Abstract

A driver with automatic speed and torque switching including two different drive trains which operate in parallel and are driven at the same time by a motor. One drive train provides a high-speed output while the other provides a low-speed output. A single drive head for transmitting torque to the nut is normally coupled to the high-speed output, and not to the low-speed output. The machine operates initially at the high speed for the "free rotation" of the nut. When the nut contacts the surface of the structural body, the drive coupling to the high-speed output is disabled, and the low-speed output (which formerly was not coupled to the drive head) is not at the same time coupled to the drive head. The nut is then driven much more slowly but with a higher driving torque. Within the low-speed drive train there is included a friction clutch, and adjustement means for adjusting the level of torque at which it will slip. This clutch is therefore set for the predetermined counter-torque that is to cause driving rotation to be terminated.