REDUCING VALVE

PURPOSE:To provide a reducing valve used in a respiratory device which can prevent generation of noise at the time of decompression by forming concave- convex portions on the inner wall adjacent to a valve seat of a passage to cause an eddy in gas. CONSTITUTION:Air flowing from a passage 72 into a valve chamber 76 is conducted from a passage 83 through a pressure chamber 89 to an air duct 7a. When the pressure in the pressure chamber 89 rises, a valve body 82 is lowered against a spring 88 and brought into contact with a valve seat 80 to keep airtightness. When air is discharged by inhalation of air to lower the pressure in the pressure chamber 89, the valve body 82 is raised so that high-pressure air in the valve chamber 76 is decompressed to flow into the passage 83. The inner wall adjacent to the valve seat 80 of the passage 83 is provided with concave- convex portions 103 formed thereon to cause an eddy in gas flowing from the valve chamber 76 into the passage 83.