Abstract:
An apparatus for cylindrically grinding workpieces includes a first holding tool ( 100 ) for positioning pre-grinding workpieces ( 40 ) and a second holding tool ( 200 ) for positioning partially ground workpieces (i.e. workpieces which have been ground on one side only). The first holding tool ( 100 ) defines a first groove ( 226 ) for containing the pre-grinding workpieces to be partially ground and the second bonding defines a second groove ( 322 ) for containing the partially ground workpieces. At least one first resisting member ( 26 ) and at least one first back plate ( 24 ) detachably connect with the at least one first holding member ( 22 ), and thus making up the first holing tool ( 100 ). At least one second resisting member ( 36 ) and a at least one second back plate ( 34 ) detachably connect at least one second holding member ( 36 ), and thus making up the second holding tool ( 100 ). The present invention also provides a process for cylindrically grinding workpieces.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to cylindrical grinding apparatuses and processes and, more particularly, to a holder for holding workpieces during a cylindrical grinding process and a holding method for such a process. 
   DESCRIPTION OF RELATED ART 
   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 centering apparatus. The centering 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 evacuating the hollow chamber, and a grinding wheel is then used to cylindrically grind the workpiece. However, the centering apparatus can only cylindrically grind one workpiece at a time. 
     FIGS. 7-8  show an apparatus for cylindrically grinding more than one workpiece at a time. The apparatus includes a first holding tool  12  and a second holding tool  14 . The first holding tool  12  defines a holding groove  122 , and the second holding tool  14  defines a semicircular groove  142 . The holding groove  122  and the semicircular groove  142  are both for securing the workpieces  16  in the holding tools  12 ,  14 . In use, firstly, a plurality of workpieces  16  are placed in the holding groove  122  of the first holding tool  12 . Secondly, the workpieces  16  are bonded together using an adhesive. Thirdly, a grinding wheel is used to grind a portion of the workpieces  16  projecting out of the holding groove  122  into a semicircular shape. Fourthly, the semicircular portion  162  of the workpieces  16  is transferred to the semicircular groove  142  of the second holding tool  14 . Fifthly, the other portion of the workpieces  16  is also ground into a semicircular shape using the grinding wheel. The final result being that the workpieces  16  are ground to a cylindrical shape. 
   When transferring the workpieces  16  from the first holding tool  12  to the second holding tool  14 , the adhesive should be dissolved so that the workpieces  16  can be taken out of the first holding tool  12 . However, the workpieces  16  will not be held compactly in the second holding tool  14  and may become disarrayed whilst the adhesive is being dissolved. 
   Therefore, an apparatus and a process for cylindrically grinding workpieces which can easily and compactly transfer the workpieces is desired. 
   SUMMARY OF THE INVENTION 
   In one aspect, an apparatus for cylindrically grinding workpieces includes a first holding tool for positioning pre-grinding workpieces and a second holding tool for positioning partially ground workpieces (i.e. workpieces which have been ground on one side only). The first holding tool defines a first groove for containing the pre-grinding workpieces to be partially ground and the second bonding defines a second groove for containing the partially ground workpieces. A first resisting member and a first back plate detachably connect with at least one first holding member, and thus making up the first holding tool. A second resisting member and a second back plate detachably connect at least one second holding member, and thus make up the second holing tool. 
   In another aspect, a process for grinding workpieces can be used wherein a plurality of pre-grinding workpieces are positioned in a first groove of a first holding tool with a first portion of the pre-grinding workpieces projecting out of the first groove. The first portion of the pre-grinding workpieces is partially ground into a first predetermined shape. A second holding tool is provided, the second holding tool defining a second groove. The first holding tool is detached, whilst the second holding tool is then placed on the partially ground workpieces with the first portion in the second groove. The parts of the second holding tool are fastened. The second holding tool is then reversed, whilst a second portion of the workpieces projects out of the second groove, this second portion is then ground into a second predetermined shape thus completing the grinding process. 
   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 apparatus 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 apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is a schematic view of a first holding tool of an apparatus for cylindrically grinding workpieces in accordance with a first preferred embodiment; 
       FIG. 2  is a schematic view of a second holding tool of the apparatus for cylindrically grinding workpieces in accordance with the first preferred embodiment; 
       FIG. 3  is a schematic view of a step of the process for cylindrically grinding workpieces using the apparatus of  FIG. 1 ; 
       FIG. 4  is a schematic view of another step subsequent to the step in  FIG. 3 ; 
       FIG. 5  is a schematic view of a further step subsequent to the step in  FIG. 4 ; 
       FIG. 6  is a schematic view of a first holding tool of an apparatus for cylindrically grinding workpieces in accordance with a second preferred embodiment; 
       FIG. 7  is a schematic view of a first holding tool of a typical apparatus for cylindrically grinding workpieces; and 
       FIG. 8  is a schematic view of a second holding tool of the apparatus in  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-2 , an apparatus for cylindrically grinding workpieces  40  according to a first preferred embodiment, includes a first holding tool  100 , a second holding tool  200 , and a grinding wheel  300 . The holding tools  100 ,  200  are configured for holding workpieces  40 . 
   The first holding tool  100  includes two first holding members  22 , a first back plate  24 , two first resisting members  26 , and two first fixing members  28 . 
   Each first holding member  22  is rectangular in shape, and has two opposite side surfaces  222 , and a working surface  224  between the side surfaces  222 . Each first holding member  22  defines a through-hole  225  extending through the side surfaces  222 . The working surface  224  defines a first groove  226  for containing pre-grinding workpieces  40 . The pre-grinding workpieces  40  can be optical elements having a non-cylindrical shape. In this preferred embodiment, the workpieces  40  are substantially square-shaped. Therefore, the first groove  226  is configured to have a V-shaped cross section along a traverse direction, for compliantly receiving the pre-grinding workpieces  40  therein. The pre-grinding workpieces  40  are partially ground on the first groove  226  and centers of the workpieces  40  are higher than the working surface  224 , thus the grinding wheel  300  cannot touch the working surface  224  when the grinding wheel  300  grinds the workpieces  40 . Understandably, the cross section along a traverse direction of the first groove  226  may be of other shape depending on the shape of the pre-grinding workpieces  40 . 
   The first back plate  24 , which is substantially rectangular shaped, defines two spaced bores  242 . The bores  242  correspond to the through-holes  225  of the first holding members  22 . The first back plate  24  has a top surface  243  paralleling the axes of the bores  242 . Two protruding columns  244  are formed on the top surface  243 . A cross-section along a traverse direction of the protruding column  244  is semicircular shape, and a radius of the protruding column is same as that of the finished product, corresponding to the shape of the first groove  226 . Each protruding column  244  has an end surface  246  which is used to resist the workpieces  40 . The end surface  246  is flat enough to avoid harming the workpieces  40 . 
   The first resisting members  26  include a base plate  262 , and a column  264  extending from one surface of the base plate  262 . A diameter and a length of the column  264  are similar to those of the through-hole  225  of the first holding member  22 . A screw hole  269  is defined at the end of the column  264 . The screw hole  269  is coaxial to the column  264 . The cross section shape along a traverse direction of protruding column  266  is the same as the protruding column  244  of the first back plate  24 . The extension direction of the protruding column  266  is the same as that of the column  264 . Each protruding column  266  has a end surface  268  which is used to resist the workpieces  40 . 
   The fixing member  28 , includes a head portion  282 , a screw portion  284 , and a connecting portion  286 . The connecting portion  286  connects the head portion  282  and the screw portion  284 . A diameter of the head portion  282  is larger than that of the connecting portion  286 , thus the diameter of the connecting portion  286  is larger than that of the screw portion  284 . 
   The configuration of the second holding tool  200  is almost the same as that of the first holding tool  100 . The second holding tool  200  includes two second holding members  32 , a second back plate  34 , two second resisting members  36 , and two second fixing members  38 . The back plate  34  includes two protruding columns  342  having an end surface  344 . Each resisting member  36  includes a protruding column  362  having an end surface  364 . Compared with the first holding tool  100 , the second holding tool  200  has some differences, which are as follows: each holding member  32  defines a second groove  322  having a semicircular shaped cross section along a traverse direction; A radius of the second groove  322  is same as the finished product. 
   In assembling the first holding tool  100 , the first holding members  22  are joined together with the first grooves  226  facing upward. The protruding columns  266  face upward, and each column  264  is inserted through the through-holes  225 . The first back plate  24  abuts against the side surfaces  222  of the first holding members  22 . Finally, each first fixing member  28  is inserted through the bores  242  and the screw portion  284  is screwed into the screw holes  269  of the columns  264 . 
   The process of assembling the second holding tool  200  is the same as that of the first holding tool  100 . 
   Referring to  FIGS. 3-5 , an exemplary process for cylindrically grinding workpieces  40  includes the steps of: 
   (1) A stack of workpieces  40  (i.e. pre-grinding workpieces) are placed in the first groove  226  of the first holding tool  100 . The first fixing members  28  are screwed down and the pre-grinding workpieces  40  are clamped by the protruding columns  244 ,  266 . A first portion  42  of the pre-grinding workpieces  40  projects out of the first grooves  226 .
 
(2) The first portion  42  of the pre-grinding workpieces  40  is partially ground to a semicircular shape.
 
(3) The first fixing members  28  of the first holding tool  100  are released so that the first back plate  24  and the first resisting members  26  are detached from the first holding tool  100 . The second holding tool  200  is placed on the partially ground workpieces  40  with the first portion  41  in the second groove  322 . The second fixing members  38  are screwed down and the partially ground workpieces  40  are clamped.
 
(4) The holding tool  200  is reversed and a second portion  44  of the partially ground workpieces  40  projects out of the second grooves  322 .
 
(5) The second portion  42  of the workpieces  40  is ground to a semicircular shape. Thus a plurality of cylindrical workpieces  40  are obtained.
 
   It is believed that the cross section along a traverse direction of the first grooves  226  can be of other shape, for example, a square groove can be defined under the original first groove  226 . The first grooves  226  and the second grooves  322  may extend to the end surfaces of the holding members  22 ,  32 . 
   It is believed that the number of the holding members  22 ,  32  can be changed and the number of the corresponding resisting members  26 ,  36  can be changed accordingly; the first resisting members  26  of the first holding tool  100  can be integrally formed and the second resisting members  36  of the second holding tool  200  can also be integrally formed. 
   The process can easily and compactly transfer workpieces  40  from the first grooves  226  to the second groove  322  using the resisting members  26 ,  36  and the back plate  24 ,  34  which can promote the working efficiency of the cylindrical process. Also the process does not use adhesive, and thus does not require water or other solvents to dissolve the adhesive, so the workpieces  40  can avoid becoming disarrayed. 
   Referring to  FIG. 6 , an apparatus for cylindrically grinding workpieces according to a second preferred embodiment includes a first holding tool  100  and a second holding tool  200 . The first holding tool  100  includes one holding member  62 , two back plates  64 , two resisting members  66 , and two fixing members  68 . The holding member  62  defines two through-holes  622  and two grooves  624  with a V-shaped cross section along a traverse direction. Each back plate  64  defines a bore. The second holding tool is same as the first holding tool  100  except for the cross section shape along a traverse direction of the grooves  624  being semicircular. 
   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.