Crown block shifting apparatus and method

摘要

A drilling rig derrick is adapted to direct the hoist lines reeved between the crown block and the traveling block such that they enter both in a vertical direction if the traveling block is moved laterally to clear the work area over the rotary table. Arrangements are provided to move the crown block laterally, and to move it back over the rotary table. Alternate provisions displace the reeved lines with idler sheaves to move the traveling block only and direct the reeved lines such that they enter both crown block and traveling block sheaves in a near vertical direction. Methods for both options are provided.