"A breathing system for divers includes a breathing bag (211) from which the inhalation gas to the diver is delivered and to which the exhalation gas from the diver is supplied, a compressed gas source for the supply of breathing gas, and a pneumatic cylinder/piston unit (308, 209) operatively connected to the compressed bag source and having the piston (209) coupled to the breathing bag (211) to contract or expand the bag. A sensor responds to pressure variations in the breathing gas caused by the diver's inhalation and exhalation, and causes at least two valves and associated controls (173-205) to switch the compressed gas source to either side of the piston (209) in the pneumatic cylinder (208). The valves (176, 177) ensure that the breathing gas to and from the diver is maintained at a pressure approximately equal to the ambient pressure. When the sensor particularly comprises a diaphragm (170), the valve controls may be arranged to provide for increasing or decreasing the high-pressure gas flow supplied to the pneumatic cylinder (208) in dependence on the extent of movement of the diaphragm (170) in the direction in question.
展开▼
