Diving bell

The diving bell is a container that is filled with air and by its weight - in spite of the air inside - does not float in water but sinks. It allows you to stay a longer time under water and perform work.

Design principle

Basically, you can diving bells then distinguish whether they are open or closed, and whether they have an air supply or not.

Open diving bells without air supply

A downwardly open wooden or metal box attached to an iron chain or steel cable. When lowering the box in the water, the air bubble is so far compressed inside by the water pressure until the water pressure and the air pressure in the bladder are the same. This is the oldest construction, which was described by Aristotle. It served as a base for example pearl divers at depth, which made it unnecessary that the diver thus lost time that they first had from the surface with a gasp down and get back up. The bottom time was correspondingly low. In a diving bell, the divers were lowered, got breath, got out, did their work and came back to the bell. This could be repeated several times. The dives were able to take place about 2 minutes up to a quarter of an hour.

Open belles of air supply

The diving bell without air supply had the disadvantage that the dipping time was indeed longer than free divers, but still limited by the fact that, first, the air reserve time enriched with the carbon dioxide in the exhaled air and secondly the air bubble is also already compressed during lowering and reduced so was ( Boyle - Mariotte's law ). This changed when Edmund Halley ( namesake of the eponymous comet ) on October 7, 1691 presented a diving bell with air supply. In addition to the bell barrels were lowered with fresh air. Once these were lower than the bell, you could direct the fresh air inside. This made ​​it possible to replace the inhaled air and the bubble to enlarge gradually. Halley himself remained with this device 1.5 hours at 15 meters depth.

From 1775 we equipped the so -served bells with drain taps. So you could see the stale air partially drain before was fed into the fresh air from the barrels.

With the development of powerful and at the same time sufficiently mobile compressors, it became possible herabzupumpen the air continuously and to keep the inside of the diving bell constantly dry. The first bell of this type was built in 1778 by the British engineer John Smeaton water.

The caisson

A further development of the open diving bell is the caisson (French Caisson = box), which is used in larger works on the base of the aquatic environment. Especially when working in the docks, in the tunnel and bridge this device is indispensable. The first caisson was constructed and used in 1850. In German waters he is a diver shaft and later since the end of the 19th century - with its own drive - as diving bells ship in operation.

Again, the air is constantly pushed by compressors on air hoses in the box. The air pressure in the box is a little higher than the surrounding water pressure. Entry is via a pressure lock. The lower edge of the caisson rests directly on the ground or expresses itself in soft ground. This makes it possible to work almost dry.

The closed diving bell

The preliminary end point of the development is the closed diving bell; they serve primarily as a diver transport agent in saturation diving where the divers are already brought to the surface to the ambient pressure in the working depth and prolonged life under this pressure. They must be brought into the depth while maintaining the pressure. For this purpose, the closed diving bell is used. It is sealed in a pressure -tight and docked to the pressure chamber in which the diver to stay on the surface, at. This is a rise, the bell is sealed and lowered into the water. At depth, the diver open it from the inside and can get out. The supply takes place via the usual supply lines, an emergency gas supply at the bell serves to bridge any failures. For deep dives, the diver supply is ensured by the bell, a second diver is for safety or control. The limits of design (eg, Perry, PC -18), extended through integration into working submarine constructions by 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 here are powerful and flexible. They are used as:

• Caisson / caisson / dry working chamber
• Stationary, open Dekompressionshilfe / deco station and communication aid ( " Phone Booth " ) at different depths (usually without air supply, the divers breathe from their diving equipment on)
• Decompression divers and transport means for saturation dives, as part of the pressure chamber system.
• Underwater stations with ambient pressure ( live, work or vacation under water)
• As part of a diver transport submarine
• Diving bells ship (eg TGS Carl Straat the Waterways and Shipping Office Duisburg- Rhine )
• Divers Shaft " Cayman " Year 1892 to 2006 Waterways and Shipping Office Bingen in use
• Diver shaft in Magdeburg Science Port

Chronology

• Around 320 BC, Aristotle describes the principle of the diving bell. In the following years it gets back into oblivion.
• 1538: In Toledo, an open diving bell is presented without an air supply.
• 1665: The British captain William Phipps " invents again " the open diving bell without air supply, with which he manages to recover before the mouth of the Río de la Plata large quantities of gold and silver.
• 1691 Denis Papin experimented with the air supply by means of a diving bell bellows. Edmund Halley patented in a diving bell with air supply through barrels.
• 1778: John Smeaton built the first tube- supplied diving bell.
• 1850: The Frenchman Cavé uses the first caisson for construction work in the Nile.
• 1892: . Messrs. Hanner and Co., Duisburg builds the diving bell ship Cayman for work assignments on the Rhine. Source: 'Journal of Construction ' 1896, p 99