Powered variable seal diameter trocar employing a winepress mechanism

A surgical access apparatus (10) includes an access member having a longitudinal passageway (12) providing access to a tissue site. An elongated seal member (24) mounted to the access member has an orifice (34) with a variable inner dimension. The elongated seal member establishes a sealing relation about an instrument and is associated with a powered adjustment mechanism (52) for adjusting the variable inner dimension of the orifice. The powered adjustment mechanism includes trailing (48) and leading (44) hubs longitudinally spaced and adapted for relative rotation about an axis defined by the access member. A plurality of spokes (40) extends between the hubs and defines first and second minimum internal dimensions when in first and second conditions respectively upon relative rotation of the hubs. The spokes are arranged about the elongated seal member to adjust the variable inner dimension of the orifice upon relative rotation of the hubs. A powered motion generator (62) effects relative rotation between the hubs.