Patent Publication Number: US-2010129484-A1

Title: Mold system for producing ophthalmic devices

Description:
PRIORITY CLAIM 
     Priority is claimed from U.S. provisional patent application Ser. No. 61/200,239, entitled “Mold System for Producing Ophthalmic Devices” filed Nov. 26, 2008, which is fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to molds and molding machines for producing ophthalmic devices and more particularly, to an improved system for manufacturing and storing contact lenses. 
     BACKGROUND INFORMATION 
     Prior art injection molding machines for the manufacture of contact lenses typically comprise two mold halves such as those taught by Homer et al. in U.S. Pat. No. 5,252,056. Homer et al. provides a contact lens manufacturing process wherein two mold halves, manufactured by injection molding, are configured to be joined together. One mold half has a convex shape and the other has a concave shape. A material such as a liquid monomer mixture is introduced between the mold halves such that when the mold halves are joined together, and the material undergoes a polymerization process, a contact lens is formed having a least one optically critical side and a mostly perfect edge which can be subsequently manipulated as necessary. The molds themselves are then used to transport and store the contact lenses. This serial manufacture of contact lenses requires significant cycle time due to the successive swapping of mold halves. 
     In U.S. Pat. No. 5,782,460, incorporated herein by reference, a molding system is provided that forms ophthalmic devices having a geometry determined by the contour of the two mold halves in the region in which they are in contact with one another such as female and male inserts. The female inserts receive a flowable starting material in excess of that required to form a contact lens and the mold halves are closed. When the mold halves are closed a polymerization process occurs allowing the contact lens material to be fully cured. In prior art molding systems such as that taught in the &#39;460 patent, the molds were disposable and only used once due, at least in part, to their contamination from the excess material or deformation, for example. 
     U.S. Pat. Nos. 6,592,356 and 7,156,638 to Lust et al., both incorporated herein by reference, describe an apparatus for molding ophthalmic devices such as contact lenses, interocular lenses, and lens curves used for making contact lenses. An injection molding machine is provided with a hot runner in the base of the apparatus configured to provide molten thermoplastic material, e.g. polystyrene, to a first mold half and a second mold half wherein each half is configured to produce front lens curve(s) and/or back lens curve(s). Further, a second mold half includes a plate mounted on the hot runner base which has been bored out to receive inserts configured to form the non-critical surfaces of the lens curves a first mold half includes changeable cassette(s), or insert retainers, which are removably attached to the base of the first mold half and which comprise a plurality of inserts. 
     Removable cassettes allow for reduced cycle time because removing and replacing a mold half may require the use of a hoist due to its relative size and weight as compared to a cassette. Therefore, cassettes are more easily moved and stored and allow for a significant increase in efficiency, particularly in the case of serial manufacture of stock keeping units (SKUs). SKU refers to ophthalmic devices having different powers, cylinders, and/or axis values for example, such that a different mold, mold orientation, and/or reactive mixture within the mold is required. Further, since an optimum molding temperature range is required to produce effective lens curves, cassettes allow for reduced preheating because upon removal and replacement of successive cassettes in a mold base, the mold base will have retainer at least some heat resulting in less down-time and less waste. 
     There is a need in the art for an improved system and method for manufacturing and storing contact lenses which increases the efficiency of insert changes and device storage in order to reduce cycle time, downtime, and required storage space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages will be better understood by reading the following detailed description, taken together with the drawings wherein: 
         FIG. 1  is a perspective view of a first mold half. 
         FIG. 2  is a perspective view of a second mold half. 
         FIG. 3   a  is a perspective view of an insert retainer including a plurality of inserts. 
         FIG. 3   b  is a side plan view of an insert retainer. 
         FIG. 4  is a front view of an insert retainer including an insert cooling medium. 
         FIG. 5   a  is a top perspective view of an insert retainer having at least one vented channel. 
         FIG. 5   b  is a perspective close-up view of an insert retainer having a vented channel. 
         FIG. 6   a  is a perspective view of an insert retainer including inserts engaged by a 45 degree rotational indexer. 
         FIG. 6   b  is a plan view of a 90 degree rotational indexer. 
         FIG. 6   c  is a perspective view of an insert retainer including inserts engaged by a 90 degree rotational indexer. 
         FIG. 6   d  is a plan view of a 90 degree rotational indexer. 
         FIG. 7  is a perspective view of an insert retainer and a mold base including a preloaded protrusion. 
         FIG. 8  is a perspective view of an insert retainer including at least one preloaded key. 
         FIG. 9   a  is a perspective view of an insert retainer including a threaded aperture. 
         FIG. 9   b  is a side view of a mounting screw. 
         FIG. 10  is a side schematic of a cylinder lock and male knob. 
         FIG. 11   a  is a side schematic of handle including a button actuation system. 
         FIG. 11   b  is a perspective view of an opaque retainer holder and cover including a handle. 
         FIG. 11   c  is a side perspective transparent view of a cover and a retainer holder including a threaded protrusion and a threaded cap. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a first mold half  10  can have a base  6  including at least one insert retainer  2  having at least one insert  4 . The first mold half  10  can be a moveable mold half having at least one cooling channel.  FIG. 1  shows a first mold half having two insert retainers  2  of a rectangular shape each having eight insert apertures and eight associated convex inserts  4 . However, the present invention is not limited to any number of insert retainers, any shape of the insert retainers, or any number of inserts. The insert retainers  2  shown in  FIG. 1  are attached by mounting screws  8  but brackets, braces, quick clamps, bolts, rods, and magnets are also contemplated as means for attaching an insert retainer  2  to a mold half  6 . A coupling system utilizing mechanical, pneumatic, spring, or hydraulic forces is also contemplated as a means for attaching an insert retainer  2  to a mold half  6 , as discussed further below. 
     Referring to  FIG. 2 , a second mold half  12  having a base  6  can include at least one insert retainer  2  having at least one insert  5 . The second mold half  12  can be a fixed mold half  12  having at least one cooling channel.  FIG. 2  shows a second mold half having two insert retainers  2  of a contoured shape each having eight insert apertures and eight associated concave inserts  5 . The second mold half  12  can include a base  6  which can include a hot runner configured to deliver material, such as molten thermoplastic material for example, for forming ophthalmic devices, such as lens curves for example, to the inserts  5 . 
     Referring to  FIG. 3   a , one embodiment of an insert retainer  2  is shown having eight convex inserts  4 , each attached to a respective insert aperture. An insert retainer  2  can also have a retainer hole  19  as shown in  FIG. 3   a  and as discussed in more detail below. An insert retainer  2  can also have a thickness T 1  and at least one mounting screw  8  as discussed further below. In order to achieve increased efficiency of heat transfer from a base, which can have a cooling medium (not shown), to an insert  4 , the insert retainer  2  thickness T 1  can be minimized. Referring to  FIG. 3   b , in order to reduce thickness T 1 , thickness T 2 , which represents the distance measured from the manufacturing hole to the optical surface  7 , can be reduced such that structural integrity of the insert  4  is maintained during the injection molding process. Reducing the two thicknesses T 1  and T 2  can have the effect of increasing the heat transfer from the cooling medium to the insert  4  due to the increased proximity of the two components. Accordingly, since an optimum molding temperature range is required to produce effective lens curves, increased heat transfer to the inserts  4  can result in reduced down-time and increased cycle time. Preferably, insert retainer  2  thickness T 1  can be not greater than 15 millimeters, and more preferably, in the case of an insert retainer  2  having convex inserts  4 , the insert retainer  2  thickness T 1  can be not greater than 10 millimeters. 
     Referring to  FIG. 4 , an insert retainer  2  is shown including a retainer cooling medium  14  disposed in a substantially central location as compared to the four insert apertures  15 , each insert aperture  15  being configured to receive an insert. The retainer cooling medium  14  can include a conductive alloy such as copper, copper chromium, copper zinc, brass, and nickel-coated brass, for example. Preferably, the mold base  6  includes a base cooling medium (not shown) comprised of the same material as the retainer cooling medium  14  and located such that when an insert retainer  2  is received by a mold half  10 ,  12  the base cooling medium and the retainer cooling medium  14  can be configured to be substantially contiguous. Although the insert retainer  2  shown in  FIG. 4  includes only four insert apertures  15 , eight or any number of insert apertures  15  can be disposed in an insert retainer  2 . Should an insert retainer  2  include more than one set of four insert apertures  15 , each set can include a retainer cooling medium  14  disposed in a substantially central location as compared to the four insert apertures  15  that comprise each set. Retainer cooling  14  and base cooling mediums allow for increased heat extraction from the insert retainer  2  and inserts  4 ,  5  which allows for increased cycle time as well as increased ophthalmic device quality. Further, high conductive alloy material can be provided in other non-structural and/or non-functional areas of the insert retainer  2  to further increase heat extraction and insert  4 ,  5  cooling. 
     Referring to  FIG. 5   a , an insert retainer  2  is shown including eight insert apertures  15 . Preferably, the insert retainer  2  can have at least one vent channel  40  disposed between a front surface  39  and a back surface of the insert retainer  2 . Vent channels  40  can be configured to allow for gases, resulting from the injection molding process, to release thereby reducing the pressure exerted on the insert  4 ,  5  and the insert retainer  2 . Preferably, the vent channel  40  can be not greater than five millimeters in the direction perpendicular to the plane parallel to the front surface  39  of the insert retainer  2 . Apart from, or in combination with, a vent channel  40 , a recessed area  41  can be disposed in the insert aperture  15 , as shown more clearly in  FIG. 5   b , further allowing for increased effectiveness of gas venting. 
     Referring to  FIG. 6 , various configurations of a rotational indexer  28  are shown. A rotational indexer  28  can be configured to lockably engage at least one insert  4 ,  5  at a specific angle, as compared to the main axis of the insert retainer  35 , such that the insert  4 ,  5  remains in place. Maintaining insert  4 ,  5  position is of particular importance when an insert retainer  2  is moved such as when using a handle  18 , as discussed further below. Maintaining the integrity of the insert  4 ,  5  position is also useful for the manufacture of toric lenses which have a plurality of curvature angles and also maintain their orientation when worn and therefore require specific angle positioning. A rotational indexer  28  can be disposed adjacent the back surface  37  of the insert retainer  2  and preferably can be disposed in a recessed area such that no portion of the rotational indexer extends beyond the back surface  37  of the insert retainer. A rotational indexer  28  can be attached to an insert retainer  2  by magnets, adhesive, and/or screws, for example. 
     More specifically,  FIG. 6   a  shows two rotational indexers  28  attached to an insert retainer  2  having eight inserts  4 ,  5 . Preferably, each rotational indexer  28  can engage at least four inserts  4 ,  5 . Rotational indexers  28  can be configured to lockably engage at least one insert  4 ,  5  at any angle but preferably can be configured to lockably engage at least one insert  4 ,  5  at 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees as compared to the main axis of an insert retainer  35 . For example,  FIG. 6   a  shows two sets of four inserts  4 ,  5 , each lockably engaged at a 45 degree angle, as compared to the main axis  35  of the insert retainer  2 , by a respective rotational indexer  28 .  FIGS. 6   b - d  show rotational indexers  28  that are configured to lockably engage inserts  4 ,  5  at a 90 degree angle as compared to the main axis of the insert retainer  35 .  FIG. 6   b  shows a rotational indexer  28  that is configured to lockably engaged four inserts  4 ,  5  while  FIG. 6   c - d  show a rotational indexer  28  that is configured to lockably engage two inserts  4 ,  5 . Although the rotational indexer  28  can be any size, to reduce landscape size and maintain increased exposure of a retainer cooling medium  14 , the rotational indexer  28  preferably can be disposed so as not to cover or impede the area included in a retainer cooling medium  14 . 
     As discussed above, an insert retainer  2  may be attached to a mold half using a number of attachment means including mounting screws  8 , brackets, braces, quick clamps, bolts, rods, magnets, and pneumatic coupling systems, for example. Depending on the means for attachment, both of the operator&#39;s hands may be required to properly attach the insert retainer  2  to the mold base  6  such as is the case when mounting screws  8  are utilized, for example. In  FIG. 7 , one embodiment of an insert retainer  2  and mold base  6  is shown having at least one preloaded protrusion  38  extending from the mold base  6 . Preferably, at least one preloaded protrusion  38  can be disposed on two opposing sides of the mold base  6 . Each preloaded protrusion  38  can be configured to extend and retract such as by a spring mechanism, for example. For each of the preloaded protrusions  38 , a corresponding concave portion can be disposed in the insert retainer. In use, an operator can place an insert retainer  2  into a mold half  6  thereby displacing each of the preloaded protrusions  38  toward the mold base  6  until the preloaded protrusions  38  are aligned with the concave portions disposed in the insert retainer  2 . Alignment with the insert retainer concavities can cause a spring to expand causing the preloaded protrusions  38  to extend into the insert retainer concavities thereby clipping the insert retainer  2  in place and freeing the operator&#39;s hands which can then be used to insert mounting screws  8  or to accomplish any other means for attachment. Additionally, upon removal of the insert retainer  2  from the mold base  6 , the insert retainer  2  can remain clipped to the mold base  6  while the operator removes the mounting screws  8 , for example, and until a force is applied to the insert retainer  2  sufficient to compress the spring and displace the preloaded protrusions  38 . 
     In another embodiment shown in  FIG. 8 , preloaded keys  42  can be attached to a mold base  6  to allow for increased precision in insert retainer  2  placement upon attachment to a mold base  6 . Preferably, at least one preloaded key  42  can be disposed on two opposing sides of the mold base  6 . Also preferably, each preloaded key  42  can include at least one angled edge such that insertion of the insert retainer  2  into the mold base  6  can cause the insert retainer  2  to engage the angled edge thereby providing for increased centering of the insert retainer  2  in the mold base  6 . Preferably the angle is a high draft angle such as a 15 degree angle, for example. Increased centering of the insert retainer  2  in the mold base  6  can result in significantly increased alignment of the concave  5  and convex  4  inserts during the molding process thereby resulting in higher quality ophthalmic devices. 
     As discussed above, an insert retainer  2  can be attached to a mold half  6  by mounting screws  8  such that each mounting screw  8  can be configured to engage a threaded aperture  30  disposed in the insert retainer  2  as shown in  FIG. 9   a . In order to reduce mounting screw  8  loss and increase insert retainer  2  changeover time, the mounting screws  8  can be configured to have a first end  34  and a second end  36  such that at least a portion of the first end  34  can be of a smaller diameter D 1  than the diameter D 2  of at least a portion of the second end  36  and the second end  36  can be threaded as shown in  FIG. 9   b . Upon insertion of a mounting screw  8 , the second end  36  can rotatably engage the threaded aperture  30  of the insert retainer  2 . Upon engagement with the threaded aperture  30  by the portion of the first end  34  having a smaller diameter D 1  than the diameter D 2  of the second end, the mounting screw  8  can slide into the threaded aperture  30  such that removal will require rotating the second end  36  back through the threaded aperture  30 . Accordingly, the mounting screws  8  can be configured to attach to an insert retainer  2  such that only rotating back through the threaded aperture  30  of the insert retainer  2  will remove the mounting screws  8  from an insert retainer  2  thereby resulting in reduced mounting screw  8  loss. 
     In another embodiment, a quick clamp method can be used to attach and remove an insert retainer  2  to a mold base  6 .  FIG. 10  shows a mold base  6  having a cylinder lock  44  disposed toward a surface adjacent to an insert retainer  2  upon attachment of the insert retainer  2  to the mold base  6 . The cylinder lock  44  can be configured to receive a male knob  46  protruding from an insert retainer  2 . The male knob  46  can be a conical shape, for example, and can be attached by a screw  50  disposed in the insert retainer  2  and extending into a threaded aperture disposed in the male knob  46 . Alternatively, the male knob  46  can be attached to the insert retainer  2  by magnet or adhesive, for example. The cylinder lock  44  can include at least one spring (not shown) configured to engage at least one wedge (not shown) upon application of pneumatic pressure. Pneumatic pressure can be delivered through channels in the mold base  6  and the pressure can be applied by an operator engaging a button, for example. Upon insertion of the insert retainer  2  into the mold base  6  and application of pneumatic pressure, a spring can be configured to expand and displace a wedge which can be configured to engage at least one sphere  48  such that the sphere  48  is displaced toward the male knob  46  locking the male knob  46  in place in the cylinder lock  44 . Preferably, the cylinder lock  44  includes a plurality of spheres  48  as shown in  FIG. 10 . Upon removal of the insert retainer  2  from the mold base  6 , pneumatic pressure can be applied such that a spring can be compressed and a wedge can be displaced causing each of the spheres  48  to displace away from the male knob  46  and allowing the male knob  46  to move relative to the cylinder lock  44 . While the male knob  46  is locked in place in the cylinder lock  44 , the cylinder lock  44  can be configured to stay mechanically locked until pneumatic pressure is once again applied. Accordingly, even if pneumatic pressure is lost, the male knob  46  and insert retainer  2  can stay locked to the cylinder lock  44  and mold base  6 . 
     In order to provide for efficient insertion and removal of insert retainers  2  as well as to maintain the integrity of optical inserts  4 ,  5 , a handle  18  can be used in the absence of, or in combination with, a cover  16  as shown in  FIG. 11 . A cover  16  can have a cover hole  17  configured to align with a retainer hole  19  (see  FIG. 3   a ). In a preferred embodiment, an ergonomic handle  18  can be attached to a cover such as by a threaded portion and associated threaded cover hole  17  or displaceable protrusions and associated cover hole concavities, for example, such that a portion of the handle  18  can extend beyond the cover hole  17 . A button  20  and associated button actuation system can be disposed on the handle  18  such that operator engagement with the button  20  can cause at least one displaceable protrusion  26  to either extend or retract into or out of at least one concavity disposed adjacent the retainer hole thereby attaching the handle  18  to the insert retainer  2  as shown in  FIG. 11   a . To insert an insert retainer  2  into a mold base  6 , an operator can place the handle  18  into the retainer hole  19  and engage the button  20 , for example, and manipulate the insert retainer  2  using the handle  18 . The operator can then manipulate the insert retainer  2  into the mold base  6  by once again engaging the button  20  to release the handle  18  and associated cover  16 . To remove an insert retainer  2  from a mold base  6 , an operator can place a handle  18 , and attached cover  16 , into the insert retainer  2  and engage the button  20 , for example, to manipulate the insert retainer  2  away from the mold base  6 . The insert retainer  2  can then be removed from the mold base  6  and manipulated using one hand by carrying the handle  18  while advantageously maintaining the integrity of the optical surface of the inserts  4 ,  5 . 
     In a preferred embodiment, a handle  18  can be both removed from and attached to a cover  16 , as discussed above.  FIG. 11   b  shows one embodiment of an insert retainer storage arrangement having a handle  18  attached to a cover  16 . Removing the handle  18  can allow for a more efficient storage solution as shown in  FIG. 11   c .  FIGS. 11   b - c  also show a retainer holder  24  disposed below the insert retainer  2  and attached to the cover  16 . Preferably, the retainer holder  24  can be configured to receive an insert retainer  2  such that each side of the retainer holder  24  is minimally larger than a corresponding side of the insert retainer  2 . In one embodiment, the cover  16  can contain at least one bore  22  and the retainer holder  24  can have at least one threaded receiver such that the cover  16  can be attached to the retainer holder  24  using threaded screws as shown in  FIG. 11   b . In another embodiment shown in  FIG. 11   c , the retainer holder  24  can have a threaded protrusion  29  configured to extend through both the retainer hole  19  (see  FIG. 3   a ) and the cover hole  17 . A threaded cap  27  can then be rotated onto the threaded protrusion  29  thereby maintaining the cover  16  between the threaded cap  27  and the retainer holder  24 . Accordingly, the retainer holder  24  and cover  16  can protect both sides of the optical inserts  4 ,  5  such that the insert retainers  2  can be stacked and stored providing for an advantageously efficient storage arrangement. 
     While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. 
     Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.