Bi-directional traction apparatus

摘要

A traction apparatus ( 1 ) for propulsion along a bore comprises first and second traction members ( 6 ) having outwardly extending legs ( 14 ). A propulsion system for operating the traction members ( 6 ) comprises a turbine-driven shaft ( 7 ) which drives the traction members ( 6 ) by way of bearing members ( 15 ). In a first phase, one of the legs of the first traction member is moved in one direction whilst in contact with the traction surface to impart the propulsion force at the same time as one of the legs of the second traction member is moved in opposite direction whilst out of contact. In a second phase one of the legs of the second traction member is moved in said one direction whilst in contact with the traction surface to impart the propulsion force at the same time as one of the legs of the first traction member is moved in opposite direction whilst out of contact.