Downhole device
A stop collar or like device is formed in one piece to have a portion for a tool to be attached. Movement of the tool allows the collar to be drawn tightly into engagement onto a pipe or other tubular member. A bow centraliser has alternate bows longitudinally offset to reduce initial insertion force. The centraliser may be formed to have end bands of the type used in the stop collar.
1. A centralizer having first and second opposing end collars, the end collars being axially separated by plural spring bows, the spring bows forming a generally convex curve, with a first set of bows extending from the first end collar substantially axis-parallel for a first distance before extending via the curve into the second end collar, and a second set of bows extending curvedly from the first end collar and into a substantially axis-parallel portion at the second end collar, whereby the centralizer is formed of a single piece, the first set of bows longitudinally offset from the second set of bows whereby upon insertion into a bore one of the first set of bows and the second set of bows engages the bore before the other set, wherein each bow of the first set is between two bows of the second set and each bow of the second set is between two bows of the first set around the end collars.
2. The centralizer according to claim 1 , in which at least one of the end collars comprises a generally cylindrical band having at least one arcuate portion with opposing end regions, the end regions being coupled together by a connecting portion having a pair of arm portions extending on respective sides of a body portion, distal ends of the arm portions extending into the end regions, the body portion having a formation for engagement therein of a tool whereby rotation of the body portion by the tool varies the size of the end collar, the end collar further comprising means for securing the arm portions with respect to an adjacent end region so that the end collar can be locked.
3. The centralizer according to claim 2 , in which the at least one end collar has a plurality of arcuate portions each having respective end regions, and a corresponding plurality of connecting portions.
4. The centralizer according to claim 2 , in which the connecting portions of the end collar are generally S shaped.
5. The centralizer according to claim 2 , in which the or each arcuate portion of the end collar has prolongations to form guides for constraining sideways movement of the arm portions.
6. The centralizer according to claim 5 , wherein the guides have teeth to interact with counterpart teeth on the arm portions to form the engagement means.
7. The centralizer according to claim 2 , wherein the at least one end collar is substantially circular with an axis, the or each arcuate portion having a first axis-parallel width and the arm portions having a second axis-parallel width that is less than the first width.
8. The centralizer according to claim 2 , being formed of micro-alloy steel.