Self-locking hooks offer many clear benefits over sling or standard hooks, all contributing to enhanced safety in their lifting operations, according to Felix Nyberg, global product manager at The Crosby Group.
Self-locking hooks close by themselves as soon as a load is placed in the bowl of the hook and lifting begins. Once it closes, it cannot open again until the load is released from the hook.
The self-locking hook concept was launched as the BK model by Gunnebo Industries in the 1960s, primarily to improve safety on construction sites where, previously, hooks were being rigged without any latch at all.
Lifting in the construction industry has always been difficult as there is a lot of variability in the loads. Equipment also undergoes a lot of wear as many people are handling the lifting gear and lifting various objects, which often can result in damage to spring latches, like those on a sling hook. This either leads to the lifting gear being taken out of service, potentially delaying work on site, or it being used without the latch, leading to a hazardous lift. The more durable latch on a self-locking hook can prevent delays and unsafe practices, while always remaining closed when under load.
Common construction applications where self-locking hooks can provide safety benefits are wire rope slings, chain slings, and as a connection point between a shackle (or hook) and a sling coming from an excavator.
History of self-locking hooks
In the early 1960s, Karl-Axel Wahlström and Stig Lindgren were credited for the first prototype, hand-carved out of wood—a simpler prototyping method than the 3D printing we use today. They called it the ‘BK’ hook, an abbreviation of ‘Byggnadskrok,’ which in Swedish is a combination of the word ‘byggnads,’ meaning construction, and ‘krok,’ meaning hook. The product was patented and released to the market in 1965.
The BK and Crosby Shur-Loc hooks produced by The Crosby Group today are very similar, and both are now designed to avoid fingers being pinched when opening the hook. Pinch point injuries are one of the most common injuries at worksites and designing a product that will help minimize that risk is critical.
Today, The Crosby Group offers clevis self-locking hooks that connect directly to a chain sling; ball-bearing swivel hooks that can rotate under load; a Griplatch hook with a latch that connects to the body for improved side-stability and reduced weight; galvanized hooks for severe-weather protection; and even a special self-locking version for skip-loaders.
Source: The Crosby Group
