Patent Publication Number: US-2005132751-A1

Title: Method for making a precision molding glass and molding device implementing for the method

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority of Taiwanese Application No. 092136547, filed on Dec. 23, 2003.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a method for making a precision molding glass, and a molding device for implementing the method.  
      2. Description of the Related Art  
      In conventional precision glass molding technology, a softened glass material is pressed by two mold portions having opposite molding surfaces to form a solid semi-product. The semi-product is then processed by a centering unit so as to remove an excess amount of the glass material from the semi-product by polishing to obtain a precision molding glass product.  
      Referring to  FIG. 1 , the conventional centering unit  1  includes a clamping member  101  for clamping the semi-product  2 , and a polishing member  102  for polishing the semi-product  2  to remove the excess amount of the glass material from the semi-product  2 . Although the centering unit  1  can be used for removing the excess amount of glass material to make the precision molding glass product, it has the following disadvantages:  
      1. When the semi-product  2  is clamped by the clamping member  101 , a center line of the semi-product  2  is liable to be offset from an axis of the clamping member  101 , which in turn results in the introduction of a relatively large error in the precision glass product.  
      2. The surface of the semi-product is liable to be abraded due to the clamping of the clamping member  101 .  
      3. Since use of the polishing member  102  is required to remove the excess amount of the glass material from the semi-product  2 , the cost for making the precision molding glass product is relatively high.  
      4. Since the precision molding glass product is made by separate molding and centering steps, the conventional method is relatively complicated to practice.  
     SUMMARY OF THE INVENTION  
      Therefore, the object of the present invention is to provide a method for making a precision molding glass having advantages of relatively simple processing, relatively low production costs, and relatively high precision.  
      In one aspect of this invention, a method for making a precision molding glass includes the steps of: 
          (a) preparing a molding device including a first mold, and a second mold which has an axis common with that of the first mold, the first mold having a first molding surface centered at the axis, a first peripheral surface extending around the axis and connected to the first molding surface, and a first edge formed between the first molding surface and the first peripheral surface, the first peripheral surface having a first distal peripheral portion distal from the first edge, the second mold having a second molding surface opposite to the first molding surface and centered at the axis, a second peripheral surface extending around the axis and connected to the second molding surface, and a second edge formed between the second molding surface and the second peripheral surface, the second peripheral surface having a second distal peripheral portion distal from the second edge;     (b) mounting a centering unit having a shearing portion around the molding device such that the shearing portion is movable axially between the first and second distal peripheral portions;     (c) placing a glass material between the first and second molding surfaces;     (d) heating the glass material to a molding temperature;     (e) molding the glass material by moving axially the first and second molds toward each other until the glass material is pressed to have a predetermined central thickness and until an excess amount of the glass material is squeezed out of the first and second edges;     (f) lowering the temperature of the glass material; and     (g) while the glass material is still soft, moving the centering unit from one of the first and second distal peripheral portions to the other one of the first and second distal peripheral portions such that the shearing portion of the centering unit removes the excess amount of the glass material.        

      In another aspect of this invention, a molding device for making a precision molding glass includes a first mold, a second mold having an axis common with that of the first mold, and a centering unit having a shearing portion. The first mold has a first molding surface centered at the axis, a first peripheral surface extending around the axis and connected to the first molding surface, and a first edge formed between the first molding surface and the first peripheral surface. The first peripheral surface has a first distal peripheral portion distal from the first edge. The second mold has a second molding surface opposite to the first molding surface and centered at the axis, a second peripheral surface extending around the axis and connected to the second molding surface, and a second edge formed between the second molding surface and the second peripheral surface. The second peripheral surface has a second distal peripheral portion distal from the second edge. The centering unit is mounted such that the shearing portion is movable axially between the first and second distal peripheral portions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:  
       FIG. 1  is a schematic view of a centering unit used in a conventional method for making a precision molding glass;  
       FIG. 2  is a flow diagram of the preferred embodiment of a method for making a precision molding glass according to this invention;  
      FIGS.  3  to  6  are schematic sectional views showing consecutive steps of the preferred embodiment of  FIG. 2 ; and  
       FIG. 7  is a sectional view of the precision molding glass made by the preferred embodiment of  FIG. 2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 2 , the preferred embodiment of the method for making a precision molding glass is shown to include the steps of:  
      A) Preparing a Molding Device  100 :  
      Referring to  FIG. 3 , the molding device  100  includes a first mold  10 , and a second mold  20  which has an axis (L) common with that of the first mold  10 . The first mold  10  has a first molding surface  11  centered at the axis (L), a first peripheral surface  12  extending around the axis (L) and connected to the first molding surface  11 , and a first edge  13  formed between the first molding surface  11  and the first peripheral surface  12 . The first peripheral surface  12  has a first distal peripheral portion  14  distal from the first edge  13 . The second mold  20  has a second molding surface  21  opposite to the first molding surface  11  and centered at the axis (L), a second peripheral surface  22  extending around the axis (L) and connected to the second molding surface  21 , and a second edge  23  formed between the second molding surface  21  and the second peripheral surface  22 . The second peripheral surface  22  has a second distal peripheral portion  24  distal from the second edge  23 .  
      B) Mounting a Centering Unit  30 :  
      The centering unit  30  has a shearing portion  31 , and is mounted around the molding device  100  such that the shearing portion  31  is movable axially between the first and second distal peripheral portions  14 , 24 . The shearing portion  31  of the centering unit  30  includes an annular blade  311  extending transversely of the axis (L) of the first and second molds  10 , 20 . The annular blade  311  has a thickness in the direction of the axis (L), and includes a cutting edge  312  proximate to either one of the first and second peripheral surfaces  12 ,  22 . The thickness is gradually enlarged from the cutting edge  312  as the annular blade  311  extends away from the molding device  100 .  
      C) Placing a Glass Material  40 :  
      The glass material  40  is placed between the first and second molding surfaces  11 , 21 .  
      D) Purging:  
      In the preferred embodiment, the molding device  100  is mounted within a shield  200 , which is made of quartz, and which is provided with a heating element  210 . After placing the glass material  40  between the molding surfaces  11 , 21 , the inside of the shield  200  is purged with nitrogen so as to protect the glass material  40  from oxidation.  
      E) Heating:  
      The glass material  40  is heated by the heating element  210  to a molding temperature T 1 .  
      F) Molding:  
      Referring to  FIGS. 4 and 5 , the glass material  40  is molded by moving axially the first and second molds  10 , 20  toward each other until the glass material  40  is pressed to have a predetermined central thickness and until an excess amount (I) of the glass material  40  is squeezed out of the first and second edges  13 , 23 .  
      G) Temperature Lowering:  
      The temperature of the glass material  40  is lowered to a temperature which is approximate to yield point A t  of the glass material  40 , and in which the glass material  40  is still in a soft state. H) removing the excess amount (I) of the glass material  40 :  
      With further reference to  FIG. 6 , while the glass material  40  is still soft, the centering unit  30  is moved from the second distal peripheral portion  24  to the first distal peripheral portion  14  such that the shearing portion  31  of the centering unit  30  removes the excess amount (I) of the glass material  40  to result in a molded glass  40 ′. The molding device  100  is maintained in a molding state until the temperature of the molded glass  40 ′ is lowered below the glass transition temperature T g  thereof.  
      I) Returning the Centering Unit  30 :  
      The centering unit  30  is returned from the first distal peripheral portion  14  back to the second distal peripheral portion  24 , as shown by the dotted lines in  FIG. 6 . Since the annular blade  311  has a thickness that is gradually enlarged from the cutting edge  312  as the annular blade  311  extends away from the molding device  100 , the risk of damage to the molded glass  40 ′ by the annular blade  311  can be reduced.  
      J) Separating the First and Second Molds  10 , 20 :  
      The first and second molds  10 , 20  are moved away from each other to obtain a precision molding glass  40 ″, and to permit taking of the precision molding glass  40 ″ out of the molding device  100 . The precision molding glass  40 ″ thus made is illustrated in  FIG. 7 .  
      In view of the aforesaid, since the centering processing is conducted while the molded glass is still in a soft state within the molding device  100 , the aforesaid disadvantages of the prior art can be overcome by the molding method of this invention. Furthermore, since the polishing processing is not required in the molding method of this invention, the yield for the precision molding glass  40 ″ can be increased, and the production cost therefor can be reduced.  
      While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.