MXPA98001068A - A provision to mold an ophthalmic lens plated in an assembly of mo - Google Patents

Abstract

Designs are described for base curve that are designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation, such that the HEMA ring with excess polymer is removed along with the base curve during the demoulding operation, the base curve mold designs promote and maintain adhesion of a HEMA ring with excess polymer to the base curve in a process for molding contact lenses cast in mold assemblies, each one comprising a front curve and a separate base curve, and because a molded lens is formed therebetween, in one embodiment, an annular area of the base curve mold adjacent to the HEMA ring with excess polymer is formed with marks machined with laser in the same, formed by laser machining a corresponding area in a mold, master used to cast the base curve molds, in a second mode, the annular area of the mold The base curve is formed with electrical discharge machine marks thereon, formed by electrical discharge machining of a corresponding annular area in a mold used to cast the base curve molds, in additional embodiments, the annular area of the curve mold base can be formed with projecting teeth projecting into the HEMA ring with excess polymer, with an annular step making contact with the HEMA ring with excess polymer, in addition, the annular step may include a plurality of teeth in projection around it, or you can define a lightning design or a mold cut design

Description

A PROVISION TO MOLD A LINTED LICENSE OFT LENS IN A MOLD ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides designs for base curve that are designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a stripping operation, such that the ring of HEMA in excess of polymer is removed along with the base curve during the demoulding operation. The present invention generally relates to base curve mold designs for maintaining adhesion of a HEMA ring with excess polymer to a base curve in a method for casting cast contact lens in mold assemblies, each comprising a front curve and a separate base curve, and wherein a molded lens is formed between them. The present invention relates generally to an arrangement for producing ophthalmic contact lenses in cast contact lens mold assemblies, and prepares the conditions for an improved removal of a HEMA ring with excess polymer with a base curve mold during a demoulding operation. The present invention is particularly well suited to molded ophthalmic lenses such as hydrogel contact lens, although it also has applicability to other small high-precision ophthalmic lenses such as intraocular lenses. 2. Discussion of the Prior Art As the ophthalmic lens industry has grown, and in particular the industry related to the supply of contact lenses that is provided for periodic frequent replacement, the number of contact lenses required to be produced has increased in number. drastic form. This has encouraged manufacturers to endeavor to use automated methods and devices that are adaptable to automated practices and consistent performance. It is generally known in the prior art to manufacture ophthalmic lenses, such as soft hydrogel contact lenses, by molding a monomer or a mixture of monomers in a mold such as one made from polystyrene or polypropylene. Examples of this prior art can be found in the Patents of E.U.A. 5,039,459, 4,889,664 and 4,565,348. These Patents describe the requirement for a polystyrene mold in which materials, chemistry and procedures are controlled in such a way that the mold portions do not require excessive force to separate when the lenses are glued together. The difference of the above polystyrene molds, another example is the use of polypropylene or polystyrene molds as described in the patent of E.U.A. No .. 4,121,896. The mold assembly for an ophthalmic contact lens typically includes a lower concave mold portion known as the front curve and a top convex mold portion known as the base curve. The concave surface of the lower front curve and the convex surface of the upper base curve define between them a mold cavity for a contact lens. A particular problem in the art is that the front curve and base curve molds are generally surrounded by a flange, and the monomer or monomer mixture is supplied in excess to the concave front curve mold prior to the assembly of the molds. As the molds are placed together, defining the lens and forming an edge, the excess monomer or monomer mixture is expelled from the mold cavity and rests on the flange of one or both of the mold portions or between them . Under polymerization, this excess material forms an annular ring around a mold assembly that resists the separation of the mold portions during a demolding operation. In such contact lens manufacturing processes, it is believed that defects such as chips and runoff as well as the absence of lenses occur, in part, due to difficulties in the demolding operation. In the demolding process, it is desirable that the HEMA ring with excess polymer remain adhered to the base curve to remove the HEMA ring with excess polymer with the base curve when the base curve is demoulded and removed, leaving only the contact lens cast on the front curve.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, a main object of the present invention is to provide designs for base curves that are designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation, such that the ring of HEMA with excess polymer is removed along with the base curve during the demoulding operation. A further object of the present invention is to provide an improved arrangement for producing cast contact lenses in mold assemblies in which the base curve molds can be easily and repeatedly separated from the front curve molds with the HEMA ring with excess of polymer adhered thereto and without damaging the lenses formed therebetween, thereby increasing the production of contact lenses without defects, and minimizing leakage of the lenses and breaking of the lens mold parts. The present invention basically describes and teaches the placement of a mechanical finish or mechanical aspect of the base curve, which helps to adhere the HEMA ring with excess polymer to the base curve, the finish or mechanical aspect is placed on the curve of base in the region in which the HEMA ring with excess polymer is normally formed. In accordance with the teachings herein given, the present invention provides an arrangement for molding an ophthalmic lens cast in a mold assembly, comprising a front curve mold having a center mold section for a lens with a surrounding flange, a corresponding base shape mold having a central lens mold section with a surrounding flange, and wherein a molded ophthalmic lens is formed between the front curve and base curve molds. A HEMA ring with excess polymer is formed around a central mold section during the molding process, and the base curve mold includes an annular area adjacent to the HEMA ring with excess polymer that is formed with an outline of surface to increase the surface area of the base curve mold in contact with the HEMA ring with excess polymer and geometrically increases the meniscus effect of the HEMA ring to raise the surface of the base curve. This increases the addition of the HEMA ring with excess polymer to the base curve mold in such a way that the HEMA ring with excess polymer is removed with the base curve mold during the demolding of the lens mold assembly. .

In greater detail, in one embodiment, the annular area of the base curve mold is formed with laser-machined marks thereon, formed by laser machining of a corresponding annular area in a master mold used to cast the molds of base curve. In a second embodiment, the annular area of the base curve mold is formed with electrical discharge machine marks therein, formed by electrical discharge machining of a corresponding annular area in a master mold used to cast the curve molds. base. In a further embodiment, the annular area of the base curve mold is formed with projecting teeth projecting into the interior of the HEMA ring with excess polymer. In an alternative embodiment, the annular area of the base curve mold is formed by an annular step which contacts the HEMA ring with excess polymer. However, the annular step may include a plurality of projecting teeth around it projecting into the HEMA ring with excess polymer. In alternative embodiments, the annular area of the base curve mold can define a step design or a mold cutting design.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages of the present invention for the base curve mold designs to maintain an adhesion of the HEMA ring to the base curve can be understood more easily by one skilled in the art if it refers to the following detailed description of the various preferred embodiments thereof, taken together with the accompanying drawings in which like elements are designated by identical reference numbers in all the different views, and in which: Figure 1 illustrates a rotal elevation view of a supporting pallet holding therein an arrangement of contact lens mold assemblies of 2 x 4, each of which consists of a lower front curve mold and an upper base curve mold, defining between them a mold cavity for a contact lens; Figure 2 is an enlarged side elevational view of a typical contact lens mold assembly of the prior art, illustrating construction details of the lower front curve mold and the upper base curve mold; Figure 3 is a schematic illustration of a mold assembly in which the base curve mold is laser machined to promote adhesion of a HEMA ring with excess polymer to the base curve during a demoulding operation; Figure 4 is a schematic illustration of a mold assembly in which the base curve mold is electric discharge machined (MDE) to promote adhesion of a HEMA ring with excess polymer to the MDE surface of the curve of base during a demoulding operation; Figure 5 is a schematic illustration of a mold assembly in which the base curve mold includes a shark tooth type design surface, to promote adhesion of a HEMA ring with excess polymer to the curve of base during a demoulding operation; Figure 6 is a schematic illustration of a mold assembly in which the base curve mold includes an annular step to promote adhesion of a ring HEMA with excess polymer to the base curve during a demoulding operation; Figure 7 illustrates a mold assembly similar to that illustrated in Figure 6, in which the annular step includes an annular ring of projecting teeth to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation; Figures 8 and 9 are respectively a bottom plan view of the base curve of Figure 7 and an enlarged view of a cross section taken along the arrows 9-9 in Figure 8; Figure 10 illustrates a mold assembly similar to that illustrated in Figures 7-9, wherein the annular step includes an annular ring of projecting teeth along the radial outer edge thereof to promote adhesion of a HEMA ring with excess polymer to the base curve during a demoulding operation; Figures 11 and 12 are respectively a bottom plan view of the base curve of Figure 10 and an enlarged view of a cross section taken along the arrows 12-12 in Figure 11; Figures 13-17 are respectively cross-sectional views more similar to Figures 9 and 12, of different modalities of a base curve surface designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation, and showing respectively a ray design, a tooth design, a mold cutting design, a laser design and an MDE design.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings in detail, particularly initially to Figures 1 and 2, Figure 1 illustrates a front elevation view of a support pallet 10 supporting thereon an arrangement, typically a 2 x 4 arrangement, of mold assemblies 12 for contact lenses, one of which is illustrated in more detail in Figure 2. Figure 2 is an enlarged side elevational view of a contact lens mold assembly 12 consisting of a lower front curve mold 14 and an upper base curve mold 16, which define therebetween a mold cavity for a contact lens 18. The base curve mold halves 14 and 16 are preferably formed from polystyrene but could be any suitable thermoplastic polymer that is sufficiently transparent to ultraviolet light to allow irradiation therethrough with light to promote the subsequent polymerization n of a white contact lens. A suitable thermoplastic such as polystyrene also has other desirable qualities such as being moldable to optical cavity surfaces at relatively low temperatures, having excellent flow characteristics and remaining amorphous during molding, without crystallizing, and having minimal shrinkage during cooling. The front curve mold half 14 defines a central curved section with a concave surface 20 of optical quality having a circumferential circular blade edge 22 extending around it. The blade edge 22 is normally desirable to form a sharp and uniform plastic radius dividing line (edge) for soft contact lenses 18 subsequently molded. A generally parallel convex surface 24 is separated from the concave surface 20, and an excessively very flat annular flange 26 forms extending radially outwardly from the surfaces 20 and 24. The concave surface 20 has the dimensions of the front curve (magnification curve). ) of a contact lens to be produced by the mold assembly, and is sufficiently smooth such that the surface of a contact lens formed by polymerization of a polymerizable composition in contact with the surface is optically acceptable. Half of the front curve mold is designed with a thickness, typically of 0.8 mm, and an effective stiffness for rapidly transmitting heat therethrough and for resisting leverage forces applied to separate the mold half from the mold assembly during a demoulding operation. The mold half 14 of the front curve further defines a generally triangular tongue 28, integral with the flange 26 projecting from one side of the flange. The tongue 28 is essentially uniplane and extends to a hot injection tip that supplies molten thermoplastic to form the front curve mold half. The front curve mold half 16 defines a central curved section with a convex surface 32 of optical quality, a concave surface 34 generally parallel, spaced from the convex surface 32, and an essentially unilateral annular flange 36 formed extending radially outwardly from the surfaces 32 and 34. The convex surface 32 has the dimensions of a posterior curve (resting on the cornea of the eye) in a contact lens to be produced by the mold half of the base curve, and is sufficiently smooth for the The surface of a contact lens formed by the polymerization of a polymerizable composition in contact with the surface is of optically acceptable quality. The half of the base curve mold is designed with a thickness typically of 0.6 mm, and effective stiffness to transmit heat therethrough, radially and to resist leverage forces applied to separate the mold half from the mold assembly during the demoulding. . The base curve mold half 16 also defines a generally triangular tongue 38, similar to the triangular tongue 28, integral with the flange projecting from one side of the flange. The tab 38 extends to a hot injection tip that supplies molten thermoplastic material to form the base curve mold half. During the process of molding a contact lens in prior art processes, an excessive amount of polymer or polymer mixture is initially deposited in a front curve mold, and then a base curve mold is placed on the mold of front curve and press against it. This results in the excess polymer in the mold cavity being displaced and discharged therefrom and an excess polymer ring 42 formed outside of the knife edge 22. The flanges 26 and 36 are designed to aid in demoulding and in the handling of the parts, and also protects the optical surfaces and the blade edge. The geometry of the triangular tabs 28 and 38 have a further function in directing and orienting the assembled front / curved base assembly 12 prior to demolding. When the front curve mold half or curve 14 is assembled with a base curve mold half or curve 16, a space 40 is formed between the two separate flanges and projection tabs that is important for demolding. The space between the tabs is preferably in the range of 1.0 mm-3.0 mm, and is required to assist in the demolding operation. Referring to Figures 1 and 2, the mold assemblies 12 for contact lenses are supported on the vane 10 with the annular flanges 26 and tabs 28 of the front curve mold 14 in depression slightly below the upper surface of the vane 10. The annular flanges 36 and tabs 38 of the base curve mold 16 are elevated above the upper surfaces of the vane, to allow a mechanical separation member to be inserted between the separate tabs 26, 36 of the front curve and base curve. Figure 3 is a schematic illustration of a mold assembly in which the base curve mole has a rough surface in an annular area 50 around it in which the HEMA with excess polymer is normally formed to promote adhesion of the ring with excess polymer to the base curve during a demoulding operation. The rough annular area 50 in the base curve mold is formed by laser machining of a rough annular area in a master metal mold which is used to cast the base curve molds. The rough annular area can be formed by means of one or more rings machined with laser in the master metal mold, formed by wear of metal in the rings by a laser beam that is scanned around it. Figure 4 is a schematic illustration of a mold assembly in which the master metal mold used to cast the base curve mold has been electro-machined (MDE) in an annular area 52 to promote adhesion of a ring of HEMA with excess polymer to the MDE surface of the base curve during a demoulding operation. Figure 5 is a schematic illustration of a mold assembly in which the base curve mold includes a "shark tooth 54" pattern on the surface in an annular area around it, to promote adhesion of a HEMA ring with excess polymer to the base curve during a demoulding operation. Figure 6 is a schematic illustration of a mold assembly in which the base curve mold includes an annular step 60 (having a cross section that approximates a triangle) formed around it to provide an annular surface area increased 62 over the base curve mold contacting the HEMA ring with excess polymer to promote adhesion of the HEMA ring with excess polymer to the base curve during the demolding operation. Figure 7 illustrates a mold assembly having an annular step 70 similar to that illustrated in Figure 6 where the annular step 70 includes annular projection-ring 72 to promote adhesion of a HEMA ring with excess polymer to the base curve during a demoulding operation. Figures 8 and 9 are respectively a bottom plan view of the annular step 70 on the base curve of Figure 7, and an enlarged cross-sectional view taken along the arrows 9-9 in Figure 8. In the Figure 9, the cross-sectional area 90 surrounding the tooth 72 can be seen as the HEMA ring with excess polymer formed around the projecting tooth. Figure 10 illustrates a mold assembly similar to that illustrated in Figures 7-9 where the annular ring of the projecting teeth 100 is displaced radially outwardly to the outer radial edge of the annular step 102 to promote adhesion of an annular ring. HEMA with excess polymer to the base curve during a demoulding operation. Figures 11 and 12 are respectively a bottom plan view of the base curve of Figure 10 and an enlarged view of a cross section taken along the arrows 12-12 in Figure 11. Again, in Figure 12, the cross-sectional area 120 surrounding the tooth 100 can be seen as the HEMA ring with excess polymer formed around the projecting tooth. Figures 13-17 are respectively cross-sectional view of different embodiments of a base curve surface designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation. In the embodiments of Figures 13-17, the cross-sectional areas can be contemplated as the HEMA ring with excess polymer. Each of these embodiments includes an annular step, similar to that of Figure 6 in which respectively a beam pattern 130, a tooth pattern 140, an edge cutting pattern 150, a laser machined design 160 and a laser pattern 160 are formed respectively. MDE 170 design. Although various embodiments and variations of the present invention are described in detail in order for the base curve mold designs to maintain HEMA ring adhesion to the base curve, it will be apparent that the description and teachings of the present invention will suggest many alternative designs to those skilled in the art.

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. - An arrangement for molding an ophthalmic lens cast in a mold assembly, comprising a front curve mold having a central section of lens mold with a surrounding flange, a corresponding base curve mold having a central section of mold lens with a surrounding flange, characterized in that a molded ophthalmic lens is formed between the front curve and base curve molds, and a HEMA ring with excess polymer is formed around the central mold section during the molding process, and the base curve mold includes an annular area adjacent to the HEMA ring with excess polymer that is formed with a surface contour to increase the surface area of the base curve mold in contact with the HEMA ring with excess polymer to increase the adhesion of the HEMA ring with excess polymer to the base curve mold in such a way that the HEMA ring with excess polymer is r excited with the base curve mold during the demolding of the lens mold assembly.

2. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold is formed with laser-machined marks thereon, formed by laser machining. a corresponding annular area in a master mold used to cast the base curve mold.

3. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold is formed with marks with electric discharge machine therein, formed by machined by electric discharge of a corresponding annular area in a master mold used to cast the base curve mold.

4. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold is formed with projecting teeth projecting towards the interior of the ring. HEMA with excess polymer.

5. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold is formed with an angular step that makes contact with the HEMA ring with excess polymer.

6. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular step includes a plurality of projecting teeth formed around the annular step projecting towards the interior of the ring HEMA with excess polymer.

7. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold defines a beam design.

8. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold defines a tooth design.

9. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold defines an edge cutting design.

10. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold defines a laser-machined design.

11. An arrangement for molding an ophthalmic lens cast in a mold assembly according to claim 1, further characterized in that the annular area of the base curve mold defines a design machined by electric discharge. SUMMARY OF THE INVENTION Designs are described for base curves that are designed to promote adhesion of a HEMA ring with excess polymer to the base curve during a demolding operation, such that the HEMA ring with excess polymer is removed along with the base curve during the demolding operation; the base curve mold designs promote and maintain adhesion of a HEMA ring with excess polymer to the base curve in a process for molding contact lenses cast into mold assemblies, each comprising a front curve and a curve of separate base, and because a molded lens is formed therebetween; in one embodiment, an annular area of the base curve mold adjacent to the HEMA ring with excess polymer is formed with laser-machined marks thereon, formed by laser machining a corresponding annular area in a master mold used for casting the molds of base curve; in a second embodiment, the annular area of the base curve mold is formed with electrical discharge machine marks thereon, formed by electrical discharge machining a corresponding annular area in a master mold used to cast the base curve molds; in additional embodiments, the annular area of the base curve mold can be formed with projecting teeth projecting into the HEMA ring with excess polymer, or with an annular step making contact with the HEMA ring with excess of polymer; In addition, the annular step may include a plurality of projecting teeth around it, or it may define a beam design or a mold cutting design. JJ / apm * amm * fac P98 / 115