PURPOSE: To obtain an air tube to a turn bar in which disturbance with an air hose does not occur and which can be remotely controlled by forming the tube for supplying the air to the bar at an expansion conduit in the moving direction of the bar.

CONSTITUTION: Turn bars 3a, 3b, 3c, 3d are connected to a header 8 having switching valves 9a, 9b, 9c, 9d by expansion conduits 11a, 11b, 11c, 11d in the moving direction of a turn bar. The conduits 11a-11d are formed of a fixed cylinder L having the maximum inner diameter, an intermediate moving cylinder M having an intermediate diameter engaged with the cylinder L and moving while holding airtightness, and a minimum moving cylinder N engaged with the cylinder M and having the minimum inner diameter moving while holding the airtightness. The cylinder 1 is connected to the header 8 via the valves 9, the cylinder N is connected to a block 7. Thus, the conduits are linearly extended to the moving direction of the bar and do not disturb the feeding of a web and the moving of the bar by linearly extending it in the moving direction of the bar, and hence the movement is smooth and easy to be controlled at the moving position, and conducted automatically without hand by a remote operation.