Patent Publication Number: US-7220171-B1

Title: Cutting cup for sphere making machines

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an improved cutting cup for sphere making machines. 
   It is known in the lapidary art to make spheres of rock and similar materials using a sphere making machine. In making rock spheres, the piece of rock is first cut into a perfect cube. The corners of the cube are then cut off, and then the resulting corners cut off again for a total of 32 cuts. The resulting rough sphere is ground so it is fairly rounded, and then placed into a sphere making machine. Machines for making such spheres have either two or three concave grinding cups that are rotated by spindles to grind against the surface of the rock to create a sphere. The interior of the concave grinding cups typically contains a coating of an abrasive, such as 40/50 mesh diamonds sintered to a cup made of cast iron. 
   Such sphere making machines are commercially available. A two head “little sphere” machine is available as Covington Model 382, and a two head “large sphere” machine is available as Covington Model 381. A three head sphere machine is available as Covington Model 383. 
   With the conventional grinding cups currently commercially available it typically takes 4–6 hours to form a rock sphere. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a cutting cup for sphere making machines that greatly reduces the time required to form a sphere. 
   The cutting cup includes a cylindrical ring having an outer wall, an inner wall, a bottom wall, and a top wall, the top wall having at least one beveled facet. A cutting element is attached to each of the beveled facets. Each of the cutting elements have a cutting edge adapted to at least partially contact a workpiece to be formed into a sphere. A mounting member is attached to the bottom wall of the cylindrical ring for attaching the cutting cup to the spindle of a sphere making machine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top plan view of the sphere making cutting cup of the present invention; 
       FIG. 2  is a side elevational view of the cutting cup; 
       FIG. 3  is a bottom plan view of the cutting cup; 
       FIG. 4  is a top plan view of the ring subassembly of the cutting cup, shown without the cutting elements in place; 
       FIG. 5  is a cross-sectional view of the ring subassembly taken along line  5 — 5  of  FIG. 4 ; 
       FIG. 6A  is a top plan view of a cutting element; 
       FIG. 6B  is a front elevational view of a cutting element; 
       FIG. 7  is a top plan view showing the relationship of the cutting elements to the plane of the rock sphere being machined; 
       FIG. 8  is a cross-sectional view taken along line  8 — 8  of  FIG. 7 ; and 
       FIG. 9  is a top plan view of a second embodiment of the cutting cup. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   The sphere making cutting cup  10  of the present invention includes a cylindrical ring  20 , a plurality of identical cutting elements  30 , and a mounting member  40  for attaching the cup  10  to the spindle of a sphere making machine. 
   Cylindrical ring  20  is preferably made of mild steel which is powder coated. As best seen in  FIGS. 4 and 5 , cylindrical ring  20  has an outer wall  22 , an inner wall  23 , a bottom wall  24 , and a top wall formed of a plurality of evenly spaced apart beveled facets  25  adapted to receive cutting elements  30 . The beveled facets  25  have an angle sloping downwardly from said outer wall  22  to said inner wall  23 . Evenly spaced apart raised triangular stops  26  separate adjacent beveled facets  25 , and are adapted to abut the ends of adjacent cutting elements  30 , as best seen in  FIG. 1 . 
   Each cutting element  30  is substantially rectangular in cross-section. As best seen in  FIGS. 6A and 6B , each cutting element  30  has a front wall  31 , a rear wall  32 , a top  33 , a bottom  34  and ends  35 . Front and rear walls  31 ,  32  are arcuate and substantially parallel to each other. Front wall  31  is concave and rear wall  32  is convex. The intersection of front wall  31  and top  33  forms a cutting edge  36 . 
   Cutting element  30  is preferably made of a hardened metal alloy containing 40/60 grit diamonds substantially uniformly dispersed throughout. A suitable alloy is one made of silica, nickel and copper. Such a composition has a much longer cutting life than would a cutting element merely coated with an abrasive material. 
   Cutting elements  30  are soldered onto beveled facets  25 . The angle of the beveled facet  25  to the horizontal is such as to cause cutting edge  36  of cutting element  30  to contact the rock workpiece to provide a cutting action. The angle depends on the diameter of the cup  10 . For a cup  10  having a diameter of about 7 cm., an angle of about 40 degrees is satisfactory. 
   The number of cutting elements  30  depends on the diameter of cup  10 . For a cup  10  having a diameter of about 7 cm., five cutting elements are preferred, as shown in the drawings. 
   Sphere making machine mounting member  40  is circular and has the same diameter as ring  20 . A hollow cylindrical collar  42  extends downwardly from member  40  in the center thereof. A circular opening  44  extends through the mounting member  40  and collar  42  along the longitudinal axis thereof. The walls of member  40  and collar  42  adjacent circular opening  44  are threaded and adapted to be threaded onto the spindles of a sphere making machine. Mounting member  40  is preferably made of an injection molded plastic, such as ABS. 
   Mounting member  40  is attached to ring  20  by any suitable means, such as threaded fasteners  46 . 
     FIGS. 7 and 8  show the relationship of cutting elements  30  and a sphere  50  being formed in a sphere making machine. The concave inner walls  31  of cutting elements  30  face sphere  50 . Initially only a central portion of the cutting edges  36  of cutting elements  30  abuts the surface of sphere  50  at the intersection of plane “P” with the surface of sphere  50 . As the cutting edges  36  of cutting elements  30  are worn down by use, more of the cutting edges  36  come into contact with sphere  50 , thus prolonging the life of the cutting elements  30 . Cutting edges  36  of cutting elements  30  act like the cutting tool used with a workpiece turned by a lathe rather than acting as a grinder as in the prior art grinding cups used with sphere making machines. 
   When the useful life of the cutting elements  30  has expired, they can be removed from ring  20  and replaced. 
   Although the segmented cutting elements  30  are preferred, a non-segmented ring-shaped cutting element  130  can be mounted on cutting cup  110 . Such a non-segmented cutting element  130  is shown in  FIG. 9  mounted onto a cylindrical ring (not shown) that is identical to cylindrical ring  20  except that the top wall thereof is not beveled. The top wall of cutting element  130  is beveled, having an angle sloping downwardly from the outer wall to the inner wall of the cutting element  130 . The cylindrical ring of cutting cup  110  is mounted on a sphere making machine mounting member  140  having a circular opening  144 . Mounting member  140  is identical to mounting member  40   
   While the cutting cups  10  and  110  have been described as being used in a sphere making machine for making rock spheres, they can be used to form spheres from any material, such as metal, plastic, etc. 
   It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments of this invention without departing from the underlying principles thereof. The scope of the present invention should, therefore, be determined only by the following claims.