| 摘要 |
PROBLEM TO BE SOLVED: To surely fasten impellers and dispense with a key or reduce the use of the key by forming the serrations on the hub inner diameter parts of the impellers and an outer diameter part of a rotary shaft, and fastening the impellers to the rotary shaft by the engagement of these serrations. SOLUTION: A plurality of impellers 2A-2D are arranged in series on a rotary shaft 1 supported by the bearings at its both ends. The impellers are fastened in a state that each hub inner diameter part of the impeller 2 is engaged with or fitted to an outer diameter of the rotary shaft 1. The rotary shaft 1 is provided with the peripheral serrations S1, S2. A first stage impeller 2A and a second stage impeller 2B respectively counted from a left side, are fastened to the rotary shaft 1 in the serration S1. Similarly a third stage impeller 2C and a fourth stage impeller 2D counted from the left side, are fastened to the rotary shaft 1 in the serration S2. Among them, the first and third stage impellers 2A, 2C are respectively fastened by the serrations S1, S2 mounted on the back side thereof.
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