A lathe having a guided movable cutter for surfacing contact lenses, comprising:
- base means;
- a motor secured to said base means;
- collet means driven by said motor and adapted to releasably retain a cylindrical lens blank for rotation therewith;
- a first stage supported on said base means for movement thereon parallel to the axis of rotation of said collet means
- a second stage mounted to said first stage for movement thereon perpendicular to the axis of rotation of said collet means;
- a cutting tool mounted to said second stage;
- radius-generating drive means comprising,
- first and second coaxial drive wheels mounted to said base for rotation in concert thereon;
- first and second idler wheels adjacent to and substantially coplanar with said first and second drive wheels, respectively;
- means for mounting said first and second idler wheels to said base and urging them radially toward said first and second drive wheels, respectively;
- first rod means mounted to said base means for reciprocating axial movement, passing between said first drive wheel and said first idler wheel and held therebetween by said first idler wheel;
- second rod means mounted to said base means essentially parallel to the axis of said lens blank for reciprocating axial movement, passing between said second drive wheel and said second idler wheel and held therebetween by said second idler wheel, and engaging said first stage in driving relationship;
- first substantially nonextensible and noncompressible band means passing between said first rod means and said first drive wheel and connected at one end to said first rod means and at the other end to the periphery of said first drive wheel, such that slippage between said first rod means and said first drive wheel is eliminated and the axial movement of said first rod means is transformed into corresponding rotational movement of said first drive wheel;
- second substantially nonextensible and noncompressible band means passing between said second rod means and said second drive wheel and connected at one end to said second rod means and at the other end to the periphery of said second drive wheel such that slippage between said second drive wheel and said second rod means is eliminated and the rotational movement of said second drive wheel is transformed into corresponding axial movement of said second rod means;
- means for imparting a desired pattern of axial motion to said first rod means;
- whereby said axial motion of said first rod means is accurately transferred through said first drive wheel, said first and second band means, said second drive wheel and said second rod means, to said first stage, effectively driving said first stage axially with respect to said lens blank;
- cross-feed drive means comprising,
- third and fourth coaxial drive wheels mounted to said base for rotation in concert thereon;
- third and fourth idler wheels adjacent to and substantially coplanar with said third and fourth drive wheels, respectively;
- means for mounting said third and fourth idler wheels to said base and urging them radially toward said third and fourth drive wheels, respectively;
- third rod means mounted to said base means for reciprocating axial movement, passing between said third drive wheel and said third idler wheel and held therebetween by said third idler wheel;
- fourth rod means mounted to said base means essentially perpendicular to the axis of said lens blank for reciprocating axial movement, passing between said fourth drive wheel and said fourth idler wheel and held therebetween by said fourth idler wheel, and engaging said second stage in driving relationship;
- third substantially nonextensible and noncompressible band means passing between said third rod means and said third drive wheel and at the other end to the periphery of said third drive wheel, such that slippage between said third rod means and said third drive wheel is eliminated and the axial movement of said third rod means is transformed into corresponding rotational movement of said third drive wheel;
- fourth substantially nonextensible and noncompressible band means passing between said fourth rod means and said fourth drive wheel and connected at one end to said fourth rod means and at the other end to the periphery of said fourth drive wheel such that slippage between said fourth drive wheel and said fourth rod means is eliminated and the rotational movement of said fourth drive wheel is transformed into corresponding axial movement of said fourth rod means;
- means for imparting a desired pattern of axial motion to said third rod means;
- whereby said axial motion of said third rod means is accurately transferred through said third drive wheel, said third and fourth band means, said fourth drive wheel and said fourth rod means, to said third stage, effectively driving said second stage axially with respect to said lens blank and
- motor means associated with, and effectively synchronously driving said radius-generating drive means and said cross-feed drive means.