Mandrel for use in the machining of ophthalmic lenses
A mandrel 1 for holding an ophthalmic lens member blank 16 during machining is disclosed. The mandrel 1 has a front surface 6 for receiving an ophthalmic lens member blank 16 to be machined. The front surface 6 comprises a planar surface region 10 ; a curved surface region 8 ; and a drainage channel 12 located between the curved surface region 8 and the planar surface region 10 such that wax applied to the curved surface region 8 flows into the drainage channel 12 . A kit of parts comprising such a mandrel 1 , a method of mounting an ophthalmic lens member blank 16 for machining, a method of machining an ophthalmic lens member blank 16 , an ophthalmic lens produced using the apparatus and a batch of such lenses are also disclosed.
1 . A mandrel and an ophthalmic lens member blank to be machined, the mandrel holding the ophthalmic lens member blank, the ophthalmic lens member blank having a surface comprising a curved surface region and a planar surface region, the mandrel having a front surface receiving the ophthalmic lens member blank to be machined; the front surface comprising;
a planar surface region of the mandrel abutting the planar surface region of the ophthalmic lens member blank;
a curved surface region of the mandrel with wax applied thereto, the ophthalmic lens member blank placed onto the wax; and
a drainage channel extending along at least a portion of the boundary between the curved surface region of the mandrel and the planar surface region of the mandrel such that wax applied to the curved surface region flows into the drainage channel.
2 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the curved surface region of the mandrel is convex and is centrally located on the front surface, and the planar surface region of the mandrel is annular and concentrically located with the curved surface region of the mandrel.
3 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the curved surface region of the mandrel defines a dome, and the mandrel is configured such that the dome can be received in a concave recess defined by the posterior surface of an ophthalmic lens member blank while the ophthalmic lens member blank abuts the planar surface region of the mandrel.
4 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the drainage channel extends along the whole of the boundary between the curved surface region of the mandrel and the planar surface region of the mandrel.
5 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the mandrel comprises a stem and a flange extending radially from the stem at one end of the stem, a surface of the flange on the opposite side of the flange to the stem defining the planar surface region of the mandrel.
6 . The mandrel and an ophthalmic lens member blank according to claim 5 , wherein the flange and/or stem comprises a socket and the mandrel further comprises a center-piece comprising a body and a leg extending therefrom, the mandrel being configured such that when the leg is received in the socket a front body surface of the body defines the curved surface region of the mandrel.
7 . The mandrel and an ophthalmic lens member blank according to claim 6 , wherein the mandrel is configured such that when the leg is received in the socket the drainage channel is defined between the center-piece and the flange.
8 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein a portion of the drainage channel extends beneath the curved surface region of the mandrel.
9 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the front surface comprises one or more overflow channels extending radially from the drainage channel to an edge of the flange.
10 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the curved surface region of the mandrel has one or more grooves therein to retain wax.
11 . The mandrel and an ophthalmic lens member blank according to claim 1 , wherein the ophthalmic lens member blank is a contact lens member blank.
12 . A kit of parts comprising the mandrel and an ophthalmic lens member blank according to claim 1 , and further comprising a socket in the front surface for receiving a center-piece, the kit of parts further comprising one or more of the following: a center-piece comprising a body having a convex body surface, the center-piece being configured to be received in the socket such that the convex body surface defines the curved surface region of the mandrel; a center-piece comprising a body having a concave body surface, the center-piece being configured to be received in the socket such that the concave body surface defines the curved surface region of the mandrel.
13 . A method of mounting an ophthalmic lens member blank on a mandrel for machining, the mandrel having a front surface comprising a planar surface region, a curved surface region and a drainage channel extending along at least a portion of the boundary between the curved surface region and the planar surface region, the ophthalmic lens member blank having a surface comprising a curved surface region and a planar surface region, the method comprising applying wax to the curved surface region of the mandrel and placing the ophthalmic lens member blank on the wax with the planar surface region of the ophthalmic lens member blank abutting the planar surface region of the mandrel, thereby causing wax to flow into the drainage channel from the curved surface region of the mandrel.
14 . The method according to claim 13 , wherein wax from the curved surface region of the mandrel is retained by the drainage channel such that no wax flows from the curved surface region of the mandrel to the planar surface region of the mandrel.
15 . The method of machining an ophthalmic lens member blank, the method comprising mounting the ophthalmic lens member blank on a mandrel in accordance with the method of claim 13 , and then mounting the mandrel on a machine tool and machining the ophthalmic lens member blank.
16 . The method according to claim 13 , wherein the ophthalmic lens member blank is a contact lens member blank.
17 . The method according to claim 16 , wherein the contact lens member blank is a rigid contact lens member blank.
18 . The method according to claim 16 , wherein the contact lens member blank is a soft contact lens member blank.
19 . The method according to claim 18 , wherein the soft contact lens member blank is a hydrogel contact lens member blank or a silicone hydrogel contact lens member blank.