Aqua-Lung
Aqua-Lung[1] was the first open-circuit, self-contained underwater breathing apparatus (or "scuba") to achieve worldwide popularity and commercial success.
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.
When the diver consumes gas from the second stage, the pressure falls in the interstage chamber and the diaphragm deforms inwards pushing against the valve lifter.
When the cylinder pressure was running low and air demand effort rising, a roll to the right side made breathing easier.
The Rouquayrol-Denayrouze apparatus went into mass production and commercialization on 28 August 1865, when the French Navy Minister ordered the first units.
Gagnan miniaturized and adapted it to gas generators in response to a fuel shortage, which was a consequence of German requisitioning.
[9] 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).
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.
[10] 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 also could be mounted on stronger and more reliable air tanks holding up to 200 atmospheres,[11] allowing extension of diving duration to more than an hour at significant depths, including the time needed for decompression stops.
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.
An advertisement in Popular Mechanics of October 1950 offered a single hose regulator for sale by Divers Supply in Wilmington, California.
[16] Virtually all modern open-circuit scuba regulators use the single-hose two-stage design, though Aqualung did market a modernised twin-hose Mistral model in 2005 and 2006.
This turned out to be a wise move, because when the French company decided not to renew his five-year contract, no one had even heard of their product, but everyone was familiar with the names he had registered.
In France, aqualung diving was popularized by Cousteau's movie Épaves, while his book The Silent World also helped significantly.
Presumably, lawyers for Cousteau or Air Liquide could have slowed or stopped this genericization by taking prompt action, but this seems not to have been done in Britain, where Siebe Gorman held the British rights to both the trade name and the patent.
The word "aqualung" was commonly used in speech and in publications as a term for an open-circuit, demand valve-controlled breathing apparatus (even after Air Liquide's patent expired and other manufacturers started making identical equipment), occasionally also for rebreathers, and in figurative uses (such as "the water spider's aqualung of air bubbles").
The acronym "SCUBA", or "Self Contained Underwater Breathing Apparatus", originated in the United States Navy, where it referred to a frogman's oxygen rebreather designed by Christian J. Lambertsen.
[citation needed] In Britain, Siebe Gorman (who held the rights to the tradename "Aqualung") made no serious attempt to control use of the word, and "aqualung" remained a common public generic word for that sort of apparatus – including in the British Sub-Aqua Club's official publications – for many years.
