US Patent 7037060 Shrinkage compensator for building tiedowns

An automatic, self-energized, length extending, take-up unit for general use in wall hold down systems. The take-up unit is generally installed as a separate element, independent of threaded retaining elements of a hold down system. One embodiment includes an internal, preloaded, coil spring to rotate a threaded sliding member relative to a threaded base member, thereby to extend a height of the take-up unit. A trigger mechanism may be included to prevent unintended actuation of the unit. Additionally, a safety mechanism may be included to prevent inadvertent separation of a base member and a sliding member, thereby to prevent loss of a preload in an energizing spring.