JPH0331538Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gasket used in a cast polymerization method for plastic lenses.

[Conventional technology]

The cast polymerization method as a method for molding plastic lenses is already known; for example, in the May 22, 1986 issue of Medical Aoi Publishing, "Gegane", there is a description of the manufacturing process for lenses made of diethylene glycol bisallyl carbonate. is disclosed.
In the manufacturing process of this lens, lens casting is shown in which an upper mold and a lower mold of a glass mother mold are combined with a gasket.

In the cast polymerization method, a cavity formed by a mold and a gasket is filled with a liquid (monomer). There is a way to put it in between.

As a method of providing an injection port in a gasket, there is a method disclosed in Japanese Utility Model Publication No. 59-40189. In this method, as shown in FIG. 4, a cavity 24 is formed by fitting an upper mold 22 and a lower mold 23 into the fitting portion of a short cylindrical gasket 21. An injection port 25 is provided that penetrates the peripheral wall from a part of the inner peripheral surface of the gasket 21, and an injection pipe 26 that projects from the injection port 25 to the outer peripheral wall is formed integrally with the peripheral wall. The monomer is injected from the injection pipe 26 while evacuating the cavity 24 so that no air remains, and then the injection pipe 26 is closed. Next, it is heated in a polymerization furnace to polymerize the monomers and mold the plastic lens.

As a method of sandwiching the injection tube between the mold and the gasket, there is a method disclosed in US Pat. No. 2,542,386. In this method, as shown in FIG. 5, an upper mold 28 and a lower mold 29 are fitted into a short cylindrical gasket 27 and held between springs 30 to form a cavity. Next, gasket 27
A flat injection pipe 31 is placed between the upper mold 28 and the upper mold 28.
The monomer is injected from here. Once the cavity is filled with monomer, insert the injection tube 31
When the injection tube 31 is pulled out with a small amount of monomer coming out, the space between the gasket 27 and the upper mold 28 is sealed again by the biasing force of the spring 30, and the injection is completed after making sure that no air remains. complete.

[Problem that the invention attempts to solve]

However, in the example shown in FIG. 4, if the distance between the upper mold 22 and the lower mold 23 is small, the inner wall of the gasket 21 becomes thin, and the injection port 25 to be penetrated therein is formed. becomes extremely difficult. Furthermore, if the distance between the upper mold 22 and the lower mold 23 is large, the diameter of the injection port 25 becomes relatively small compared to the thickness of the inner wall, making it difficult to completely remove the air inside the cavity 24. It becomes difficult. In addition, the injection port 25 and the cavity 24
Since the structure has a continuous structure, a protrusion in the shape of the injection port 25 remains on the outer peripheral surface of the molded lens, requiring a process to remove this protrusion, and furthermore, optical distortion occurs around the removed part. This occurs and marks are left on the outer periphery of the removed portion.

On the other hand, in the example shown in FIG. 5, the monomer is injected in an amount slightly larger than the cavity volume formed by the gasket 27, the upper mold 28, and the lower mold 29, and the monomer is injected while flowing out from the injection pipe 31. Not only is excess monomer spilled out and wasted when the tube 31 is pulled out, but the monomer also adheres to the gasket 27, upper mold 28, and lower mold 29. Therefore, it is necessary to take measures such as placing absorbent paper under the lower mold 29 so as not to contaminate the inside of the polymerization furnace, and when the mold is reused, the burden of cleaning it increases.

The purpose of the present invention is to solve the above-mentioned problems of the conventional technology, to easily arrange an injection port regardless of variations in mold spacing, that is, variations in wall thickness due to lens power, and To provide a plastic lens casting gasket which allows easy air evacuation and allows stable production of plastic lenses.

[Means to solve the problem]

The present invention has been made to achieve the above object, and has a ring-shaped protrusion band on the inner wall surface of the cylindrical body along the circumferential direction, and the upper and lower end surfaces of the protrusion band are respectively on the upper and lower sides. The lower end surface of the die mold and the upper end surface of the lower die mold are formed so as to be able to come into contact with each other, and the inner circumferential surface of the cylindrical body is formed so as to be able to hold the mold, and a part of the ring-shaped protrusion band is formed so that the upper end surface of the lower die mold can come into contact with each other. A recess extending from the end face to the lower end face is formed, and a monomer inlet having an upward opening is formed on the outer peripheral wall side of the cylindrical body adjacent to the recess, and the bottom of the monomer inlet and the It is characterized in that the bottom of the recess is communicated with the bottom of the recess through a through hole formed in the cylindrical body.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a plan view showing an embodiment of the gasket of the present invention, and FIG. 2 is a sectional view taken along line A--A in FIG.

This gasket 1 is formed into a cylindrical shape, and on the inner wall surface 2a of the cylindrical body 2, a ring-shaped protrusion band 3 is provided along the circumferential direction at approximately the middle position of the cylindrical body 2 in the height direction.
is formed. A side wall 4 having a substantially semicircular horizontal cross section is provided on the outer wall surface 2 b of the cylindrical body 2 , and a monomer injection port 5 is formed by this side wall 4 and the outer peripheral surface of the cylindrical body 2 . This monomer inlet 5
A recess 6 extending from the upper end surface to the lower end surface is formed in the ring-shaped projection band 3 adjacent to the ring, and a through hole 7 is provided in the cylindrical body 2 to communicate the recess 6 with the monomer injection port 5. It is set up.

Furthermore, a first protrusion 8 and a second protrusion 9 are provided at positions moved from the monomer injection port 5 along the outer periphery of the cylindrical body 2 at an angle of 90 degrees.

The inner diameter of the cylindrical body 2 is the same as the outer diameter of the mold to be fitted into the gasket 1.
The end face of the mold can be held between the inner wall of the cylindrical body 2. The inner diameter of the ring-shaped protrusion 3 is sized to correspond to the outer diameter of the plastic lens, and the width (height direction) of the ring-shaped protrusion 3 varies depending on the prescription of the molded lens, and this width determines the peripheral thickness of the lens. is determined.

The gasket 1 is made of resin, and its material can be arbitrarily selected depending on the application, such as ethylene.
Examples include vinyl acetate copolymer, polyethylene, and polyethyl acrylate. Further, this gasket 1 can be molded by filling a mold cavity with resin using an injection molding method. In addition, the first protrusion 8 and the second protrusion 9 are used to control the astigmatism axis direction, lens layout, and gasket in the case of an astigmatic lens when injection molding the gasket 1, when molding a plastic lens using the gasket 1, respectively. This is an index that can be used to classify type names, etc.

FIG. 3 is a sectional view showing the state during molding of a plastic lens, and the effects of using the gasket of the present invention will be explained with reference to FIG. 3 and FIG. 2.

First, the lower mold 10 is attached to the gasket 1 so that the upper end surface of the lower mold 10 is in contact with the lower end surface 3a of the ring-shaped projection band 3 of the gasket 1.
mated to. Further, the upper mold 11 is fitted into the gasket 1 so that the lower end surface of the upper mold 11 is slightly spaced apart from the upper end surface 3b of the ring-shaped protrusion 3 (temporarily fixed). In this state, monomer is injected from the monomer injection port 5. After the monomer injected into the monomer injection port 5 reaches the recess 6 through the through hole 7, it overflows from the recess 6 and fills the cavity 12. Cavity 12
When the inside is filled with monomer, the upper mold 11
The upper mold 11 is pressed downward until the lower end surface of the ring-shaped projection 3 contacts the upper end surface 3b.

If the cavity 12 is filled with more monomer than necessary as a result of this operation, the excess monomer flows back through the recess 6, through hole 7, and monomer injection port 5 and is pushed out. At this time, air bubbles generated within the cavity 12 are also discharged. The injection amount of this monomer is automatically adjusted according to the power of the lens.

(Effects) As described above, according to the present invention, since the monomer injection port is formed upward on the side wall surface of the gasket, the monomer can be easily injected, and the monomer injection position can be easily detected, making it possible to automate the injection. Furthermore, air bubbles generated during monomer injection can be easily removed without being affected by changes in wall pressure due to lens power.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing one embodiment of the gasket of the present invention, Fig. 2 is a sectional view taken along the line A-A in Fig. 1, and Fig.
The figure is a sectional view showing the state when a plastic lens is molded using the gasket in Figure 1, and
The figure is a cross-sectional view showing conventional lens casting.
The figure is a perspective view showing conventional lens casting. DESCRIPTION OF SYMBOLS 1... Gasket, 2... Cylindrical body, 3... Ring-shaped protrusion band, 4... Side wall, 5... Monomer injection port, 6... Recessed part, 7... Through hole, 8... First protrusion part , 9... second protrusion, 10... lower mold,
11...Upper mold, 12...Cavity.

Claims (1)

[Scope of utility model registration request] The inner wall surface of the cylindrical body has a ring-shaped protrusion band along its circumferential direction, and the upper and lower end surfaces of this protrusion band can be brought into contact with the lower end surface of the upper mold and the upper end surface of the lower mold, respectively. The inner peripheral surface of the cylindrical body is formed to be able to hold the mold, and a recess extending from the upper end surface to the lower end surface is formed in a part of the ring-shaped protrusion band. A monomer inlet having an upward opening is formed on the outer circumferential wall side of the cylindrical body adjacent to the recess, and the bottom of the monomer inlet and the bottom of the recess are connected to the through hole formed in the cylindrical body. A plastic lens cast gasket characterized in that the gasket communicates with the plastic lens through the plastic lens.