US Patent 7025747 Valve assembly including diameter reduction structure for trocar

A valve assembly and diameter reduction structure for trocar employing a movable diameter reduction structure. The diameter reduction structure is positioned in proximity to a first seal and includes a plurality of stand off members movable between a first position, a second position, and a third position. The diameter reduction structure in the first position reduces the likelihood of the first seal losing its integrity by limiting excessive off-axis and angular movements of small diameter surgical instruments. When large diameter surgical instruments are positioned through the trocar, the diameter reduction structure pivots to accommodate the passage of larger diameter surgical instruments without any operational adjustments.