Су астына тыныс алу аппаратының алғашқы үлгісі

Original name for open circuit scuba equipment

Aqua Lung was the first open circuit, self contained underwater breathing apparatus (or "scuba") to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin hose diving regulator, or demand valve. The Aqua Lung was invented in France during the winter of 1942–1943 by two Frenchmen: engineer Émile Gagnan and Jacques Cousteau, who was a Naval Lieutenant It allowed Cousteau and Gagnan to film and explore underwater more easily. The invention revolutionised autonomous underwater diving by providing a compact, reliable system capable of a greater depth range and endurance than its precursors, and was a major factor influencing the development of recreational scuba diving after WWII. The twin hose Aqua Lung demand regulator is the foundation of all modern scuba regulators. A diaphragm is used to control a valve to deliver the breathing gas to the diver on demand, at ambient water pressure. However, the layout has changed to a single hose system, where the second stage is split from the first stage along with the exhaust valve, as they must be kept at the same depth, and repositioned at the diver's mouth, eliminating the need for the exhaust hose, and allowing the use of a more rugged, smaller bore hose for the intermediate pressure gas supply to the second stage valve at the mouthpiece, but increasing the load on the diver's jaw and releasing bubbles nearer the eyes and ears.

The Aqua Lung is a self contained open circuit demand system, which means that breathing gas is provided from high pressure storage carried by to the diver on demand, when the diver inhales and reduces the pressure in the supply hose, and the flow is shut off when not required, and that once breathed, the exhaled gas is vented to the surroundings. Scuba systems invented before the Aqua Lung were mostly closed circuit rebreather equipment, in which breathing gas flows through an ambient pressure hose to the diver, and exhaled gas is returned through a scrubber which removes carbon dioxide, to a counter lung reservoir. Some fresh gas is added to maintain the oxygen content and is then circulated back to the diver again in a closed loop. In open circuit free flow systems, the air is supplied at an approximately constant rate, and the diver uses only a relatively small part of the passing gas. The original Aqua Lung regulator was a single stage unit, packaged in a circular brass housing mounted on the cylinder valve behind the diver's neck. High pressure gas flows into the regulator from the cylinder valve outlet, and is blocked by the demand valve. When the diver consumes ambient pressure gas, the pressure falls in the low pressure chamber and the diaphragm deforms inwards pushing against the valve lifter. This opens the high pressure valve permitting gas to flow past the valve seat into the low pressure chamber. When the diver stops inhaling, pressure in the low pressure chambers quickly rises until the diaphragm returns to its neutral position and no longer presses on the valve lifter, shutting off the flow until the next breath is taken. On a single stage regulator, the flow rate through the demand valve orifice will vary depending on cylinder pressure for the same opening size, and the opening force required will vary depending on the inlet pressure and orifice area, together making the delivery rate vary as the pressure in the cylinder changes. Flow rate is also affected by downstream pressure, which varies with depth, so the effort of breathing could vary considerably during a dive, even without taking diver attitude into account. After 1884, several companies and entrepreneurs bought or inherited the patent and produced it until 1965. In 1942, during the German occupation of France, the patent was held by the Bernard Piel Company (Établissements Bernard Piel). One of their apparatuses went to Émile Gagnan, an engineer employed by the Air Liquide company. Gagnan miniaturized and adapted it to gas generators in response to a fuel shortage, which was a consequence of German requisitioning. Gagnan's boss, Henri Melchior, knew that his son in law Jacques Yves Cousteau was looking for an automatic demand regulator to increase the useful endurance of the underwater breathing apparatus invented by Commander Yves le Prieur, so he introduced Cousteau to Gagnan in December 1942. On Cousteau's initiative, the Gagnan regulator was modified for use in diving. Cousteau and Gagnan were issued a patent some weeks later in 1943. After the war, in 1946, both men founded La Spirotechnique as a division of Air Liquide in order to mass produce and sell their invention, this time under a new 1945 patent, and known as CG45 ("C" for Cousteau, "G" for Gagnan and "45" for 1945). This same CG45 regulator, produced for more than ten years and commercialized in France as of 1946, was the first to actually be called the "Aqua Lung". In France, the terms scaphandre autonome ("autonomous diving set"), scaphandre Cousteau Gagnan ("Cousteau Gagnan diving set"), or CG45 were meaningful enough for commercialization, but to sell his invention in English speaking countries, Cousteau needed an appealing name following English language standards. He then coined the trade name Aqua Lung. In the late 1940s and early 1950s, La Spirotechnique started exporting the Aqua Lung and leasing its patent to foreign companies like the British Siebe Gorman. The equipment was a great success compared to the Rouquayrol Denayrouze apparatus, which was limited because the technology of its time could only produce compressed air tanks that could hold 30 atmospheres, which allowed dives of only 30 minutes at no more than ten meters depth. Before 1945, French divers preferred the traditional standard diving dress with copper helmet and surface supplied breathing air. When the Aqua Lung became available for commercial use, divers around the world found the Cousteau Gagnan equipment smaller and easier to use than either the Le Prieur or Rouquayrol Denayrouze apparatus. The Aqua Lung could be also be mounted on stronger and more reliable air tanks holding up to 200 atmospheres, allowing extension of diving duration to more than an hour at significant depths, including the time needed for decompression stops. The first Cousteau Gagnan Aqua Lungs (like the CG45 of 1945 or the Mistral of 1955) were twin hose open circuit scuba. Similar configurations have since been made by various manufacturers with varying design details and numbers of cylinders. Like open circuit scuba with single hose regulators, they consisted of one or more high pressure diving cylinders and a diving regulator (the Aqua Lung) that supplied the diver with breathing gas at ambient pressure via a demand valve. For more than ten years, seen in the films Épaves (Shipwrecks, 1943) and Le Monde du silence (The Silent World, 1956) the main scuba equipment used by Cousteau and his divers was an Aqua Lung mounted on three diving cylinders, one being used as a reserve. The Aqua Lung allowed divers to spend more time underwater, and, along with the invention of several underwater cameras, to film and explore more freely.

The Aqua Lung was not the first self contained underwater breathing apparatus, but it was the first to be widely popular. In 1934, René Commeinhes developed a firefighter's breathing apparatus which was adapted for diving as the G. C. 42, and patented in April, 1942 (no.976,590) by his son Georges in 1937. It was used by the French Navy during the first few years of World War II. It was an open circuit system supplied from two 200 bar cylinders, and used a single stage regulator to supply gas to a bag between the two back mounted cylinders at slightly above ambient pressure. The gas was then supplied to the left side of a full face mask by a corrugated rubber hose, and exhausted directly from the right side of the mask. At about the same time as Divers Supply began selling the Sport Diver regulator, Australian Ted Eldred designed a two stage single hose regulator which he marketed in Australia as the Porpoise.