| 摘要 |
PURPOSE:To make it possible to freely adjust an air quantity without increasing noise in a fan, by providing an inner cylinder, having a certain clearance toward an outer cylinder, movably in the cylinder axis direction, inside the outer cylinder fixed on a casing. CONSTITUTION:An outer cylinder 4 fixed on a casing 3 is provided at the suction port of a fan, and an inner cylinder 5 movable in the cylinder axis direction, and having a certain clearance 6 toward the outer cylinder 4, is provided in said outer cylinder 4. When overlapping parts of the inner and outer cylinders 4, 5 are shortened, gas flows from the clearance 6 under the induced effect being generated by a current in the inner cylinder 5, while, when overlapping parts of both cylinders 4, 5 are made longer by shifting the inner cylinder in the axis direction, the passage resistance in the clearance 6 is enlarged, so that only the current in the inner cylinder 5 is sucked by an impeller 1. With this arrangement, it is possible to adjust an air quantity, but the current becomes axially symmetric at all times so as to prevent the occurrence of turbulence, thereby noise can not be generated.
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