US Patent 7963378 Corrugated tubular energy absorbing structure

An energy absorbing tubular structure is formed of a molded or extruded polymer. The tube has a quadrangular cross-section with rounded corners. The walls of tube are corrugated with alternating convex and concave corrugations surfaces having a continuous constant radius, preferably with no flat spots. The corrugated walls have a constant thickness. The corrugations progressively deform during impact thereby providing a near perfect square wave force vs. deflection energy absorption curve at any predetermined nearly constant force level. The tube may be filled with polymer foam to vary the impact performance of the structure.