Patent Publication Number: US-2007111643-A1

Title: Apparatus and method for grinding workpieces

Description:
TECHNICAL FIELD  
      The present invention generally relates to apparatus and methods for grinding workpieces and, more particularly, to an apparatus and a method for cylindrically grinding workpieces.  
     BACKGROUND  
      Usually, optical elements such as camera lenses and spectacles are in used in cylindrical form. However, original optical workpieces (i.e. lens blanks) are most easily manufactured in the form of a square. Therefore, these original optical workpieces have to be cylindrically ground before use.  
      A typical example of a contemporary cylindrical grinding apparatus is a centraling apparatus. The centraling apparatus typically includes a pair of holders for holding the original workpiece, where each holder has a hollow chamber communicating with a surface of the holder. The holder can hold the workpiece on its surface by using an air pump creating suction in the hollow chamber, a grinding wheel is then used to cylindrically grind the workpiece. However, the centraling apparatus can only cylindrically grind one workpiece at a time.  
       FIG. 2  shows a method for cylindrically grinding more than one workpiece  50  at a time. The workpieces  50  are bonded together using ultraviolet adhesive. Then a grinding wheel  40  is used to grind the bonded workpieces  50  into a cylindrical shape. During the grinding process, the grinding wheel grinds the bonded workpieces  50  along an X direction and a Z direction. However, when grinding along the X direction, the grinding wheel needs to run along the X direction many times because the grinding wheel only contacts the workpieces over a small area.  
      Therefore, a method for cylindrically grinding workpieces which can overcome the above-described problems is desired.  
     SUMMARY  
      In one aspect, a method for grinding workpieces is provided. Firstly, a plurality of bonded workpieces are positioned. The bonded workpieces have a central axis. Secondly, a grinding wheel is placed near to the workpieces. The grinding wheel has a rotating axis perpendicular to the central axis. The rotating axis and the central axis are separated by a predetermined perpendicular distance. Thirdly, the bonded workpieces are rotated around the central axis. Finally, the grinding wheel is rotated around the rotating axis, whilst maintaining the predetermined distance between the rotating axis and the central axis, and moved in a direction parallel to the central axis to grind the workpieces.  
      In another aspect, an apparatus for grinding workpieces is provided. The apparatus includes a clamp mechanism, a grinding wheel, and a driving mechanism. The clamp mechanism is configured for holding a stack of workpieces in a manner that the workpieces are rotatable around a central axis. The grinding wheel has a rotating axis perpendicular to the central axis. The driving mechanism is connected to the grinding wheel for rotating the grinding wheel around the rotating axis and moving the grinding wheel in a direction parallel to the central axis at the same time.  
      Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the method for cylindrically grinding workpieces can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present method for cylindrically grinding workpieces. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a schematic view of a method for cylindrically grinding workpieces in accordance with a preferred embodiment; and  
       FIG. 2  is a schematic view of a method for cylindrically grinding workpieces from the related art. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT  
      Referring to  FIG. 1 , in a preferred embodiment, a grinding wheel  10  and two clamps  12  are used for cylindrically grinding workpieces  18 . The clamps  12  are used for holding the workpieces  18 , and the grinding wheel  10  is used for grinding the workpieces  18 . The grinding wheel  10  is connected to a driving mechanism  102  for rotating and moving the grinding wheel  10 . One of the clamps  12  is connected to a rotating device  14  for rotating the clamps  12  and the workpieces  18 .  
      The workpieces  18  can be optical elements having a non-cylindrical shape. In this exemplary embodiment, the workpieces  18  are in substantially square form. The workpieces  18  can be bonded together using hydrolysable ultraviolet adhesive. The bonded workpieces  18  have a central axis  181 , and the bonded workpieces  18  can be rotated using the rotating device  14 . In this embodiment, the rotating device  14  can be a rotary motor.  
      In this embodiment, the grinding wheel  10  is cylindrical in shape, and has a radius r. The grinding wheel  10  has a rotating axis  100  perpendicular to the central axis  181  of the workpieces  18 , and the grinding wheel  10  can be rotated around the rotating axis  100  by the driving mechanism  102 . In this embodiment, the driving mechanism  102  is a motor.  
      Referring to  FIG. 1 , an exemplary method for cylindrically grinding workpieces  18  includes the steps of 
          (1) a stack of workpieces  18  are bonded together using hydrolysable ultraviolet adhesive;     (2) the bonded workpieces  18  are held in the clamps  12 , and the bonded workpieces  18  have a central axis  181 ;     (3) the grinding wheel  10  is placed near to the bonded workpieces  18 , the rotating axis  100  is perpendicular to the central axis  181 , and the rotating axis  100  and the central axis  181  are separated by a predetermined perpendicular distance L;     (4) the bonded workpieces  18  are rotated around the central axis  181  by the rotating device  14 ;     (5) maintaining the predetermined distance L, the grinding wheel  10  is rotationally moved along a moving path  101  parallel to the central axis  181  to grind the workpieces  18  into cylindrical shape; and,     (6) the cylinder shape workpieces  18  are placed in a water container, and the hydrolysable ultraviolet adhesive is removed using a ultrasonic device so as to obtain a plurality of desired workpieces.        

      In step (5), the cylinder shape workpieces  18  have a predetermined radius R. The predetermined distance L is equal to the radius r of the grinding wheel  10  plus the radius R of the cylindrical workpieces  18 . Understandably, the step (4) can be performed either before or after step (3).  
      It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples here before described merely being preferred or exemplary embodiments of the invention.