Abstract:
A method and apparatus for processing a periphery of a lens includes holding the lens to be processed, providing at least one edge processing system, disposing the at least one edge processing system and the periphery of the lens proximal one another in a processing position, dry edging the periphery of the lens with the at least one edge processing system to a predetermined configuration, and cooling the periphery of the lens during the edging step with a cooling medium other than a liquid.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for processing a peripheral edge of a lens, and more particularly, a method of cooling the peripheral edge of the lens during dry edging processes, and an apparatus therefor. 
       BACKGROUND OF THE INVENTION 
       [0002]    An eyeglass-lens processing apparatus for processing a peripheral edge of an eyeglass lens in conformity with the shape of an eyeglass frame is known. With this type of apparatus, the eyeglass lens after being roughly processed is subjected to finish processing by a finish abrasive wheel, and the peripheral edge of the eyeglass lens is further subjected to edge finishing, such as a bevel, polishing, chamfering and/or grooving. 
         [0003]    Traditionally, the edging was manually performed by an operator using a so-called hand grinder having a rotating conical abrasive wheel. More recently though, processing apparatuses are provided with a rotating abrasive wheel having different abrasive portions for roughing, finishing, and polishing the lens edge. Examples of edge processing apparatuses include the LE-9000SX/LX/EX/DX Series and the SE-9090 Express manufactured by Nidek Co., Ltd. of Japan. 
         [0004]    These type of edge processing apparatuses provide a vast improvement over manual grinding in terms of high speed production, versatility in type of lens material, and precision. Generally, in an apparatus for processing a periphery of an eyeglass lens, the rotating grinding abrasive wheel is caused to press against the periphery of the lens by applying a fixed load between the abrasive wheel and the lens while rotating the lens held on a lens rotating shaft (lens chuck shaft), thereby carrying out the processing. During the rough, finish and polish processing of a glass or plastic lens, water may be supplied in order to cool the lens edge and to remove processing wastes. The used water is discharged through a drain such as a drainage port provided in a lower part of the processing chamber. When rough processing a polycarbonate lens, however, water cannot be used without causing a melting or swarfing of the lens material. Thus, a dry roughing process is performed on a polycarbonate lens, although water can be used to cool the lens edge during the finishing and polishing stages. 
         [0005]    As a result of the dry roughing, the high speed processing tends to increase the heat and stress in the eyeglass lens as it is being processed. In turn, the heat build up on the eyeglass lens can lead to lens slippage as it is being held in the lens chuck, as well as causing increased wear of the abrasive wheel. More specifically, the lens chuck generally includes opposing blocks, each of which has an adhesive pad for holding the lens therebetween. The increased heat encountered during the dry roughing process may cause a decrease in the effectiveness of the adhesive pads, and thus tends to cause the lens to slip. 
         [0006]    Accordingly, there is a need for a method and apparatus for rough processing the peripheral edge of an eyeglass lens, in particular a polycarbonate lens, in a high speed production process while avoiding swarfing, the build up of heat during processing and the consequences thereof. 
       SUMMARY OF THE INVENTION 
       [0007]    These and other objects of the present invention are satisfied by a method for processing a periphery of a lens, comprising holding the lens to be processed; providing at least one edge processing system; disposing the at least one edge processing system and the periphery of the lens proximal one another in a processing position; dry edging the periphery of the lens with the at least one edge processing system to a predetermined configuration; and cooling the periphery of the lens during the dry edging step with a cooling medium other than a liquid. In a preferred embodiment, a gaseous substance such as cooled, compressed air is directed to an area proximal the periphery of the lens. 
         [0008]    A further aspect of the invention provides an apparatus for processing a periphery of a lens, comprising: a lens holding system; at least one edge processing system; control means for controlling operation of the lens holding system and the at least one edge abrasive processing system so as to process the periphery of the lens to a predetermined configuration; and a cooling system for cooling the periphery of the lens during edge processing with a cooling medium other than a liquid. 
     
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0009]    These and other objects, features, and advantages of the present invention will become more readily apparent to those skilled in the art upon reading the following detailed description, in conjunction with the appended drawings in which: 
           [0010]      FIG. 1  is a schematic drawing of a conventional lens processing apparatus with a cooling apparatus connected thereto in accordance with a preferred embodiment of the present invention. 
           [0011]      FIG. 2  is a schematic drawing thereof with the outer housing removed. 
           [0012]      FIG. 3  is a perspective view of the inside of the grinding chamber thereof with the cooling apparatus connected thereto in accordance with a preferred embodiment of the present invention. 
           [0013]      FIG. 4  is a further perspective view of the inside of the grinding chamber. 
           [0014]      FIG. 5  is a perspective view of the nozzle assembly used with the cooling apparatus in accordance with a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Referring to  FIG. 1 , the external configuration of a typical eyeglass-lens processing apparatus, or edger, is generally shown by reference numeral  10 . The apparatus  10  may include an eyeglass-frame-shape measuring device  12 , such as that disclosed in U.S. Pat. Nos. 5,228,242, 5,333,412, or U.S. Pat. No. 5,347,762 (Re. Pat. No. 35,898), within the main body  1  of the apparatus. A switch panel section  410  having switches for operating the frame-shape measuring device  12  and a display  415  for displaying processing information and the like may be disposed in front of the frame-shape measuring device  12 . The apparatus  10  also preferably has a switch panel section  420  having various switches for inputting processing conditions and the like and for giving instructions for processing, and an openable window  402  for gaining access to a processing chamber  405 . In accordance with a preferred embodiment of the present invention, a cooling device  20  is connected to the processing chamber  405 , as described in further detail below. 
         [0016]      FIG. 2  is a perspective view illustrating the arrangement of a typical lens processing section disposed in the casing of the main body  1 . A carriage unit  700  is mounted on a base, and a subject lens LE clamped by a pair of lens chuck shafts of a carriage  701  is ground by a group of abrasive wheels  602  attached to a rotating shaft  601 . The group of abrasive wheels  602  preferably include a rough abrasive wheel  602   a , a finish abrasive wheel  602   b , and a polishing abrasive wheel  602   c . Different wheels can also be provided for glass, polycarbonate and plastic lenses, and/or the polishing abrasive wheel may be eliminated, or any combination thereof depending upon the desired processing. Still further, more than one group of said abrasive wheels may be provided as in, for example, the Nidek SE-9090 mentioned above. The rotating shaft is rotatably attached to the base by a spindle  603 . A pulley  604  is attached to an end of the rotating shaft  601 , and is linked through a belt  605  to a pulley  607  which is attached to a rotating shaft of an abrasive-wheel rotating motor  606 . Other types of systems for rotating the shaft, as are well known in the art, could of course be provided instead. An optional lens-shape measuring section  500  may be provided in the rear of the carriage  701  and an optional edge processing section  800  may be provided in the front side for certain type of edging, such as chamfering and grooving the periphery of the lens. 
         [0017]    Referring also to  FIGS. 3 and 4 , the present invention provides a cooling apparatus  20  for supplying a cooling medium other than a liquid, e.g., water, glycol, or other liquid coolant, to the lens edge during processing, and in particular, during the dry edging process of a lens, such as a polycarbonate, CR39, or hi-index lens. In a preferred embodiment, the cooling apparatus  20  is a pneumatic cooling device, and more preferably a vortex tube such as vortex tube Model 106-2-h available from C.C.Steven &amp; Associates, Ventura, Calif. The vortex cooling apparatus  20  is preferably self-contained and enclosed in a 6″×6″ (15 cm×15 cm) or similar sized control box  22 . The control box  22  can be placed directly next to edging apparatus  10 , or if desired mounted up to approximately 30″ (0.8 m) away from the apparatus  10  in order to reduce the footprint thereof. 
         [0018]    When using a vortex tube, air from a standard air compressor (80 psi) enters the vortex tube at approximately 70° F. (21° C.) and is transformed to a temperature of 30°-40° F. (−1°-5° C.) As known in the art in vortex tube operation, compressed air enters a tangentially drilled stationary generator which forces the air to spin down the long tube&#39;s inner walls toward the hot air control valve, achieving sonic speeds of up to 1,000,000 RPM. A percentage of this air, now at atmospheric pressure, exits through the needle valve at the hot air exhaust. The remaining air is forced back through the center of the sonic-velocity airstream where, still spinning, it moves at a slower speed, causing a simple heat exchange to take place. The inner, slower-moving air column gives up heat to the outer, faster moving air column. When the slower inner air column exits through the center of the stationary generator and out the cold exhaust, it has reached a lower temperature, preferably 30°-40° F. (−1°-5° C.) when exiting the cooling apparatus  20 . 
         [0019]    The cooling apparatus  20  is arranged for use with the edging apparatus  10  by attaching a flexible tube  24  to the cold air exhaust and running the flexible tube  24  to the internal processing chamber of edging apparatus  10 . The other end of flexible tube  24  is connected to a nozzle assembly  26 , which is directed to the point of the lens contacting the roughing wheel  602   a . If the edging apparatus has more than one group of abrasive wheels  602 , the cooling apparatus  20  preferably includes a nozzle assembly  26  for each dry roughing wheel thereof. As illustrated in  FIG. 5 , in a preferred embodiment, the nozzle assembly  26  includes a flat nozzle or a flat angled nozzle  28 , such as Model Nos. 920, 921, or 961 available from Silvent AB of Boras, Sweden, connected via a ball swivel joint  30  so as to accurately direct the cooling medium to the point of contact and reduce noise. It has been found that by supplying the cooled air from cooling apparatus  20  to the edge of the lens, the build up of heat in the lens is reduced and consequently, the adhesive pads of the lens chuck are better able to maintain the lens in position. Hence, lens slippage is reduced. 
         [0020]    In order to install the cooling apparatus  20  for use with a conventional edger, such as the Nidek 9000 EX Edger, the following preferred method of installation is followed. A hole  32  having a preferred diameter of 7/16 inch (1.11 cm) is first drilled in the front inside panel of the grinding chamber  405 . The center of the drilled hole is preferably oriented 5 cm (1.9″) from the left side of the grinding chamber and 1 cm (0.4″) below the top of the lower panel to allow adequate clearance for the groove arm of the edge processing section  800  to raise and lower unrestricted. This hole  32  will be the location of the mounting of the nozzle assembly  26 . 
         [0021]    A threaded connector, such as a LOC-LINE connector, is placed inside the drilled hole  32 , from the inner side of the grind chamber  405 . A brass elbow fitting is preferably placed opposite the LOC-LINE fitting, on the front out-side of the grinding chamber  405  and the two fittings are threaded together and tightened until snug and securely mounted. As known in the art, washers can be used as spacers if necessary to provide a tight fit. 
         [0022]    A preferably ¼ inch (0.635 cm) diameter hole is drilled wherever convenient through the rear panel of the apparatus  10  to run the tubing  24  through, and out to the cooling apparatus  20 . The tubing  24  is preferably water resistant since it will be used within the grinding chamber where water is used to cool glass and plastic lenses. A typical tubing would be PUN-H blue tubing available from Festo Corporation, Hauppauge, N.Y. The opposite end of the tubing is connected inside the apparatus  10  to an appropriate fitting attached to the brass elbow fitting at the grinding chamber  405 . The tubing  24  thus defines the cold line for delivery of the cooled air to the nozzle assembly  26 . Since tubing  24  will be delivering cooled air, it is preferred that this line be properly insulated throughout the entire inside of the machine to prevent condensation from gathering and potentially damaging the edger apparatus  10 . It is also important to ensure that the tubing line  24  does not rest anywhere that would restrict movement of motor axes. 
         [0023]    After the nozzle assembly  36  and cold line  24  have been affixed to their proper locations, the cooling apparatus  20  can be placed anywhere desired outside of the apparatus and the cold line  24  connected to an appropriate fitting, preferably marked “Air OUT” on the cooling apparatus  20 . Compressed air is supplied to the cooling apparatus  20  by using the female cable in the back of the edger preferably labeled “Pump  2 ” and plugging it into the matching male cable on the cooling apparatus  20 . The remaining female cable from the cooling apparatus  20  is then plugged into the edger apparatus  10  where the female cable was just removed. Afterward, tubing is connected to the appropriate fitting, preferably marked “Air IN” on the cooling apparatus  20 , and the other end of the tubing is connected to any available compressed air supply. As the “Air IN” tubing line is not cold, it does not need to be insulated. 
         [0024]    The last step is to adjust the air regulator knob  34  to the desired air pressure (preferably 80 psi (5.6 kg/cm 2 )), and adjust the temperature with the cooling regulator or hot air exhaust knob  36 . The cooling apparatus  20  will preferably only be activated when the switch  38  is in the ON position and the water curtain (optional) of the edger apparatus  10  is activated simultaneously. Preferably, the cooling apparatus  20  is automatically energized when apparatus  10  is cycled on. Additionally, the cooling apparatus  20  can preferably be manually turned off when edging plastic or glass lenses by turning switch  38  to the OFF position. Normally plastic and glass lenses use water and do not require cooling; thus, by turning off the cooling apparatus  20  un-needed air would not be consumed. 
         [0025]    Although only preferred embodiments and examples are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings including, but not limited to, the application of the claimed invention to other types of lenses other than eyeglass lenses, lenses made of materials other than those specifically mentioned herein, and other types of edge processing systems other than abrasive systems or abrasive wheels. All of such modification and variation are deemed within the purview of the appended claims without departing from the spirit and intended scope of the invention.