Speedsafe — Assisted Opening System
Throughout the twentieth century, the improvement of folding knives evolved towards the fastest possible extraction of the blade from the handle. The increased speed of life and the desire of consumers to do everything in one movement, forced manufacturers to invent more and more options of knife locks, especially "push-button locks". The most famous among them, the lock with the pin on the flat spring - lever-lock, used since the XIX century, gradually gave place to the more advanced button-lock. The new lock became more convenient, easier to use and made the ejection of the blade much faster. Then came the era of single and double action knives with front ejection. Knife with OTF (out-the-front) system allowed instant blade ejection and, though not without its drawbacks, turned out to be extremely popular among the customers. All these solutions greatly simplified the use of knives, but immediately fell under the ban of the law enforcement agencies in most countries of the world.
The requirements of the law and the desires of consumers came into conflict, which prompted manufacturers to search for alternative ways of pulling the blade to bypass restrictions. As a result, the 1980s and 1990s were the period of maximum productivity of designers in this direction. Several very effective inventions were made, including:
Flipper — a protrusion on the blade for extraction from the handle with a flip;
Thumbstud — pin to press with a finger when opening;
Thumbhole — through-hole for hooking with a finger.
All of them were simple, reliable and fast enough. However, the speed of opening depended primarily on good coordination and dexterity of hands, qualities that not all people possess. A technical solution was required, the performance of which did not depend on a person and made it possible to open the knife at the same speed in any conditions.
Such a solution was the speedsafe - a patented system for opening folding knives, by the American company Kershaw. It was first used in 1998 on a knife designed by Ken Onion, one of the greatest knife masters of our time. The system consists of a rod connected to the blade, which helps to eject it after an initial impulse made by human muscles. That is, the speed - safe allows you to easily open the knife after pushing a finger on the pin, flipper or washer on the blade. All the knife owner needs to do is to overcome the primary resistance of the system and bring it out of its resting state.
The backbone of the speed-safe system is the «torsion bar» made of elastic steel and connected at one end to the handle liner and at the other to the blade. The bar sits in a special recess in the liner filled with grease to prevent corrosion and ensure spring elasticity. When folded, the torsion bar helps to keep the blade closed, protecting it from an independent, unauthorized opening. Once the blade is ejected from the handle, the rod straightens, pushing the blade out before locking it in place. The most common locks used with the speedsafe system are frame lock or liner lock, with its springs locking the heel of the blade quickly and without deviation. The knife can be closed with one hand, but the movement of the blade will be hard, because the pressure of the rod must be overcome. In terms of opening speed, a speed-safe knife is virtually the same as a push-button knife, but it is absolutely legal in many countries of the world.
For all its simplicity, the speedsafe system is not without its drawbacks. During the first decade of its use, knives with a torsion bar did not have a detent ball, which locked the blade in the closed position and created a preload when the blade was ejected. These functions were performed by the rack as the only control system of knife mechanics. If the speed-safe was dismounted or the rod broke, the blade was not held in the closed position and fell out, creating inconvenience in carrying and a risk of injury to the owner. However, in knives produced in recent years, the detent ball and the mating hole in the blade are used in parallel with the speedsafe. This allows the system to be removed completely and the knife to be used normally without speed opening. Another disadvantage is the possibility of the rack failing. Like any part that has a lot of internal stress and works in compression-straightening mode, it is subject to wear and tear. In addition, most manufacturers make such springs from carbon spring steel, which is subject to corrosion. To extend the life of the system, it requires maintenance: regular replacement of the grease in the liner recess and avoiding water getting inside.
Despite its shortcomings, the speed-safe has become an important and sought-after invention. The speed of operation, lightness, convenience and high reliability of the system were appreciated by experts and knife enthusiasts. Ken Onion won several prizes at prestigious knife shows, and the speedsafe has been used on many different models and today has a wide, and well-deserved popularity.