Adjustable negative pressure suction tube

According to the adjustable negative pressure suction tube, a double-layer filter screen is arranged in the front end of the suction tube, an adjusting hole is formed in the upper middle portion of the suction tube, a limiting cylinder matched with the adjusting hole is arranged on the outer ring of the adjusting hole, and an adjusting assembly is arranged at the position, at the adjusting hole, of the suction tube; the adjusting assembly comprises an adjusting frame and an adjusting block capable of being inserted into the adjusting hole, the adjusting frame is arranged on the outer wall of the suction tube, the top face of the adjusting frame is an inclined face and is provided with a strip-shaped groove, and an adjusting rod extending into the adjusting frame is movably arranged on the strip-shaped groove. The top end of the adjusting rod is provided with a pushing block which can slide by clinging to the top surface of the adjusting frame; a pressing rod is hinged to the inner side wall of the adjusting f