Lock - Komon (English spelling) lock

A structure that allows ships to pass between water surfaces with different water levels. They are installed when connecting a river with a difference in water level to a canal, or when constructing a dam, weir, or bed dam on a river. A lock consists of a lock chamber, a lock gate, and a door chamber. A lock chamber is where ships are accommodated, and lock gates are installed at both ends. A pipeline is installed connecting the door chambers to raise and lower the water level in the lock chamber. When a ship is going from a low water level to a high water level, the lock gates at both ends are closed, the valve of the pipeline on the low water level side is opened to drain the water from the lock chamber, and after the water level inside the lock chamber is equalized to the water level on the low water level side, the lock gate on the low water level side is opened to let the ship into the lock chamber, and the lock gate is then closed. Then the valve on the pipeline on the high water level side is opened to let water into the lock chamber, and once the water level inside the lock chamber is equalized to that on the high water level side, the lock doors on the high water level side are opened to allow the ship through. The procedure is reversed when a ship is going from a higher water level to a lower water level. Panama's Panama Canal (completed in 1914) uses three locks to connect the Pacific Ocean to the Caribbean Sea via Gatun Lake, which is 26 meters above sea level. At the Three Gorges Dam on the Yangtze River in China (a gravity concrete dam, 185 meters high, completed in 2009), ships are raised and lowered over a water level difference of 113 meters using five stages of locks.

[Noboru Ikawa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

水位差のある水面間で船舶を通航させるための構造物。水位差のある河川と運河を連絡する場合や河川にダム、堰(せき)、床固めを建設する場合などに設置される。閘門（ロック）は閘室（ロック室）、閘門扉(こうもんぴ)（ロックゲート）と扉室(ひしつ)（ゲート室）からなる。閘室は船を収容する場所で、両端に閘門扉が設置される。閘室の水位を上昇、下降させるために扉室と閘室を結ぶ管路が設置される。船が水位の低いほうから高いほうに行く場合は、両端の閘門扉を閉め、低水位側の管路のバルブを開いて閘室内の水を排出し、閘室内の水位を低水位側の水位と等しくした後に低水位側の閘門扉を開いて船を閘室内に入れ、閘門扉を閉じる。そして高水位側の管路のバルブを開いて閘室内に給水し、閘室内の水位を高水位側の水位と等しくした後に高水位側の閘門扉を開いて船を通す。船が水位の高いほうから低いほうに行く場合は逆の手順になる。パナマのパナマ運河（1914年完成）は3か所の閘門で標高26メートルのガトゥン湖を経て太平洋とカリブ海を結ぶ。中国・長江(ちょうこう)の三峡ダム（重力式コンクリートダム、高さ185メートル、2009年完成）では、113メートルの水位差を5段の閘門で船を上げ下げする。

［鮏川　登］

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