Diving Bell

Invented by : Guglielmo de Lorena

Invented in year : 1535

A diving bell is one of the earliest types of equipment for underwater work and explorations. It consisted of a cable-suspended airtight chamber, open at the bottom like a moon pool structure, that is lowered underwater to operate as a base or a means of transport for a small number of divers. The pressure of the water keeps the air trapped inside the bell. They were the first type of diving chamber. Early bells consisted of a container open only at the bottom, usually provided with a source of compressed air. Diving bells are used as underwater rescue vessels and by working divers doing underwater work and salvage. The bell is lowered into the water by cables from a crane attached to a ship or dock. The bell is ballasted so as to remain upright in the water and to be negatively buoyant so that it sinks even when completely full of air. They are also known as a wet bell,

Hoses, fed by pumps on the surface, provide compressed breathing gas to the bell, serving two functions:

1. Fresh gas is available for breathing by the occupants, and excess gas leaks out under the lip of the wet bell, where it bubbles naturally to the surface.
2. As a wet bell is lowered, increasing pressure from the water compresses the gas in the bell. If the gas pressure inside the bell were not raised by adding gas to compensate for the outside water pressure, the bell would partially fill with water as the gas was compressed. Adding pressurized gas ensures that the usable workspace within the bell remains constant as the bell descends in the water, as well as refreshing the air, which would become saturated with a toxic level of carbon dioxide and depleted of oxygen by the respiration of the occupants.

History

The use of the diving bell was first described by Aristotle in the 4th century BC: "...they enable the divers to respire equally well by letting down a cauldron, for this does not fill with water, but retains the air, for it is forced straight down into the water." One of the earliest reports of the use of a device that enabled a diver to enter the water with some degree of protection and a supply of air involved the diving bell, Colimpha used in Alexander the Great's descent in approximately 330 B.C., depicted by an Indian artist in a 1575 miniature. An account of this dive appeared in the 13th century French manuscript, The True History of Alexander.

In 1535, Italian, Guglielmo de Lorena created and used what is considered to be the first modern diving bell. It was worn on the shoulders of the diver and was supported by slings. He hoped to salvage some boats belonging to an ancient roman emperor. Though he did not succeed, he was one of the first to use a diving bell to complete a one-hour dive and showed that his bell did work.

Development in the invention of the diving bell

In 1616, Franz Kessler built an improved diving bell.

In 1687, Sir William Phipps used an inverted container to recover £200,000-worth of treasure from a Spanish ship sunk off the coast of San Domingo.

In 1689, Denis Papin suggested that the pressure and fresh air inside a diving bell could be maintained by a force pump or bellows.

The earliest applications were probably for commercial sponge fishing. A diving bell was used to salvage more than 50 cannons from the Swedish warship Vasa in the period immediately following its sinking in 1628.

In 1690, Edmund Halley completed plans for a diving bell capable of remaining submerged for extended periods of time, and fitted with a window for the purpose of undersea exploration. In Halley's diving bell, atmosphere is replenished by sending weighted barrels of air down from the surface.

In 1789, John Smeaton, an english engineer utilized Denis Papin's design to fit an air pump to the bell. Regardless of the depth to which a diving bell is lowered, in principle at least, fresh air fills the available vital space. It's pressure is automatically regulated by the pump and by the water pressure; surplus air escapes through the edges of the container. As the bell descends, the water level tends to rise inside the bell. As it surfaces, the decreasing water pressure lowers the level inside the bell. Thus, the pressure inside the bell remains the same as that outside. Some bells, however, are kept at working-depth pressure and are used to commute to and from an outfitted surface decompression chamber and the work site, thus eliminating the need for decompression between dives on a mission.

Role of the diving bell in the improvement of human life

• It encouraged further improvements and inventions in underwater equipment.

• Man was able to explore and utilise the resources of the hidden underwater world.

• It led to a better understanding of underwater environment.