Abstract:
A machine for shaping blanks to create a lens, the machine comprising a pair of worktables each to support one of the blanks to be shaped, and each to be driven by a first motor, a drill bit unit provided with a rotatable drill bit, an elevator supporting the drill bit unit and shiftable along a vertical axis to raise or lower the drill bit with respect to the blank on each worktable, and a second motor for driving the elevator, a carriage carrying said elevator and shiftable along a horizontal axis to move the drill bit back and forth with respect to said blanks, said carriage being driven by a third motor, and a processor adapted to coordinate the operation of the first, second and third motors to cause the drill bit to shape the blanks to form the lenses of a desired geometry.

Description:
[0001]     This application is a Continuation in Part, and claims the benefit of U.S. application Ser. No. 09/991,870, filed on Nov. 26, 2001. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates generally to a machine adapted to mill blanks to create filter lenses for a clip-on accessory which hitches onto the frame of prescription eyeglasses having a pair of optical lenses, the filter lenses then being in registration with the optical lenses to protect the wearer of these eyeglasses from harmful radiation. More particularly, the invention relates to a computer-controlled milling machine which produces filter lenses for a clip-on accessory whose geometry matches that of the frame of the eyeglasses.  
         [0004]     2. Status of Prior Art  
         [0005]     An individual who is myopic (near-sighted) or hyperopic (far-sighted), or suffers from other visual defects normally wears a pair of eyeglasses in which optical lenses are mounted in a frame having temple pieces hinged thereto. The optical lenses are designed to correct for the visual defects of the wearer and are therefore usually prescribed by an optometrist or an eye doctor.  
         [0006]     The same individual may on occasion be exposed to harmful radiation, such as intense sunlight, rays from a welding arc or from a laser beam instrument. He therefore requires sunglasses or other radiation protection glasses whose filtration characteristics depend on the nature of the harmful radiation to which the wearer is exposed.  
         [0007]     When an individual wearing prescription eyeglasses switches to a pair of sunglasses to protect his eyes from harmful radiation, it is essential that the filter lenses of these sunglasses have the same corrective optical properties as the optical lenses in his eyeglasses—otherwise he will not see clearly through his sunglasses. However, a pair of prescription sunglasses tailored to the eyes of its wearer is at least as expensive as a costly pair of prescription eyeglasses. Hence the wearer may be reluctant or unable to bear these additional costs.  
         [0008]     To avoid the need for prescription sunglasses, the wearer of prescription eyeglasses can convert his eyeglasses to sunglasses simply by hitching onto the frame of his eyeglasses a clip-on accessory. This accessory is provided with a pair of filter lenses that register with the optical lenses of the eyeglasses to filter out harmful radiation.  
         [0009]     The typical clip-on is a universal accessory in the sense that it is capable of being clipped onto the frame of a pair of prescription eyeglasses regardless of the geometry or design of this frame. This is a distinct advantage, for in this era of “designer” frames, eyeglasses are now marketed in a broad range of distinctly different styles.  
         [0010]     The disadvantage of a universal clip-on accessory which may have discouraged its more widespread use is that the standardized design of a clip-on accessory includes round filter lenses. This design is usually incompatible with the frame design of the eyeglasses onto which the accessory is hitched. It is the frame of eyeglasses that impart to eyeglasses its overall appearance. Thus if the frame is composed of trapezoidally-shaped half-sections and the filter lenses of the clip-on accessory hitched thereon are circular, the appearance of the accessory is then incongruous and unappealing.  
         [0011]     Hence while a clip-on accessory may be said to fit onto a pair of prescription eyeglasses, it would be more realistic to say that the clip-on accessory misfits these eyeglasses and renders them unattractive.  
         [0012]     To obviate this drawback, there is disclosed in PCT patent publication WO 95/04635 “Clip-on Sunglasses and System for Cutting Clip-on Sunglasses” a machine to custom-cut the filter lenses of the clip-on accessory so as to impart thereto the same size and shape as the half-sections of the frame of the eyeglasses onto which the clip-on is hitched. To this end, the machine includes a holder for the eyeglasses to be copied and for the clip-on, and a cutter and stylus to trace the contours of the eyeglasses and to custom-cut the clip-on in accordance with this trace.  
         [0013]     Also disclosing a method of customizing a clip-on accessory is PCT patent publication WO 93/24856 (1993). In this method, the pair of filter lenses for the clip-on have their perimeters cut to conform to the contours of a particular pair of eyeglasses. Of prior art interest is U.S. Pat. No. 5,546,140 to Underwood which discloses a machine for custom-cutting clip-on sunglasses, the machine trimming the sunglasses to conform to the shape and size of a pair of eyeglasses.  
       SUMMARY OF THE INVENTION  
       [0014]     In view of the foregoing, the main object of this invention is to provide a computer controlled machine for milling blanks to create filter lenses for a clip-on accessory having a geometry which matches the geometry of the complementary half-sections of the eyeglass frame onto which the accessory is hitched.  
         [0015]     By a filter lens is meant any lens adapted to cooperate with the optical lens of the eyeglasses onto which the accessory is hitched to protect the eyes of the wearer from harmful radiation, or to improve his vision. Thus the filter lens of the accessory may be an optical lens which combines with the optical lens of the eyeglasses to create a compound lens for vision correction.  
         [0016]     Among the significant advantages in a clip-on accessory in accordance with the invention are the following: 
        A. The design of the clip-on accessory is fully compatible with that of the eyeglass frame onto which the clip-on is hitched whereby the attractive design of the eyeglasses is not degraded by the accessory. This is of particular value when the eyeglasses are those designed by a renowned designer and are costly.     B. Because the machine is computer-controlled, it creates a filter lens for a clip-on accessory whose geometry precisely matches that of a half-section of the frame of the eyeglasses.     C. Because the geometry of the clip-on accessory matches the geometry of the eyeglasses onto which it is hitched, it can readily be clipped onto the frame of the eyeglasses and requires no special handling.     D. The cost of manufacturing the clip-on accessory is relatively low, making it possible for the wearer of prescription eyeglasses to inexpensively convert his eyeglasses to sunglasses having the same prescription.        
 
         [0021]     More particularly, it is an object of this invention to provide a milling machine in which a blank to be milled is supported on a rotary worktable to be engaged by a drilling bit that is shifted along X and Y coordinates to cut the blank to form a filter lens having the desired geometry. In the milling machine, the rotary motion of the worktable on which the blank is supported and the movements of the drill bit which act to shape the blank are computer-controlled to exactly impart the desired geometry to the blank.  
         [0022]     Briefly stated, these objects are attained in a milling machine on whose rotary worktable is supported by a blank workpiece which is engaged by the bit of a drill bit unit mounted on an elevator. The elevator which acts to move the drill bit up and down along a vertical axis rides on a carriage movable along a horizontal track back and forth to shift the drill bit along a horizontal axis.  
         [0023]     The rotary worktable, the elevator and the carriage are driven by respective stepping motors whose incremental advances are controlled by a computer. Digitally stored in the database of the computer is data regarding the geometry of the half-sections of the eyeglass frame on which the accessory is to be hitched. The computer acts to precisely position the drill bit with respect to the blank as it is being rotated, so as to impart thereto the desired geometry. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     For a better understanding of the invention as well as other objects and features thereof, reference is made to the annexed drawings wherein:  
         [0025]      FIG. 1  illustrates a clip-on accessory in accordance with the invention adapted to hitch onto a pair of prescription eyeglasses;  
         [0026]      FIG. 2  separately shows one of the filter lenses included in the accessory;  
         [0027]      FIG. 3  is a perspective view of the milling machine in accordance with the invention for milling blanks to create the filter lenses of the clip-on accessory;  
         [0028]      FIG. 4  is a section taken through a transverse plane in the machine shown in  FIG. 3 ;  
         [0029]      FIG. 5  is a longitudinal section taken through a preferred embodiment of the drill bit unit to be included in the machine;  
         [0030]      FIG. 6  is a perspective view of a preferred embodiment of a worktable to be included in the machine;  
         [0031]      FIG. 7  illustrates an on-screen display in accordance with which a user may define an arbitrary lens geometry;  
         [0032]      FIGS. 8A and 8B  illustrate how the cutting of a lens may be shifted;  
         [0033]      FIG. 9  illustrates a block adapted to retain a blank, for example on a worktable of the machine illustrated in  FIG. 3 ;  
         [0034]      FIG. 10A  illustrates a block positioning device for use in accordance with the block illustrated in  FIG. 9 ; and  
         [0035]      FIG. 10B  illustrates a typical use of the block positioning device illustrated in  FIG. 10A . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     Clip-On Accessory:  FIG. 1  illustrates a pair of prescription eyeglasses for correcting visual defects in the eyes of the wearer, and it also shows a clip-on accessory in accordance with the invention which is to be hitched onto these eyeglasses to protect the eyes against harmful radiation.  
         [0037]     Included in these eyeglasses is a metal or plastic frame  10  formed by left and right half sections  10 L and  10 R joined together by a nosepiece NP. Mounted in the half sections of the frame are optical lenses  11 L and  11 R. Half sections  10 L and  10 R of frame  10  have a generally trapezoidal geometry, with rounded corners. The optical lenses mounted in the half sections are similarly shaped. Hinged to the half sections of the frame are temple pieces  12 L and  12 R.  
         [0038]     It is to be understood that the stylized frame  10  shown in  FIG. 1  is by way of example only and that whatever the actual geometry of the eyeglasses to be fitted with a clip-on accessory, the geometry of the accessory must substantially match that of the frame so that the attractiveness of the eyeglasses is not degraded by the accessory.  
         [0039]     As shown in  FIG. 1 , the clip-on accessory  13  is custom-made in the sense that it fits, as it were, like a glove on the frame of the prescription eyeglasses whose stylistic geometry it has copied. In the accessory, the geometry of filter lens  14 L and  14 R substantially matches that of the complementary half sections  10 L and  10 R of the eyeglasses frame  10 .  
         [0040]     When therefore these filter lenses overlie the optical lenses of the eyeglasses, they fully cover the half sections of the frame and there is no disparity in shape and size therebetween. Hence whatever design a designer gives to the frame of prescription eyeglasses, this design is preserved by the clip-on accessory hitched onto the frame.  
         [0041]     Filter lenses  14 L and  14 R of the accessory are bridged by a bridge piece  15  of a high-strength flexible metal, such as stainless steel. Piece  15  acts to position the filter lenses so that they lie in registration with the optical lenses of the eyeglasses.  
         [0042]     Filter lenses  14 L and  14 R are fabricated of high-strength, synthetic plastic material having a high index of transparency, such as a polyacrylic material. The filter lenses are tinted or otherwise treated to have the desired filtration characteristics so that they filter out or reduce the harmful radiation for which the accessory is designed. Thus if the accessory is intended to convert a pair of prescription eyeglasses to sunglasses, the plastic filter lenses may be smoked or tinted for this purpose.  
         [0043]     But for other forms of radiant energy, such as rays emanating from an arc welding device or from a laser beam instrument, the filtration characteristics must be appropriate to these rays. Or the filter lens may have optical properties which when combined with those of the optical lenses of the eyeglasses then produce a compound lens affording visual correction beyond that provided by the optical lenses alone.  
         [0044]     Milling Machine: The purpose of the milling machine illustrated in  FIGS. 3 and 4  is to shape under computer-control a pair of blanks formed of transparent synthetic plastic material to create a pair of filter lenses for a clip-on accessory. The shaping of the blanks must be such as to impart to the resultant filter lenses substantially the same geometry as that of the half-sections of the frame of the prescription glasses onto which the accessory is to be hitched so that the style of the custom-made accessory is compatible with that of the eyeglasses.  
         [0045]     The machine includes twin rotary worktable units  18  which support the blanks to be machined. These units are cantilevered from a vertical barrier wall  19  so that they are spaced apart at fixed and stable positions. Each unit  18  is provided with a rotary worktable  20  mounted above a gear train box  21  whose gears couple the worktable to a stepping motor  22  placed behind barrier wall  19 . The shaft  23  of stepping motor  22  passes through a port in wall  19  to engage gears  24  in gear box  21 , whose output shift  25  joins worktable  20  at its center.  
         [0046]     A stepping motor is powered by a train of dc voltage pulses which cause the motor shaft to advance incrementally one angular step per pulse in a clockwise or counterclockwise direction, depending on the polarity of the pulses. These pulses are delivered to stepping motor  22  by a computer C which by controlling the number of pulses fed to the motor and their polarity can precisely position the worktable and the blank thereon to set it to a desired angular position.  
         [0047]     Milling is carried out by a drill bit unit  26  cantilevered by an arm  27  from an elevator  28 . Drill bit unit  26  includes a drill bit  29  capable of cutting and shaping plastic material as well as drilling a hole therein. It is continuously rotated at high speed by a standard dc motor  30  coupled to the drill bit unit.  
         [0048]     It is to be noted that a unique feature of a computer-controlled milling machine in accordance with the invention is that its drill bit unit is capable of drilling, cutting, notching and engraving the blank being milled. In this way the blank is given a geometry matching that of the eyeglasses frame onto which the resultant filter lens is hitched, but the filter lens also has holes and notches by means of which clips can be anchored thereon. Engraving of the filter lens makes it possible to engrave therein a brand name or the name of the designer of the eyeglasses whose geometry is copied by the filter lens.  
         [0049]     Elevator  28  rides on a carriage  38  that is movable back and forth on a horizontal track  35  bridging a pair of vertical pillars  36  and  37  which are parallel to the front wall  19  of the machine and are joined thereto by horizontal beams  36 B and  37 B. Elevator  28  rides up and down carriage  38  along a vertical rack  32  attached to the front side of carriage  38 . Thus as the elevator travels up or down, it then shifts drill bit  29  of the drill bit unit  26  attached thereto along a vertical Y axis towards or away from the blank on the worktable.  
         [0050]     Elevator  28  is driven by a stepping motor  33  powered and controlled by a train of dc pulses issuing from computer C. The number of pulses applied to the stepping motor and their polarity determines the direction and the extent to which elevator  28  is shifted in the Y direction. Carriage  38  is driven back and forth on track  25  by a stepping motor  39  mounted on vertical pillar  37 , motor  39  turning a lead screw  40  which passes through threaded bores in the ends of the carriage. Stepping motor  39  is powered and controlled by a dc pulse train delivered thereto by computer C.  
         [0051]     Thus the following three positions are controlled by computer C. 
        I. The vertical position of drill bit  29  relative to the blank on the worktable, as determined by elevator  28  driven by stepping motor  28 .     II. The horizontal position of drill bit  29  relative to the blank, as determined by carriage  38  driven by stepping motor  39 .     III. The angular position of the blank relative to the drill bit, as determined by worktable  21  driven by stepping motor  22 .        
 
         [0055]     Computer C which delivers a train of power pulses to each of the three stepping motors, varies the number of pulses in each train and their polarity so as to coordinate their respective operations to cause the drill bit to shape the blank being worked on to produce a filter lens of the desired geometry.  
         [0056]     In order that the geometry of the filter lenses of the accessory match the geometry of the half-sections of the frame of the eyeglasses onto which the accessory is hitched, it is necessary to inform the computer of this geometry. This information is supplied to the computer by an electronic scanner S.  
         [0057]     Scanner S views the pair of prescription eyeglasses whose frame geometry is to be reproduced in a clip-on accessory, and it generates a digital image thereof. The digital image is processed in the computer to derive therefrom data regarding the predetermined geometry of the frame. By predetermined is meant the geometry of the frame given to it by its designer. This data is stored in the database of the computer memory which is then able to instruct the three stepping motors of the machine to coordinate their operations so as to give the blank being shaped the desired geometry.  
         [0058]     As an alternative to a scanner adapted to scan whatever prescription eyeglasses are brought in by a wearer to have a matching clip-on accessory made, one can store in the database of the computer the geometry of the various frames that are currently being marketed (altogether at least 500). When an individual comes in with his eyeglasses for which he wishes to obtain a clip-on accessory, the operator of the clip-on service can by looking at the frame of the eyeglasses and recognizing its style, can then extract from the database the appropriate data.  
         [0059]     To check on whether he has selected the right data, the operator can display on the monitor screen associated with the computer an image of the selected frame geometry, and can compare this image with the frame of the spectacles for which the clip-on accessory is intended.  
         [0060]     Alternatively, the digital image of the desired lens geometry may be input manually to the computer. According to one embodiment, illustrated in  FIG. 7 , a user is presented with an on-screen circle  100  and rectangle  102  centrally located therein. The circle  100  represents the perimeter of an uncut lens, and is thus the outer limit of the outline of a lens. The rectangle  102  represents the inner limit of the outside of the lens. (The lens outline thus must be entirely within the area  104  between the rectangle  102  and the circle  100 ). An input device is provided to allow the user to input a desired design  106  on the screen. The input device may be a mouse, touch screen, or any other known device.  
         [0061]     The computer may be adapted to compute an outline from the inputted design  106 . This computation may include smoothing and, in the event that the curve is not closed, closing the curve. The outline is editable, allowing a user to, inter alia, override any of the changes made by the computer to the design  106 . The computer may also be preloaded with outlines. In this way, a user may select one of many pre-drawn designs without having to input it manually. The computer also allows the user to mark locations  108  where holes are to be drilled by the machine. A hole may be marked coincident with the outline in order to indicate the location of a slot. Once all computations and editing has been completed, the computer coordinates shaping of the lens from a blank. A second lens may be cut which is a mirror image of the first so that an entire pair of eyeglasses or clip-ons may be assembled using the lenses.  
         [0062]     The user may also specify the horizontal and vertical offsets, if any, of the lens. This is especially useful when shaping prescription lenses. These values may be provided by an optometrist as P.D. and segH, respectively. As seen in  FIG. 8A , when there is no offset provided, the computer coordinates operations of the machine to shape a lens having a perimeter which is formed along line  120  of a blank  122 . The center  124  of the resulting lens is coincident with the optical axis  126  of the blank. As illustrated in  FIG. 8B , when an offset is provided, the cutting is shifted according to the horizontal and vertical offsets, as indicated by arrows  130   a  and  130   b , respectively. The computer coordinates operations of the machine to cut the lens having a perimeter which is formed along line  128 . The optical axis  126  of the resulting lens can thus be located non-coincidentally with its center  124 . This allows for all blanks to be secured to the worktable of the machine in the same position, without first determining the offset on the blank itself prior to shaping, as is typically done today.  
         [0063]     In order to place the blank on the worktable in the appropriate position, a block, generally indicated at  140 , is provided, as illustrated in  FIG. 9 . The block  140 , which may be single-use, comprises a top surface  142  and a bottom surface  144 . The top surface  142  is curved to match the curvature of the inner surface of a blank, and is provided with an adhesive. The adhesive should be selected such that it bonds the blank to the block during the shaping, preventing shifting, and is easily removable afterwards, preferably without leaving residue on the blank after removal.  
         [0064]     As illustrated in  FIG. 10A , a block positioning device, generally designated at  146 , is provided, comprising a first seat  148  and a second seat  150  on a first side  152  thereof. The first seat  148  is adapted to hold the blank, and the second seat  150 , centrally located with respect to the first seat, is adapted to slidingly receive the block  140 . The second seat  150  is preferably in the form of a through-going aperture shaped in accordance with the block. In use, the block  140  is placed within the second seat  150 , such that its top surface  142  is disposed toward the first side  152  of the block positioning device  146 . A blank  154  is placed in the first seat  148 , as illustrated in  FIG. 10B , and the user pushes the block  140  so that adhesive adheres thereto. A user may accomplish the pushing by inserting his finger through the second seat  150  so that it bears on the bottom surface  144  of the block  140 . The blank  154  may be placed on the worktable by mounting the block  140  thereto.  
         [0065]     In the computer-controlled machine in accordance with the invention&#39;s digital data yielded by a scanner regarding the geometry of the eyeglasses frame is stored in the database of the computer. This data instructs the milling machine so that the blank being shaped results in a filter lens whose geometry matches that of the frame. But it is also necessary to drill and notch the filter lens so that clips can be anchored therein to hitch the filter lens onto the frame. For this purpose the computer is provided with software that instructs the milling machine to drill and notch the filter lens at the proper positions.  
         [0066]     Worktable: In order for the worktable in the milling machine to precisely position a blank work piece supported on the table driven by a stepping motor, it is essential that when the rotary worktable is shifted to a particular angular position, that it then maintains this position. Should there be “play” in the drive mechanism (freedom to deviate slightly away from the set position) then this tolerance will adversely affect the shaping precision of the machine.  
         [0067]     To eliminate this play, the worktable  46  shown in  FIG. 6  is mounted on a shaft  47  driven by a stepping motor  48  to turn incrementally in the counterclockwise direction. Surrounding shaft  47  is a spiral spring  49  formed of spring metal, the inner end of the spring being joined to the shaft and the outer end to a fixed body  50  in the machine. Thus each time shaft  49  is caused to turn one step by stepping motor  48 , spiral spring  49  is wound to tighten it.  
         [0068]     As a consequence the shaft is subjected by the spring to a tension force that holds the turntable at its set position and prevents it from deviating therefrom. With successive steps of the motor which incrementally advance the worktable, the spring is further tightened until a point is reached at which it is fully tightened and therefore cannot continue to be tightened.  
         [0069]     In order to release the fully-tightened spring so that it can resume its function to prevent play of the worktable, there is fixedly mounted on shaft  47  a ring  51 . Projecting horizontally from this ring is a rod  52  which is joined to a vertical finger  53  connected to the end of a pointer arm  54  that is free to swing about shaft  47 .  
         [0070]     When the spring is being tightened this causes pointer arm  54  to swing in a counterclockwise direction until it strikes the actuator  54  of a spring-release mechanism which is actuated when the spiral spring is fully tightened and movement of the shaft is then arrested. The resultant unwinding of the spring makes it possible to resume the worktable operation.  
         [0071]     While there has been shown preferred embodiments of a milling machine in accordance with the invention, it is to be understood that many changes may be made therein without departing from the spirit of the invention.  
         [0072]     Thus when the prescription eyeglasses having a pair of optical lenses is “rimless” and therefore has no separate frame, the clip-on accessory having a pair of filter lenses hitches onto the borders of the optical lenses. These borders effectively function as the frame of the eyeglasses, and the geometry of these framing borders must be matched by the filter lenses of the accessory.