| 摘要 |
PURPOSE:To prevent the static pressure from decreasing and the noise of a duct ventilating fan main body from increasing even when its impeller is reduced in width to reduce the input to the duct ventilating fan. CONSTITUTION:A casing of a duct ventilating fan includes an exterior frame 6, an electric motor 8, an upper casing 9, a side casing 11 and an orifice plate 12. The exterior frame 6 is a box having a suction port 2 on the bottom, a delivery port on the side and a motor base 5 inside. The motor 8 is mounted on the motor base 5 and an impeller 7 is attached at the lower end. The upper casing 9 covers over the impeller 7 and the side casing 11 having a tongue 10 covers around the periphery of the impeller 7. The orifice plate 12 is in contact with the lower edge of the side frame 11 and introduces air to the impeller 7. The casing has such a depth that the upper casing 9 is accommodated in the casing with a clearance left between the upper edge of the impeller 7 and a ceiling plate 4 of the exterior casing 6 so that the impeller 7 is prevented from coming in contact with the ceiling plate 4. |
