مقاله مکانیک -یاتاقان فشاری کینگزبری
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The first Kingsbury thrust bearing was put into service on June 22, 1912, under the 10,000kilowatt Unit 5 at the Holtwood hydroelectric station of the Pennsylvania
Water & power Company. The 48inch (1,219mm ) diameter bearing has been at work ever since, effortlessly carrying 410,000 pounds (186,000 kg) at a speed
of 94 rpm.
All rotating machinery must use bearings to maintain the correct location between stationary and revolving parts, and to maintain the correct relative position of the
shaft and its supporting structure. Specifically, a thrust bearing maintains the relative axial location of a shaft and its supporting structure. Helicopter rotors, for
example, and boat and airplane propellers need thrust bearings on their shafts. So do water and steam turbines, which must operate continuously for long periods of
time—usually several years—with no maintenance.
The Kingsbury thrust bearing was the brainchild of Pittsburgh mechanical engineer Albert Kingsbury (1863–1943). Kingsbury's idea was deceptively simple: instead
of roller bearings, a series of adjustable bearing surfaces would carry the weight, gliding, as they did so, over a continuous film of oil.
Patented in 1910 (No. 947,242), the Kingsbury thrust bearing consists of a stationary castiron ring (called a "runner"), a cupshaped frame or collar (to
Albert Kingsbury (right) and Frederick A. Allner, who later became
a vice president of the Pennsylvania Water and Power
Company, inspect the Unit 5 thrust bearing in 1937.
contain the lubricant), the shaft, and a segmental ringbearing member comprised of several wedgeshaped bearing shoes (usually six, as in the case of Holtwood Unit
5) that are identical in size. Each shoe is loosely bolted through a tapped hole at its midpoint so that it can rock a bit. As the shaft rotates, a film of oil is forced
between the stationary ring and the shoes, where the pressure is highest. The oil actually supports the weight—there is no physical contact between the runner and the
shoes—resulting in extremely low friction and almost no mechanical wear.
Until the advent of the Kingsbury thrust bearing, units like
Holtwood represented the upper limit of hydroelectric turbine size; even then, roller thrust bearings commonly used in such installations wore out quickly and had to be
repaired or replaced with annoying (and expensive) frequency. Kingsbury bearings could support one hundred times the load of roller bearings with negligible wear
and were rapidly adopted for hydraulic and steamturbine use. Eventually, Pennsylvania Water & Power put them on all ten Holtwood units.
When Holtwood Unit 5 was rebuilt for sixtycycle service in 1950, the original Kingsbury bearing was found still to be in perfect condition. The bearing was inspected
again in 1969 with the same result. "Not a single part has ever been replaced", reads a plaque attached to the unit in recognition of Albert Kingsbury's singular
mechanical achievement, which made possible the design of much larger hydroelectric units, including those of the Tennessee Valley and Bonneville power authorities.
Kingsbury thrust bearings have also found wide application on the propeller shafts of ocean liners.