To provide an isolation valve which securely prevents back water from a secondary water passage from reaching a primary water passage.
The isolation valve 20 is equipped with a pressure detection chamber 22 and a fluid pass chamber 23 which are partitioned with a bellowphragm 27. The fluid pass chamber 23 is equipped with a valve main body 21 which is divided into a front chamber 23A and a rear chamber 23B by a partition wall 24 having a connection port 24A. If the back water tends to intrude into the valve main body 21, the pressure in the front chamber 23A becomes almost the same or more than that in the pressure detection chamber 22, the bellowphragm is moved to a primary pressure receiving port 26 side. The valve element 31 opens an exhaust port 32 and closes the connection port 24A. The back water is drained from an outlet port 33 through an exhaust port 32 thereby. Since the connecting port 24A is closed by the valve element 31 at that time, the back water does not flow into the front chamber 23A, that is, the situation where the secondary side water and the primary side water contact each other, is surely avoided and the isolating operation to the back water is securely performed.
COPYRIGHT: (C)2004,JPO
Yoshito Saai
Kazuhiko Muto
Kenji Ohashi
Shinichi Otani
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