Injection molding machine having a precision clamping unit

An injection molding machine having bed means on which is disposed an apparatus for moving together and separating first and second injection mold pieces, said first and second injection mold pieces having a mutually central axis along which said moving together and separating first and second injection mold pieces occurs, said central axis passing substantially through a central portion of said first and second injection mold pieces, said apparatus comprising:

• first and second guide rail means, disposed on said bed means, said first and second guide rail means movably supporting at least one of said first and second injection mold pieces, each said guide rail means defining its longitudinal axis;
• said longitudinal axis of said first guide rail means being disposed generally parallel to said longitudinal axis of said second guide rail means;
• first and second ball spindle drives mechanically connected to said at least one of said first and second injection mold pieces for moving said at least one of said first and second injection mold pieces toward and away form the other of said first and second injection mold pieces;
• said at least movable one of said first and second injection mold pieces being supported by said first and second guide rail means;
• said first and second guide rail means being firmly attached to said bed means a substantial distance form one anther to provide linear guidance and torsion resistance for said at least movable one of said first and second injection mold pieces;
• said first and said second ball spindle drives for being disposed a distance from one another, one on either side and symmetrically with respect to said central axis of said fist and second injection mold pieces, said first and second ball spindle drives being substantially parallel to said central axis, said first and second ball spindle drives defining a horizontal plane;
• means for operating said first and second ball spindle drives synchronously with one other;
• cradle means for movably supporting said first injection mold piece on said first and second guide rail means, said cradle means comprising a generally U-shaped cradle element having an interior cavity, the interior cavity for being disposed about said guide rail means;
• and
• said first ball spindle drive being positioned generally vertically above said first guide rail means and said second ball spindle drive being positioned generally vertically above said second guide rail means so that the distance form said first guide rail means to said second guide rail means is substantially equal to the distance from said first ball spindle drive to said second ball spindle drive.