A duct section or other load to be moved axially along a bore hole has two reciprocating drivers mounted on it and two sets of gripping elements. Each driver reacts axially between the load and a set of gripping elements to move the gripping elements relative to the load through a defined stroke in each...http://www.google.fr/patents/US4141414?utm_source=gb-gplus-shareBrevet US4141414 - Device for supporting, raising and lowering duct in deep bore hole
Device for supporting, raising and lowering duct in deep bore hole
