Method for manufacturing ophthalmic lenses using circular blanks
View Patent ↗For manufacturing ophthalmic lenses and other optical form bodies made of plastic material, plastic form parts are used which are made by non-cutting shaping and are then further worked by mechanical production steps. Said plastic form parts are circular blanks ( 1 ) made of two different plastic materials which are firmly joined to each other. Thereby, an interior lens element ( 2 ) that consists of a high-quality material is concentrically surrounded by a ring fixture ( 3 ) which consists of a low priced material. Either surface of the lens element ( 2 ) may feature any given geometry. During mechanical working, the ring fixture ( 3 ) is used for mounting as well as for depositing and, in addition, for stabilizing the workpiece ( 9 ). For this reason it is partially maintained throughout the mechanical working and is cut off at the end only.
1. A method for manufacturing a spectacle lens made of plastic material wherein the method comprises the steps of:
providing a plastic circular blank made by non-cutting shaping procedures, the plastic circular blank comprising:
an interior lens element comprised of a plastic material suitable for the manufacture of a spectacle lens, the interior lens element being substantially of a size and shape suitable for the manufacture of a spectacle lens, the interior lens element having two surfaces being of an arbitrary geometry, and
a ring fixture comprised of a plastic material different than the plastic material comprising the interior lens element, the ring fixture concentrically surrounding the interior lens element, the ring fixture being fixedly attached to the interior lens element;
mechanically working the plastic circular blank by mechanical production steps using cutting procedures selected from the group consisting of milling, lathing, grinding, polishing, and engraving, wherein during the mechanically working step, the ring fixture is available for mounting, depositing and stabilizing the plastic circular blank, the ring fixture being partially maintained during the mechanical production steps; and
cutting off the entire ring fixture so as to remove all plastic material outside the periphery of said interior lens element to form a lens suitable in size and shape for use as a spectacle lens.
2. The method for manufacturing according to claim 1 , wherein during non-cutting shaping, the lens element is made to obtain the same dimensions and geometries as obtained from plastic form parts by conventional blocking-on procedures, a desired enlargement of the diameter of the plastic circular blank being produced by the ring fixture put around the interior lens element.
3. The method for manufacturing according to claim 1 , wherein the ring fixture is cast or injected around the interior lens element.
4. The method for manufacturing according to claim 1 , wherein the ring fixture is adhered or is made using liquid plastic which is hardened by a hardener or by ultraviolet light.
5. The method for manufacturing according to claim 1 , wherein the ring fixture is made of thermoplastic plastic which is heated for processing and is injected around the interior lens element.
6. The method for manufacturing according to claim 1 , wherein the ring fixture is manufactured as a separate component by casting, by injection molding or by cutting-off from a hollow cylinder and is joined to the interior lens element afterwards.
7. The method for manufacturing according to claim 6 , wherein adhesive means are used for joining the interior lens element and the ring fixture.
8. The method for manufacturing according to claim 6 , wherein welding by a laser or by ultrasound means is used for joining the interior lens element and the ring fixture.
9. The method for manufacturing according to claim 1 , further comprising reducing a thickness of the spectacle lens.
10. The method for manufacturing according to claim 1 , wherein by means of mechanical working out of the ring fixture, a basic part of an annular region is formed which in the following mechanical production steps is maintained and which serves for mounting, depositing and stabilizing the plastic circular blank, the annular region consisting mainly of the material comprising the ring fixture.
11. The method for manufacturing according to claim 1 , wherein two plane faces are produced as the surfaces of the interior lens element.
12. The method for manufacturing according to claim 1 , wherein through use of non-cutting shaping procedures, the interior lens element is given a plane face and a pre-shaped face formed to be a concave surface or a convex surface, respectively, which are either roughly pre-shaped or are already shaped.
13. The method for manufacturing according to claim 1 , wherein during manufacturing of the interior lens element by non-cutting shaping, two pre-shaped faces are formed both of which are either roughly pre-shaped or already shaped.
14. The method for manufacturing according to claim 1 , wherein one side of the interior lens element is already provided with a concave or convex surface of optical quality, and the ring fixture protrudes beyond the surface of the interior lens element so as to form a shaped rim which is maintained during the following mechanical production steps and which serves for mounting, depositing and stabilizing the plastic circular blank, the shaped rim consisting of the material comprising the ring fixture.
15. The method for manufacturing according to claim 14 , wherein the shaped rim protrudes from the concave surface of the interior lens element and wherein the concave surface is manufactured by non-cutting shaping so as to be already shaped.
16. The method for manufacturing according to claim 14 , wherein the shaped rim protrudes from the convex surface of the interior lens element and the convex surface is made so as to be already shaped.
17. The method for manufacturing according to claim 1 , wherein following the mechanical working the plastic circular blank is coated and its optical is marked, whereupon the spectacle lens is cut off from the circular blank, the cut being exclusively made within the material of the interior lens element.
18. The method for manufacturing according to claim 1 , wherein a mechanical working tool, a waterjet or a laser is used for cutting the spectacle lens off from the plastic circular blank.
19. The method for manufacturing according to claim 1 , wherein through the cutting of the plastic circular blank, the spectacle lens obtains an outer contour which is sized and shaped to fit into a spectacle lens frame, either exactly or with a machining allowance.
20. The method for manufacturing according to claim 1 , wherein the step of cutting follows the step of mechanically working the plastic circular blank.