 1 , there is shown a side view of a finishing apparatus, generally designated by reference numeral  10 . The finishing apparatus  10  includes a pressing device, generally designated by reference numeral  12  and provided with at least one arm  14  and an optional second arm  16 . The arms  14 ,  16  are swingably supported so as to be movable in a direction towards a workpiece  18  which defines a central workpiece axis  20 . The workpiece  18  may involve for example a crankshaft having a center bearing or pin bearing to undergo a finishing process. The workpiece surfaces to be treated may be configured as full seat having a workpiece surface which is cylindrical about its entire circumference or as part-seat having a workpiece surface with segments of cylindrical configuration about the circumference. 
     The finishing apparatus  10  includes a finishing belt  22  which is shown in dash-dot line in  FIG. 1 . The finishing belt  22  originates from a finishing belt source  24  and routed in substantial radial direction towards the workpiece  18  and brought into contact in the region of an entry zone  26  for the finishing belt  22  with a workpiece surface  28  to be treated of the workpiece  18 . The finishing belt  22  is routed starting from the entry zone  26  between a guide unit  30 , schematically indicated in  FIG. 1  only by a broken line, and the workpiece surface  28  and up to a finishing belt exit zone  32 . In the region of the exit zone  32 , the finishing belt  22  is routed away from the workpiece surface  28  substantially radially outwards and away from the workpiece  18 . 
     The further course of the finishing belt  22  leads over deflection rollers  34 ,  36 , with a tensioning device  38  tightening the finishing belt  22 . The tensioning device  38  has a tension element  40  which acts upon the finishing belt  22  and serves at the same time as a deflection element. The tensioning device  38  is firmly connected with the first arm  14 . 
     The guide unit  30  is mounted onto the first arm  14 , for example by a threaded connection  42 . 
     When undergoing the finishing process, the workpiece  18  is caused to rotate about the workpiece axis  20  by a not shown drive unit. The finishing belt  22  may either be at a standstill or moved in a direction indicated by arrow  44  to increase the cutting speed during treatment of the workpiece surface  28 . The arm  14  of the pressing device  12  applies in the direction of the workpiece  18  a contact force by which the guide unit  30  applies a pressure upon the finishing belt  22  and by which the finishing belt  22  applies a pressure upon the workpiece surface  28 . 
     The configuration of the guide unit  30  will now be described in greater detail with reference to  FIGS. 2 and 3 . 
     The guide unit  30  includes a holder  46  which is connectable to the first arm  14 , for example by screw fasteners  42 , shown in  FIG. 1 , and/or screw fasteners  48 , shown in  FIG. 2 . The holder  46  has for example a substantial C-shaped configuration and includes a rear plate  50  and two supports  52 ,  54  extending out from the plate  50 . The supports  52 ,  54  are provided to bear further components to be described hereinafter. Secured to the supports  52 ,  54  are deflection rollers  56 ,  58  through intervention of mountings  60 , respectively. The holder  46  is also provided to establish pivot axes  62 ,  64  which, as shown by way of example, are oriented in parallel relationship. The pivot axes  62 ,  64  define the bearing axes for guide members  66 ,  68 , respectively, which are swingable about the pivot axes  62 ,  64 , respectively. The guide member  66  has a surface area  70  and the guide member  68  has a surface area  72 , with the surface areas  70 ,  72  forming jointly a guide surface  74  which extends between the entry zone  26  and the exit zone  32  for the finishing belt  22 . The surface areas  70 ,  72  adjoin one another but are independently movable from one another. 
     Support of the guide members  66 ,  68  on the holder  46  may be realized by bearing pins  76  ( FIG. 3 ) which extend in coaxial relationship to the pivot axes  62 ,  64 . The bearing pins  76  may be connected in fixed rotative engagement with the support  52  of the holder  46 . A particular low-friction support of the guide members  66 ,  68  is established by the use of rolling-contact bearings such as ball bearings. 
     The guide unit  30  further includes a force-application mechanism, generally designated by reference numeral  80 . In a simplest construction, the force-application mechanism  80  includes at least one spring  82  which maintains the guide members  66 ,  68  under tension. In this way, the guide members  66 ,  68  can be held in an idle position. In the non-limiting example shown in  FIG. 2 , two springs  82 ,  84  are provided which are fixed in place in relation to the holder  46  and may for example be articulated to an articulation  86 . 
     The ends of the springs  82 ,  84  in distal relationship to the articulation  86  are respectively connected to the guide members  66 ,  68 . The force-application mechanism  80  generates a tension force to move the surface areas  70 ,  72  towards one another so as to establish a first circumferential angle  88  defined by the surface areas  70 ,  72 . The circumferential angle  88  is at most approximately 180°, especially maximal 180°. 
     Referring now to  FIG. 4 , there is shown a side view of a variation of a guide unit  30 . Parts corresponding with those in  FIGS. 2 and 3  are denoted by identical reference numerals and not explained again. The description below will center only on the differences between the embodiments. In this embodiment, provision is made for slide bearings  90 ,  92  to support the guide members  66 ,  68 , respectively, on the holder  46 . In the non-limiting example of  FIG. 4 , the slide bearings  90 ,  92  include bearing pins  94 ,  96 , respectively, which are connected in fixed rotative engagement with the holder  46  and on which a bearing surface of the guide members  66 ,  68  slides so that the guide members  66 ,  68  are swingable about the pivot axes  62 ,  64 , respectively. The bearing pins  94 ,  96  may optionally be guided in elastic bearing bushings which permit a radial mobility of the pivot axes  62 ,  64 . 
     Otherwise, structure and mode of operation of the guide unit  30  according to  FIGS. 2 and 3  is the same as the structure and mode of operation of the guide unit  30  according to  FIG. 4  so that the following description is applicable to both embodiments. 
     The guide surface  74  formed by the surface areas  70 ,  72  bounds a receiving zone  98  ( FIG. 2 ) which receives the workpiece  18  ( FIG. 4 ). The disposition of the pivot axes  62 ,  64  is selected such that respective imaginary planes  100 ,  102 , in which the pivot axes  62 ,  64  and the workpiece axis  20  are oriented in substantial parallel relationship, intersect the surface areas  70 ,  72  at least in approximation in midsection thereof. 
       FIG. 4  shows the lower guide member  68  in its idle position. The surface area  72  of the guide member  68  is hereby inclined so as to enlarge the receiving zone  98  and thereby facilitate introduction of workpiece  18  into the receiving zone  98 . As the workpiece  18  is introduced into the receiving zone  98 , the workpiece surface  28  comes into contact with the finishing belt  22 , which is not shown in  FIGS. 2 and 4  for ease of illustration, so that the finishing belt  22  in turn comes into contact with the surface areas  70 ,  72  of the guide members  66 ,  68 , respectively. As a result, the guide members  66 ,  68  are moved from their idle position to their operative position.  FIG. 4  shows the operative position with respect to the upper guide member  66 . In the operative position, the surface areas  70 ,  72  embrace the workpiece  18  at a second circumferential angle  104  which is greater than the first circumferential angle  88 , shown in  FIG. 3 . 
     The second circumferential angle  104  is advantageously selected to exceed 180°. 
     In the operative position of the guide members  66 ,  68 , the workpiece surface  28  of the workpiece  19  undergoes a finishing operation. The workpiece surface  28  may be configured entirely rotation-symmetrical or may only have segments of rotation-symmetrical configuration and a section  106  shown in  FIG. 4  by dashed line and deviating from a rotation-symmetric configuration. When working on a workpiece  18  that is not entirely rotation-symmetrical, the swinging support of the guide members  66 ,  68  renders it possible for the guide members  66 ,  68  to execute a pendulum motion, with the guide members  66 ,  68  moving back and forth alternatingly as a result of the action of a rotation-symmetrical section of the workpiece surface  28  and the action of the force-application mechanism  80 . 
     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.