Underwater aeration device

A submersible aerator including an impeller which is rotated by a motor and draws air and liquid simultaneously from different locations so as to mix the air and the liquid at a peripheral edge of the impeller, wherein a boss portion of the impeller is attached to an end of a motor shaft extending downward from the motor and penetrating into an air chamber;

• an intermediate plate having an air suction opening at the center thereof is attached to a top wall of a guide casing such that the intermediate plate faces an upper surface of a peripheral portion of a circular main plate of the impeller extending radially outward from the boss portion;
• a suction cover having a liquid suction opening at the center thereof is attached to a bottom wall of the guide casing such that the suction cover faces lower end surfaces of blades of the impeller;
• a plurality of guide vanes are provided on an upper surface of the suction cover such that a clearance is left between the guide vanes and a peripheral edge of the impeller;
• guide passages defined between the guide vanes guide an air-liquid mixture discharged from the impeller to air-liquid discharge passages of the guide casing, whereby the air-liquid mixture is jetted outward through the air-liquid discharge passages;
• an air chamber communicating with an air conduit extending downward from the atmosphere above a liquid into which the guide casing is immersed is provided above the guide casing in order to introduce air from the atmosphere above the liquid into which the guide casing is immersed;
• the impeller, which is rotated by the motor, is accommodated within the guide casing such that the impeller can rotate between a lower surface of the intermediate plate and the upper surface of the suction cover;
• the plurality of blades are provided on the main plate of the impeller such that the blades project toward the upper surface of the suction cover with a predetermined clearance left therebetween, and radially inner ends of the blades face the liquid suction opening, whereby liquid passages are defined between the blades such that the liquid passages communicate with the liquid suction opening and extend radially outward;
• a groove is provided in each blade such that the groove extends from the periphery of the boss portion of the impeller toward the periphery of the impeller so as to define air passages which communicate with the air chamber, which extend radially outward, and which are open at radially outer ends thereof;
• the blades have partition walls which separate the liquid passages and the air passages from each other;
• and the liquid passages and the air passages meet through communication portions at the radially outer ends of rear-side blade partition walls, which are partition walls of the blades which are located rearward with respect to the rotational direction of the motor and which do not receive pressure.