Spring-coupled power screwdriver

摘要

A helical spring couples a drive shaft geared to the motor with the work spindle. With this arrangement hard screwdriving operations can be extended in time so that time is added for the drive motor to come a stop after it is switched off. Transducers are provided for measuring the torque at which motor switch-off occurs, and also the cumulative angle of rotation, the latter for detecting defective screws. No switchdown of the drive speed is necessary before the screw is driven home.