Patent Publication Number: US-2007122520-A1

Title: Clamping device

Description:
1. FIELD OF THE INVENTION  
      The present invention relates to clamping devices, and more particularly to a clamping device for clamping a lens preform.  
     2. DESCRIPTION OF RELATED ART  
      Nowadays, plastic lenses are widely used in consumer electronics products, for example, digital cameras, as they are cheap and simple to produce.  
      A method for producing plastic lenses generally includes the following steps: forming a lens preform using an injection molding apparatus; and cutting the lens preform and obtaining a number of lenses. Referring to  FIG. 10 , a lens preform  10  is shown. The lens preform  10  includes four lenses  12 , a sprue forming portion  14 , and four runner forming portions  16 . The lenses  12  are each connected to the sprue forming portion  14  by the runner forming portions  16 . The lenses  12  can be cut away from the runner forming portions  16 .  
      In the cutting process, a clamping device is provided to hold the lens preform  10 . Referring to  FIG. 11 , a typical clamping device  22  is shown. The clamping device  22  includes two grooves  221  and  222  at the top thereof. The lens preform  10  is carried to the space above the clamping device  22  and dropped to the clamping device  22  in such a manner that the runner portions  16  are engaged in the grooves  221  and  222 . Then the cutting takes place.  
      However, it is difficult to drop the lens preform  10  into the clamping device  22  precisely. That is, the runner portions  16  may not easily engage in the grooves  221  and  222 . In this case, the lenses  12  cannot be properly cut from the lens preform  10 .  
      It is therefore desirable to find a new clamping device which can overcome the above mentioned problems.  
     SUMMARY OF THE INVENTION  
      In a preferred embodiment, a clamping device for clamping a lens preform includes a base, at least two clamping portions, and a driving device. The base includes a flat bottom. The clamping portions are arranged on the bottom. Each of the clamping portions defines a recess at a top thereof. Each pair of adjacent recesses cooperatively form a space when the two adjacent clamping portions are in contact with each other. The clamping portions are reciprocally moveable on the bottom between a holding position and a releasing position. The driving device is configured for driving the clamping portions to move between the holding position and the releasing position. The clamping portions are moved towards each other to reach the holding position in a manner such that the lens preform is held by the clamping portions. The clamping portions are moved towards each other to reach the releasing position in a manner such that the lens preform is released from the clamping portions.  
      Other advantages and novel features will become more apparent from the following detailed description of the present clamping device, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the clamping device 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 invention.  
       FIG. 1  is a schematic isometric view of a clamping device in accordance with a first embodiment;  
       FIG. 2  is a schematic top view of a base of the clamping device of  FIG. 1 ;  
       FIG. 3  is a cross-sectional view of the clamping device of  FIG. 1 , showing clamping portions thereof are in a clamping position;  
       FIG. 4  is a cross-sectional view of the clamping device of  FIG. 1 , showing clamping portions thereof are in a releasing position;  
       FIG. 5  is a schematic isometric view of the clamping device of  FIG. 1 , together with a lens preform clamped therein;  
       FIG. 6  is a cross-sectional view of the clamping device and the lens perform of  FIG. 5 ;  
       FIG. 7  is a cross-sectional view of the clamping device of  FIG. 1 , showing a lens preform is dropped into the clamping device;  
       FIG. 8  is a schematic isometric view of a clamping device, in accordance with a second embodiment;  
       FIG. 9  is a schematic isometric view of a clamping device of  FIG. 8 , together with a lens preform clamped therein;  
       FIG. 10  is a schematic isometric view of a typical lens perform;  
       FIG. 11  is a schematic isometric view of a typical clamping device together with the lens perform clamped therein.  
    
    
      Corresponding reference characters indicate corresponding parts throughout the drawing. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
     DETAILED DESCRIPTION OF THE INVENTION  
      Reference will now be made to the drawings to describe the preferred embodiments of the present clamping device in detail.  
      Referring to  FIGS. 1 and 2 , a clamping device  30  for clamping a lens preform  40  (referring to  FIG. 5 ) is shown in accordance with a first embodiment. The clamping device  30  includes a base  32 , two clamping portions  34  and a driving device  36 .  
      The base  32  includes a flat circular bottom  322  and a peripheral side wall  324  extending from the bottom  322 . The bottom  322  defines two slots  328  therein. The slots  328  are oriented radially. The side wall  324  is for further confining the clamping portions  34  to the base when the clamping portions  34  move outwards.  
      The clamping portions  34  are arranged within the base  32  on the bottom  322 . Each clamping portion  34  is a half-cylinder with a recess defined therein at a top thereof. The recesses cooperatively form a space  342  when the clamping portions  34  are in contact with each other. The clamping portions  34  are reciprocally movable on the bottom  322  between a holding position and a releasing position. The clamping portions  34  are moved towards each other to reach the holding position in a manner such that the lens preform  40  is held by the clamping portions  34 . The clamping portions  34  are moved towards each other to reach the releasing position in a manner such that the lens preform  40  is released from the clamping portions  34 .  
      Referring to  FIGS. 3 and 4 , the driving device  36  includes a driving element  362 , a shaft  364 , and two rods  366 . The shaft  364  has one end connected with the driving element  362  and the other end connected to the two rods  366 . Each rod  366  has one end coupled to a bottom of each clamping portion  34  and the other end hinged with the other end of the shaft  364 . The rods  366  extend through and are slidable in the slots  328  on the bottom  322 . The driving element  362  is, for example, a pneumatic cylinder, or a hydraulic cylinder. The driving element  362  drives the shaft  364  to move lengthwise, the rods  366  then drive the clamping portions  34  to move between the holding position and the releasing position. When the shaft  364  is driven by the driving element  362  to move downward, the rods  366  drive the clamping portions  34  to move towards each other to clamp the lens preform  40  (referring to  FIG. 5 ); when the shaft  364  is driven by the driving element  362  to move upward, the rods  366  drive the clamping portions  34  to move away from each other to release the lens preform  40 .  
      Referring to FIGS.  5  to  7 , the lens preform  40  includes two lenses  42 , a sprue forming portion  44 , and two runner forming portions  46 . The lenses  42  are connected to the sprue forming portion  44  by the runner forming portions  46 . The lens preform  40  is held by the clamping device  30  in the cutting process. The operation of the clamping device  30  includes the steps of: 
      driving the clamping portions  34  to move away from each other;     dropping the lens preform  40  into the clamping device  30 ;     driving the clamping portions  34  to move towards each other to clamp the lens preform  40  firmly; and     cutting the lens  42  from the lens preform  40 .    

      Referring to  FIGS. 8 and 9 , a clamping device  50  for clamping the lens preform  10  is shown in accordance with a second embodiment. The clamping device  50  includes a base  52 , four clamping portions  54  and a driving device (not shown) similar to the driving device  36  of the clamping device shown in  FIG. 1 . The clamping device  50  is similar to the clamping device  30 , but includes four clamping portions  54 . Each clamping portion  54  is a quarter-cylinder with a recess defined therein at a top thereof. Each pair of adjacent recesses cooperatively form a space  542  when the two adjacent clamping portions are in contact with each other. The driving device drives the clamping portions  54  to move towards each other to clamp the lens preform  10  and to move away from each other to release the lens preform  10 .  
      The operation of the clamping device is similar to that of the clamping device  30 .  
      It should be noted that the clamping device can have at least two clamping portions depending on the lens preform to be cut. Each clamping portion can be a part cylinder.  
      Although the present invention has been described with reference to specific embodiments, it should be noted that the described embodiments are not necessarily exclusive, and that various changes and modifications may be made to the described embodiments without departing from the scope of the invention as defined by the appended claims.