Method and device for position locked power tool operation for correction of unacceptable screw joint tightening results

A control device for a power wrench arranged to prevent negligence of at least one unacceptably tightened screw joint on an assembled object, the power wrench comprising at least one operation parameter indicating unit;

• wherein a position sensing system is arranged to indicate continuously an actual multi-dimensional position of the power wrench during tightening of the at least one screw joint on the object to be assembled;
• wherein a control unit is arranged to compare obtained operation parameter values indicated by said at least one operation parameter indicating unit at each tightening operation with predetermined operation parameter limit values, and to issue an OK or a NOK signal depending on said limit values being passed or not for each screw joint;
• and
• wherein said control unit is arranged to lock power wrench operations to the object position for which a NOK indicated screw joint tightening result has been indicated, and to enable the power wrench for tightening operations on other objects than that for which said NOK indicated position has been indicated only as said NOK indication is removed.

A method for ensuring correction of occurring non-acceptably tightened screw joints on objects to be assembled by utilizing a power wrench having at least one operation parameter indicating unit, and a position sensing system for indicating an actual position of the power wrench, the method comprising:

• indicating continuously the position of the power wrench during tightening of the screw joints on the objects to be assembled;
• providing the tightening result as indicated by the parameter indicating unit in terms of OK and NOK signals for each screw joint in relation to predetermined tightening parameter limit values;
• locking the power wrench operation to the object on which a NOK indication for at least one screw joint has been received;
• and
• enabling the power wrench for operation at other objects only when the NOK indication for at least one screw joint on the object has been removed.