The Development History Of Gears

Origin
In 300 BC, the ancient Greek philosopher Aristotle, in The Mechanical Problem, addressed the problem of the transmission of rotating motion by bronze or cast iron gears. The famous Greek scholars Aristotle and Archimedes have studied the gear, the famous Greek inventor Gutisibius in the round plate table edge evenly inserted the dowel, so that it mesh with the pin wheel, he applied this mechanism to the engraved. This was about 150 BC. In 100 BC, the Alexandrian inventor Heron invented the odometer, in which gears were used. In the 1st century AD, the Roman architect Bidopius also used a gear drive in his water-wheel mill. By the 14th century, gears were used on clocks.
In the early Eastern Han Dynasty (1st century AD), there were already double-shaped gears. The south-pointing car and the drum car in The Three Kingdoms period have adopted the gear transmission system. The water rotary continuous mill invented by Du Yu in the Jin Dynasty is to transfer the power of the water wheel to the stone mill through the gear. The earliest record of gear transmission system in historical books is the description of the water-moving armsphere made by Liang Lingzan in 725 of the Tang Dynasty. The water transport instrument platform (see ancient Chinese chronometer) manufactured in the Northern Song Dynasty used a complex gear system. In 1956, the ancient city of Anwuji in Hebei Province was excavated, and an iron spine gear with a diameter of about 80 mm was found. Although the wheel was broken, it was of good iron quality. After research, it was confirmed that it was made during the late Warring States period (3rd century BC) to the Western Han Dynasty (206 BC ~ 24 AD). In 1954, bronze spiny gears were unearthed in Tilangjiaya, Yongji County, Shanxi Province. With reference to the artifacts unearthed in the same pit, it can be concluded that it is a relic of the Qin Dynasty (221 ~ 206 BC) or the early Western Han Dynasty, with 40 teeth and a diameter of about 25 mm. As for the purpose of the spine gear, no written records have been found so far, and it is speculated that it may be used for braking to prevent the axle from reversing. In 1953, a pair of bronze herringbone gears were unearthed in Hongqing village, Chang 'an County, Shaanxi Province. According to the analysis of tomb structure and burial articles, it can be concluded that this pair of gears originated from the early Eastern Han Dynasty. Both wheels have 24 teeth and are about 15 mm in diameter. The same herringbone gear was also found in Hengyang and other places. [1]
As early as 1694, French scholar PHILIPPE DE LA HIRE first proposed that the involute can be used as a tooth curve. In 1733, the Frenchman M. AMUS proposed that the common normal of the tooth contact point must pass through the node on the central connection. When an auxiliary spur line rolls along the spur line (pitch circle) of the big wheel and the small wheel respectively, the two tooth profiles formed by the envelope of the auxiliary spur line and the auxiliary spur line are conjugate to each other, which is CAMUS theorem. It takes into account the meshing state of two tooth surfaces; The modern concept of contact point trajectories is clearly established. In 1765, L. ULER of Switzerland proposed the mathematical basis for the analysis of involute tooth profile, and clarified the relationship between the radius of curvature and the position of the center of curvature of the tooth profile curve of a pair of meshing gears. Later, SAVARY further completed this method and became the EU-LET-SAVARY equation. The contribution to the application of involute tooth profile is ROTEFT WULLS, who proposed that when the center distance changes, the involute gear has the advantage of constant angular ratio. In 1873, the German engineer HOPPE proposed that the gear shape of the asymptote when the pressure Angle of the gear with different number of teeth was changed, thus laying the foundation of the idea of modern gear with variable position.
At the end of the 19th century, the principle of developing the cutting method and the special machine tools and tools using this principle appeared one after another, so that the gear processing has a more complete means, the involute tooth shape has shown great advantages. As long as the cutting tool is slightly moved from the normal meshing position, the standard tool can be used to cut out the corresponding displacement gear on the machine tool. In 1908, the Swiss MAAG studied the displacement method and manufactured the development of the machining gear shaper machine, and later, the British BSS, the American AGMA, and the German DIN successively proposed a variety of calculation methods for the gear displacement.