MXPA01002084A - Automated cast mold hydrating device - Google Patents

Abstract

A method for processing a cured contact lens (11) wherein the contact lens is hydrated while retained in the mold cavity in which it was cast. The lens is released from the mold with cured excess lens material (61) remaining with the mold.

Description

AUTOMATIC HYDRATION DEVICE OF FOUNDRY MOLDS BACKGROUND OF THE INVENTION The present invention relates to a method of hydration and release of a contact lens from the section of the mold, in which it was molded. Soft contact lenses are produced by a number of methods including static casting, spin casting and combinations thereof. Two-part molds are commonly used in casting molding processes, while casting by rotation involves the use of an individual mold. In all cases, where the lens is cast in a mold, it is important to recover the lens without damaging it. As an example, U.S. Patent No. 5,271,875 discloses a method of molding by casting lenses in a mold assembly comprised of anterior and posterior sections of the mold. The method involves filling the previous mold with a monomer mixture, mounting the front and back sections, holding them together, hardening the monomer to form a lens, removing the mold sections, recovering the lens, and hydrating the lens to form a hydrogel lens. . This patent also discloses that it is advantageous to ensure that the lens is selectively retained on one of the sections of the mold. U.S. Patent No. 5,271,875 illustrates two general methods of lens recovery. In both methods one of the anterior and posterior sections of the mold is removed, the remaining lens remaining with the other section of the mold. First, in a "dry release" process, the lens is decoupled from the mold section, where it is retained by a force applied by a mechanical adapter. Second, in a "wet release" process, the lens is hydrated to facilitate its removal from the mold section in which it is held. More specifically, as the lens absorbs water, the hardened material of the lens expands sufficiently to uncouple it from this section of the mold. U.S. Patent No. 5,264,161 also discloses a "wet release" method of recovering a lens. In this method, a contact lens and the mold, in which it is retained, (preferably the lens being retained in both the anterior and posterior sections of the mold) is added to an aqueous bath, whereby the lens is hydrated and released from the lens. mold. U.S. Patent No. 5,264,161 further shows the advantage of adding a surfactant to this aqueous bath to facilitate the release of the lens. A drawback of dry release methods is that, unless proper adjustment and operation of the mechanical release device is maintained, there is a high probability that the lens will be damaged. One drawback of wet release methods is that they can not properly uncouple the lens from the surface of the mold, thus requiring manual handling or resulting in damage to the lens when attempting to remove the lens from the mold. In casting lens casting, it is common that in addition to the hardened lens, excess hardened lens material is produced. This results from the fact that the liquid mixture of excess monomer is expelled from the lens cavity in an overflow. This excess monomer is then hardened together with the lens. Finally, this excess hardened material has the shape of a ring, formed around the hardened lens. It is important that this excess hardened material of the lens be separated cleanly from the lens. In the wet release process, as described in U.S. Patent No. 5,264,161, by using an aqueous bath, where the excess material of the lens in is hydrated together with the lens, it is necessary to ensure that This excess hardened lens material does not adhere to the hydrated lens. This is a particular problem, since the lens and the excess lens material tend to adhere to each other when they are hydrated. This invention provides an improved process for the hydration and release of a contact lens from the mold in which it is retained, offering less chance of damaging the lens and ensuring that the lens is recovered separately from any excess hardened material. of the lens.

SUMMARY OF THE INVENTION The present invention relates to an automatic method of hydrating a contact lens, while in the mold in which it has been melted. The present invention relates to an improved method for the release of a contact lens from the mold in which it has been melted. The present invention further reduces or eliminates the incidence of excess hardened material of the lens, which is affixed to the lens as the lens is hydrated and released from the mold.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a cross-sectional view of the front and rear sections of the assembled mold of Figure 2. Figure 2 is a schematic ordered exploded view of a mold and contact lens assembly suitable for this invention . Figure 3 is a flowchart useful for explaining a lens hydration method in accordance with this invention. Figure 4 is a partially cross-sectional view of the solution distribution station for a single lens. Figure 5 is a partially cross-sectional view of an individual lens in the heating station. Figure 6 is a partially cross-sectional view of a hydrated lens in the heating station.

Figure 7 is a partially cross-sectional view of the hydrated lens as it is removed posteriorly from the mold; and Figure 8 is a partially cross-sectional view of the lens placed in the inspection tray.

DETAILED DESCRIPTION OF THE INVENTION Figures 1 and 2 illustrate sets of representative molds for the casting of contact lenses. The set includes an anterior section of the mold , which includes the surface 25 for forming the anterior surface 13 of the lens 11, and a posterior section of the mold 21, which includes the surface 28 for forming the rear surface 15 of the lens 11. The anterior mold 20 includes a cylindrical base 22, a conical head 24, a collar 50, a rim 52 and surface 25 defining the anterior cavity of the mold . The anterior reverse surface 56 of the mold generally follows the contours of the cylindrical base 22 and the reverse side 19 generally follows the surface defining the anterior cavity of the mold. The back mold 21 includes a cylindrical casing 26, an upper planar surface 27 and the inverse side 29 of the surface defining the back cavity of the mold. For the illustrated embodiment, the cylindrical housing portion 22 of the anterior section of the mold 20 is received in the cylindrical housing portion 26 of the rear section of the mold 21. However, it is understood that the invention is applicable to other assemblies. of mold and mold section configurations. Other examples of applicable casting methods include static casting and spin casting or other individual mold methods. The parts of the molds may be made from any material conventionally used to melt hydrophilic contact lenses, including plastic materials such as polyethylene, polypropylene, polystyrene and polyvinyl chloride. Figure 1 illustrates the rear section of the mold 21 mounted with respect to the front part of the mold 20, after the introduction of the monomer mixture forming the lens used to form the lens 11. More specifically, typically, a mixture that forms the lens is introduced onto the upper surface 25 of the anterior section of the mold 20, the rear section of the mold 21 is mounted with respect to the anterior section of the mold, and the mold sections are put completely together to assume the configuration shown in FIG. Figure 2. As seen in Figure 2, when the mold sections come together, the excess monomer mixture 61 is received and retained in the receptacle 59 located around the perimeter of the molding cavity formed between the surfaces 25, 28. After hardening of the monomer mixture forming the lens in the mold cavity 57 to form the lens 11, the back mold is removed leaving the lens 11 and the hardened material in excess of the lens in the receptacle 59 with the previous mold. (Although the illustrated embodiment shows a two-part mold assembly used to mold lenses by casting, a single anterior section of the mold should be used to retain the mixture that forms the lens in the case of casting the lens by means of casting by rotation). Figure 3 shows a flow chart explaining a method of hydrating the lens according to this invention. In the SI stage, the molded front and rear surfaces are disassembled. Since the hardened lens has greater affinity for the anterior mold 21, the cured lens 11 as well as the excess material of the lens 61 remains with the anterior mold.

As previously indicated, lenses can be formed by other methods, such as individual mold methods, where the lens remains in the mold. Starting with the stage S2, the anterior mold with the lens is placed on an automatic conveyor belt that moves it through a series of stations. In the first station, the lens is filled with a moisturizing solution. In step S3, the next station, the lens is exposed to a thermal source. This occurs during a period of time in which the conveyor belt is slowly synchronized, keeping the lens at a certain distance from the thermal source. Steps S4 and S5 take place in the third station. The lens is then transported to the inspection tray of step S6 which is located in the fourth station. The following description of Figs. 4-8 will further detail the method depicted in Fig. 3. Fig. 4, which illustrates step S2, shows a detail of the cross section of the station distributing the solution of this invention, where the lens 11 is now retained, together with the excess material of the lens, on the anterior mold 20. For the illustrated embodiment, the anterior mold 20 is supported on and is positively driven by an automatic conveyor 30 by placing the mold on the support pin 32 of the mold. The pin 32 rests securely on the hub 31 which is fixed to the belt 30. The pin 32 is slightly narrower than the inner diameter of the mold and has the upper surface 34 which is concave. This allows the mold to fit closely on the pin and have a slight oscillating movement when it comes into contact with the lower surface 19 of the mold. Alternatively, the pin 32 can be configured to contain a tip on the upper surface. It will be appreciated that other mechanisms for transporting the mold / lens assemblies are within the scope of the invention. In a first station located along the conveyor 30, a predetermined quantity of hydration fluid 5 is distributed over the concave surface of the contact lens by the injection pump 35. Ideally, the amount of hydrating fluid distributed by the pump 35 in station 1 is such that the meniscus of the solution greatly exceeds the flange 52 of the anterior mold, ie, excess fluid will not spill into the receptacle 59. Although a smaller amount of fluid may flow into the receptacle 59 , it is intended to prevent a sufficient quantity of fluid from flowing into the receptacle 59, whereby the ring of the excess material 61 of the lens would be completely hydrated together with the lens 11. On the other hand, the hydration fluid should completely cover the lens 11 including its edge, so that the edge of the lens is completely hydrated to avoid the likelihood that the edge of the lens will continue to adhere to the lens. surface of the mold. Accordingly, several drops of the moisturizing fluid are distributed in the center of the non-hydrated lens retained in the mold 20, such that a meniscus is formed that covers just the edge of the lens but does not invade the area of the receptacle. Hydration fluids may be fluids conventionally used for the hydration of soft hydrogel contact lenses, including water or saline, optionally including a surfactant such as Tween-80 surfactant. Step S3 starts with Figure 5 and ends with Figure 6. The previous mold with the lens 11 is transported along the conveyor 30 to a second downstream station, as shown in Figure 5. In this station, the Hydrated lens is exposed to thermal source 36. Any suitable heat generation system, such as a microwave source, can be used, however the preferred heat source is an infrared panel. As an example, in the case where the lenses are formed of poling (a crosslinked copolymer formed mainly of 2-hydroxyethyl methacrylate), the lenses are exposed to the infrared light source for about 7 to 25 minutes, the infrared lamp being located at about 3 inches from the upper part of the previous mold. The heat from this lamp carries the hydration fluid to a suitable temperature to hydrate the lens. The main purpose of the thermal source is to accelerate the hydration of the lens. Although the lens would eventually hydrate at room temperature when immersed in the hydration fluid, the application of heat to the lens and to the hydration fluid accelerates the hydration of the lens. A suitable temperature for the hydration fluid used to hydrate a pollination lens is 145 ° +/- 20 ° F. Accordingly, the thermal source and its position are selected in such a way that the hydration of the lens is completed before the lens 11 and the mold reach the next station on the conveyor 30. On the other hand, if the fluid temperature of the Hydration becomes too high or if the lens is exposed to heat for a very long time, evaporation will occur leaving the lens dehydrated. If the excess material 61 of the lens has been partially hydrated, it is during the heating process when the material will dry and may adhere to the mold. The anterior mold 20 with the lens 21 is then synchronized along the conveyor 30 to a third station, downstream of the heating station, as seen in figure 6. At the moment in which the lens and the mold reach this station, the lens has been hydrated and separated from the previous mold. At this point, the edges of the lens 11 have been gently pushed out from the anterior surface of the mold 25. The hydrated lens has further increased in size and no longer fits in the mold cavity. The ring of the excess hardened material 61 of the lens remains in the receptacle 59 preferably dehydrated and adhered to the mold 20. In this station at S4, the collar 50 is indexed under the retaining plate of the fixed mold 63 and the nozzle element 71 as shown in Figure 7. The nozzle element 71 includes a body portion 72 and a head portion 73. In the preferred embodiment, the head portion of the nozzle 71 has a section that has been cut. The surface 74 formed at the end of the head portion has a partial peripheral surface. This helps to remove the lens from the previous mold. The vacuum source 81, connected to the central passage 82, extends through the body portion and connects with the passage of the nozzle head 83. The passage of the nozzle head 83 forms the opening 75 in the surface 74 of the nozzle head. The surface 74 is generally spherical to conform to the back surface 15 of the lens 11 and to the surface 25 defining the anterior cavity of the mold. The screen 84 is placed in the opening 75. Accordingly, the nozzle 71 is lowered towards the anterior mold until it comes into contact with the surface 15 of the hydrated lens 11. As the nozzle 71 is lowered, a vacuum through the tube 81. The vacuum source sucks through the central passage 82 and the passage of the head of the nozzle 83. As the head portion of the nozzle 73 comes into contact with the hydration solution 5. , the solution is pushed upwards inside the nozzle passages into the vacuum. The surface 74 of the nozzle head then comes into contact with the surface of the lens 15. The surface of the head of the nozzle is itself aligned with the curvature of the surface 25 of the mold cavity, which can cause the mold 20 oscillates slightly on the pin 32. This allows the head of the nozzle to center on the surface of the lens 15. Since the vacuum of the head of the nozzle 73 begins to push on the lens 11, the oscillating movement of the mold 20 adds friction further assisting the evacuation of the lens 11. The screen 84 is included in the opening of the nozzle head 75, only allowing the hydration fluid to be evacuated through the passage 83, while leaving the lens fixed to the screen 84. The screen 84 prevents the hydrated lens from being inadvertently withdrawn from the vacuum source 81. The nozzle element 81 and the screen 84 are preferably made of materials that will not damage the lenses during this acquisition and placement operation. The nozzle member 71 is then raised while maintaining the vacuum through the passages 82 and 83 to lift the lens from the mold as shown in Figure 7. Preferably, the nozzle 71 is raised relatively slowly to allow the lens is detached from the mold, the weight of the mold contributing to its separation. It should be noted that in some cases, the lens can not be completely uncoupled from the mold, that is, the weight of the mold does not facilitate complete separation of the lens from the mold, so the mold is raised together with the lens when the lens is raised. nozzle assembly. In such cases, the mold contacts the retaining plate 63 of the fixed mold which serves to uncouple the mold from the lens and the mold falls back onto the pin 32, or is discarded by the conveyor belt. The nozzle carrying the lens 11 is then moved to a station longitudinally of the conveyor, as shown in Figure 8 (S6). In this station, the lens is released from the nozzle assembly in the lens holder 91. For the illustrated embodiment, the holder 91 is a tray that includes the cavity 93 for holding and transporting the lenses for further processing. However, the support can have other configurations depending on the desired manufacturing sequence, for example, the nozzle 71 can deposit the lens directly in a contact lens bubble pack in this step. In any case, after the lens is placed above the cavity 93, a switching valve (not shown) changes the vacuum in the central passage 82 and the head passage 83 of the nozzle 71 to a positive air pressure low. For the illustrated embodiment, the cavity 93 of the support 91 includes a fluid such as water or aqueous solution. While the nozzle assembly transfers the lens to the support 91, the mold 20, which now lacks a lens, but still includes the ring of excess lens material 61, is further synchronized along the conveyor 30, up to that reaches a waste station (not shown). In this station, the mold with the material ring 61 is discarded; any hydration fluid that remains in the mold can be discarded or, if desired, recovered and circulated through the filters for recycling. It has been found that a range of lenses of different magnification corrections can be hydrated using the apparatus and method described. The lenses were constantly removed from the mold without damage, and the annular ring of the excess lens material remained constantly fixed to the mold. The foregoing has been provided so that the nature of the invention can be easily understood. However, it should be evident that modifications of the foregoing embodiments can be made without departing from the nature and scope of the invention. For example, it is possible to provide the formed non-hydrated lens in an individual mold process, ie spin casting, lathe cutting and casting and lathe combinations. Therefore, the invention is applicable to other processes that melt a contact lens in a xerogel state and involve the hydration and release of the lens of a mold. Additionally, the invention can be applied to other foundry processes involving molds with configurations other than those described for the illustrated embodiment. Accordingly, the scope of the invention should not be limited to the specific described above, but should instead be measured with respect to the appended claims.

Claims (14)

Claims

1. A method of hydrating a hardened lens retained in the mold cavity, in which it has been melted, said mold containing a receptacle of excess lens material adjacent said mold cavity, comprising: hydrating the lens while the lens is retained in the mold, while avoiding complete hydration of the hardened material in excess of the lens, which is retained in the mold; and removing the hydrated lens from said mold, the excess material remaining from the lens in the mold. The method of claim 1, wherein the liquid is distributed over the lens while the lens is retained in the mold. 3. The method of claim 2, wherein after the distribution of liquid over the lens retained in the mold, the lens and the liquid are exposed to a source of heat. The method of claim 3, wherein the liquid is liquid distributed over the lens retained in the mold in a first station along a conveyor, and the lens and the mold are synchronized to a second station along the conveyor for exposure to the thermal source. The method of claim 3, wherein said thermal source comprises an infrared light source. 6. The method of claim 2, wherein said liquid is selected from water or an aqueous solution. The method of claim 1, wherein the hydrated lens is removed from the mold with a nozzle assembly including a head portion for contacting the hydrated lens, and a extending through a body of the assembly of nozzle, said central passage being connected to a vacuum source. The method of claim 6, wherein the nozzle assembly deposits the lens in a receptacle of a lens holder. The method of claim 7, wherein the passage of the nozzle assembly is also fixed to a source of pressurized air, said nozzle assembly including a valve that deactivates the vacuum source and activates the source of pressurized air to deposit the lens . A lens molding method comprising: hardening the polymerizable lens material to form a lens in a mold cavity formed between a first mold, having a first lens molding surface and a second mold having a surface of opposite lens molding, wherein the excess polymerizable lens material is received and hardened in a space adjacent to an edge of the mold cavity; removing the second section of the mold so that the hardened lens and the excess material of the lens remain on the first mold; place a liquid on the hardened lens and hydrate the lens; and removing the lens from the first mold, whereby the excess hardened material of the lens is not completely hydrated and remains in the first mold. The method of claim 10, wherein the lens including the distributed liquid is subjected to a thermal source before removing the lens from the first mold. 1

2. A method of hydrating a hardened lens retained in the mold cavity in which it has been melted, said mold containing the receptacle of excess hardened material of the lens adjacent said mold cavity, comprising: distributing the liquid over the lens while the lens is retained in the mold, and exposing the lens and liquid to a heat source, thereby hydrating the lens and decoupling the lens from the mold; and removing the hydrated lens from said mold, the excess material remaining from the lens with the mold. The method of claim 12, wherein the excess hardened material of the lens is not completely hydrated. The method of claim 12, wherein said heat source comprises an infrared light source.