Impact tool torque limiting control

Claim 1

IN A ROTARY IMPACT TOOL INCLUDING A ROTARY ANVIL AND A ROTARY HAMMER ADAPTED TO PERIODICALLY STRIKE THE ANVIL, A COUPLING FOR TRANSMITTING THE ROTARY HAMMER IMPACTS FROM THE ANVIL TO A WORKPIECE AND LIMITING THE MAXIMUM TORQUE OF THE TRANSMITTED IMPACTS TO A SELECTED PREDETERMINED VALUE OF TORQUE WHICH CAN BE READILY ADJUSTED, SAID COUPLING COMPRISING: A TORSION SPRING HAVING ONE END NON-ROTATABLY CONNECTED TO SAID ANVIL AND ADAPTED TO HAVE ITS OTHER END CONNECTED TO A WORKPIECE; AN ADJUSTMENT MEMBER MOUNTED ON THE OTHER END OF SAID TORSION SPRING; AND ENGAGEMENT MEANS INTERCONNECTING SAID ADJUSTMENT MEMBER TO BOTH SAID SPRING AND TO SAID ANVIL FOR LOCKING SAID ADJUSTMENT MEMBER AGAINST ROTATION RELATIVE TO SAID SPRING AND ANVIL IN AT LEAST ONE ROTARY DIRECTION, SAID ENGAGEMENT MEANS INCLUDING A WORM SCREW ENGAGING A SERIES OF WORM GEAR TEETH FOR ROTATING THE OPPOSITE ENDS OF SAID SPRING RELATIVE TO EACH OTHER AND WINDING THE SPRING TO A PRE-STRESSED TORQUE AS SAID WORM SCREW IS ROTATED.