To securely maintain the sealing property of a chute and a valve element by making a diameter of a bottom circle of the valve element having a conical shape larger than a diameter of a circular discharge port of the chute and connecting a top part of the valve element through a free connection mem ber to lift and lower it.

A valve element 14 is made of cast iron or cast steel and has conical shape, and a diameter D of a bottom circle 11 in a bottom part is larger than a diameter d of a circular discharge port 13 of a chute 12 so that a material is discharged and passes or the material is stored temporarily. Moreover, it is connected with a top part of the valve element 14 through a free joint 15 and has an air cylinder 16 which lifts and lowers the valve element 14 for the circular discharge port 13. The circular discharge port 13 of the chute 12 and a side face 23 of the valve body 14 are sealed by a metal touch structure. Furthermore, this metal touch is constituted in such a manner that a part of the chute 12 in contact with the valve element 14 of the circular discharge port 13 is formed like an edge. For this reason, the sealing property is improved, and the occurrence of troubles due to clogging and catching of the material is reduced.