Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Including step of mold making
Reexamination Certificate
2001-04-09
2002-11-05
Silbaugh, Jan H. (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Including step of mold making
C264S002200, C264S328800, C425S575000, C425S588000, C425S808000
Reexamination Certificate
active
06475410
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for producing a contact lens material, and a die assembly for injection molding used in the method and apparatus. More particularly, the present invention is concerned with such a method for producing the contact lens material which has two opposite lens-forming surfaces and which provides a contact lens or a lens blank which gives the contact lens, wherein steps of injection-molding resin molds in a die assembly, filling a contact lens molding material into the resin molds, and assembling the resin molds together, are effected without removing the resin molds from dies of the die assembly. The present invention also relates to the apparatus used for the method, and the die assembly used for the apparatus.
2. Discussion of the Related Art
In recent years, disposable contact lenses have been widely used by contact lens users on the ground that the disposable contact lenses assure the lens users of easy handling thereof and a high degree of safety with the eyes of the lens users, since the lens users are capable of discarding stained contact lenses and wearing new ones when necessary. Accordingly, the market of such disposable contact lenses has been rapidly expanded.
As a technique for mass-producing such contact lenses at a low cost, there has been practiced a method (mold polymerization method) which uses a pair of molds (mold halves) which respectively give an inner surface (base curved surface) and an outer surface (front curved surface) of an intended contact lens. The pair of molds define therebetween a mold cavity having a configuration following that of the contact lens. The mold cavity is filled with a molding material in the form of a suitable polymeric monomer composition, which is polymerized to form the intended contact lens. Further, there has been practiced another method to produce a contact lens by effecting a simple cutting operation on one of or both of opposite surfaces of a lens blank which has been obtained by a method similar to the above-described mold polymerization method and which has one of the inner and outer surfaces of the intended contact lens, or a lens blank which has been obtained by a method similar to the above-described mold polymerization method and which has a surface and/or surfaces approximating the inner and/or outer surfaces of the contact lens.
The above-described methods for producing a contact lens material which has opposite two lens-forming surfaces and which provides a contact lens or a lens blank that gives the contact lens permit mass-production of the contact lens so as to meet the demand of the market, since these methods reduce a required amount of the monomer and simplify the process steps of producing the contact lens, as compared with a cutting method conventionally effected to produce a contact lens by cutting a block of polymer into an intended configuration of the contact lens.
Some techniques have been proposed in JP-A-9-19972 and JP-A-9-323366, for instance. These publications disclose an apparatus for assembling contact lens molds in which a polymeric monomer mixture is filled so as to form a contact lens. Described in detail, the monomer is introduced into the molds while the molds are transferred, and the molds are assembled together to form the contact lens. JP-A-10-156887 and JP-A-10-180830 disclose a method of uniformly injection-molding molds for forming the contact lens by polymerization of the monomer therein.
In producing the contact lens by the mold polymerization method described above, various attempts have been made to reduce a cost of manufacture of the contact lens, so that the inexpensive disposal contact lenses described above are put on the market. In the above-described methods, the resin molds for forming the contact lens, which include a front-curve mold and a back-curve mold, are formed by using dies, and each of the formed molds is taken out of the corresponding molding cavity defined between the dies. Subsequently, a monomer or a monomer mixture is introduced into a recess of one of the formed front-curve mold and the back-curve mold (generally, the front-curve mold), and the monomer or monomer mixture is polymerized with the two molds being assembled together. Upon completion of the polymerization of the monomer or monomer mixture, the molds are separated away from each other. Then, the formed contact lens article is subjected to a hydration process and an inspection process, to thereby provide an intended contact lens.
In assembling the two molds together for forming the contact lens, the front-curve mold and the back-curve mold tend to be misaligned relative to each other with their axes or centers being offset from each other, giving an adverse influence on the dimension of the contact lens to be obtained, especially the thickness of the central portion of the contact lens. This causes deficiency of the contact lens whose configuration deviates from a certain nominal specification, resulting in a low non-defective ratio of the contact lens.
After the molds have been injection-molded, the molds are removed from the dies, and are relocated for introducing thereinto the polymeric monomer for the contact lens. During the relocation, oxygen may be adsorbed or absorbed on, and dust or dirt may adhere to, the resin surface of the molds, undesirably causing insufficient polymerization of the monomer and undesirable entrance of foreign matters in the contact lens.
SUMMARY OF THE INVENTION
The present invention was developed in the light of the above situations. It is therefore an object of the present invention to provide a method and an apparatus for producing a contact lens material with high dimensional accuracy, and an injection molding die assembly suitably used for the method and apparatus. It is another object of the invention to provide a technique and an apparatus for accurately assembling together two resin molds used for producing the contact lens material. It is also an object of the invention to provide a method and an apparatus for producing the contact lens material with high dimensional accuracy while effectively avoiding or minimizing adverse influences which arise from the use of the resin molds, such as insufficient polymerization of the monomer and adhesion of dust to the resin surfaces of the molds.
The above-indicated objects of the present invention may be attained according to one aspect of the invention, which provides (1) a method of producing a contact lens material which has opposite two lens-forming surfaces and which provides a contact lens or a lens blank which gives the contact lens, the method being characterized by comprising the steps of: (2) injection-molding a first resin mold having a molding surface which provides one of the opposite lens-forming surfaces of the contact lens material, by closing a first die and a second die so as to define at least one mold cavity therebetween, and injecting a suitable resin material into the at least one mold cavity so as to fill the at least one mold cavity; (3) injection-molding a second resin mold having a molding surface which provides the other of the opposite lens-forming surfaces of the contact lens material, by closing a third die and a fourth die so as to define at least one mold cavity therebetween, and injecting a suitable resin material into the at least one mold cavity so as to fill the at least one mold cavity; (4) separating the first and second dies away from each other such that the first resin mold is held on one of the first and second dies with its molding surface being removed from the other of the first and second dies; (5) separating the third and fourth dies away from each other such that the second resin mold is held on one of the third and fourth dies with its molding surface being removed from the other of the third and fourth dies; (6) introducing a molding material which gives the contact lens material into one of the first and second resin molds which are held on the one of the firs
Burr & Brown
Heckenberg Donald
Silbaugh Jan H.
Tomey Corporation
LandOfFree
Method and device for producing contact lens elements and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for producing contact lens elements and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for producing contact lens elements and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2945668