Injection molding apparatus for shoe or sole using thermoplastic resin and thereby shoes

1. An injection foam molding apparatus for manufacturing a one-piece shoe or sole having various colors, hardnesses and specific gravities, using ethylene-vinyl acetate (EVA) ethylene-poly olefin compounds and thermoplastic resins, the apparatus comprising:

a top mold including a molding space having a shape corresponding to an upper part of a shoe or sole;

a bottom mold including a molding space having a shape corresponding to a lower part of the shoe or sole;

a middle mold configured to be located between the top mold and the bottom mold and to separate the two molding spaces of the top mold and bottom mold from each other;

a resin supply unit configured to supply different thermoplastic resins into the molding space defined between the top mold and the middle mold and the molding space defined between the middle mold and the bottom mold, respectively;

a transfer unit configured to

move the middle mold into a space between the top mold and the bottom mold, and

remove the middle mold from the space between the top mold and the bottom mold; and

a pressing unit configured to press the thermoplastic resins charged in the molding spaces by moving the top mold downward and bottom mold upward,

wherein

the resin supply unit is configured to inject the thermoplastic resins into the molding spaces of the top mold and bottom mold in a state in which the top mold and bottom mold are coupled with the middle mold, and then

the pressing unit is configured to press the top mold and the bottom mold against the middle mold to form the upper part and lower part of the shoe or sole, and then

the transfer unit is configured to separate the middle mold from the top mold and bottom mold, and then

the pressing unit is configured to press the top mold and bottom mold, including the formed upper part and lower part of the shoe or sole, to each other, thereby forming the upper part and lower part of the shoe or sole into one body,

wherein the top mold comprises a moving core for forming an inner shape of the shoe,

wherein the moving core is moveable upward and downward in the molding space of the top mold, and the moving core is coupled with a spring for biasing the moving core downward,

wherein the transfer unit is further configured to

be contacted with protrusions which are provided on a side surface of the middle mold, and

move the middle mold forward, backward, upward and downward while the middle mold is supported by the protrusions,

wherein the moving core comprises a rod-shaped moving member which is integrally provided on an upper portion of the moving core and is coupled to the spring, and the moving member is inserted into a through-hole formed in an upper portion of the top mold,

wherein the moving member is configured to move upward and downward along the through-hole in the top mold, and the moving core is configured to move upward and downward integrally with the moving member.

2. The injection foam molding apparatus according to claim 1 , wherein

an upper spring support end is integrally provided on an upper end of the moving member, and a lower spring support end is provided below the upper spring support end to be stopped by an upper surface of the top mold while being fitted over the moving member in such a way as to permit upward and downward movement of the moving member, and

the spring is mounted on the moving member in such a way as to be positioned between the upper spring support end and the lower spring support end.

3. The injection foam molding apparatus according to claim 1 , wherein the top mold is provided at one side thereof with a holding unit for preventing the moving core from being displaced upward and downward.

4. The injection foam molding apparatus according to claim 1 , wherein the thermoplastic resin is one or more selected from among olefin resins, ethylene-vinyl acetate (EVA), ethylene-octene copolymer, ethylene-butene copolymer, Engage, Tafmer, and combinations thereof.

5. The injection foam molding apparatus according to claim 1 , wherein the thermoplastic resin that is injected and foamed has a hardness of about 70C˜20C, which is measured using a Asker-C type hardness tester, which is an international hardness tester, and a specific gravity of 0.30 g/cm 3 ˜0.10 g/cm 3 .

6. The injection foam molding apparatus according to claim 1 , wherein the thermoplastic resin is cross-linked for 2˜20 minutes on condition that a temperature of a screw of the resin supply unit for supplying the resin is 40˜150° C., and a temperature of the molds is 120˜200° C.

7. The injection foam molding apparatus according to claim 1 , wherein

the top mold is engraved in intaglio to have a shape corresponding to that of an upper part of the one-piece shoe and an upper part of the sole, and

a space of the top mold engraved in intaglio forms the molding space in the top mold and is configured to be sealed by the middle mold.

8. The injection foam molding apparatus according to claim 7 , wherein an upper surface of the middle mold, which is configured to be coupled to the top mold, has a shape corresponding to that of a lower surface of the upper part of the one-piece shoe.

9. The injection foam molding apparatus according to claim 1 , wherein

the bottom mold is engraved in intaglio to have a shape corresponding to that of a lower part of the one-piece shoe, and

a space of the bottom mold engraved in intaglio forms the molding space in the bottom mold and is configured to be sealed by the middle mold.

10. The injection foam molding apparatus according to claim 9 , wherein a lower surface of the middle mold, which is configured to be coupled to the bottom mold, has a shape corresponding to that of an upper surface of the lower part of the one-piece shoe.

11. The injection foam molding apparatus according to claim 1 , wherein the transfer unit comprises a rail, so that the middle mold is placed on the rail to be moved along the rail.