Summary description: Automatic unloading start valve: It is used in the Plumbing of Roots blower. When the blower starts, the transported gas flows into the outside through the unloading valve, and the blower starts at a slight load. At the same time, due to the pressure difference between the gas in the pipeline and the external atmosphere, the starting valve slowly closes, allowing the transported gas to flow into the normal working pipeline. The micro load start of the blower has been achieved, avoiding the impact on the main body of the equipment, the impact on the driving equipment, and the damage to the transmission mechanism caused by direct load start. Avoiding the cumbersome and malfunctioning caused by the use of bypass, electric valves or actuators, and then being controlled by electrical control equipment.