Two-stage universal joint

A two-stage universal joint, including:

• a sleeve, defining an axis, including a receiving groove and an assembling portion, an inner wall of the receiving groove including a plurality of first projections extending axially and a plurality of second projections extending axially, the plurality of first projections being disposed on an end of the receiving groove away from the assembling portion, an annular recession being disposed between the plurality of first projections and the plurality of second projections, the plurality of second projections being located between the plurality of first projections and the assembling portion, the plurality of first projections having respective first inclined surfaces each disposed on an end away from the plurality of second projections and having respective first abutting surfaces, each of the respective first inclined surfaces and one of the respective first abutting surfaces having an arcuate chamfer disposed therebetween, the plurality of second projections having respective second inclined surfaces each disposed on an end adjacent to the plurality of first projections and having respective second abutting surfaces, a distance from each of the respective first abutting surfaces to the axis being larger than a distance from each of the respective second abutting surfaces to the axis;
• a driving member, including a polygonal ball head which has a plurality of arcuate portions, the polygonal ball head being inserted into the receiving groove and each of the plurality of arcuate portions being abutted against one of the respective second abutting surfaces of the plurality of second projections, the driving member being slidable between a first position and a second position relative to the sleeve;
• and
• a restricting member, disposed on the annular recession;
• wherein when the driving member is in the first position, the driving member is non-swingable about the polygonal ball head relative to the sleeve;
• when the driving member is in the second position, the driving member is swingable about the polygonal ball head relative to the sleeve, and the restricting member blocks the polygonal ball head within the receiving groove.