Patent ID: 7934867

Claim:
A stirring apparatus comprising a stirred tank, a stirring shaft that is disposed within the stirred tank along an axis thereof so as to be rotatable from the outside of the stirred tank, and a flat plate like and generally rectangular shaped stirring impeller that is mounted to the stirring shaft, the stirring apparatus being characterized in that the stirring impeller has plural openings satisfying the following conditions: (i) the ratio of the opening area of the openings in an upper half of the stirring impeller relative to the total area of the upper half of the stirring impeller (the opening ratio in the upper half of the stirring impeller) is from 45 to 80%; (ii) the ratio of the opening area of the openings in a lower half of the stirring impeller relative to the total area of the lower half of the stirring impeller (the opening ratio in the lower half of the stirring impeller) is from 18 to 50%; and (iii) the ratio of the opening ratio in the lower half of the stirring impeller relative to the opening ratio in the upper half of the stirring impeller is from 46 to 56%.