HK1024882A - Method and apparatus for assembling lens-forming device - Google Patents

Description

Method and apparatus for assembling lens forming structures

The invention includes apparatus and methods for cast molding of lenses and gaskets for use therein. The invention also includes a method of curing such cast lenses, and an apparatus and method for separating the cured lens from the mold in which it is formed.

The glasses must be adapted to the requirements of the individual and to the morphological and psychological characteristics of the individual. Ophthalmic lenses for spectacles are made of transparent material, usually glass or plastic, and are sized and shaped to produce the desired effect, i.e. to concentrate the light reaching the human eye so that it can be seen clearly.

The lenses adopt a well-defined geometry which determines their optical characteristics. The shape of each lens is characterized by three characteristics: (1) the curvature of its two surfaces; (2) thickness of the center and edges thereof; (3) its diameter. The two surfaces of the lens may take on different geometries, including: a spherical shape; a cylindrical shape; a toric surface shape; a planar shape; aspherical (typically elliptical); and progressive. For example, the surface of the lens may have a constant radius along its various axes, so the surface is symmetrical, referred to as a spherical shape. Such spherical lens surfaces reference the shape of a portion of a sphere in which all meridians have the same radius of curvature. The spherical surface may be either concave or convex.

Alternatively, the lens surface may have two axes, each with a different radius of curvature, so that the surface of the lens is asymmetric. An example of such an asymmetric surface is a light diffusing surface, which is characterized in that its two main meridians have mutually different radii of curvature. The largest radius of curvature is referred to as the "axis" and the other meridian with the smaller radius is referred to as the "orthogonal axis". The astigmatic lens surface consists essentially of a cylindrical surface and a toric surface. One example of a planar and non-spherical surface is other lens surfaces employed in the art.

For a cylindrical surface, the principal meridian along the axis has an infinite radius of curvature, e.g., a flat or straight meridian, with the orthogonal axis having a radius of curvature that is the same as the circumferential radius of the cylinder. Thus, a concave cylindrical surface is shaped to complementarily receive a cylindrical shape on its surface, while a convex surface is similar to the cylindrical outer surface.

The toric surface resembles an annular side surface, for example, shaped like the inner tube of a tire. Thus, an annular surface resembles a cylindrical surface, but its long axis is curved rather than straight as is the case with a cylindrical surface. The orthogonal axes or meridian lines on the toric surface have a radius of curvature that is less than the radius of the axes. Like spherical and cylindrical surfaces, toric surfaces can be convex, having an outer surface shape of a torus, or alternatively, can be concave having an inner surface shape of a torus.

An astigmatic surface is used for visually astigmatic persons whose cornea is elliptical rather than circular. Astigmatic corneal extensions are easily oriented by humans. For example, one person may have one axis of 5 degrees while another person has an axis of 30 degrees, while another person also has a differently oriented axis. The orientation of the axis of the lens surface must coincide with the orientation of the corneal elongation.

Different lens surfaces may be used in combination. Typically, the anterior surface of the lens is spherical and the posterior surface is spherical, cylindrical or toric. In another aspect, the front surface may be a flat surface. The optimum combination of lens surfaces is determined by the optical properties, the intended use and the appearance of the lens.

In addition to shape, thickness is also an important property of the lens. The glass or plastic used to form the lens is one factor in determining the thickness. Today, many lenses are made of plastic because of its light weight, low density, low refractive index, and impact resistance. Examples of plastics used to make lenses include methyl methacrylate (a thermoplastic resin known under the trade designation "Plexiglas"  or "Perspex" ) and modern glycol carbonates, also known as CR 39.

CR39 is one of the most popular lens materials used today because all lens types used in ocular optics can be made of this material. CR39 is a polyester-based petroleum derivative, a family of polymerizable thermosetting resins. In production, monomer was first obtained from CR 39. This monomer is a clear liquid with the viscosity of glycerol, which is liquid under refrigeration but solidifies at room temperature for several months. To form a lens, the liquid monomer is placed and contained within a volume defined by two molds and a gasket. Once the monomer is within the volume, the monomer is cured to form a hardened polymeric lens in the shape of the mold.

The glass mold used to form the polymer lens is important in the manufacture of CR39 lenses. Not only does the mold form the lens to the correct shape in accordance with the desired optical characteristics, but the surface quality of the formed lens depends on the precision of the molds because the lens surface is an exact replica of the inner surface of the molds. Therefore, the surfaces of these molds are prepared with extremely high precision and are heat-toughened after manufacture to withstand deformation during the polymerization reaction.

An increased power (power) anterior mold that forms the bifocal or trifocal portion of the lens can also be used to form the lens. The power-increasing mold includes a partial arc which is a depression cut into one half of the concave surface of the mold to form the increased thickness portion on the anterior surface of the lens. This portion of the arc produces a convex surface for the remote portion and a steeper convex surface for said portion of increased thickness.

As described above, the liquid monomer is placed in a volume defined by two molds and a gasket to form a lens. As shown in cross-section in fig. 1, the prior art gasket is referred to as a T-washer G, with a bore B and two ends, each end complementarily receiving a respective die M. Since each T-washer G sets a predetermined axial separation distance between the molds M, different T-washers G are required to form lenses of different powers. That is, one T-washer G allows the mold to be further separated to form a lens of greater power than another T-washer G used to form a lens of lesser power. Therefore, the manufacturer must keep a single T-washer G for one +2 lens, another for one-3 lens, and yet another for one-4 lens, and so on.

Those skilled in the art will appreciate that forming a light diffusing surface within a T-shaped gasket G requires that the end of the gasket be of the same shape as the inner surface of the mold M. For example, if the back mold M forms a concave toric surface, one end of the T-washer G must have a complementary convex design to receive the mold M without leakage. Furthermore, there must be a different T-washer for each lens thickness that takes that mold shape.

Two manufacturing processes are used in the manufacture of the lenses: direct polymerization and polymerization of semi-finished lenses. For the direct polymerization process, the upper mold is removed and a nozzle is directed into the mold cavity to fill the volume with monomer. The operator then places the upper die in alignment with the T-washer so that excess monomer is squeezed out and air bubbles are eliminated. The volume defined by the two polished molds and the gasket when cured forms the shape of the lens. Disadvantages of this prior art system include process solidification, synthesis mess and wasted monomer. And some air bubbles remain trapped in the volume, which may damage the formed lens. Therefore, such production processes are labor intensive and are therefore often performed in areas with inexpensive labor.

To cure the monomer after the top mold is secured to the T-shaped gasket, the filled gasket assembly is stored in a rack and placed in an oven for 14-16 hours to withstand a controlled temperature cycle that provides the correct degree of polymerization. When this lengthy curing process is completed, the gasket assembly is removed and the lens is removed from between the molds. Lenses made using this direct polymerization production process require some finishing work such as edge deburring, annealing to relieve casting stress, visual inspection to remove lenses that may have defects, and lens power inspection with a focus gauge. Once the lenses are finished, they are packaged for shipment to retailers or mounted on consumer's eyeglasses.

The second process, the polymerization of the semi-finished lens, produces a lens known as a "semi-finished" lens. Unlike direct polymerization lenses, a semi-finished lens has a concave unfinished side, the side of the surface when the curing process is complete. Thus, rather than having few finishing operations to form the lens to be incorporated into the lens, the semi-finished lens has only one finished surface formed by the mold, and the other surface is mechanically finished after the lens has been cured. Thus, the semi-finished lens is manufactured in stages, with one surface finished by the mold and the other surface cured and then machined. The lens surface formed by the mold is typically the anterior spherical surface, with or without power addition.

The unfinished side of the semi-finished lens is typically finished in the same manner as a glass lens using a special lathe or motor (generator), but with other abrasives. The polymerized lens was mounted on a circular holder, the surface of which was machined with a diamond grinding wheel. The curvature is controlled by the relative position and angle of the diamond grinding wheel and the lens. This surface is then finished and finally ground with a suitable surfacing tool. Lapping and grinding are performed using metal tools, each surface shape having its own tool. Therefore, a large number of tools are required to surface the entire area of the lens. Such semi-finished lenses are typically placed in a holding table and reprocessed when needed, for example, when a customer of a particular request orders the lens.

For high power lenses, such as aphakic lenses or lenses having high cylindrical power, semi-finished lenses are used rather than direct polymerization lenses. Such high power lenses cannot be made by direct polymerization because the difference between the lens center and edge thickness causes significant stress that can break the glass mold with the T-shaped gasket.

Another reason for manufacturing semi-finished lenses is the large number of lenses that are not mass-produced, which are required by different consumers. For example, a quality requirement may require adding a certain power to its front surface and its back surface is a astigmatic back surface arranged in one or more different orientations. That is, the power-increasing portion must be oriented such that its plateau is horizontal, but its astigmatic surface varies as the elongated portion of the cornea varies from person to person. Those skilled in the art will appreciate that there are many variations to a particular add power and a given differently oriented astigmatic back surface. Mass production of endless lenses is not feasible, so it is common for retailers to purchase a semi-finished lens and machine its astigmatic surface immediately prior to sale.

The present invention overcomes the disadvantages of the prior art and improves upon the lens forming process. Specifically, the present invention includes a gasket that can be formed to all thicknesses and geometries of a lens, and is not limited to forming a particular lens as is the case with prior art T-shaped gaskets. The invention also includes an apparatus and method for forming lenses using an automated manufacturing process. In addition, the present invention includes a method of curing the formed lens in a fraction of the time required for the prior art manufacturing process. Further, the present invention includes an apparatus and method for separating a cured lens from a mold used to form and trim the lens.

The gasket of the present invention is designed such that either or both of the front mold and the back mold are movably disposed within the bore thereof. At least one of the dies is axially movable within the bore relative to the other die to a position having a desired axial spacing between the dies. Each different desired axial separation distance corresponds to a different lens power. Unlike prior art T-washers, the washer of the present invention is capable of receiving a variety of molds having different surfaces (i.e., spherical or astigmatic) to produce the desired lens surface. Since a single gasket is used to form multiple powers of the lens and different lens surfaces, such a gasket of the present invention is referred to as a "universal gasket".

Therefore, those skilled in the art recognize that the prior art T-washers place and hold the mold at a set distance apart, which creates a problem because the monomer volume shrinks by about 10% -15% when cured. Annealing is sometimes required because the mold remains stationary while the T-washer is used, and this shrinkage causes internal stresses in the lens. In comparison, the gasket of the present invention reduces stress by allowing some axial movement of the mold as the monomer volume shrinks during curing. Thus, lenses made with the gaskets of the present invention typically do not require annealing.

The casting process of the present invention includes positioning at least one of the molds rotatably and axially movably relative to the other mold so that a lens of the correct power can be formed therebetween. That is, rather than relying on the design of the gasket to set the dimensions of the lens, the present invention employs automated techniques, including modern motion control devices with precise tolerances, to position the molds within the gasket at the proper axial spacing from each other. The invention also includes automated techniques for rotating the molds to the proper orientation relative to each other, e.g., the toric back surface mold is rotated into proper alignment with the add power.

The monomer is then injected into the volume defined by the two molds and the bore of the gasket to form the desired lens. The monomer is injected through a needle rather than being poured into the gasket and the excess extruded when the posterior mould is placed on the gasket. The filling method of the present invention greatly reduces the amount of wasted monomer and reduces the chance of bubbles forming within the lens.

The production of lenses using the invention is more economical and efficient because the amount of lens mold equipment required for lens production is greatly reduced, as well as the amount of manual labor previously required in forming the lenses is greatly reduced, if not eliminated.

Further, the lenses produced using the present invention are a number of improvements over the prior art. The quality of the mechanically finished surface of the semi-finished lens after cutting and grinding is lower than that produced directly from the glass mold. Those skilled in the art will appreciate that it takes a technician a long time to cut, grind and finish the mold as perfectly as possible when forming the front and rear glass molds, and conversely, one lens surface cut by a motor (generator) may be less accurate.

The present invention therefore allows the use of a single universal gasket designed for a specific quality requirement to immediately produce a customized product of any axial orientation. Unlike the prior art, no cutting of the lens or lens motor (generator) is required. That is, once a lens is cured using the present invention, the lens is a finished lens, unlike the semi-finished lenses of the prior art. The invention is faster and cheaper than the prior art.

The present invention also greatly reduces the time required to cure the monomer. As described above, the curing in the prior art takes 14 hours or more depending on the design of the lens. The invention has only one step, namely the universal gasket of the invention is used. In fact, the lens can cure in about 1 minute.

Another aspect of the invention is a method and apparatus for separating a cured lens from a mold comprising directing a fluid such as carbon dioxide gas to the interface of the lens and a mold. The temperature of the gas is lower than the temperature of the mold-lens-mold sandwich just cured, causing shrinkage of the element. The polymer and glass molds from which the lenses are formed have different coefficients of thermal expansion that cause different shrinkage rates. This differential shrinkage helps break the bond between the mold surface and the corresponding lens surface. The present invention is superior in this respect to the prior art, which generally requires physically pulling these elements apart.

The invention allows for rapid production of lenses to suit specific quality requirements. Producing lenses at this speed greatly reduces the operating time (regardless of the power and surface shape of the lens) compared to the prior art. For example, prior art systems allow a wholesaler to sell lenses in about an hour, but this is only the time required if the lens is a standard normal lens. That is, if the quality requires a toric lens with an increased power, one hour is not enough. In such cases, the prior art requires the wholesaler to use a semi-finished lens with an increased thickness on its front surface and use a motor (generator) to cut the back surface of the lens into the desired toric surface. Those skilled in the art will appreciate that the use of a motor (generator) is time consuming and thus is an exception to the 1 hour case described above. In contrast, the present invention allows for the formation and curing of one lens in less than 30 minutes, which is faster than retailers producing a limited number of lenses, several days faster than forming other lenses from one semi-finished lens.

In addition, the present invention provides an opportunity for doctors to wait a short period of time in their office for the lenses required by their prescription to be manufactured. The given speed and short curing time for manufacturing lenses of the invention is clear from a commercial point of view, and it enables one-job shopping for patients/customers. Thus, the patient can examine the eye and wait about 30 minutes to leave with the glasses matching the prescription filled after examination.

FIG. 1 is a cross-sectional view of a prior art T-washer.

Fig. 2 is a cross-sectional view of the stepped washer of the present invention.

Fig. 3 is a cross-sectional view of a straight-walled gasket of the present invention showing some of the holes in the gasket.

FIG. 4 is an exploded cross-sectional view of the die and a gasket, wherein the front die defines an annular ring defining an edge thereof.

FIG. 5 is a perspective view of the present invention showing an assembly station, robot and infusion station.

Fig. 6 is a top plan view of an assembly station disposed outside of the housing.

FIG. 7 is a side cross-sectional view of the assembly station piston after it has been lifted.

Fig. 8 is a side cross-sectional view of the piston of fig. 7 after it has been dropped and showing a camera.

Fig. 9 is a perspective view of a radial clamping device for use with the present invention.

Figure 10 is a side view of a robot for use with the present invention.

FIG. 11 is a top plan view of the system showing the robot moving to one infusion station and picking up the gasket and radial clamp from the assembly station and moving to another infusion station.

FIG. 12 is a front view of the infusion stage.

FIG. 13 is a side cross-sectional view of the infusion stage taken along line 13-13 in FIG. 12 when the lens shaping assembly is first reached.

Fig. 14 is a side cross-sectional view of the infusion station shown in fig. 13 when infusion is initiated, with the needle inserted into the gasket and the linear actuator having moved the posterior mold to the correct axial separation distance from the anterior mold.

Fig. 15 is a schematic partial schematic cross-sectional view of a UV curing apparatus that cures lenses formed at the assembly station and the infusion station.

FIG. 16 shows a partial schematic perspective view of a separation device of the present invention for separating a mold from a cured lens.

FIG. 17A is a cross-sectional view of the assembly tool showing the gasket aligned to mount the rear mold in its bore.

FIG. 17B is a cross-sectional view of FIG. 17A, wherein the posterior mold is inserted into the gasket using the assembly station.

The present invention is described in further detail in the following examples, which are intended for the purpose of illustration only, since numerous modifications and variations will be apparent to those skilled in the art. As used in the specification and in the claims, the terms "a" and "an" may mean one or more, depending on the context. The preferred embodiments will now be described with reference to the drawings, wherein like reference numerals refer to like parts throughout.

Referring to fig. 2-17B, the present invention includes a lens casting method and gaskets for use therein. The invention also includes a method of curing the cast lens, and an apparatus and method for separating the cured lens from the elements from which the lens is cast.

Gasket of the invention

The gasket 20 of the present invention can be used to form lenses of various powers and does not require differently designed gaskets for each different lens to be formed, as in the prior art. Referring to fig. 2 and 3, the washer 20 of the present invention has a first end 22 and an opposite second end 24, a body portion connecting the first end 22 to the second end 24, and a longitudinally or axially extending axis L. The washer 20 has an outer surface 26 and defines a bore 30 extending axially through the washer 20 between its opposite ends 22, 24. The bore 30 defines an inner surface 32 that defines a longitudinal axis L of the gasket 20.

The outer surface 26 of the washer 20 is preferably circular or annular (as shown in the perspective view of fig. 9), so the preferred embodiment of the washer 20 is substantially tubular in shape. Although other shapes (e.g., elliptical, polygonal, or other non-circular shapes) may be used, a circular cross-section embodiment is preferred for its acceptance in the art, manufacturing conditions, and ease of automation.

The front mold 40 and the rear mold 50 are installed in the hole 30 of the gasket 20. As best seen in fig. 4, the anterior mold 40 has a front surface 42, an opposite back surface 44, and edges 46 defining it. The rim 46 is sized to complimentarily fit within at least a portion of the aperture 30 such that the rim 46 forms a substantially leak-proof seal with the inner surface 32 of the gasket 20.

Similarly, the posterior mold 50 also has a front surface 52, an opposite back surface 54, and an edge 56 defining it. The rim 56 is sized to complimentarily fit within at least a portion of the aperture 30 such that the rim 56 and the inner surface 32 of the gasket 20 also form a substantially leak-proof seal therebetween. Since the preferred embodiment of the gasket 20 described above is circular in cross-section as shown in fig. 9, the dies 40, 50 are preferably also circular and have a diameter. When both the anterior mold 40 and the posterior mold 50 are fitted into the bore 30 of the gasket 20, as shown in fig. 2 and 3, the combination of these elements is referred to as a lens forming assembly 10, a lens forming structure or a lens casting unit.

When the molds 40 and 50 are placed within the gasket 20 as described above, a space is formed that is defined by the rear surface 44 of the front mold 40 and the front surface 52 of the rear mold 50 and the inner surface 32 of the gasket 20. That is, the dies 40 and 50 are placed in spaced relation to each other within the bore 30 so as to form a space therebetween. This space, referred to as cavity 31, is preferably of a suitable size to form a desired lens when a lens-forming liquid is injected into the cavity 31 and cured therein. This cavity 31 is also shown in the cross-sectional view in fig. 4.

The lens-forming liquid is preferably a monomer. The preferred monomer is manufactured by p.p.g. located in Monroeville, Georgia under the trade name CR 424. Those skilled in the art will appreciate that the present invention is capable of using other lens-forming liquids known in the art.

The present invention also includes an apparatus for injecting the monomer into the chamber 31. The preferred injection device comprises an injection needle as discussed in detail below. The present invention also includes a means for providing fluid communication between the outer surface 26 of the gasket 20 and the cavity 30. The preferred means for providing includes a vent needle in communication with the bore 30 so as to allow fluid communication between the air in the cavity 31 and the exterior of the outer surface 26 to facilitate the axial movement of the injection unit and the molds 40, 50.

Either the anterior mold 40 or the posterior mold 50 is axially moved in the bore 30 relative to the other mold to a desired one of a number of anterior and posterior mold axial separation distances. The space is different for each axial separation distance and thus the size of the lens formed in the cavity 31 is different for each axial separation distance. As described in detail below, the infusion station of the present invention uses a computer-assisted system (or controller such as a computer or micro-curing press), robotic arms, and linear actuators or servomotors to accurately place the posterior mold 50 in a predetermined position within the bore 30 relative to the anterior mold 40. Because the automation includes modern motion control devices with tight tolerances, the quality of the lenses produced by the present invention is higher than the quality of lenses produced by prior art systems.

Referring to fig. 2, the bore 30 of the washer 20 defines a first diameter adjacent the first end 22 thereof that decreases along a portion of the length of the bore 30. The first diameter is sized to complimentarily fit the rim 46 of the anterior mold 40. The bore 30 also defines a constant second diameter adjacent the second end 24 of the washer 20 that extends along a portion of the length of the bore 30, wherein the second diameter is sized to complimentarily fit the rim 56 of the posterior mold 50.

A transition portion 34 exists within the bore 30 between the first diameter and the second diameter. The transition portion 34 includes an inset step 36, i.e., ridge, for positioning the anterior mold 40 in a fixed, known position within the bore 30. A transition step 36 is formed in the inner surface 32 of the washer 20 at the junction of the first and second diameters. The front mold 40 is slidably mounted along the inner surface 32 of the gasket 20 until it engages the step 36 of the transition portion 34. The portion of the back surface 44 of the anterior mold 40 adjacent the edge 46 is shaped to complimentarily engage the transition portion 34 to form a substantially leak-proof seal therewith. That is, the transition portion 34 has an annular geometry, and the anterior mold 40 has a corresponding annular rim 46 that complementarily partially mates with the transition portion 34 to form a seal that substantially prevents leakage of the monomer disposed within the cavity 31. The transition portion 34 may be angled from a right angle with respect to the inner surface 32 to an angle offset from the right angle of 20 degrees or more, preferably 10 degrees. The transition section 34 and the edge 46 of the anterior mold 40 may alternatively have other mating shapes to form a leak-proof seal therebetween.

In this embodiment, the posterior mold 50 is axially movable along at least a portion of the bore 30 to be positioned at a desired axial spacing from the anterior mold 40, which is smoothly positioned within the transition section 34. Since the washer 20 of the present invention is designed for automation technology, the second diameter along the inner surface 32 of the bore 30 between the transition portion 34 and the second end 24 of the washer 20 is constant. The diameter of the back mold 50 is substantially the same as the second diameter so that the back mold 50 can be inserted into the bore 30 and slid axially along the bore to a desired axially spaced position from the front mold 40. As discussed above, when both the front mold 40 and the rear mold 50 are disposed within the bore 30 of the gasket 20, the cavity 31 defined by the molds 40, 50 and the inner surface 32 of the gasket 20 can contain a liquid, such as a liquid monomer, without leaking.

In a non-illustrated gasket variant having a transition portion, the first diameter of the bore may remain constant moving inwardly from the first end of the gasket and then abruptly expanding to form an axially extending gap adjacent the transition portion. The gap is sized to complimentarily receive the edge of the anterior mold therein. This embodiment also positions the anterior mould tool adjacent the transition portion. That is, when the anterior mould tool is inserted axially into the bore, it snaps into place in the gap and remains stably and removably adjacent the transition portion.

Another embodiment of the invention shown in fig. 3 includes a gasket 20 without a transition portion or step. Instead, the first and second diameters are the same, so the bore 30 has a constant diameter along its entire length. Thus, similar to the slidable positioning of the posterior mold 50 in the transition section gasket embodiment, the anterior mold 40 and/or the posterior mold 50 are movably positioned within this straight wall gasket. Those skilled in the art will appreciate that one die may remain in a fixed position while the other die moves axially within the bore 30, similar to the transition section embodiment. Alternatively, both molds 40, 50 may be moved independently, either simultaneously or non-simultaneously with each other. The preferred embodiment of the washer 20 also has a keyway 28 adjacent its second end 24 to ensure proper alignment of the washer 20 during the lens forming process.

Comparing the transition-with gasket and the straight-walled gasket embodiments, the transition-with gasket has the disadvantage that although there is substantially no leakage through the front mold 40, a small amount of the liquid monomer can penetrate and creep between the transition 34 and the front mold 40. Thus, when the cured lens is removed from the gasket 20, it is not cleaned along its outer periphery, which requires a post-curing process to remove lens material that leaks into the junction of the anterior mold 40 and the transition section 34. Moreover, some monomer may be left in the hole 30 adjacent the transition portion 34, which must be cleaned and removed before the gasket 20 can be reused. Thus, additional time and expense is required to reuse the gasket device with the transition portion because the cured lens is cured and/or the gasket 20 and the anterior mold 40 are cleaned for reuse. Another related disadvantage is that the number of uses or life of the gasket with the transition portion 34 can potentially be shortened by cleaning thereof. However, in automated systems, this arrangement of the gasket with the transition portion is simple to implement because the front mold 40 is in a known position and the rear mold 50 is axially displaced a desired axial spacing distance relative to this fixed position.

While automation is more complicated for straight wall embodiments, the use of such gaskets is less expensive in the long term due to the significant reduction in cost of cleaning the front mold and gasket. Thus, such a straight-walled embodiment would have a longer useful life.

Referring again to fig. 2 and 3, each gasket 20 according to the present invention preferably further includes one, and more preferably two, ports 38, 39 formed in the body portion 20 of the gasket 20 between the outer surface 26 and the inner surface 32 thereof. These ports 38, 39 are in fluid communication with the bore 30, particularly the cavity 31 formed between the rear surface 44 of the front mold 40 and the front surface 52 of the rear mold 50 and the inner surface 32 of the gasket 20. Each port 38, 39 is adapted to receive a portion of a needle therein such that the needle is in fluid communication with the cavity 31 and is not inserted into the bore 30 itself. The injection needle is placed in fluid communication with one port (injection port 38) and the vent needle is placed in fluid communication with the other port (vent port 39). That is, one port 38 adds monomer to the chamber 31 and the other port 39 vents air within the chamber 31 when replaced by incoming monomer. The vent 39 also provides fluid communication between the outside of the gasket 20 and the cavity 31 to allow air to be excluded from entering the space or existing spaces in accordance with the relative axial movement of the molds 40, 50 by axially moving the molds 40, 50 relative to each other. Preferably, the needle passes through the washer 20 into the respective port 38, 39 in a direction substantially parallel to the longitudinal axis L of the washer 20, as opposed to at a steeper angle. This small angle or parallel alignment with the longitudinal axis L reduces the chance that the tip will be able to contact one of the dies 40, 50. However, the steeper angle may be perpendicular to the longitudinal axis L and the washer 20 still functions properly.

These ports 38, 39 are beneficial when the cavity 31 is relatively small, such as when the back surface 44 of the front mold 40 is very close to the front surface 52 of the back mold 50. In this case, insertion of the needle tip into the bore 30 contacts one or both surfaces 44, 52 of the two dies 40, 50. This contact could potentially damage a surface of the mold or move a mold so that the lens would not be the correct size, or leak monomer into the cavity.

It is also contemplated that only one hole (not shown) through gasket 20 will vent air from the cavity. That is, the cavity 31 is in direct communication with the outside air, rather than through the port 39 and needle.

Another aspect of the gasket of the present invention is the material of the gasket. In the presently preferred embodiment, the desired characteristic is that the gasket material is chemically compatible with the lens forming liquid to avoid inhibiting polymerization of the liquid. The gasket material should not include free radical inhibitors such as "UV" stabilizers and antioxidants. A UV stabilizer can soak into the monomer because the monomer always acts like a solvent to extract this additive from the gasket material and locally mix into the monomer, causing the edge of the lens to remain slightly wet after curing. This moisture can be a problem because it potentially causes the monomer to adhere to the gasket 20 and the dies 40, 50, which requires cleaning before reuse, increasing operating costs. Therefore, it is desirable that the gasket be a polymeric elastomer compatible with the optical monomer, which will not inhibit the lens monomer during curing. Yet another aspect of the gasket material is that it is relatively soft, for example between 40-70 as measured by a durometer. Another related aspect is whether the gasket has long-term stability.

In a preferred embodiment of the invention, a suitable gasket material is a thermoplastic rubber comprising KRATON  G, a styrene-ethylene-propylene (butylene) block copolymer, sold by Shell oil of Houston, Tex. Such rubbers include those sold by GLS corporation of Cary, illinois under the trade names DYNAFLEX  G2703, 2711 and 2712. These rubbers have a Shore A hardness of about 43-62, a specific gravity of about 0.9g/cc, an elongation of 300%, an elongation of from about 355-470, a tensile strength of about 680-1000psi, and a tear strength of about 113-127. Another contemplated gasket material includes a PVC composition. However, the gasket material of the present invention is not limited to a single material. In fact, the ideal gasket material may vary depending on the particular monomer compound used to form the lens. That is, a certain gasket material may be preferred for one particular lens-forming liquid, while a different type of gasket material is selected for another lens material. Other contemplated materials include flexible PVC, silicon, ethylene vinyl acetate or mixtures thereof.

When saidAfter vent needle 232 or injection needle 252 has been removed from gasket 20, the present invention also preferably includes a means for sealing gasket 20. Preferably, the seal comprises PVC, silicon, KRATON^G. Ethylene vinyl acetate or mixtures thereof. That is, the gasket is self-sealing, and thus this compound prevents leakage after needle withdrawal.

Other sealing means are envisaged including, for example, physically blocking the needle aperture when the needle is withdrawn. Alternatively, the sealing means may comprise a needle retained in the gasket to prevent leakage of liquid therefrom, but this embodiment is undesirable because of operational limitations on the portion of the needle extending out of the gasket 20, and often limitations in the process of replacing the needle at the infusion station. Yet another embodiment of the sealing means is to cure the monomer leaking into the needle hole, for example by quickly exposing the monomer adjacent the needle exit support to UV light, heat or other curing source. Instead of a monomer curing in the pinhole acting as a sealing means, the heat applied to the gasket 20 may itself alternatively seal the pinhole.

Fig. 4 shows an alternative embodiment of the mold, with the front mold 40 having an annular ring 60 defining the edge 46 and abutting the rear surface 44. The annular ring 60 increases the area of the cavity 31 adjacent the front surface 52 of the back mold 50, thus allowing better communication with the ports 38, 39 or needle tips if the needle is inserted substantially perpendicular to the longitudinal axis L. The protrusions formed during the shaping of the lens will be removed in a post-curing process. Those skilled in the art will appreciate that an annular ring may alternatively or additionally be included on the front surface 52 of the back mold 50.

Method and apparatus for casting ophthalmic lenses

In summary, the lens forming assembly 10 is first machined at the assembly station 110 and then machined at the infusion station 200, which is generally shown in FIG. 5 and generally designated 100. The frame 104 supports the platforms 110, 200. In a preferred embodiment, the molds 40, 50 are rotatably aligned with one another and placed in the bore 30 of the washer 20 at the assembly station 110. At the injection station 200, the molds 40, 50 are moved axially within the bore 30 and are spaced apart from one another by a desired distance (e.g., an appropriate spacing distance to produce a lens of a desired thickness). A lens forming liquid is also injected at the infusion station 200 into the cavity 31 formed between the two molds 40, 50 and the aperture 30. The method of the present invention will be discussed in terms of embodiments of gaskets employing transition portions as opposed to straight wall type gaskets.

Assembling table

Referring now to fig. 5-8, assembly station 110 includes a means for supporting washer 20 so that molds 40, 50 are inserted into bore 30. The assembly station 110 preferably has three alignment collets: a front mold locating collet 120, a rear mold/washer locating collet 130 and a clamp locating collet 150. The cartridges are mounted on a plate 112 that slides along a track 114. A drive cylinder 116, such as a pneumatic or electric cylinder, moves the slide plate 112 along the rail 114 between a charging position and an assembly position. In the loading position shown in fig. 6, the slide plate 112 is disposed outside the perimeter of the housing 102, while in the assembled position shown in fig. 5, the plate 112 is disposed within the perimeter of the housing 102.

The housing 102 is preferably made of glass or clear plastic and acts as a barrier and covers the infusion station 200 and robot 160 (discussed in more detail below) to ensure that the operator avoids interference with the components. The enclosure is also employed for safety reasons, such as to protect the operator from inadvertent contact by a robot arm, etc.

In the preferred embodiment, the anterior mold 40 is stored on a storage station (not shown) located adjacent to the assembly station 110. The gasket 20 is stored in another location also adjacent to the assembly station 110 or in the same storage station as the front mold 40. The gaskets 20 preferably each have a rear mold 50 disposed within its respective bore 30. As will be discussed in detail below, the posterior mold 50 is preferably placed in the aperture 30 of the corresponding gasket 20 when the curing process is complete and when the cured lens is separated from the two molds 40, 50. Those skilled in the art will appreciate that the gasket 20 and molds 40, 50 may be stored in different combinations. For example, the dies 40, 50 and the gasket 20 are all stored as separate elements, or the front die 40 is placed in the gasket 20 and the rear die 50 is stored separately, or both dies 40, 50 are placed and stored within the bore 30 of the gasket 20.

To begin the manufacturing process of the preferred embodiment, an operator enters parameters of the lens to be shaped (e.g., commands including additional magnification), such as via a keyboard, into a computer-aided system (not shown) that also includes a storage-aided system and a hard disk that runs a computer program. The power supply means (not shown) for driving the electronic components in the present invention, such as a computer-aided system, is preferably a 120V ac power supply.

Algorithms used in the computer program determine the appropriate anterior and posterior molds for forming the desired lens and the computer-assisted system then provides an output indicative of the appropriate mold to be used. The anterior mold 40 is generally spherical and the posterior mold 50 is generally spherical or astigmatic, e.g., toric or cylindrical. For additional magnification, the anterior mold 40 may also be adapted to be formed into bifocals or trifocals.

In one embodiment of the invention, the computer-assisted system displays on its monitor an output indicative of the appropriate mold to be used. Another embodiment additionally illuminates a beam of light (not shown) on a storage table in a specific location where a suitable mold is stored. The indicator light helps the operator determine the proper mold to reduce the probability that the operator will inadvertently pick up the incorrect mold to manufacture the lens.

One means of transferring the elements of the lens forming assembly 10 to the slide plate 112 of the assembly station 110 is by an operator manually moving the elements. The present invention can also use an automated device (not shown) to move the components of the lens forming assembly 10 onto the plate 112 of the assembly station 110. In this automated system, the computer-aided system operates an arm (not shown) controlled by electronic means to transfer the appropriate molds 40, 50 and a gasket 20 to the plate 112 of the assembly station 110. Once the molds 40, 50 and gasket 20 are transferred to the plate 112, the plate 112 is then slid along rails 114 from the loading station to an assembly position within the perimeter of the housing 102.

The anterior mold locating collet 120 of the assembly station 110 has an upstanding annular flange 122 adapted to receive the anterior mold 40. Other anterior mold support devices include a vacuum support (not shown), spring clips (not shown), and the like. The anterior mold locating collet 120 may have a beam of light (not shown) to indicate that an anterior mold is placed in the collet or an interlock to prevent the process from continuing until an anterior mold is placed on the collet 120.

The rotational orientation of the spherical anterior mold 40 does not present a problem when it is placed on the anterior mold locating collet 120. However, orientation is important for an anterior mold or an asymmetric mold suitable for forming an additional thickness lens. In a preferred embodiment, the anterior mold locating collet 120 is marked with a series of parallel marking lines (not shown). The operator aligns the straight line forming the top of the flat top so that the straight line is aligned or parallel with the marking lines. In this way, the anterior mould with the additional magnification can be placed in one of two positions, mutually offset by 180 ° and both parallel to the marking line. For progressive addition power front molds (where there are no identifiable markings on the front mold or on the asymmetrical front mold), the mold may be etched or scribed with a line to align. An electronic eye (not shown) or the like may be used to verify proper positioning before allowing the procedure to proceed. Alternatively, robotic manipulation means using a vision system can properly position the anterior mold on the anterior mold positioning collet 120.

One reason for correctly positioning the add-on power mold is that its flat top portion is vertically oriented during filling of the lens-forming liquid into cavity 31 to prevent air bubbles from being left therein. If, for example, the flat top is oriented horizontally during filling, air bubbles are likely to remain in the cavity 31. In addition, it is important that the anterior mold 40 be properly positioned relative to an astigmatic posterior mold 50 to ensure that the additional thickness is properly oriented in the formed lens.

The anterior mold alignment collet 120 preferably has a plurality of air holes 124 or female air ports that direct free air from a free air supply (not shown) to the posterior surface 44 of the anterior mold 40. The free air ensures that dust and other impurities, which are generated as discussed below, are removed before the front mold 40 is placed in the hole 30 of the gasket 20.

The rear mold/gasket locating collet 130 has a gasket support flange 132 adapted to support the second end 24 of the gasket 20 thereon, the flange 132 being the end of the gasket 20 closest to the rear mold 50 disposed within the bore 30. As with the front mold 40, an operator, or alternatively an automated handling system, places the washer 20 with the back mold 50 therein onto the collet 130. Other means (not shown) for supporting the gasket 20 and the posterior mold 50 include separate collets, vacuum collets, clamping devices, or the like for each component.

As discussed above, the rear mold 50 is preferably placed in the aperture 30 of the gasket 20 prior to placing the rear mold 50 in the storage station. It is important that the posterior mold 50 be placed in a predetermined orientation within the aperture 30 of the gasket 20. The anterior and posterior molds 40, 50 need not initially be in a proper relative orientation to each other, but instead are in a known position from which one mold is later rotated to be properly aligned with the other mold.

The rotational position of the washer 20 is important when placing the washer 20 on the assembly station 110 so that the rear mold 50 will be in a known rotational orientation on the rear mold/washer positioning collet 130. The position of the gasket 20 is also important because it can have ports 38, 39 therein, with an injection needle and a vent needle inserted into the ports 38, 39. Thus, as shown in FIGS. 2 and 3, the preferred embodiment of the washer 20 is provided with a keyway 28 adjacent its second end 24 or other means of ensuring that the washer 20 is properly aligned on the support flange 132. In one embodiment, if the key slot 28 of the washer 20 is not properly aligned, an interlock (not shown) prevents the lens forming process from continuing. For example, the slide plate 112 will not move from the charging position to the assembly position until the gasket 20 is properly positioned on the rear mold/gasket locating collet 130 to meet the interlock conditions. The interlock may also provide a visual indication, such as a warning light on the assembly station 110 or a message on the computer-aided system controller.

The assembly station 110 also includes a means, preferably a movable arm, for inserting the front mold 40 into the aperture 30 of the gasket 20. Other contemplated embodiments of the anterior mold insertion device (not shown) include manually moving and inserting the anterior mold 40. Using slides, pneumatics, linear motors, portal robots and the like.

The movable arm employed in this embodiment picks up the anterior mold 40 placed on the anterior mold locating collet 120 and pushes the anterior mold 40 axially into the bore 30 of the washer 20, through the first end thereof until the posterior surface 54 of the anterior mold 40 contacts the insertion step 36 of the transition section 34. As discussed above in the description of the gasket, the transition portion 34 serves to position the front mold 40 in a fixed, known position and to form a substantially leak-proof seal between the front mold 40 and the step 36. Once the front mold is properly positioned in the bore 30 of the gasket 20, the movable arm is disengaged from the inserted mold and moved to an edge position, or alternatively, the movable arm remains engaged with the front mold 40 to support the gasket 20 on the rear mold/gasket-positioning step 130.

In a preferred embodiment, the movable arm is a robot 160, as shown in fig. 5 and 10, having a pneumatic clamp 162 that removably engages the front surface 42 of the anterior mold 40. Robot 160 is commercially available from mitswishi^The ELECTRONIC is commercially available under the trademark "MOVEMASTER RV-M2". The computer-assisted system guides and controls the operation of the manipulator 160. Mechanical arm160 may also include an internal computer that is linked to the computer-assisted system to control the movement of the robot 160.

As can be better seen in fig. 10, the body of the robot 160 is disposed within the perimeter of the enclosure 102. A shoulder 164 connects the body of the robot 160 to its upper arm, which is connected by an elbow 166 to a forearm 167. The pneumatic clamp 162 is connected to the forearm 167 of the robot 160 at a wrist joint 168. The robot 160 has a full range of motion due to horizontal rotation at the center of rotation on the floor and vertical lift created by the motion of the robot shoulders 164, elbows 166 and wrists 168. A wrist tool plate 169 interposed between the robot's pneumatic clamp 162 and wrist 168 and attached to them provides sufficient rotational movement for the pneumatic clamp 162. The robot 160 provides 5 degrees of freedom (excluding hands) and a large position memory, is driven by a DC servo motor (not shown), and includes pneumatic lines (not shown) of internally given course.

When moving the anterior mold 40 into the bore 30 of the washer 20, and when the anterior mold 40 is placed on the anterior mold locating collet 120, regardless of its initial orientation, one embodiment contemplated by the present invention requires the robot 160 to position the anterior mold 40 in a desired orientation, i.e., the robot 160 twists the anterior mold 40 to properly position it within the bore 30 in a predetermined orientation relative to the washer 20 when necessary. However, the anterior mould 40 will need to be marked by means of a device detectable by the robot 160, so that the robot 160 has a reference point.

The assembly station 110 also preferably includes a means for inserting the posterior mold 50 into the aperture 30 of the gasket 20. The rear mold insertion means, which is part of the rear mold/gasket locating collet 130, also preferably includes a means for removing the rear mold 50 from the bore 30 of the gasket 20. Thus, the rear mold inserting apparatus can both insert the rear mold 50 into the hole 30 and remove the rear mold 50 from the hole 30.

The posterior mold insert apparatus preferably includes a movable piston 134 adapted to removably engage a portion of the posterior mold 50 (e.g., the posterior surface 54 thereof) and remove the posterior mold 50 from the bore 30 of the gasket 20 or insert the posterior mold therein. More specifically, the posterior mold insertion means includes a mold support plate 136 adapted to removably engage the posterior surface 54 of the posterior mold 50 and a means connected to the mold support plate 136 for moving the mold support plate, the movable mold support plate 136 for the posterior mold 50 being defined by the support flanges 132 of the posterior mold/gasket positioning collet 130.

The mold support plate 136 is movable between an insertion position (where the mold support plate 136 is substantially at the same height as the support flange 132) and a retracted position, shown in fig. 7. In the retracted position shown in fig. 8, the mold support plate 136 is moved or retracted to a support frame 138, the support frame 138 including a plurality of upstanding support bars 139 extending between the support flange 132 and a cylinder mounting plate 140. When fully in the stowed position, the mold support plate 136 is positioned adjacent the cylinder seating plate 140. A portion of the "T" shaped piston 134, which moves within the cylinder 142, is fixedly attached to the mold support plate 136. The "T" shaped piston 134 is preferably controlled by compressed air and moves in response to positive air pressure applied to the cylinder 142 through an appropriate air port, although other actuation means, such as an electric solenoid, may be used. That is, the piston 134 moves upward within the cylinder 142 in response to pressurized air applied through the first port 144, and the piston 134 moves downward in response to pressurized air applied through the second port 146. The mold support plate 136 correspondingly moves with the attached piston 134.

When the back mold 50 and gasket 20 are loaded onto the back mold/gasket locating collet 130, the back mold 50 abuts the mold support plate 136. A plurality of vacuum ports 148 are provided in the mold support plate 136, the vacuum ports 148 being connected to a vacuum source (not shown). The vacuum port 148 communicates with and creates a suction force on the back surface 54 of the posterior mold 50 when the mold support plate 136 is in the inserted position, by the action of the vacuum source. The suction force is sufficient to draw and separate the posterior mold 50 from within the aperture 30 as the mold support plate 136 moves toward the stowed position. That is, the rear mold 50 is withdrawn from the hole 30 by the action of the vacuum source and the simultaneous movement of the rear mold support plate 136 to the retracted position. In the preferred embodiment, the time at which the rear mold 50 is retracted from the gasket 20 is substantially the same as the time at which the robot 160 removes the front mold 40 from the front mold locating collet 120 and inserts it through the first end 22 of the gasket 20.

The invention also includes a means for rotating the washer support means relative to the long axis L of the washer 20. A light diffusing mold surface has different radii on different axes. Those skilled in the art will appreciate that the orientation of the posterior mold 50 relative to the anterior mold 40 is critical, particularly for anterior molds designed to form a multifocal lens with an additional thickness. Thus, it may be desirable to adjust the rotational position of the back mold 50 relative to the front mold 40, which may occur when a rotational device is used to place the back mold 50 in the stowed position.

The rotation includes the computer-aided system described above which directs a support flange 132 or mold support plate 136 to rotate or twist the washer 20 or the back mold 50, respectively, a desired number of degrees, if necessary. The pressurized air then moves the piston 134 and the die support plate 136 back to the inserted position so that the rear die 50 is reinserted into the aperture 30 of the gasket 20 in the orientation in which it has been rotated. Thus, when reinserted, the posterior mold 50 will be in a desired rotational orientation relative to the anterior mold 40, which provides a proper orientation of the astigmatic posterior mold 50 relative to the anterior mold 40. It is presently preferred to rotate the support flange 132 and attached washer 20 and front mold 40 rather than rotating the mold support plate 136 to which the back mold 50 is mounted.

Preferably, the present invention further includes a means for determining a selected dimension of the posterior mold 50, and in particular the height of the posterior mold 50. This preferred embodiment of the present invention operates on the premise that the dimensions of the anterior mould tool are maintained within a specified tolerance, which is quite accurate due to the grinding techniques used to form the anterior mould tool. However, when the mold is placed horizontally, this premise is not accurate enough for the rear mold 50, particularly for its center thickness or height. That is, the height from the back surface 54 of the back mold 50 to the top of the front surface 52 of the back mold 50 for making the same type of lens may vary slightly in different back molds. The tolerance between posterior molds is the largest variation in forming the lens, and in fact may be greater than 5% (0.05) MM, and in the preferred embodiment this tolerance is the smallest tolerance required to ensure the desired precision of forming the lens. Thus, the present invention employs a determination device.

To determine the height of the posterior mold 50, in one embodiment, the determining means comprises a means for optically receiving at least a portion of the outline image of the posterior mold 50 when in the stowed position; a means for digitizing the image of the back mold 50, and a means for forming information from the digitized image of the back mold 50, such as information relating to the height and thickness of the back mold 50. The forming device generates a signal that is communicated to the computer-assisted system and stored in its memory-assisted system.

A camera 149, preferably an optical receiver, is provided for viewing the back mold when the mold support plate 136 is moved to the retracted position. A CCD or similar camera 149 records an image of the rear mold 50, and the digitizing means and forming means are used to determine the height of the rear mold 50. The camera 149 can also use gain control, an automated iris and the like to ensure that the image of the rear mold 50 is properly received.

The digitizing means may be a frame gripper (not shown), which is also referred to as a collector plate. Other contemplated embodiments of the digitizing means are a digitizing camera instead of an analog camera and frame holder, a scanning line sensor, and the like. The forming means and the digitizing means may be integrally formed as the same element.

In another embodiment, the molds 40, 50 may be pre-measured and marked with a bar code representing their measurements the operator scans the bar code and transmits the dimensions of the posterior mold 50 to a computer-assisted system prior to placing the posterior mold 50 onto the posterior mold/washer positioning collet 130. The bar code may be placed with printing on one mold surface (e.g., the front surface 52 of the back mold 50) so that the bar code image is transferred to the cured lens, which aids in tracking the lens. The bar code will then be replaced on the mold surface before it is used on another lens. The bar code transmitted to the lens will be located and cut off when the lens is used in eyeglasses. The back surface 54 of the back mold 50 itself is also etched with indicia that corresponds to the information in the bar code to be reprinted onto the front surface 52.

Since, in this embodiment, the computer-assisted system does not know in advance which of the plurality of posterior molds 50 is used for a given lens power, the computer-assisted system would be required to store and use a large directory of queries involving the different characteristics of the various specific molds. If the system uses, for example, 1000 molds, it will simply view each back mold 50 with the camera 149 or get information from a bar code. Thus, the height of each posterior mold 50 in this embodiment is determined, and this determined height is then used to calculate the desired axial separation distance between the molds 40, 50 and obtain a lens with the correct thickness. I.e., the determined height of the back mold 50, is used to calculate the distance the molds 40, 50 move axially in the bore 30 of the gasket 20.

Continuing the assembly process, the rear mold 50 is reinserted to be positioned adjacent the second end 24 of the washer 20, as opposed to being inserted to a calculated desired axial spacing. It is not necessary to open the hole to the space 31 formed between the two molds 40, 50 and the hole 30 because the distance the rear mold 50 is inserted into the hole 30 is short. As will be described in greater detail below, the injection station 200 preferably includes a means for axially moving the posterior mold 50 within the bore 30 to a desired spaced-apart distance from the anterior mold 40. Thus, the axial distance between the front and rear molds 40, 50 at the assembly station 110 is not critical.

However, in another embodiment, the posterior mold 50 is intended to be inserted into the bore 30 at a desired axial spacing distance from the anterior mold 40 using a posterior mold insertion device. Although not required, during adjustment in this alternative embodiment, it may be desirable to use a needle or other device to open the cavity 31 to ensure that the dies 40, 50 do not become misaligned with the inner surface 32 of the bore 30 when moved toward each other.

The last collet of the assembly station 110 is the clamp positioning collet 150. A means of securing the dies 40, 50 within the bore 30 is stored on the clamp locator collet 150. The clamp positioning collet 150 has an annular groove therein sized to receive the washer 20. The securing means of the lens shaping assembly 10 may optionally be added at this location. The fixture may be used to hold each mold stationary relative to each other within the bore 30 of the washer 20. Thus, when the molds 40, 50 are axially moved a desired distance apart from each other at the injection station 200, the fixture holds the molds 40, 50 firmly so that their relative positions do not change. Therefore, the securing means in this preferred embodiment is disposed around the outer surface 26 of the washer 20 on the clamp positioning collet 150 and is sufficiently secured to the perfusion table 200.

Referring to fig. 9, the preferred embodiment of the fixture is a radial clamp 152 that holds the position of the molds 40, 50 by defining and tightening the outer surface 26 of the washer 20. The preferred radial clamp 152 has a band portion 156 and an eccentric clamp 158 to secure the band. The tightened band presses the body portions of the gasket 20 inwardly to ensure that the molds 40, 50 do not change their relative positions and to strengthen the seal formed by the gasket 20 with the molds 40, 50. However, as the monomer shrinks during the curing process, the frictional forces between the gasket 20 and the molds 40, 50 do not prevent one mold (e.g., the back mold 50 in the case of a stepped gasket embodiment) from sliding toward the other mold. Another advantage of the radial clamp 152 is that it can also provide a handle member 154, such as a cam or other protrusion, for easy grasping by a robot 160 or operator when handling the lens-forming assembly 10.

When these components are aligned at the infusion station 110, the robot 160 moves the gasket 20 with the two molds 40, 50 in its bore 30 from the rear mold/gasket locating collet 130 to the clamp locating collet 150. The robot 160 also twists the washer 20, if necessary, prior to inserting the lens forming assembly 10 into the radial clamp 152 on the clamp positioning collet 150. If the washer 20 is twisted, for example, when the back mold 50 is in the retracted position, the robot 160 rotates the washer 20 while moving it to the clamp collet 150 so that the washer 20 is in a predetermined orientation. As this rotation occurs, the ports 38, 39 of the gasket 20 are in the correct position for insertion of the injection needle 252 and vent needle 232 on the infusion table 200, and the flat top will be oriented substantially upright when placed on the infusion table 200 to prevent pooling of air bubbles. If the plateau is not oriented properly, the high energy regions present due to surface tension at its edges have a tendency to trap bubbles along its edges.

Further, the radial clamp 152 may include a plurality of apertures (not shown) therethrough, wherein one aperture is aligned with a corresponding port 38, 39 of the gasket 20. The injection needle 252 passes through one port and the vent needle 232 passes through the other port so that the two needles 232, 252 communicate with the respective ports 38, 39 of the gasket 20.

Another embodiment of the present invention does not use a fixture. However the gasket should be thicker and the mould should fit tighter within the gasket to ensure that no leakage occurs. Such alternative embodiments are now less than ideal based on the automated manufacturing process technology used.

B. Irrigation platform

After assembling the gasket 20, molds 40, 50, and radial clamp 152 at the assembly station 110, the robot 160 moves the formed lens assembly to the casting station 200 shown in fig. 11. Robot 160 operating at assembly station 110 is shown in cross-section (phantom). The robot moving to another infusion station 200 is also shown in phantom (phantom).

Referring now to fig. 12-14, the injection station 200 preferably includes a means for supporting the lens-forming structure 10 and a means for axially moving the posterior mold 50 to a desired distance from the anterior mold 40, which is one of a number of axially spaced distances between the anterior mold 40 and the posterior mold 50 (e.g., moving the posterior mold 50 in a stepped gasket embodiment). The front mold 40 may alternatively be moved if a straight-walled gasket is used instead of a stepped gasket.

The infusion stage 200 has an upright support plate 210 supporting a top bracket 212 and a bottom bracket 214. The top bracket 212 supports a vent assembly 230 and the bottom bracket 214 supports a pour assembly 250.

The axial movement means preferably comprises a cylindrical piston 220 having one end adapted to fit a die sliding in the bore 30. A linear drive 222 or servo motor generating a certain output power is provided at the base of the frame and comprises a ball screw (not shown) over which a sled (not shown) passes or moves. A device, in particular a coupler 224, mechanically couples the linear actuator 222 to the piston 220, converting the output of the linear actuator 222 into movement of the piston 220. The piston 220 axially moves the rear mold 50 disposed within the bore 30 of the gasket 20 relative to the front mold 40. Fig. 13 shows the back mold 50 before the back mold is pushed along the hole 30 of the gasket 20, and fig. 14 shows the cylindrical piston 220 in the case where the back mold 50 has been pushed toward the front mold 40, so that there is a desired spacing distance between the front and back molds and the cavity 31 has a desired size. The linear drive 222 is operated using an electric or pneumatic source.

In one embodiment, the piston 220 further advances the posterior mold 50 into the bore 30 toward the anterior mold 40 as opposed to pulling the posterior mold 50. That is, the spacing between the anterior and posterior molds 40, 50 when assembled at the assembly station 110 is such that the pushing action is the only action exerted by the piston 220 on the posterior mold 50 to form the lens. However, a vacuum tube (not shown) connected to a vacuum source (not shown) may extend through the piston 220 to apply a vacuum force or suction to the back surface 54 of the back mold 50 to advance or retract the back mold 50. The vacuum tube also ensures that the piston 220, when advanced into the posterior mold 50, securely engages the posterior mold 50 so that the mold does not tilt, which could cause the lens to be improperly formed or the injected monomer to leak through the posterior mold 50.

The injection station 200 also includes a means for providing fluid communication between the aperture 30 or cavity 31 between the front and rear molds 40, 50 and the exterior surface of the gasket 20. In addition, the filling station 200 includes a means for injecting a desired amount of lens-forming liquid into the cavity 31. Such a delivery device is also referred to as a vent assembly 230 and the injection device is referred to as a priming assembly 250. Vent assembly 230 and irrigation assembly 250 are similar in structure and operation.

The vent assembly 230 includes a vent needle 232 having a bottom end 234 and a tip end 236 adapted to pierce a portion of the gasket 20. The tip 236 of the vent needle 232 is in fluid communication with the bottom end 234 thereof to allow fluid, such as air, to flow therebetween.

The vent assembly 230 also includes a means for moving the vent needle 232 between the first position and the second position. In a first position, as shown in figure 14, the tip 236 of the vent needle 232 is in fluid communication with the cavity 31, and in a second position, as shown in figure 13, the tip 236 is spaced from the gasket 20 and its aperture 30. The moving means is preferably a cylinder 240 that drives an injection piston 244 that contacts a coupler body 246. An injection support 242 holds the vent needle 232 and is fixedly connected to the coupler body 246. Thus, the injection support 242 and vent needle 232 move in response to the injection piston 244. A protective cap (not shown) may optionally cover the tip of the vent needle 232 when the vent needle 232 is in the second position.

The injection or priming device 250 comprises an injection needle 252 having an insertion end 254, a receiving end 256 adapted to be in fluid communication with a supply of lens forming fluid and a passage extending therebetween, the insertion end 254 passing through a portion of the gasket 20 to be in fluid communication with the cavity 31. The channel allows lens-forming liquid to flow from the receiving end 256 out of the insertion end 254 into the cavity 31 through the channel.

The infusion assembly also includes a means for delivering the needle 252 between an insertion position, shown in fig. 14, in which the insertion end 254 of the needle 252 is in fluid communication with the chamber 31, and a withdrawn position. In the pulled-out position shown in fig. 13, the insertion end 254 is spaced from the washer 20. The transfer device of the priming assembly is similar to the vent assembly 230 and includes a cylinder 260, an injection piston 262, a coupler body 264 and an injection support 266. Injection needle 252 is connected to an infusion catheter (not shown) in fluid communication with an infusion tube. A protective cap (not shown) may optionally cover the tip of the needle 252 when the needle 252 is in the withdrawn position.

As described above, the robot 160 moves the lens forming device 10 to the filling station 200 and places it on the supporting means of the filling station 200. The vent needle 232 is moved to the first position where the needle 232 is inserted into the gasket 20 to communicate with the cavity 31 through a port 39 of the gasket 20. In this way, the venting pins 232 allow air to escape from the cavity 31 so that atmospheric pressure exists between them when one mold is slid relative to the other by the piston 220 of the axial moving device.

The computer-aided system marks the coordinate system in which the anterior mold 40 is located, the anterior mold 40 abutting the step 36 within the gasket 20. A cylindrical piston 220 connected to the linear actuator 222 slides the back mold 50 to obtain the correct thickness of the desired lens to be formed. As discussed above, the computer-aided system has determined the actual height of the posterior mold 50 from images recorded by the camera 149 on the assembly station 110, bar code data, or other means. In this manner, the computer-assisted system, which utilizes the height of the particular posterior mold 50 predetermined during this process, directs the posterior mold 50 to be advanced a predetermined distance toward the anterior mold 40 to form a lens having the desired thickness. If greater accuracy is required, the computer-assisted system can adjust the axial separation distance to account for shrinkage (about 10% -15% of the volume) that occurs when curing the monomer. Upon axially moving the posterior mold 50, the anterior and posterior molds 40, 50 are in the correct rotational orientation relative to each other and are spaced apart from each other by the desired distance.

The next step in the process is to inject a lens-forming liquid (i.e. liquid monomer) into the cavity 31. The vent needle 232 has been connected to the cavity 31, preferably in communication with the cavity 31 at its highest point, and an injection needle 252 is inserted into another hole 38 in communication with the cavity 31. The monomer is then supplied into the cavity 31 through the injection needle 252. The present invention allows for efficient venting and filling of the cavity 31 regardless of the spacing of the front and rear molds 40, 50 and the amount of monomer to be injected.

As shown in fig. 13 and 14, the gasket 20 is arranged so that the injection port 38 is located below the vent port 39 so that any air bubbles that may form when the monomer is injected into the cavity 31 are effectively vented. However, the filling or injection rate used is slow enough that no bubbles are formed.

The filling station 200 includes a means for detecting the level of monomer being filled by the injection device. The sensing means preferably includes a means in fluid communication with the vent needle 232 to create a negative pressure both locally at the tip 236 of the needle 232 and in the cavity 31, and a means in fluid communication with the vent needle 232 to sense the pressure within the cavity volume. The vent needle 232 is connected to a vacuum source (not shown) via a first conduit 248, which conduit 248 draws approximately one-half inch of air from the tip 236 through the hole in the needle 232, thereby reducing the pressure in the tip 236 or the cavity 31 to a pressure less than atmospheric pressure, e.g., drawing a slight vacuum. For ease of description, the first tubing 248 is shown closer to the bottom end 234 of the needle 232 than in the preferred design. A second line (not shown) for detecting the degree of vacuum is connected to a vacuum sensor (not shown).

When the liquid monomer fills the cavity 31 and contacts the vent needle 232 (the vent needle 232 is disposed at the highest position in the cavity 31), the vacuum sensor detects an increase in pressure, e.g., a decrease in vacuum, which causes the computer-assisted system to shut off the infusion of the monomer. Those skilled in the art will appreciate that the amount of monomer wasted is only a few micrograms, such as the amount needed to fill a small portion of needle 232. In comparison, the amount of monomer wasted in prior art systems is large.

The vacuum used may be slightly less than atmospheric pressure. Since the main purpose of the vacuum is to act as a fill sensor rather than aid in filling, lower pressures are not required. That is, it would be beneficial if a vacuum were present in chamber 31, because the chance of bubble formation during filling is further reduced, but this advantage is not important compared to venting chamber 31 to atmosphere.

Those skilled in the art will appreciate that other sensors may be used to detect when the gasket 20 is full of cells, such as an electronic eye (not shown), other optical sensors (not shown), or the like.

An alternative way to carry out the filling process is to calculate the monomer volume injected into the cavity 31 by a computer-assisted system and to stop filling the cavity 31 once the calculated volume has been increased. Therefore, the use of sensors in this alternative filling method is optional. It is also contemplated that a predetermined amount of monomer will be injected prior to axially moving the molds 40, 50 toward one another so that the cavity 31 will be completely filled with monomer when the molds 40, 50 are at the desired axial spacing.

The location where the vent and injection needles 232, 252 are inserted into the gasket 20 may vary. In a preferred embodiment, needles 232, 252 are moved axially through a portion of gasket 20 until the respective needle tips are in fluid communication with ports 38, 39. The port is also in fluid communication with the cavity 31. This design is preferred for an alternative embodiment in which the respective needle 232, 252 passes through the washer 20 perpendicular to the outer surface 26 so that the needle tip is actually inserted into the cavity 31. Inserting vent needle 232 or a portion of injection needle 252 in this embodiment causes problems when forming a small thickness lens if anterior mold 40 and posterior mold 50 are axially separated by a small distance. A die having an annular ring 60 as shown in fig. 4 may be used for this small pitch case.

After filling is complete, the needles 232, 252 are retracted and the gasket 20 is sealed by a sealing means (preferably a self-sealing material via the gasket). The radial clamp 152 of the fixture can then be tightened to secure the molds 40, 50 within the bore 30 at the desired distance from each other. Those skilled in the art will appreciate that the radial clamp 152 may alternatively be tightened after the axial moving device has placed the back mold 50 in a correct position relative to the front mold 40 and prior to injecting the monomer.

The present invention may be used with multiple infusion stations 200 and assembly stations 110. For example, one embodiment uses two assembly stations and two infusion stations operating simultaneously. A single robot arm mounts one lens forming assembly while the other lens forming assembly is injected with monomer at the injection station. The robot then transfers the newly assembled lens forming structure to another filling station for filling, removes the lens forming assembly that has been injected with monomer, and then assembles the next lens forming assembly. This process may continue to repeat. Another contemplated embodiment has four stations and two robots, one for assembling and placing the lens shaping assembly in the infusion station and one for removing it from the infusion station. Those skilled in the art will appreciate that other alternative embodiments having different numbers of manipulators and perfusion stations may be employed.

Curing method

The robot 160 removes the monomer injected lens forming assembly 10 from the infusion station 200 and transfers it to an operator or other automated system to cure the monomer. The curing process of the present invention involves exposing the monomer to an ultraviolet ("UV") light for a desired period of time, which is much shorter than in the prior art. The UV ray exposure described in this preferred embodiment is the only step. Alternatively, when the monomer is exposed to UV light, the monomer is then heated for a predetermined period of time, for example in an infrared ("IR") oven for a predetermined period of time. This second heating step cures the monomer to form a hardened polymerized lens if not sufficiently cured in the UV step.

The desired exposure time under UV light is between 20 seconds and 30 minutes, more preferably between 30 seconds and 2 minutes, most preferably between 45 seconds and 1 and a half minutes. The exposure process is performed by placing the monomer between a plurality of UV light sources, preferably one adjacent each end of the gasket 20, so that the UV light passes through the glass mold to the monomer entering the cavity 31. The intensity of the UV light source 312 is preferably about 1.2 to 1.3X 10-2 watts per square centimeter at a wavelength of 350 nanometers.

The exposure process of the lens forming assembly 10 can be automated by, for example, using the curing station 300 shown in fig. 15. The operator connects the handle member 154 of the clamp 152 to a movable cylindrical rod 310 which moves the clamp 152 and lens forming assembly 10 upwardly. In the top position, each of the two molds 40, 50 is exposed to a UV light source 312 so that the UV light source passes through the molds to interact with the monomer. A computer-assisted system or other automated or manual means energizes the UV light source for a predetermined period of time, after which the movable cylindrical rod 310 is lowered so that the operator can remove the fixture 152 and lens shaping assembly 10.

Because of this unique gasket design, the curing process of the present invention is relatively fast and less complex, and more efficient than prior art processes. This curing process completely cures the monomer and reduces the stress in the cured monomer so that the cured lens is stronger than a lens cured using prior art processes. Stress is also reduced because the back mold 50 slides along the bore 30 of the gasket 20 as the cured monomer volume shrinks by about 10-15%. In contrast, the die of the prior art T-shaped gasket remains stationary regardless of the stress due to shrinkage.

Separation device and method

When the liquid monomer has been cured, the cured lens must be separated from the gasket 20 and the molds 40, 50. Since the gasket 20 is flexible, the two molds 40, 50 and the lens clamped between them can easily slide out of the gasket 20 when the radial clamps 152 are removed. However, separating the molds 40, 50 from the lens is more difficult because of the strong bond formed by surface tension between the lens and the mold with which it is in contact. The present invention also includes an apparatus and method for separating molds 40, 50 from a newly formed lens.

Referring to fig. 16, the separating device 400 of the present invention includes a means for supporting the lens and the mold and a means for directing a fluid onto a portion of at least one of the lens or the mold. Those skilled in the art will appreciate that the mold and lens have different coefficients of thermal expansion because they are made of different materials. The fluid is preferably a gas having a temperature lower than the temperature of the mold and lens just removed from a heat source such as a UV light or IR oven. The temperature of this gas is typically lower than the ambient temperature and the temperature of the lens and mold is higher than the ambient temperature.

Gases that may be used include pressurized air, oxygen, nitrogen, and more preferably carbon dioxide ("CO₂"). The gas guided by the guide means cools the sameThe hotter mold-lens-mold sandwich 410 allows the glass mold to shrink with the cured monomer. Due to the different coefficients of thermal expansion of the glass and copolymer lenses being cooled, there is a different shrinkage between the two materials. This differential shrinkage helps break the surface bond between the respective surfaces of the molds 40, 50 and the lens. Those skilled in the art will appreciate that the greater the temperature difference between the gas and the mold-lens-mold sandwich 410, the faster the cooling and the more effective the separation of the lens from the mold 40, 50.

The directing means comprises a nozzle 412 connected to a gas supply 418 at a pressure above atmospheric pressure. The nozzle 412 has an inlet 414 in fluid communication with a gas source 418 and an outlet 416 for directing the gas onto the lens and mold, particularly onto the interface of the lens and a mold. As one example, each nozzle 412 may have an inner diameter of about 3mm and decrease to about 3/10(0.3) mm at outlet 416. Such a nozzle 412 allows the fluid flowing from the nozzle to increase to a very high velocity. Such a guide means comprises one nozzle 412, more preferably two nozzles, preferably four nozzles, arranged at about 90 ° intervals around the edge of the mold-lens-mold sandwich 410. Fig. 16 shows an embodiment with four nozzles 412.

The support means comprises a horizontally disposed member 420 having an upper surface 422 adapted to support the lens and mold thereon and an opposing lower surface 424. The preferred support means also has a rotational R axis. The invention further comprises means for moving a selected one of the support means of the guide means or the nozzle 412 relative to the other. Those skilled in the art will appreciate that the nozzle 412 can be rotated relative to the mold-lens-mold sandwich 410, that the nozzle 412 and such sandwich 410 can be rotated in different directions, or that both the nozzle 412 and the sandwich 410 can be rotated in the same direction at different speeds so that there is relative motion therebetween. It is also envisaged that there is no relative movement between the guide means and the support means.

However, in this preferred embodiment, the support device is rotated about its axis of rotation R, while the nozzle 412 remains stationary, so that the mold-lens-mold sandwich 410 rotates relative to said nozzle 412. The means for rotating the member 420 preferably includes a motor 430 for generating a rotational output power and a portion 432 having opposite ends. The portion 432 is connected at one end to the motor 430 and at the other end to a portion of the lower surface 424 of the member 420 so that the output of the motor 430 rotates the member 420 about an axis in the direction of rotation R. The motor 430 may be electric, pressurized air driven, or driven by other means known in the art.

Referring to fig. 16, the outlet 416 of each nozzle 412 is preferably disposed at a different height relative to the other outlets 412 because at least one outlet 416 of one nozzle 412 should be directed to the interface of the lens and an adjacent mold regardless of the thickness of the lens. That is, each nozzle 412 directs gas to a different height above the edge of the mold-lens-mold sandwich 410 to cool the materials. The combined rotary devices provide relative rotational movement between the mold-lens-mold sandwich 410 and the nozzle 412. Directing the gas at the interface of the lens and the mold is helpful because after the gas exits the outlet 416 of the nozzle 412, the gas expands and spreads to cover a vertical height of about 1mm or more, depending on such factors as the gas velocity, nozzle design, and the separation distance between the outlet 416 of the nozzle 412 and the mold-lens-mold sandwich 410.

When this preferred high velocity CO2 gas is directed from nozzle 412 onto the interface of the lens and one of the molds 40, 50, some of the gas molecules reach the interface between them. It is believed that some of the CO2 gas becomes "dry ice" when it reaches the mold-lens-mold sandwich 410 and expands after penetrating into the space existing between the lens and one of the molds. This expansion forces the adjoining lens and mold away from each other, helping to break the intimate contact of these elements. The infiltrated CO2 additionally cools the lens and mold at their interface to accelerate differential shrinkage between them. Moreover, the more separation that occurs, the deeper the CO2 can penetrate to continue this expansion and cooling. The apparatus and method of the present invention enable the mold and lens to be separated without the need for any external physical or mechanical shear forces applied to these elements.

However, the invention may also include a means for physically bending a selected one of the lens or mold. The preferred bending means comprises at least two engagement members (not shown), each having a contact surface adapted to releasably engage a separate portion of the lens, and a means for moving the engagement members relative to each other, such that the respective contact surfaces cause the lens to bend. Such contact surfaces may be shaped as crenulations, knurled surfaces, or other shapes that prevent slippage between the engaging member and the lens edge.

The moving means comprises at least one actuator for generating an output, a means for mechanically coupling each linear actuator to the corresponding engagement member, and a means for energizing the actuator. The output of the driver translates into movement of the combined engagement member. Thus, the contact surface of this engaging member presses inwardly on the plastic lens to deform it away from the glass mold, thereby causing a slight physical deformation to break the surface tension bond therebetween. The opposite edge of the lens can be placed against either a stationary engagement or another engagement in combination with a separate drive, wherein the two drives move their respective engagement toward each other. Physically deforming the lens is less desirable than separating the elements using a cooling gas.

Another method of separating the lens from the mold is for the operator to submerge these elements in soapy water. This alternative method enables simultaneous cleaning and separation of the lens and mold.

After the molds 40, 50 have been separated from the cured lens, the molds 40, 50 and gasket 20 can be reused or scrapped. If these components are to be reused, the operator places the rear mold 50 in the bore 30 of the washer 20 in a predetermined rotational orientation relative to the washer 20. An operator may use an assembly positioning device 500 as shown in fig. 17A and 17B to assist in inserting the posterior mold 50 into the bore 30 and to reduce the physical manipulation of the posterior mold 50.

The gasket 20 can be reused to manufacture another lens if it is acceptable. However, the life of the gasket 20 is much shorter than that of the glass mold. If the gasket 20 requires extensive cleaning or has been damaged, it is scrapped and ground for reuse.

The assembly positioning device 500 has a central portion 510 adapted to horizontally support the rear side of the rear mold 50. Surrounding the central portion 510 of the assembly alignment device 500 is a spring load receiving member 512 adapted to engage the second end 24 of the washer 20. In this way, the central portion 510 secures the back mold 50 and the gasket 20 is pushed down against the spring load receiving member 512 so that the back mold 50 is received within the aperture 30 of the gasket 20.

The posterior mold 50 is marked, for example, by a line engraved on one of its surfaces that is not in contact with the monomer when forming the lens, such as the posterior surface 54. The operator aligns the rear mold 50 in a desired rotational orientation relative to the alignment device. For positioning on assembly table 110, the rotational orientation of the toric back lens (toric back lens) relative to the washer 20 must be in a known position. The operator then places the washer 20 over the assembly fixture 500 and rotatably orients a mark on the washer 20 to align with the score line on the back mold 50. In this preferred embodiment, the washer 20 will only be received by the assembly fixture when the washer 20 is in the desired rotational orientation, which helps to ensure that the washer 20 and the back mold 50 are in the desired rotational orientation relative to each other. The keyway 28 may be used to ensure that the washer 20 is properly aligned with the spring load receiving member 512. Figure 17A shows the components properly aligned.

Fig. 17B shows the operator having pushed the washer 20 down on the assembly fixture 500 so that the rear mold 50 is received into a portion of the bore 30. When the operator starts to push down, the washer 20 moves against the spring force and receives the back mold 50 into its hole 30. When the rear mold 50 is axially received into the bore 30 a predetermined distance, the movement of the gasket 20 is stopped by the receiver 512, and the receiver 512 cannot be further compressed. Therefore, the rear mold 50 is placed within the hole 30 for a desired distance.

While the axial position of the posterior mold 50 within the bore 30 is not critical, the assembly apparatus ensures that the posterior mold 50 is consistently placed the same distance each time, rather than varying from operator to operator. This improves the operation of the present invention by, for example, ensuring that the back mold 50 does not become inserted too far into the aperture 30 to prevent operation of the mold support plate 136, the support plate 136 moving the back mold 50 to the stowed position at the assembly station 110. Those skilled in the art will appreciate that this process can be automated such that a robot or the like performs the process to place the rear mold 50 in a known rotational orientation within the aperture 30 of the gasket 20.

From the viewpoint of handling, it is also relatively easy to store the rear mold 50 in the gasket 20. Since the surface 44, 52 of the mold used to form the lens is a sensitive surface, contaminants, such as those on a person's fingers, can also damage it. The other surfaces 42, 54 of the contact molds 40, 50 that are not used to form the lens shape are not problematic. It is not a problem for the back mold 50 to be oriented with the front surface 52 facing the interior of the gasket 20, while the back surface 54 is manipulated. Since it is easy to place the rear mold 50 in the hole 30, the sensitive side is protected by the gasket 20, and the front mold 40 is manipulated by the front surface 42 of the front mold 40, for example, the robot 160 contacts the front surface 42 thereof.

The anterior mold 40 and the gasket/posterior mold 20, 50 are then moved to the appropriate storage area proximate the assembly station 110 to form additional lenses. For example, the operator places these components on a moving belt. The anterior mold 40, which may be stored in one transfer tool, is placed on one belt and the gasket/posterior mold 20, 50 is placed on the other belt. If necessary, sensors detect the dies reaching the ends of the belts and stop the movement of the respective belts. Another operator at the end of the belt then places the components in the correct storage position so that the process of the invention can be repeated.

Although the invention has been described in detail with reference to specific embodiments thereof, it should be noted that such detail is not to be considered as limiting the scope of the invention, which is defined by the appended claims.

Claims (40)

1. An apparatus for assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, an outer surface, and a longitudinal axis and defining an axially-extending bore, the apparatus comprising:

a. means for supporting said gasket so that at least one of said front mold or said rear mold is inserted into said gasket hole;

b. means for inserting the anterior mold into a gasket bore;

c. means for inserting the rear mold into a gasket bore;

d. means for axially moving a selected one of the front or rear dies relative to the other within the bore of the gasket to provide a desired axial separation distance between the dies.

2. The apparatus of claim 1, wherein said post-mold insertion means further comprises means for removing the post-mold from the aperture of said gasket so that the post-mold insertion means can insert the post-mold into said aperture and remove it therefrom.

3. The apparatus of claim 2, further comprising means for rotating a selected one of the washer support means or the post-mold insertion means relative to the long axis of the washer, wherein the rotating means rotates the selected one of the washer support means or the post-mold insertion means after the post-mold insertion means removes the post-mold from the aperture of the washer, such that the washer is in a different rotational orientation when the post-mold insertion means reinserts the post-mold into the aperture.

4. The apparatus of claim 2, wherein the posterior mold insertion apparatus comprises:

a. a mold support plate adapted to removably engage a portion of said back mold when the gasket is placed on the gasket support means;

b. a means connected to said mold support plate for moving said mold support plate between an insertion position wherein said mold support plate abuts a portion of said gasket support means and a retracted position wherein said mold support plate is spaced from said gasket support means.

5. The apparatus of claim 4, further comprising means for rotating a selected one of the gasket support means or the post-mold insertion means relative to the long axis of the gasket, wherein the rotating means rotates the selected one of the gasket support means or the post-mold insertion means after the post-mold insertion means removes the post-mold from the aperture of the gasket so that the gasket is in a different rotational orientation when the post-mold insertion means reinserts the post-mold into the aperture.

6. The apparatus of claim 4, further comprising means for determining a selected dimension of said posterior mold.

7. The apparatus of claim 6, wherein the determining means comprises:

a. a means for optically receiving at least a portion of an image of the posterior mold profile when in said retracted position;

b. a means for digitizing said post-mold image;

c. a means for creating data from the digitized image of the rear mould, comprising data relating to the height of the rear mould, wherein the creating means generates a signal containing the data.

8. The apparatus of claim 1, wherein the axial movement means comprises:

a. a plunger adapted to removably engage a selected one of the two molds when said molds are placed in the bore of said gasket;

b. a driver for generating an output;

c. a means for mechanically coupling said driver to a portion of said piston to convert the output of the driver into movement of the piston;

d. a means for supplying energy to said driver.

9. The apparatus of claim 1, further comprising means for securing said molds within said bore at a desired spaced distance from each other.

10. The apparatus of claim 9, wherein the securing means comprises a radial clamp.

11. The apparatus of claim 1 wherein said anterior mold insertion means is a robot adapted to removably engage a portion of said anterior mold, insert said anterior mold into said gasket bore at a predetermined axial position and then separate from said inserted anterior mold.

12. The apparatus of claim 1, further comprising means for providing fluid communication between the outer surface of the gasket and the bore between the front and rear molds to facilitate axial movement of the molds relative to each other within the bore of the gasket.

13. The apparatus of claim 12, wherein the providing means comprises:

a. a vent needle having a base end and a tip end adapted to communicate with the bore through a portion of said gasket, wherein said base end is in fluid communication with said tip end to allow fluid to flow therebetween;

b. means for moving said vent needle between a first position in which the tip of the vent needle is in fluid communication with the aperture of the gasket and a second position in which said tip is spaced from the gasket and its aperture.

14. The apparatus of claim 1, wherein said gasket support means further comprises means for indicating proper alignment of a gasket supported thereby.

15. The apparatus of claim 1 further comprising means for injecting a lens-forming liquid into the bore of the gasket between the front and rear molds.

16. The device of claim 15, wherein the injection device comprises:

a. a needle having an insertion end, a receiving end and a passageway therethrough, said insertion end passing through a portion of said gasket to communicate with the bore of the gasket between the front and rear molds, said receiving end being adapted to be in fluid communication with a supply of lens forming liquid, said passageway therethrough allowing said lens forming liquid to pass through said receiving end through said passageway and out of said insertion end to communicate with said bore;

b. means for transferring said needle between an insertion position wherein the insertion end of said needle is in fluid communication with the washer bore and a retracted position wherein said insertion end is spaced from the washer and its bore.

17. An apparatus for assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, a longitudinal axis and defining an axially extending bore at their ends, the apparatus comprising:

a. means for supporting said gasket so that said front and rear molds are insertable into said gasket opening;

b. means for inserting the anterior mold into a gasket bore;

c. means for inserting the rear mold into a gasket bore;

d. means for rotating a selected one of the front mold, the back mold or the gasket relative to the long axis of the gasket so that when the two molds are inserted into the bore of the gasket they are in one of a number of selected rotational orientations relative to each other.

18. An apparatus for assembling a lens-forming structure having a front mold, a back mold, and a gasket defining an axially extending bore, the apparatus comprising:

a. a gasket support supporting said lens forming structure;

b. a robot adapted to removably engage a portion of said anterior mold and insert said anterior mold into said gasket bore;

c. a movable piston adapted to removably engage a portion of the posterior mold and insert the posterior mold into the gasket bore, wherein at least one of the robot or the piston axially moves the respective engaged anterior mold or posterior mold within the gasket bore to a desired one of a plurality of axially spaced apart positions relative to the other mold, wherein the spacing distance between the molds within the gasket bore is different for each desired axially spaced apart position.

19. A method of assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, an outer surface, and a longitudinal axis and defining an axially-extending bore, the method comprising:

a. supporting the gasket so that the front mold or the rear mold can be inserted into the gasket hole;

b. inserting the rear mold into the hole of the gasket;

c. inserting the front mold into the hole of the gasket;

d. a selected one of the front or rear molds is axially moved relative to the other mold within the bore of the gasket such that there is a desired one of a plurality of axially spaced distances between the two molds.

20. The method of claim 19, further comprising, prior to said axially moving step, the steps of:

a. removing the rear mold from the gasket bore;

b. rotating one of the back mold or the washer relative to the other about the long axis of the washer;

c. reinserting the rear mold into the bore so that the front and rear molds are in a selected rotational orientation relative to each other.

21. The method of claim 20, further comprising the step of determining the post-mold height after said removing step.

22. The method of claim 21, wherein said determining step comprises:

a. optically receiving an image of said back mold to form an output;

b. transmitting the output to a controller;

c. the height of the back mold is calculated from the optically received image.

23. The method of claim 20, wherein the removing step comprises:

a. positioning a mold support plate adjacent an end of said gasket adjacent a posterior mold, the mold support plate adapted to removably engage a portion of said posterior mold;

b. repositioning the mold support plate to a retracted position.

24. The method of claim 20 further including the step of providing fluid communication between the outer surface of the gasket and the bore between the front and rear molds to facilitate axial movement of the molds relative to each other.

25. A method of assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, a longitudinal axis and defining an axially extending bore at their ends, the method comprising:

a. supporting the gasket so that the front mold and the rear mold can be inserted into the hole of the gasket;

b. placing the front mold in the hole of the gasket;

c. rotating the selected one of the back mold or the washer relative to each other about a long axis of the washer, the front mold being disposed in the bore of the washer;

d. inserting the rear mold into the bore of the washer such that the front and rear molds are in a selected rotational orientation relative to each other within the bore.

26. An apparatus for forming a lens using a structure comprising a front mold, a back mold and a gasket having opposite ends and defining an axially extending bore, wherein said front and back molds are disposed within said bore and spaced apart from one another therein, the apparatus comprising:

a. means for supporting the structure;

b. means for axially moving a selected one of the front or rear molds relative to the other mold within the bore of the gasket to a desired one of a plurality of axially spaced distances between the molds;

c. means providing fluid communication between the outer surface of the gasket and the bore between the front and back molds to facilitate axial movement of the molds relative to each other;

d. means for injecting a desired amount of lens-forming liquid into the gasket hole between the anterior and posterior molds.

27. The apparatus of claim 26, wherein the axial movement means comprises:

a. a plunger adapted to engage a selected one of the two molds when said molds are placed in the bore of said gasket;

b. a driver for generating an output;

c. a means for mechanically coupling said driver to said piston to convert the output of the driver into movement of the piston;

d. a means for supplying energy to said driver.

28. The apparatus of claim 26, further comprising means for securing said molds within said bores at a desired spaced distance from one another.

29. The apparatus of claim 28, wherein said securing means comprises a radial clamp.

30. The apparatus of claim 26, wherein the providing means comprises:

a. a vent needle having a base end and a tip end adapted to communicate with the bore through a portion of said gasket, wherein said base end is in fluid communication with said tip end to allow fluid to flow therebetween;

b. means for moving said vent needle between a first position in which the tip of the vent needle is in fluid communication with the aperture of the gasket and a second position in which said tip is spaced from the gasket and its aperture.

31. The apparatus of claim 30, further comprising means for detecting the level of lens forming liquid injected by said injection means into the volume formed within said structure.

32. The apparatus of claim 31, wherein the detecting means comprises:

a. a means in fluid communication with said vent needle for creating a sub-atmospheric pressure in a portion of said vent needle;

b. a means in fluid communication with said vent needle for sensing pressure within said vent needle, wherein when said volume is filled with said lens forming liquid, the pressure sensed by the pressure sensor increases so that said lens forming liquid is in communication with the tip of said vent needle.

33. The device of claim 26, wherein the injection device comprises:

a. a needle having an insertion end, a receiving end and a passageway therethrough, said insertion end passing through a portion of said gasket to communicate with the bore of the gasket between the front and rear molds, said receiving end adapted to be in fluid communication with a supply of lens forming liquid, said passageway permitting said lens forming liquid to pass through said passageway through the receiving end to exit said insertion end to communicate with said bore;

b. means for transferring said needle between an insertion position wherein the insertion end of said needle is in fluid communication with the washer bore and a retracted position wherein said insertion end is spaced from the washer and its bore.

34. An apparatus for forming a lens, comprising:

a. means for supporting a lens-forming structure having a gasket defining an axially extending bore, a front mold and a back mold, wherein said front and back molds are disposed within said bore and spaced apart from one another therein;

b. means for axially moving a selected one of the front or rear molds relative to the other mold within the bore of the gasket to provide a desired one of a plurality of axially spaced distances between the molds.

c. Means providing fluid communication between the outer surface of the gasket and the bore between the front and back molds to facilitate axial movement of the molds relative to each other;

d. and injecting a desired amount of lens-forming liquid into the gasket hole between the anterior mold and the posterior mold.

35. An apparatus for assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, a longitudinal axis and defining an axially extending bore, the apparatus comprising:

a. means for supporting said lens forming structure;

b. means for moving a selected one of said front and rear molds to a desired one of a plurality of axial positions while said molds are disposed in said bore of said gasket, wherein the separation distance between the two molds in said bore of said gasket is different for each desired axial position.

36. An apparatus for assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, a longitudinal axis and defining an axially extending bore, the apparatus comprising:

a. a support for said lens-forming structure;

b. a plunger adapted to removably engage a selected one of said front and rear molds when said molds are disposed within said apertures of said gasket;

c. a driver for generating an output;

d. a mechanical coupling connecting said actuator to a portion of said piston such that the output of the actuator is translated into movement of said piston, said piston moving said removably engageable die to a desired one of a plurality of axial positions, wherein the separation distance between the two dies in said gasket bore is different for each desired axial position;

e. means for supplying energy to said driver.

37. A method of assembling a lens-forming structure having a front mold, a back mold, and a gasket having opposed ends, an outer surface, and defining an axially extending bore, the method comprising:

a. inserting the rear mold into the hole of the gasket;

b. inserting the front mold into the hole of the gasket;

c. after the mold has been inserted into the gasket bore, the desired amount of lens-forming liquid is injected into the bore of the gasket between the front and back molds.

38. The method of claim 37 further including the step of axially moving a selected one of said front or rear molds relative to the other mold within said bore of said gasket to provide a desired one of a plurality of axially spaced distances between said molds.

39. The method of claim 38, wherein said axially moving step is performed prior to said injecting step.

40. The method of claim 37 further including the step of providing fluid communication between the outer surface of said gasket and the bore between said front and rear molds to facilitate said injecting step.