Abstract:
Precision polishing equipment polishes a general surface, such as an aspheric optical surface. A polishing element is rotatably mounted in a frame of the equipment. Polishing element has a compliant polishing member fixedly mounted to a substantially rigid support member. Compliant polishing member has plurality of spaced polishing portions for engaging the surface to be polished and trapping polishing fluid between the interface of the surface to be polished and nearest polishing portion in contact with the surface. Important advantages derived from the polishing equipment of the invention are that it can efficiently polish a general surface, such as an aspheric optical surface, and it enables the polishing fluid to evenly flow across the surface to be polished.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is related to U.S. Ser. No. 10/645,692 filed Aug. 21, 2003 of Randolph C. Brost, entitled “Compliant Polishing Element And Method Of Manufacturing The Same”, Atty. Docket No. 85078/CEB. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates generally to the field of precision surface polishing, and in particular to polishing of general surfaces. More specifically, the invention relates to a tool for polishing precision surfaces.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is well known in the art that precision surface polishing is often performed by large pads that execute planar or spherical motions relative to the surface to be polished. These large pads are either flat or spherical, depending on the shape of the surface to be polished. Because the pad shape and motion both match the surface, a large pad can contact the surface over a large area, and repetitive polishing motions can produce a precise surface by averaging effects.  
         [0004]     However, for polishing general surfaces, such as aspheric optical surfaces, existing polishing devices and systems have proven woefully inadequate. For these surfaces, the contact between the polishing tool and the surface must be much smaller than the pads used for planar or spherical surfaces, because the local radius of curvature varies across the surface. Further, polishing pads that are entirely sufficient for polishing planar or spherical surfaces are not sufficiently compliant to accommodate the variations in curvature radius inherent in aspheric surfaces to be polished.  
         [0005]     While there have been numerous attempts in the prior art to address the challenges presented when polishing aspheric surfaces, there has been limited success in overcoming the aforementioned problems. As an example, in one known device for polishing an aspheric surface, a small contact patch is used to contact the surface. In another instance, a large wheel device is used that achieves a small contact patch by exploiting magneto-rheological fluids. Further, other polishing systems that have attempted to solve the aforementioned problem have used a convex pad to polish the surface, sometimes with a pressing motion. One shortcoming with all of the above-mentioned polishing systems is that the polishing tool is large relative to the contact patch, which makes it impossible to use for surfaces with small, deep concavities. There is one prior art attempt that seeks to overcome this latter problem disclosed in co-pending U.S. patent application Ser. No. 10/318,787, filed Dec. 13, 2002 by Stephen C. Meissner, titled “Sub-Aperture Compliant Toroidal Polishing Element,” hereby incorporated herein by reference. The compliant polishing tool in U.S. Ser. No. 10/318,787 uses a very small toroidal compliant tool to achieve a small polishing contact patch that can reach into small concavities.  
         [0006]     One problem that is known to occur with the above and all of the existing compliant polishing tools is that a deficiency in polishing fluid coverage on the surface to be polished results as contact pressure is increased between the polishing member and the surface. It is our experience that this deficiency arises because polishing fluid is forced away from the center of the contact region of the polishing member and surface to be polished, leaving a region deficient in fluid coverage for effective polishing. As a result, it is well known that prior art polishing devices limit the contact pressures that may be applied by the polishing member on the surface to be polished, which in turn limits material removal rates. Consequently these compliant tools cannot achieve the polishing productivity and efficiency that might be attained if positive fluid flow throughout the contact was assured.  
         [0007]     Therefore, there remains a need for a compliant polishing element for polishing surfaces, particularly aspheric surfaces, that provides a small contact patch that can reach into deep concavities, while maintaining fluid flow throughout the contact even while significant contact pressure is applied by the polishing member.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, precision surface polishing equipment has a rigid frame and a polishing element mounted for rotation in the rigid frame. The polishing element has a substantially rigid support member cooperatively associated with a compliant polishing member fixedly attached thereto. The compliant polishing member has a plurality of spaced polishing portions for engaging a surface to be polished, each one of the plurality of spaced polishing portions being projected radially outwardly from the substantially rigid support member. Nearest adjacent of the plurality of spaced polishing portions form a fluid transport region therebetween when the compliant polishing member is in compressive contact with the surface to be polished. Means associated with the rigid frame is provided for rotating the polishing element. Further, a polishing fluid is applied to the surface with an appropriate means such as a reservoir connected to a fluid nozzle. The layer of polishing fluid is substantially evenly applied onto the surface to be polished when disposed in the fluid transport region of the polishing element.  
         [0009]     The present invention has numerous advantages over prior art developments. For instance, the polishing device can polish aspheric surfaces. Moreover, the polishing device of the invention is not complicated to manufacture and is easy to use. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein:  
         [0011]      FIG. 1A  is an elevated, slightly tilted side view of the polishing device of the invention;  
         [0012]      FIG. 1B  is an elevated side view of the polishing device of  FIG. 1A  partially sectioned and exploded to show the lobes of the polishing member;  
         [0013]      FIG. 2  is a schematic of the polishing tool of the invention during polishing;  
         [0014]      FIG. 3A  is an elevated side view of an alternative embodiment of the invention;  
         [0015]      FIG. 3B  is an elevated side view of the embodiment of  FIG. 3A  partially sectioned and exploded to show the features of the polishing member;  
         [0016]      FIG. 4  is an enlarged perspective view of the compliant polishing member used in the embodiment of  FIGS. 3A and 3B ;  
         [0017]      FIGS. 5A-5F  are top plan views of several exemplary compliant polishing members used in the invention;  
         [0018]      FIG. 6A  is an elevated side view of another alternative embodiment of the invention;  
         [0019]      FIG. 6B  is an elevated side view of the embodiment of  FIG. 6A  partially sectioned and exploded to show the polishing member;  
         [0020]      FIG. 7  is an enlarged perspective view of the compliant pad illustrated in  FIGS. 6A and 6B ;  
         [0021]      FIG. 8A  is an elevated side view of yet another embodiment of the invention;  
         [0022]      FIG. 8B  is the embodiment of  FIG. 8A  partially sectioned and exploded to show the polishing member;  
         [0023]      FIG. 9  is an enlarged perspective view of the compliant pad of the embodiment illustrated in  FIGS. 8A and 8B ;  
         [0024]      FIG. 10  is a perspective view of a polishing tool containing the polishing element of the invention; and,  
         [0025]      FIG. 11  is an elevated side view of the polishing tool of  FIG. 9  in service polishing a surface; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     Turning now to the drawings, and more particularly to  FIGS. 1A and 1B , polishing element  10  of the first embodiment of the invention is illustrated. According to  FIGS. 1A and 1B , polishing element  10  has a substantially rigid support member  12  with an outer perimeter  14  for cooperatively associating with a tool, such as the exemplary rotary tool shown in  FIG. 10 . The outer perimeter  14  terminates at one end with a mounting surface  16  provided for affixing a compliant polishing member or pad  18 . Compliant polishing member  18  may be affixed to mounting surface  16  in any number of ways including gluing, friction or interference fit, or with a screw. Moreover, the compliant polishing member  18  may be molded to the mounting surface  16 .  
         [0027]     Referring to  FIGS. 1A, 1B , and  2 , polishing tool  26  comprises a polishing fluid applicator or nozzle  23  and the polishing element  10  (compliant polishing member  18  only illustrated) in a precision surface polishing application, for example, polishing an aspheric optical surface  22 . Compliant polishing member  18  of the invention has a plurality of regularly spaced polishing portions or lobes  20  for spreading polishing fluid  21  across the surface  22  to be polished. The recess  24  between nearest adjacent lobes  20  enables a predetermined amount of polishing fluid  21  to be spread in a predictable manner across the surface  22  to be polished. During a precision polishing application, the polishing element  10  is structurally mounted into a spindle (not shown) of a rotary device ( FIG. 11 ) via the substantially rigid support member  12  ( FIGS. 1A and 1B ). The polishing element  10  is rotated while in compressive contact with the surface  22  to be polished. A polishing fluid, such as a slurry of abrasive particles, is disposed, typically via nozzle  23 , in an interfacial area between adjacent lobes  20  of the compliant polishing element  10  and the surface  22  to be polished. As the polishing element  10  is rotated by the rotary device, the plurality of spaced polishing portions or lobes  20  traps polishing fluid  21  between the surface  22  to be polished and the nearest of the lobes  20 . This action forces the polishing fluid  21  across the surface  22  to be polished. In the process, it also prevents polishing fluid starvation from any area on the surface  22  to be polished.  
         [0028]     Referring to  FIGS. 3A, 3B , and  4 , in a second embodiment of the invention, polishing element  30  has a substantially rigid support member  33  and a compliant polishing member  35  mounted on an end portion (not shown) of the support member  33 . Compliant polishing member  35  has a plurality of spaced lobes  37  each being connected to a nearest adjacent lobe  37  by a recess  39 . A continuous groove  41  passes through each of the lobes  37  about the circumference of the compliant polishing member  35 . A portion of each lobe  37  separated by the groove  41  is directed inwardly towards the groove  41 . Groove  41  prevents polishing fluid  21  from escaping from between the lobes  37  and surface to be polished  22  (shown in  FIG. 2 ) as polishing element  30  rotates. According to FIG.  4 , continuous groove  41  is clearly shown in a close-up view of the polishing element  30 .  
         [0029]     Referring now to  FIGS. 5A-5F , illustrated are several substantially star-shaped configurations  40 ,  50 ,  60 ,  70 ,  80 ,  90  for compliant polishing member  18  or pads. Each of these substantially star-shaped configurations  40 ,  50 ,  60 ,  70 ,  80 ,  90  may be used in the polishing element  10  of the invention to produce substantially the same result. More particularly, each of the substantially star-shaped configurations  40 ,  50 ,  60 ,  70 ,  80 ,  90  produces similar favorable fluid dynamics at the interface of the surface  22  and compliant polishing member  18 . According to  FIG. 5A , configuration  40  has typically six lobes  42  having rounded peaks  44  separated by slightly arcuate recesses  46  which form a slightly arcuate angled lobe  42 . According to  FIG. 5B , configuration  50  has a plurality of lobes  52  (typically six) each having a relatively flat and substantially straight peak  54  separated from the nearest adjacent lobe  52  by a slightly curved recess  56  to form a flat, substantially straight lobe  52 . According to  FIG. 5C , configuration  60  has a plurality of lobes  62  (typically six) each having a relatively narrow and slightly rounded peak  64  separated by a slightly curved recess  66  to form a substantially straight lobe  62 . According to  FIG. 5D , configuration  70  has a plurality of lobes  72  (typically six) each having a relatively narrow and round peak  74  separated from the nearest adjacent lobe  72  by substantially curved recess  76  to form a narrow, substantially arcuate shaped lobe  72 . According to  FIG. 5E , configuration  80  has a plurality of lobes  82  each having a narrow rounded peak  84  separated from the nearest adjacent peak  84  by substantially wide, arcuate shaped recess  86  to form a substantially wide arcuate lobe  82 . Finally, according to  FIG. 5F , configuration  90  has a plurality of lobes  92  each having a narrow, very round peak  94  separated from the nearest adjacent narrow, very round peak  94  by a very arcuate shaped recess  96  to form a narrow, very arcuate lobe  92 .  
         [0030]     Turning now to  FIGS. 6A, 6B , and  7 , a third embodiment of the compliant polishing element  100  is illustrated. According of  FIGS. 6A, 6B , and  7 , compliant polishing element  100  has a substantially disk-shaped polishing member  102  supported on substantially rigid support  104 . A central opening  106  passes through the compliant polishing member  102  for locating onto the substantially rigid support  104 . As indicated above, substantially rigid support  104  cooperates with a rotary tool for polishing a work piece (Shown in  FIG. 10 ). In this embodiment, compliant polishing element  100  is characterized by a plurality of spaced depressions  108  arranged in the circumference  110  of the compliant polishing member  102 . the portions of the circumference  110  between the depressions  108  form the compliant polishing portions  112 . As in the previous embodiments, the spaced depressions  108  trap the polishing fluid between the surface  22  to be polished and the compliant polishing member  102  during polishing. Further, spaced depressions  108  assure that the polishing fluid will spread across the surface without leaving voids. Depressions  108  may be formed in the circumference of compliant polishing member  102  in a number of ways, including cutting or forming during a molding process.  
         [0031]     Referring now to  FIGS. 8A, 8B , and  9 , a fourth embodiment of the compliant polishing element  120  is illustrated. In this embodiment, the compliant polishing element  120  has a substantially rigid support  122  and a compliant polishing member  124  attached to one end of the rigid support  122 . Important to the invention, compliant polishing member  124  has a plurality of spaced compliant polishing portions  126  each having a surface shape generally in the form of a torus, as best seen in  FIG. 9 . The compliant polishing portions surround recessed portions  128 . As in previous embodiments, the substantially torus-shaped compliant polishing member  124  traps polishing fluid between the interface of the surface  22  to be polished and the recessed portions  128  of the compliant polishing member  124 . Compliant polishing member  124  further provides means for distributing the polishing fluid across the surface area of the surface  22  to be polished.  
         [0032]     Referring now to  FIGS. 10 and 11 , precision surface polishing equipment, such as tool,  200  for precision polishing a general surface, for instance an aspheric optical surface, is shown. In  FIG. 11 , a partial schematic of polishing element  220  of polishing equipment  200  is shown polishing an aspheric surface  240  ( FIG. 11 ). According to  FIG. 10 , polishing equipment  200  comprises a movable work piece holder  210  for precise engagement by compliant polishing member  230  of polishing element  220 . Polishing element  220  comprises compliant polishing member  230  affixed to substantially rigid support member or frame  250 . In the preferred embodiment, polishing element  220  is slightly angled from the polishing surface normal ( FIG. 11 ). Means, such as a nozzle (described above) is provided for applying a layer of polishing fluid onto the surface to be polished. The polishing fluid is not shown. This configuration allows polishing of flat surfaces and concavities using a uniform contact condition.  
         [0033]     The invention has been described with reference to a preferred embodiment. However, it will be appreciated that variations and modifications can be effected by a person of ordinary skill in the art without departing from the scope of the invention.  
       Parts List  
       [0000]    
       
           10  first embodiment of polishing element  
           12  substantially rigid support member  
           14  outer perimeter of support member  12   
           16  mounting surface  
           18  compliant polishing member of first embodiment  
           20  lobes  
           21  polishing fluid  
           22  surface to be polished  
           23  nozzle  
           24  recess between nearest adjacent lobes  20   
           26  partial polishing tool  
           30  second embodiment of polishing element  
           33  substantially rigid support member of second embodiment  
           35  compliant polishing member of second embodiment  
           37  lobes of second embodiment  
           39  recess separating nearest adjacent lobes  37   
           40  first configuration of compliant polishing member  18   
           41  continuous groove  
           42  lobes of first configuration  
           44  rounded peaks of lobes  42   
           46  slightly arcuate recess  
           50  second configuration of compliant polishing member  18   
           52  lobes of second configuration  
           54  substantially straight peak of lobe  52   
           56  slightly curved recesses between nearest adjacent lobes  52   
           62  third configuration of compliant polishing member  18   
           64  lobes of third configuration  
           66  slightly rounded peak of lobes  62   
           70  slightly curved recess between nearest adjacent lobes  62   
           72  fourth configuration of compliant polishing member  18   
           72  lobes of fourth configuration  
           74  round peak of lobes  72   
           76  substantially curved recesses between nearest adjacent lobes  72   
           80  fifth configuration of compliant polishing member  18   
           82  lobes of fifth configurations  
           84  narrow rounded peaks of lobes  82   
           86  substantially wide, arcuate shaped recess between nearest adjacent lobes  
           90  sixth configuration of compliant polishing member  18   
           92  lobes of sixth configuration  
           94  very round peaks of lobes  92   
           96  very arcuate shaped recess between nearest adjacent lobes  92   
           100  third embodiment of compliant polishing element  
           102  disk shaped polishing member of third embodiment  
           104  rigid support of third embodiment  
           106  central opening passing through member  102   
           108  spaced depressions in compliant polishing member  102   
           110  circumference of compliant polishing member  102   
           112  compliant polishing portions of polishing member  102   
           120  fourth embodiment of compliant polishing element  
           122  rigid support of compliant polishing element  120   
           124  compliant polishing member of fourth embodiment  
           126  spaced polishing portions  
           128  recessed portion  
           200  tool for precision polishing  
           210  movable work piece holder  
           220  polishing element of tool  200   
           230  compliant polishing member of element  220   
           240  aspheric surface  
           250  substantially rigid support member of element  220