Patent Publication Number: US-6986703-B2

Title: Apparatus for processing substantially planar workpieces

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is entitled to the benefit of German Patent Application No. 102 44 733.0 filed on Sep. 25, 2002. 
   FIELD OF INVENTION 
   The present invention concerns an apparatus for processing substantially planar workpieces, which workpieces are moveable in a transport plane relatively to the apparatus, the apparatus including at least one grinding head having a tool carrier rotatable around a carrier axis orthogonal to the transport plane, on which tool carrier a plurality of grinding brushes each including a brush body and bristles attached to said body are individually mounted so that they are each rotatable around an individual brush axis. 
   BACKGROUND OF THE INVENTION 
   One such apparatus is for example known from U.S. Pat. No. 5,105,583, in which a machine for the deburring of internal and external burrs of metal workpieces is shown, in which the workpieces are moved in a horizontal transport plane relatively to the deburring machine. The deburring machine includes a planetary grinding head with a planet carrier which rotates around a vertical carrier axis at low speed. Inside the planet carrier three planet gears are mounted rotatably around vertical axes, which rotate at high speeds when the planetary grinding head is driven. Brushes, whose bristles are engaged vertically against the surface of the workpiece, are attached to the planetary gears. 
   An apparatus of the afore-mentioned kind not only serves for deburring, but also for removing oxide layers from cutting areas, which oxide layers are formed e.g. during the cutting of metal sheet plate to size with the help of laser beams or during autogenous cutting. Since such burrs usually protrude vertically from the workpiece surface, they will be removed during processing of said surface, while the cuffing areas extend perpendicularly to said surface and require processing in a processing plane perpendicular to the workpiece surface processing plane. 
   In order to be able to process the workpiece simultaneously in said processing planes which are perpendicular to each other, the brushes, which in an apparatus of the afore-mentioned kind are generally engaged against the workpiece surface, have to be sufficiently soft and yielding to reach both the surface and the cutting areas of the workpiece. The thicker the metal sheet plate to be processed is, the softer the bristles of the grinding brushes need to be so as to cover the entire cutting area, respectively, generally speaking, the edges of a workpiece. 
   However, the bristles may not exhibit any desired degree of softness, since their abrasive effect might become too small. Since it has recently become possible to cut metal sheet plate of increasing thickness to size by means of a laser, it is no longer possible to perform comprehensive processing of the edges of a workpiece by means of a known apparatus of the afore-mentioned type with satisfactory efficiency. 
   In the above-mentioned U.S. Pat. No. 5,105,583 it is suggested not to arrange the carrier spindle in an exact vertical direction (and thus not orthogonally to the transport plane, at variance from the wording of the preamble), but to tilt its upper end somewhat in the workpiece feeding direction which results in a higher pressure being exercised on the front face of the workpiece, which in turn causes an increase in the abrasive effect on the workpiece front face, while the abrasive effect on the lateral edges does not increase and the abrasive effect on the workpiece rear face even decreases. 
   It is an object of the present invention to provide an apparatus of the afore-mentioned kind which allows comprehensive and efficient processing of the edges of a workpiece also for comparatively thick workpieces. 
   This object is solved by an apparatus according to the present invention. This enables the bristles to process different portions of the workpiece edges in accordance with their respective distance to the transport plane. Thus, by selecting the distances of the bristles from the transport plane in a suitable manner, the entire width of the workpiece edges (i.e. the entire thickness of the workpiece) can be processed, while there is no need for using especially soft bristles. Thus, it is possible to achieve a far greater abrasive effect with the apparatus according to the present invention than with known apparatus. 
   Varying distances between the ends of the bristles and the transport plane can be reached in different ways. In a preferred embodiment of the invention the bristles on the individual grinding brushes differ in length. In another preferred embodiment the brush bodies are tilted with respect to the transport plane. In both cases, a good abrasive effect on the entire width of the workpiece edges is achieved, while the respective distances between the ends of the single bristles and the transport plane do not change during the rotation of the grinding brush. Since the bristles are arranged at different distances to the transport plane, however, they wear off unevenly. 
   In an improved embodiment, the brush bodies are tilted with respect to the transport plane, while the brush axes extend in an orthogonal direction with respect to the brush bodies. This means that the distance between each single bristle and the transport plane changes as the brush rotates around its brush axis. The brush itself can be rotationally symmetric with respect to the brush axis and thus wears off evenly. 
   Preferably, the distances between the ends of the bristles and the transport plane differ by up to 1 to 2 cm. In an advantageous embodiment the apparatus includes several planetary heads which are arranged in two rows extending transversely with respect to the workpiece transport direction with the rows being arranged one behind the other in the workpiece feed direction and with the two rows of planetary heads being offset towards each other transversely with respect to the workpiece transport direction such that the planetary heads of one row—when viewed in the workpiece transport direction—close the gaps between the planetary heads of the other row. By using such an arrangement also big workpieces, and in particular broad metal sheets, can be processed. 
   A further improvement can be achieved by using different types of bristles. Thus the bristles of at least one of the grinding brushes can differ from the bristles of the other grinding brushes in their material characteristics, structure, texture, hardness, thickness and/or trimming length. The different types of bristles may necessitate a different infeed of the grinding brushes in the direction of the workpiece in order to reach the desired results and may moreover exhibit different wear behaviour during their useful life. For this reason it is advantageous if the infeed of at least some of the grinding brushes can be regulated individually. It is also possible to control the infeed of sets of grinding brushes of the same type, for which purpose use may be made of a support element for grinding brushes of the same type which is centrally adjustable. In an alternative solution all grinding brushes are arranged within a common support element such that they can be axially adjusted with sets of like grinding brushes being adjustable via a common operating device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention will be apparent from the following description in which the solution according to the present invention is explained in more detail by way of exemplary embodiments and with reference to the accompanying drawings. The drawings are: 
       FIG. 1  a plan view of an apparatus according to one embodiment of the present invention, 
       FIG. 2  a side view of the apparatus of  FIG. 1 , 
       FIG. 3  a schematic sectional view of a metal sheet plate whose edge is processed by means of a grinding brush of a known apparatus, 
       FIG. 4  a schematic sectional view of a metal sheet plate whose edge is processed by means of a grinding brush of an apparatus according to one embodiment of the present invention, 
       FIG. 5  a schematic sectional view of a metal sheet plate whose edge is processed by means of a grinding brush of an apparatus according to a further embodiment of the present invention, 
       FIG. 6 . a semi-schematic partial sectional view through a portion of the planetary grinding head containing the axis and a grinding brush according to a further embodiment of the invention and 
       FIG. 7 . a partially schematic plan view of the portion of the planetary grinding head shown in  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a plan view of an apparatus  10  for the processing of substantially planar workpieces and particularly of metal sheet plates. The apparatus  10  contains a conveyor belt  12 , which conveys a sheet steel plate  14  lying thereon in a horizontal transport plane. The feed direction of the sheet steel plate  14  is indicated by an arrow  16 . 
   The apparatus  10  includes four similar planetary grinding heads  18   a,    18   b,    18   c  and  18   d,  out of which grinding head  18   d  will be explained in the following by way of example. The grinding head  18   d  contains a planet carrier  20  rotatable around a vertical carrier axis  22 . Within the planet carrier  20  grinding brushes  24  are mounted rotatably around vertical brush axes  26 . The grinding brushes  26  are coupled to planet gears (not shown) which drive them in a known manner at high speeds, while the planet carrier  20  rotates at a comparatively low speed. 
   The planetary grinding heads  18   a  and  18   b  are arranged in a first row extending transversely to the feed direction  16 , while the planetary grinding heads  18   c  and  18   d  are arranged in a second row extending transversely to the feed direction  16  with the first and second rows being offset to each other in such a manner that the planetary grinding head  18   c —when viewed in the feed direction  16 —closes the gap between the planetary grinding heads  18   a  and  18   b  resp. the planetary grinding head  18   b  closes the gap between the planetary grinding heads  18   c  and  18   d.  This arrangement allows uniform processing of the sheet steel plate  14  over its entire width. 
     FIG. 2  shows a side view of the apparatus  10  of  FIG. 1 . In this Figure, the right lateral edge of the sheet steel plate  14  when viewed in the feed direction  16  (i.e. the lower lateral edge as shown in  FIG. 1 ) is depicted. Moreover, in  FIG. 2  the planetary grinding head  18   d  and the planetary grinding head  18   b,  which is partially concealed by the former, are shown. 
   As can be seen in  FIG. 2 , the brushes  24  include brush bodies  30  and bristles  32  attached thereto. In accordance with one embodiment of the invention the brushes  32  in  FIG. 2  are of different lengths and their ends therefore are spaced at different distances to the transport plane indicated by means of dashed lines  34  in  FIG. 2 . While the brushes  24  of the grinding head  18   b  shown in  FIGS. 1 and 2  only process the surface of the sheet steel plate  14 , the brushes  24  of the grinding head  18   d  also process the lateral edge  28 . 
   In the following, the processing of the lateral edge  28  by means of a known apparatus and by means of various embodiments of the invention, respectively, will be described with reference to  FIGS. 3 to 6 . In  FIG. 3  a schematic sectional view of a known grinding brush  36  including a brush body  37  and bristles  38  is shown. As depicted schematically in  FIG. 3 , the brush  36  is a pot brush in which the ends of the bristles  38  are spaced at a uniform distance to the transport plane  34 . When the brush  36  is rotated around its brush axis  26  as shown in  FIG. 3 , the bristles  38  are bent outwards due to centrifugal forces and thus make contact with the lateral edge  18  of the sheet steel plate  14  over its entire width (i.e. over the entire thickness of the sheet steel plate  14 ). To achieve this, however, the bristles  38  have to be relatively soft, which impairs their machining qualities. 
     FIG. 4  shows a sectional view which is basically identical to the one shown in  FIG. 3 , except for the fact that in  FIG. 4  use is made of the grinding brush  24  with bristles  32  of varying lengths already depicted in  FIG. 2 . The bristles  32  of the grinding brush  24  are markedly harder than the bristles  38  of the known grinding brush shown in  FIG. 3  and thus, due to their low flexibility, each bristle can only process a certain portion of the lateral edge  28  depending on the distance between the end of said bristle and the transport plane  34 . However, since the bristles  32  are of varying lengths and their ends are thus spaced at various distances to the transport plane  34 , all or lateral edge  18  is processed over the entire thickness of the sheet steel plate  14 . 
   Similarly to  FIGS. 3 and 4 ,  FIG. 5  shows an arrangement for a grinding brush  40  according to an alternative embodiment of the invention. In the case of the grinding brush  40  the bristles  42  are all of uniform length. However the corresponding brush body  44  is tilted with respect to the transport plane  34 , while the brush axis  26  remains vertical. Thus, despite their uniform length, the ends of the bristles  42  are spaced at different distances to the transport plane  34  and it is possible to process the lateral edge  18  over the entire thickness of the sheet steel plate  14  without using particularly soft bristles  42 . In the arrangement of  FIG. 5  the grinding body  44  performs a tumbling movement when the grinding brush  40  rotates around its axis  26 . 
   The distance between the ends of each bristle and the transport plane  34  remains unchanged during the rotation of the brush both in the case of the grinding brush  24  of  FIG. 4  and in the case of the grinding brush  40  of  FIG. 5 . Since the wear the bristles are subjected to changes depending on their distance from the transport plane, the bristles  32  of the grinding brush  24  and the bristles  42  of the grinding brush  40 , respectively, will wear off unevenly. In the case of the grinding brush  24  of  FIG. 4  the uneven wear is enhanced further by the different lengths of the bristles  32 . 
   In the embodiments shown in  FIGS. 4 and 5  the distances between the ends of the bristles of one single grinding brush and the transport plane  34  differ by up to 1 to 2 cm, i.e. the bristles which are spaced at the greatest distance from the transport plane  34  are spaced to said plane at a distance which is 1 to 2 cm larger than that of the bristles arranged closest to it. Such a distance range allows for the removal of oxide layers from lateral edges of metal sheet plates with a thickness of up to at least 2 cm with the use of the disclosed apparatus while the bristles do not need to be particularly soft. 
   The sectional view of  FIG. 6  shows a planet carrier  20  and a grinding brush  26  which is coupled to a shaft  52 . Together with this shaft  52  the grinding brush  26  is mounted in a nut  54  in such a way that it is freely rotatable, but inhibited from performing an axial sliding movement. On the free end of the shaft  52  protruding from the nut  54  a pinion gear  56  is mounted in a torque proof manner, which intermeshes with a sun gear  58  of the planetary drive. 
   On an axial portion of the periphery of the nut  54  a thread is formed by means of which the nut is screwed into a corresponding threaded hole  60  of the planet carrier  20 . On the remaining portion of the periphery of the nut  54  a toothing  62  is formed which is engaged with an adjusting collar  66  mounted on the planet carrier  20  coaxially to the latter and provided with internal teeth  64 . By turning the adjusting collar  66  in the direction of the double arrow  68  of  FIG. 7  the nut  54  can be adjusted within the planet carrier  20  in the direction of the double arrow  70  of  FIG. 6  parallel to the axis of the planet carrier  20 . The adjusting collar  66  can engage the nuts  54  of a plurality of grinding brushes  26  in order to adjust several grinding brushes  26  with respect to the planet carrier  20  at the same time, while other grinding brushes may be arranged on the planet carrier in such a way that they are not adjusted by means of the adjusting collar  66 . This arrangement allows for moving a set of grinding brushes, which e.g. are provided with a special type of bristles, to a distance relatively to the workpiece that differs from that of the remaining grinding brushes mounted on the same planet carrier. 
   REFERENCE CHARACTER LIST 
   
       
         10 —apparatus for processing planar workpieces 
         12 —conveyor belt 
         14 —sheet steel plate 
         16 —feed direction 
         18   a —planetary grinding head 
         18   b —planetary grinding head 
         18   c —planetary grinding head 
         18   d —planetary grinding head 
         20 —planet carrier 
         22 —carrier axis 
         24 —grinding brush 
         26 —brush axis 
         28 —lateral edge 
         30 —brush body 
         32 —bristles 
         34 —transport plane 
         36 —grinding brush 
         37 —brush body 
         38 —bristles 
         40 —grinding brush 
         42 —bristles 
         44 —brush body 
         46 —grinding brush 
         48 —bristles 
         50 —brush body 
         52 —shaft 
         54 —nut 
         56 —pinion 
         58 —sun gear 
         60 —threaded bore 
         62 —toothing 
         64 —internal teeth 
         66 —adjusting collar 
         68 —double arrow 
         70 —double arrow