Abstract:
An assembly for surface finishing, comprising a pair of heads which are movable on linear slides. Each head comprises a series of cup brushes that finish the surface of the workpiece. The two heads are tied to a single motor/gearbox combination by a crankshaft which allows each head to move with a phase relationship determined by the linkage to counterbalance the motions and acceleration forces against each other. By counterbalancing the heads in this manner, faster oscillation speeds can be achieved without undesirable vibration. The result is a better treatment of the surface of the workpiece.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to provisional application No. 61/002,755 filed Nov. 13, 2007 and provisional application No. 61/102,606 filed Oct. 3, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to assemblies for finishing the surfaces of workpieces that pass through the machinery, such as widebelt wet or dry metal finishing machines for operations such as grinding, deburring, polishing, and the like. 
       BACKGROUND 
       [0003]    The basic features of surface finishing machines for metal are well known. In general, a moving bed carries a workpiece such as a plate of metal beneath a series of assemblies that abrade or polish the upward-facing surface of the workpiece. Typical types of assemblies include belt sanders, brushes, and discs. 
       SUMMARY 
       [0004]    In general terms, this application describes an assembly for surface finishing, comprising a pair of heads which are movable on linear slides. Each head comprises a series of cup brushes that finish the surface of the workpiece. The two heads are tied to a single motor/gearbox combination by a crankshaft which allows each head to be attached such that they are out of phase in their linear motions compared to each other. This counterbalances the motions against each other. By counterbalancing the heads in this manner, faster oscillation speeds can be achieved without undesirable vibration. The result is a better treatment of the surface of the workpiece. 
         [0005]    More specifically, the assembly is for treating a longitudinally moving surface of a metal workpiece. It comprises a vertically adjustable frame and a pair of heads facing each other from opposite sides of the frame. Each head is supported by a rail mounted to the frame for transverse sliding motion on the rail relative to the frame. The assembly further comprises a motor to transversely slide each head. The motor is mounted to the frame and coupled to each of the pair of heads by a transmission. The transmission converts rotation of the motor into reciprocating transverse sliding motion of each head during longitudinal movement of the workpiece. A plurality of independently driven spindle motors is vertically mounted to each head, and a respective plurality of cup brushes is mounted to the spindle motors to address the longitudinally moving surface of the metal workpiece during transverse motion of each head. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]    The figures are schematic and provided for illustration only, and thus do not limit the scope of the invention. In particular, common accessories and components, such a mounting hardware and electrical wiring, has been omitted solely for clarity. 
           [0007]      FIG. 1  is a perspective view of the assembly with some components removed for clarity of illustration. 
           [0008]      FIG. 2  is a side view of the assembly of  FIG. 1 . 
           [0009]      FIG. 3  is a reversed perspective view of the assembly of  FIGS. 1 and 2 . 
           [0010]      FIG. 4  is a perspective view of the motor, gear box, and linkage components. 
           [0011]      FIG. 5  is a reverse perspective view of the linkage components of  FIG. 4 , the motor and gear box being omitted for clarity. 
           [0012]      FIG. 6  is a close-up perspective view of the various linkage components. 
           [0013]      FIG. 7  is a reversed perspective view of selected components of the assembly of  FIGS. 1-3 . 
           [0014]      FIG. 8  is a close-up perspective view of the spindle motor and cup brush components. 
           [0015]      FIG. 9  is a close-up perspective view of the coupling block component. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In the description below, the longitudinal direction is direction of travel of the workpiece having its surface finished, i.e., longitudinal corresponds to “forward” or “reverse” directions of the workpiece. The transverse direction is perpendicular to longitudinal but within the plane of the workpiece, i.e., corresponding to the “width” of the throat of the apparatus into which the workpiece travels. The vertical direction is perpendicular to the plane of the workpiece, i.e., away from or toward the surface being finished. 
         [0017]    Referring to  FIGS. 1-3 , assembly  100  comprises a pair of reciprocating heads  10 , the nearest of which has had its cover  11  removed to expose a series of spindle motors  12  (see also  FIG. 8 ) as attached to the head  10 . Each cup brush  13  is attached by a collet chuck to the drive shaft of its respective spindle motor  12 . On each head, the set of cup brushes  13  abrade the entire width of the upper-facing surface of the workpiece (not shown) as it passes underneath the assembly  100  on a conventional bed, in the form of an endless moving belt (not shown). At the same time, each head  10  is transversely reciprocating by action of the combination of a single drive motor  14  and reduction gear box (see also  FIG. 4 ), which is rotating a single drive shaft  15 , which in turn is connected to each head  10  by a linkage  16  (see also  FIGS. 4-6 ). 
         [0018]    In structural terms, the assembly  100  is attached to a chassis (not shown) by conventional mounts (not shown); a chassis-mounted frame comprises two vertically movable upright columns  16  to which the drive motor  14  and a pair of transverse rails  17  are fixed. Each rail  17  supports a pair of upper and lower edges  18  on which each head  10  glides with the assistance of various guide/support wheels  19  (see also  FIG. 7 ). The unmatched guide/support wheel on the upper edge  18  ensures that head  10  is supported by at least two upper wheels when it is slid fully from the apparatus for replacement of the cup brushes  13 . For this purpose, rail  17  and edges  18  extend beyond column  16 . 
         [0019]    A single vertical frame adjustment mechanism  20  (for example, a worm gear and shaft arrangement) moves the entire frame and everything attached to it at once. This allows for all of the drive motor  14 , the pair of heads  10 , and the linkage  16  between the drive motor  14  and each head  10  to be vertically moved together in a single adjustment, thus maintaining intact the alignment (phase difference) of the heads  10  with respect to each other and the other geometry of the assembly  100  with respect to the workpiece. 
         [0020]    As illustrated in  FIGS. 4-6 , the drive motor  14  is linked to a worm drive so that relatively rapid rotation of the vertically mounted drive motor shaft is converted into relatively slower rotation of the horizontally oriented drive shaft  15 , providing sufficient torque to oscillate the heads  10  despite their large weight. Friction is considerably reduced by the rolling action of each head  10 , using the guide/support wheels  19  along upper/lower edges  18 . As illustrated, the heads  10  are exactly out of phase, such that the two heads  10  reciprocate in opposite directions, automatically balancing the forces on the entire assembly  100  caused by motion of the heads  10 . The phase difference between the two heads  10  is set by the relative positions of the two coupling blocks  21  as angularly placed around the circumference of the drive shaft  15 . 
         [0021]    Each coupling block  21  attaches on one of its ends to the drive shaft  15  and on its other end to a tie rod assembly  22 . Each tie rod assembly  22  comprises an externally threaded rod  23  and a pair of internally threaded end pieces  24 , one end piece  24  on each end of the externally threaded rod  23 . The two end pieces  24  are threaded onto rod  23  as required to span the distance between the drive shaft  15  and head  10 , and jam nuts  25  are used to fix each end piece  24  in place on rod  23 . Each end piece  24  further comprises a non-rotating minor shaft  26 . The minor shaft  26  is attached to either the coupling block  21  or the backplate  27  of each head  10 . As shown in  FIG. 6 , the minor shaft  26  has a rounded end to provide sufficient play in each tie rod assembly  22  to accommodate any minor tolerances that are required to fit the entire linkage in place. 
         [0022]    In the preferred embodiment illustrated, shaft key  28  provides an index location and fixes the relative positions of the two coupling blocks  21  with respect to each other and drive shaft  15 . The shape of shaft key  28  is designed to mate with indexed detents  29  arranged at 90° angles around the drive shaft recess  30  defined by each coupling block  21  (see also  FIG. 9 ). This enables placement of a set of two coupling blocks  21  (each of which can be reversed left-to-right) in any of four positions around drive shaft  15 , i.e., in-phase (both heads  10  moving in unison), out-of-phase (each head  10  moving exactly opposite to the other), and the two positions in between. 
         [0023]    In any embodiment of the invention, the cup brushes are preferably, but not necessarily, identical (particularly in their abrasive characteristics) and spinning in the same direction. It is possible for the cup brushes on the first head encountered by the workpiece to be different from those of the second head. This would permit, for example, the use of relatively course abrasive rating cup brushes followed by relatively fine abrasive rating cup brushes in a single pass of the workpiece. It is not preferred for the abrasive rating of the cup brushes of a single head to vary from one another, however, as this would not provide a finish to the workpiece that did not vary across the transverse width of the workpiece, which is generally not desired. 
         [0024]    Another option is for all cup brushes to be identical but for them to be spinning in any arrangement of directions, such as all of the first head spinning counterclockwise (viewed from either above or below) and all of the second head spinning clockwise (viewed from the same perspective). Another possibility is for the cup brushes on a given head to alternate in rotation direction. Depending on the materials of the workpiece and abrasive on the cup brushes, such options may provide variations in finish quality or finish pattern that are desirable. Such options are easily accommodated by known variations in the wiring and/or phases of the signals provided to drive the spindle motors involved. In the latter regard, it should be noted that the spindle motors are not coupled together in any mechanical sense other than their common mounting within head  10 . That is, there are no gears, belts, or other means of mechanical coupling between adjacent spindle motors to coordinate their operation. Instead, the electrical signal brought to each spindle motor—which, in the preferred embodiment, is simply parallel wiring of a common signal to each spindle motor of a given head—is responsible for driving each motor in a coordinated (preferably identical) manner. 
         [0025]    The number and diameter of cup brushes is related to the working width of the apparatus and the head oscillation travel distance. In the preferred embodiment illustrated here, the head has sixteen cup brushes, each being three and one-half inch diameter, spaced at intervals on the order of three and five-eighths to four inches. Each head travels between two and five inches in the transverse direction, fully finishing a workpiece which is up to about sixty-three inches in transverse width. The cup brushes, as illustrated, are fully in-line and not staggered longitudinally, which would undesirably increase the width of each head and thus the entire apparatus. 
         [0026]    Typical operating parameters include: workpiece feed speeds of three to nine inch/second; cup brush rotation speeds in the range of hundreds to thousands of rpm; head oscillation frequencies in the range of one-quarter to three cycles/second; head oscillation travel distances in the range of three to ten inches; drive motor speeds in the range of one thousand to two thousand rpm (and up to twenty horsepower); and gear box ratios in the range of 5:1 to 100:1. These are preferred ranges only. 
         [0027]    Optional pinch rollers (not shown) are preferred to hold the workpiece in place against the drive bed for improved performance. The advantage of the use of dual heads is that a central pinch roller may be placed between the two heads, in addition to pinch rollers on both inlet and outlet sides of the assembly as a whole. Similarly, there is also room underneath each head, on opposite sides of the central pinch roller, for stationary manifolds to deliver cooling liquid to the surface of the workpiece as it is being treated.