| 摘要 |
PROBLEM TO BE SOLVED: To enhance suction performance and propulsive forces by providing a screw blade having a series of continuous twisted blade faces in a coned flow passage. SOLUTION: This device has a helical screw blade 14 wound on a conical hub 13 from the start end to the intermediate stage of a coned pump casing 4, the hub 13 being fastened to a driveshaft 11 extending from the coned pump casing 4. A guide blade 15 is connected to the rear stage of the pump casing 4 and water flowing into the pump casing 4 is continually pressurized by a series of blade faces. The overall length L of the hub with the screw blade 14 wound thereon is made greater than the bore D1 of the suction opening of the pump casing 4 to pressurize and increase the speed of water flow in a helical centrifugal direction so as to generate high thrust by means of the speed of ejection and generate inducer action at the suction part of the screw blade. This prevents cavitations and a plurality of screw blades wound on the hub are placed with their outer peripheries brought close to the inner peripheral surface of the pump casing, and with the ends of the outer peripheries extended into a suction casing so as to prevent floating objects from clogging the suction parts of the screw blades.
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