A twistlock and corner casting together form a standardised rotating connector for securing shipping containers. The primary uses are for locking a container into place on container ship, semi-trailer truck or railway container train; and for lifting of the containers by container cranes and sidelifters.
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.
The female part of the connector is the 7×7×4 1⁄2 in (180×180×110 mm) corner casting, which is fitted to the container itself, and has no moving parts, only an oval hole in the bottom. The hole is an oval 4.9 in (124.5 mm) on the long axis with two flat sides 2.5 in (63.5 mm) 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 4.1 in or 104.1 mm long and 2.2 in or 55.9 mm wide), and then the top portion (normally pointed to make insertion easier) is rotated 90° so that it cannot be withdrawn. The mechanism is the same as that of a Kensington lock, but on a much larger scale. The maximum size and position of the holes in the connector is defined in international standard ISO 1161:1984.
The tensile strength of a twistlock is rated at either 20 or 25 tonnes.
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 by the mover) does the twistlock become dangerous to move the crate by. The male part is placed on vehicles and equipment that are inspected very frequently and will work with all containers while working effectively.
Corner casting on a shipping container. The twistlock proper is done through a larger oval hole on the bottom.
Twistlocks on the base of a container ship. Foreground: unlocked; background: locked. The turnbuckles are "lashing rods" used for additional stability
Special types of twist-locks are also used in Double-stack rail transport to secure the lower stack container with the upper one.
|Wikimedia Commons has media related to twistlocks.|
- Peck and Hale (2000). "Container Stowage and Securing Systems" (PDF). West Sayville, NY: Peck & Hale. Retrieved 2011-03-01.
- Levinson, Marc (2006). The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger. Princeton, N.J: Princeton University Press. ISBN 0-691-12324-1.
- Nichols, C. Reid; Williams, Robert G. (November 2008). Encyclopedia of Marine Science. Infobase Publishing. p. 119. ISBN 978-0-8160-5022-2. Retrieved 8 March 2011.
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