Impact tool torque limiting means

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 COMPRISING A BARREL MOUNTED ON THE OTHER END OF SAID TORSION SPRING AND SURROUNDING SAID SPRING AND SAID ANVIL; ENGAGEMENT MEANS INTERCONNECTING SAID ADJUSTMENT MEMBER TO BOTH SAID SPRING AND TO SAID ANVIL FOR ALLOWING SAID MEMBER TO SLIDE LONGITUDINALLY RELATIVE TO SAID SPRING AND ANVIL AND FOR LOCKING SAID ADJUSTMENT MEMBER AGAINST ROTATION RELATIVE TO SAID SPRING AND ANVIL IN AT LEAST ONE ROTARY DIRECTION, SAID ENGAGEMENT MEANS INCLUDING A SET OF INTERENGAGING HELICAL SPLINES AND GROOVES EXTENDING AT A SUBSTANTIAL ANGLE RELATIVE TO THE LONGITUDINAL AXIS OF SAID TORSION SPRING; MEANS FOR FORCING SAID ADJUSTMENT MEMBER TO SLIDE LONGITUDINALLY ALONG SAID SPRING TO CAUSE SAID HELICAL SPLINES TO SLIDE ALONG SAID HELICAL GROOVES FOR ROTATING THE OPPOSITE ENDS OF SAID SPRING RELATIVE TO EACH OTHER AND WINDING THE SPRING TO A PRESTRESSED TORQUE, SAID MEANS FOR FORCING SAID ADJUSTMENT MEMBER AXIALLY ALONG SAID SPRING INCLUDING AN EXTERNALLY THREADED COLLAR ROTATABLY MOUNTED ON SAID ANVIL AND ENGAGING INTERNAL THREADS ON SAID BARREL; AND MEANS FOR PREVENTING SAID COLLAR FROM SLIDING AXIALLY FORWARD ON SAID ANVIL DURING THE ADJUSTMENT OF SAID BARREL.