Diving bell
The diving bell is a container that is filled with air and due to its weight - despite the air inside - does not float in the water, but rather sinks. It makes it possible to stay under water for a long time and to carry out work.
Construction principle
Basically, diving bells can be differentiated according to whether they are open or closed and whether they have an air supply or not.
Open diving bells without air supply
A wooden or metal box , open at the bottom, hangs on an iron chain or a steel cable. When the box is lowered into the water, the air bubble inside is compressed by the water pressure until the water pressure and the air pressure in the bubble are the same. It is the oldest construction method already described by Aristotle . It served, for example, pearl divers as a base in the depths, which made it unnecessary for the divers to lose time by first having to get down from the surface and then up again with one breath. The bottom time was correspondingly short. In a diving bell, the divers were lowered, took a breath, got out, did their work and came back into the bell. They could repeat this several times. The dives could last up to a quarter of an hour instead of about two minutes.
Open diving bells with air supply
The diving bell without air supply had the disadvantage that the diving time was longer than with free divers , but was still limited by the fact that firstly, the air reserve was enriched with the carbon dioxide from the exhaled air and secondly, the air bubble was already compressed and thus reduced when it was lowered became ( Boyle-Mariotte law ). This changed when Edmund Halley ( Halley's Comet is named after him) on October 7, 1691 presented an air-powered diving bell. Barrels with fresh air were lowered next to the bell. As soon as these were lower than the bell, you could let in the fresh air. This made it possible to renew the air we breathe and also to gradually enlarge the air bubble. Halley himself stayed at a depth of 15 meters for 1.5 hours with this device.
A diver who was connected to the diving bell by a breathing tube could now inhale the pre-compressed air better.
From 1775, the bells supplied in this way were equipped with drain cocks. In this way, the used air could be partially let out before the fresh air was supplied from the barrels.
With the development of powerful and at the same time sufficiently mobile compressors , it became possible to continuously pump down the air and to keep the inside of the diving bell permanently dry. The first bell of this type was built in 1778 by the British hydraulic engineer John Smeaton .
The caisson
A further development of the open diving bell is the caisson (French: caisson = box), which is used for larger work on the bottom of water. This device is essential, especially when working in the harbor basin , in tunnel and bridge construction . The first caisson was built and used in 1850. In German waters he has since the late 19th century as divers bay and later - with their own accord - as diving bells ship in operation. (see Kaiman and Carl Straat )
Here, too, the air is constantly pushed into the box by means of compressors via air hoses. The air pressure in the box is slightly higher than the surrounding water pressure. Entry is via a pressure lock . The lower edge of the caisson rests directly on the ground or is pressed into soft ground. This makes it possible to work almost dry.
The closed diving bell
The closed diving bell represents the preliminary end point of the development. It is primarily used as a means of divers' transport during saturation diving , in which the divers are brought to the ambient pressure in the working depth on the surface and live under this pressure for a long time. They must be brought in depth while maintaining the pressure. The closed diving bell is used for this. It is sealed pressure-tight and docks to the pressure chamber in which the divers stay on the surface. They get in, the bell is locked and lowered into the water. At depth, the divers open them from the inside and can get out. The supply takes place via the usual supply lines, an emergency gas supply on the bell serves to bridge any failures. During deep dives, the diver is provided with care from the bell, a second diver is used for safety and control. The limits of the construction are expanded through integration in work submarine constructions (e.g. Felinto Perry , PC-18), through use as an observation capsule and equipment with remote-controlled grippers or propellers for lateral movements.
Diving bells today
The open diving bell was suitable for diving in shallow water. Modern, closed diving bells are more powerful and flexible here. They are used as:
- Caisson / caisson / dry working chamber
- stationary, open decompression aid / decostation and communication aid ("telephone booth") at different depths (usually without air supply, the divers continue to breathe from their diving equipment)
- Decompression and diver transport for saturation dives, as part of the pressure chamber system.
- Underwater stations with ambient pressure (living, working or vacationing underwater)
- as part of a diving transport submarine
- Diving bell ship (e.g. TGS Carl Straat of the Duisburg-Rhine Water and Shipping Office)
- Kaiman diving shaft built in 1892, in use at the Bingen Waterways and Shipping Authority until 2006
- Diving shaft II in the Magdeburg Science Harbor
Timetable
- around 320 BC Chr .: Aristotle describes the principle of the diving bell. In the following time it is forgotten again.
- 1538: An open diving bell without air supply is demonstrated in Toledo .
- 1583/84: The Italian Giuseppe Bono demonstrates a diving bell in Lisbon in the presence of Philip II , "without getting wet", which he wants to use "for pearl diving".
- around 1665: The British captain William Phipps "reinvents" the open diving bell without an air supply, with the help of which he succeeds in recovering large amounts of gold and silver from the mouth of the Río de la Plata .
- 1691: Denis Papin experiments with the air supply of a diving bell by means of bellows . Edmund Halley patented a diving bell with air supply from barrels.
- 1778: John Smeaton builds the first hose-supplied diving bell.
- 1850: The French Cavé uses the first caisson for construction work in the Nile.
- 1892: Hanner u. Comp., Duisburg builds the diving bell ship Kaiman for work on the Rhine.
literature
- Emo Descovich: Technique of depth , 5th edition, Franckh, Stuttgart 1932; NA: Salzwasser, Paderborn 2012, ISBN 978-3-8460-0389-3 .
- Hanns Günther: The conquest of the deep , Kosmos Stuttgart 1928, DNB 574763325 .
Web links
- The diving bell - in Pfennig magazine No. 1 from May 4, 1833
- Historical Diving Society: The History of the Diving Bell ( Memento April 14, 2009 in the Internet Archive )
- Alexander the Great and the Bathysphere
Individual evidence
- ^ Ernst Schäfer: The Royal Spanish Council of India . Part I. History and organization of the Council of India and the Casa de la Contratacion in the sixteenth century. Hamburg: Ibero-American Institute 1936. p. 205 Note 17 - Pearl fishing came on Portuguese territory before a. in Sri Lanka in the Gulf of Mannar .
- ↑ Zeitschrift für Bauwesen , 1896, p. 99