| 摘要 |
A housing 14 forms, together with a cover 34, an annular vortex chamber 42. An impeller 22 is provided with a disk portion 24 which is connected to a drive shaft 12 so that the impeller 22 rotates integrally with the shaft 12. The impeller 22 has an annular support portion 26 and rows of angularly-spaced blade portions 28 and 30 arranged along the circumference of the impeller. The blade portions 28 and 30 are located in the vortex chamber 42. A seal portion is created between the impeller 22, the housing 14 and the cover 34, which seal portion is constructed by inner axial slits 72A and 72B formed between axially-spaced surfaces transverse to the axis of the shaft 12, radial slits 74A and 74B formed between radially spaced-apart cylindrical surfaces, and outer axial slits 76A and 76B formed between axially spaced-apart surfaces transverse to the axis of the shaft 12. The thickness of the radial slits 74A and 74B is smaller than a half of the thickness of at least one of the inner or outer axial slits, and the length of the radial slits 74A and 74B is between 2 mm and 5 mm.
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