Mandrel for holding a lens blank and method of making a lens using the same
A mandrel for holding and positioning an intraocular lens blank during manufacturing includes a shank portion having a central axis and a lens blank holding section configured to hold the lens blank. The holding section includes a central cavity formed concentrically with the central axis of the mandrel. Projections are formed on a surface of the central cavity and are configured to support a first surface of the lens blank at a fixed distance from the surface of the central cavity. A ring fits within a peripheral portion of the central cavity to hold a second opposing surface of the lens blank. A method for making an intraocular lens using the mandrel includes filling the space formed under the first surface of the lens with a liquid, such as water, freezing the liquid, and then machining and/or milling the second surface of the lens blank.
1. A mandrel assembly for holding an intraocular lens blank, the mandrel assembly comprising:
a mandrel comprising:
a shank portion having a central axis, and
a lens blank holding section configured to hold a lens blank, the lens blank holding section including a central cavity formed concentrically with the central axis of the shank portion, the central cavity comprising a surface upon which projections are formed; and
a ring portion comprising an inner ledge;
wherein the mandrel assembly is configured such that, when the intraocular lens blank is held by the lens blank holding section and the ring portion is received within the central cavity, the projections contact and support a first bottom surface of the lens blank at a fixed distance from the surface of the central cavity and the inner ledge contacts and holds a second top surface of the lens blank opposing the first bottom surface of the lens blank.
2. The mandrel assembly of claim 1 , wherein a space is formed between the first bottom surface of the lens blank and the surface of the central cavity as the lens blank is supported by the projections.
3. The mandrel assembly of claim 2 , wherein the shank portion is configured to be received within a supporting collet.
4. The mandrel assembly of claim 2 , wherein the mandrel further comprises a second cavity that is concentric with the central cavity and has a smaller cross-sectional diameter than the central cavity.
5. The mandrel assembly of claim 2 , wherein the ring portion is configured to be held within the lens blank holding section by an interference fit formed with a sidewall portion of the central cavity.
6. The mandrel assembly of claim 2 , wherein the ring portion further includes a plurality of holes formed along an inner peripheral surface thereof, the holes being configured to permit a liquid to be transferred into the space formed between the first bottom surface of the lens blank as the lens blank is supported by the projections and the surface of the central cavity.
7. The mandrel assembly of claim 1 , wherein the inner ledge of the ring portion is configured to hold the intraocular lens blank onto the mandrel by pressing down on the second top surface of the intraocular lens blank while the first bottom surface of the intraocular lens blank is supported by the projections of the mandrel.