MXPA97006295A - Multiple optic curve molds formed in a polim solid piece - Google Patents

Abstract

An injection molding process for molding an assembly of front curve molds into a plurality of unitary solid pieces of polymer, wherein a plurality of front curve molds are arranged symmetrically around a single central polymer injection gate; In this arrangement, the molten polymer flows radially out of the same uniformly in all directions towards the four front curves to form a common polymer molded part, in a compression injection molding process, the pressure on the molten polymer is maintained relatively constant, and the mold is mechanically crushed during the molding operation, the present invention molds a front curve mold cabinet in a manner in which there is a significant reduction of residual stress enclosed in the resulting assembly of front curve molds; this causes a significant reduction in the camber and co ntracción of each mold of frontal curve, that is not subjected to stress, and gives as a subsequent casting of ophthalmic lenses that are not subjected to stresses, in addition, the assembly of front curve molds can work as its own support pallet for purposes of placement and alignment of product during subsequent production operations

Description

MULTIPLE MOLDS OF OPTICAL CURVE FORMED IN A SOLID PILE OF POLYMER FIELD OF THE INVENTION The present invention relates generally to a multiple assembly of optical curve molds formed in a solid single piece of polymer, and more particularly belongs to a multiple assembly of front curve molds formed in a single solid piece of polymer; the front curve mold assembly is used in a subsequent production process for casting ophthalmic lenses in mold assemblies, each comprising a front curve and a separate base curve, and in which molded lenses are formed between them « ales as a contact lens.

BACKGROUND OF THE INVENTION As the ophthalmic lens industry has grown, and in particular the industry related to the supply of contact lenses provided for frequent periodic replacement, the number of contact lenses that are required to be produced has increased dramatically. This has encouraged manufacturers to look for automatic methods and devices adaptable to automatic practices and consistent performance.

In the prior art it is generally known to make ophthalmic lenses, such as soft hydrogel contact lenses, by molding a monomer and monomer mixtures in a mold such as one made of polyethylene or polypropylene. Examples of this prior art can be found in the U.S. patents. Nos. 5,039,459, 4,889,664 and 4,565,348. These patents discuss the requirement of a polyethylene mold in which the materials, chemistry and procedures are wrapped in such a way that the mole portions do not require undue force to detach by adhesion to the lenses or from one another . In contrast to the previous polyethylene molds, another example is the use of polypropylene or polyethylene molds described in the U.S. Patent. No. 4, 121,896. The assembly of molds for molding an ophthalmic contact lens typically includes a concave portion of lower rnolde, referred to as a front curve and a convex upper mold portion, referred to as a 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.

BRIEF DESCRIPTION OF THE INVENTION Therefore, a main object of the present invention is to provide a multiple assembly of optical curve molds formed in a solid piece of polymer in which the assembly of optical curve molds is used in a subsequent production process for molding lenses Of the cast optics in roller assemblies, each comprises a front curve and a separate base curve, and wherein molded lenses such as contact lenses are formed therebetween. The present invention relates to an injection molding process for molding an assembly of a plurality of front curve molds into a solid unitary piece of polymer in which four front curve molds are arranged symmetrically around a single central injection gate. of polymer. In this arrangement, the molten polymer, plastic molten mixture, flows radially outwardly therefrom relatively evenly in all directions toward the four frontal curves to clamp a polymer-molded part. In a compression injection molding process, the pressure on the molten polymer is kept relatively constant and the mold is mechanically crushed during the molding operation. According to the teachings of the present invention, the molten polymer flows through the orifice of the injection gate to flow to the mold assembly and fill it, in a uniform, consistent, laminar manner, which results in the shear stress it is within acceptable limits to provide uniformly curved and non-curving optical curve molds having uniform physical characteristics and acceptable optical properties. The present invention molds an assembly of front curve molds in a manner in which there is a significant reduction of residual stress enclosed in the resulting assembly of front curve molds. This results in a significant reduction in the camber and contraction of each front curve mold, which is not optically subjected to stress and thus results in a subsequent casting of ophthalmic lenses that are not optically subjected to stress. In addition, the assembly of the front curve molds can function as your own support pallet for purposes of alignment and product placement during subsequent production operations. This eliminates a production requirement for the support vanes to position and align the separate front curve molds, since each separate front curve mold is positioned and aligned precisely by means of the front curve mold assembly. This results in a significant reduction in the complexity of the product's handling requirements in production operations. A preferred embodiment of the present invention molds an assembly of front curve molds, however, the present invention is also capable of molding an assembly of base curve molds into a solid single piece of polymer in an alternative embodiment. The present invention relates to the injection molding of a curve of generally round shape with somewhat normal processing parameters. The design of the present invention eliminates the problems encountered with the prior art designs in the areas of stress, differential contraction (soccer effect), assembly, uniformity between lenses and parts, and cost. The design of the present invention provides a central polymer injection gate, and four lens molds located symmetrically around it. The molded part can be designed with dimensions that match those of the existing parts, and therefore an existing hydration and operation unit can remain unchanged in the present production line. In accordance with the teachings of this, e >This invention provides an injection molding process for molding an assembly of a plurality of optical curve molds into a single unitary solid piece of polymer in which an assembly mold defines a plurality of optical curve molds arranged symmetrically about a single central polymer injection gate. In this arrangement, the molten polymer flows substantially uniformly radially to and outward thereof in all directions towards the plurality of optical curve molds to form a common polymer molded part, formed within the assembly mold. This results in a significant reduction in the amount of residual stress enclosed in each optical curve node, and a significant reduction in shrinkage and warpage of each optical curve mold, and results in a subsequent casting of ophthalmic lenses that are not optically subjected. to effort. In greater detail, the assembly mold preferably includes four optical curve molds located siretically around the central polymer injection gate. During the compression injection molding operation, the pressure on the molten polymer remains relatively constant, and the assembly olde is mechanically crushed to cause a volumetric shrinkage in the assembly rnolde. In addition, the optical curve mold assembly can operate with its own support paddle for product placement and alignment purposes during subsequent production operations, thereby eliminating a production requirement for support pallet to place and align separate optical curve molds, since each separate optical curve model is positioned and aligned precisely by means of the assembly of optical curve molds. A preferred embodiment of the present invention molds an assembly of front curve molds, however, the present invention is equally capable of molding an assembly of base curve molds into a single solid piece of polymer in an alternative embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages of the present invention for a multiple assembly of optical curve molds formed in a single solid piece of polymer, can be easily understood by the person skilled in the art with reference to the following detailed description of a preferred embodiment. thereof, taken in conjunction with the accompanying drawings in which like elements are designated by identical reference numerals in all different views, and in which: Figure 1 is a top plan view of a single solid piece of molded polymer which is molded according to the teachings of the present invention in a compression molding process in which two groups of four frontal curves are each symmetrically molded around a central polymer injection gate; Figure 2 is a side elevational view of the molded polymer front curve mold assembly of the fi ber 1; Figure 3 is a flow diagram of the process illustrating the main steps of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to injection molding of curves of generally round shape with somewhat normal treatment parameters, and eliminates problems with the prior art designs in the areas of stress, differential contraction (soccer effect), assembly, uniformity between lenses and parts, and cost. More particularly, the present invention relates to a compression injection molding process for molding an assembly of a multiple number of front curve molds into a single solid piece of polymer. Four front curve molds are arranged symmetrically around a single central polymer injection gate (Table 1, Figure 3) and the molten plastic polymer flows radially outward to the four surrounding front curve molds (Table 2, Figure 3) to form a single unitary molded piece with polymer (Table 1, Figure 3). In said compression injection molding process, the pressure on the molten polymer is kept relatively constant (Table 2A, Figure 3), and the mold is mechanically crushed during the molding operation (Table 2B, Figure 3), as is generally known in the art. Referring to the drawings in detail, the Figure 1 is a top plan view, and Figure 2 is a lattice elevation view of a single solid piece of molded polymer 10 forming a front curve mold assembly, molded according to the teachings of the present invention in an injection molding process by understanding. In the embodiment of Figures 1 and 2, a first group of four front curve molds 12 is symmetrically molded around a first central polymer injection gate located at 14, and a second group of four front curve molds 16. they are also symmetrically molded around a second central polymer injection gate in 18. Each front mold curved 12 or 16 defines an inner concave surface 20, Figure 2, which when the front curve rnolde is assembled with a rnolde of the corresponding base curve, forms the front surface of molded contact lenses between the assembly of the front curved and base curve molds. The assembly 10 includes a plurality of four descendingly suspended front and rear ends 22, two descendingly suspended lateral ends 24, and a descendingly suspended central end 26, provided to hold the assembly on a flat surface. However, it should be understood that the assembly 10 in this its simplest form can take almost any circular shape, with or without supporting limbs, although the supporting limbs are normally required in some way.

In different embodiments, the multitude of front curve molds can include any convenient number of front curve molds arranged symmetrically around the central polymer injection gate. The present invention molds an assembly of front curve molds in a manner in which there is a significant reduction in the amount of residual stress enclosed in each front curve mold. This results in a significant reduction in warping and contraction of each frontal curve pattern, which is not optically subjected to stress, and thus results in a subsequent casting of ophthalmic lenses that are not optically subjected to stress. In addition, the front curve mold assembly can function as its own support pallet for placement and product alignment purposes during subsequent production processes (Table 4, Figure 3). This eliminates a production requirement for paddle pads for positioning and aligning the separate front bend molds, since each separate front bend mold is positioned and aligned precisely by the assembly of front curve molds. This causes a significant reduction in the complexity of the product handling requirements of the production process. In addition, the molded part can be designed with dimensions to occupy exactly the same amount of space as the existing parts, and therefore, with the adoption of a front curve mold assembly in the present contact lens production line, no There is a need to change the existing hydration unit and the procedures in the current production line. A series of 13 sequential time measurements were taken during injection molding by understanding an assembly of four front curves molded in a single piece of polymer, similar to that illustrated in one half of Figures 1 and 2, on time measurements nodal to nodal, nodal to nodal pressure measurements, nodal to nodal temperature measurements, and element shear measurements for 13 sequential time measurements. The measurements and analysis showed that the conditions are very good for the process of the present invention. Although various embodiments and variations of the present invention have been described in detail for a multiple assembly of optical curve molds formed into a solid piece of polymer, it is evident that the description and teachings of the present invention will suggest many alternative designs to those skilled in the art. The matter.

Claims (10)

NOVELTY OF THE INVENTION CLAIMS

1. - An injection molding process for molding an assembly of a plurality of optical curve molds into a unitary solid piece of polymer, comprising symmetrically arranging a plurality of optical curve molds around a single central polymer injection gate in an assembly mold, causing the molten polymer to radially flow therefrom through the assembly rim towards the plurality of optical curve molds to form a common polymer molded part, which results in a significant reduction in the amount of residual stress enclosed in each optical curve mold, and a significant reduction in the camber and contraction of each optical curve mold, and as a result results in a subsequent casting of ophthalmic lenses that are not optically shattered to the force.

2. An injection molding process according to claim 1, further characterized in that it comprises a compression injection molding process during which the pressure on the molten polymer remains relatively constant, and the assembly mold is mechanically crushed. to cause a volumetric contraction of the assembly mold during the molding operation.

3. An injection molding process according to claim 2, further characterized in that the assembly of optical curve molds functions as their own support pallet for purposes of placement and alignment of product during subsequent production operations, thus eliminating a production requirement for support vanes to position and align separate optical curve molds, since each optical curve mold is precisely positioned and aligned by the assembly of optical curve molds.

4. An injection molding process according to claim 3, further characterized in that it comprises a method for molding an assembly of optical front curved molds into a single unitary solid piece of polymer.

5. An injection molding process according to claim 3, further characterized in that it comprises a method for molding an assembly of base curve molds into a single unitary solid piece of polymer.

6. An injection molding process according to claim 3, further characterized in that the mold of the assembly includes four optical curve molds located symmetrically around the central polymer injection gate.

7. - An injection molding process according to claim 1, further characterized in that the assembly of optical curve molds functions as their own support pallet for purposes of positioning and alignment of product during subsequent production operations, thereby eliminating A production requirement for support vanes for placing and aligning separate optical curve molds, since each optical curve mold is precisely positioned and aligned by the assembly of optical curve molds.

8. An injection molding process according to claim 1, further characterized in that it comprises a method for molding an assembly of front curve olds into a single solid piece of polymer.

9. An injection molding process according to claim 1, further characterized in that it comprises a method for molding an assembly of base curve molds into a single unitary solid piece of polymer.

10. An injection molding process according to claim 1, further characterized in that the mold of the assembly includes four optical curve molds located symmetrically around the central polymer injection gate.