Automatic wrench for screwing a pipe string together and apart

Claim 1

An automatic wrench for screwing together and apart a string of pipes joined with threaded collars, said automatic wrench comprising: a first base; a high-torque device mounted on said first base and including: a rotatable clamping means having grippers adapted to embrace a pipe; an actuator for bringing together and apart the grippers of said rotatable clamping means, operatively connected with said grippers; and a rotation actuator, operatively connected with said rotatable clamping means; a second base mounted on said first base; a low-torque device mounted on said second base and including: a spinning clamping means having grippers adapted to embrace the pipe; an actuator for bringing together and apart the grippers of said spinning clamping means, operatively connected with said grippers; and a spinning actuator operatively connected with said spinning clamping means; a locking device mounted on said first base under said high-torque device and comprising: a locking clamping means having grippers adapted to embrace a pipe string on the external side surface of a threaded collar; an actuator for bringing together and apart the grippers of said locking clamping means, operatively connected with said grippers; and a means for a movable attachment of said second base on said first base; and a control system comprising: a system of detectors, including: a torque detector installed on said high-torque device for delivering a signal when the torque developed by said high-torque device reaches as preset value; and a rotation angle detector installed on said high-torque device for delivering a signal when the angle of rotation of said rotatable clamping means with respect to said locking clamping means reaches a preset value; a control unit for generating control commands based upon the signals of the detectors of said system of detectors, said control unit comprising a unit monitoring the duration of the execution of a command and an AND gate, and the AND gate, upon receiving the signals from said torque detector and rotation angle detector within a preset time measured by said unit monitoring the duration of the execution of a command, outputs a signal indicative of the end of the rotation of the pipe by said high-torque device; and a system of electrically controlled actuating mechanisms acting upon said actuators of said devices under commands from said control unit.