A pressure drop through the bit maintains the tool in the open position while the return springs close the pistons when flow decreases.

随后钻头处的压力降使扩眼工具处于打开状态，当流速下降时弹簧将活塞收回至原处。

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Billionaires, celebrities and royals will soon be converging on the horse racing town of Saratoga Springs, New York for the chance to drop as much as a couple million dollars on a future Kentucky Derby winner.

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Trent will drop the video cameras, the size of a salt shaker, into acidic hot springs by stretching a rope across each pool and slowly lowering cameras and instruments.

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