HK1032560B - Mold and molding machine for making ophthalmic devices - Google Patents

Description

Mold and molding machine for manufacturing ophthalmic devices

Technical Field

The present invention relates to a mold and/or molding machine for manufacturing ophthalmic devices. More particularly, the present invention relates to a mold and/or molding machine for manufacturing an apparatus having a finished product holding unit.

Background

The entire disclosure of Martin et al, U.S. patent No. 5,702,735, which is incorporated herein by reference, provides an apparatus for molding a polystyrene lens curve, either a front curve or a back curve, for subsequent molding of soft contact lenses. The apparatus is designed to provide excellent thermal conductivity to minimize molding cycle time while producing uniformly accurate and correct optical quality surfaces. Molten polystyrene is supplied to a plurality of mold cavities via a hot runner system. In a mold for making a front curve, the convex surface of the mold provides an optical quality surface to the concave surface of the front curve created thereby. The structural elements defining each convex surface include a hollow cylindrical sleeve and a removable power insert mounted therein which can be replaced to allow variation in the prescribed strength of the contact lens to be formed from the lens curve. In a first embodiment, the power insert includes only a convex surface on its operative end. In a second embodiment, the power insert includes an annular flat surface surrounding the convex surface, the junction between which defines a discontinuous curvature to impart a sharp edge to the front curve formed thereby. During the molding process, cooling water is pumped into the core of the insert to cool the insert, which complicates the process of replacing the insert. The power insert may be constructed of a variety of materials including pure steel, brass, copper chromium alloy, cobalt nickel alloy martensitic steel. The power insert may be coated with a surface layer of nickel phosphide or silicon oxide or chromium nitride. These layers may be formed to their appropriate thickness and size using a diamond cutter, and may be heat hardened.

U.S. patent No. 4,565,348 to Larsen, also incorporated by reference herein, discloses another conventional method of manufacturing lens curvatures. According to this patent, the lens curve is molded in a set of eight lens curves carried on a frame in a 2 x 4 array. Fig. 3 of the Larsen patent shows a mold frame carrying a 2 x 4 array of concave front curve elements, while fig. 5 shows a mold frame carrying a 2 x 4 array of back curve elements. The assembly of the frame and lens curve element in groups is made in one piece by injection molding the assembly, wherein the lens curve element is fixed in an outer rectangular frame by small struts extending between the outer rectangular frame and the lens curve element. The height of the frame is such that during handling the surface of the lens curve is protected from scratches and mechanical damage and the frame has approximately a shape that is easy to stack and handle. This conventional method of molding polystyrene lens curves in a set of parts typically takes about 24 seconds, which is still too long for efficient production of polystyrene lens curves.

In this conventional method, complementary sets of anterior and posterior curved surfaces are used in the production of hydrogel contact lenses by molding a reaction mixture; wherein the mixture is preferably dissolved in a non-aqueous water-displaceable solvent. After a dosing step, in which the front curve is substantially filled with the reaction mixture, the back curve is overlaid on the concave front curve in such a way that no air bubbles are trapped underneath the back curve. The back-curved piece is placed as an individual unit on the polymerizable mixture in the front-curved piece; thus, prior to this step, the back curve piece is torn or cut too often to separate it from its frame. When the back curve element is separated from the frame, it is preferably supported by a mechanism which places the back curve element on the front curve element. The reaction mixture is then conditioned for polymerization, such as by irradiation with actinic visible or ultraviolet radiant energy to thereby produce a polymer having the desired hydrogel lens shape. After completion of the polymerization process, the two lens curves are separated (referred to as demolding); the contact lens is typically left in the front curve and subsequently removed from the front curve. Typically, the anterior and posterior curved members are used only once to mold a single contact lens. After completion of the polymerization, the diluent was replaced with water to produce an aqueous lens.

U.S. patent No. 5,782,460 and WO 98/42497 disclose a method of manufacturing hydrogel contact lenses by molding a material that has been polymerized but is at least partially non-crosslinked in a reusable mold. Crosslinking of the polymer is achieved by ultraviolet radiation; thus, the mold is constructed of a material that is transparent to ultraviolet light, such as quartz or a polymeric material. One or more contact lenses may be molded in each mold tool.

Kok et al, U.S. patent No. 5,451,155, the entire contents of which are also incorporated herein by reference, discloses an apparatus for manufacturing articles such as compact discs using injection molding, which provides a vertical injection molding machine including two supports for supporting mold plates. The two templates are adjustable relative to each other between a first position and a second position; in the first position, the mold plate defines a cavity into which material is injected by the injection molding machine during operation to form a particular molded article; in the second position, the templates have been moved apart by a distance while the molded article has been removed. On each side of the injection-moulding machine, transport means are provided which move the support and the mould from a position at a distance from the injection-moulding machine to a position suitable for cooperation with the injection-moulding machine. The transport device and the support member are detachably coupled. The patent also discloses that a support member can provide a new template at a distance from the machine while the machine is in operation. To replace the template and supports it is only necessary to remove the supports supporting the template that is currently used and move the new supports and template into position. This form of changing the mold plates provides for quick and simple tool changes while minimizing the time that the machine of the injection molding operation is out of production.

There is a need in the art for improvements in molds and molding techniques for making ophthalmic devices, and in particular for improving molds and molding techniques for making ophthalmic devices having finished retention units. By "finished product holding unit" is meant different devices, such as different products. For example, contact lenses having different optical powers and/or cylinder and/or axis values (axis values), each combination of these will represent a different finished holding unit, each finished holding unit being manufactured using a different mold or different mold orientations or different reaction mixtures within the mold.

The present invention provides a mold for forming an ophthalmic device, comprising:

a first mold half that cooperates with a second mold half, wherein said second mold half comprises an insert and said first mold half comprises a base, attachment means by which said cassette is removably attached to said molding base, and at least one replaceable cassette comprising a surface that is not in contact with said molding base and insert, wherein said attachment means is accessible on said surface of said replaceable cassette but does not contact said base, and wherein said insert in said at least one replaceable cassette comprises an optical quality surface.

The molds can be used to make ophthalmic devices; however, the mold is preferably used in an automated molding machine, and more preferably in an injection molding machine. The invention is preferably used to manufacture curved lens elements which will be used to manufacture contact lenses.

The present invention further provides a vertical injection molding machine comprising a mold having at least one cassette, wherein the machine can quickly change from one mold half to another, and wherein the machine has the capability of manufacturing ophthalmic devices.

The present invention additionally provides a mold wherein two ophthalmic devices of different optical qualities are manufactured in a single mold.

The molds of the invention allow for rapid changes in the optical characteristics of ophthalmic devices produced using the molds of the invention. The mold includes one or more cassettes that enable rapid cartridge change, thereby efficiently using one or a small number of mold halves containing replaceable cassettes to manufacture ophthalmic devices having a plurality of product holding units. These molds are particularly well suited for the direct or indirect production of contact lenses having a variety of spherical, aspherical or multifocal powers.

It is therefore a primary object of the present invention to provide an improved mold comprising a first mold half and a second mold half, wherein the first mold half comprises at least one replaceable cassette comprising a plurality of inserts for forming ophthalmic devices. The first and second mold halves being adjustable relative to each other between a first position and a second position; in the first position, the mold halves form a mold cavity to allow material to be introduced into the mold cavity to form a molded ophthalmic device; and in the second position, the mold halves are separated by a distance, preferably while providing a mechanism to remove the molded ophthalmic device.

An embodiment of the present invention provides a mold half comprising one or more replaceable cassettes with non-directly cooled inserts; thereby making it easier to remove and interchange cassettes.

Another embodiment of the present invention improves removal of a molded ophthalmic device from a mold by providing an air injection system. In contrast to the prior art using ejector pins, the air jet does not distort the ophthalmic device and, when the molded ophthalmic device is at a higher temperature, for the preferred embodiment, the air jet is available.

Another embodiment of the present invention provides a mold that allows one or more cassettes and/or mold halves containing the cassettes to be replaced for use with different ophthalmic devices, i.e., different product holding units. In preferred applications, the ophthalmic devices formed using the molds are front curve pieces and back curve pieces used to make contact lenses. The front and back curve pieces are preferably molded in a "family series mold" configuration, meaning that the mold halves include complementary inserts to form the front curve piece and the back curve piece (male protrusion and female recess). The mold halves preferably include one cassette having an insert for the front curve and another cassette having an insert for the back curve. In this embodiment, only one mold half needs to be changed to change the front curve and back curve, or a cassette on the mold half can be changed to change the front curve or back curve provided by the mold. Changing a mold half or changing a cassette changes the front curve and/or back curve and results in a lens with different finished retention units produced using the front curve and back curve. This arrangement is possible because only one surface of the front and back curve elements has an optically critical side, whereas the other side is not. Thus, if the optically critical sides of the lens curve are formed by the replaceable cassette side of the mold, the optical characteristics of the lens curve can be changed without changing the sides of the mold.

Another aspect of the present invention is to provide an injection molding apparatus or machine that is vertically positioned to form an ophthalmic device, preferably using the molds of the present invention. Vertical injection molding machines require less shop space than horizontal injection molding machines. Also, vertical injection molding machines are easier to incorporate with other components of a production line. Another advantage of the vertical injection molding machine is: at least one vertically moving mold half can be moved horizontally by the transport mechanism when molding and simply replaced by a new mold half in the vertical injection molding machine with minimal machine downtime, making the molding process more economical and efficient.

It is another object of the present invention to provide an improved mold for making front and back curve pieces having the same wall thickness.

Drawings

In the drawings, like numbering represents like elements:

figure 1 is a side view of a front curve and back curve assembly comprising a front curve and back curve.

Fig. 2 is a top view of a first mold half.

Fig. 3 is a cross-sectional view of the first mold half of fig. 2 taken along line 3-3 of fig. 2.

FIG. 4 is a cross-sectional view of a mold in an open position; the mold is formed from the same first mold half and a second mold half shown in fig. 3.

Fig. 5 is a vertical injection molding machine of the present invention.

Fig. 6 is an enlarged portion of a vertical injection molding machine of the present invention showing the robot arm.

Detailed Description

The molds of the invention can be used to make ophthalmic devices such as contact lenses, intraocular lenses, other forms of lenses, and molded parts of molds, such as lens curves used to make contact lenses. Preferred uses of the mold are in the manufacture of molded plastic parts for contact lenses, or ophthalmic devices, more preferably in the manufacture of plastic molded parts for the production of contact lenses, and most preferably in the manufacture of curved lens parts. The mold for the preferred embodiment will be described below; however, the present invention is not limited to the embodiments described and may be modified or used to manufacture other ophthalmic devices. For example, molds of the present invention having replaceable mold halves and/or replaceable cassettes may be used to mold contact lenses using methods such as those described in U.S. Pat. No. 5,782,460 and the prior art of WO/98/42497, which are incorporated herein by reference. For manufacturing contact lenses, the mold halves are pivotally hinged together as taught in those prior art documents.

In a preferred embodiment, the mold is used to form "lens curve", i.e., "front curve" and "back curve". In the prior art lens curve elements, i.e. the front curve element and the back curve element, a mold or mold half for the production of contact lenses has been explained. Although the lens curve is used to mold a contact lens, the terms "mold" and "mold half" are not used herein to describe a lens curve. The terms "mold" and "mold half" will be used to describe the mold and mold half used to form an ophthalmic device, such as a lens curve.

FIG. 1 shows a preferred lens curve element assembly 110, individual elements of which are made using the mold of the present invention. The mold will be described later. Lens curve assembly 110 is comprised of a front curve member 112 and back curve member 114 defining an opening 113 in which opening 113 a contact lens reaction mixture is polymerized or cross-linked to form a contact lens. Front curve 112 and back curve 114 are formed of a plastic material, preferably polystyrene, polypropylene, cyclo-olefin, or the like, and are formed in first and second molds of the present invention (described in more detail below), preferably in an injection molding machine. Front curve piece 112 and back curve piece 114 are similar to those of the prior art disclosed and used to manufacture contact lenses, for example, as suggested in U.S. patent No. 5,545,366, which is incorporated by reference herein. Front curve 112 has a central curved section with an optical quality concave surface 19, which preferably has a circular circumferential defining edge 116 extending from its periphery. The concave surface 119 is preferably sized to the optical power of the anterior surface of a contact lens to be produced in the lens assembly 110. The front curve piece has a preferred thickness of between 0.2mm and 1.0 mm; the optimum thickness is about 0.6 mm.

Back curve element 114 has a central curved segment with an optical quality convex surface 118. The back curve piece 114 has the dimensions of the back surface of the contact lens to be produced by the lens assembly 110 and, for example, for a toric lens, determines the cylindrical power. Back curve piece 114 has a preferred thickness of between 0.2 and 1.0 mm; the optimum thickness is about 0.6 mm. The front curve element and the back curve element preferably have the same thickness. Each of the front curved member 112 and the back curved member 114 includes an annular flange 115, and a tab 117 integrally formed and protruding from one side of the flange 115. Both front curve 112 and back curve 114 are shown with gate vestige 121, which is sometimes formed at the gate or injection hot tip, which in the preferred embodiment is used to supply molten thermoplastic material to the mold in which front curve 112 and back curve 114 are formed.

The improvement of the front curve and back curve elements of the present invention over prior art front curve and back curve elements such as disclosed in U.S. patent No. 5,545,366 involves a reduction in the volume of plastic used to form the front curve and back curve elements. This reduction in material is achieved by reducing the size of the tabs 117 and flanges 115. Also, preferably, the front curved surface piece and the back curved surface piece have a small thickness, that is, as small as 0.8mm, and the two lens curved surface pieces have the same thickness. Also, the preferred front curve and back curve of the present invention do not have an area traversing from the hot tip of the spray to collect small amounts of scrap of hot and cold plastic material that may form at the hot tip of the spray. Preferably the fins have a flat rounded triangular shape and no steps to block the flow of polymer into the mold. The weight of the thermoplastic material used to form the front curve or back curve is preferably less than 0.5gm, more preferably less than 0.4gm, and most preferably less than 0.3 gm. The best weight is shown to be reduced by about 25% compared to prior art front curve and back curve pieces. Preferably, the combined weight of the front curve element and the back curve element is less than 0.7 gm. Surprisingly, the weight and volume of the thermoplastic material ejected to produce the lens curve is reduced, and the thickness of the components and the size of the fins are reduced, without degrading the optical quality of the front and back curve. In fact, the present invention provides an improvement in the quality of the front and back curves over prior art front and back curves having a greater weight and volume of thermoplastic material and having steps, and other molding features to improve part quality. Also, and unexpectedly, lenses made using front curve pieces and back curve pieces with the same part thickness (e.g., 0.6mm) had better lens quality than was not expected in the prior art. Prior to the present invention, it was believed that the thickness of the back curve element had to be small compared to the front curve element to provide a high quality lens.

Both the front curve piece and the back curve piece of the present invention are preferably made using a modified mold and injection molding machine, which will be described below. Such an improved mold and injection molding machine will be described herein; aspects of the mold or molding process not described herein are as described in U.S. patent No. 5,545,366 and U.S. patent No. 5,451,155, which are incorporated by reference herein, or are known to those of ordinary skill in the art.

Figure 2 is a top view of a first mold half 20 used to mold front curve 112 and back curve 114 in a single mold. (the preferred mold includes a first mold half 20 and a second mold half 440, as shown in fig. 4.) preferably, the first mold half 20 has two cassettes 21, 22 removably attached to a molding base 23. Depending on the injection molding to be performed, there may be one or more cassettes that are removably attached to the molding base 23. Preferably two or three cassettes, and most preferably one cassette, are shown in figure 2 as cassettes 21, 22 which are removably attached to the moulded base 23 by virtue of each cassette having two readily accessible screws 29. Thus, replacing the cassette on the molded base 23 is a simple and quick job. Alternatively, the cartridge may be attached to the molded base 23 with any mechanism, such as a retaining clip, post, bolt, snap clamp, and magnetic force; however, it is good that the mechanism provided should allow for simple and quick removal of the cartridge from the molded base. Preferably, a plurality of inserts 24, 25 are embedded in each cassette for receiving thermoplastic material for forming the lens curves. It is preferred that the inserts 24, 25 are individually removable from the cartridge; but the cassette and insert may be abutted if desired. Preferably, each cassette comprises two to twenty inserts, more preferably four to ten inserts. The insert, sometimes referred to as a power insert, may be constructed of any material that can support an optical finish, such as pure steel, brass, copper chromium metal, or cobalt nickel alloy martensitic steel. Alternatively, and particularly for embodiments that include an insert to directly manufacture a mold for a contact lens, the insert may comprise quartz, ceramic, or a polymeric material such as polycarbonate, cyclo-olefin, polystyrene, polypropylene, or poly (acrylonitrile).

In a preferred mode, cassette 21 holds front curve insert 24 to form front curve 112 (when properly mated with second mold half 440), and cassette 22 holds back curve insert 25 to form back curve 114 (when properly mated with second mold half 440). Second mold half 440, shown in fig. 4, has inserts that are complementary to inserts 24, 25 in first mold half 20 to form front curve piece 112 and back curve piece 114, respectively. The first mold half 20 and the second mold half 440 are both parts of a family of molds, meaning that multiple types of parts can be made in a single mold consisting of a first mold half 20 and a second mold half 440. Prior to the present invention, it was not anticipated that various types of components of optical quality could be made in a family of series of molds.

The cassette is preferably made of a metal such as stainless steel, tool steel, high hardness machinable alloy, or the like; in an alternative embodiment the cassettes may be manufactured from a polymeric material. The cassettes are preferably made using nickel plated tool steel. The metal from which the cassette is made is preferably mechanically perforated to form openings for receiving the inserts and other channels and paths for cooling water and air (described in detail below). The cassette preferably weighs less than 12 pounds. The mold halves of the prior art typically weigh between 100 and 150 pounds, requiring a crane to operate when one or more mold halves must be replaced in an injection molding machine, and requiring a minimum of 30 minutes to replace the mold halves. In contrast, the cassette of the present invention is light enough to allow easy loading and unloading by an operator, and can be removed from one mold half and replaced with another in less than 8 minutes, preferably less than 4 minutes, and more preferably less than 3 minutes. In preferred embodiments, the cassette or cassettes represent a portion of the thermal mass of the mold halves, preferably the cassette or cassettes on the mold halves comprise less than 90%, more preferably less than 70%, and most preferably less than 50% of the total mass of the fully assembled mold halves. In a preferred embodiment, each cassette represents 20% of the total mass of the fully assembled mold halves.

Fig. 3 is a cross-sectional view taken along line 3-3 of the first mold half shown in fig. 2. Fig. 3 shows the front curve insert 24 and the back curve insert 25 in the cassettes 21, 22, respectively. Fig. 4 shows a cross-section of a first mold half 20 and a cross-section of a complementary second mold half 440, which together form a mold 475. Fig. 4 shows the mold formed by the first mold half 20 and the second mold half 440 in an open position. The first mold half 20 has an insert 24 with a convex molding surface and the second mold half 440 has an insert 441 with a concave molding surface. While the first mold half 20 has an insert 25 with a concave molding surface and the second mold half 440 has an insert 442 with a convex molding surface. In a preferred arrangement, inserts forming the optically critical surface 119 (shown in FIG. 1) of front curve 112 and/or (preferably "and") forming the optically critical surface 118 (shown in FIG. 1) of back curve 114 are placed into one or more cassettes that are each part of the same mold half (preferably first mold half 20). In a preferred mode, the inserts for the back curve are all located in a cassette and the inserts for the front curve are all located in separate cassettes within the first mold half.

The second half mold 440 may comprise a replaceable cassette that includes inserts for forming critical and non-critical surfaces, and which may be simply and quickly removed from the second mold half; however, in a preferred mode, the second mold half 440 does not include a cassette, but instead, the second mold half preferably includes a plate, frame, or similar support to hold the insert forming the non-optically critical surface of the front curve and/or (preferably "and") back curve. Inserts 441 and 442 preferably fit into the plate, frame, or rack, and are each individually removable from the second mold half; however, the insert may abut the plate, frame or bracket if desired.

In a preferred embodiment, both the front curve insert 441 and the back curve insert 442 are embedded in a plate 443 of the second mold half 440. The plate 443 is made of the type of metal used to make the cassettes described above, which has been drilled to substantially match the full size of the inserts 441, 442. The plate 443 is mounted at the hot runner base 444. Similar to that described and disclosed in the prior art, the plate 443 and hot runner base 444 have an extrusion portion (not shown) for introducing molten thermoplastic material into a closed mold to form a front curve and a back curve. See, for example, U.S. patent No. 5,545,366, previously incorporated by reference herein. In a preferred mode, because the insert forms a non-critical surface of the lens curve, the second mold half 440 is preferably installed in an injection molding machine and only occasionally removed for maintenance or replacement of a worn or damaged insert. At this point, the plate 443 may be removed from the hot runner base 444 and the inserts 441 and 442 may be replaced, or the entire plate 443 and inserts 441, 442 may be replaced. Such maintenance typically requires the injection molding machine to stop producing the ophthalmic device for up to 15 minutes or more.

The inserts 441, 442 in the second mold half 440 are both cooled with circulating water that travels through the plate 443 and around the smaller diameter portions 449 of the inserts 441, 442 in conduits 448. The O-ring 450 maintains a water tight seal around the inserts 441, 442 (it must be noted that the detail of one of the four inserts shown embedded on the second mold half 440 is similar to all of the inserts 441, 442. additionally, the detail of one of the four inserts shown embedded on the first mold half 20 is similar to all of the inserts 24, 25, except that the detail of the insert 25 within the cassette 22 is a mirror image of the detail of the insert 24 within the cassette 21). Circulating water preferably flows through the plate 443 into a single circuit, contacting all of the inserts 441, 442 in each circuit. Because the plate 443 is not removed from the injection molding machine as often, direct water cooling of the inserts is preferred, although direct water cooling complicates replacement of the inserts.

In the first mold half 20 carrying the cassettes 21, 22 there is a novel cooling mechanism. Instead of water cooling directly contacting the inserts 24, 25 requiring a water seal, complex and sluggish cassette removal and interchangeability capabilities, cooling of the inserts 24, 25 in the first mold half is accomplished using a heat transfer block 335. The heat conductive blocks 335 are preferably placed in the mold base 23. The heat conductive block 335 directly contacts the inserts 24, 25 when both cassettes 21, 22 are mounted to or attached to the molded base 23. The heat conductive block 335 is preferably made of copper, copper chrome, copper zinc, brass, nickel plated brass, or similar high heat conductive material. Steel is also a possible choice but not necessarily the best. To improve the thermal conduction of the molded part requiring cooling, it is also preferred to machine the insert from the high thermal conductivity materials listed above. The heat transfer block contacts and preferably is formed partially around a water tube 331 and preferably is pumped through the water tube 331 into a single circuit to pass back and forth through the molded base 23 containing all of the heat transfer block 335. Alternatively, the water tube and cooling block may be made from a single piece of metal. The water pipe 331 cools the cooling block 335 for cooling the inserts 24, 25. In this way, all the inserts 24, 25 are cooled indirectly by water. The water pipe 331 contains distilled water filled under vacuum. Alternatively, other indirect cooling methods may be used to cool the insert, such as solid heat pipes with or without fins or connected to a cooling block, heat pipes with or without fins containing a fluid or coolant, or the like.

Fig. 3 and 4 illustrate an air injection system for removing the front and back curve pieces from the first mold half 20 and the second mold half 440. In contrast to the ejector pins used in the prior art, the air jet does not distort the lens and can be performed when the lens curve is at a higher temperature. The air jets and reduced material in the front and back curve elements allow the front and back curve elements to be molded in a cycle time of less than 6 seconds, preferably less than 4 seconds, and more preferably about 2 seconds. Air is sprayed over an area of 2mm x 100 microns to about 3 mm x 300 microns at about 5 to 6 bar. Air is ejected through the gaps 336, 451 around the perimeter of the top of each insert 24, 25, 440, 441. The width of the gaps 336, 451 is preferably less than 12 μm. Alternatively, a plurality of holes are provided on the perimeter around the top of the insert for air injection.

For the second mold half 440, air connected to a source of compressed air, not shown, is provided to the gap 451 from a path 446 via the grooves 447. For the first mold half 20, air connected to a source of compressed air, not shown, is provided from a path 332 to the gap 336 via channels 333.

The channels 333, 447 connecting the pathways 332, 446 form a plurality of slots into the cassettes 21, 22 and the plate 443 by mechanical cutting at a diameter around the opening of the receiving insert 24, 25, 441, 442. Alternatively, the channels 333, 447 may be cut into the inserts 24, 25, 441, 442.

Fig. 2 and 3 show a connector nozzle 345 in communication with the path 332 and connectable to a source of air (not shown) for the cassettes 21, 22. When the first mold half 20 with the cassettes 21, 22 already attached is removed from the molding machine, or if one or both cassettes 21, 22 are removed from the base 23 of the first mold half 20, the air path 332 can be easily disconnected from the air source (not shown) via the connector nozzle 345. The air source connected to the connector nozzle 345 preferably has one or more valves that can be closed, or preferably automatically closed, when the mold halves are removed from the molding machine. The cassettes have at least one nozzle, preferably two nozzles 345 per cassette, one on each side of each cassette. When one nozzle 345 is attached to the air source, it is preferable to plug the other nozzle 345.

Just as and just before the first and second mold halves change from a closed position to an open position, air is preferably ejected from all gaps 451 at the top of the inserts 441, 442 in the ambient second mold half 440 in a single shot. A single jet of air removes the front curve and back curve from second mold half 440, and thus the lens curve preferentially adheres to or rests on first mold half 20. After opening the mold halves, a single jet of air is ejected from all gaps 336 around the top of the inserts 24, 25 in the first mold half 20 and the front and back curve pieces are removed from the first mold half 20. The air jets from the first mold half 20 occur simultaneously with the movement of a robot arm 600 (shown in fig. 6) to move to a position between the mold halves to pick up the released front and back curved pieces. As another alternative, the process may be modified such that the front curve and back curve pieces remain on second mold half 440. Alternatively, other mechanisms may be used to cause the lens curve to adhere preferentially to the mold half, such as a surface treatment of the insert, an anchor on one surface of the lens curve, or other known methods; however, it is preferred to use air jets to release the lens curve on at least one (preferably "two") mold half.

Fig. 5 illustrates a preferred injection molding machine 500 in which the mold of the present invention is used. The preferred injection molding machine is a vertical injection molding machine 500 as disclosed in U.S. Pat. No. 5,451,155. The preferred vertical injection molding machine has a movable platen 507 with a lower mold half 520 removably mounted on the platen 507. The movable platen is a horizontal table as described in U.S. patent No. 5,451,155. The term movable platen will be used herein. The lower mold half 520 is preferably a first mold half having a removably assembled cassette as previously described. The upper mold half 540 faces the lower mold half, which is shown in phantom in fig. 5. The upper mold half 540 is preferably the second mold half previously described. The upper mold half 540 is removably fitted over the support plate 503. The support plate 503 is preferably held stationary for all times. In this embodiment, the lower mold half 520 and movable platen 507 are moved up and down to open and close the mold.

In a preferred embodiment, there is a transport mechanism, shown as at least one or preferably two of conveyors 516, 517, for rapidly replacing one lower mold half 520 with another lower mold half 520'. Alternatively, the transport mechanism may be a pneumatic, hydraulic, or electric drive chain. In the preferred embodiment, the transport mechanism is a hydraulically driven chain. Fig. 5 shows the lower mold half 520' to be embedded into the molding machine 500 on the conveyor 517. In a preferred mode, both conveyors 516, 517 may be inserted or removed from the mold halves; thus, with regard to the description of the actions at the conveyor 517, the actions that may be performed by the conveyor 516 are described, and vice versa.

After the mold halves 520 in the molding machine have made a particular number of ophthalmic devices, i.e., lens curves, the mold halves 520 are automatically unlocked from the movable platen 507, the conveyor 516 attaches itself to the lower mold half 520 via the brake mechanism 509, and the mold halves 520 are pulled away from the movable platen 507 and placed on the conveyor 516. In a preferred embodiment, the mold halves are moved by hydraulically driven chains, but are supported by a support surface and guide rails on each side of the support surface. At this point, the conveyor 517 attached to the mold half 520 ' pushes the mold half 520 ' onto the movable platen 507 via the capture mechanism 510, and when properly placed, the mold half 520 ' is locked in place. The mold halves are preferably held on the movable platen 507 via hydraulic clamps 532. Once the mold half 520 'is locked in place, the molding machine 500 may begin manufacturing a new ophthalmic device using the newly installed lower mold half 520'. It takes less than 60 seconds, preferably less than 30 seconds, and more preferably less than 20 seconds to replace one mold half 520' with another.

The quick change of the one lower mold half 520 with the other lower mold half 520 ' is further facilitated by the provision of double water and/or air (not shown), preferably both, to at least the two lower mold halves 520, 520 ' so that water and air connections do not need to be physically moved from one mold half 520 to the other mold half 520 ' to facilitate the change of one mold half with the other. In a preferred mode, the lower mold half 520 on the movable platen 507, and the lower mold half 520' on the transport mechanism 517, have dual water and air supplies. Again, if desired, one or more heating elements (not shown) may be provided to heat the inserts present within the lower mold half 520 'on the conveyor 517 prior to inserting the lower mold half 520' into the molding machine. Heating the lower mold half 520' prior to mounting it on the movable platen 507 reduces the time required for the insert to reach the optimum molding temperature range (the insert in the mold half needs to be heated first to reach a temperature within the optimum molding temperature range, but after several cycles of molding the part, the insert needs to be cooled to maintain it within the optimum molding temperature range). By preheating the lower mold half 520' on the conveyor 517, the insert in the lower mold half can reach the optimum molding temperature range in two or fewer molding cycles, resulting in shorter machine downtime and less scrap. The time required to heat the lower mold half 520 is also reduced if only one or two cassettes are replaced in the mold half without removing the lower mold half 520 from the movable platen 507, and the lower mold half 520 is used to manufacture more ophthalmic devices before cooling. In an embodiment of the invention, the base of the mold half will remain hot and be able to transfer heat to one or more replaced cassettes. However, if the lower mold half 520 is moved away from the movable platen 507 and the other lower mold half 520' is being used for molding. And replacing one or more cassettes in the lower mold half 520, there is still the benefit of faster warm-up time than replacing the entire lower mold half, since the base of the lower mold half 520 will transfer heat to the one or more replaced cassettes.

After one mold half is replaced, one or more cassettes that were just removed from the movable platen into a conveyor mold half may be replaced, the entire mold half may be replaced with another mold half, or the mold half may be later reinstalled on the movable platen. The two cassettes in the mold halves can be replaced in less than 6 minutes, preferably less than 4 minutes, and most preferably less than 2 minutes. After the cassette replacement is complete, the insert is preheated and ready to be mounted on movable platen 507. The preheating is preferably less than 1 minute. Preferably, at least one, and preferably one, lower mold half 520' is ready for use on one of the belts 516 or 517 when the lower mold half 520 is ready to be removed from the movable platen 507.

Preferably, the movable platen 507 is movable between a down position (as shown) and a closed position; during this lower position, the mold is open; while in the closed position, the inserts in the lower mold half 520 contact the inserts in the upper mold half 540 and the inserts on the two mold halves together form a mold cavity; a molten thermoplastic material is injected into the mold cavities. After injection and about 0.5 to 1.5 seconds after cooling the part, the mold halves separate as air from the air jet gap in the upper mold half pushes the front and back curve pieces on the insert in the lower mold half 520. The movable platen 507 and lower mold half 520 are moved to the open position shown in fig. 5. The molded lens curve is then removed from the lower mold half 520, preferably by a robot. This preferred robotic arm is shown in figure 6.

Fig. 6 shows a portion of a preferred injection molding machine 500, and a preferred robot arm 600 in greater detail. The robotic arm 600 includes a link 601, an arm 602, and an end of an arm tool 603. With the upper mold half 540 and the lower mold half 520 in the open position as shown in fig. 5 and 6, the robot 600 moves horizontally between the upper mold half 540 and the lower mold half 520. The robot 600 then moves horizontally in the opposite direction away from the area between the lower mold half 520 and the upper mold half 540 as the lower mold half 520 moves toward the upper mold half 540 to form a closed mold. In a preferred mode, as shown in FIG. 6, the robot is a direct drive robot, i.e., a drive mechanism 610 for the robot slides up and down with the movement of the movable platen 507. The robot arm moves horizontally through gears and rotatable cogs, such as rack and pinion mechanisms (not shown), i.e., the robot arm moves in and out between the mold halves as the molds open and close, respectively. The robot arm is shown positioned inside the open mold, e.g., between the upper mold half 540 and the lower mold half 520. As the robot arm 600 moves horizontally into position between the mold halves, the trailing end of the arm tool 603 is preferably lowered adjacent the surface of the lower mold half 520 (as shown in the figures) via a vacuum extender 620, which moves the trailing end of the arm tool 603 up and down. Vacuum extender 620 is connected to a vacuum source (not shown). (when the vacuum source is activated, the trailing end of arm tool 603 is moved upward via retraction of vacuum extender 600. when the vacuum device ceases to function, the trailing end of arm tool 603 is moved downward via extension of vacuum extender 520). At this point, the lens is ejected by the air ejection system away from the lower mold half 520. The trailing end of the arm tool 603 preferably has a cup portion 604 that is connected to a vacuum source (not shown) that is activated to pick up a lens curve (not shown) that is ejected by air. When the lower mold half 520 is moved toward the stationary upper mold half 540, the robotic arm preferably moves out from between the upper mold half 540 and the lower mold half 520 via a direct drive mechanism and transfers the front curve piece and back curve piece to another robotic arm (not shown) for proper placement on a lens curve piece pallet (not shown), similar to that described in the prior art.

Due to the thinner lens curve and the air jet, the cycle time of the present invention is less than 6 seconds, preferably less than 4 seconds, and more preferably 2 to 3 seconds. Cycle time refers to the time required to proceed from opening the mold to closing the mold and back to opening the mold.

In an alternative embodiment, the molds of the present invention having replaceable mold halves and/or interchangeable cassettes can be used to mold contact lenses using methods described in the prior art, such as U.S. Pat. No. 5,782,460 and NO/98/42497, which are incorporated herein by reference. A mold for use with this embodiment may include first and second mold halves, at least one of which includes an insert for forming a contact lens. Preferably, at least one of the inserts used to make each contact lens is a reaction mixture capable of transmitting radiant energy for polymerization to make the contact lens. Suitable insert materials are described above. For this embodiment, at least one mold half, and preferably both mold halves, comprises at least one, and preferably at least two, cassettes comprising inserts for forming contact lenses. When forming a contact lens, all inserts provide an optically critical surface to the contact lens. The mold halves and cassettes are easily replaceable and can be used in different combinations to produce a number of finished product holding units. The mold half may include a base, which may be in the shape of a frame, support, plate, or the like, to which the cassette is removably attached. The mold halves may be pivotally hinged or may be moved apart vertically, either horizontally or vertically. In embodiments where the mold is used to form a contact lens, the mold preferably does not provide air jets to cool the insert or contact lens as described earlier. The ejection of the contact lens from the insert may be accomplished by immersing the contact lens in water.

In a preferred mode, an identifier such as a Radio Frequency (RF) chip or the like may be placed on each cassette to store information identifying the ophthalmic device that it forms. The identifier may also be used to track the cassette. This preferred example is fully described in the co-pending application entitled "method and apparatus for bulk tracking and transformation," VTN-419 also being incorporated by reference into this application. The molding machine preferably includes a computer which programs or receives input information for the manufacture of ophthalmic devices from the molding machine. Based on this information, the computer determines when the mold or cassette needs to be replaced. When a mold or cassette is replaced, the molding machine reads the identifier information on the cassette to determine that the correct cassette and/or mold halves are in the machine. Based on the information of the ophthalmic device to be produced by the machine, the process conditions can be automatically adjusted for the new ophthalmic device to be produced. The computer tracks the number of devices being manufactured and schedules the next mold or cartridge change.

Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that: various omissions, substitutions and changes in the form and details of the devices described, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. Substitutions of elements from one described embodiment to another are also fully intended. It should also be understood that: the drawings are not necessarily to scale.

Claims (67)

1. A mold for forming an ophthalmic device comprising:

a first mold half that cooperates with a second mold half, wherein said second mold half comprises an insert and said first mold half comprises a base, attachment means by which said cassette is removably attached to said molding base, and at least one replaceable cassette comprising a surface that is not in contact with said molding base and insert, wherein said attachment means is accessible on said surface of said replaceable cassette but does not contact said base, and wherein said insert in said at least one replaceable cassette comprises an optical quality surface.

2. The mold of claim 1, wherein: the first mold half includes at least two replaceable cassettes in use.

3. The mold of claim 2, wherein: the replaceable cassette includes an insert for forming a lens curve.

4. The mold of claim 3, wherein: the replaceable cartridge includes an insert shaped to form a back curve and a front curve.

5. The mold of claim 1, wherein: the insert is an insert for forming a contact lens.

6. The mold of claim 1, wherein: the first mold half includes an insert for an optically critical surface of the ophthalmic device and the second mold half includes an insert for a non-optically critical surface of the ophthalmic device.

7. The mold of claim 6, wherein: the first mold half includes inserts for optically critical surfaces of the front curve piece and back curve piece.

8. The mold of claim 1, wherein: the second mold half comprises at least one replaceable cassette comprising an insert of the second mold half, and the inserts in the first and second mold halves form the optically critical surfaces of the ophthalmic device.

9. The mold of claim 4, wherein: the insert for the optical critical surface of the front curve is in a first cassette and the insert for the optical critical surface of the back curve is in a second cassette, the first and second cassettes being simultaneously attached to the first mold half.

10. The mold of claim 1, wherein: the insert in the at least one replaceable cartridge is indirectly cooled.

11. The mold of claim 1, wherein: the insert is cooled by contact with a heat transfer block.

12. The mold of claim 1, wherein: the ophthalmic device is ejected from the first mold half or the second mold half by at least one air pulse.

13. The mold of claim 1, wherein: the ophthalmic device is ejected from the first and second mold halves by at least one air pulse from each of the first and second mold halves.

14. The mold of claim 13, wherein: the insert in the at least one replaceable cartridge is indirectly cooled.

15. The mold of claim 1, wherein: the ophthalmic device is removed from the insert with water.

16. The mold of claim 1, wherein: the mold is inserted into an injection molding machine.

17. The mold of claim 16, wherein: the injection molding machine is a vertical injection molding machine wherein the first mold half is a lower mold half.

18. The mold of claim 17, wherein: the vertical injection molding machine includes a directly driven robotic arm that picks up the ophthalmic device.

19. The mold of claim 18, wherein: the mold simultaneously forms an optical quality front curve piece and a back curve piece.

20. The mold of claim 16, wherein: the cycle time of the injection molding machine is less than 4 seconds.

21. The mold of claim 17, wherein: the time taken to change the first half mould to another first half mould may be less than 60 seconds.

22. The mold of claim 1, wherein: the attachment means is selected from the group consisting of screws, brackets, bolts, quick clamps and magnetic forces.

23. A molding system for forming an ophthalmic device includes a mold having a first mold half and a second mold half,

wherein said first mold half comprises at least one replaceable cassette comprising a surface not in contact with the molding base and insert, and said molding system further comprises at least one more replaceable cassette than said replaceable cassette removably attached in use to said first mold half, said replaceable cassette comprising a plurality of differently shaped inserts, and wherein said inserts in said replaceable cassette comprise optical quality surfaces, and said second mold half comprises inserts defining cavities with said inserts in said replaceable cassette that form said ophthalmic devices.

24. The molding system of claim 23, wherein: the first mold half, in use, includes at least two replaceable cassettes.

25. The molding system of claim 23, wherein: the first mold half also includes a base to which the at least one replaceable cassette is removably attached.

26. The molding system of claim 24, wherein: the replaceable cassette includes an insert for forming a lens curve.

27. The molding system of claim 26, wherein: the replaceable cartridge includes an insert for forming a back curve and a front curve.

28. The molding system of claim 24, wherein: the replaceable cartridge includes an insert for forming a contact lens.

29. The molding system of claim 23, wherein: the first mold half includes an insert for an optically critical surface of the ophthalmic device and the second mold half includes an insert for a non-optically critical surface of the ophthalmic device.

30. The molding system of claim 29, wherein: the first mold half includes inserts for the optically critical surfaces of the front and back curve pieces.

31. The molding system of claim 23, wherein: the second mold half comprises at least one replaceable cassette comprising an insert of the second mold half and an insert forming an optically critical surface of the ophthalmic device within the first mold half and the second mold half.

32. The molding system of claim 27, wherein: the insert for the optical critical surface of the front curve is in a first cassette and the insert for the optical critical surface of the back curve is in a second cassette, the first and second cassettes being simultaneously attached to the first mold half.

33. The molding system of claim 23, wherein: the insert in the cassette is cooled indirectly.

34. The molding system of claim 23, wherein: the insert is cooled by contact with a heat transfer block.

35. The molding system of claim 23, wherein: the ophthalmic device is ejected from the first mold half or the second mold half by at least one air pulse.

36. The mold of claim 23, wherein: the ophthalmic device is ejected from the first and second mold halves by at least one air pulse from each of the first and second mold halves.

37. The molding system of claim 24, wherein: the insert in the cassette is cooled indirectly.

38. The molding system of claim 23, wherein: the ophthalmic device is removed from the insert with water.

39. The molding system of claim 23, wherein: the mold is inserted into an injection molding machine.

40. The molding system of claim 39, wherein: the injection molding machine is a vertical injection molding machine wherein the first mold half is a lower mold half.

41. The molding system of claim 40, wherein: the vertical injection molding machine includes a directly driven robotic arm that picks up the ophthalmic device.

42. The molding system of claim 41, wherein: the mold simultaneously forms an optical quality front curve piece and a back curve piece.

43. The molding system of claim 39, wherein: the cycle time of the injection molding machine is less than 4 seconds.

44. The molding system of claim 40, wherein: the time taken to change the first half mould to another first half mould may be less than 60 seconds.

45. A molding system for forming an ophthalmic device, comprising:

a plurality of first mold halves containing inserts, said inserts comprising optical quality surfaces, and a second mold half containing inserts, wherein each first mold half cooperates with said second mold half to produce ophthalmic devices of different shapes; the first mold half includes at least one replaceable cassette including a surface that is not in contact with the molded base and insert.

46. The molding system of claim 45, wherein: the first mold half includes at least one replaceable cassette, and the molding system further includes at least one more replaceable cassette than the first mold half, the replaceable cassette being removably attachable to the first mold half in use, the replaceable cassette including a plurality of differently shaped inserts.

47. The molding system of claim 46, wherein: the first mold half, in use, includes at least two replaceable cassettes.

48. The molding system of claim 46, wherein: the first mold half also includes a base to which the at least one replaceable cassette is removably attached.

49. The molding system of claim 47, wherein: the replaceable cassette includes an insert for forming a lens curve.

50. The molding system of claim 49, wherein: the replaceable cartridge includes an insert for forming a back curve and a front curve.

51. The molding system of claim 46, wherein: the replaceable cartridge includes an insert for forming a contact lens.

52. The molding system of claim 46, wherein: the first mold half includes an insert for an optically critical surface of the ophthalmic device and the second mold half includes an insert for a non-optically critical surface of the ophthalmic device.

53. The molding system of claim 52, wherein: the first mold half includes inserts for the optically critical surfaces of the front and back curve pieces.

54. The molding system of claim 46, wherein: the second mold half comprises at least one replaceable cassette comprising an insert of the second mold half and an insert forming an optically critical surface of the ophthalmic device within the first mold half and the second mold half.

55. The molding system of claim 50, wherein: the insert for the optical critical surface of the front curve is in a first cassette and the insert for the optical critical surface of the back curve is in a second cassette, the first and second cassettes being simultaneously attached to the first mold half.

56. The molding system of claim 46, wherein: the insert in the cassette is cooled indirectly.

57. The molding system of claim 46, wherein: the insert is cooled by contact with a heat transfer block.

58. The molding system of claim 46, wherein: the ophthalmic device is ejected from the first mold half or the second mold half by at least one air pulse.

59. The mold of claim 46 wherein: the ophthalmic device is ejected from the first and second mold halves by at least one air pulse from each of the first and second mold halves.

60. The molding system of claim 59, wherein: the insert in the cassette is cooled indirectly.

61. The molding system of claim 46, wherein: the ophthalmic device is removed from the insert with water.

62. The molding system of claim 46, wherein: the mold is inserted into an injection molding machine.

63. The molding system of claim 62, wherein: the injection molding machine is a vertical injection molding machine wherein the first mold half is a lower mold half.

64. The molding system of claim 63, wherein: the vertical injection molding machine includes a directly driven robotic arm that picks up the ophthalmic device.

65. The molding system of claim 46, wherein: two ophthalmic devices of different optical qualities are formed simultaneously.

66. The molding system of claim 62, wherein: the cycle time of the injection molding machine is less than 4 seconds.

67. The molding system of claim 62, wherein: the time taken to change the first half mould to another first half mould may be less than 60 seconds.