Cast mould for manufacturing contact lenses or intraocular lenses
A cast mould for manufacturing a contact lens or an intraocular lens, wherein the cast mould is provided with a central part and a bearing ring and a flexible connection between the central part and the bearing ring. Further, an injection mould is provided for manufacturing such a cast mould and a method for manufacturing such a cast mould. The injection mould is provided with a mould cavity with a plunger biased by spring means towards the mould cavity which serves for compensating shrinkage which occurs during the curing of the plastic injected into the injection mould. Also described is a method for manufacturing a contact lens or intraocular lens with the aid of the cast mould, as well as a contact lens or intraocular lens obtained with this method.
1. An injection mould for forming a cast mould, comprising:
a first injection mould half;
a second injection mould half; and
at least one injection mould cavity formed between the first injection mould half and second injection mould half, the at least one injection mould cavity comprising the following connected cavities:
a central part cavity centered on a longitudinal central axis (A);
a bearing ring cavity radially outward of the central part cavity; and
a connecting cavity fluidly connecting the central part cavity to the bearing ring cavity, wherein an axial height of the connecting cavity is less than 0.1 times an axial height of the central part cavity at the longitudinal central axis (A);
a plunger in the first injection mould half, the plunger movable along the longitudinal central axis (A), the plunger having an end face facing the at least one injection mould cavity and forming a boundary of the central part cavity; and
a spring urging the plunger toward the second injection mould half, wherein
the cast mould is formed by injecting a flowable material into the entire injection mould cavity.
2. The injection mould according to claim 1 , further comprising a first stop forming a boundary for movement of the plunger towards the second injection mould half.
3. The injection mould according to claim 2 , comprising a second stop forming a boundary for movement of the plunger from a pressed-in position to a stop position spaced from the injection mould cavity.
4. The injection mould according to claim 1 , wherein the spring comprises one or more Belleville springs.
5. The injection mould according to claim 1 , wherein the central part cavity is bounded on one side by the end face of the plunger and on an opposite side by a wall part of the second injection mould cavity, wherein a circumferential wall of the central part cavity is chamfered, such that a diameter of the central part cavity, viewed in the direction of the longitudinal central axis (A), gradually increases from the plunger towards the second injection mould half.
6. The injection mould according to claim 2 , wherein the first stop is a cylinder surrounding the plunger.
7. The injection mould according to claim 3 , wherein the first stop is a tubular bush surrounding the plunger, and wherein the second stop is a tubular bush located within the first stop and on a side of the plunger opposite the end face.
8. The injection mould according to claim 1 , further comprising a first stop, the first stop being a tubular bush surrounding the plunger, wherein the connecting cavity is formed between an end face of the tubular bush and the second injection mould half.
9. The injection mould according to claim 1 , wherein the axial height of the connecting cavity is less than 0.2 times an axial height of the bearing ring cavity.
10. The injection mould according to claim 1 , wherein the connecting cavity is ring-shaped.
11. The injection mould according to claim 10 , wherein the bearing ring cavity is ring-shaped, and wherein the connecting cavity is configured to create an annular plastic film which connects a bearing ring formed in the bearing ring cavity with a central part formed in the central part cavity.
12. The injection mould according to claim 1 , wherein the connecting cavity comprises a plurality of spoke-cavities which extend radially or radially/tangentially from the central part cavity to the bearing ring cavity and connect the central part cavity with the bearing ring cavity.
13. The injection mould according to claim 12 , wherein the bearing ring cavity is ring-shaped, and wherein the spoke-cavities are configured to create a plurality of spokes which are each connected by a first end to the central part formed in the central part cavity and to the bearing ring formed in the bearing ring cavity.
14. The injection mould according to claim 1 , wherein the axial height of the connecting cavity is less than an axial height of the bearing ring cavity.
15. The injection mould according to claim 1 , wherein the axial height of the connecting cavity is less than 0.1 times an axial height of the bearing ring cavity.