Lens generating tool for generating a lens

#This invention is related to a solid polycrystalline diamond cutting tool, and a method for generating a prescription surface in a plastic lens used in spectacles, and more particularly to a method for generating a surface in a plastic lens blank that eliminates the finishing step required after the conventional lens grinding step.

#Plastic lens blanks are conventionally formed in an injection molding process, either of a polycarbonate or a plastic material commonly known as CR-39. Polycarbonate is much tougher than CR-39 and is used where safety is a factor in material selection.

#U.S. Pat. No. 3,685,210 which issued Aug. 22, 1972 to Gilbert John Bowen shows a prior art method for generating a surface on a lens.

#The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:

#FIG. 1 is a view of a tool having a spindle and a pair of solid crystalline diamond inserts illustrating the preferred embodiment of the invention;

#FIG. 2 is an enlarged view of one of the cutting tool inserts;

#Referring to the drawings, a preferred tool 10 is illustrated in FIG. 1, supporting a pair of identically- shaped cutting elements 12 and 14 for rotation about tool spindle axis 16. The tool is mounted in a conventional lens generating machine having rotary power means 22. Rotary power means 22 rotates the tool in the manner well known to those skilled in the art of lens generating.

#A commercially-available CR-39 lens blank 24, is releasably connected to block 26, and mounted in holder 27, in a stationary position, with respect to the tool.

#Cutting elements 12 and 14 are adapted to generate a prescription-defined, curved surface 28 on the back side of the lens blank.