Patent Publication Number: US-2007114699-A1

Title: Mold and mold releasing method of the same

Description:
FIELD OF THE INVENTION  
      The present invention relates to a mold and a mold releasing method of the same, and more particularly relates to a mold being suitable for molding optical elements and a mold releasing method using the same.  
     DESCRIPTION OF RELATED ART  
      Optical elements are generally made by molding processes. Especially for plastic optical elements, such as micro lenses or light guide plates, the injection molding method is generally employed. The injection molding method has advantages such as high production rate and efficiency, and cost of optical elements thereby can be reduced. During the molding process, ejector elements are generally employed for separating the optical elements from a molding surface of the mold.  
      In a typical mold for molding optical elements, ejector pins are employed as the ejector elements. In operation, the ejector pins can push peripheries of the optical elements to separate the optical elements from molding surfaces. However, optical elements are required to satisfy requirements such as downsizing and weight reduction, and the peripheral portions of the optical elements are getting smaller. Correspondingly, the diameters of the ejector pins must be downsized, which results that the ejector pins are too small to separate the optical elements easily.  
      In another typical mold for molding optical elements, a mold core is employed as the ejector element. However, the movements of the mold core may lead to problems such as abrasion and decentration, which results that the quality of the optical elements is reduced, and the service life of the mold is shorten.  
      What is needed, therefore, is a mold for molding optical elements which has long service life and can release optical elements easily.  
      What is also needed, therefore, is a mold releasing method using the mold.  
     SUMMARY OF THE INVENTION  
      In a preferred embodiment, a mold for molding optical elements includes a mold core and a gas blowing device. The mold core includes a molding surface, at least one gas inlet, a plurality of gas outlets located around the molding surface, a plurality of gas channels defined therein for connecting the at least one gas inlet and the gas outlets, and a plurality of switch elements positioned around the molding surface and configured for opening and closing the gas outlets. The gas blowing device has an output end communicated with the at least one gas inlet and is configured for blowing gas into the gas channels.  
      In another preferred embodiment, a mold releasing method using the above-described mold comprises the steps of: opening the gas outlets by operating the switch elements; blowing gas into the gas channels via the output end and the at least one gas inlet by operating the gas blowing device; and releasing the optical element by adjusting the pressure of the gas via controlling the output end.  
      Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the present invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a schematic, cross-sectional view of a mold for molding optical elements in accordance with a first preferred embodiment;  
       FIG. 2  illustrates a schematic, cross-sectional view of the mold of  FIG. 1  during molding process;  
       FIG. 3  illustrates a schematic, cross-sectional view of the mold of  FIG. 1  during mold releasing process;  
       FIG. 4  is a schematic, cross-sectional view of a mold for molding optical elements in accordance with a second preferred embodiment during molding process; and  
       FIG. 5  illustrates a schematic, cross-sectional view of the mold of  FIG. 4  during mold releasing process. 
    
    
      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  
      Embodiments of the present invention will now be described in detail below and with reference to the drawings.  
      Referring to  FIG. 1 , a mold  10  according to a first preferred embodiment is provided. The mold  10  includes a mold core  100  and a gas blowing device  150 . The mold core  100  includes a molding surface  110 , a plurality of gas inlets  121 , a plurality of gas outlets  122  located around the molding surface  110 , a plurality of gas channels  120  connecting the gas inlets  121  and the gas outlets  122 , and a plurality of switch elements  130  positioned around the molding surface  110  and configured for opening and closing the gas outlets  122 . The gas blowing device  150  has an output end  151  communicated with the gas inlets  121  configured for blowing a gas into the gas channels  120 . The switch elements  130  each includes a slidable portion  131  having an end surface  133  and a driving portion  132  configured for driving the slidable portion  131 .  
      The mold core  100  is made from a material selected from the group comprising stainless steel, super-hard alloy, carbide ceramic and cermet. The molding surface  110  may be a spherical surface or an aspheric surface. The gas outlets  122  can be arranged around the molding surface  110  in a predetermined layout. The slidable portion  131  is made from a material selected from the group comprising stainless steel, super-hard alloy, carbide ceramic and cermet. The driving portion  132  can be selected from the group comprising spring, screw rod, retractable pole and folding bracket. In the preferred embodiment, the mold core  100  and slidable portions  131  are made from stainless steel. The molding surface  110  is an aspheric surface. The gas outlets  122  are spacedly distributed in an annular region (not labeled) around an edge of the molding surface  110  symmetrically. The annular region has a width of 0.5 mm (millimeter). The diameter of each gas outlet  122  is less than 0.5 mm. The driving portions  132  each employs a folding bracket.  
      Referring to  FIG. 2 , the mold  10  is in process for molding an optical element  101 . The driving portions  132  are extended and thereby the gas outlets  122  are closed by the slidable portions  131 . In the preferred embodiment, the end surfaces  133  of the slidable portions  131  are substantially coplanar with top portion of the molding surface  110 . Therefore, portions of the gas channels  120  which adjacent to the gas outlets  122  are plugged by the slidable portions  131 .  
      Referring to  FIG. 3 , a mold releasing method using the mold  10  is also provided. The method comprises the steps of: opening the gas outlets  122  via retracting the slidable portions  131  by the driving portions  132 , and the gas outlets  122  and the gas inlets  121  are communicated via the gas channels  120 ; blowing the gas into the gas channels  120  via the output end  151  and the gas inlets  121  by operating the gas blowing device  150 , the gas thereby blowing to a periphery of the optical element  101  via the gas outlets  122 ; and adjusting the pressure of the gas via controlling the output end  151  thereby pushing the periphery of the optical element  101  to separate the optical element  101  from the molding surface  110 . The gas may employ any suitable gas such as nitrogen gas or clean dry air.  
      Referring to  FIG. 4  and  FIG. 5 , a mold  20  according to a second preferred embodiment is provided. The mold  20  for molding an optical element  201  includes a mold core  200  and a gas blowing device  250 . The mold core  200  includes a molding surface  210 , a gas inlets  221 , a plurality of gas outlets  222  located around the molding surface  210 , a plurality of gas channels  220  connecting the gas inlet  221  and the gas outlets  222 , and a plurality of switch elements  230  configured around the molding surface  210  to open and close the gas outlets  222 . The gas blowing device  250  has an output end  251  communicated with the gas inlet  221  configured for blowing a gas into the gas channels  220 . The switch elements  230  each includes a slidable portion  231  and a driving portion  232  configured for driving the slidable portion  231 .  
      The mold  20  is similar to the mold  10  of the first embodiment. However, the mold  20  only employs one gas inlet  221  connecting with the gas outlets  222  via the gas channels  220 . The driving portions  232  are retracted and thereby the gas outlets  222  are closed by the slidable portions  231 . The slidable portions  231  are moving at a surface which substantially coplanar with the gas outlets  222 .  
      As stated above, the mold and mold releasing method in accordance with preferred embodiments employ a plurality of gas channels, gas outlets and switch elements. Therefore, during mold releasing processes, the optical element can be separated from the molding surface by gas flow output from the gas outlets. The optical element can be released easily. Furthermore, the movements of the mode core for mold releasing are not necessary, problems such as abrasion and decentration thereby can be avoided.  
      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 hereinbefore described merely being preferred or exemplary embodiments of the invention.