Injection molding method and mold mechanism

Abstract

An injection molding method includes the steps of positioning a core piece in a mold cavity through a plurality of positioning pins; injecting a molten plastic material into the mold cavity to surround and cover the core piece; maintaining the pressure inside the mold cavity at a predetermined maintaining time so that the core piece is positioned by the molten plastic material; retracting the positioning pins from the mold cavity when a predetermined retraction time is reached, so that spaces occupied by the positioning pins in the mold cavity can be filled with the molten plastic material; and completely curing the molten plastic material to form a finished product.

What is claimed is: 
     
         1 . An injection molding method, comprising the steps of:
 positioning a core piece in a mold cavity defined by male and female molds through a plurality of positioning pins;   injecting a molten material into the mold cavity to surround and cover the core piece;   maintaining the pressure inside the mold cavity at a predetermined maintaining time so that the core piece is positioned by the molten material;   retracting the positioning pins from the mold cavity when a predetermined retraction time is reached, so that spaces occupied by the positioning pins in the mold cavity can be filled with the molten material, the predetermined retraction time being the time before the predetermined maintaining time is reached and before the molten material is completely cured; and   completely curing the molten material to form a finished product.   
     
     
         2 . The injection molding method as claimed in  claim 1 , wherein the predetermined retraction time is 0.5 seconds. 
     
     
         3 . The injection molding method as claimed in  claim 2 , wherein the predetermined maintaining time to maintain the pressure inside the mold cavity is 5 seconds. 
     
     
         4 . An injection mold mechanism comprising:
 a male mold including a base plate, and an embedding portion disposed on said base plate and formed with an embedding groove;   a pushing system including a push rod that is actuatable to move through said male mold along a pushing direction; and   a male mold core disposed in said embedding groove and including
 a forming member having a first mold cavity, and 
 a positioning module including a plurality of positioning pin units each of which has a slide member, at least one positioning pin fixed on said slide member, and a drive member to drive movement of said slide member; 
   wherein, prior to actuation of said push rod, said slide members of said positioning pin units are spaced apart from each other and said positioning pins of said positioning pin units extend into said first mold cavity; and   wherein, when said push rod is actuated, said push rod pushes said drive members of said positioning pin units to respectively engage said slide members and drive said slide members to move toward each other to thereby retract said positioning pins from said first mold cavity.   
     
     
         5 . The injection mold mechanism as claimed in  claim 4 , wherein said male mold core further includes a connecting member having an engaging groove, and a holding member sandwiched between said forming member and said connecting member, said push rod extending movably through said engaging groove, said forming member further having a plurality of slide grooves respectively receiving said slide members of said positioning pin units, said first mold cavity being formed on an outer periphery of said forming member, said holding member having a plurality of first receiving holes respectively receiving said drive members of said positioning pin units, and a second receiving hole communicating with said first receiving holes for receiving said push rod. 
     
     
         6 . The injection mold mechanism as claimed in  claim 5 , wherein said slide member of each of said positioning pin units has a through hole, said drive member of each of said positioning pin units having an abutment portion abutting against said push rod, and an inclined insert portion that is inclined with respect to said abutment portion and that is movable into said through hole. 
     
     
         7 . The injection mold mechanism as claimed in  claim 5 , wherein said push rod has a main body, a neck portion connected to said main body, and a pushing portion connected to said neck portion opposite to said main body, said engaging groove of said connecting member having an inverted U-shaped cross section with an opening that opens downward, said neck portion having a cross-sectional area smaller than that of said main body and that of said pushing portion, and being inserted movably into said engaging groove through said opening, said pushing portion extending into said second receiving hole of said holding member and having a shape matching that of said second receiving hole. 
     
     
         8 . The injection mold mechanism as claimed in  claim 7 , further comprising a female mold, and a female mold core disposed on said female mold and including a main body, and a second mold cavity formed in said main body of said female mold core, said first and second mold cavities forming a complete mold cavity when said male and female molds are mated. 
     
     
         9 . The injection mold mechanism as claimed in  claim 8 , further comprising a runner system located in said female mold and communicating with said second mold cavity. 
     
     
         10 . The injection mold mechanism as claimed in  claim 9 , wherein said runner system includes a gate provided in said female mold distal from said male mold, at least one runner extending through said female mold and said female mold core and communicating with said gate, and a sprue that corresponds in number to said runner and that communicates with said second mold cavity. 
     
     
         11 . An injection mold mechanism comprising:
 a male mold core including
 a forming member having a first mold cavity, and 
 a positioning module including a plurality of inner positioning pin units each of which has an inner slide member, at least one inner positioning pin fixed on said inner slide member, and an inner drive member to drive movement of said inner slide member; 
   a male mold including abase plate, and an embedding portion disposed on said base plate, and a plurality of outer positioning pin units, said embedding portion being formed with an embedding groove in a surface that is opposite to an interface between said embedding portion and said base plate for receiving said male mold core, each of said outer positioning pin units having an outer slide member with a through hole, an outer positioning pin fixed on said outer slide member, and an outer drive member to drive movement of said outer slide member, said outer drive member having an outer abutment portion and an inclined insert portion that is inclined with respect to said outer abutment portion and that is movable into said through hole in said outer slide member; and   a pushing system including an inner push rod that is actuatable to move through said male mold along a pushing direction, a first push plate connected to said push rod, a plurality of springs that are disposed on said first push plate and that extend toward said male mold core, a second push plate that is connected to said springs opposite to said first push plate and that is parallel to said first push plate, and a plurality of outer push rods that are connected to said second push plate and that extend through said male mold, said inner push rod abutting against said inner drive member, each of said outer push rods abutting against said outer drive member of a respective one of said outer positioning pin units;   wherein, prior to actuation of said inner and outer push rods, said inner slide members of said inner positioning pin units are spaced apart from each other, said outer slide members of said outer positioning pin units are also spaced apart from each other, and said inner positioning pins of said inner positioning pin units and said outer positioning pins of said outer positioning pin units extend into said first mold cavity;   wherein, when said inner push rods are actuated, said inner push rod pushes said inner drive members of said inner positioning pin units to respectively engage said inner slide members and drive said inner slide members to move toward each other to thereby retract said inner positioning pins from said first mold cavity; and   wherein, when said outer push rods are actuated, said outer push rod pushes said outer drive members of said outer positioning pin units to respectively engage said outer slide members and drive said outer slide members to move toward each other to thereby retract said outer positioning pins from said first mold cavity.   
     
     
         12 . The injection mold mechanism as claimed in  claim 11 , wherein said male mold core further includes a connecting member having an engaging groove, and a holding member sandwiched between said forming member and said connecting member, said inner push rod extending movably through said engaging groove, said forming member further having a plurality of slide grooves respectively receiving said inner slide members of said inner positioning pin units, said first mold cavity being formed on an outer periphery of said forming member, said holding member having a plurality of first receiving holes respectively receiving said inner drive members of said inner positioning pin units, and a second receiving hole communicating with said first receiving holes for receiving said inner push rod. 
     
     
         13 . The injection mold mechanism as claimed in  claim 12 , wherein said inner slide member of each of said inner positioning pin units has a through hole, said inner drive member of each of said inner positioning pin units having an abutment portion abutting against said inner push rod, and an inclined insert portion that is inclined with respect to said abutment portion of said inner drive member and that is movable into said through hole in said inner slide member. 
     
     
         14 . The injection mold mechanism as claimed in  claim 12 , wherein said inner push rod has a main body, a neck portion connected to said main body, and a pushing portion connected to said neck portion opposite to said main body, said engaging groove of said connecting member having an inverted U-shaped cross section with an opening that opens downward, said neck portion having a cross-sectional area smaller than that of said main body and that of said pushing portion, and being inserted movably into said engaging groove through said opening, said pushing portion extending into said second receiving hole of said holding member and having a shape matching that of said second receiving hole. 
     
     
         15 . The injection mold mechanism as claimed in  claim 14 , further comprising a female mold, and a female mold core disposed on said female mold and including a main body, and a second mold cavity formed in said main body of said female mold core, said first and second mold cavities forming a complete mold cavity when said male and female molds are mated. 
     
     
         16 . The injection mold mechanism as claimed in  claim 14 , further comprising a runner system located in said female mold and communicating with said second mold cavity. 
     
     
         17 . The injection mold mechanism as claimed in  claim 16 , wherein said runner system includes a gate provided in said female mold distal from said male mold, at least one runner extending through said female mold and said female mold core and communicating with said gate, and a sprue that corresponds in number to said runner and that communicates with said second mold cavity.