HK1068305B - Injection molded thermoplastic spectacle lens suited for fully automated dip hardcoating - Google Patents

Description

Injection molding thermoplastic plastic spectacle lens suitable for full-automatic impregnation hard plating

This application is a divisional application entitled "molding, demolding and dip hard coating of thermoplastic ophthalmic lenses" (application No. 00121798.4, application date: 1996, 9/20).

1. Field of the invention

The field of the invention is plastic injection compression molding of pairs of burr-free, cleanliness-improved thermoplastic ophthalmic lenses which are then conveyed for subsequent in-line dip hard-coating processing. In particular, the method and apparatus for multi-cavity injection molding of polycarbonate ophthalmic lenses is integrated with the immersion hard-coating process through a fully automated process to produce clean hard-coated molded lenses entirely in a single continuous enclosed clean room surrounding the lenses, without any operator in the clean room, and without requiring any shearing or trimming of the molded lens or runner system prior to immersion coating, nor the use of chlorofluorocarbon (CFC) or aqueous cleaning protocols. The atmospheric cleaning chamber and automated processing extensions optionally provide automated monitoring of optical power and appearance quality of in-line continuous article flow lenses and/or optionally provide in-line continuous article flow vacuum coating of antireflective films, and then transport the molded and hard-coated polycarbonate lenses out of the continuous closed cleaning chamber or to manual processing.

2. Background of the invention

Market prospect of polycarbonate Rx lens

The field of related products relates to plastic spectacle lenses (hereinafter referred to as Rx lenses) for correcting vision against eye diseases, which have refractive indexes of 1.530 and 1.49 to 1.50 of CR-39 (chemically peroxide crosslinked ethylene carbonate propylene glycol ester thermosetting casting lenses) of glass. This is the material that has grown the fastest in recent 5 years for Rx lens materials, whether in the united states or world markets. The demand for such cast thermoset lenses and injection molded thermoplastic lenses is extremely high because consumers/wearers of ophthalmic lenses find such lenses thin (due to the greater refractive power of the high index plastic) and lightweight (lower specific gravity, especially polycarbonate compared to CR-39). Therefore, the wearer of the myopia glasses can avoid the ugly appearance of the glasses like the coke bottle glasses. In addition, the light weight means that the nose bridge and the top of the ears, which are the load bearing surfaces, feel comfortable and are less subject to weight and pressure.

In the context of such "thin, lightweight" high index plastic Rx lenses, U.S. market statistics show that it accounts for 25-30% of the total market. Within this range, the fraction of thermoset cast high index lenses has remained essentially unchanged since 1991; almost all growth in recent years has been thermoplastic injection molded Rx lenses, particularly lenses made of polycarbonate (refractive index 1.586). (although other candidate high refractive index thermoplastics are contemplated, the most commercially stable to date is polycarbonate, hereinafter "polycarbonate" will replace other optical grade thermoplastics, as will be apparent to the skilled artisan).

The main reason that polycarbonate Rx lenses are seen in the market place rather than cast thermoset high index Rx lenses is reported to be that polycarbonate Rx lenses are relatively inexpensive to produce and can be mass produced. This is due to the high degree of automation that can be achieved with polycarbonate, whereas thermoset casting operations are inherently less than such highly automated, which requires more manpower. The low production rate coupled with the highly automated production results in a very high fixed cost, but the production rate, if it exceeds the "break-even" balance point, then it becomes a critical disadvantage for hot set material casting because it inherently requires labor and materials with relatively high fluctuating costs. Subsequently, as product increases, gains for increased amounts per unit will become more advantageous for more automated (polycarbonate) production and.

This is reflected in the market price of the lens manufacturer, where cast high index hard-coated Rx lenses are not at all competitive in price with multi-cavity injection molded hard-coated polycarbonate Rx lenses of the corresponding specification (especially Finished Single Vision (FSV) lenses, which have a higher individual sales volume for each Rx lens). The price of the cast FSV with high refractive index is usually 50-100% higher. For these reasons, further reduction of manufacturing costs by further increasing the level of automation and improving investment benefits (i.e. reducing the yield of the break-even point, which reduces the investment requirements of new manufacturers into this area) is a very important strategy for future development of polycarbonate Rx lenses.

B. Prior patents relating to multi-cavity lens molding and immersion hard-plating.

To date, the production of polycarbonate lenses has been dominated by four companies throughout the world, together estimated to account for more than 90% of the world's market share. At this point each of the four companies employed some form of injection compression multi-cavity molding process and apparatus at the beginning of their "batch" manufacturing flow (see comparative example of fig. 4A). The subsequent step is to shear the runner system and/or degating or stripping the mold piece after molding so that the cut lens can be mounted on the lens holder. These operations are typically manual, semi-automatic, but may be entirely manual. An example of a suspension molded thereon that is adapted to engage a lens holder frame that holds a plurality of such lenses is shown in Weber, U.S. patent 4443159. The next step in the manufacturing process is to use some form of cleaning protocol (all fluorochloroalkane (CFC) ultrasonic vapor degreasing, more recently, aqueous cleaning using a combination of high pressure spraying of aqueous solution and centrifugal spinning, or multi-stage ultrasonic bath immersion followed by drying). These cleaned and dried lenses are then dip-coated in a liquid hard coating solution (a heat-curable silicone type coating solution or an ultraviolet ray-curable coating solution), and the coating is cured by a chemical crosslinking method.

Two of the four polycarbonate Rx lens manufacturers described above allow the use of applicant's us patent 4828769 and 4900242, the third being the assignee of us patent 4933119 by Gentex corporation, Weymouth. The fourth family is the assignee of U.S. patent to bakarr, by neolense corporation. These patents all employ some form of injection compression molding process with multiple mold cavities and employ various means of achieving cavity-to-cavity symmetry. The difference between these three patents applied by the four manufacturers is how the molded lenses are ejected from the lens molds, and the differences are clearly seen by observing the lens peripheral edge and the side wall of the sampled lenses produced by each manufacturer. Shown in more detail in figure 2 and its description. All three of these patents must be cut to at least some degree before immersion plating can be performed.

Referring again to other prior art patents showing multi-cavity injection compression molding of Rx lenses, the Weber device for injection compression molding of Rx lenses (U.S. patent US 4008031) shows a mold that may be dual cavity. For subsequent dip plating operations, hanger 20 is angled 180 relative to gate entrance 23. Weber also shows two mold stripper sheets 16 located at about 10:30 to 1.00 hours, with their gate/drop locations located at 6:00 hours. This position adversely affects the flow of immersion plating solution along the front and back surfaces of the molded lens as it is withdrawn from the immersion bath, but in Weber, it forms a flap and an ejector plate on the four-sided flange 12 so that the solution can flow along the flange from the top to the bottom of each individually held lens (provided the lens does not swing from side to side).

U.S. patent 5093049 to Uehara et al also describes and illustrates an Rx lens injection compression molded with a dual cavity mold, the cavities being connected by runners and gates, and the gates being capable of being mechanically closed at predetermined times of the molding cycle to prevent backflow. Uehara refers to any demolding device for demolding both lenses, without any demolding sheet or demolding pin being shown. If the forward movement of the movable mold core, which provides a compressive force, is limited by a hard stop, the mold core cannot be used to advance the lens, once the mold is opened, so that it moves through the mold line. In this case it is necessary to grasp the cold gate and release the two lenses attached to the gate from the mold. No suspension tabs are shown and mentioned.

Other historically important lens injection compression molding methods include Spector et al, U.S. patent 4836960, and Lalibert, U.S. patent 4364878, both of which are limited to a single mold cavity embodiment.

Referring now to prior art patents for Rx lens immersion plating, in addition to the Weber U.S. patent 4443159 mentioned above, the Laliberte U.S. patent 3956540 (method) and 4036168 (apparatus) describe the use of a form of conveyor that transports such lens holder frames through a multi-station machine having a clean room within which a filtered air environment is present, wherein the lenses are continuously ultrasonically cleaned and destaticized, then immersion plated, dried and at least partially cured to a tack-free state, and then the conveyor transports them to a loading/unloading station where the operator removes the lenses. Similar arrangements have been developed using different automated transfer devices, including double chain drive conveyors operating in parallel and connected by crossbars on which the lens holder racks are suspended, or alternatively, powered overhead conveyors with convertible travel on which the suspended removable lens holders are mounted. This configuration for polycarbonate Rx lenses (and non-Rx lenses) typically uses at least one (and preferably two, when immersed in series) freon ultrasonic cleaner/degreaser wherein the polycarbonate lens is immersed in an ultrasonic bath for a prescribed time during which cavitation (generation and collapse of micro-bubbles) provides a high kinetic energy operation that, in combination with freon solubility (reduced sticking of dust to the mirror surface), removes and floats soluble and insoluble contaminants on the mirror surface. After removal from the ultrasonic bath, it is passed through a constant composition fluorochloroalkane/alcohol vapor zone, which aids in rinsing and drying the lens prior to immersion in the immersion plating bath.

UK patent application GB 2159441 to Liebler et al (assigned to Rohm GmbH) published on 12/4.1985 also describes a method for continuous immersion of scratch-resistant liquid coatings on optical mouldings, for example lenses. It is particularly applicable to an endless conveyor for transporting lens holder frames comprising a plurality of lenses. Among the optical plastic molded parts considered are ophthalmic lenses, of which fig. 2 shows a molded part on which "a lug 10 for clamping is formed, diametrically opposite to the end where the lug is formed, is a drop-off lug 11, so that excess scratch-resistant coating liquid composition will drop off without forming bumps during coating and drying" (97-105 lines). The machine is simpler than the device of the Lalibert, requiring only the loading and unloading stations, the liquid immersion plating station and the drying station (illustrated as "preferably two or more infrared radiators") shown. Not shown but mentioned herein "a cleaning tank may be provided upstream of the immersion tank, such cleaning tank may be, for example, an ultrasonic tank containing an organic solvent" (lines 122 to 128). However, it is believed that the machine of Liebler has never been used to plate ophthalmic lenses in practice, nor has it been used to plate Rx lenses. There are major problems not encountered by Liebler. The lens in his figure 2 has diametrically opposed hanging and dripping blades, which inevitably causes the plating bath effluent to spread from the two junctions of the coated blades at its part. Unfortunately, these spreads occur at locations where the perimeter is disadvantageous because the coating liquid will spread directly through the central region, which is the most important optical zone of sight. Lebler sets are somewhat acceptable, and are believed to be not useful for ophthalmic lenses, but are useful for protective cover lenses in general, such as dishes, utensils and mirrors, none of which require the image transmission necessary for high quality vision correcting lenses. Such plating solution propagation may be harmless and not present functional problems when the hard plating layer is used only to prevent excessive scratches and the protective cover mirror is used only to provide a certain transparency to the article or device. However, in the case of spectacle lenses, vision problems arise due to optical aberrations, and the spread of the plating solution is completely unacceptable and a source of a high percentage of rejects. This problem is absolutely unavoidable if the structure of the sheet, as shown in the figure, occupies the entire thickness of the molded lens. However, if the sheet does not occupy the entire thickness of the lens, as shown in the Werber figure, but is only thick enough to support the weight of the suspended lens, which is quite light, the sheet configuration is acceptable, but only if the lens is held horizontally on its support without rocking back and forth, which is another problem encountered with the Lebler's "carousel".

C environmental and economic problems with cleaning lenses

The "fluorochloroalkane" cleaning is based on the use of CFC-113 (ozone depletion layer) which is now banned from use, and the production of this fluorochloroalkane should be stopped before 12/31 days in 1994, according to the Montreal convention and its EU amendments. Therefore, new Rx lens devices must employ alternative aqueous cleaning methods. An alternative method is to spray water at high pressure (up to 2000 lbs/inch) by moving the lens (e.g., by rotating it about an axis) or moving the spray head (e.g., back and forth) or preferably both the lens and the spray head, to sweep the water across the front and back surfaces of the lens. The spray of high pressure water is particularly effective for removing soluble dust particles from surface soils (e.g., electrostatically attracted polycarbonate dust particles or inorganic dust) and has the disadvantage that this cleaning method is a 100% "line of sight" cleaning method, so that not only can one lens be cleaned at a time, but the typical spin/spray combination requires cleaning one side first, then inverting and returning to a different axis in a manual or automated fashion to clean the second side. The productivity of labor and capital costs (lens products per hour) for such equipment is much higher than that of older chlorofluorocarbon cleaners that were replaced due to environmental regulations.

A second method of aqueous cleaning is to place an ultrasonic aqueous wash solution in the first stage of a counter-current multi-station automated wash line, which is conveyed by a conveyor, passing the lenses through a continuous immersion bath (typically at least 5 stations, preferably 7-15 stations, including deionized water wash).

Whether cleaned with high pressure water sprays or with ultrasonic multi-stage baths, the resulting clean, but still wet, polycarbonate lenses still cannot be immersed in a liquid hard-plating bath (the hard-plating bath is chemically incompatible with any proportion (%) of water, so they face another problem, namely how to remove all residual water from the lens (or its lens holder frame) without leaving surface marks (water spots) on the optical surface of the lens. Since the liquid hard-plating solution cannot withstand the extremely small amount of "carry-in" water carried in by the lens, even a very small amount of water droplets may form streaks or fog on the plated lens, or cause a stained appearance), the use of a hot air circulation dryer (filter-cleaned) is inevitable, which results in a high-cost operation with high energy consumption. The multi-station automated delivery scrubber inline system takes up a lot of floor space, adding to the expense (hundreds of thousands of dollars). In addition, these aqueous cleaning solutions being discharged also pose environmental problems not previously encountered with the use of substituted fluorochloroalkanes.

3. Objects of the invention

For these reasons, it is an object of the present invention to produce a clean, demolded, multi-cavity Rx lens that is ready for immersion plating without the need for shearing or cutting, and without the need for any fluorochloroalkane or aqueous washing procedures, the lens having a suspension (hanging) sheet formed thereon with special features suitable for automated handling and transport.

It is another object of the invention to eliminate the need for operator access to the lens from the time the demolding of the multi-cavity mold is initiated until the hard coating is at least partially cured to a tack-free condition. To minimize dust fouling, it is desirable to completely eliminate the operator from the air space of the same clean room surrounding the lens until the hard coating is at least partially cured to a tack-free state.

Another object of the invention is to increase the productivity by changing the "transfer unit" to be processed from the single Rx lenses of the prior art to Rx lenses moulded together in pairs, which are taken out of the mould ready for automatic processing with shaped suspensions with special parts.

It is another object of the present invention to minimize plastic flash on the edges of the parting line at which the lens pair is formed, thereby preventing immersion plating solution from running off such flash, and/or eliminating the trimming flash operation prior to immersion plating, as such trimming would generate plastic dust contaminants.

It is another object of the present invention to enable clean demolding of lenses with minimal (or no) metal or plastic dust particle contamination during demolding.

It is another object of the present invention to further reduce the cost of producing Rx polycarbonate lenses by replacing the prior art batch process flow with a novel fully automated continuous process flow, thereby increasing productivity, reducing process equipment and increasing labor productivity.

4. Summary of the invention

The present invention employs the principle of "design for manufacturability" that is lacking in the prior art, and the essential element of the present invention is that the transfer unit from the demolding step to the hard-plating curing step is a pair of Rx lenses rather than a single Rx lens. Thus, the output in this manner is effectively flipped over when the automatic transfer is performed. This is not possible in the prior art, which have only a single lens for each suspension.

The third element is to provide a means for forcing using a two-stage spring for a flash-free injection compression molding process that determines the height of the positive displacement mold cavity during the injection and ejection of the molding cycle. (As used herein, "parting line flash" refers to the plastic that escapes from the die set along the parting line formed by the joining of the A, B sides of the die set). This element is only during this last half millimeter compression stroke, since the last millimeter portion of the "closed mold" compression stroke during the injection process is most likely to produce plastic "flash" at the parting line edges of the pair of molded lenses. The elastic force for keeping the mold split mold line closed is greatly increased. Removing the flash may prevent the immersion plating solution from flowing off the flash and/or may eliminate the flash cutting operation prior to immersion plating because the cutting process may produce plastic dust contaminants.

The third element is a novel stripping operation that minimizes or eliminates the generation of dust that contaminates the molded Rx lens. This element is first embodied in the design of the Rx lens piece, specifically the detailed geometry design of the lens edge. Second, the principle of the apparatus must be changed to a mold design that provides the required processing steps for automatically demolding the molded pair of Rx lenses (without manual assistance in demolding) when the mold is fully open and the robot arm with the appropriate jaws is in the proper position for the pair of molded Rx lenses that can be subjected to demolding.

The fourth element of the present invention is that all cutting operations to cure the thermoplastic plastic after demolding until the coating has been applied and cured to at least a tack-free state can be eliminated. The elimination of flash by the modified form of machining (with two-stage spring force) is better than trimming the flash at a later time. Any stripper or drip sheet must be properly positioned along the edge of the lens so that it does not interfere with proper immersion plating and does not spread the immersion plating solution. Specifically, no such plate is disposed in the upper 90 ° angular quadrant (defined as the 10:30 to 1:30 hour positions) of the lens periphery. The Rx lenses in a forming pair must be connected by a cold runner, the runner is positioned in the side quadrant of 1: 30-4: 30 for the left lens, and is positioned in the side quadrant of 7: 30-10: 30 for the right lens.

A fifth element of the invention is that the integral formation is a flap which is located between the two lens pairs moulded substantially equidistant therefrom and stands substantially vertically on the cold runner connecting the lens pairs (the advantage of this symmetry is that the side-by-side tilt of the lens pairs can be minimised). In a preferred embodiment of choice, the head of the suspension formed thereon is located above the uppermost top edge of the lens to be formed in the pair when in the vertical position, thereby preventing the liquid immersion plating liquid from contacting the robot holding the head, so that the length of the bar between the head and the cold runner should be at least sufficiently higher than the above-mentioned top edge of the lens. The rod is preferably sufficiently long so that the second gripping position with the projecting slide stop is also above the top edges of the pair of lenses. (in an alternative, less preferred embodiment, the heads of the molded suspension are positioned below the uppermost top edges of the molded pair of lenses when vertically positioned, and the accumulated impregnated hard coating that sticks to and solidifies on the robot holding the heads is periodically removed during use). Special features are formed on the head to allow it to be geometrically matched to certain robots, workholding fixtures and supports.

The dropping sheet can be selectively arranged in the bottom quadrant (4: 30-7: 30 clock point position) of each lens to reduce the size of dropping marks of the immersion plating solution as much as possible, and after the forming paired lenses are completely withdrawn from the immersion plating tank, the excessive liquid plating solution can be discharged by using the action of a capillary core. However, these selected drop-on-demand sheets suffer from the disadvantage that they require a cutting operation after the coating has cured, and they also increase the amount of polycarbonate resin used per lens and the cost.

These four elements of the invention allow the multi-cavity injection molding of polycarbonate ophthalmic lenses to be integrated with immersion hard plating through full automation, thereby producing clean hard-plated molded lens pairs entirely in a single continuous closed clean room surrounding the lenses, without requiring either the operator or any cutting operations on the molded lenses or runner system prior to immersion plating, and without requiring the use of chlorofluorocarbon (CFC) wash protocols or aqueous wash protocols prior to immersion plating. The inventors' novel combination of lens forming methods, apparatus and molded lens structures used in the manufacturing process can achieve this objective. The enclosed cleaning chamber and automated transfer extensions can optionally provide in-line continuous product flow automated viewing of lens optical power and appearance quality and/or optionally provide in-line continuous product straight-through coating of antireflective films, and then deliver molded and dip coated polycarbonate lenses out of the enclosed cleaning chamber and/or receive manual handling.

Another novel improvement is the use of a special spring loaded assembly of two different types of springs to reduce parting line flash during positive displacement injection compression molding suitable for molding any molded plastic part with a gate in the blank.

5. Brief description of the drawings

FIGS. 1, 1A and 1B illustrate a dual-cavity Rx lens mold of the invention, shown in two split cross-sectional views (different stages of the forming and ejection/demolding steps of the molded lens in a single molding cycle) and a plan view;

FIGS. 2, 2A, 2C and 2D show comparative examples selected from the prior art, with particular attention to the location of the drop marks and the location of exit pieces or gates that need to be cut off before immersion plating and the orientation of the overhang;

FIGS. 3, 3A, 3B, 3C and 3D show the pair of molded lenses of the invention after demolding, with preferred flap positions and stem lengths, and particular head and stem configurations adapted to mate with various forms of automatic clamping positions and workholding fixture mating geometries;

FIGS. 4, 4A, 4B, 4C and 4D show a manufacturing flow diagram showing process steps in block diagram form, with those steps automatically performed in the cleaning chamber shown in dashed box.

6. Modes for carrying out the invention

A. Lens formation and ejection within a module

The present invention employs a novel and advantageous method and apparatus for demolding multi-cavity injection compression molded Rx lenses, the lenses being molded in pairs, each pair having a suspension (see fig. 3), while maintaining the cleanliness of both the molded lens that has been demolded and the optically polished molding surfaces of the mold set, free of metal and plastic particles. Fig. 1, 1A, 1B show a simplified dual-cavity lens module with a nozzle head (not shown) of an injection molding machine injected into a cold sprue bushing (9) and a cold runner system (15) centered between the two mold cavities. An alternative preferred embodiment for molding two or more pairs of Rx lenses in one molding cycle from a single mold set employs a hot runner system that employs a number of hot runner nozzle heads that inject a cold runner sleeve (9) and a cold runner system (15) in place of a single injection molding machine nozzle head; a hot runner apparatus for a four-cavity mold is shown in fig. 17 of applicant's U.S. patents 4828769 and 4900244 (references herein). Another alternative hot runner system for optical thermoplastic molding is shown in applicant's U.S. patent 4965028, which is incorporated herein by reference. Cold wells (40) are preferably formed in the cold sprue and cold runner system to trap "cold material" before it reaches the lens mold cavity.

It should be noted that forming a slight undercut (41) or negative draft angle on the cold well (40) provides a strong mechanical retention, which is useful in subsequent demolding steps.

Another alternative preferred embodiment for molding pairs of Rx lenses in a single mold set employs "positive-displacement" mold cavities wherein the height of the mold cavity beginning prior to injection is greater than the thickness of the final molded lens. Such "positive-displacement" cavity module apparatus typically employs an injection compression molding process to mold Rx lenses, wherein the injected melt is squeezed with a driving force at some time after the injection begins to reduce the cavity height (see the arrangement of driving forces and sequences in the cited prior art lens molding patents). One preferred arrangement, shown in applicant's U.S. patents 482876 and 4900242, employs elastomeric member 13 (e.g., a hydraulic cylinder or mechanical spring) of fig. 10B to determine the mold height such that when elastomeric member 13 is extended or uncompressed, the cavity height is made greater than compression stroke length 40, and when elastomeric member 13 is contracted or compressed (e.g., preferably by increasing the molding clamping force applied by the injection molding machine before injection is complete, causing the platens to simultaneously compress), the compression stroke length (40) is made zero, thereby reducing the mold cavity height. Referring to FIGS. 2-8, the sequence of the injection compression process is shown during a complete molding cycle.

The applicant has found that since the filing of the patent, the use of hydraulic cylinders as the resilient member 13 in polycarbonate Rx lens molds is disadvantageous because such molds operate at very high temperatures (240-295F; 120-150 c) and cause leakage and oil fouling of the part molding surfaces. The use of conventional coiled (disk) die springs as springs does not have this problem, and has a long life, and allows for a large compression stroke length (up to 0.400 inch or 10mm lengths have been used to mold very high negative power Rx lenses with center thicknesses of 1.0-1.5 mm and edge thicknesses of 10-14 mm with minimal "knit lines"). However, the elastomeric member also has the problem of "flash" formation during mold injection; to eliminate the parting line "flash", the spring force clamping the parting line must exceed the melt pressure exerted by the melt on the raised area, and it is typically time to form such flash at the last 0.1 to 0.5mm of the compression stroke. Parting line "flash" (i.e., plastic that spills over the die set along the parting line at the junction of the sides of die set A, B) must also be eliminated or minimized or otherwise cut out (thereby creating particles) or allow for the spread of the liquid immersion plating solution prior to immersion plating. The use of extremely strong, high compression force mold coil springs as the resilient member solves this problem by creating a different problem during the ejection of the molding cycle, since this high spring force acts like a slingshot on the lens and the chill gate by prematurely pushing forward the parting line molding surface before driving the ejection mechanism of the injection molding machine once the clamping force is released in preparation for opening the mold.

The present invention preferably uses a novel combination of two different types of die springs in the die set to enable these "springs" to form a two-stage operation. As shown in fig. 1 (split die cross-section showing the state of the spring being loosened by, for example, loosening the die clamping force applied by the injection molding machine during the ejection of the operating cycle), a conventional steel die disc spring (25) is used in conjunction with an extremely strong Belleville type spring washer, the disc (25) having a long compression stroke and a moderate biasing force, the washer being a superimposed assembly with an extremely strong biasing force, held in place by shoulder bolts (29), providing two different die spring forces at different stages of the stroke, i.e. the Belleville spring assembly with an extremely high biasing force dominates when the opening and final closing movement of the die is between 0.0 and 0.5 mm; only the weaker mold coil spring (25) then exerts a spring force giving a controlled mold opening stroke (too high a spring force will almost eject the pair of molded lenses held only by the retainer 41 from side B). At the same time, the resilient member determines the positive displacement cavity height for each molding cycle, thereby establishing a compression stroke length (21) up to a maximum height determined by the shoulder bolt (29). In this alternative preferred embodiment of the invention, the sequence of the injection compression process is the same as that shown in FIGS. 2-6 of Applicant's U.S. Pat. Nos. 4828769 and 4900242, but then is different (unlike FIGS. 7 and 8) in how the Rx lens is demolded and ejected. For flash-free injection compression molding, the use of two-stage spring loading forces greatly increases the spring force that closes the mold split parting line only during the last half centimeter of the compression stroke. This process can be automatically changed to the sum of the two spring forces when a large spring force is being required, i.e. when the compression stroke of the closing mold reaches the final part of 1mm during the positive displacement mold injection process.

The applicant's two-stage spring-loaded combination (strong spring acting only for short strokes and weak spring acting over longer strokes) is an improved form of elastomeric member operating in such positive displacement injection compression molds, the cavity height in the mold being determined by the extent of the spring extension. The prior art cited herein and the prior art cited in applicant's U.S. patents 4828769 and 4900242 have not addressed this two-stage spring-loaded combination nor do they address the effects. In particular, any molded part with a binder ingate molded in a positive displacement injection compression mold whose cavity height is determined by the degree of spring elongation tends to produce parting line flash, which is more problematic the larger the projected area of the cold runner system (particularly if a large fan gate or full length runner is used). If the article is flat or the melt flow path length is short, then a very short compression stroke length (0-1 mm) can be used, which is satisfactory with a single extremely strong spring, thus eliminating the need for the applicant's two stage spring loading combination. However, if the article is not flat and has a large melt flow path, a long (> 1mm, usually 2-10 mm) compression stroke length must be used, and it is not satisfactory to use only a strong spring. The applicant's novel two-stage spring-loaded combination is now applied to control burr generation. Such other articles may be other precision optical lens articles (e.g., light magnifying LCD lens arrays for flat displays, many optical microstructured surfaces replicated by molding including "binary optics", "hybrid optics", fresnel and holographic imaging) and molded windows, headlight lenses and mirrors, but may also include similarly shaped, fringe-free, non-optical, opaque injection compression molded parts, such as large exterior body panels (hoods, doors and bumpers) and textured interior panels in the mold. All of these non-ophthalmic lens applications have been studied and variable volume injection compression molding has been used as is well known. It is believed that the burr problem has somewhat hindered practical applications. The applicant has recently investigated this positive displacement injection compression molding process using and without the novel two-stage spring-loading combination, and these studies have clearly demonstrated the claimed flash-resistant advantages.

The injection compression molding process for reducing split fluff flash on at least one molded thermoplastic article may be carried out in a mold block which is mounted in an injection molding machine having program control means for applying clamping and opening forces to a parting line formed between the sides of the mold block A, B and program control means for moving the ejection assembly back and forth within the B side of the mold block. The mold block has at least one edge-gated positive-displacement mold cavity forming part-forming surfaces on opposing pairs of a-side inserts (core cores) and B-side inserts facing the parting line, and at least one passive elastic member of variable extensible and compressible length determines the height dimension of the mold cavity within a predetermined mechanical range. The elastic element is an operational combination of the following springs:

i) a steel die coil spring providing a moderate spring force over a long distance of the die set first clamping position;

ii) stacked steel spring inserts of the bellenle type providing a strong spring force within a short distance of said die set second clamping position;

the resilient member is mounted between the B-side parting line die plate and the B-side clamping plate of the die set and applies a combined spring force to the parting line to bias the B-side parting line die plate forward. During injection compression molding, the spring length is maximized within a predetermined mechanical range of the first clamping position of the die set when the clamping force applied by the injection molding machine is less than a first spring force equal to the spring force of a forward parting line biasing the B-side parting line die plate against the steel die disc (wrap) spring alone.

The length of the resilient member reaches a value intermediate the second clamping position of the die set when the clamping force is greater than a first spring force equal to a forward parting line biasing spring force of the steel die disc spring acting alone but less than a second spring force equal to a forward parting line biasing B-side parting line die plate spring force of the steel die disc spring and the steel spring liner acting in combination.

The spring length is at a minimum within the predetermined mechanical range of the third clamping position of the die set when the clamping force is greater than a second spring force equal to a spring force of a forward parting line biasing the B-side parting line die plate forward of the steel die disc spring in cooperation with the steel spring liner.

The method comprises the following steps:

a) substantially closing the periphery of the mold cavity along the parting line, thereby pre-enlarging the mold cavity such that production of thermoplastic flash is prevented in a first position of the mold set formed by application of a clamping force equal to a first spring force, thereby determining a first mold cavity height prior to injection, the height being equal to the desired compression row length plus the final thickness of the molded article;

b) partially filling the mold cavity after injection firing by gradually reducing the height of the mold cavity at a second position of the mold assembly, the second position being formed by applying a similar tightening force exceeding the first spring force but less than the second spring force;

c) gradually reducing the height of the mold cavity further after the injection is completed to a third position of the mold set, thereby completely filling the mold cavity, the third position being achieved by applying a clamping force exceeding the second spring force;

d) cooling said molded article in the mold cavity after the injection is complete by maintaining the applied clamping force in excess of the second spring force such that the mold cavity height substantially maintains the third position of the mold set until the maximum cross-section is below the characteristic glass transition temperature of the thermoplastic;

e) the clamping force is released and the die set is opened along the parting line to eject the molded article.

According to the present invention, once the optical grade thermoplastic cools to at least the glass transition temperature (polycarbonate is 296F.) even at the final cross-sectional portion, the final molded lens should be shape stable (the plastic molecules have a memory function). Because increased heat transfer rates between the cooled melt and the mold insert can increase molding productivity, it is desirable to use copper-based alloys with high thermal conductivity as the material from which the mold insert is made and to plate the molding surface of the optically polished part with a hard chrome or nickel surface. One such example of use in optical molding is in applicant's U.S. patent 4793953 (herein incorporated by reference). Further improvements in optical molding thermodynamics are provided in Applicant's United states patent 5376317 (incorporated herein by reference) which uses such high thermal conductivity copper-based alloy mold inserts with the surface of the insert at the beginning of a mold cycle at a temperature above the glass transition temperature, then fills the cavity, compacts and lowers the mold temperature to well below the normal scorching temperature (240-295F; 120-150℃) for molding Rx polycarbonate Rx lenses.

The first step in demolding and ejecting the pair of lenses is to release the clamping force applied by the injection molding machine, thus releasing and elongating the elastic member comprising the above-mentioned united spring. Referring to the right side broken away view of FIG. 1B, it shows that the molded lens (16) has been separated from the optical polishing element molding surface of side B core insert (14), forming a disengaged space (17) between the lens 'concave surface and the insert's convex surface forming the concave surface. The modular spring is extended or not compressed by releasing the clamping force applied by the injection molding machine during the very beginning of the withdrawal time of the operating cycle, the disengagement space (17) being substantially equal to the size of the compression stroke (21). At this point, the beveled sleeve surface (19) forming the lens edge can assist in releasing the mold cavity bore (sleeve 20) surface by thermal shrinkage of the molded lens. Significantly, if zero tilt is applied to the holes forming the lens edge, as is common in the prior art for making current Rx polycarbonate lenses, these lens segments may become firmly stuck to the B-side mold insert (14) by the partial vacuum which pulls the lens backwards as the spring-loaded parting line B-side mold plate (28) is moved forward (relative to the B-side mold insert). The applicant has seen examples where the gate, which is still hot, is stretch-bent or, worse still, torn, leaving the lens stuck to the B-side insert deep within the hole. Creating some positive tilt on the B-side sleeve can create a mechanical interference that can prevent the possibility of the lens being pulled back into the hole.

See fig. 1B. It should be noted that even though the movable platen has moved forward, the parting line (C-C cross-sectional plane) has not yet fully opened (compare the module height measured between the class a clamping plate (25) and the B clamping plate (23) with the left hand split view representing the fully clamped state). When the parting line begins to open, the molded pair of lenses, with and without selective blowing, have already broken free from the B-side and have dragged out the optical burnishing element molding surface of the a-side female insert (13) because the cold sprue (18) and cold runner (15) that mold the pair of lenses remain firmly secured to the ejection mechanism (not yet actuated) with a conventional retainer (41) (which is a controllable angle of inclination on the sprue well (40)), thereby "gripping" the pair of molded lenses (16) on the B-side. (in addition, careful control of the cooling temperature on the B side below the A side temperature causes greater shrinkage of the molded lens on the B side, and thus reduces the holding power of the A side lens).

Referring to fig. 1, the parting line opens as the mold of the injection molding machine continues to open after the maximum forward stroke of the spring-loaded B-side mold plate (set with shoulder bolts (29)) is reached. Once A, B are no longer held together, the mold opening motion will automatically apply a peel force that will exceed the partial vacuum that may exist between the convex surface of the molded lens and the corresponding concave mold insert surface forming the convex surface, since the molded lens pair is still held by the mechanical retainer (41) on side B of the movable platen of the mold set. As long as these B-side holding forces exceed the forces required to secure the lens to the a-side insert and do not exceed the adhesive strength of the plastic in the cold runner and sprue, the lens can be mechanically released from the B-side with certainty when the parting line is fully open during mold opening.

The pair of molded lenses (16) and the connecting cold runner system including mechanical retainers (41) are then disengaged from side B as shown in fig. 1 by conventional ejector pins (4) driven by the motion of the hydraulic ejector cylinders (not shown) of the injection molding machine integral with the mold set ejector plate (24), the ejector pins 4 being mechanically integral with the ejector plate (24). The lens can be peeled off the side B by mechanical means. This step can only be performed when the module is opened along the parting line. The timing of the ejection movement is initiated after the gripper arm end of the automatic take-out machine is brought into position to receive the lens while the lens pair is being formed off the mechanical holder. This timing control can be adjusted between the injection molding machine and the programmed control of the automatic take-out machine with the detection feature that can confirm that the take-over has been completed. There are currently a variety of brands of automatic take-out machines available for use with plastic injection molding machines. Side-entry machines are preferred over the more common "up-out" rectilinear machines because the space on the die platen is preferably where the downward facing HEPA filter is located, and because the enclosed cleaning chamber can be made smaller and more compact if a side-entry machine is used. Typical manufacturers of side-entry automatic take-out machines are Ranger Automation, Inc. of Shrewsbury, Mass, Conair Martin, Mass, and AutomatedAssembies, Inc. of Clintoon, Mass.

It should be noted that the above-described ejection sequence differs from the conventional method of ejecting a plastic part from an injection molding die by first stripping the molded part from the concave surface of the part being molded, and holding the molded part on the surface of the core of the part being molded as the die begins to open. After the mold is fully opened, the molded part is accessed and released from the part-forming core surface, either by a robot arm or manually.

In an alternative embodiment of the invention, filtered compressed air is used in a step-specified "blow-through" sequence to provide a supplemental driving force to separate the molded lens from the optically polished part-forming surface, as the natural vacuum created by the thermal contraction causes the mirrors to cling to the part-forming surface as the thermal contraction occurs while the mold seal and clamping force are maximized. While the use of a compressed air stream to assist ejection is generally not new to those skilled in injection molding thermoplastics, the applicant is not aware that it has been used in the molding of optical lenses and is not seen in any of the prior art in this regard. Refer to fig. 1B. The applicant applied filtered compressed air (in order to maintain the purity of the part-forming mould surface and the formed lens surface) introduced with a-side air tube (10) and a B-side air tube (11) to the clearance (12) formed between the outer periphery of each cavity insert (a-side cavity insert 13 and B-side core insert (14) and the bore of the sleeve 20 surrounding the periphery), an air valve (not shown) controlling the air flow and pressure in the air tubes (10) and (11) providing an air flow in the ejection process, which air flow is operated in conjunction with a conventional ejection pin (104) driven by the movement of a hydraulic ejection cylinder (not shown) of the injection moulding machine integrally connected with a module ejection plate (24), which ejection pin is mechanically integrally connected with the ejection plate (24).

In an alternative preferred embodiment of the invention, filtered compressed air is fed into these channel gaps (12) of only "vent gap" size (0.001 (0.0245mm) gap for a carbonate lens without "flash" occurring even before the parting line opens) so that the pressure of the air begins to act on the B side (core side) of the movable platen around the periphery of the male insert and inwardly toward the center of the lens, thereby cleanly separating the lens from the male part molding surface of the B side insert. At the same time, the beveled surface of the lens edge assists in detaching from the cavity (sleeve 20) bore surface by thermal shrinkage of the molded lens. To facilitate the release of the paired lenses from the stationary platen (a-side) of the mold prior to opening of the parting line, in an alternative preferred embodiment of the invention, a second stage air flow may be initiated in which similar compressed air enters around the periphery of the circumference of the optically polished a-side mold insert and drives toward the center of each lens, breaking the partial vacuum formed during molding. At this point, a substantial seal is maintained by a small edge seal overlap (42) of the anterior portion of the lens that overlaps the peripheral edge of the lens cavity. If such a minimal seal overlap (42) is omitted, the air flow force will be weaker and less effective, as the air flow will by-pass the center of the lens along the path of least resistance and leave some partial vacuum that will hold the molded lens in place during the next stage of ejection by stripping the lens from the concave insert surface with the mold's gripper opening stroke while the molded lens is being held firmly on the ejection device that moves with side B of the mold set, see fig. 1B.

B. The cured plastic is not cut prior to immersion plating to maintain purity.

Immersion plated lenses of various polycarbonates are edge-gated in nature and are hard-coated with a smooth film on which "drip marks" (formed by the flow of the liquid hard-coating solution under gravity along the front and back surfaces of the lens) are readily visible. To test this Rx lens, we can look at the molded hard coated lens and find the location of the drop mark (easily visible as the raised portion (37) of the relatively thick hard coated smooth film, as shown in fig. 2C). When set to a clock face, we can autonomously designate the position of any lens drop at the 6 o' clock position. The lens was then inspected for wall wrap from drop mark to end and we would see if any exit piece was used and if an exit piece was used we would also see if the cut was made before or after immersion plating because if the cut was made before immersion plating, a smooth coating would form on the cut/remnants in addition to the gate remnants.

Lens samples tested were taken from commercial, Gentex and Neolens company lens samples typically exhibited one or more exit sheets, generally at a 180 ° angle relative to the gate. There were four such exit pieces and gates for the samples of neolense, all of which were removed prior to the cleaning and dip plating operations (like the comparative example of fig. 2).

The reason why some lens edge locations are not allowed to have a release sheet during immersion plating is that the liquid plating solution on the upper half of the lens will flow downward under gravity from the end of the release sheet to the lens edge, and that this liquid immersion plating solution will flow vertically downward from the peripheral location of the release sheet along the front and back optical surfaces of the lens. These "bath flows" will cause uneven light refraction (i.e., images of aberrations will be seen through the accumulated thicker coating) and thus cause defective final lenses. If one or more exit sheets must be cut from the formed polycarbonate lens prior to immersion plating, this not only increases the variable cost per lens (more resin per lens, additional labor costs for the operator to carry out the transfer and cutting operations), but also directly reduces the purity of the newly formed lens. There is no method available to cleanly trim the cured polycarbonate plastic without generating fine dust particles ("polycarbonate dust") that quickly reattach to the front and back optical surfaces of the polycarbonate lens because the electrostatic attraction attracts the dust particles and causes them to adhere to the high dielectric constant polyester surface layer. Blowing de-ionized air flow can minimize this electrostatic attraction, but practical inspection of newly formed lenses with an electrometer shows that the lenses have a static charge of 5-30 KV, which can only dissipate very slowly (within minutes, not seconds) due to the excellent electrical insulation of polycarbonate.

Even if no ejected sheet is cut during immersion plating, these degating and/or gating operations can produce fine polycarbonate dust that smears the surface if degating is necessary so that it can be hung from the lens holder frame by the hanging sheet molded thereon (see comparative example of fig. 2), or if the cold runner is cut so that it can be inserted into the lens holder frame by the hanging sheet molded thereon (see comparative example of fig. 2A). And all of these obviously require manual handling by the operator between the forming and immersion plating steps. After cutting and mounting on the lens holder frame, these polyester lenses are cleaned to remove soluble contaminants (e.g., oils) and insoluble fine particle dust (e.g., inorganic dust, and most troublesome fine polycarbonate particles resulting from the cutting, degating and sprue cutting operations).

Allowing the lenses produced with applicant's us patents 4828769 and 4900242 to be produced without any exit sheet as evidenced by inspection of the lens edge. However, if the injection molded unitary piece (many lenses connected by a cold runner melt delivery system) must be cut to fit on the lens holder, these runner removal operations can also produce polycarbonate dust, which is also an undesirable result. The statistically largest source of defects is the defect known as "clear spots" in the coating, where transparent and translucent particles of sufficiently large size and location to affect the line of sight are sealed in a smooth mold formed by liquid immersion plating. It is clear that such economic losses and rejects can be reduced to some extent by using intensive washing and multistage dilution. However, even with the best cleaning agents today, this defect is the largest source of defective lenses.

Refer to fig. 1A. The lenses of the invention formed into pairs do not have any overhangs in the upper 90 quadrant (6) between the 10:30 and 1:300 hour positions and gates are formed in the right and/or left quadrants (5) and (-5) (for (5) between the 1:30 and 4:30 hour positions and for (-5) between the 7:30 and 10:30 hour positions), which would be in the lower quadrant (7) (between the 4:30 and 7:30 hour positions) if the lenses were drop cast (optional, not shown). The open spring configuration of the hanger bar and head shown in more detail in the example of fig. 3 can also be seen.

Reference is now made to comparative examples of fig. 2, 2A, 2C and 2D. It should be noted that contrary to the cited prior art, the lens periphery of the applicant itself (see fig. 3) does not have any escape sheet and therefore most particularly no sheet at any location that needs to be cut before dip hard-plating.

The comparative example of fig. 2 shows a simplified dual cavity lens mold with a cold sprue and runner (32). It should be noted that each lens has a plurality of ejection tabs and gates, each of which is cut (33) in a separate operation after molding and prior to immersion plating and using a "T" shaped tab (34) molded thereon. The prior art patent closest to the comparative example of fig. 2 is the Weber patent (us patent 4008031) with the only difference being that the T-shaped suspension 20 of Weber is directly opposite the gate 25 and has exit tabs on each side of the suspension 20. Weber requires the removal of a gate into the drip sheet 23 prior to immersion plating.

Bakalar U.S. patent 4644854 assigned to Neollens corporation, in FIGS. 4 and 5 thereof, shows the use of an ejector pin (15) against the gate, without any overhang molded thereon. In practice, the molded lenses of Neolenses have a number of ejector blades and pins that need to be cut prior to immersion plating, arranged much like the comparative example of FIG. 2, and therefore need to be cut to finish the lenses for immersion plating using an unknown shaped suspension blade (34) in its position shown in FIG. 3.

U.S. patent 4933119 to Weymouth, assigned to Gentex corporation, does not show any ejector pins or ejector blades and does not describe any method of demolding or ejecting the molded lens. Therefore, the operator only thinks that he should take out the molded lens by hand. In this case, a large amount of dust particles must be adhered to the demolded lens. All Genter's Rx lenses showed at least one notch per lens (the notch was coated with a smooth film) prior to immersion plating.

The comparative example of fig. 2A shows a simplified four-cavity lens molding with a cold sprue 18 'and runner 35 mounted on each lens of two pairs of lenses, each pair having a sprue 15'. Even though the closest prior art (applicant's U.S. patents 4878969 and 4900242) was made with two pairs as shown rather than four individual lenses, and even though molded clamping and retention features were added to the runners of each pair of lenses, there was no method of immersion plating after demolding of the lenses without at least two cuts (33) to separate the four-cavity integrally molded part into 2 pairs.

Other limitations exist with the applicant's U.S. patents 4878969 and 4900242. See fig. 6, 7 and 8 thereof, wherein the resilient member 13 is held in its compressed or contracted position such that when the injection molding machine with the parting line fully open pushes the ejector plate 17 forward, the B-side insert 5B is pushed forward through the parting line plane, as shown in fig. 8, and pushes out the molded optical lens or picture, as shown. This Rx lens ejection method is not desirable for in-line molding and immersion plating process configurations employing the present invention. This back and forth movement of the B-side insert in a tight fitting hole, where fine single vision lenses of high negative power of at least a few millimeters are easily available to an edge thickness of 10mm, must cause wear between the metals and produce scratching (scratches are visible when viewing the molded lens edge, as evidenced by visual inspection of the molded lens edge produced by this "moving insert" ejection method of the applicant's patent (produced by the patent thermo-irradiator). The abrasion that must occur between the metals will produce extremely fine metal particle contaminants that deposit not only on the molded lens but also on the component molding surface of the optical molded article, and also on the component molding surface of the optical molded article, thus producing an appearance defect in the dipped article. Secondly, if severe scratches occur, the uneven surface shape created in the cavity-side wall-forming holes causes molten plastic to enter these very fine scratch gaps, which will be sheared during the application of the withdrawal force (pushing the moving insert forward), thus creating fine plastic particle dust, which in turn causes additional dust contamination of the molded lens and molding surface. For this reason, the moving insert method has been found to be unacceptable for the in-line forming and immersion plating process of the present invention.

Referring now also to the applicant's U.S. patent nos. 4878969 and 4900242, it should be noted that in fig. 9B thereof, the drip sheet (99) is located at the 6:00 clock position of the molded lens, but even if there is a method to separate the two molding pairs shown without cutting out after the plastic has solidified, the small cold well (31) cannot be set too high for cleaning the lens edge to serve as a holder or flap for immersion plating, while the robust gate of the cold runner cannot be separated without a severing operation that would cause contamination of plastic dust particles.

The comparative example of fig. 2C shows a typical prior art single lens with the plate (34) in the 12:00 clock position. If the immersion stroke is imprecise and the lens is not just dipped to the top edge of the lens but is dipped deeper, partially onto the stem of the sheet, the liquid will run down the stem under gravity, thus causing a backflow (38) of liquid onto the optical surface of the lens. Reducing the thickness of the plate and spacing the plate (34) some distance from the two mirror surfaces can minimize, but not completely eliminate, this phenomenon. One such example is U.S. patent 4008031 to Weber.

The comparative example of figure 2D shows a single lens of the british patent GB 2159441 a of the prior art Liebler, with the plate (34) having the thickness of the lens at the 12:00 clock position. Referring also to fig. 2 of Liebler, which is taken from this fig. 2, lens F has a lug 10 and a drip piece 11. If the immersion stroke is too inaccurate (which is not possible with the immersion of the lens using the Liebler's endless conveyor), the lens must partially dip onto the stem of the sheet and then the liquid flows down the stem under gravity, causing a large amount of liquid to flow back (38) onto the optical surface of the lens.

C lens edge detail design facilitating cleaning ejection

Turning now to the applicant's fig. 1, this figure shows the draft bevel surface (19) of the cavity bore which forms a detail of the lens sidewall. In an alternative preferred embodiment of the invention, the angle of inclination of this surface is positive compared to vertical (zero inclination). The tilt angle should generally increase in value proportionally to the increase in thickness of the lens edge. It should also be noted that the addition of a small flange formed on the lens to act as an edge seal (42) (see fig. 1B) at the junction of the convex surface and the side wall of the lens edge (typically not more than 0.5mm per side is sufficient) facilitates compressed air blowing, which is optional but preferred in the present invention.

Molded or cast Rx lens blanks are sold in the market at nominal diameters rounded to an integer millimeter. Since all cast or molded plastic spectacle lens blanks are subsequently cut to their periphery so that they can be fitted into the particular spectacle frame chosen by the patient's prescribing physician, all Rx lenses should basically be designed to fit into the matching spectacle frame. Dead zones consisting of a peripheral band 5mm wide around the lens edge can be generated from experience due to various stains and defects (e.g., bubbles or voids in the former, and vestige bond lines or stains in the latter) that accumulate on the edge of cast Rx lenses and plastic molded lenses, or due to defects (e.g., drip marks) created by immersion plating. Thus on a 76mm nominal diameter lens blank, only the inner 66mm can be used when subtracting the unused 5mm area on each side for configuration purposes.

The present invention takes advantage of the fact that there is a dead zone to alter the detail of the edge and sidewalls of the lens article to improve manufacturability. Refer again to FIGS. 1, 1A and 1B. Specifically, in an alternative preferred embodiment of the invention, the inventor provides a plurality of interchangeable sleeves (20) that can be selected to have different sloped surfaces (19) to be assembled with appropriately matched male inserts (14) to form lenses of various powers to provide for the cleanest ejection of the formed lens pairs without the generation of solid metal or plastic particles during ejection. None of such sleeve bevel angles or surface geometries are optimal for all Rx FSV lens molding because the bevel angle or surface geometry must cover a wide range of article geometries. If the downward slope angle along the cavity bore forming the lens sidewall and the sleeve sidewall is too steep, considerable play may be formed between the sleeve and the insert, resulting in "flash," which is unacceptable. The FSV positive and negative power lenses to be formed in series require mold designs that are tailored to the widely varying thickness of the lens edge. Magnifying lenses of positive power (correcting hyperopia with distance) typically have a minimum lens edge thickness (2.0-0.8 mm). In contrast, negative power lenses (for correcting myopia) have relatively thick edge thicknesses (2.0-12.0 mm). Creating a zero tilt angle at the edge of the thickest lens can be problematic. However, the prior art patents do not show any such means for varying or adjusting the tilt angle, as the tooling of the die becomes more and more complex. In practice, measurements on some markets may be confident that the Rx lenses produced with the cited prior art patents demonstrate zero tilt angles and that the lenses can be pushed out with a "power" despite the high retention within them. This practice also increases the likelihood of intermetallic wear and shearing between the metal and plastic. This abrasion and shearing will produce solid particles that contaminate the surface.

As shown in fig. 1A and 1B, the present invention employs an interchangeable mold sleeve (20), which is the part molding surface that forms the edge of the lens sidewall. By replacing a set of sleeves having a predetermined bevel surface (19) with another set of sleeves having a different predetermined bevel surface/angle, and by inserting them into corresponding B-side inserts for a particular desired FSV negative power lens, the bevel angle of the pair of lenses can be controllably increased or finished within the FSV lens range to achieve the cleanest molded lens upon demolding. The thicker the lens edge and the higher the corresponding negative power, the greater the tilt angle that should be applied, but preferably only on the sleeve, formed partially downward. For example, a lens with a power of-2.00 has an edge thickness of 4.2mm, which can be cleanly demolded with only a 1.9mm beveled edge. In contrast, an FSV lens with a curve power of-5.00 mm had a nominal edge thickness of 14.6mm and the bevel edge to be cleaned and demolded increased to 7.2 mm.

D. Sheet design for molding on lens adapted for automated operation in immersion plating process step

After the molded lens having the aforementioned features of the invention is formed and cured in the aforementioned multi-cavity injection compression mold of the invention, the demolding is conducted in a closed clean room preferably maintained at a positive pressure (relative to atmosphere) with a HEPA blower. There is a need for an automatic take-out machine, preferably of the side-entry type, not "up-out" type, having the modular blower delivering HEPA filtered air directly above the platens on the molding machine, to preferably maintain positive air pressure in a closed clean room that substantially surrounds the mold (a predetermined gap below the mold for venting may improve the down-flow laminar flow pattern; likewise, a bottom gap for directing the vented gases is preferably below the immersion plating machine).

The side entry automatic take out machine operates in a closed clean room tunnel between a closed mold and a closed HEPA filtered automatic immersion plating machine. When the mold is opened along the parting line and the arm of the side entry automatic take out machine is moved into position, each pair of lenses is pushed forward against the gripping jaws of the gripper arm end mounted on the side entry automatic take out machine arm. In an alternative preferred embodiment, the automatic immersion plating machine has a positive pressure HEPA filter in its housing that filters clean room air, the immersion plating machine being located between two such injection molding machines and a multi-cavity mold, two such side entry automatic machines delivering pairs of lenses into the automatic immersion plating machine. This "two-wire" in-line system is an economically preferred embodiment relative to transfer from a single molding machine and mold to a single immersion plating machine because typical Rx lens molding cycles are quite long (between 1-5 min depending on the magnification of the Rx lens and corresponding molding thickness). For lenses with longer cycle times, the two-wire configuration solves the problem of the molding step forming a bottleneck, thus increasing the productivity per unit of equipment investment.

FIG. 4B shows a block flow diagram of the steps of the present invention performed in a single enclosed cleanroom (shown in phantom, showing all steps performed within the confines of its cleanroom space).

The robot or immersion plating machine has many conventional forms and its automatic conveyor can be driven using a chain driven conveyor (single or parallel operated, connected in parallel by a crossbar on which the lens holder supports are suspended) or a rotatable overhead conveyor or a moving bar conveyor. Alternative preferred embodiments employ programmed SCARA cylinder machines manufactured by IBM, GMF Fanuc, and Seiko corporation. Such SCARA robots should have a working range of suitable dimensions (typically 270 ° rotation and at least 100mn movement along the Z axis) to allow transfer of these formed pairs of lenses from a transfer point somewhere within the coating machine sealed cleaning chamber to at least one hard coating bath, where the immersion time and withdrawal speed can be controlled using a computer program, and then transferred to a fixture that is part of the curing station equipped with a conveyor.

Figure 3 shows a shaped pair of lenses with a suspension (1) comprising a stem (3) and a head (4), coming from a side-entry automatic extraction machine, directly or indirectly transferred to a second automatic device. It should be noted that the broken line (39) represents the liquid level of the immersion plating liquid, and a portion below the line (39) is immersed in the hard plating liquid. It should also be noted that the contoured surface (50 is the lead angle chamfer, 52 is the recess stop, and 53 is the lead angle) that matches the horseshoe-shaped head of the workholding fixture is preferably located above the fluid level (39) so as not to contaminate downstream areas where mechanical engagement might remove the plated layer.

Reference is now made to fig. 3D. The second receiving robot is preferably a programmed SCARA cylinder robot arm with a pivoting wrist (not shown) that pivots (70) about an axis (69), and with pairs of gripper fingers (43 on the left and 60 on the right) that are programmed to move simultaneously to grip and release. Refer to fig. 3C. While the jaws are cut to a generally mirror image of the head surface profile (50 for lead angle bevel, 52 for recess stop, 53 for lead angle), there is an additional gap (63 for vertical and 62 for horizontal) that provides inaccurate "pass-through" when transferring the formed pair of lenses from one station or operation to another. These gaps allow for slight mis-alignment or positional errors, even if any, to properly complete the pick-up or delivery.

The gripping orientation shown in fig. 3C illustrates how the SCARA robot grips the lenses formed in pairs during the lowering and operation of the immersion plating step, after which the wet lens is placed on one of the multi-piece gripper arms having a generally matching mirror-imaged "nest" with an inclined face (50'), a stem portion gap (57), and a stem retaining step (58), and a stem gap (56) as shown in fig. 3B. Such a work holder is then used to automatically transport the wet lens through the drying and curing steps. Such an automated transfer device may be a conventional conveyor, but in an alternative preferred embodiment, a rotary drive mounts a plurality of such work holder arms as a carousel within a curing station.

The gripping direction shown in fig. 3D illustrates how a SCARA automated machine grips pairs of molded lenses during insertion of the heads into a lens gripper frame or similar gripper, wherein the receiving nest (not shown) has a convex surface for mechanical interference with the surface of the head stop (52) to prevent easy disengagement of the heads during transport. Subsequent insertion requires the automatic machine to apply a pushing force to the head in the axial direction of the rod, so much as to deform the spring, i.e. the leading inclined surface (53) facilitates this frictional fit, because of the spring relief (51) (the greater the relief and the thinner the legs, the easier it is to deform the horseshoe spring.

Another alternative preferred embodiment employs an intermediate step of automatically placing the formed pair of Rx lenses into a circulating filtered alcohol bath and holding it there for a predetermined time to accomplish the following functions:

1. destaticizing (measurement of meter charge by an electric field instrument before immersion indicates that the lens still has a static charge of at least 4-10 ev even after blowing with an ion suction fan for a predetermined period of time; after immersion in an alcohol bath for at least two minutes, no surface charge is actually measured on the lens);

2. heat dissipation (immediate after demolding, as measured by a non-contact infrared pyrometer, the temperature of the polycarbonate Rx lens is typically 250 ℃ F. or higher; depending on the dwell time and the temperature of the alcohol bath, it may be lowered to 120-60 ℃ F. to the temperature required by the solvent components of the liquid immersion plating bath, thus preventing the formation of "solvent burn" on the surface of the polyester lens.

3. Low kinetic energy washing and rinsing (soluble organic surface residues and slightly attached insoluble microparticles can be removed with running alcohol).

The advantages of using such an alcohol bath are particularly evident if the hard-plating solution is solvent-borne, since such solvents typically attack freshly formed hot (250F (125 c) or higher actual temperature of the polycarbonate lens surface as measured by a non-contact infrared pyrometer) polycarbonate lenses, thereby producing an etched or partially dissolved surface layer, i.e., both surface damages cause optical defects. At room temperature, the same plating solution may not damage the lens. The problem is therefore that cooling in air is required for several minutes, during which even polycarbonate lenses, which have been reasonably well destaticised of static electricity, still have a relatively high surface charge (typically 3KV) and can therefore attract the dust which is additionally agitated by the local hot air flow generated by the hot lens, even in HEPA clean rooms, so that the hot, clean lens gradually becomes a cold, but less clean lens. Dipping the hot lens pair into the alcohol bath as quickly as possible, the lenses can remain clean, but the heat can be removed quickly (reducing the number of lenses in the cooling stage prior to immersion plating, making the apparatus more compact) and the surface charge drops to zero. Preferably, the pairs of lenses are automatically placed in an alcohol bath for a period of minutes with a stainless steel lid that is made to "nest" as many matching heads as needed (as shown in fig. 3B), i.e., the longer the immersion time, the greater the number of nests and the larger the bath must be.

If such an alcohol bath is used prior to immersion plating, it may be necessary to wait a considerable amount of time, i.e., after removal from the alcohol bath, long enough to allow the lens formed into a pair to dry completely before it is immersed in the hard bath of liquid. This causes dust to be deposited on the cleaned dry mirror surface, even if it is subsequently immersed in the liquid immersion bath very quickly. Thus, an alternative preferred embodiment of the present invention employing an alcohol bath solution is immersed in the liquid hard coating bath solution without the wet alcohol film on the Rx lens pair formed being completely dry. I.e., the wet alcohol film remains on the lens while immersed in the bath solution, leaving the lens in the bath solution for a time sufficient to retain any remaining wet alcohol film (and any dust particles that may adhere during transfer from the alcohol bath to the immersion bath). The immersion plating liquid is circulated at high speed, and the mechanical arm for holding the lens is mechanically moved to form stirring action and vortex.

This SCARA dip and alcohol bath method assumes that at least a significant percentage of alcohol is included in the composition of the liquid hard bath and that the increase in concentration of alcohol due to release from the molded lens during operation does not destroy the desired solvent balance and drying characteristics of the liquid dip bath within a certain concentration range. The liquid solvent composition, which is particularly suited for this protocol and for use with SCARA robots, is also low to moderate (< 10 centipoise, preferably less than 5 centipoise) in viscosity, allowing it to effectively mix/remove wet alcohol films on lenses in the immersion plating bath without entrapping air bubbles, and to flow out smoothly after vibration caused by the immersion motion of the SCARA. Another method of obtaining a smooth coating with such an unconventional low viscosity (2-10 centipoise) immersion plating solution is to use an unconventional rapid draw-off rate (at least 20 inches per minute, preferably 0.5-5 inches per second, and more preferably 1-3 inches per second) and perform at least one second immersion after the first immersion clean. In such rapid withdrawal speed dual immersion processes, the immersion bath should dry relatively quickly (with appropriate selection of volatile solvents such as low molecular weight alcohols and ketones) so that a smooth coating can be formed without flow-through or buckling lines, albeit with a relatively dilute (typically, < 25% solids mass) immersion bath solution having a medium to low hard-coat polymer molecular weight.

Depending on the chemical crosslinking of the selected hard plating solution, a cure station is formed that provides the required curing protocol. For example, the simplest approach is a solvent-free uv curing coating process, in which case the curing station may simply consist of a battery of electrodeless uv lamps (manufactured by Fusion Systems, Rockville, maryland) or conventional mercury arc uv lamps, with the lenses being automatically placed on a support suspended from a suspended conveyor so that the front and rear surfaces of pairs of lenses are exposed to the uv lamps in line of sight for a sufficient time to achieve the desired degree of curing. However, this method requires the use of an alcohol bath. Another variation of this configuration is solvent-based uv curing, in which case solvent drying is performed prior to the uv curing lamp irradiation stage (infrared lamps being the most effective method of devolatilizing the coating if the lens is then shaped to have line-of-sight orientation to the infrared lamp array) so that both front and rear mirror surfaces are dried. And then the principle of the previous paragraph is used.

All thermal curing liquid immersion baths that are required for large scale applications are solvent borne, so that a substantial solvent evaporation/coating drying step is required before curing is accelerated. As previously mentioned, this is the most effective way to achieve this if the orientation of the lens allows the lens to have a set of infrared lamps in sight to be exposed. Once the volatiles are completely removed, the applied exposure to infrared light can achieve complete crosslinking, or can be consolidated into a relatively hard film with a relatively small dose, rendering it "tack free" (meaning that dust is no longer permanently adhered to the surface), so that the tack free coated lenses can be safely handled by hand outside of the enclosed cleaning room without causing waste from the coated clear spots. Or to regenerate a coated, spotted lens, it is also necessary to achieve a tack free condition by immersing the inspected lens with the coating defect in a suitable solvent to strip the tack free but gelled, not yet fully crosslinked coating thereby removing the defective coating and passing the molded pair of lenses through a cleaning and dip coating station to regenerate the coated defective lens.

An alternative preferred embodiment of the curing station utilizes a rotary table equipped with a plurality of arms having mechanical nests adapted to receive the jaws, suction cups or sculptures forming pairs of Rx lenses on which the suspension blade has been molded. A particularly preferred embodiment uses a SCARA robot to accurately place the suspension head into pockets of the type shown in fig. 3B having a generally mechanical mating geometry, preferably with a tapered lead angle fitting, disposed proximate the end of each arm.

Another alternative preferred embodiment of this particular form of curing station allows the arm to be adjustably rotated so that the position of the formed pair of Rx lenses is different from a straight down orientation in which the formed lenses are suspended vertically downward from the arm at a 90 angle, and this angle can be continuously reduced by rotating the arm, perhaps to a minimum angle of about 10 or below about horizontal. (see retention step 58 of fig. 3B). The advantage of this alternative preferred embodiment is that a more uniform flow pattern of the plating solution is formed, allowing all the plating solution to be spread over the mirror surface. This is believed to be particularly important for Rx lenses with high positive power (steep convex front curve) and multi-focal lenses with convex two and three focal lengths. Both lenses are particularly problematic when drying and curing are performed in a generally vertical direction because of the increased uneven flow of the liquid hard-coat solution due to gravity. Reference is made to Weber's coating patent (us patent 4443159).

E process flow of additional steps in the continuous process after "forming and dip-plating".

In another alternative preferred embodiment, after the molded and hard-coated lens is cured to at least a tack-free state, the lens is automatically transferred to an adjacent extension of the same enclosed cleaning chamber, the extension including a computer-assisted automated lens inspection system for lens appearance inspection. See fig. 4C. Thus, automatic lens inspection machines typically employ image recognition computer software to perform visual and/or laser scanning non-contact inspection, compare the resulting image with the computer's judgment rules, and then "pick" and "cut" based on differences in appearance defects. However, optical computer inspection systems for such visual appearance rely on high resolution images, and most of all visual defects occur on the surface of hard coated lenses (particularly "clear spots of coating" and "flow marks of coating"). Non-contact International, Inc. of Maumee, Ohio is one manufacturer of such an Rx FSC lens automated inspection machine.

Such machines that achieve the desired result (i.e., rejecting a bad lens and receiving a good lens) must not reject a "good" lens that has only dust loosely adsorbed on the lens surface. The purity of the lens entering the inspection system is the biggest problem with such machines used to date. Sophisticated and expensive multi-stage cleaning stations and washing protocols are also required to properly use such equipment. The particularly advantageous combination of the present invention with such a machine also requires the use of a matched clean room operating at positive pressure (i.e., the lenses must never leave a clean air environment of 100 grade), without any operator in the clean room space, so that the pair of tack-free hard-coated lenses remain in place as they leave the curing station to the image inspection station. The appearance defective stuck in such a non-adhesive state is automatically picked out, and then subjected to solvent dissolution, rewashing and replating for recycling, as described above.

See the flow chart of fig. 4D. Yet another alternative preferred embodiment of the present invention provides for the hardcoated lenses to be brought to a fully crosslinked state prior to exiting the curing operation and then for the automated transfer of the formed lens pairs with their coatings fully cured in the adjacent extension of a sealed air chamber operating at positive pressure (typically filtered air of 100-degree purity) in cooperation therewith, wherein the connected sealed clean chamber includes an anti-reflective film ("AR") vacuum coater and a multi-pack enclosure and article fixture adapted to form the lens pairs hardcoated. Figure 4D shows a flow chart of the steps of the present invention performed in a single enclosed clean room (all steps performed in the space of the clean room are shown in dashed boxes). The continuous process antireflective vacuum coating system generally comprises the steps of:

1. after the loading station, at least a slight vacuum is drawn and then transferred via the closing device to a second vacuum stage, in which a final vacuum is drawn;

2. at this point certain surface treatment protocols, such as ionized plasma or electron-gun discharge treatment protocols, can be applied in the chamber or in the next chamber connected by the enclosure to clean and/or modify the surface chemistry state of the minority molecule layer on the top surface of the hard-plated Rx lens;

3. once this surface treatment is completed, the automated transfer device moves the pair of lenses through the load lock into the vacuum deposition chamber where the antireflective film is deposited. Preferably, the antireflective film is deposited by sputtering or ion gun means onto a high energy type antireflective film to form a strongly adherent antireflective coating of the desired density on one or both optical surfaces of the already hard-coated pair of lenses.

This continuous process, self-feeding, anti-reflective coating machine is very similar to many similar machines that form aluminum sputter coatings on injection molded polycarbonate compact discs using a continuous process. Manufacturers of advanced Vacuum coating apparatus, such as Leybold, Balzer, and Denton Vacuum, have provided such machines for compact disc global formation and coating.

Claims (76)

1. A lens-coated molding comprising:

a suspension having a head and a stem, both integrally molded on a plastic lens, said lens having a 90 quadrant between 10:30 and 1:30 when placed in an immersion plating position, the tail end of said stem being connected to the gate of said lens outside of said 90 quadrant; the rod has a second gripping location along its length between its head and tail ends.

2. A moulding according to claim 1 wherein the second clamping position of the lever includes a projecting anti-slip stop.

3. A moulding according to claim 1 wherein the stem, but not the head, is shaped to fit different automatic gripping means.

4. A formed article according to claim 1 wherein the shank, but not the head, is configured to fit the geometry of a junction of different workholding fixtures.

5. A moulding according to claim 1 wherein the head is configured in a geometry to cooperate with a robot.

6. A formed article according to claim 1 wherein the head is configured in geometry to engage a workpiece holder.

7. A moulding according to claim 1 wherein the head is configured in a geometry to engage a bracket.

8. A moulding according to claim 1 wherein the head is configured in geometry to cooperate with a robot, a workpiece holder and a stand.

9. A moulding as claimed in claim 1 wherein the head has a horseshoe shape.

10. A moulding according to claim 9 wherein the head includes a stop to prevent the head from being released during transport.

11. A moulding according to claim 1 wherein the head comprises legs which are bendable by a pushing force to prevent the head from being released during transport.

12. A forming member according to claim 1 wherein said lens has a top edge when placed in the immersion plating position, said head portion being located above said top edge.

13. A forming member according to claim 12, wherein said second clamping position is located above said top edge.

14. A form as in claim 1 wherein the suspension is substantially vertical when the lens is placed in the immersion plating position.

15. A molding according to claim 1 further comprising a second lens connected to the plastic lens by a cold runner, wherein the suspension plate upstands from the cold runner.

16. The molding of claim 15, wherein said suspension plate stands vertically from said cold runner when said lens is placed in an immersion plating position.

17. The molding of claim 15 wherein said suspension is positioned equidistant between the two lenses.

18. The forming member of claim 17, wherein said suspension is upstanding vertically from said cold runner when said lens is placed in an immersion hard plating position.

19. The molded article of claim 15, wherein the cold runner is connected to the gate between the 1:30 position and the 4:30 position with one lens and between the 7:30 position and the 10:30 position with the other lens when the lenses are placed in the dip hard plating position.

20. A shaped part according to claim 1, further comprising:

molding the lens with a pair of thermoplastics held in a cold runner;

the cold runner includes a rod with a free end portion including a point above the uppermost edge of the lens when the dual lens is placed in the immersion position, the free end portion providing a first location for automatic gripping, the rod including a second location along its length for automatic gripping.

21. A forming member as claimed in claim 20, wherein said free end portion includes a forked head to provide said first position.

22. The molding of claim 21 wherein said forked head includes a stop configured to receive an automatic grip to prevent disengagement of the forked head during transport.

23. A forming member as claimed in claim 20, wherein said forked head includes leg members which are bent inwardly to provide a spring force to prevent disengagement of the forked head during transport.

24. A moulding according to claim 20 wherein the rod includes a projection to provide the second position.

25. A moulding according to claim 24 wherein the projections extend laterally outwardly from the rod.

26. A forming member as in claim 20 wherein said first position and said second position are spaced along said rod to allow for automatic handoff where a first robot grips said rod in one of said first and second positions and a second robot grips said rod in the other of said first and second positions.

27. The molding of claim 20 wherein said lens is circular, said lens is connected to said cold runner at or below a lens surface at a position equivalent to between 3 o ' clock and 9 o ' clock, and said rod projects above a lens surface at a position equivalent to 12 o ' clock.

28. The molding of claim 20, wherein said lens and said cold runner are formed in the same molding process.

29. A formed part according to claim 20 wherein the rod is formed in moulding without cutting to form the free end portion.

30. A shaped part according to claim 20 wherein the lens when placed in the immersion plating position comprises an upper 90 ° quadrant between the 10:30 and 1:30 positions, the rod being connected to the lens outside the upper 90 ° quadrant.

31. A method of manufacturing a lens comprising the steps of:

molding a molded lens of pad plastic with a cold runner attached thereto, said cold runner including a rod with a free end, said free end including a point above the highest edge of the lens when the lens is placed in the immersion hard plating position, the free end portion providing a first position for self-gripping, the rod including a second position along its length for self-gripping;

clamping one of the first position and the second position to provide a clamping position; and

immersing the lens in the solution without immersing the holding position for dip hard coating the lens, wherein the cold runner is connected to each lens outside a 90 quadrant between the 10:30 and 1:30 positions when the lens is placed in the dip position.

32. The method of claim 31, wherein the molding step comprises injection molding the polycarbonate.

33. The method of claim 31, wherein the free end portion comprises a forked head to provide the first position (1), the forked head including a stop configured to receive the automatic gripping, and wherein the gripping step comprises gripping the forked head at the stop to prevent disengagement of the forked head during transport.

34. A method according to claim 31, wherein said free end portion comprises a forked head to provide the first position (1), said forked head comprising legs which are inwardly flexible to provide the spring force, said gripping step comprising gripping the forked head while compressing said legs to prevent disengagement of the forked head during transport.

35. The method of claim 31, wherein the rod includes a projection to provide a second position (4), and wherein the step of clamping includes clamping the rod below the projection.

36. The method of claim 31, wherein the first (1) and second (4) positions are spaced apart along the rod, the method further comprising the step of delivering the lens between automatic grips, one first robot gripping the rod at one of the first and second positions and one second robot gripping the rod at the other of the first and second positions.

37. The method of claim 31 wherein said step of dip hard plating the dual lens includes maintaining said first position above the solution surface during dip hard plating.

38. The method of claim 31 wherein said step of dip hard plating the dual lens includes maintaining said free end portion above the surface of the solution while the dual lens is fully immersed in the solution during dip hard plating.

39. The method of claim 31 wherein said step of dip hard plating the two lens pieces comprises maintaining said free end portion vertically above the lens pieces during dip hard plating.

40. The method of claim 31 wherein said cold runner is connected to each lens at or below the 3 o 'clock and 9 o' clock positions of the mirrored surface, said step of dip hard coating the dual lenses comprising maintaining said free end portions vertically above said lenses during dip hard coating.

41. The method of claim 31, wherein the molding step includes forming the dual lens and the cold runner in the same molding process.

42. The method of claim 31, wherein the stems are formed in a mold without cutting to form the suspension.

43. The method of claim 31 wherein the molding, clamping and immersion hard plating steps are all performed in the same enclosed clean room.

44. The method of claim 31, further comprising the step of curing the impregnated hardcoating material.

45. The method of claim 31, further comprising the step of plating each lens with an anti-reflective coating.

46. The method of claim 31, further comprising the step of monitoring the contrast lens in an automated monitoring process.

47. A method as in claim 46 wherein said monitoring step is performed in the same enclosed clean room as said molding, clamping and immersion hard plating steps.

48. The method of claim 31, wherein said first location (1) comprises a flap that extends above the lens' highest edge vertically above the immersion plating solution during the immersion hard plating step.

49. The method of claim 31 wherein the cold runner is connected to each lens outside the 90 ° quadrant of one of the lens positions between the 10:30 o 'clock position and the 1:30 o' clock position when the lens is in the immersion hard plating position, the step of immersion hard plating the lens comprising maintaining the free end perpendicular to the lens during immersion hard plating.

50. The method of claim 31 wherein the free end comprises a point above the highest edge of the lens when the lens is hung up during the dip hard coating step.

51. The method of claim 31, wherein the molding step comprises molding two lenses connected by a cold runner, the stem upstanding from the cold runner.

52. The method of claim 51, wherein said bar stands vertically from said cold runner when said lens is placed in an immersion hard plating position.

53. The method of claim 51, wherein the rod is positioned equidistant between the two lenses.

54. A method as claimed in claim 31, further comprising the steps of:

molding a pair of thermoplastic molded lenses connected by a cold runner, said cold runner including a stem with a free end portion, said free end portion including a point above the uppermost lens edge when the pair of lenses is in the immersion hard plating position, said free end portion providing a first position for self-gripping, said stem including a second position for self-gripping along its length;

clamping one of the first position and the second position to provide a clamping position; and

the dual lens is immersed in a solution without immersing the holding position to subject the dual lens to dip hard plating.

55. The method of claim 54, wherein the molding step comprises injection molding the polycarbonate.

56. The method of claim 54, wherein the free end portion includes a forked head to provide the first position, the forked head including a stop configured to receive the automatic gripping, and wherein the gripping step includes gripping the forked head at the stop to prevent disengagement of the forked head during transport.

57. The method of claim 54 wherein said free end portion includes a forked head portion to provide the first position, said forked head portion including legs which flex inwardly to provide the spring force, said gripping step including gripping the forked head portion while compressing said legs to prevent disengagement of the forked head portion during transport.

58. The method of claim 54 wherein the rod includes a projection to provide a second position, the clamping step including clamping the rod below the projection.

59. The method of claim 54, wherein the first and second positions are spaced apart from one another along the rod, the method further comprising the step of delivering the lens between automated grips, one of the first robots gripping the rod at one of the first and second positions and one of the second robots gripping the rod at the other of the first and second positions.

60. The method of claim 54 wherein said step of dip hard plating the dual lens includes maintaining said first position above the solution surface during dip hard plating.

61. The method of claim 54 wherein said step of dip hard plating the dual lens includes maintaining said free end portion above the surface of the solution while the dual lens is fully immersed in the solution during dip hard plating.

62. The method of claim 54 wherein said step of dip hard plating the two lens pieces comprises maintaining said free end portion vertically above the lens pieces during dip hard plating.

63. The method of claim 54 wherein said cold runner is connected to each lens at or below the 3 o 'clock and 9 o' clock positions of the mirrored surface, said step of dip hard coating the dual lenses comprising maintaining said free end portions vertically above said lenses during dip hard coating.

64. The method of claim 54, wherein said molding step includes forming the dual lens and said cold runner in the same molding process.

65. The method of claim 54, wherein the stems are formed in a mold without cutting to form the suspension.

66. A method as in claim 54 wherein said molding, clamping and immersion hard plating steps are all performed in the same enclosed clean room.

67. The method of claim 54, further comprising the step of curing the impregnated hardcoating material.

68. The method of claim 54, further comprising the step of plating each lens with an anti-reflective coating.

69. The method of claim 54, further comprising the step of monitoring the contrast lens in an automated monitoring process.

70. A method as in claim 69 wherein said monitoring step is performed in the same enclosed clean room as said molding, clamping and dip hard plating steps.

71. The method of claim 54 wherein the first position comprises a flap that extends above the highest edge of the lens vertically above the immersion plating solution during the immersion hard plating step.

72. The method of claim 54 wherein the cold runner is connected to each lens outside the 90 ° quadrant of one of the lens positions between the 10:30 o 'clock position and the 1:30 o' clock position when the lens is in the immersion hard plating position, the step of immersion hard plating the lens comprising maintaining the free end perpendicular to the lens during immersion hard plating.

73. The method of claim 54 wherein the free end comprises a point above the highest edge of the lens when the lens is hung up during the dip hard coating step.

74. A method according to claim 54 wherein the molding step comprises molding two lenses connected by a cold runner, the stem upstanding from the cold runner.

75. The method of claim 74 wherein said rod stands vertically from said cold runner when said lens is placed in an immersion hard plating position.

76. The method of claim 74, wherein the rod is positioned equidistant between the two lenses.