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![[image of flower]](../../ima/flowXS_06.gif)
General Purpose Tools, Machines & Machine Tools |
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Chronology
Simple tools and machines (complex tools) are important, components in an industrial society because they make and drive special-purpose machines with reduced amounts of animal and worker effort. Welding, brazing, soldering and cutting equipment enable complex machines to be fabricated without fasteners. Gears and cams translate motion at different rates into different directions. Pumps and compressors create useful vacuums that drive machinery and equipment. Winches and cranes move loads from one place to another in place of animal and people labor. Hammers, screwdrivers, wrenches, saws, axes, drills and other hand tools are slightly more complex renditions of the 6 basic machines on which all other mechanical machines are derived. These are all-purpose tools. In addition, there are thousands of special-purpose tools used to reduce manual effort and time. Without these simple tools, it would be almost impossible to construct bigger and better machines. A cam is a device that converts rotary motion to linear motion. It is shaped like a disc, but with a variable radius. A cam follower, such as a rod or a wheel attached to a rod causes the rod to move up and down. An example of this device is an automobile camshaft used to move engine intake and exhaust valves. A gear is a toothed wheel and two or more gears on shafts are used to transmit power from one shaft to another, in the same direction or in different directions. Gears are also used to increase or reduce the speed of the shafts, such as in an automobile transmission system. There are different kinds of gears: spur, bevel, helical and worm. Spur gears, the most common, transmit power to parallel shafts or to gears on the same shaft. When one or more "planet" gears run along the outside of a "sun" gear, the combination is called a planetary or epicyclic system. Multiple speed bicycles use this system. Bevel gears are shaped like cones to allow transmitting power between shafts that have intersecting axes. Spur and bevel gears that have spiral teeth to transmit power between shafts at any angle between them. Worm gears have one spur or helical gear and one worm gear at a 90°angle to each other. The worm gear has one or more threads. Gears are usually made of steel, but plastic and composite non-metals are used for gears too. Gears and cams are made by special cutting machines. Machines tools are machines used to make and repair parts. Special purpose machine tools make a single parts, while general purpose machine tools make a variety of parts and, in combination, can reproduce themselves. Special purpose machine tools cannot reproduce themselves. Typical general purpose machine tools are drilling machines, sawing and cutoff machines, lathes, planing, milling and grinding machines. The use of faster and more accurate and precise machine tools resulted in interchangeable parts, assembly lines, automation, and cheaper products. Welding, Brazing and Soldering Welding, brazing and soldering are 3 methods to join metals using gas or electric torches for heat. Welding fuses the metals by melting both. A filler metal with a coating to prevent atmospheric effects may or may not be used. It is commonly applied to iron and steel, but also to plastics. The simplest type of welding is by hammering together 2 heated pieces of metal. This was performed by blacksmiths in early times. In oxy-acetylene welding, the heat is produced by the combustion of oxygen and acetylene. Arc welding is welding using a heat-generating electric arc between a carbon (no filler) or metallic (filler) electrode and the metal. An inert gas, such as argon may be used to prevent unwanted oxidation from the air. Brazing and soldering use a filler metal that melts and binds to the two working metals, neither of which are melted. The basic difference between the two methods is that brazing uses a higher temperature melting metal than soldering. The filler material, often an alloy of copper and zinc for brazing and tin and lead for soldering, must melt at a lower temperature than either metal so they will not melt too. A flux is used to clean the metal surfaces of oxides and impurities. Brazing produces a stronger joint than soldering, while welding produces the strongest bond of all. How 331,2458,3131 In assembly-line industrial fabrication, where frequent welds are required, welding often is done with robots. Water, petroleum and other liquids often must be pumped to their destinations to overcome gravitational and frictional forces. The heart is a natural blood pump. Compressed air and other gases have potential energy to drive machinery and burn fuels. An air pump or compressor (one compresses the air in one container and then pumps it into another) is a machine that compresses air to drive other machinery. An example of the simplest compressor is a bicycle tire pump. Muscle power pushes and pulls against a handle that moves a leather cup piston up and down inside a cylinder, the barrel of the pump. As the handle moves up, air is drawn past the piston to fill the cylinder with air. As the handle moves down, the leather cup is spread against the cylinder wall and the air is compressed until the pressure opens a nonreturn valve to push the air into the tire. A more complex pump is the compressor used in industries, which is powered by a motor. These compressors drive pneumatic drills and machinery, paint sprayers, passenger elevators, tunneling machines, assembly line tools, liquid pumps, etc. Animal lungs are natural air pumps. A bellows, used to drive air into furnaces and forges, is a pump (and compressor). How 587 Bellows, an air pump and driven by human and animal power or water power, were used extensively since ancient times by blacksmiths and in steelmaking furnaces and forges. They are made from leather. The bellows is opened to allow air in and closed to force air out. Gears and cams are ancient devices that were made of wood until technical advances in steel made them more accurate and cheaper. Steel gears and cams last much longer than wood gears. Around 2,000,000 BCE, the first advances in technology made by unknown pre-homo sapiens ancients were the development of simple stone tools, especially knives and spears used to kill, skin, and cut meat. Tools saved labor, i.e., they increased productivity, which let people devote more time to produce other inventions, art, and play. Another very useful tool for hunting was the invention of the bow and arrow around 20,000 BCE. In 1645, a German physicist, Otto von Guericke, invented the first practical air pump. It worked like a water pump, except that the parts were fitted together well enough to make it almost airtight. It was pumped by hand. Asimov 165 The principles of air pumps would lead in later centuries to pneumatic drills to remove ores more efficiently. In 1646, Joseph Jencks was granted a Massachusetts patent for a scythe-grinding machine. Carruth 17 Unless iron was absolutely required, most tools and machinery in 1790 were made of wood, which was readily available everywhere in America and much cheaper than iron. In 1798, David Wilkinson of Rhode Island invented a screw threading machine. At this time, all welding is done by hammering together two heated pieces of metal, work usually performed by blacksmiths. Abel Stowel of Massachusetts produced a screw-cutting machine in 1809. In 1845, the German inventor, Johann Geissler, used a column of mercury moving up and down to create a vacuum above the mercury that sucked air out of a container. This method created vacuums that were more perfect than the Guericke pump. His Geissler tubes, as they were called, were used by scientists to determine atomic structure and by lamp inventors, like Thomas Edison, to create the incandescent lamp. Asimov 370 Auguste De Meritens, a Frenchman, used the heat of an electric arc to join lead plates for storage batteries in the year 1881. His pupil, a Russian, Nikolai N. Benardos, was granted a patent for welding. He and a fellow Russian, Stanislaus Olszewski, secured a British patent in 1885 and an American patent in 1887. This was the beginning of carbon arc welding. A blow pipe or torch that used hydrogen or coal gas and oxygen was invented in 1887. Weld n.p. In 1890, C.L. Coffin of Detroit was awarded the first U.S. patent for an arc welding process using a metal electrode. Weld n.p. About 1900, Strohmenger, an Englishman, introduced a coated metal electrode that stabilized the arc. The coating was clay or lime. Around this sam time, a torch using low-pressure acetylene was invented. Weld n.p. Oscar Kjellberg of Sweden invented a covered or coated electrode stick sometime between 1907 and 1914. The stick electrodes were made by dipping short lengths of bare iron wire into mixtures of carbonates and silicates, and then the coating was allowed to dry. Weld n.p. In 1920, automatic arc welding using a bare electrode wire was invented by P.O. Nobel of the General Electric Company. Weld n.p. H.M. Hobart and P.K. Devers used argon and helium atmospheres in 1926. Weld n.p. Submerged arc welding process; that is, welding "under powder" or smothered arc welding process was invented by the National Tube Company for a pipe mill at McKeesport, PA. It was designed to weld longitudinal seams in the pipe. The process was patented by Robinoff in 1930 and was later sold to Linde Air Products Company, where it was renamed Unionmelt® welding. Submerged arc welding was used during the defense buildup beginning in 1938 in shipyards and in ordnance factories. It is one of the most productive welding processes and is used today. Weld n.p. |
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