To prevent water leakage in case of breakage of a pressure- displacement conversion element.
In a pressure reducing valve 1, a ventilation path 29 communicating with the outside is provided to a spring room 3 sealed in watertight by a pressure-displacement conversion element 13 and a spring cover 4, a floating bar 33 whose top and bottom ends are projected from upper and lower openings 29a and 29b is freely passed through the ventilation path 29, a water leakage preventing valve 34 to open and close the lower opening 29b is provided with the floating bar 33, a fallout preventing piece 36 of the floating bar 33 on the upper end side of the floating bar 33 forming an air vent 35 to make the spring room 3 communicate with the outside through the ventilation path 29 when the preventing valve 34 is opened, usually air flows into the spring room 3 by opening the preventing valve 34 as not to vary an inner pressure in the spring room 3 even due to temperature fluctuations. The preventing valve 34 is closed by pressurized water flowing from a secondary side pressurized room 9 through the spring room 3 to prevent the water leakage in case of the breakage of the conversion element 13.
WATANABE TAKANORI
IWAMOTO HOMARE
