Injection molding apparatus

An injection molding apparatus comprising:

• a mold including a lower-side mold and an upper-side mold configured to form a cavity with the lower-side mold;
• a vertical injection cylinder having an upper portion, a lower portion and a nozzle disposed in a lower end of the lower portion, the injection cylinder configured to receive stick-shaped molding materials sequentially supplied in line from an upper end of the upper portion;
• a heater configured to generate a temperature gradient in the lower portion of the injection cylinder such that the temperature increases from above to below inside the lower portion of the injection cylinder, thereby changing sequentially molding material of the stick-shaped molding materials supplied in the injection cylinder from solidification to a completely molten state;
• and
• a push-in shaft having a main portion and an operating portion that contacts the molding material, a width of the main portion being substantially the same as a width of the operating portion, the push-in shaft configured to push the molding material downward in the injection cylinder,
• wherein the molding material in the upper portion and an upper end of the lower portion of the injection cylinder remains solidified and the molding material in the lower end of the lower portion of the injection cylinder is completely molten,
• when the push-in shaft is inserted into the injection cylinder and the solidified molding material in the upper portion and the upper end of the lower portion of the injection cylinder is pushed by the push-in shaft, a gap is formed between an outer surface of the push-in shaft and an inner surface of the injection cylinder and the completely molten molding material in the lower end of the lower portion of the injection cylinder is injected such that an airtight stopper is formed in a space between the molding material in a middle level of the lower portion of the injection cylinder and the inner surface of the injection cylinder at the middle level due to a half-molten state of the molding material in the middle level of the injection cylinder, and
• heat is transmitted from the injection cylinder to the mold through a nozzle touch from the nozzle.