Abstract:
Disclosed herein is a mold device. The mold device includes: an injection molding core; an ejector pin disposed under the core to pull the core in injection; a first magnet disposed at the lower end of the core; and a second magnet disposed at the upper end of the ejector pin to attract the first magnet and prevent the core from being biased.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2010-0032401, filed on Apr. 8, 2010, entitled “A Mold Device”, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a mold device. 
         [0004]    2. Description of the Related Art 
         [0005]    The present invention relates to a mold device, in particular, to a lens mold device. Plastic lenses have the advantage in low material cost and high productivity in comparison with glass lenses, such that they are used for various fields, such as mobile phone cameras and disc pick-up devices. The picture performance of camera modules of mobile and the form accuracy of lenses are in close connection with each other and the outer diameter of the lenses and concentricity of a non-spherical curved surface are one of the factors having the most relation to the picture performance. The lenses of the camera modules of mobile phones are made of plastic lenses and glass lenses and the plastic lenses are manufactured by injection molding. Since the lens-shaped portion of the mold is transcribed to form the shape of a lens product in the injection molding, the accuracy of the mold is very important and the concentricity of the portion corresponding to the outer diameter of the lens product and the portion corresponding to the non-spherical surface of the lens in the mold has a direct effect on the concentricity of the lens product. 
         [0006]      FIG. 7  is a cross-sectional view showing the entire structure of a molding for forming an injection-molded part of a lens according to the related art, in which the molding includes a movable plate  11 , a movable core  12 , a stationary plate  13 , and a stationary core  14 . As shown in the figure, the concentricity of the lenses are affected by the driving accuracy of the movable core  12 , machining accuracy of the lens outer circumference of the movable plate  11 , an assembly gap of the movable core  12  and the movable plate  11 , machining accuracy of the stationary core  14 , an assembly gap of the stationary core  14  and the stationary plate  13 , and shape accuracy of the movable plate  11  and the stationary plate  15 . 
         [0007]    In the lens mold device according to the related art, an ejector pin is fastened by a core and a bolt to eject the movable core after filling the lens gap. However, in this configuration, when the concentricity of the ejector pin and the core is not matched, the core biases in fastening the ejector pin with the bolt, such that it may fail to achieve accurate concentricity of the injection-molded part for the lens. 
         [0008]    Therefore, research for removing the problems and improving the concentricity in a lens mold is significantly required. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in an effort to provide a mold device having improved concentricity of the mold, removing the problems. 
         [0010]    A mold device according to an exemplary embodiment of the present invention includes: an injection molding core; an ejector pin disposed under the core to pull the core in injection; a first magnet disposed at the lower end of the core; and a second magnet disposed at the upper end of the ejector pin to attract the first magnet and prevent the core from being biased. 
         [0011]    In this configuration, the first magnet and the second magnet are fastened to the core and the ejector pin by a first fastening member and a second fastening member, respectively. 
         [0012]    Further, the first fastening member and the second fastening member are bolts or pins. 
         [0013]    Further, a plate is further provided under the ejector pin, and a first magnet and a fourth magnet are further disposed at the lower end of the ejector pin and the upper end of the plate. 
         [0014]    Further, the core ejects a lens mold. 
         [0015]    A mold device according to another exemplary embodiment of the present invention includes: an injection molding core; an ejector pin fastened to the core; a plate disposed under the ejector pin to support the ejector pin; a third magnet disposed at the lower end of the ejector pin; and a fourth magnet disposed at the upper end of the plate to attract the third magnet. 
         [0016]    In this configuration, the third magnet and the fourth magnet are fastened to the ejector pin and the plate by a third fastening member and a fourth fastening member, respectively. 
         [0017]    Further, the third fastening member and the fourth fastening member are bolts or pins. 
         [0018]    Further, the core ejects a lens mold. 
         [0019]    A mold device according to another exemplary embodiment of the present invention includes: an injection molding core; a metal-based ejector pin fastened to the core; a plate disposed under the ejector pin to support the ejector pin; and a fourth magnet disposed at the upper end of the plate to attract the ejector pin. 
         [0020]    In this configuration, the fourth magnet is fastened to the plate by a fourth fastening member. 
         [0021]    Further, the fourth fastening member is a bolt or a pin. 
         [0022]    Further, the core ejects a lens mold. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a cross-sectional view of a mold device according to a first exemplary embodiment of the present invention; 
           [0024]      FIG. 2  is a cross-sectional view of a mold device according to a second exemplary embodiment of the present invention; 
           [0025]      FIG. 3  is a cross-sectional view of a mold device according to a third exemplary embodiment of the present invention; 
           [0026]      FIG. 4  is a cross-sectional view of a mold device according to a fourth exemplary embodiment of the present invention; 
           [0027]      FIG. 5  is a partial enlarged view of a mold device according to exemplary embodiments of the present invention; 
           [0028]      FIG. 6  is a perspective view of a lens shape according to exemplary embodiments of the present invention; and 
           [0029]      FIG. 7  is a cross-sectional view showing the entire structure of a molding according to the related art. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Various objects, advantages and features of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings. 
         [0031]    The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the best method he or she knows for carrying out the invention. 
         [0032]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. In the specification, in adding reference numerals to components throughout the drawings, it is to be noted that like reference numerals designate like components even though components are shown in different drawings. Further, in describing the present invention, a detailed description of related known functions or configurations will be omitted so as not to obscure the gist of the present invention. 
         [0033]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0034]      FIG. 1  is a cross-sectional view of a mold device according to a first exemplary embodiment of the present invention,  FIG. 2  is a cross-sectional view of a mold device according to a second exemplary embodiment of the present invention, and  FIG. 3  is a cross-sectional view of a mold device according to a first exemplary embodiment of the present invention. Further,  FIG. 4  is a cross-sectional view of a mold device according to a fourth exemplary embodiment of the present invention,  FIG. 5  is a partial enlarged view of a mold device according to exemplary embodiments of the present invention, and  FIG. 6  is a perspective view of a lens shape according to exemplary embodiments of the present invention. 
         [0035]    As shown in  FIG. 1 , a mold device  100   a  according to a first exemplary embodiment of the present invention includes a core  110 , a first platen  111 , a first magnet  112 , a first fastening member  113 , an ejector pin  120 , a second platen  121 , a second magnet  122 , a second fastening member  123 , and a plate  130 . 
         [0036]    The core  110  is disposed inside the first platen  111  shaping a mold and used to eject the mold. 
         [0037]    S 1  of the first platen  111  represents the curved surface of a plastic lens that is a mold according to an exemplary embodiment of the present invention and S 2  represents the outer diameter of the plastic lens. 
         [0038]    Concentricity of the plastic lens is associated with optical properties of a camera and the magnitude becomes more restricted with the increase in pixels of the camera. Therefore, the value of the center of the concentricity to the center of the outer diameter is considered important. 
         [0039]    The first magnet  112  is attached to the lower end of the core  110  and the core  110  and the first magnet  112  are combined by the first fastening member  113 . 
         [0040]    The ejector pin  120  separates the product from the mold, as the mold opens, and is fixed by the second platen  121 . 
         [0041]    A second magnet  122  is attached to the upper end of the ejector pin  120 , at the position corresponding to the first magnet  112  attached to the lower end of the core  110 . The second magnet  122  and the first magnet  112  attract each other such that the ejector pin  120  and the core  110  are positioned adjacent to each other. The second magnet  122  and the ejector pin  120  are combined by the second fastening member  123 . 
         [0042]    In this configuration, although the first fastening member  113  and the second fastening member  123  can be variously implemented by bolts, pins, and adhesives, etc., it should be noted that they are included in the spirit of the present invention. 
         [0043]    When the lower end of the core  110  is attached to the upper end of the ejector pin  120  by the magnets, the core  110  is not biased even if concentricity is not achieved between the core  110  and the ejector pin  120  in ejecting the product. In this configuration, the polarities of first magnet  112  and the second magnet  122  are arranged such that the magnets attract each other, as shown in  FIG. 5 . 
         [0044]    Since the temperature of the mold is around 150° C. in injecting the lens, the magnets should be made of a heat resistance material (e.g. neodymium magnet) keeping magnetism even at the temperature. Further, the core  110  is not biased nor deformed to one side in assembling even if the centers of the ejector pin hole and the core holes do not match. Since the core  110  is attracted by the magnet even in this state, it does not matter in ejecting the product. 
         [0045]    The plate  130  supports the lower end of the ejector pin  120  to easily eject the core  110 . 
         [0046]      FIG. 2  shows a mold device  100   b  according to a second exemplary embodiment of the present invention and of which the basic configuration and shape are the same as those of the mold device  100   a  according to the first exemplary embodiment of the present invention; therefore, the function and characteristics of the same parts are not described. 
         [0047]    Although the mold device  100   b  according to a exemplary second embodiment of the present invention is basically the same as the structure and the shape of the mold device  100   a  according to the first embodiment, it is different in that a third magnet  124  is attached to the lower end of the ejector pin  120 . The ejector pin  120  and the third magnet  124  are combined by a third fastening member  125 . 
         [0048]    A fourth magnet  131  is attached to the upper surface facing the third magnet  124  of the plate  130   b . The polarities of the third magnet  124  and the fourth magnet  131  are arranged such that the magnets attract each other. The plate  130   b  and the fourth magnet  131  are combined by the fourth fastening member  132 . 
         [0049]    In this configuration, although the third fastening member  125  and the fourth fastening member  132  can be variously implemented by bolts, pins, and adhesives, etc., it should be noted that they are included in the spirit of the present invention. 
         [0050]      FIG. 3  shows a mold device  100   c  according to a third exemplary embodiment of the present invention and of which the basic configuration and shape are the same as those of the mold device  100   a  according to the first exemplary embodiment of the present invention; therefore, the function and characteristics of the same parts are not described. 
         [0051]    Although the mold device  100   c  according to the third exemplary embodiment of the present invention is basically the same as the structure and the shape of the mold device  100   a  according to the first embodiment, it is different in that the core  110  and the ejector pin  120  are combined by a bolt (not shown) as in the related art, and the third magnet  124  and the fourth magnet  131  are disposed at the lower end of the ejector pin  120  and the upper end of the plate  130   b , respectively. 
         [0052]    The polarities of the third magnet  124  and the fourth magnet  131  are arranged such that the magnets attract each other, and the magnets are fastened by the third fastening member  125  and the fourth fastening member  132 , respectively. 
         [0053]    The plate  130   b  and the ejector pin  120  are attached by the third magnet  124  and the fourth magnet  131 . 
         [0054]      FIG. 4  shows a mold device  100   d  according to a fourth exemplary embodiment of the present invention and of which the basic configuration and shape are the same as those of the mold device  100   a  according to the first exemplary embodiment of the present invention; therefore, the function and characteristics of the same parts are not described. 
         [0055]    Although the mold device  100   d  according to the fourth exemplary embodiment of the present invention is basically the same as the structure and the shape of the mold device  100   a  according to the first embodiment, it is different in that the core  110  and the ejector pin  120  are combined by a bolt (not shown) as in the related art, and the fourth magnet  131  is disposed only at the upper end of the plate  130  where the lower end of the ejector pin  120  contacts. 
         [0056]    The ejector pin  120  is made of a metal-based material, such that it can be attached to the fourth magnet  131  of the plate  130   b , without being provided with a specific magnet. The core  110  is ejected by the ejector pin  120  and the plate  130   b  attached to each other. 
         [0057]      FIG. 5  shows when different polarities are disposed to face each other such that attracting force is generated between the first and third magnets  112  and  124  and the second and fourth magnets  122  and  131  included in the mold devices  100   a ,  100   b ,  100   c , and  100   d  according to the embodiments of the present invention. The first and third magnets  112  and  124  and the second and fourth magnets  122  and  131  are respectively combined by the first and third bolts  113  and  125  and the second and fourth bolts  123  and  132 . 
         [0058]      FIG. 6  shows a lens  140  injection-molded by the mold devices  100   a ,  100   b ,  100   c , and  100   d  according to the exemplary embodiments of the present invention, in which S 1  represents the curved surface of the lens and S 2  represents the outer diameter of the lens. In this configuration, the concentricity of the center of the curved surface to the center of the outer diameter is an important factor in the performance of a camera, it can be seen from an experiment that the concentricity of the lens  140  injection-molded by the mold devices  100   a ,  100   b ,  100   c , and  100   d  according to the embodiments of the present invention is 2˜5 μm, which is considerably improved, in comparison to 9˜13 μm in the related art. 
         [0059]    In the mold devices  100   a ,  100   b ,  100   c , and  100   d  according to the present invention, it is possible to easily improve the concentricity of an injection-molded product by disposing a magnet between the core  110  and the ejector pin  120  or between the ejector pin  120  and the plate  130  to attach them. 
         [0060]    In particular, it is also very effective in adjusting the concentricity of the plastic lens products. 
         [0061]    According to a mold device of the present invention, it is possible to easily improve concentricity of an injection-molded product by disposing a magnet between a core and an ejector pin or the ejector pin and a plate to attach them, such that it is very effective particularly in adjusting the concentricity of plastic lens products. 
         [0062]    Although the embodiments of the present invention has been disclosed for illustrative purposes, it will be appreciated that a mold device according to the invention is not limited thereby, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
         [0063]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.