Patent ID: 8087814

Claim:
A batch mixer comprising: a barrel having a sealed chamber with a section comprising two mutually communicated circles which are communicated throughout the length of the chamber; two rotors mounted in the chamber for rotation in a direction of rotation, each of said rotors including at least one rotor blade shaped to cooperate with the inner wall of the barrel to shear a material in the chamber during rotation of the rotors in a rotating direction; a plurality of recessed parts on each of the rotor blade surfaces of at least one of said rotor blades, wherein the plurality of recessed parts are provided only on the leading blade surfaces during the rotation of the rotors in the rotating direction, except at the tip of said rotor blade, wherein each of said recessed parts is elongated along the surface of the rotor blade; a space in each of said rotors for circulating a cooling medium; a material feed opening for feeding the material into the chamber; a material discharge opening provided at an underside of the barrel; means for closing said material feed opening during mixing of the material in the chamber; and means for closing said material discharge opening during mixing of the material in the chamber.