Impact sprinkler
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An Impact sprinkler (sometimes incorrectly called an impulse sprinkler) is a type of Irrigation sprinkler used primarily to irrigate farm fields. It is by far the most widely recognized type of sprinkler, particularly by the sound it makes while operating. The original horizontal action impact drive sprinkler was invented by Los Angeles citrus farmer Orton Englehardt in 1933 and patented in 1935 (US Patent #1,997,901). Orton later sold it to Clem and Mary LaFetra who manufactured and marketed it under the brand name Rain Bird, which has since grown into one of the largest irrigation supply companies in the world.
The sprinkler pivots on a bearing on top of its threaded attachment nut, and is driven in a circular motion by a spring-loaded arm that is pushed back by the water stream, then returning to "impact" the stream. This produces an intermittent diffusion of the stream that provides a uniform rainfall closer to the sprinkler. Additionally, the uninterrupted straight-through flow path of impact heads makes them virtually impervious to dirt and sand in the water, making them ideal for systems running on well water. One defining feature of impact heads is that they almost always have a male pipe thread, as opposed to the female threads found on virtually all other sprinkler types. Some full-circle impact heads feature a second, short range opposing nozzle (pictured at above), which adds to the the close-in watering action provided by the rapid "return cycle" on part-circle heads.
The impact sprinkler is arguably the single most important development in the history of irrigation. Its long throw radius and remarkably uniform water distribution re-created the effect of natural rainfall, and quickly replaced the centuries-old technique of "furrow irrigation", in which trenches were dug between rows of crops and flooded.
An underground pop-up version of the impact sprinkler was introduced in 1941 and provided a means to water large lawn areas without a travelling hose-end sprinkler. When not in operation, these sprinklers disappeared out of sight below turf level. Although these were largely replaced by gear-driven "rotor heads" by the 1990s, impact sprinklers still have many advantages, including uniformity of coverage, sand and grit resistance, wind resistance, and higher flow rate, which allows for shorter operating times.
