Patent ID: 7690618

Claim:
A position adjustment mechanism, comprising two cylindrical portions, a first one of the cylindrical portions being slidably disposed inside a second one of the cylindrical portions, said second cylindrical portion defining a chamber having a closed upper end containing a fluid inlet/outlet opening, said first cylindrical portion arranged in sealing relation within said chamber, and further comprising means for moving said cylindrical portions relative to each other by introducing and removing pressurized fluid to said chamber via said inlet/outlet opening in said second cylindrical portion, wherein one of the cylindrical portions has at least three detents and the other cylindrical portion has at least three members for engaging in respective ones of said detents to hold said cylindrical portions in a first position, the members being removable from said detents to allow said cylindrical portions to move into a second position, wherein the detents and members are equally spaced around the first and second cylindrical portions.