Abstract: A dust-collecting device of a secondary dust-collecting machine includes a wind guide barrel having a wind intake and a bottom disposed with a dust-collecting barrel. The wind guide barrel further has its topside mounted with a wind duct installed thereon with a blowing fan and connected with a dust-collecting box, which has a plurality of centrifugal type dust collectors set therein. Thus, outside dust accompanying air can be sucked into the wind guide barrel through the wind intake by the suction of the blowing fan to have the dust with comparatively large diameter first collected by the dust-collecting barrel. Then, the remaining dust with lighter mass will be collected for a second time by the centrifugal type dust collectors and filtrated by the filter screen for completely filtrating and removing the dust from the operation environment.

Abstract: A negative pressure dust collector with a dust receiving bag comprises a ventilation hood and an exhaust device. The ventilation hood includes a motor, fan blades, and a first exit. A dust collection tank is positioned below the first exit. The exhaust device comprises a ventilation tube and a flexible tube.

Abstract: A negative pressure dust collector with a dust receiving bag smoothly inflatable includes a ventilation hood and an exhaust device. The ventilation hood has a motor fixed on its top, fan blades confined in it to connect with the motor, and a first exit formed at its bottom. A dust collection tank is positioned below the first exit, having its interior put with a dust receiving bag. The exhaust device includes a ventilation tube fixed in the ventilation hood, and a flexible tube connected with the ventilation tube and positioned outside the ventilation hood. The flexible tube is connected with the dust collection tank so that the air existing between the inner wall of the dust collection tank and the dust receiving bag can effectively be sucked out to keep the dust receiving bag inflated to closely contact the inner wall of the dust collection tank.