To provide a bottom valve for a tank truck which can be easily opened/closed because of the excellent operability in such an emergency that troubles have arisen in the outside air devices and which can rapidly cope with the suspension of unloading or the like and by which these can be realized in a simple constitution.
The bottom valve of a tank truck is opened/closed by pneumatic forces. An emergent air circuit 45 with the second changeover valve 44 of an emergent device 43 can be connected in parallel with the first changeover valve 40 interposed, in the air piping 37 between the air source 38 and the air inlet/ outlet 25 of the air pipes. The emergent device 53 is ordinarily separately contained and the emergent air circuit 45 is connected in such an emergency when troubles have arisen in the first changeover valve 40 or the upstream or downstream air pipes 37 on unloading and the bottom valve is opened/closed. Both ends of the emergent air circuit 45 are respectively connected to a three- way valve 39 side at the upstream side of the air piping 37 and a shuttle valve 41 side at the downstream side, for instance.
SATO KIYOTERU
WATANABE HIROSHI
SUGANO TOKIO
