Patent ID: 8807246

Claim:
A downhole tool comprising: a substantially hollow body having a longitudinal axis and including an external wall having a first outer diameter; at least one arm bay formed in a portion of the external wall around a periphery of the body; at least one expandable arm located in an associated arm bay and mounted for expansion between a retracted position within the body and an expanded position in which each expandable arm describes a second outer diameter which is greater than the first outer diameter; at least one expansion mechanism for expanding an associated expandable arm between the retracted and expanded positions, wherein each expansion mechanism comprises a first elongate link and a second elongate link, said first elongate link pivotally connected to its associated expandable arm at one end position and to its associated arm bay at another end position, said second elongate link pivotally connected to its associated expandable arm at one end position and to its associated arm bay at another end position, each expandable arm being pivotally mounted at its respective end positions with respect to its associated arm bay so that each expandable arm is maintained substantially parallel to the longitudinal axis in both the retracted and expanded positions, and, during its expansion and retraction between the retracted and expanded positions; and an actuation mechanism for activating the expansion mechanism, wherein the expansion mechanism further comprises a third elongate link pivotally connected, independently from the first elongate link and the second elongate link, to its associated expandable arm at one end position and to the actuation mechanism at another end position.