Abstract: A rivet nut tool has a primary gear driven by a motor and a gear assembly coupled to the primary gear for rotation for moving a pull screw by a movement distance to achieve a stroke. The tool has a selection button for selecting a stroke value and a pull-riveting force. A control processor receives the selected stroke value and pull-riveting force. A count sensor is used to measure the rotational movement of a primary gear in terms of signal counts for determining the stroke achieved by the pull screw. The selected stroke value is presentable as a preset count value. When the signal count reaches the preset count value, or the motor current exceeds the current needed for the selected pull-riveting force, the control processor is configured to reverse the rotation direction of the motor so as to return the pull screw to its start position.

Abstract: A flexible friction driving device has a driving gear, a driven gear, a hexagonal sleeve, a damping ring, an elastic ring and two bearing seats, wherein the driving gear is mounted below the driven gear and engaged with the driven gear; the hexagonal sleeve is disposed between the two bearing seats, and the damping ring and the driven gear are successively sheathed on the hexagonal sleeve; a cap and the elastic ring are placed in an opening at one end of the driven gear; the elastic ring compresses the damping ring onto a cylindrical outer surface of the hexagonal sleeve; power from a motor is transferred to the driven gear by the driving gear; and, the power is flexibly transferred to the hexagonal sleeve by the friction of the inner holes of the damping ring and the driven gear against the cylindrical outer surface of the hexagonal sleeve.