Negative pressure dust collector with a dust receiving bag smoothly inflatable

A negative pressure dust collector with a dust receiving bag smoothly inflatable, said negative pressure dust collector comprising a ventilation hood that is provided with a motor positioned on its top, plural fan blades positioned inside said ventilation hood for pivotally connected with said motor, a suction tube vertically fixed under said fan blades, a first exit formed in a bottom of said ventilation hood, a dust collection tank positioned just under said first exit and provided with a dust receiving bag put inside it for receiving comparatively heavy dust particles, a second exit formed at an upper tight side, an inlet formed at a left side of said ventilation hood, a dust collecting bag connected with said second exit, said dust collector characterized by:

• an exhaust device composed of a ventilation tube and a flexible tube, said ventilation tube inserted in said ventilation hood through a through hole bored in an intermediate right side wall of said ventilation hood with some portion remained outside said ventilation hood, an annular fixing base fixed around said ventilation tube for threadably combining with a wall of said ventilation hood, said ventilation tube being obliquely positioned with a certain angle and having an exit at an upper end to approximately face to a center of an opening of said suction tube of said ventilation hood and an outlet formed in a lower wall, said flexible tube installed outside said ventilation hood and having its upper end connected with said inlet of said ventilation tube to communicate with said ventilation tube and a lower end jointed with an outer wall of said dust collection tank to communicate with said dust collection tank.