US Patent 7240727 Armored stripper rubber

An armored stripper rubber is provided that protects the drillstring bore of the stripper rubber from substrate infiltration, yet pivotally dilates to facilitate the passage of drillstring components through the bore while effectively maintaining a fluid-tight seal. Additionally, the stripper rubber substantially inhibits resilient contraction of the stripper rubber to an internal bore diameter smaller than a pre-selected internal diameter. The armored stripper rubber, or armadillo, substantially prevents rubber inversion and puckering under high operational well pressures. Also provided are stripper rubber inserts and insert assemblies.