US Patent 9351734 Spring loaded anvil retainer

A surgical stapling device including a handle assembly, a body portion extending distally from the handle assembly, a head portion including an anvil retainer and a shell assembly, the anvil retainer being movable in relation to the shell assembly between unapproximated and approximated positions, a tube surrounding a portion of the anvil retainer, wherein the anvil retainer includes a distal annular protrusion for releasably engaging an anvil assembly and wherein the anvil assembly includes a center rod.