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A Drifter is either a hydraulic or pneumatic powered rock or ground drill placed on top of a feed. The feed is like a rail that the drill travels on, or drifts. This kind of drilling procedure is also called drifting. The feed is usually attached with a flexible boom (like an arm) to a stationary or mobile unit that contains the powerpack (engine and hydraulic pump or compressor). Drifters are used in mining, construction, exploration and natural science. A hydraulic rock drill or drifter is usually a machine that consists of a percussive system and a rotative system. The percussive system strikes the drill steel, for example 2000-5000 strikes per minute, as the rotation can be, for example, 100-400 rounds per minute. Combined together, these functions enable drilling holes into rock. The excess material (cuttings) is then pushed up from the bottom of the hole by means of pressurized air or water. Hydraulic rock drills are also called hydraulic top hammers, which explains the position of the actual drilling device concerning the drill rod. Opposite to a top hammer drill or drifter are the down-the-hole hammers, which are usually pneumatic. ==Early rock drills== In 1849, J. J. Couch, an American inventor from Philadelphia, received the first patent for a rock drill.〔(【引用サイトリンク】title=From gunpowder to Pit Viper )〕 It featured a drill rod which passed through a hollow piston and was thrown against the rock. In 1851, James Fowle received a patent for a rock drill powered by steam or compressed air.〔(【引用サイトリンク】title=Drills )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Drifter (drill)」の詳細全文を読む スポンサード リンク
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