Abstract: A mouth piece unit (6) for a semi-closed type breathing device (1) in which when pressing down a start button (102), the entirety of a movable assembly (70) moves and an external opening (73) opens, whereby a mouth piece (62) is caused to protrude, allowing a diver to hold it in his/her mouth. Since the movable assembly (70) is held at that position even if the start button (102) is restored, an inhalation gas supply valve (21) is held in an open state by an engagement bar (74), whereby the supply of inhalation gas is continued. When the mouth piece (62) comes out of the mouth of the diver, the movable assembly (70) is restored and the external opening (73) is automatically closed, thereby preventing water from entering the inside therethrough from the outside.

Abstract: A mouthpiece unit (6) of a semiclosed-circuit breathing apparatus (1) includes a inhaled/exhaled air circulation chamber (61), an inhalation gas supply opening (71) for providing a constant flow of fresh breathing gas from a breathing gas cylinder, a mouthpiece (62) attached to an external opening (65), and manually operated members (75, 76) that are maintained at an initial position by a resilient force and can be moved to a first operating position against the resilient force. In an interlocking operation, movement of the manually operated members to the first operating position is accompanied by opening of an external opening (65) by a valve (101). A first lever (73) opens and closes the gas supply opening (71) in conjunction with the opening and closing operation of the valve (101).

Abstract: The constituent parts of a semiclosed respirator (1) are all set in a housing (2). When a push button (616) of a mouthpiece unit (6) is pressed with a chewing piece (617) held between upper end lower teeth, the supplying of a gas to be inhaled, which flows at a predetermined flow rate, through a gas supply pipe (84) is started. When an control lever (633) is pressed, a large quantity of gas is supplied through a gas supply pipe (85), end the removal of water from the mouthpiece unit is carried out. A carbon dioxide adsorption device (7) is of a so-called cartridge type held detachably in a container (3), and can be replaced by a new one easily. A large quantity of gas is supplied automatically in an emergency from a gas supply pipe (86) to an inhalation air passage (32), and an auto-valve mechanism (12) adapted to discharge a gas automatically when the inner pressure of the respiration passage has increased is provided thereon.