Expandable Torque Tool

An apparatus for engaging and rotating a workpiece, comprising:

• a body having a longitudinal axis and an axially extending cavity;
• the cavity having three receptacles spaced around and joining each other at corner ridges, the receptacles opening inward toward the axis, each of the receptacles having a receptacle cylindrical surface extending from one of the corner ridges to another of the corner ridges, each of the receptacle cylindrical surfaces having an center point radially spaced outward from the axis;
• three jaws, each of the jaws having a cam portion fitting within one of the receptacles and being rotatably slidable in said one of the receptacles an increment, and a workpiece engaging portion protruding from the body, each of the cam portions having a center point that coincides with one of the receptacle center points;
• each of the cam portions having a cylindrical outer surface that is received within one of the receptacles, each of the cam portions having a pair of flat flanks extending from the cylindrical outer surface toward the axis, the flat flanks intersecting each other at an inner corner, each of the flanks of each of the cam members abutting and being slidable relative to one of the flanks of another of the cam members;
• each of the engaging portions having an outer surface configured to engage a hole within the workpiece;
• wherein
• while in a contracted position, the inner corners are located on the axis;
• and
• an increment of rotation of the body relative to the jaws causes the inner corners of the flanks to move away from each other and outward from the axis to an expanded position;
• and
• while in the expanded position, the outer surfaces of the engaging portions define a circumscribed diameter that is greater than while in the contracted position in order to grip the hole in the workpiece to transmit torque from the body to the workpiece.

A method for engaging and rotating a workpiece with a tool, the tool comprising:

• a body having a longitudinal axis and an axially extending cavity;
• the cavity having a plurality of partly cylindrical receptacles spaced around and opening inward toward the axis;
• a plurality of jaws, each of the jaws having a cam portion within one of the receptacles and a workpiece engaging portion protruding from the body;
• each of the cam portions having a partly cylindrical outer surface that is received within one of the receptacles, each of the cam portions having a pair of flat flanks that intersect each other at an inner corner, each of the flanks of each of the cam members abutting one of the flanks of another of the cam members;
• aligning the inner corners with the axis to define a contracted position and inserting the engaging portions into a hole within the workpiece;
• rotating the body an increment of rotation relative to the jaws, causing the inner corners of the flanks to move outward from the axis and the outer surfaces of the engaging portions to move from the contracted position to an expanded position in gripping engagement with the workpiece;
• and
• continuing to rotate the body to transmit torque from the body to the workpiece.