Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
1999-01-15
2001-08-07
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S233000
Reexamination Certificate
active
06270219
ABSTRACT:
TECHNICAL FIELD
This invention relates to a plastic trial lens used for testing eyesight and the like of testees, an injection molded product for making the plastic trial lens, and a mold assembly for molding the injection molded product for the plastic trial lens.
BACKGROUND ART
A trial lenses exchanged method, which is a subjective refraction tests, has been adopted for the prescription of glasses for selecting the most suitable lens for each user of glasses for some time. When the trial lenses exchanged method is conducted, a testee wears trial frames for trial lenses. Many kinds of trial lenses with various spherical diopters and astigmatic diopters and the like selected among a set of trial lenses are fitted in trial frames, thereby selecting the most suitable lens for each testee. A trial lens used in the trial lenses exchanged method has a grip portion on a periphery of a lens portion. By gripping the grip portion, the trial lens is set in and taken off from the trial frames.
A conventional trial lens is mainly made of glass. The trial lens is manufactured by attaching a holder ring member with a grip portion on the periphery of the lens cut (edge-filed) into the fixed size (Japanese Utility Model Laid-open No. Hei 4-22902). Some conventional trial lenses are plastic, but the manufacturing process after cutting is the same as that of glass trial lenses.
Besides manufacturing lenses, the conventional trial lens manufacture requires the process of manufacturing members for grip portions with different materials from the lenses and attaching the members on lenses, which takes a lot of time and labor.
Members for grip portions are made of metal in view of durability and easy operation, which causes the disadvantage that a trial lens is heavy as a whole. In complicated prescriptions for glasses for astigmatism, glasses for both far vision and near vision and the like, trial tests are conducted by setting more than one trial lenses one on another in trial frames so that the ears and nose of a testee get a heavy weight, which causes another disadvantage that the trial frames are easy to slip off. The diameter of the trial lens is small so that after-processing such as edge-filing and holder ring attaching is difficult. The grip portion is disposed at the fixed angle, for example, at the upper right or at the upper left of the lens in consideration of setting work in trial frames. In a trial lens with differences between the top and the bottom and between the right and the left, such as a progressive multifocal lens and a lens for an astigmatism, when a holder ring with a grip portion is attached on the periphery of the trial lens, precise positioning of the above fixed angle concerning the grip portion is required in accordance with an optical layout in the design of the lens about an optical center position and the like, which makes the attaching process of the holder ring difficult in a trial lens with a short diameter. Moreover, when the holder ring with the grip portion is caulked too strongly on the periphery of the lens, in a plastic lens, this situation causes an optical surface to be deformed, which brings about optical distortion and the like.
An object of the present invention is to provide a plastic trial lens, in which the process of manufacturing a member for a grip portion with different materials from a lens and attaching the member on the lens is omitted, the whole trial lens is more light-weight and the precise layout of the grip portion in relation to the lens portion is obtained, and an injection molded product to make the plastic trial lens, and moreover, a mold assembly to mold the injection molded product.
DISCLOSURE OF THE INVENTION
A plastic trial lens according to the present invention is provided with a lens portion and a grip portion integrally formed on a periphery of the lens being gripped when the lens portion is set in trial frames for trial lenses, the grip portion being molded simultaneously with the lens portion.
The trial lens according to the present invention is plastic, in which the grip portion is integrally molded with the lens portion. The lens portion and the grip portion are molded out of the same synthetic resin, the grip portion being molded simultaneously with the lens portion, which omits the process of attaching a member for the grip portion on the lens portion. The grip portion is formed out of the same synthetic resin as the lens portion so that the whole trial lens is lightweight. The grip portion is integrally molded with the lens portion after being positioned in a mold assembly so as to be formed in the fixed position of the lens portion, and hence the grip portion is disposed in relation to the lens portion in a fixed position accurately laid out.
An injection molding method, an injection compression molding method or a casting method (cast molding method) can be adopted to manufacture the above-described plastic trial lens in which the lens portion and the grip portion are integrally molded.
However, the casting method uses thermosetting resins (diethylene glycol bisuallyl carbonate is typical) for materials. The polymerization shrinkage percent of thermosetting resin is as large as about 14 percent. Therefore, the difference between a lens shape in design and a real mold transfer shape is large so that extremely high manufacturing technology is required to make precision mold transfer of a molded product attain the high precision required for the trial lens. In addition, molding a plastic lens by means of the casting method requires a molding time from 12 to 24 hours to precisely control the polymerization of the resin for the materials. As a result, one cycle of molding time becomes long, thus making mass-production of trial lenses costly. For the reasons stated above, it is preferable that the plastic trial lens is molded by means of the injection molding method or the injection compression molding method in which any disadvantage as described above does not occur.
When the plastic trial lens is molded by means of the injection molding method or the injection compression molding method, the thermoplastic resin used for the materials is such as a PMMA (polymethyl methacrylate) system resin or a PC (polycarbonate) system resin.
A holder ring can be attached on the periphery of the lens portion of the plastic trial lens, but it is preferable that an edge portion instead of the holder ring is integrally provided on the periphery of the lens portion, the edge portion being molded simultaneously with the lens portion.
Using the edge portion instead of the holder portion helps the trial lens to be more lightweight and omits a member for the holder ring. In addition, the process requiring the holder ring to be caulked on the periphery of the lens portion is unnecessary, which secures a high optical precision of the lens portion.
The plastic trial lens according to the present invention can be a progressive multifocal lens with a portion for far vision, a portion for near vision and a progressive portion between the portion for far vision and the portion for near vision or a lens for an astigmatism. The present invention is applicable to both a single vision lens and a multifocal lens which has a portion for near vision and a portion for far vision but no progressive portion.
When the trial lens is a progressive multifocal lens, it is preferable that the lens is provided with a mark indicating the direction of a horizontal datum line and a grip portion shifting to the right or the left from the center between the right portion and the left portion of the lens portion on the periphery of the lens portion according to the lens for a right eye or for a left eye.
Thus, the distinction between a lens for a right eye and a left eye in each progressive multifocal trial lens and the horizontal direction are clearly known with the position of the grip portion and the mark. As a result, while distinguishing the trial lens for a right eye from that for a left eye, the position of revolving direction of the round shaped lens portion as a
Flynn ,Thiel, Boutell & Tanis, P.C.
Hoya Corporation
Sugarman Scott J.
LandOfFree
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