Abstract:
A lens deblocking system ( 1 ) used for removing a lens ( 51 ) from an edging block ( 22 ). The system ( 1 ) includes opposed movable arms ( 4, 5 ) that are constrained to travel longitudinally within an aperture ( 3 ) so as to grip a lens ( 51 ) that is adhesively secured to an edging block by a pad ( 52 ). The edging block ( 22 ) is held within a clamp ( 11 ) that resides on a collet closer ( 63 ) which may be rotated by activating an air cylinder ( 82 ). A cam push block ( 91 ) is linked to file cylinder ( 82 ) as well as a cam arm ( 98 ) that is attached to a spindle ( 96 ) extending from the collet closer ( 63 ). In response to the movement of the push block ( 91 ) a rotational motion is imparted to the clamp ( 11 ) via the cam arm ( 98 ). The rotation of the clamp ( 11 ) occurs while the lens ( 51 ) is still constrained against rotational movement between the movable arms ( 4, 5 ) thereby physically breaking the bond between the pad ( 52 ) and the clamp ( 11 ) and permitting subsequent manual removal of the pad ( 52 ) from the lens ( 51 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention pertains generally to the field of lens fabrication and more particularly to the removal of a lens from a lens retaining block. 
     2. Description of Prior Art 
     The fabrication of lenses includes processing steps to generate both the surfaces of the lenses so as to impart specific optical properties to the lens, and also to accomplish the peripheral alteration, or edging, of the lenses. The first step in altering a lens is typically the generation of a surface on a partially finished lens blank. The second step in processing the lens is normally the peripheral alteration of the shape of the surfaced lens. The lens blanks and surfaced lenses may be, for example, spherical, cylindrical, optical flats, aspherical, or of multiple focal lengths. Once the lenses have been finished they may be put to a variety of uses such as spectacle lenses, camera lenses, or lenses used in instrumentation. 
     Edging the lens to obtain a desired shape involves a series of steps. Typically the optical center and, optionally the cylinder axis, of the lens is located and marked on a face. In those instances when the lens to be edged contains an asymmetric surface it is necessary that the optical center and cylinder axis of the lens be located and marked. Next, the lens is attached to a lens block by some type of holding mechanism, such as an adhesive, so that the optical center, and optionally the cylinder axis, of the lens are aligned with the center point and cylinder axis of the block. The desired peripheral shape is then imparted to the lens. During edging the temperature of the lens rises. The lens is often exposed to the steady flow of a coolant in order to prevent the lens from cracking. 
     Some means must be provided to attach the lens blank to the edging block with a bond that will not fail during alteration yet is possible to break once alteration is complete. In practice, the lens may be removed from the block by a variety of methods. For example, the lens may be pried from the block. However, this method has the disadvantage that the lens is often chipped, scratched, or otherwise damaged by the act of prying. This method can be facilitated by immersing the lens and block in hot water for a short period of time. However, some plastic lens materials cannot withstand such temperatures. 
     Another method of lens removal is the use of a fluid that is forced against the surface of a blocking pad that is adhered to the lens, thereby reducing the force holding the pad to the lens or block. Approximately two atmospheres of fluid gauge pressure are sufficient to reduce the holding force such that the lens may be easily separated from the block. The fluid used to achieve removal should comprise a gas or liquid that is nontoxic and which will be inert with respect to the lens block, the blocking pad, and the lens. Representative examples of useful gases for pneumatic lens removal include air, nitrogen, carbon dioxide, helium, and fluorocarbon gases. Representative examples of useful liquids for hydraulic lens removal include water, hydraulic oils, mineral oils and fluorocarbon liquids. 
     Another method of lens removal employs a tab that is pulled in the direction of the plane of the blocking pad so as to cause a reduction in the thickness of the pad and a progressive disengagement of the pad from the interface between lens and block. Removal may also be accomplished by placing the combination of lens, blocking pad and block into a cavity of the mounting block and then rotating the lens and the block in opposite directions with respect to each other, thereby causing them to separate. A specially designed hand tool may also be provided to accomplish this same result. The tool is not as wide as the mounting block and facilitates removal by making it easier to grasp the edge of the lens. 
     The latter method of lens removal is disclosed in U.S. Pat. No. 3,962,833 entitled METHOD FOR THE ALTERATION OF A LENS AND AN ADHESIVE LENS BLOCKING PAD USED THEREIN, issued to Johnson on Jun. 15, 1976: The problem repeatedly grasp pliers or a similar tool to remove the lens. Some level of skill is required to perform the lens removal operation rapidly while avoiding damage to the lens. After a period of time in such an occupation, the operator is likely to suffer various forms of fatigue and injury including, for example, carpal tunnel syndrome. 
     A final issue to be faced when removing a lens from an edging block is the relatively recent development and use of hydrophobic and oleo phobic coatings, which cause the surface of coated lens to have a relatively low coefficient of friction. The relatively slick frictionless lens surface required the development of adhesive pads having relatively greater adhesion which caused the aforementioned methods of lens removal to be generally less effective. In particular, the conventional methods of lens deblocking resulted in crazing, pitting or other scarring and damage to the lens, or additional treatment step to remove adhesive residue from the lens. 
     SUMMARY OF THE INVENTION 
     The current invention is an improved apparatus and method for the removal of a lens from an edging block. The present invention retains the blocked lens by means of a collet chuck or clamp. The blocked lens resides on a pad which supports the lens on the edging block while protecting the lens from abrasion or damage from the block itself. A pair of opposed slidable lens clamps or arms are pneumatically advanced to grip the blocked lens along portions of the lens edge. Once the lens is secured by the lens clamp, the collet chuck is rotated approximately forty five degrees, thereby breaking the bond between the lens and the edging block. The lens clamps may then be retracted away from the lens edges and the lens may be manually removed from the pad. 
     The surface area of the combined edging block and pad is typically on the order of fifty percent of the total lens surface area. Thus when the lens is freed from the pad by the twisting motion of the collet, the lens is still sufficiently supported by the pad, which itself still rests on the edging block, to prevent the lens from falling off of the pedestal formed by the collet. After the lens is removed, the pad may be lifted from the edging block and then the edging block may be removed from the collet. 
     In a preferred embodiment of the invention, the device includes a pair of collet chucks or clamps spaced apart along a line that is substantially parallel to a line formed by the gripping edges of the lens clamps. In this embodiment, a blocked lens is placed on each collet and both lenses are gripped simultaneously by the opposed jaws of the lens clamps. The collets are rotated simultaneously by means of a manually operated switch, thereby freeing each lens from its respective pad. When the lens clamps are retracted, each lens may be easily lifted from its respective pad. These and other advantages of the present invention will become apparent by referring to the accompanying drawings and the detailed description of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an automated edged lens deblocking system constructed according to the principles of the present invention; 
         FIG. 2  is a perspective view of one of the many various types of edging block that may be utilized by the system depicted in  FIG. 1 ; 
         FIG. 3  is a first perspective view of an edging block and pad mounted on a lens as utilized by the system depicted in  FIG. 2 ; 
         FIG. 4  is a second perspective view of an edging block and pad mounted on a lens as utilized by the system depicted in  FIG. 1 ; 
         FIG. 5  is a perspective view of two lenses mounted on a pad and edging block while being retained by the deblocking system depicted in  FIG. 1 ; 
         FIG. 6  is a perspective view of the automated edged lens deblocking system depicted in  FIG. 1  with the chassis cover removed; 
         FIG. 7  is a sectional view taken along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a perspective view of the collet depicted in  FIG. 1 ; 
         FIG. 9  is a top plan view of the collet illustrated in  FIG. 1 ; 
         FIG. 10  is an exploded perspective view of the automated edged lens deblocking system depicted in  FIG. 1 ; 
         FIG. 11  is a top plan view of the automated edged lens deblocking system depicted with edging blocks and lenses mounted on the collets in an unclamped position; 
         FIG. 12  is a top plan view of the automated edged lens deblocking system depicted with edging blocks and lenses mounted on the collets in a clamped position; 
         FIG. 13  is a top plan view of the automated edged lens deblocking system depicted with edging blocks and lenses mounted on the collets after the collets have been rotated from a first position to a second position; 
         FIG. 14  is a top plan view of the automated edged lens deblocking system depicted with edging blocks mounted on the collets after the lenses have been removed; and 
         FIG. 15  is a bottom perspective view of the automated edged lens deblocking system depicted in  FIG. 6  with some components removed for clarity. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , an automated edged lens deblocking system constructed according to the principles of the present invention is shown generally at 1. The deblocking system  1  includes a protective cabinet  2  typically composed of a durable metal or plastic material. The top surface  9  of the cabinet  2  is formed to include a generally rectangular aperture or slot  3  above which a pair of opposed arms  4  and  5  are slidably mounted by means of supports  6  and  7 . The supports  6  and  7  permit movement of the arms  4  and  5  in the directions generally indicated by arrow  8 . The top surface  9  also includes an opening or first circular aperture  10  which permits access to a first edging block clamp  11 . A second circular aperture  12  is located in a symmetrical position opposite the rectangular aperture  3 . The circular aperture  12  permits access to a second collet or edging block clamp  13 . 
     As best seen in  FIGS. 8 and 9 , each edging block clamp, such as first edging block clamp  11 , includes three distinct, separable regions or jaws  31 ,  32  and  33 . Each region includes a series of inclined, angular and substantially planar surfaces, such as surfaces  34 ,  35 ,  36  and  37 , with each surface joining adjacent surfaces along a line, such as lines  38 ,  39  and  40 . Each region  31 - 33  also includes a substantially circular aperture or bore, such as bores  41 ,  42  and  43 , for example. A ridge  44  extends across the floor  45  of jaw  32 , while a collinear ridge  46  extends along the floor  47  of jaw  33 . Each of the features of the edging block clamp  11  facilitates the ability of the clamp to mate with or grip an edging block  22  as depicted in  FIG. 2 . Additionally, the edging block clamp  11  is textured with a Carbinite high friction coating to facilitate gripping of the edging block  22  by the clamp  11 . The Carbinite coating is available from Carbinite Metal Coatings, 508 Pittsburgh Road, Butler, Pa.  16002 . 
     In a preferred embodiment the system  1  is pneumatically powered with air being introduced at inlet  14  of regulator assembly  17 , which also includes a regulating valve  15 , an air filter  18  and an air pressure indicator  16 . Several controls are accessible to the operator of the system  1 , including a first toggle switch  19  that causes the edging block clamps  11  and  13  to grip or release an edging block that may be placed upon them by moving jaws  31 - 33  in the directions indicated by the arrows  48 ,  49  and  50 , respectively. 
     As seen in  FIG. 2 , the edging block  22  includes a series of inclined surfaces, such as surfaces  23 ,  24 ,  25  and  26 , for example. Additionally the block  22  includes a diametric groove  27  which broadens to a keyway  30  at one end. The block  22  also contains a pair of substantially circular indentations  28  and  29 . At least some of the features such as the surfaces  23 - 26 , the groove  27 , the keyway  30 , the indentation  28  and indentation  29  are adapted to mate with and be gripped either by or within an edging block clamp, such as clamp  11 , when the block  22  is placed on the clamp  11  and toggle switch  19  is activated. In particular, the groove  27  is adapted to fit within and be retained by the ridges  44  and  46 . The operator of system  1  also has access to a second toggle switch  20  that causes the opposed arms  4  and  5  to move in one of the directions indicated by arrow  8 . A button  21  causes the edging block clamps  11  and  13  to rotate about a longitudinal axis. 
     Referring also to  FIGS. 3 and 4 , the adherence and securing of a lens  51  to the block  22  can be better appreciated. An adhesive pad  52 , having an adhesive material on each side, is affixed to the undersurface  53  of the block  22 . The bottom surface  58  of the adhesive pad  52  is affixed to the bottom side  54  of the lens  51 . The pad  52  includes a tab  57  which aids an operator in manually affixing and removing the pad as necessary. Due to the transparent nature of the lens  51 , the pad  52  and block  22  are directly visible through the lens when viewed through the top or outer lens surface  56 . The entire perimeter or edge  55  of the lens  51  remains completely accessible after the pad  52  is affixed to both the lens  51  and the block  22 . The pad  52  is affixed in preparation for any of numerous types of machining or treating operations to be performed on the edge  55  of the lens during manufacture. Once the machining and treatment operations are complete, the problem remains of safely removing the adhesive pad  52  from both the lens  51  and the block  22 . 
     As best seen in  FIG. 5 , a block  22  is mounted on each of the edging block clamps  11  and  13 , each block  22  supporting a pad  52 . The opposed arms  4  and  5  of the deblocking system  1  are movable in the direction of arrow  8 , and by actuating switch  20  the operator is able to urge both arms to simultaneously move toward the nearest edge  55  of the lens  51 . A urethane cushion  59  is affixed to the inner surface  60  of each arm  4  and  5  to provided a firm grip on the lens  51  without damaging the edge  55 . 
     Referring also to  FIGS. 6 ,  7  and  10 , the internal construction and function of the system  1  may be better understood. The internal components of the system  1  are supported by a base plate  61  which may be composed of any rigid material. Mounted on the base plate  61  is a collet closer  62  which activates the first edging block clamp  11 , while oppositely mounted collet closer  63  operates clamp  13 . Also mounted on the base plate  61  is a support block  64  which itself supports a clamp  65 , the block  64  and clamp  65  defining a path for feather shafts  66  and  67 . 
     A pillow block  71  is affixed to a slide rail  75 . Feather shafts  66  and  67  pass through a pillow block  71  and permit the assembly of the pillow block  71  and the slide rail  75  to move longitudinally along the feather shafts  66  and  67 . A shaft end support block  72  is mounted so as to serve as a stop for the pillow block  71  and includes shaft passageways  73  and  74 . Mounted on the slide rail  75  is an air cylinder  76  which receives pressurized air, via toggle valves  19  and  20 , from the pressure regulator assemblies  17  and  68  affixed to the base plate  61  by means of a regulator mounting plate  69  which is also supported by standoff  70 . The air cylinder  76  is linked to an arm pusher  77 , the arm pusher being affixed to the arm  5  along indentation  79 . A guide rail  78  constrains movement of the arm pusher  77  along a line that is parallel to the shafts  66  and  67  as well as the rectangular aperture  3 , thereby causing the arm  5  to be urged longitudinally along a line defined by the path of the guide rail  78  whenever the air cylinder  76  is energized. 
     In a preferred embodiment the air cylinder or pneumatic piston  76  is a Bimba FS-091.25 air cylinder including a rod  87  having a 1.25 inch stroke length and which is marketed by the Bimba Manufacturing Company located in Monee, Ill. A second air cylinder  80  is mounted on a second pillow block  81 , the second pillow block  81  also being slidably mounted on shafts  66  and  67 . The second air cylinder  80  including rod  86  is coupled to the arm  4  such that operation of the first toggle valve  19  causes each air cylinder  76  and  80  to simultaneously advance the arms  4  and  5 , respectively, toward the opposing arm and thereby grip the lens  51  between the opposed arms  4  and  5 . The cylinders  76  and  80  exert substantially horizontal and substantially equal forces, with variations in the amount of individual force extended by each individual cylinder being balanced mote precisely by the independent motion of each cylinder  76  and  80  which are slidably mounted on the pillow blocks  71  and  81  respectively. The pressurized air used to operate the air cylinders  76  and  80  enters the toggle valve  19  via connection  84 , the actual air hoses employed being omitted from the figures for the sake of clarity. 
     Once the lens  51  is firmly secured between the arms  4  and  5 , an additional air cylinder  82  is employed to impart a twisting motion to the edging block clamps  11  and  13 . In a preferred embodiment, the edging block clamps  11  and  13  are mounted on rotary bases  83  and  89 , respectively. As best seen in  FIG. 15 , the additional air cylinder  82  is mounted on the bottom surface  85  of the base plate  61  by means of a riser  86 . The button  21  is connected to an air valve  90  which is in fluid communication with the additional air cylinder  82 , the actual interconnecting hoses being omitted for clarity. The air cylinder  82  is connected to a cam push block  91  which is formed to include two orifices  92  and  93 . Each orifice is associated with an individual collet closer, with only the collet closer  63  being shown for the sake of clarity. 
     The collet closer  63  is rotatably secured to the base plate  61  by means of a bearing washer  94  and a shim  95 , both of which surround a spindle  96 . A cam arm  98  is rigidly secured around the spindle  96  between the shim  95  and a cap  97 . Extending from an end region of the cam arm is a shaft  99  that is rotatably retained within the orifice  93 . Activating the push button  21  causes the cam push block  91  to advance in the direction of arrow  100  until the block  91  is pre vented from further motion in the direction of arrow  100  by the presence of the stop block  101 . The motion of the cam push block  91  causes shaft  99  to also move in the direction of arrow  100  and thereby cause the collet closer  63  to rotate generally in the direction of arrow  102 . 
     Referring also to  FIGS. 11 ,  12 ,  13  and  14 , the operation of the system  1  can be better understood.  FIG. 11  depicts the system  1  in an initial position when the lenses  51 , having been previously processed while secured to the edging blocks  22 , are placed onto the block clamps  11  and  13 . The toggle switch  20  is then moved from the first position shown in  FIG. 11  to the second position shown in  FIG. 12 , the switch  20  causing the block clamps  11  and  13  to security grip the edging blocks  22 . The toggle switch  19  is then moved from the position shown in  FIG. 11  to the position shown in  FIG. 12 , thereby causing the arms  4  and  5  to move toward the opposing arm as well as the nearest edge of the nearest lens  51 . The arms  4  and  5  self center, that is, stop at a location which causes the lens  51  to be securely gripped regardless of the exact shape and position of each lens  51 , because each arm  4  and  5  is moved into position by the action of the air cylinders  80  and  76 , respectively, which are free to travel with their respective pillow blocks  81  and  71 , respectively, until the force exerted by each cylinder  60  and  76  on the arms  4  and  5  is substantially equal, regardless of the specific position of each cylinder. 
     The push button  21  is then pressed causing the cam push block  91  to impart rotation to the block clamps  11  and  13 , thereby creating the geometry depicted in  FIG. 13 . The groove  27  can be seen to have rotated through an approximately forty five degree angle. The effect of this rotational displacement is to break the adhesive bond between the adhesive pad  52  and the lens  51  while leaving the lens  51  still securely gripped between the arms  4  and  5 .  FIG. 14  depicts the orientation of the groove  27  after the push button  21  has been released. 
     By returning the toggle switch  19  to the position shown in  FIG. 14 , the arms  4  and  5  will be withdrawn from the lenses  51 . Since the adhesive bond between the edging blocks  22  and the adhesive pad  52  has been broken, each lens  51  can be lifted from the edging block  22  and the adhesive pad manually removed from the lens by means of the tab  57 . The toggle switch  20  is then returned to the position shown in  FIG. 14  in order to allow the removal of the edging blocks  22  from the block clamps  11  and  13 . 
     The foregoing improvements embodied in the present invention are by way of example only. Those skilled in the materials processing field will appreciate that the foregoing features may be modified as appropriate for various specific applications without departing from the scope of the claims. For example, the item to be loosened due to the twisting motion of the block clamps  11  and  13  may be some device or element other than a lens  51 . Further, the bond that is broken between the edging blocks  22  and die pad  52  may be some linkage other wan an adhesive, such as a mechanical, electrical or residual magnetic attraction or force.