Static molds – Container-type molding device – Having plural mold sections
Reexamination Certificate
1999-06-01
2001-07-10
Heitbrink, Tim (Department: 1722)
Static molds
Container-type molding device
Having plural mold sections
C249S117000, C425S808000
Reexamination Certificate
active
06257547
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE ART
The present invention relates to a mold assembly for forming an ophthalmic lens such as a contact lens or an intraocular lens. More particularly, the invention is concerned with such a mold assembly which does not need a sharp annular protrusion or edge portion such as a knife-edge portion for defining an edge of the ophthalmic lens.
DISCUSSION OF THE RELATED ART
There have been proposed various techniques for producing an ophthalmic lens by a mold assembly consisting of a first mold and a second mold in the form of a male mold and a female mold or an upper mold and a lower mold, which are assembled together so as to define therebetween a mold cavity having a configuration that gives the intended ophthalmic lens such as a contact lens or an intraocular lens. The mold cavity defined upon closing or assembling of the first and second molds is filled with a suitable lens material to mold the intended ophthalmic lens.
To define the mold cavity between the two molds, the two molds are assembled together such that they are held in close contact with each other at their radially outer peripheral portions functioning as abutting contact portions, so that the ophthalmic lens to be obtained in the mold cavity has an intended edge profile defined by the abutting contact portions of the two molds which are held in close contact with each other, and so that the mold cavity defined between the two molds is fluid-tightly sealed so as to prevent leakage of the lens material therefrom during a molding operation for forming the ophthalmic lens. In general, the abutting contact portions of the two molds make close line contact or surface contact with each other to define the fluid-tight mold cavity. When the two molds are constructed for the line contact, the abutting contact portion of one of the two molds is in the form of a sharp annular protrusion such as a knife edge that is brought into line contact with the abutting contact portion of the other mold. When the two molds are constructed for the surface contact, the two molds have respective flat mating surfaces which are brought into abutting surface contact with each other for defining the mold cavity.
U.S. Pat. Nos. 5,238,388 and 5,395,558 disclose one example of the mold assembly constructed for the line contact. In this mold assembly consisting of a male and a female mold, at least one of the two molds has a knife-edge portion which is held in line contact with the other mold. In a molding operation using the thus formed mold assembly, the knife-edge portion of the above-indicated one mold is held in abutting contact with the corresponding portion of the other mold to define a fluid-tightly sealed mold cavity between the two molds while the two molds are forced together, so that a lens material filling the mold cavity is polymerized to produce an intended ophthalmic lens. The mold assembly disclosed in the U.S. Patent, however, suffers from various problems. For instance, it requires a high level of worker's skill to form the mold assembly with such a knife-edge portion, resulting in a low non-defective ratio of the mold assembly when the mold assembly is produced by a molding operation as generally employed in the art. Further, if the knife-edge portion is not formed with high accuracy of configuration, the ophthalmic lens to be obtained does not have an intended edge profile.
U.S. Pat. No. 4,209,289 discloses one example of the mold assembly constructed for the surface contact. In this mold assembly consisting of a male and a female mold, the male mold has a flat mating surface extending radially outwardly of the periphery of its convex molding surface, while the female mold has a flat mating surface extending radially outwardly of the periphery of its concave molding surface. When the male and female molds are assembled together, the flat mating surfaces of the two molds are held in abutting contact with each other to define a fluid-tightly sealed mold cavity between the two molds. In the thus formed mold assembly, if the mating surfaces of the two molds are not accurately aligned or engaged with each other, the configuration of the mold cavity may undesirably have a deviation with respect to the nominal design. In this case, the configuration of the ophthalmic lens to be formed in the mold cavity may have a corresponding deviation. In particular, the obtained ophthalmic lens does not have an intended edge profile due to the misalignment of the mating surfaces of the two molds.
JP-A-5-337957 and JP-A-6-170858 disclose another example of the mold assembly constructed for the surface contact. The disclosed mold assembly consists of two identically constructed molds. Each of the two molds has a concave and a convex mold surface, and two flat contacting surfaces formed radially outwardly of the convex and concave mold surfaces, respectively. When the two molds are assembled together, their contacting surfaces are brought into abutting contact with each other, so as to define a fluid-tightly sealed mold cavity between the two molds. The thus constructed mold assembly requires a relatively large clamping force for holding the two molds together such that the contacting surfaces are kept in abutting contact with each other during a molding operation for forming an intended contact lens. The clamping force applied to the molds, however, may cause deformation of the molds, undesirably resulting in a change in the spherical degree of the ophthalmic lens to be obtained and a change in the volume of the mold cavity. Further, for establishing close abutting contact between the contacting surfaces of the two molds, the contacting surfaces need to be have high accuracy of straightness.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a mold assembly which permits easy production of an intended ophthalmic lens having a desired edge profile, and which does not have a sharp protrusion such as a knife edge, or which does not require a large force for keeping the molds in a closed state to define a fluid-tightly sealed mold cavity.
The above-described object of the present invention may be attained according to a principle of the present invention, which provides a mold assembly for forming an ophthalmic lens, the mold assembly comprising a first mold and a second mold which cooperate with each other to define therebetween a mold cavity having a profile following that of the ophthalmic lens with the first and second molds being held in line contact with each other at a predetermined radial position, wherein the improvement comprises: at least one of the first and second molds consisting of a central molding portion located radially inwardly of the radial position, and an outer rim portion located radially outwardly of the radial position, the central molding portion of the at least one mold cooperating with the other mold to define therebetween the mold cavity when the two molds are assembled together; and the at least one mold having a mold surface which is opposed to a mold surface of the other mold when the two molds are assembled together, the mold surface of the at least one mold consisting of a central lens-forming region in the central molding portion, and an outer peripheral non lens-forming region in the outer rim portion, at least a part of the lens-forming region which is adjacent to the radial position providing a concave portion, while at least a part of the outer peripheral non lens-forming region which is adjacent to the radial position providing a convex portion.
In the present mold assembly wherein the first and second molds are held in line contact with each other at the radial position, and at least one of the first and second molds has the mold surface which consists of the central lens-forming region in the central molding portion, and the outer peripheral non lens-forming region in the outer rim portion, at least a part of the lens-forming region which is radially inwardly adjacent to the radial position is made concave to provide the concave p
Ishihara Kenichi
Togo Motonobu
Burr & Brown
Heckenberg Donald
Heitbrink Tim
Menicon Co. Ltd.
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