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.
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.
JINNO HIDEKI
KAMEI TAKESHI
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