Twistlock

The twistlock was developed in Spokane, Washington, in the 1950s by transport engineer Keith Tantlinger. The relative obscurity of this invention belies its importance to a more efficient world trade and transport, as the Tantlinger lock made handling and stacking standard containers much easier. Tantlinger later released his patent royalty-free, which enabled the twist-lock to become an industry and international standard. A major advantage of this approach to attachment is that containers, which may be stored or transported without being inspected for months at a time, do not require any maintenance in order to function effectively. Even with long-term exposure to the weather the container remains as simple to move as ever. Only when corrosion is very extensive (to the extent of being easily visible) does the twistlock become dangerous to move the crate. The male part (which is more exposed and susceptible to damage) is placed on vehicles and equipment that are inspected very frequently, and will work with all standard containers. ==Mechanism==

The female part of the connector is the corner casting, which forms each of the eight corners, welded to the container itself, and has no moving parts, only an oval hole in the tops of the four upper corners, and in the bottom of the four lower corners. The hole is an oval on the long axis with two flat sides apart. The male component is the twistlock, which is fitted to cranes and transport bases. This can be inserted through the hole (it is roughly long and wide), and then the top portion (normally pointed to make insertion easier) is rotated 90°, so that it cannot be withdrawn. The mechanism is similar to that of a Kensington lock, but of a much larger size. The maximum size and position of the holes in the connector defined in the original patent and is now defined in international standard ISO 1161:2016. The tensile strength of a twistlock is rated at either . Some twistlocks have built-in levers or mechanisms, while simpler versions require tools for installation or removal. Some twistlocks are permanently installed (e.g., on the decks of container ships or on the beds of semi-trailers), while others are temporarily installed and removed as needed, for instance to stack containers securely on ships, or in storage yards. File:Automatic twistlock.jpg|Mid-locks are manually attached to the bottom corners of an upper container, and will automatically lock into the top corners of the lower container when stacked. File:Container twistlock.JPG|Closeup of twistlock at Maritime Museum of Finland File:Container Verriegelung 1.jpg|High-quality retractable twistlock File:Container lashed.jpg|Twistlock engaged with shipping container at sea File:JR貨物関連 = コンテナ制限表記マーキング 6158 (cropped).jpg|Close-up of ISO standard container bottom corner casting. Twistlocks engage through a large oval hole on the bottom File:Container 【 22G1 】 WTPU 010097(1)---No,1 【 Pictures taken in Japan 】.jpg|Standard 20-foot ISO shipping container with standard corner castings on each of its eight corners. File:Container lock----6005【 Pictures taken in Japan 】.jpg|Close-up of corner casting with twist-lock in place and locked.] ==Applications==

Double male twistlocks (midlocks) are also used to lock two stacked containers vertically, for example in double-stack rail transport or on well cars. File:Containerverriegelung.JPG|Rusty twistlock on a semi-trailer File:Container on trailer with twistlocked.jpg|Twistlock attachment to a trailer (Japan) File:First level of twistlocks on a containership deck.jpg|First level of twistlocks on the deck of a container ship File:Twistlock and lashing rods.jpg|Twistlocks on deck of container ship. Foreground: unlocked; background: locked. The turnbuckles are "lashing rods" used for shoring File:Container lock----6031【 Pictures taken in Japan 】.jpg|Loosely stacked tank containers, without twistlocks to tie their corners together, illustrating how easily the top one might shift off the bottom one File:Container handling 6274 【 Pictures taken in Japan 】.jpg|Skystacker attaching to just two top corner castings on one side of 20-foot container File:NZ Defence Force assistance to OP Rena - Flickr - NZ Defence Force (19).jpg|Grounded container ship, the off New Zealand, 5 October 2011. Some of the bottom containers collapsed, but many twistlocks held, resulting in the cargo stacks falling over. ==Notes==