US Patent 7857187 Surgical stapler with tiltable anvil assembly

A surgical stapling device comprises a tiltable anvil assembly. The anvil assembly includes a center rod and a head assembly which is pivotally secured center rod. The head assembly includes a housing, a post, an anvil plate and a backup member. The backup member is movably positioned about the post from a first position preventing pivotal movement of the head assembly to a second position permitting pivotal movement of the head assembly. A retainer member is positioned between the backup member and the housing to prevent movement of the backup member from its first position to its second position until a predetermined force has been applied to the backup member.