Air duct telescopic device for tunnel construction

The invention provides an air duct telescopic device for tunnel construction, which is characterized by comprising a transmission device, an air duct telescopic device and an air duct telescopic device, the driving rod is connected with the transmission device; the first transmission box comprises a first gear and is connected with the driving rod; the second transmission box comprises a second gear; the belt ring is connected to the gear rings of the first gear and the second gear at the same time and rotates along with the gears for transmission; the track is fixedly connected between the first transmission case and the second transmission case; the belt ring is driven along the track; the pulley is arranged on the belt ring and is in synchronous transmission with the belt ring; the air duct is connected with the pulley; the upper end of the air duct is connected with the track, and the air duct can slide along the track and can telescopically move. The air duct expansion device is convenient to operate, si