| 摘要 |
PURPOSE:To suitably prevent cement accumulated in a chute from scattering, by providing a flexible member between an extendable pipe and a short pipe so that it is made into contact with both pipes, by displacing the surface of this extendable pipe with the use of blow and suction air to maintain air-tightness for the chute. CONSTITUTION:By stopping a fan for ventlating in an outer pipe 5 (extendable pipe) is a valve V1 is opened and a valve V2 is closed before a winder is actuated to blow air from an air pressure supply source 25 to fill air in a space C. Thereby a flexible plate 19 is displaced to a position indicated by two-dot chain line 19a due to the blowing amount of air and the pressure thereof. In this position the flexible plate 19 is made into close contact with a short pipe 8 in a dust-free chute 4 to vertically shut off the communication between the areas A, B in a space between the dust-free chute 4 and the outer pipe 5. As a result, even though cement dust accumulated on the inner wall surface 17 of the outer pipe 5 drops due to vibration and air stream which are generated when the dust- free chute 4 is subsequently displaced with its entirety, the cement dust is accumulated and trapped on the flexible plate 19 at the position 19a, thereby the dust is prevented from dropping and scattering. |
