Charles Brady King

Sri Lanka,ශ්‍රී ලංකා,Ceylon,Jackhammer,Marteau Piqueur,Presslufthammer

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• published: 15 Oct 2011
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A pneumatic jackhammer, also known as a pneumatic drill or pneumatic hammer, is a jackhammer that uses compressed air as the power source. The air supply usually comes from a portable air compressor driven by a diesel engine. Reciprocating compressors were formerly used. The unit comprised a reciprocating compressor driven, through a centrifugal clutch, by a diesel engine. The engine's governor provided only two speeds: idling, when the clutch was disengagedmaximum, when the clutch was engaged and the compressor was running.Modern versions use rotary compressors and have more sophisticated variable governors. The unit is usually mounted on a trailer and sometimes includes an electrical generator to supply lights or electric power tools.Additionally, some users of pneumatic jackhammers may use a pneumatic lubricator which is placed in series with the air hose powering the air hammer. This increases the life andperformance of the jackhammer. Specific lubricant in filled in the pneumatic lubricator. Furthermore, air compressors typically incorporate moisture into the compressed air leading to freeze-ups of the jackhammer or air hammer in cold weather.A jackhammer is a pneumatic tool that combines a hammer directly with a chisel that was invented by Charles Brady King. Hand-held jackhammers are typically powered by compressed air, but some use electric motors. Larger jackhammers, such as rig mounted hammers used on construction machinery, are usually hydraulically powered. They are usually used to break up rock, pavement, and concrete. In modern terminology, a "jackhammer" does not have the capacity to drill rock.A jackhammer operates by driving an internal hammer up and down. The hammer is first driven down to strike the back of the bit and then back up to return the hammer to the original position to repeat the cycle. The bit usually recovers from the stroke by means of a spring. The effectiveness of the jackhammer is dependent on how much force is applied to the tool.Pneumatic drills were developed in response to the needs of mining, quarrying, excavating, and tunneling. The first "percussion drill" was made in 1848 and patented in 1849 by Jonathan J. Couch of Philadelphia, Pennsylvania.In this drill, the drill bit passed through the piston of a steam engine. The piston snagged the drill bit and hurled it against the rock face. It was an experimental model. In 1849, Couch's assistant, Joseph W. Fowle, filed a caveat for a percussion drill of his own design. In Fowle's drill, the drill bit was connected directly to the piston in the steam cylinder; specifically, the drill bit was connected to the piston's crosshead. The drill also had a mechanism for turning the drill bit around its axis between strokes and for advancing the drill as the hole deepened.By 1850 or 1851, Fowle was using compressed air to drive his drill, making it the first true pneumatic drill.The demand for pneumatic drills was driven especially by miners and tunnelers because steam engines required fires in order to operate and the ventilation in mines and tunnels was inadequate to vent the fires' fumes; there was also no way to convey steam over long distances (e.g., from the surface to the bottom of a mine); furthermore, mines and tunnels occasionally contained flammable explosive gases such as methane. By contrast, compressed air could be conveyed over long distances without loss of its energy, and after the compressed air had been used to power equipment, it could still serve to ventilate a mine or tunnel.In Europe since the late 1840s, the king of Sardinia, Carlo Alberto, had been contemplating the excavation of a 12-kilometer (7.5 mi) tunnel through Mount Fréjus in order to create a rail link between Italy and France, which would cross his realm.The need for a mechanical rock drill was obvious and this sparked research on pneumatic rock drills in Europe. A Frenchman, Cavé, designed, and in 1851 patented, a rock drill that used compressed air; however, the air had to be admitted manually to the cylinder during each stroke, so it was not successful.[7] In 1854, in England, Thomas Bartlett made and then patented (1855) a rock drill in which the drill bit was connected directly to the piston of a steam engine. In 1855 Bartlett demonstrated his drill, powered by compressed air, to officials of the Mt. Fréjus tunnel project.(In 1855, a German, Schumann, invented a similar pneumatic rock drill in Freiburg, Germany. Bartlett's drill was refined by the Savoy-born engineer Germain Sommeiller (1815-1871) and his colleagues, Grandis and Grattoni, by 1861.Thereafter, many inventors refined the pneumatic drill.The word "jackhammer" is used in North American English and Australia, while "pneumatic drill" is used colloquially elsewhere in the English speaking world, although strictly speaking a "pneumatic drill" refers to a pneumatically driven jackhammer.In Britain, the term "jackhammer" usually refers to electromechanical version of the tool.