Shaft coupling

A shaft coupling between a first shaft having an inside wall and a second shaft telescopically overlapping an end of said first shaft and having an outside wall facing said inside wall of said first shaft comprising:

• a plurality of concave inside linear grooves in said inside wall of said first shaft parallel to a longitudinal centerline of said shaft coupling arrayed evenly around said longitudinal centerline of said shaft coupling,
• a plurality of concave outside linear grooves in said outside wall of said second shaft parallel to said longitudinal centerline of said shaft coupling arrayed evenly around said longitudinal centerline of said shaft coupling,
• said outside linear grooves facing said inside linear grooves and cooperating therewith in defining a plurality of linear cylindrical passages between said first shaft and said second shaft parallel to said longitudinal centerline of said shaft coupling arrayed evenly around said longitudinal centerline of said shaft coupling,
• a pair of barrel-shaped lugs in each of said linear cylindrical passages each made of an elastomeric material having a low coefficient of sliding friction and having a convex surface of revolution about a centerline of said barrel-shaped lug defining an outside surface thereof bearing tangentially against corresponding ones of said inside linear grooves and said outside linear grooves and operative to couple together said first shaft and said second shaft for unitary rotation about said longitudinal centerline of said shaft coupling and for relative linear translation in the direction of said longitudinal centerline of said shaft coupling, and
• a integral beam spring integral with and between each pair of said barrel-shaped lugs, said beam spring being made of said elastomeric material and resiliently tipping each of said barrel-shaped lugs endwise to eliminate dimensional clearance between each of said barrel-shaped lugs and corresponding ones of said inside linear grooves and said outside linear grooves.