Low torque automatic screwdriver

Claim 1

In an improved powered screwdriver including an air motor having an inlet at which to receive a source of high pressure supply air; a drive end for work engagement with a fastener member to be rotationally driven; and a clutch operative to couple the output of said motor to said drive end and operative to effectively uncouple the drive end from the motor at an encountered fastener turning resistance corresponding to a torque of predetermined value; the improvement comprising an improved disconnect and reset means responsive to uncoupling of the clutch to effect interruption of the air supply to the motor and to reset the screwdriver for subsequent operation, said improved disconnect and reset means including: a shutoff valve in the air inlet adapted to open and close the air supply to the motor; a slidable throttle rod for operating said shutoff valve between its open and closed positions; pin means having an axis of movement which intersects the axis of tool rotation, and movable radially relative to the axis of tool rotation between a first position engaging said throttle rod for preventing movement of said throttle rod in a direction to close said valve and a second position out of engagement with said throttle rod permitting said rod movement for closing said valve; cam means rotatable with said drive end including at least one radially disposed point for shifting said pin means from said first to said second position; said pin means including an apex portion for engaging said cam means, said apex portion being offset from said axis of movement of pin means; and biasing means for urging the apex portion of said pin means toward said cam means and toward said first position regardless of the operative condition of said clutch.