Method for molding lenses

• US 5,271,875 A
• Filed: 09/12/1991
• Issued: 12/21/1993
• Est. Priority Date: 09/12/1991
• Status: Expired due to Term

• Current Assignee: Bausch & Lomb Incorporated (Bausch Health Cos., Inc.)
• Original Assignee: Bausch & Lomb Incorporated (Bausch Health Cos., Inc.)
• Inventors: Appleton, William J., Ruscio, Dominic V., Shannon, John H., Hahn, Dennis, Weaver, Edwin W. Jr., Moucha, William E., Silbermann, Steven D.
• Primary Examiner(s): Thurlow, Jeffery
• Assistant Examiner(s): VARGOT, MATHIEU D
• Application Number:
  US07/758,046
• Time in Patent Office: 831 Days
• Field of Search: 264/2.2, 264/2.3, 264/2.4, 264/2.6, 264/313, 264/319, 425/808, 249/82, 249/160
• US Class Current: 264/2.3
• CPC Class Codes: B29C 33/0011 thin-walled moulds
• CPC Class Codes: B29C 33/0038 with sealing means or the like seals on envelopes used in tyre retreading B29D30/542; for injection moulding footwear B29D35/0045
• CPC Class Codes: B29C 33/0055 with incorporated overflow cavities in particular in injection moulds B29C45/2669
• CPC Class Codes: B29C 33/303 centering mould parts or halves, e.g. during mounting
• CPC Class Codes: B29C 37/006 Degassing moulding material or draining off gas during moulding venting means in moulds B29C33/10
• CPC Class Codes: B29C 43/00 Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor by liberation of internal stresses B29C61/006
• CPC Class Codes: B29C 43/10 Isostatic pressing, i.e. using non-rigid pressure-exerting members against rigid parts or dies
• CPC Class Codes: B29D 11/00038 Production of contact lenses
• CPC Class Codes: B29D 11/00057 characterised by the shape or surface condition of the edge, e.g. flashless, burrless, smooth
• CPC Class Codes: B29D 11/00125 Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere
• CPC Class Codes: B29D 11/0049 Double sided moulds
• CPC Class Codes: B29D 11/005 having means for aligning the front and back moulds
• CPC Class Codes: B29D 11/00576 with means to engage flash, e.g. HEMA ring
• CPC Class Codes: B29D 11/00586 and removing the flash or HEMA ring
• CPC Class Codes: Y10S 425/808 Lens mold

Abstract

A mold assembly includes first and second mold sections having respective first and second mold cavity defining surfaces, the first mold cavity defining surface terminating in an encircling peripheral rim and the second mold cavity defining surface terminating in a deformable peripheral annulus disposed at a diameter corresponding to the rim, and cooperating tapers depending from each of the first and second molds for relatively centering the molds.

Claims

1. A lens molding method comprising:

depositing lens material in a first mold section;

seating a second mold section adjacent the first mold section and sealing the first and second mold sections so as to define a mold cavity sealed at an edge thereof, with excess lens material being received in a space adjacent the edge of the mold cavity;

curing the lens material to form a molded lens; and

accommodating, during curing, shrinkage in the lens material by relatively deforming a rim of one of said first and second mold section and a deformable mating surface on the other of said first and second mold sections;

wherein an edge of the lens is formed at a point of deformation of the rim and the deformable mating surface.

2. A method according to claim 1, wherein the amount of lens material deposited in said depositing step is metered such that excess lens material is deposited in the first mold section.

3. The method of claim 1, wherein the excess lens material is confined in the space adjacent to the edge of the mold cavity.

4. The method of claim 1, further comprising clamping said first and second mold sections by applying a clamping force during curing.

5. The method of claim 4 wherein the clamping force is sufficient to seal the mold cavity but without excessive deformation.

6. The method of claim 5 wherein the clamping force is within the range of about 20-40 pounds.

7. The method of claim 4 wherein the first and second mold sections are clamped by applying an external clamping force.

8. The method of claim 7 wherein the clamping force is maintained at a constant level throughout curing of the lens material.

9. The method of claim 4 wherein the first and second mold sections are clamped by taper-lock clamping means.

10. A method according to claim 1, further comprising disassembling the first and second mold sections such that the molded lens remains with one of said first and second mold sections.

11. The method of claim 10 wherein the mold sections are formed from different materials such that the cured lens preferentially remains on one of the mold sections after disassembly of the mold sections.

12. A method according to claim 10, wherein excess lens material is retained in the other of said first and second mold sections.

13. A method according to claim 10, further comprising hydrating the molded lens.

14. A method according to claim 1, further comprising centering the first mold section with respect to the second mold section during said seating step.

15. A method according to claim 14, wherein said centering comprises inserting a generally cylindrical shell of one of said first and second mold sections into a correspondingly shaped generally cylindrical shell of the other of said first and second mold section.

16. A method according to claim 15, wherein the cylindrical shells are tapered and the tapers are substantially equal.

17. A method according to claim 15, wherein the cylindrical shells are tapered and the tapers are different.

18. A method according to claim 1, wherein a rim is defined by the corner of a right cylindrical wall of the mold cavity.

19. The method of claim 1, wherein the first mold section comprises a mold cavity defining surface including a central optical zone and, at a periphery of the mold cavity defining surface, a right cylindrical wall whose corner defines the deformable rim.

20. The method of claim 19, wherein the first mold section further comprises a collar surrounding the rim for confining the excess lens material in the space adjacent to the edge of the mold cavity.

21. The method of claim 19, wherein the first mold section comprises a generally cylindrical base and a tapered head.

22. The method of claim 1, wherein the second mold section comprises a mold cavity defining surface including a central optical zone and, at a periphery of the mold cavity defining surface, a reversely angled deformable mating surface.

23. The method of claim 22, wherein the deformable mating surface comprises an annulus.

24. The method of claim 23, wherein said annulus is radiused.

25. The method of claim 1, wherein the first and second mold sections comprise respective anterior and posterior mold cavity defining surfaces, said first mold section including, at a periphery of the anterior mold cavity defining surface, a right cylindrical wall whose corner defines the deformable rim, said second mold section including, at a periphery of the posterior mold cavity defining surface, a reversely angled deformable mating surface disposed at a diameter that corresponds to said deformable rim.

26. The method of claim 25, wherein the anterior and posterior mold cavity defining surfaces define a rigid mold cavity having a central optical zone.

27. The method of claim 25, wherein the deformable rim of the first mold section is a corner formed of the right cylindrical wall and an outwardly extending flange.

28. The method of claim 27, wherein the first mold section includes a collar surrounding the rim and extending from the flange for confining the excess lens material in the space adjacent to the edge of the mold cavity.