Telescopic umbrella shaft means with concave hexagonal sides

摘要

A telescopic umbrella shaft includes at least an inner tube, and an outer tube telescopically slidably engageable with the inner tube, with each tube having a cross section of hexagonal shape consisting of six arcuate rectangular sides each arcuate rectangular side concaved inwardly towards a longitudinal axis of the shaft, and every two neighboring arcuate rectangular sides converging to form a reinforcing rib convex outwardly from the longitudinal axis, with each reinforcing rib formed as an inversed-U shape and having a longitudinal strip defining a horizontal plane perpendicular to a normal line between the longitudinal axis and an apex intersected by the two neighboring arcuate rectangular sides of the tube, thereby forming a balanced moment of inertia of the concave and convex portions of the tube when dynamically rotating the central shaft for greatly enhancing the stability and strength of the umbrella shaft.