Personnel in and on moving vehicles can be exposed to high-acceleration environments, such as collisions or rapid changes in speed, resulting in rapid relative motion between the vehicle and passengers. These environments pose a risk of injury due to contact with vehicle or equipment structures, as well as the risk of accidental ejection from the vehicle. The risk of injury is particularly pronounced for personnel who cannot be restrained by typical seat restraint systems due to mobility requirements, such as crew members in the cargo hold of military helicopters.
Current systems used to restrain helicopter crew members include gunner's belts with fixed-length tethers or reel systems. A disadvantage of fixed-length tethers is that the user can swing freely at any point within the tether's range. Some tethers are not adjustable in length; and some require constant manual adjustment by the user, disrupting mission-critical tasks.
Reel systems address some of the drawbacks of fixed-length tether systems by using a retractable reel that utilizes the slack in the tether between the user and the reel. An acceleration-sensing drum locking mechanism can lock the drum to prevent further movement of the user or crew member in the event of a high-acceleration event.
The implementation utilizes a spiral spring as the primary mechanism. Spiral springs are designed to provide a smaller torque range throughout the entire operation compared to typical coil springs. This smaller torque range means that force is required to resist webbing pull-out and achieve cord retraction, without applying torque large enough to cause user fatigue.
Most power springs are manufactured by tightly winding spring material onto a mandrel and attaching the free end to a housing. The spring's natural tendency to expand provides momentum to the mandrel or housing, thus generating usable torque. The total torque generated increases as the spring is wound tighter and decreases as it unwinds.
Power springs can be an attractive option for your application; their compact size and simple design contribute to their relatively hassle-free operation. The combination of materials, sizes, and options available for power springs makes them an attractive consideration for meeting your rotational needs.
