Blender having bi-directionally rotatable blades

A blender having bi-directionally rotatable blades, the blender comprising:

• a container configured to accommodate food;
• a blade assembly including a main blade shaft that has an upper portion coupled to a first blade and a lower portion coupled to a first main coupler so as to rotate in a forward direction and a reverse-rotation blade shaft that has an upper portion coupled to a second blade and a lower portion coupled to a first reverse-rotation coupler so as to rotate in a reverse direction and that has a structure which is coaxial with the main blade shaft and through which the main blade shaft passes;
• a gearbox assembly including a main gear shaft coupled to a second main coupler, which is engaged with the first main coupler, so as to rotate in the forward direction, a plurality of gears configured to convert the forward rotation of the main gear shaft to reverse rotation, a second reverse-rotation coupler configured to transmit the reverse rotation transmitted through the plurality of gears to the first reverse-rotation coupler, and a gearbox housing configured to surround outer sides of the main gear shaft, the plurality of gears, and the second reverse-rotation coupler;
• and
• a case that has the gearbox assembly provided therein and a case upper plate formed to cover an upper portion of the gearbox assembly, the case upper plate being formed so that the second main coupler and the second reverse-rotation coupler pass therethrough,
• wherein the plurality of gears include:
• a main gear coupled to the main gear shaft to rotate in the forward direction;
• a first sub-gear including a main gear engagement portion, which is engaged with the main gear, and a second sub-gear engagement portion, which is formed to have a diameter different from that of the main gear engagement portion, to rotate in the reverse direction;
• a second sub-gear including a first sub-gear engagement portion, which is engaged with the second sub-gear engagement portion, and a reverse-rotation gear engagement portion, which is formed to have a diameter different from that of the first sub-gear engagement portion, to rotate in the forward direction;
• and
• a reverse-rotation gear which is engaged with the reverse-rotation gear engagement portion to transmit the reverse rotation to the second reverse-rotation coupler and which has a structure coaxial with the main gear shaft.