Patent ID: 7143848

Claim:
An expandable centralizer for centering a tool in a wellbore having an opening larger in diameter than the diameter of an opening through which the expandable centralizer can freely pass the expandable centralizer comprising: a body connectable in a workstring, said body having a bore defined therein running axially therethrough, said body including: a first portion being substantially cylindrical in shape and having a substantially circular cross-section of a first diameter; a second portion being polyhedral in cross-section and having a plurality of faces disposed parallel to said bore; a plurality of centralizing members, one of said centralizing members being located, respectively, on one of said faces: actuating means for moving said centralizing members from a first position within said first diameter to a second position wherein portions of said centralizing members are located outside said first diameter; wherein said second position is variable depending on said actuating means; wherein there are at least three centralizing members; wherein said faces are identical and are arranged equidistantly around said body; wherein there are three faces, wherein said second portion has a triangular cross-section, and wherein each face has an associated centralizing member arranged thereon; wherein each centralizing member includes a pivot point and each centralizing member is pivoted at said pivot point against its associated face; and further including a spring located at each of said pivot points such that each member is returned to said first position from said second position on cessation of operation of said actuating means.