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A crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated. Crushing is the process of transferring a force amplified by mechanical advantage through a material made of molecules that bond together more strongly, and resist deformation more, than those in the material being crushed do. Crushing devices hold material between two parallel or tangent solid surfaces, and apply sufficient force to bring the surfaces together to generate enough energy within the material being crushed so that its molecules separate from (fracturing), or change alignment in relation to (deformation), each other. The earliest crushers were hand-held stones, where the weight of the stone provided a boost to muscle power, used against a stone anvil. Querns and mortars are types of these crushing devices. ==Background history== In industry, crushers are machines which use a metal surface to break or compress materials into small fractional chunks or denser masses. Throughout most of industrial history, the greater part of crushing and mining part of the process occurred under muscle power as the application of force concentrated in the tip of the miners pick or sledge hammer driven drill bit. Before explosives came into widespread use in bulk mining in the mid-nineteenth century, most initial ore crushing and sizing was by hand and hammers at the mine or by water powered trip hammers in the small charcoal fired smithies and iron works typical of the Renaissance through the early-to-middle industrial revolution. It was only after explosives, and later early powerful steam shovels produced large chunks of materials, chunks originally reduced by hammering in the mine before being loaded into sacks for a trip to the surface, chunks that were eventually also to lead to rails and mine railways transporting bulk aggregations that post-mine face crushing became widely necessary. The earliest of these were in the foundries, but as coal took hold the larger operations became the coal breakers that fueled industrial growth from the first decade of the 1600s to the replacement of breakers in the 1970s through the fuel needs of the present day. The gradual coming of that era and displacement of the cottage industry based economies was itself accelerated first by the utility of wrought and cast iron as a desired materials giving impetus to larger operations, then in the late-sixteenth century by the increasing scarcity of wood lands for charcoal production to make the newfangled window glass〔〕 material that had become—along with the chimney—'' 'all the rage' '' among the growing middle-class and affluence of the sixteenth-and-seventeenth centuries;and as always, the charcoal needed to smelt metals, especially to produce ever larger amounts of brass and bronze,〔Burke, James, ''"Connections"'', page 167〕 pig iron, cast iron and wrought iron demanded by the new consumer classes. Other metallurgical developments such as silver and gold mining mirrored the practices and developments of the bulk material handling methods and technologies feeding the burgeoning appetite for more and more iron and glass, both of which were rare in personal possessions until the 1700s. Things only became worse when the English figured out how to cast the more economical iron cannons (1547), following on their feat of becoming the armorers of the European continent's powers by having been leading producers brass and bronze guns,〔 and eventually by various acts of Parliament, gradually banned or restricted the further cutting of trees for charcoal in larger and larger regions in the United Kingdom.〔 In 1611, a consortium led by courtier Edward Zouch was granted a patent for the reverberatory furnace, a furnace using coal, not precious national timber reserves,〔Burke, James, ''"Connections"'', page 168〕 which was immediately employed in glass making. An early politically connected and wealthy Robber Baron figure Sir Robert Mansell bought his way into the fledgling furnace company wrested control of it, and by 1615 managed to have James I issued a proclamation forbidding the use of wood to produce glass,〔 giving his families extensive coal holdings a monopoly on both source and means of production for nearly half-a-century. Abraham Darby a century later relocated to Bristol where he had established a building brass and bronze industry by importing Dutch workers and using them to raid Dutch techniques. Both materials were considered superior to iron for cannon, and machines as they were better understood. But Darby would change the world in several key ways. Where the Dutch had failed in casting iron, one of Darby's apprentices, John Thomas succeeded in 1707〔Burke, James, ''"Connections"'', page 170〕 and as Burke put it: ''"had given England the key to the Industrial Revolution"〔''. At the time, mines and foundries were virtually all small enterprises except for the tin mines (driven by the price and utility of brass) and materials came out of the mines already hammered small by legions of miners who had to stuff their work into carry sacks for pack animal slinging. Concurrently, mines needed drained resulting in Savery and Newcomen's early steam driven pumping systems. The deeper the mines went, the larger the demand became for better pumps, the greater the demand for iron, the greater the need for coal, the greater the demand for each. Seeing ahead clearly, Darby, sold off his brass business interests and relocated to Coalbrookdale with its plentiful coal mines, water power and nearby ore supplies. Over that decade his foundries developed iron casting technologies and began to supplant other metals in many applications. He adapted Coking of his fuel by copying Brewers practices.〔 In 1822 the pumping industries needs for larger cylinders met up with Darby's ability to melt sufficient quantities of pig iron to cast large inexpensive iron cylinders instead of costly brass ones,〔 reducing the cost of cylinders by nine-tenths.〔〕 With gunpowder being increasingly applied to mining, rock chunks from a mining face became much larger, and the blast dependent mining itself had become dependent upon an organized group, not just an individual swinging a pick. Economies of scale gradually infused industrial enterprises, while transport became a key bottleneck as the volume of moved materials continued to increase following demand. This spurred numerous canal projects, inspired laying first wooden, then iron protected rails using draft animals to pull loads in the emerging bulk goods transportation dependent economy. In the coal industry, which grew up hand in hand as the preferred fuel for smelting ores, crushing and preparation (cleaning) was performed for over a hundred years in coal breakers, massive noisy buildings full of conveyors, belt-powered trip-hammer crushing stages and giant metal grading/sorting grates. Like mine pumps, the internal conveyors and trip-hammers contained within these 7—11 story buildings. 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「crusher」の詳細全文を読む スポンサード リンク
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