Adjustable torque limiting assembly

Abstract

An adjustable torque limiting assembly includes a first wrap spring mechanism which provides a readily adjustable torque transmission limit and a second coaxially disposed wrap spring mechanism which provides a mechanical signal that the torque limit has been reached. This signal may be utilized to terminate an energy supply to a prime mover associated with the torque limiting assembly. The first wrap spring mechanism generally includes a wrap spring in which the spring moment and thus the slip or overrunning torque threshold may be readily adjusted. The second wrap spring assembly likewise includes a wrap spring which is activated only subsequent to slip of the first wrap spring and enlarges to engage a concentrically disposed control sleeve. The control sleeve then rotates and activates an associated shut-off mechanism. Drive from the first wrap spring assembly to an output shaft is through an overrunning clutch assembly which allows energy in the wrap springs to dissipate and the springs to wind down and return to their start positions when power to the torque limiting assembly is removed.