Abstract:
Apparatus for clamping together contact lens molds having a polymerizable liquid monomer disposed therebetween includes a plurality of clamping assemblies each having a linearly translatable shaft member mounted to a contact lens curing table. A common mold clamp release assembly is provided through which each mold clamping assembly passes, thereby ensuring that each mold set is subjected to the same clamping and release profile. Additionally, the amount of clamping force of each clamping assembly may be individually adjusted by way of an adjustable nut mounted to the shaft member which, thereby, controls the amount of force delivered by the shaft member to the contact lens molds being clamped.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an apparatus and method for clamping together and releasing contact lens mold halves for manufacture of contact lenses, and more particularly to an apparatus and method for clamping multiple contact lens mold halves together by way of a single activating source while still providing means to individually adjust the clamping force being supplied to each pair of contact lens mold halves. 
     It is desirable to directly mold contact lenses rather than form the lenses by machining operations such as lathing. Generally, depositing a predetermined amount of curable substance, such as a polymerizable liquid monomer into a preformed mold cavity forms molded lenses. Thereafter, the liquid monomer is subjected to a curing source such as UV light or heat for a predetermined period of time until the monomer is properly cured. A soft contact lens results when the cured monomer form is separated from the molds and hydrated. 
     Generally, in the process briefly described above, a large number of contact lens molds are filled with the polymerizable liquid monomer at a station remote from the actual curing apparatus. Herein, the polymerizable liquid monomer is first injected into one (female) half of the mold assembly and then the second (male) half of the assembly is brought into contact with the first half. The opposing surfaces of the mold halves define the optical surface of a contact lens therebetween. The mold halves are lightly clamped together to allow transport from the monomer inject station to the clamping and curing station. 
     Once the contact lens molds are introduced to the clamping and curing station, it is recognized that problems may occur during the clamping and release procedure generally used in the past. For example, it is recognized that defects may appear in some lenses due to variations caused by providing individual clamping and release mechanisms associated with a respective mold. In previously known systems, the contact lens molds are arranged together in, for example, groups of three. Thereafter, the grouped lens molds are clamped together by individual clamping sources acting on each lens mold. In other words, a separate clamping and release source is provided for each contact lens mold being presented to the curing station. For example, three air cylinders would clamp three molds in a group, respectively, with the three air cylinders being extended and retracted by a common air line. With each group of molds having its own air line, variations were inevitably seen between each air line, and in both the extension and retraction velocities of the cylinders. In this case, each mold or groups of molds may see different clamping and release velocity profiles. 
     The present invention recognizes the problems that occur in contact lenses molded from a polymerizable material, which are not subjected to uniformly even clamping and release velocity profiles which are being applied to the lens mold halves. Problem areas are seen in improper edge formation, as well as defects in the optical portion of the lenses. 
     U.S. Pat. No. 5,914,074 to Martin et al entitled “Mold Clamping and Curing of a Polymerizable Hydrogel” discloses a clamping device for clamping together contact lens mold halves which have a polymerizable material, such as hydrogel, therebetween. The mold halves are clamped together with a predetermined force provided by way of an air cylinder, springs or weights for a predetermined period of time. The mold halves are formed of a material suitable to allow the polymerizable hydrogel material to be exposed to a curing source, such as UV light, to thereby cure the material to a gel-like state. Thereafter, the clamping pressure is removed and the mold halves having the partially cured hydrogel material disposed therebetween is moved to a further station for finish curing. 
     In addition to the above reference, U.S. Pat. Nos. 3,806,079; 4,284,399; 5,690,473; 5,693,268 and 5,850,107 disclose a liquid monomer clamped in a contact lens mold and polymerized to form a contact lens. 
     None of the above art solves the problems which occur when using the previously known contact lens clamping methods. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward an apparatus for accurately and repeatably clamping together multiple pairs of contact lens mold halves having a polymerizable liquid material contained between each pair. The clamped together contact lens mold halves are thereafter presented to an appropriate source for curing the polymerizable material to form contact lenses. 
     In this invention, a contact lens mold clamping assembly is presented which with accuracy and repeatability, clamps together and then releases multiple pairs of contact lens mold halves by utilizing a common source for activating the plurality of clamping mechanisms. 
     The contact lens mold clamping assembly may include a biasing mechanism coupled to each of the plurality of contact lens molds to enable the force being exerted thereon by the clamping assembly to be individually and accurately determined and set. 
     Further, this invention provides a contact lens mold clamping assembly and a common release mechanism for interaction with the clamping assembly to open the clamping assembly for introduction thereto of assembled contact lens molds, and thereafter releasing the clamps enabling the contact lens molds to be clamped by the clamping assembly. Because each clamp passes through the same, common release mechanism, each clamp sees the same, controlled linear motion profile. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a mechanism for clamping together a plurality of contact lens mold halves, according to an embodiment of the invention; 
     FIG. 2 is a front view, in partial cross-section, of the clamping mechanism of FIG. 1; 
     FIG. 3 is a perspective view of a release mechanism for coupling together with the clamping mechanism of FIGS. 1 and 2 to thereby release the clamping pressure applied to the contact lens mold halves; 
     FIG. 4 is a front view, in partial cross-section, of the release mechanism of FIG. 3; 
     FIG. 5 is a view showing the clamping mechanism and release mechanism mounted to a carousel table and in engagement with each other; and 
     FIG. 6 is a schematic diagram of a carousel table used in clamping together contact lens molds and curing contact lenses contained therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is useful in the process of clamping together male and female molds in the process of forming soft contact lenses from a polymerizable material. As best illustrated in FIGS. 1,  2  and  5 , a clamping assembly  10  is constructed so as to clamp together and hold assembled contact lens mold halves. Clamping assembly  10  may include sufficient space for positioning thereon four assembled lens molds  12 , although depending upon preferences, either more or less mold capacity may be chosen. 
     The clamping assembly  10  includes a plurality of spring loaded clamping members  14 , each of which include a shaft  16 , a central threaded portion  17 , a hexagonal portion  18  formed at one end  20 , and a threaded portion  22  formed at the end opposite end  20 . A bushing  24  having a stepped portion  26  is received on central portion  17 . An adjusting clamp  28  is mounted to threaded portion  17  of shaft  16  above stepped portion  26  of bushing  24 . Adjusting clamp  28  includes a threaded split nut  30  and clamp screw  32  so as to enable split nut  30  to be adjustably positioned on, and locked to, threaded central portion  17 . A coil spring  34  is mounted between the stepped portion  26  of bushing  24  and split nut  30 . Further, each shaft  16  includes a bearing  36  and a retaining ring  38  mounted adjacent hexagonal portion  18  thereof. As best seen in FIGS. 2 and 4, a preselected number of the spring loaded clamping members  14  are mounted between lower mount  40  and upper mount  42  of clamping assembly  10  by a plurality of threaded spacer bolts  44 . Still further, a locator block  46  is mounted to upper mount  42  and is also secured by spacer bolts  44 . Shaft  16  may be journalled to lower mount  40  by way of annular bearing  48 , as best shown in FIG.  2 . 
     A bushing  50  is secured to threaded portion  22  of shaft  16  by way of internally threaded nut  52 . Bushing  50  is dimensioned so as to be slidably received for reciprocal motion within aperture  54  formed within blocks  46 , 47 . Further, as is seen in FIGS. 1 and 2, a clamping plate  56  is secured to locator block  46  a predetermined distance thereabove by parallel guide plates  49 , 51 . 
     Referring now to FIGS. 3 and 4, a clamp release mechanism  100  includes an actuator mechanism  102  (which may be an air cylinder, servo drive, stepper motor, or any other suitable source). Actuator  102  is coupled to a plurality of paired release fingers  104 . The number of paired release fingers  104  equals the number of grouped contact lens molds  12  which are presented in the clamping assembly  10  as described hereinabove. Therefore, in this description the number of paired release fingers  104  in clamp release mechanism  100  is four, although more or less may be considered as pointed out above. The paired release fingers  104  are compliantly mounted by coil springs  108  and threaded shafts  110  to a block  112  which, in turn, is mounted to actuator mechanism  102  by way of spacers  114 . A pair of guide plates  116  are longitudinally mounted to block  112 , as best seen in FIG.  3 . Actuator mechanism  102  includes a mounting plate  118 . 
     In operation, a clamping assembly  10  is prepared for use in a contact lens curing station, such as a carousel table schematically shown in FIG. 6 which is well known in the art. To initially calibrate clamping assembly  10 , each clamping assembly  10  would be set up in a test fixture (not shown) and subjected to a test procedure to determine if each of the individual clamping members  14  is applying a specific predetermined clamping force to the contact lens mold assemblies being clamped together. Each nut  30  may be individually adjusted until the desired clamping force is achieved. Accordingly, if, after taking the test reading there is a discrepancy in any one (or all) of the readings, it is a simple matter to adjust any one (or all) of the clamping assemblies  10  to achieve the desired results. This is done by simply loosening clamp screw  32  on split nut  30 . Thereafter, an appropriate tool may be affixed to hexagonal end portion  18  of shaft  16  so that the shaft may be rotated. Depending upon the direction of rotation, split nut  30  moves either up or down the threaded portion  17  of shaft  16 , as it can be seen that each individual split nut  30  bears against an adjacent split nut and, therefore, cannot rotate. Readings are taken in the test fixture as the adjustments are being made until the proper and desired reading is achieved. For example, as split nut  30  is moved upward on shaft  16 , the force exerted by spring  34  against the test mold assembly is reduced whereas moving split nut  30  downward increases force, At this time, the clamp screw  32  is tightened and split nut  30  is locked to threaded portion  17  of shaft  16 . Therefore, it will be appreciated that by so adjusting each clamping assembly  10 , an integrated clamping assembly is provided which provides the exact clamping force to each contact lens mold assembly  12 . After completing the procedures described above, each tested and calibrated clamp assembly  10  is mounted in a contact lens curing apparatus, such as the previously referenced carousel which is shown schematically in FIG.  6 . 
     In actual production, the mold assemblies  12  may be introduced to the clamping assembly  10  along arrow  43  seen in FIG.  1 . Prior to introducing the mold assemblies, a downward force is applied to each bearing  36  such that bushing  50  attached to shaft  16  is retracted to the flush position shown by arrow “A” in FIG.  2 . In this position, the upper surface  50 ′ of bushing  50  lies substantially flush with the upper surface  47 ′ of plate  47 . At this position, the lower surface  50 ″ of bushing  50  abuts and stops against the upper surface  42 ′ of plate  42 . With referencing fixtures  50  retracted, the mold assemblies  12  may be pushed onto their respective bushing  50 . The retractive force on bearings  36  is then released which, by way of the force exerted by coil spring  34  between bushing  24  and split nut  30 , pushes the bushing  50  upwardly until the associated mold assembly is forced against clamping plate  56 . Briefly, a carousel curing apparatus is a large, discshaped table  200  which is rotatably mounted to a central shaft  202 . A significant number of contact lens mold clamping assembles  10  are mounted in annularly spaced relation to table  200  through complimentary shaped openings  210  formed adjacent the periphery of table  200 . As table  200  is incrementally rotated about shaft  202 , the clamp assemblies  10  are each individually opened (i.e., they are retracted to the “A” position of FIG. 2 in the manner described below), and a number (e.g., four at a time) of the contact lens molds  12 , which have been previously filled with a liquid monomer and preliminarily capped, are shuttled along arrow  43  of FIG. 1 into respective clamp assemblies  10  on table  200 . As table  200  continues to rotate, the clamping assemblies  10  are released whereby each lens mold  12  is clamped against associated plate  56  with the appropriate, calibrated force. Table  200  is equipped with an appropriate curing source such as UV lights such that the clamped molds  12  are subjected to UV radiation through table openings  210  and plate openings  56 ′ as table  200  rotates the clamped assemblies toward a post-cure station  300 . Once they reach station  300 , the mold clamping assemblies  10  are retracted to the “A” position, and the mold assemblies  10  are shuttled off table  200  to a post-cure or other appropriate station  300 , as indicated by arrow “C” in FIG.  6 . 
     In a preferred embodiment of the present invention, a plurality of clamp assemblies  10  are mounted to an appropriate apparatus, such as the carousel table  200  described above and schematically illustrated in FIG.  6 . Further, one or more clamp release mechanism  100  (FIGS. 3-5) are mounted, by way of an associated mounting plate  118 , such that it is disposed directly below table  200  and clamp assemblies  10 . Thus, while clamp assemblies  10  are fixed to and rotate with table  200 , the clamp release mechanism  100  are fixed by mount  118  and do not rotate with table  200  or clamp assemblies  10 . 
     More particularly, in the embodiment of FIG. 6 a clamp release mechanism  100  is positioned at mold load location “D” where the mold assemblies  12  are first shuttled onto table  200  in associated clamping assemblies  10 . Further, a second clamp release mechanism  100  is positioned at mold exit location “C”, where the mold assemblies, having been rotated by table  200  to location “C” from location “D”, are shuttled off table  200  to a subsequent processing station  300 . 
     Thus, clamp release mechanisms  100  are required at two distinct process steps: (1) at initial clamping of mold assemblies  12 , and (2) at transfer of mold assemblies  12  from table  200  to subsequent processing station(s). 
     Referring to FIG. 5, each clamp release mechanism  100  includes one or more engaging members  103  having bifurcated fingers  104 . In the embodiment shown, a group of four engaging members  103  are provided in a single clamp release mechanism  100  which equal in number the set of mold clamping members  14  on each assembly  10 . The bifurcated fingers  104  are shaped, and the engaging members  103  are spaced, so that as table  200  incrementally rotates, the next clamping assembly  10  comes into alignment with the clamp release mechanism  100  with bearings  36  being received between the bifurcated fingers  104  of an associated engaging member  103  as seen best in FIG.  5 . Once so positioned, actuator mechanism  102  is energized which retracts engaging members  103 , and thus also fingers  104  downwardly, thereby pulling bearings  36  and clamping member  14  downwardly also to position “A”, as shown in FIGS. 2 and 5. As previously stated, downward movement of clamping members  14  is limited by bushing lower surface  50 ″ engaging plate upper surface  42 ′. In order to accommodate tolerance buildup between the meeting point of the bushing  50  and plate  42 , and the meeting point of the upper surface of bearing  36  and the lower surface of the respective fingers  104 , coil spring(s)  108  mounted to threaded shafts  110  will compress. 
     More particularly, actuator  102  is designed to pull the bifurcated fingers  104  to the retracted position (shown at “A” in FIG.  2 ). The bifurcated fingers  104  are guided in their up and down movement by way of parallel guide plates  116 . Each clamping member  14  is, consequently, pulled down to the “A” position, which is sufficient to allow a predetermined number of contact lens molds  12  (e.g., four) filled with a polymerizable liquid monomer to be-shuttled (along arrow  43  of FIG. 1) into place on a respective clamping assembly  10 . When each contact lens mold  12  is positioned on a respective bushing  50 , actuator mechanism  102  is deactivated which releases the bifurcated fingers  104  to their extended position. With the load applied by fingers  104  thus removed, springs  34  bias against nuts  30  thereby causing upward extension of clamping members  14  and clamping of mold sets  12  between upper plate  56  and associated bushing  50 . Again, each clamping member  14  has been previously calibrated so that springs  34  exert the correct force to mold sets  14 . 
     As table  200  is incrementally indexed, the clamping assembly  10  which has clamped mold sets  12  held therein as described above, proceeds to rotate with table  200  while clamp release mechanism  100  in which it was engaged remains stationary. As such, bearings  36  exit from between their respective bifurcated fingers  104 , travelling toward station  300  with table  200 . It will thus be appreciated that mold sets  12  are in the clamped “B” position as they travel between mold load location “D” and mold exit location “C” of table  200 . The elapsed time between stations “D” and “C” is predetermined and set according to known criteria for polymerizing the monomer contained within the mold sets  12 . 
     As stated above, a second release assembly is located at location “C” to permit the unclamping of mold sets  12  and transport thereof off table  200  and to station  300 . Again, the mounting of clamp release mechanism  100  is such that bifurcated fingers  104  are aligned to receive a respective bearing  36  of successively indexed clamp assemblies  10  of table  200 . Once the respective clamping assembly  10  has aligned with the clamp release mechanism  100  at location “C”, associated actuator  102  is energized, thereby retracting engaging members  103  and respective clamping members  14  which are thus moved downwardly to the “A” position. The previously clamped mold sets  12  are thus free to be shuttled off table  200  to station  300  for subsequent processing as desired. Once the mold sets  12  have been shuttled off table  200 , actuator  102  is released, thereby returning associated clamping members  14  to their extended “B” positions, absent the mold sets  12  which have been transported to station  300  as described above. The now “empty” clamping assembly  10  continues travel with table  200  back toward the mold loading station “D” as seen in FIG.  6 . The cycle is then repeated, with each empty clamping assembly  10  being successively indexed to mold loading station “D” where assembly  10  comes into alignment with the clamp release mechanism  100  positioned at station “D”. 
     It will thus be appreciated that each group of mold sets  10  passes through the same release assemblies, one at mold load location “D”, and the other at mold exit location “C”. As such, each incrementally indexed mold set  10  on table  200  is subjected to the same clamping and release profile. This is a vast improvement over the prior art in that the variability seen between different mold sets of the prior art method have been eliminated. Furthermore, tolerance buildup variability between the different clamping assemblies has been substantially eliminated through the compliant mounting of the clamping release members. 
     Lastly, it will be recognized from the preceding description regarding the testing and calibration procedure performed on each clamping assembly  10  and each clamping member  14 , that the clamping force exerted on each contact lens mold  12  may be precisely controlled and equalized across all mold sets  12 . Accordingly, previously accepted, yet undesirable variables in producing molded contact lenses has been eliminated. 
     While the invention has been shown and described with respect to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be accomplished without departing from either the spirit or scope of the invention which should be limited only by the scope of the claims appended hereto.