Release / Actuation / Shut-off
Release, actuation and shut-off involve the release or holding of a force.
Systems are released, actuated and shut off by means of activation energy in an energy converter. Solenoids, pyrotechnics, pneumatic and hydraulic actuators or manual force are used as energy converters.
It is crucial that these processes are executed quickly, reliably and precisely. It may be that systems only need to be released once – but when they are, this must happen reliably and within milliseconds. And the forces which are released are very high in comparison to the energy that releases them.
In safety systems it is sometimes necessary that these release units, shut-off units and actuation units have their own energy supply and are monitored by the control.
Release and shut-off are generally executed by means of pins and ratchets.
Electromagnetic releases are particularly suitable, as they can be tested in an inspection. They are reversible – which means that they can actuate repeatedly.
In pyrotechnical release systems, on the other hand, often only resistances can be measured. The release system itself cannot be tested, however.
One example of a safety-relevant release using electromagnetic and pyrotechnical release systems is the roll-over protection system in a convertible.
Many modern convertibles have an active roll-over protection system, which can extend a roll bar to protect the passengers’ head region in less than 150 milliseconds, should the vehicle overturn. The roll bars have very strong pressure springs, which extend the bar. Electromagnetically driven release systems are mainly used to release the forces acting on the bars. The incorporation of airbags into almost every modern motor vehicle has also resulted in the use of pyrotechnical actuators in release systems.
As the solenoid has considerably lower forces than pyrotechnical devices, the acting spring force must be transmitted from the roll bar by a mechanism, so that it can be switched by the solenoid. A ratchet system may be used, for example, which has both a locking function and a transmission function.
As a solenoid manufacturer, Thomas develops and manufactures solutions for release systems, actuation systems and shut-off devices.
