Die-casting mold and method for thin-walled electrical connector shells

Abstract

The present invention discloses a die-casting mold structure for a thin-walled shell for electrical connectors and a method for designing the mold structure. The runner of the mold structure includes a longitudinal runner, a transverse runner, an end runner, and an in-gate connected sequentially. The cross-sectional areas of the longitudinal runner, the transverse runner, the end runner, and the in-gate decrease progressively. The cross sections of the longitudinal runner and the transverse runner may be oval or circular in shape. The perimeter-to-area ratio of the oval cross section of the longitudinal runner and of the transverse runner is smaller than the ratio for a runner with a rectangular cross section of the same area. The method may be used to calculate the in-gate area. Cold shuts and gas entrapment during the molding process are reduced, enhancing the quality of the thin-walled shell and raising the efficiency of the design process.

What is claimed is: 
     
         1 . A die-casting mold structure for a thin-walled shell of an electrical connector, comprising:
 a mold cavity;   an overflow; and   a runner structure that provides a path for a liquid metal to flow into the mold cavity and the overflow;   wherein an area of the cross section of the runner structure is progressively smaller in a direction of flow of the liquid metal, and wherein the cross section of a part of the runner structure has a perimeter-to-area ratio smaller than a perimeter-to-area ratio of a rectangular or a square cross section of the same area.   
     
     
         2 . The die-casting mold structure of  claim 1 , wherein the runner structure comprises a longitudinal runner, a transverse runner, an end runner, and an in-gate, wherein the longitudinal runner, the transverse runner, the end runner, and the in-gate are connected sequentially, and wherein the end runner connects to the mold cavity at the in-gate. 
     
     
         3 . The die-casting mold structure of  claim 2 , wherein the cross section of the longitudinal runner is oval or circular, and the cross section of the transverse runner is oval or circular. 
     
     
         4 . The die-casting mold structure of  claim 2 , wherein the longitudinal runner and the transverse runner are connected by a first curved runner, the transverse runner and the end runner are connected by a second curved runner, and the end runner and the in-gate are connected by a third curved runner. 
     
     
         5 . The die-casting mold structure of  claim 4 , wherein each of the first curved runner, the second curved runner, and the third curved runner is an arc-shaped structure. 
     
     
         6 . The die-casting mold structure of  claim 5 , wherein the first curved runner has a radius of curvature R1 greater than 0.45*L1 and less than 0.7*L1 (0.45 L1<R1<0.7 L1), the second curved runner has a radius of curvature R2 greater than 0.4*L2 and less than 0.6*L2 (0.4 L2<R2<0.6L2), and the third curved runner has a radius of curvature R3 greater than 0.3*L2 and less than 0.5*L2 (0.3 L2<R3<0.5L2), wherein L1 is the length of the transverse runner, and L2 is the length of the end runner. 
     
     
         7 . The die-casting mold structure of  claim 2 , wherein the height H of the in-gate is between 0.2 and 0.5 of the area of the in-gate. 
     
     
         8 . The die-casting mold structure of  claim 2 , wherein the mass of the thin-walled shell in the mold cavity is twice the mass of the metal in the overflow, and wherein a quadratic function describes a relationship between the area A of the in-gate, and the sum G of the mass of the thin-walled shell in the mold cavity and the mass of the metal in the overflow. 
     
     
         9 . The die-casting mold structure of  claim 8 , wherein the quadratic function is A=0.8948+0.4292*G−0.01040*G 2 , wherein A is in unit of mm 2 , and G is in unit of g. 
     
     
         10 . The thin-walled shell cast from the die-casting mold structure of  claim 1 , wherein the metal of the thin-walled shell is an alloy that has a density ρ of 6.8 g/cm3. 
     
     
         11 . The thin-walled shell cast from the die-casting mold structure of  claim 1 , wherein the thin-walled shell is thinner than 1 mm. 
     
     
         12 . A method for die-casting a thin-walled shell of an electrical connector, comprising configuring a runner structure that provides a path for a liquid metal to flow into a mold cavity and an overflow, wherein an area of the cross section of the runner structure is progressively smaller in a direction of flow of the liquid metal, and wherein the cross section of a part of the runner structure has a perimeter-to-area ratio smaller than a perimeter-to-area ratio of a rectangular or a square cross section of the same area. 
     
     
         13 . The method of  claim 12 , wherein said configuring comprises configuring the runner structure to have a longitudinal runner, a transverse runner, an end runner, and an in-gate, wherein the longitudinal runner, the transverse runner, the end runner, and the in-gate are connected sequentially, and wherein the end runner connects to the mold cavity at the in-gate. 
     
     
         14 . The method of  claim 13 , wherein said configuring further comprises:
 configuring the cross section of the longitudinal runner to be oval or circular; and   configuring the cross section of the transverse runner to be oval or circular.   
     
     
         15 . The method of  claim 13 , wherein said configuring further comprises:
 connecting the longitudinal runner and the transverse runner by a first curved runner;   connecting the transverse runner and the end runner by a second curved runner; and   connecting the end runner and the in-gate by a third curved runner.   
     
     
         16 . The method of  claim 15 , wherein said configuring further comprises:
 configuring the first curved runner to be an arc-shaped structure having a radius of curvature R1 greater than 0.45*L1 and less than 0.7*L1 (0.45 L1<R1<0.7 L1);   configuring the second curved runner to be an arc-shaped structure having a radius of curvature R2 greater than 0.4*L2 and less than 0.6*L2 (0.4 L2<R2<0.6 L2); and   configuring the third curved runner to be an arc-shaped structure having a radius of curvature R3 greater than 0.3*L2 and less than 0.5*L2 (0.3 L2<R3<0.5 L2), wherein L1 is the length of the transverse runner, and L2 is the length of the end runner.   
     
     
         17 . The method of  claim 13 , wherein said configuring further comprises configuring the height H of the in-gate to be between 0.2 and 0.5 of the area of the in-gate. 
     
     
         18 . The method of  claim 13 , further comprising:
 setting the mass of the thin-walled shell cast in the mold cavity to be twice the mass of the metal in the overflow;   calculating the sum G of the mass of the thin-walled shell cast in the mold cavity and the mass of the metal in the overflow; and   calculating the area A of the in-gate from the sum G using a quadratic function that describes a relationship between the area A of the in-gate and the sum G.   
     
     
         19 . The method of  claim 18 , wherein the quadratic function is A=0.8948+0.4292*G−0.01040*G 2 , wherein A is in unit of mm 2 , and G is in unit of g. 
     
     
         20 . The method of  claim 12 , wherein the metal for die-casting the thin-walled shell is an alloy that has a density β of 6.8 g/cm3.