Abstract:
An apparatus for eliminating the differences in the curvatures of a facing lens blank and an abrasive pad mounted on a formable lap includes a drivable track portion, a compensation plate disposed on the drivable track portion, and a compensation member removably disposed on the compensation plate. The compensation member is removable from the compensation plate by a carriage supporting the lens blank and is disposable between the lens blank and the formable lap. The method for compensating for the differences in curvatures of the formable lap and the lens blank includes inserting the compensation material onto the formable lap, softening the formable lap, placing the lens blank over the compensation material to cause the formable lap to conform to a shape of the lens blank, allowing the formable lap to cure, removing the lens blank, and removing the compensation material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of an earlier filing date from U.S. Provisional Application Serial No. 60/244,702 filed Oct. 31, 2000, the entire disclosure of which is incorporated herein by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This disclosure relates to the manufacture of a lens, and, more particularly, to an apparatus and method for substantially eliminating differences in the curvatures of the facing surfaces of a lens blank and an abrasive pad mounted on a formable lap employed in a lens finishing operation.  
         BACKGROUND  
         [0003]    The manufacture of a lens involves the generation of a lens blank and the fining and polishing of the lens blank with an abrasive pad mounted to a lap. The fining and polishing of the lens blank is effectuated by the positioning and manipulation of an abrasive pad disposed on the lap and between the surfaces of the lens blank and the lap to alter the shape of the material of the lens blank, thereby producing a lens of the desired optical properties. The thickness of the abrasive member may be substantial relative to the amount of material that is removed from the lens blank to arrive at the finished lens. This thickness is accounted for by shaping the surfaces of the lens blank and the lap so that the surfaces of the lens blank and the lap are not complementary. To accurately fine and polish the lens blanks, apparatuses of the related art require a multitude of various laps in which each lap is of a curvature that is different than the curvature of the blank. Oftentimes, thousands of different laps need to be kept on hand in order to effectively produce a lens of the desired optical properties.  
           [0004]    With the advent of a lap that is formable to the curvature of different lens blanks, the number of various laps that need to be kept is significantly reduced; producing a lap that matches the curvature of the desired lens blank is achieved by softening the lap with heat, pressing the curved surface of the blank onto the softened lap, and allowing the deformed lap to cool, thereby hardening and matching the curvature of the blank. In using a blank and a lap generated by such a procedure, the introduction of the abrasive member between the blank and the lap causes the curvature of the combination of the lap and the abrasive pad to be different from the lens blank, which can result in the optical properties of the finished lens being slightly irregular relative to that which is desired.  
         SUMMARY  
         [0005]    A device and method for eliminating the differences in the curvatures of a facing lens blank and an abrasive pad mounted on a formable lap during a lens finishing operation is disclosed herein. The device inserts a piece of material that corresponds to the thickness of a fining and polishing pad between the lens blank and the lap before the lap is deformed to enable the curvature of the deformed lap and abrasive pad to be complementary to the proper curvature of the lens blank during the finishing operation. Once the lap is deformed such that the desired curvature is obtained, the compensation material is removed, and the lap receives the proper fining and polishing pad, thereby allowing the lens blank to be more accurately finished. The device includes a drivable track portion, a compensation plate disposed on the drivable track portion, and a compensation member removably disposed on the compensation plate. The compensation member is removable from the compensation plate by a carriage before being disposed between the lens blank and the lap.  
           [0006]    In a first embodiment, the compensation member comprises a piece of material having a plurality of rings disposed at the edges thereof. The rings are engagable by a corresponding number of members disposed on the compensation plate to retain the compensation member on the compensation plate. The carriage includes a plurality of pickups depending therefrom, each being configured and positioned to receive each of the rings in successive motions articulated by the carriage.  
           [0007]    In a second embodiment, the compensation member comprises an inner ring, a piece of material draped over the inner ring such that edges of the material extend at least over the edges of the inner ring, and an outer ring disposed over the edges of the material and around the inner ring to frictionally retain the piece of material between the inner ring and the outer ring. The outer ring includes at least one magnet disposed thereon, and the carriage includes a corresponding number of magnets positioned to correspond with the magnets of the outer ring. Engagement of the magnets on the outer ring with the magnets on the carriage effectuates the transfer of the compensation member to the carriage.  
           [0008]    The method includes inserting the compensation material onto the formable lap, softening the formable lap, placing the lens blank over the compensation material to cause the formable lap to conform to a shape of the lens blank, allowing the formable lap to cure, removing the lens blank, and removing the compensation material.  
           [0009]    The above-mentioned device and method promote the efficient manufacture of lenses of varying prescriptions without the need for maintaining a large inventory of laps of varying curvatures. Furthermore, by compensating for the differences between a lens blank and its corresponding lap that are introduced by the abrasive member, the accuracy of each lens produced is greatly increased. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of a compensation device of a lens finishing apparatus.  
         [0011]    [0011]FIG. 2 is a perspective view of a lens finishing apparatus.  
         [0012]    [0012]FIG. 3 is a perspective view of a first embodiment of a compensation plate of a compensation device.  
         [0013]    [0013]FIG. 4 is a perspective view of a spool member.  
         [0014]    [0014]FIG. 5 is a perspective view of a compensation member having rings attached thereto.  
         [0015]    [0015]FIG. 6 is a perspective view of a spool pickup.  
         [0016]    [0016]FIG. 7A is an exploded perspective view of a second embodiment of a compensation member.  
         [0017]    [0017]FIG. 7B is an exploded perspective view of an outer ring of the compensation member of the second embodiment and a compensation plate.  
         [0018]    [0018]FIG. 8 is a plan view of a carriage of a lens finishing apparatus.  
         [0019]    [0019]FIG. 9 is a perspective view of a compensation device incorporating the second embodiment of the compensation member. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Referring to FIG. 1, one embodiment of a compensation device for use with a lens finishing apparatus (shown below with reference to FIG. 2) is shown generally at  10 . Compensation device  10  comprises a compensation plate, shown generally at  12 , attached to a track portion, shown generally at  14 , a drive motor  16  that drives track portion  14 , and a compensation member, shown generally at  18 , removably connected to compensation plate  12 . Compensation device  10  inserts compensation member  18  between a lens blank and a formable lap  20  of the lens finishing apparatus. Compensation member  18  is dimensioned to compensate for the distance between the lens blank and lap  20  by being dimensioned so as to correspond to the thickness of an abrasive pad (not shown) used to fine and polish the lens blank. Once compensation member  18  is inserted between the lens blank and lap  20 , compensation member  18  is removed from compensation plate  12  by a carriage (shown below with reference to FIG. 2) on the lens finishing apparatus. The carriage is then manipulated such that compensation member  18  is placed over lap  20 , lap  20  is deformed so as to cause the contact surface of lap  20  to correspond with the curvature of the lens blank when the later applied abrasive pad is positioned between the lens blank and lap  20 , and the deformed lap  20  is cured to produce a finished lap of a curvature that is, when combined with an abrasive pad, proper for the lens blank. Removal of compensation member  18  from lap  20  once the lap forming procedure is concluded comprises reversing the order of the foregoing operations.  
         [0021]    Referring now to FIG. 2, a lens finishing apparatus is shown generally at  22 . Lens finishing apparatus  22  is an apparatus for performing work operations on a surface of a lens. Such an apparatus is taught in issued U.S. Pat. No. 5,980,360, which is incorporated herein by reference in its entirety. Lens finishing apparatus  22  comprises a frame  26 , a plurality of struts  28  connected at the first ends thereof to frame  26 , and a carriage, shown generally at  24 , connected to the second ends of strut members  28 . Carriage  24  is configured and dimensioned to support the lens blank (not shown) and to receive the compensation member from the compensation device, which is positioned proximate lens finishing apparatus  22  such that when track portion  14  extends, the compensation plate positions the compensation member for pick up by carriage  24 . An operation wherein the compensation member is removed from the compensation plate and retained on carriage  24  for placement over lap  20  is described below.  
         [0022]    In FIG. 3, one embodiment of compensation plate  12  is shown in greater detail. Compensation plate  12  comprises a plurality of arms  30  radiating outward from a central portion  32 . Each arm  30  is positioned to be in the same plane as each other arm  30 . In a preferred embodiment, compensation plate  12  includes three arms  30 , although a compensation plate incorporating more than three arms may be used. Spool members  34  (described in detail below with reference to FIG. 4) are disposed in holes  36  on the end portions of each arm  30 . In one embodiment, a spacer  33  is disposed within central portion  32  and extends from the surface of compensation plate  12  to provide support for the compensation member disposed on compensation plate  12 . Support of the compensation member, which may be coated with a liquid lubricant, prevents the compensation member from adhering to the surface of compensation plate  12  when the compensation member is disposed thereon. Compensation plate  12  may be fabricated from a variety of different materials including, but not limited to, aluminum. The material need only have sufficient durability in the lens fining environment to be acceptable.  
         [0023]    Referring now to FIG. 4, the spool member, which is shown generally at  34 , comprises a cylindrically shaped body portion  38  and a pin  40  depending from one end thereof. Body portion  38  is generally of a smaller cross section at a point intermediate the ends thereof to accommodate rings (shown below with reference to FIG. 5) disposed at the edges of the compensation member and to retain the rings upon application of a force in directions lateral to the axis of the cylindrically shaped body portion  38 . Pin  40  is dimensioned and configured to be received in the hole in the end portion of the arm of the compensation plate.  
         [0024]    Referring to FIG. 5, compensation member  18  comprises a piece of material  42  and a plurality of rings  44  disposed on the edges of material  42 . Material  42  may be a piece of elastic material such as LYCRA (trademark), although other materials having the appropriate thickness and being capable of withstanding the heat associated with the process of forming the lap and the other environmental factors extant in the fining apparatus can be used. Rings  44  may be glued, sewn, or otherwise attached to the edges of material  42  in a configuration that corresponds with the arrangement of the arms of the compensation plate. Rings  44  are sized to accommodate the spool members and to allow for the transfer of rings  44  between the spool members of the compensation plate and the spool pickups of the carriage to effectuate the transfer of compensation member  18  from the compensation device to the lens finishing apparatus.  
         [0025]    Referring to FIG. 6, a spool pickup is shown generally at  46 . Spool pickup  46  is similar in configuration and dimension to the spool member of the compensation plate. In particular, spool pickup  46  comprises a cylindrically shaped body portion  48  having a smaller cross section intermediate the ends of body portion  48 . One end of body portion  48 , however, includes a hole  50  disposed therein that extends longitudinally for some length along body portion  48 . Hole  50  is configured and dimensioned to receive a pin (not shown) depending from the carriage, which provides a means for connecting spool pickup  46  to the carriage.  
         [0026]    Referring back to FIGS. 1 and 2, compensation plate  12  is mounted to track portion  14  of compensation device  10 . In a preferred embodiment, an operator (not shown) fits the rings of compensation member  18  over the spool members of compensation plate  12  such that compensation member  18  is stretched relatively tightly across compensation plate  12 . Drive motor  16  is then actuated and causes track portion  14  having compensation plate  12  attached thereto to extend into lens finishing apparatus  22  such that compression plate  12  is between carriage  24  and lap  20 . To transfer compensation member  18  from compensation plate  12  to carriage  24 , apparatus  22  is manipulated such that an edge of carriage  24  at which a spool pickup is positioned is “dipped” in the direction of a first ring of compensation member  18  such that the spool pickup on carriage  24  extends into the ring. Carriage  24  is then rotated in an outward direction relative to the central portion of compensation plate  12 , thereby causing the spool pickup to pull the ring away from the spool member on compensation plate  12 . Carriage  24  is further manipulated such that the edge of carriage  24  that was originally dipped is returned to its “pre-dipped” position, thereby causing the first ring to be retained on the spool pickup on carriage  24  while the second and third rings on compensation member  18  remain retained on the spool members on compensation plate  12 . In successive movements similar to that of the movement described above, the second and third rings are transferred to their respective spool pickups on carriage  24 , thereby causing compensation member  18  to be completely retained on carriage  24 . Upon completion of the transfer of compensation member  18  from compensation plate  12  to carriage  24 , compensation plate  12  is removed from lens finishing apparatus  22  by retracting track portion  14  therefrom.  
         [0027]    Another embodiment of the compensation member and the compensation plate on which it is mountable is shown in FIGS. 7A and 7B. In FIG. 7A, a compensation member, shown generally at  56 , comprises an inner ring  58  and an outer ring  60  which together are similar to what is commercially known as an embroidery hoop. Inner ring  58  is a continuous member having a substantially uniform cross section and being configured such that the edges of a piece of composition material (not shown) positioned over inner ring  58  can drape over the edges of inner ring  58 . Outer ring  60  includes an opening  62  formed therein and is fabricated of a material such that outer ring  60  is flexible. The flexibility of outer ring  60  enables outer ring  60  to be fitted around inner ring  58  when the compensation material is placed on inner ring  58 , thereby causing the compensation material to be retained between inner ring  58  and outer ring  60 . Upon fitting outer ring  60  around the compensation material and inner ring  58 , outer ring  60  can be tightened. The tightening of outer ring  60  may be effectuated by the insertion of a fastener  64  extending through a protrusion  66  on one end of outer ring  60  to a protrusion  68  on a second end of outer ring  60 . Other means of tightening outer ring  60  may also be employed, such as a clasp (not shown) or a spring or other type of elastic member (not shown). The compensation material for this embodiment need not be elastic but can be any flexible textile type material having the appropriate thickness (defined by thickness of abrasive pad to be used) and the ability to withstand the lens machine environment including heat and lap forming.  
         [0028]    Outer ring  60  further includes magnets  70  disposed therein and alignment pins (shown below with reference to FIG. 7B) disposed thereon. Magnets  70  are positioned on or in protrusions  68  that radiate outward from outer ring  60 , although, if space allows, they may be positioned directly on or in outer ring  60  itself. Preferably, three magnets  70  are incorporated into the structure of outer ring  60  and are mounted in protrusions  68  that are spaced at equidistant points about the circumference of outer ring  60 .  
         [0029]    Referring now to FIG. 7B, alignment pins  71  are shown depending from outer ring  60 . Alignment pins  71  depend from the surfaces of protrusions  68  opposing the surfaces in which the magnets are disposed. Alignment pins  71  are configured and dimensioned to be received in holes  73  in a compensation plate, shown generally at  75 , configured to support a compensation member incorporating an inner ring and outer ring  60  between which a piece of compensation material is held taught. Compensation plate  75 , which may optionally include a spacer  81  to support the compensation material, thereby preventing its adherence to compensation plate  75 , is attached to the track portion that extends into the lens finishing apparatus to deliver the compensation member to the carriage of the lens finishing apparatus. The positioning of alignment pins  71  effectuates the removal of the compensation member from the carriage, as is described below with reference to FIG. 9.  
         [0030]    If compensation member  56  is employed, a carriage, shown generally at  72  in FIG. 8, is the carriage for use in the lens finishing apparatus. Carriage  72 , which is similar in construction to carriage  24  as shown in FIG. 2, comprises a ring member  74  having a plurality of brackets  76  depending therefrom at points equidistant from each other. Brackets  76  are configured to house bearings  77  in similarly facing surfaces thereof. Bearings  77  enable carriage  72  to communicate with the apparatus and to respond to the movements of the struts (shown above with reference to FIG. 2). Magnets  78  are disposed on or within the similarly facing surfaces of each bracket  76  and are positioned to correspond with the positioning of the magnets of the outer ring as well as being oriented so that polarity of each of the magnets provides for attractive forces on the compensation member  56 .  
         [0031]    The operation of a lens finishing apparatus incorporating compensation member  56  is described with reference to FIG. 9. An operator of a lens finishing apparatus incorporating the carriage (shown at  72  with reference to FIG. 8) fits the compensation material over the inner ring and secures the compensation material thereto by tightening the outer ring. In a manner similar to that described with reference to FIG. 1, compensation member  56  is removably mounted to it respective compensation plate on track portion  14 . Drive motor  16  is then actuated and causes track portion  14  to extend into the lens finishing apparatus, where the compensation plate having compensation member  56  positioned thereon is disposed between lap  20  and the carriage. To transfer compensation member  56  to the carriage, the carriage is brought into proximity with compensation member  56  such that magnets  70  attract the magnets of the carriage, thereby causing compensation member  56  to magnetically adhere to the carriage and thereby effecting the transfer of compensation member  56  from track portion  14  to the carriage. Upon completion of the transfer of compensation member  56  to the carriage, the compensation plate is removed from the lens finishing apparatus by retracting track portion  14  from the lens finishing apparatus.  
         [0032]    To remove compensation member  56  from the carriage, track portion  14  is extended so as to be disposed proximate the carriage and lap  20 . The carriage having compensation member  56  magnetically adhered thereto is lowered such that the holes disposed in the compensation plate receive the alignment pins depending from compensation member  56 . Holes  73  may include beveled edges  74  to reduce precision necessary to facilitate engagement of pins  71  with holes  73 . Track portion  14  is then retracted from the lens finishing apparatus, thereby slidingly breaking the magnetic attraction between magnets  70  and the magnets disposed in the carriage.  
         [0033]    In the lens finishing operation, when either of the above mentioned embodiments are employed, the carriage extends in the direction of the lap such that one side of the compensation member contacts the surface of the lap and an opposing side of the compensation member is contacted by the lens blank. The lap is then deformed under an application of heat. The compensation member, which substantially matches the thickness of fining and polishing pads positioned between the lap and the lens blank, provides a compensation measure that enables the lap to be more accurately deformed to match the contour and curvature of the lens blank when a fining and polishing pad is disposed between the lens blank and the lap. Accuracy in the deformation of the lap enables the lens blank to be more accurately finished to the desired prescription.  
         [0034]    While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration only, and such illustrations and embodiments as have been disclosed herein are not to be construed as limiting to the claims.