Method and apparatus for manufacturing contact lenses
Apparatus and methods are described for manufacturing contact lenses employing dissolvable mold structure. The apparatus and methods involve approaches to dissolve at least portions of a mold and to separate a lens from the mold to present the lens for collection.
1. A method of forming a contact lens, the method comprising:
providing a polymerizable contact lens precursor material in a cavity defined by at least one cavity-defining portion of at least one mold member, the at least one cavity-defining portion comprising a material that is soluble in a solvent in which the contact lens is not soluble;
polymerizing the polymerizable contact lens precursor material to form an unhydrated contact lens in the cavity; and
holding a support portion of the at least one mold member whilst immersing the at least one cavity-defining portion in the solvent to dissolve at least part of the material that is soluble of the at least one cavity-defining portion, so that the contact lens is released from the cavity;
wherein more of the polymerizable contact lens precursor material is provided to the cavity than is required to fill the cavity, so that there is an excess of the polymerizable contact lens precursor material;
wherein,
the excess of the polymerizable contact lens precursor material passes into a channel defined by at least one cavity-defining portion of at least one mold member; and
a portion of the excess of the polymerizable contact lens precursor material passes from said channel into a channel defined by the support portion of the at least one mold member, so that, after the polymerizable contact lens precursor material is polymerized and the material that is soluble of the at least one cavity-defining portion is dissolved, the excess polymerizable contact lens precursor material forms a solid that is retained by the support portion.
2. A method as claimed in claim 1 , in which the retention of the excess polymerizable contact lens precursor material by the support portion is assisted by gripping the at least one mold member at the channel defined by the support portion.
3. A method as claimed in claim 1 , in which the at least one cavity-defining portion is dissolved in two or more stages.
4. A method as claimed in claim 3 , in which, in an earlier stage, a lower part of the at least one cavity-defining portion is immersed in the solvent and an upper part of the at least one cavity-defining portion is not immersed in the solvent and, in a later stage, the upper part of the at least one cavity-defining portion is immersed in the solvent.
5. A method as claimed in claim 1 , wherein ultrasound is used to speed up dissolution of the at least one mold member.
6. A method as claimed in claim 5 , in which the ultrasound is reduced in power during the dissolution.
7. A method as claimed in claim 1 , in which the at least one mold member is moved in the solvent continuously during dissolution.
8. A method as claimed in claim 1 , wherein the at least one mold member comprises a plurality of molds that are mounted on a moving support.
9. A method as claimed in claim 1 , in which, during dissolution, the at least one mold member is inside a guide tube.
10. A method as claimed in claim 9 , wherein the guide tube is made from an acoustically transparent material.
11. A method as claimed in claim 1 , in which the solid formed by the solid that is retained by the at least one support portion is in a single piece.