Patent ID: 9488016
Filing Date: 2016-11-08
CPC Classification: B66D,E21B

Claim Text:
1. An apparatus for injecting or withdrawing a continuous string into and from a wellbore, the apparatus comprising: a plurality of endless drive conveyors positioned on different respective sides of an upright pathway in which an upright length of the continuous string is receivable, each endless drive conveyor comprising an endless chain and a plurality of gripper dies coupled to the endless chain, each gripping die having a gripping face that faces outwardly from the endless chain and is shaped to engage a periphery of the continuous string and a base surface that faces inwardly from the endless chain, the endless chains being arranged for driven movement around respective closed-loop paths on the different sides of the upright pathway such that the gripper dies of each endless chain are conveyed in a same direction along the upright pathway at the respective side thereof during a portion of the respective closed-loop path; a plurality of skates respectively residing on the different respective sides of the upright pathway with the closed-loop path of each endless chain closing around a respective one of the skates, each skate carrying a plurality of spherical balls that are exposed on an upright side of the skate that faces toward the pathway; and a force application mechanism operable to force the skates toward the upright pathway for clamping of the upright length of the continuous string between the gripping faces and rolling movement of the endless chains over the spherical balls exposed on the upright side of the skate that faces toward the pathway; wherein the spherical balls of each skate are exposed on the upright side of said skate through one or more gaps at said upright side that each measure less than a diameter of said spherical balls to prevent exit of said spherical balls from said upright side of the skate.