Abstract:
An apparatus for polishing the edges and sides of granite and other stones includes a hollow rectangular base for sliding along a stone surface, a yoke mounted on the base, a disc polisher pivotally mounted in the yoke for rotation around a horizontal axis between a variety of polishing orientations, and an indexing mechanism for releasably locking the polisher in such orientations.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to an apparatus for polishing stone, and in particular to a manually operated apparatus for polishing the sides and edges of sheets of granite and other stones. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    In general, the edges and sides of granite and other stones are polished using portable disc grinders or polishers such as those sold under the Makita trademark. In order to do a good job with such devices, a great deal of time and experience is required. Another problem with the portable devices is that the power cord is usually located on the floor behind the operator where cooling water accumulates, increasing the likelihood of electrical shock and the possibility of tripping on the cord. 
         [0003]    In the hands of an inexperienced or unskilled operator, the use of such devices often results in uneven bevelled edges. Even with an experienced tool user, holding the grinder or polisher at a certain angle for a lengthy period of time can result in muscle strain. In any event, the task of bevelling edges evenly is difficult. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    The present invention provides an apparatus for polishing stone which is relatively simple and easy to manipulate, thereby preventing operator fatigue. One embodiment of the invention includes rollers for making it easy to produce an evenly polished edge on a workpiece even for an inexperienced operator. The use of a mechanism for adjusting the grinding or polishing angle relative to the workpiece facilitates the production of a smooth and even bevelled edges and sides of a workpiece. 
         [0005]    In its simplest form, the polishing apparatus includes a base having a straight front end for sliding along the top surface of a workpiece; a handle extending outwardly from a front end of said base for manipulating the apparatus on the workpiece; a yoke on said base; a grinder pivotally mounted in the yoke for rotation around a horizontal axis parallel to the straight front end of the base; a head on said grinder extending outwardly beyond the straight front edge of the base; a grinding pad connected to a spindle extending out of said head for polishing a workpiece; and an indexing mechanism for releasably locking the grinder in one of a non-use position above the base and a plurality of use positions in which the grinding pad is perpendicular to the top surface of the workpiece for polishing a side of the workpiece or at an angle to the vertical for producing a bevelled edge on the workpiece. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The polishing apparatus is described in greater detail below with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention, and wherein: 
           [0007]      FIGS. 1 and 2  are isometric views of a polishing apparatus in accordance with the invention; 
           [0008]      FIG. 3  is an exploded, isometric view of the polishing apparatus of  FIG. 1 ; 
           [0009]      FIG. 4  is a cross-section of a portion of the front end of the polishing apparatus of  FIGS. 1 to 3  with parts omitted; 
           [0010]      FIG. 5  is an exploded, isometric view of a polisher and bracket assembly used in the apparatus of  FIGS. 1 to 3 ; 
           [0011]      FIG. 6  is an isometric view of a second embodiment of the polishing apparatus; 
           [0012]      FIG. 7  is an exploded, isometric view of the apparatus of  FIG. 6 ; and 
           [0013]      FIG. 8  is a cross-section of a portion of the front end of the apparatus of  FIGS. 6 and 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    With reference to  FIGS. 1 to 3 , the polishing apparatus includes a hollow, rectangular, steel base indicated generally at  1  for sliding along the surface of a solid workpiece  2  ( FIGS. 1 ,  2  and  5 ) proximate one side  3  thereof. The base  1  includes a top wall  4 , a bottom wall  5 , a front wall  6 , a rear wall (not shown) and side walls  8  (one shown). The base  1  acts as a reservoir for receiving water from a hose (not shown). The hose is releasably connected to the base  1  by an off-the-shelf quick connect  9  which is mounted on the top wall  4  of the base  1  above an inlet opening  10  ( FIG. 3 ). Water is discharged from the base  1  via a plurality of small holes  11  in the bottom wall  5  of the base  1 . As described hereinafter, in greater detail, stop plate  13  is secured in a shallow recess  14  in the front of the base  1  by screws  15  for limiting tilting of a disc polisher or grinder  16  relative to the base  1 . A rectangular, plastic pad  17  can be connected to the bottom wall  5  of the base  1  for ensuring smooth sliding of the assembly on the workpiece  2 . 
         [0015]    A pair of handles  18  extend into two rectangular bars  19  on the side walls  8  of the base  1  for maneuvering the apparatus on the workpiece  2 . The handles  18  can be generally J-shaped as shown in the drawings or straight. Moreover, both handles  18  can be replaced by a single, generally C-shaped handle (not shown) with the free ends of the handle extending into the bars  19 . The bars  19  are slidable on the side walls  8  of the base  1 . Each bar  19  is fixed in one position by a bolt  22  on one end of a handle  23 . The bolt  22  extends through a washer  24  and a longitudinally extending slot  25  in the bar  19  into a threaded hole  27  in the side wall  8  of the base  1 . When the bolts  22  are loosened, the bars  19  with the handles  18  can be moved forwardly or rearwardly relative to the base  1  to effectively make the handles longer or shorter. 
         [0016]    As best shown in  FIG. 4 , one arm  29  of each handle  18  extends through a roller support  30  into a blind hole  31  in the front end of the bar  19 . The front end of a handle receiving socket  33  in the roller support  30  is larger in diameter than the handle  18 . A helical spring  34  around the handle  18  is sandwiched between the inner end  35  of the socket  33  and a ring  36  connected to the handle by a set screw  37 . The handle  18  is held in the roller support  30  by a circlip  38  mounted in the outer end of the socket  33 . 
         [0017]    With the spring  34  in the relaxed condition shown in  FIG. 4 , there is a gap  40  between the inner end of the handle  18  and the inner end of the blind hole  31 . Thus, the handle  18  can be pushed toward the bar  19  to compress the spring  34  and press a roller  41  against the workpiece  2 . The roller  41  is suspended from a ledge  42  extending outwardly from the bottom end of the support  30  by a nut  43  connected to the threaded top end  45  of the shaft  46  of the roller. Screws  47  in the sides of the bars  19  are used to lock the handles  18  in fixed positions. 
         [0018]    A disc polisher or grinder assembly indicated generally at  48  is pivotally mounted in a yoke defined by a pair of parallel, spaced apart plates  49  connected to the base  1  by screws  50 . The plates  49  are generally L-shaped, including ends  51  extending outwardly beyond the front wall  6  of the base  1 . The polishing assembly  48  is held in a fixed position by an off-the-shelf spring loaded index pin  52  extending through one plate  49  into one of three holes  53 ,  54  or  55  arranged in an arcuate row in a generally triangular indexing plate  57  on one side of the polishing assembly  48 . 
         [0019]    As best shown in  FIG. 5 , as well as the polisher  16 , and the indexing plate  57 , the polishing assembly  48  includes a generally U-shaped baseplate  58 . The indexing plate  57  is mounted on one side  59  of the baseplate  58  using screws  60 . The polishing assembly  48  is pivotally mounted in the yoke by a bolt  62  extending through aligned holes  64  in the plates  49  and a hole  65  near the bottom corner of the indexing plate  57 , washers  66  and a nut  67 . The polisher  16  is mounted on the rear end of the baseplate  58  by means of a two-piece bracket  69 , which includes an inverted U-shaped top piece  70  and a U-shaped bottom piece  71  interconnected by screws  72 . A notch  73  in the bight  74  of the bottom piece  71  receives one end  75  of a tube  76  which is connected to the polisher  16  for feeding water from the base  1  to the polisher  16 . A coupler  78  connects the other end  79  of the tube  76  to an outlet hole  80  ( FIG. 3 ) in the top wall  4  of the base  1 , whereby some of the water entering the base  1  is fed to the polisher  16 . 
         [0020]    The spindle  82  in the head  83  of the polisher  16  extends through a bearing  84  in a countersunk hole  85  in the other end  86  of the baseplate  58 . A circlip  87  holds the bearing  84  in the hole  85 . A second bearing  89  is mounted in the bottom of the baseplate  58 . A tubular shaft extension  90  is connected to the grinder spindle  82  and extends downwardly through the bearings  84  and  89 . A rubber pad  92  is connected to the bottom end  93  of the extension  90  using a threaded nozzle  95 . During grinder operation, water from the base  1  is fed through the tube  76  to the polisher head. The water enters the spindle  82  and passes downwardly through the extension  90  and the nozzle  95  to the workpiece  2 . A polishing disc  96  is mounted on the bottom of the pad  92  using a hook and loop connection (not shown) of the type employed on off-the-shelf disc polishers, i.e. VELCRO7 hooks are provided on the bottom of the pad  92  for mating with loops  97  on the top of the disc  96  or vise versa. 
         [0021]    Referring again to  FIGS. 1 to 3 , with the index pin  52  in the hole  53  in the indexing plate  57  the polisher  16  is located in a slightly tilted, non-use position (not shown) above the base  1 . In the non-use condition of the assembly, the bars  19  extend beyond the rear end of the base  1  (see  FIG. 2 ). In these positions of the polisher  16  and the bars  19 , the center of gravity of the assembly is rearward of the front of the base  1 , making carrying of the assembly less awkward. In order to polish a top edge  99  ( FIG. 1 ) of the workpiece  2 , the bars  19  are moved forward to the positions shown in  FIG. 1 . By pulling the index pin  52  outwardly, the polisher assembly  48  can be rotated around the longitudinal axis of the bolt  62 . During rotation, the index pin  52  is released and ends up in the hole  54 , locking the polisher assembly  48  in the position shown in  FIG. 1  for polishing the top edge  99  of the workpiece  2 . The handles  18  are pushed towards the workpiece  2  to bias the rollers  41  against the workpiece  2 , causing the disc  96  to engage the workpiece  2 . The assembly is moved along the side of the workpiece  2  to polish the top edge  99 . When the handles  18  are released the springs  34  push the handles  18  and the rollers  41  away from the workpiece  2 . 
         [0022]    In order to polish the side  3  of the workpiece  2 , the bars  19  are moved rearwardly to the positions shown in  FIG. 2 , the index pin  52  is retracted and the polisher assembly  48  is rotated to the position shown in  FIGS. 2 and 4  which causes the pin to enter the hole  55  in the indexing plate  57 . The polisher assembly is prevented from going beyond the vertical position shown in  FIG. 2  by the stop plate  13  ( FIG. 3 ). The handles  18  are pushed inwardly and the assembly is moved along the side of the workpiece  2  as described above. 
         [0023]    A second embodiment of the invention is illustrated in  FIGS. 6 to 8 , in which the same reference numbers are used to identify the elements the same or similar to those in  FIGS. 1 to 5 . 
         [0024]    In the second embodiment of the invention, a second indexing plate  101  is connected to a second side  102  of the base plate  58  using screws  60  ( FIG. 8 ). The bolt  62  ( FIG. 3 ), the washers  66  and the nut  67  are replaced by a pair of bolts  104  and  105 , washers  106  and nuts  107 . The bolts  104  and  105  extend through the sides  49  of the yoke and the indexing plates  57  and  101  for pivotally mounting the grinder assembly  48  in the yoke. 
         [0025]    Referring to  FIGS. 6 and 7 , the bolt  105  has a reduced diameter outer end  109  for insertion between the arms  110  of the bifurcated end  111  ( FIG. 8 ) of a cam lever  112 . The arms  110  are generally circular and include off-centered holes  114  for receiving a small shaft  115 . The reduced diameter outer end  109  of the bolt  105  is inserted into a diametrically extending hole  117  in the shaft  115 , and a pin  118  is inserted through a radially extending hole  119  at 90° to the hole  117  into a diametrically extending hole  120  in the end  109  of the bolt  105 . The arms  110  at the end  111  of the lever straddle a pair of ears  121  on a pivot plate  122  sandwiched between the lever end  111  and the washer  106 . 
         [0026]    The end  111  of the lever  112  acts as a cam. In the position shown in  FIG. 8 , the lever  112  exerts pressure on the plate  122  and the washer  106 , drawing the nut  107  tight against the indexing plate  101  to prevent rotation of the latter and consequently rotation of the polishing assembly  48 . When the lever  112  is rotated by 90° to a position in which it is more or less aligned with the bolt  105 , the indexing plate  101  is released and consequently, when the index pin  52  is retracted, the polisher assembly  48  is free to rotate to any of a plurality of use positions. Thus, the angle of the beveled edge on the workpiece can be virtually infinitely varied. Once the desired tilt of the polishing assembly  48  has been achieved, the lever  112  is again rotated to the position shown in  FIG. 8 .