JPH045287Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a gasket for molding plastic lenses, and in particular to the structure of a gasket in which an upper mold and a lower mold are fitted together during cast polymerization of a plastic lens. Regarding.

[Conventional technology]

In the production of plastic lenses, a lens mold is formed by combining the upper and lower molds of a glass matrix and a gasket, and a monomer is injected into this mold and polymerized. Therefore, the gasket functions as a holder for the outer periphery of the matrix, determines the thickness of the lens, and also functions to prevent monomer from leaking out.

Lenses as finished or semi-finished products are manufactured using such molds.

By the way, in the case of a bifocal lens, there are powers for farsightedness, nearsightedness, and astigmatism in the far vision part, and there is also an additional power for near vision in each part. Furthermore, in the case of astigmatism, unlike the case of single vision lenses, the lens cannot be rotated to align with the astigmatism axis. For this reason, plastic lenses are manufactured in the form of semi-finished products using the molds described above.
They are processed and made into finished products according to individual orders.

Therefore, a bifocal lens is shaped so that the position of the small lens is placed at a predetermined position with respect to the geometric center of the lens.

After molding, it is necessary to fix a jig for measuring and processing the geometric center of the lens (hereinafter referred to as centering) so as to correspond to the prescription value order of the patient or the like.

For such lens processing work, an erasable mark is marked on the lens surface in advance, and the worker positions the lens by visual measurement based on the marking line (geometric center line, etc.) and fixes it to a lens jig. are doing.

Furthermore, according to Spanish Utility Model Registration No. 257196, an identification mark is attached to the lens during the manufacturing process, and according to a predetermined code such as the type, size, and position of the mark, the framing criteria of the lens manufacturer,
It is used for product identification and fixing to tools during the polishing process.

[Problem that the invention attempts to solve]

However, when centering a circular lens, the lens is first positioned visually using a marking device, marked on the lens surface, and then fixed to a jig using the marking line as a reference. There is a risk of errors and errors when fixing to the jig, and a high level of judgment is required from the operator, and many work errors occur.

Furthermore, the method disclosed in Spanish Utility Model Registration No. 257196 described above requires a new special grinding process for the lens, resulting in problems such as an increase in the number of manufacturing steps.

It is an object of the present invention to solve the problems of the prior art described above and to provide a gasket suitable for obtaining a plastic lens that is easy to center.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a cylindrical gasket into which an upper mold and a lower mold for forming an optical surface of a plastic lens are fitted.
Protrusions on which the upper mold can be placed are provided at the locations, two of the protrusions have different shapes to the extent that they can be distinguished from each other, and are arranged at opposite positions on the substantial diameter of the gasket. It is characterized by

[Effect]

An index section having a shape corresponding to the protrusion provided on the gasket is formed on the lens, and the positional relationship between the index section and the geometric center point, the small ball, etc. is determined in advance,
When fixing the lens to a jig, positioning (alignment) in a fixed direction is always possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a perspective view showing a gasket for molding a plastic lens according to the present invention, FIG. 2 and FIG.
The figure shows an upper mold and a lower mold that are fitted into the gasket of FIG. 1, respectively.

The gasket 1 has a cylindrical shape, and an obtuse-angled protruding inner wall flange 2 is formed on the inner wall surface of the gasket 1, and the inner wall flange 2 is formed on an extension line of the apex 2a of the inner wall flange 2 and the geometrical center point of the lens to be molded. It is arranged so that the center of the trapezoidal inner wall flange 3 is located. Therefore, the apex 2a of the inner wall flange 2 and the center of the inner wall flange 3 are arranged at positions corresponding to the diameter direction of the lens to be molded. The inner wall flange 2 and the inner wall flange 3 are located at the same height of the cylindrical gasket 1, and the depths of the inner wall flange 2 and 3 are also configured to be the same.

These inner wall flanges 2 and 3 have one vertex with respect to the circumferential surface of the gasket 1, and have an index for fixing a lens formed by a mold containing this gasket 1 to a jig. There is.

Therefore, since the inner wall flange 3 opposite to the inner wall flange 2 also functions as an indicator as described above, it is preferable that the inner wall flange 2 and the inner wall flange 3 have different shapes to the extent that they can be distinguished so that they can be distinguished as indicators.

The material for the gasket 1 is preferably a thermoplastic resin having a certain degree of rubber-like elasticity in view of its properties and ease of molding, such as vinyl chloride resin or ethylene-vinyl acetate copolymer.

The upper mold 4 shown in FIG. 2 has a concave surface 4a serving as a transfer surface for the convex surface of the lens, and the concave surface of the upper mold 4 has a shaped portion corresponding to a small bead portion to be formed on the lens. This bead portion corresponds to the near vision portion of the lens and is formed from a specific shape and radius of curvature. On the other hand, in the lower mold 5, the convex surface 5a serves as a transfer surface for the concave surface of the lens.

Note that the molds 4 and 5 are made of glass or, as the case may be, some kind of synthetic resin.

Next, a method of molding a lens using the above-described gasket 1, upper mold 4, and lower mold 5 will be described.

First, the upper mold 4 is fitted from the upper side of the gasket 1 with the concave surface 4a facing down, and is placed in contact with the upper end surfaces of the two inner wall flanges 2 and 3.
Next, the lower mold 5 is fitted into the gasket 1 from the lower side, and the end surfaces of the lower mold 5 are sandwiched.
The fitting depth of the lower mold 5 into the gasket 1 is:
The upper end surface of the lower mold 5 should be approximately 2.2 mm downward from the lower end surface of the inner wall collars 2 and 3.
It is arranged so that it does not come into contact with the lower end surface of.

A syringe needle is inserted into the boundary between the upper mold 4 and the gasket 1 of the lens mold thus assembled, and monomer is injected. As the monomer, for example, diethylene glycol bisallyl carbonate is used.

This monomer shrinks during polymerization, and the shrinkage rate is around 14%. This contraction causes gasket 1
is absorbed by the elastic force of Also, gasket 1
Because the lower end surfaces of the inner wall flanges 2, 3 and the upper end surface of the lower mold 5 are not in contact with each other and a gap is provided, part of the shrinkage during monomer polymerization occurs in the height direction of the cylindrical gasket 1. It is absorbed evenly along the (bottom side).

Next, the mold filled with the monomer is subjected to a heating polymerization process of the monomer in an electric furnace and annealed. Thereafter, the upper mold 4 and the lower mold 5 are released from the gasket 1, and the lens is taken out.

FIG. 4 is a front view of a plastic lens (bifocal lens as a semi-finished product) molded by the method described above, and FIG. 5 is a right side view of FIG. 4.

This lens 7 has a platform-type small bead 8 in the near vision portion. The position of this small bead 8 is arranged with the upper end of the small bead as a reference in the horizontal direction, a horizontal reference line 10 passing through the geometrical center point 9 of the lens 7, and a vertical reference line 11 that intersects with the geometrical center point 9 as a reference point. ing.

Further, an upper index portion 12 and a lower index portion 13 are formed at the upper and lower portions of the lens 7, and the upper index portion 12 has a shape corresponding to the inner wall flange 3 formed on the gasket 1 shown in FIG. , lower indicator part 1
3 is an inner wall flange 2 formed on the gasket 1 shown in FIG.
It has a shape corresponding to

That is, the upper indicator part 12 is formed into a trapezoidal shape, and the center of the upper side of the trapezoid is located on the vertical reference line 11.

Further, the lower indicator portion 13 has an included angle on two sides,
Its apex is located on the vertical reference line 11.

These index portions 12 and 13 are not formed on the entire edge portion (end surface) of the lens 7, but are formed from the bottom surface.
2.2mm is formed into a normal circular shape.

The diameter of the small bead 8 is 25 mm, its platform top line 14 is located 2.5 mm below the geometrical center point 9, and the optical center point 15 of the distance part is located 10 in the horizontal reference line direction from the geometrical center point 9. 2mm below and 2.5mm to the right of the vertical reference line.

Therefore, the position of the lower indicator part 13 (the apex of the included angle), the position of the small bead 8 from the position of the lower indicator part 13,
Layout information such as the optical center point 15 and the geometric center point 9 can be derived, and the lens 7 fixed to the jig can be processed based on this information.

In the embodiment described above, two inner wall flanges are provided on the gasket 1, but three or more protrusions like these inner wall flanges may be provided in total.

[Effect of idea]

As described above, according to the present invention, an index portion having a shape corresponding to the protrusion provided on the gasket is formed on the lens, and the positions of this index portion and the geometric center point, small beads, etc. are determined, so that the lens can be fixed. When fixing to a tool, it can always be positioned in a fixed direction.

Therefore, the marking process can be omitted, the positioning work is simplified, highly accurate positioning is possible, and machining errors can be prevented. Furthermore, automation of lens positioning work becomes possible.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the gasket of the present invention, Fig. 2 is a perspective view showing an upper mold fitted into the gasket shown in Fig. 1, and Fig. 3 is a perspective view showing an upper mold fitted into the gasket shown in Fig. 1. FIG. 4 is a front view of the lens formed by the mold shown in FIGS. 1 to 3, and FIG. 5 is a right side view of FIG. 4. be. 1... Gasket, 2, 3... Inner wall flange, 4...
Upper mold, 4a...concave surface, 5...lower mold, 5a...convex surface, 7...lens, 8...small ball,
9...Geometric center point, 10...Horizontal reference line, 11
... Vertical reference line, 12 ... Upper indicator section, 13 ...
Lower indicator section, 14... Platform top line, 1
5...Optical center point.

Claims (1)

[Scope of utility model registration request] In a cylindrical gasket into which an upper mold and a lower mold for forming an optical surface of a plastic lens are fitted, protrusions on which the upper mold can be placed are provided at at least two places on the inner wall surface of the gasket. A gasket for molding a plastic lens, characterized in that the two protrusions have different shapes to the extent that they can be distinguished from each other, and are arranged at opposing positions on a substantial diameter of the gasket.