Patent ID: 6892809

Claim:
A coiled tubing injector apparatus comprising: a base; first and second carriages extending upwardly from the base, wherein each carriage has first and second outer plates, and at least one of the first and second carriages is movable laterally with respect to the base; and a gripper chain system mounted to the first and second outer plates of each carriage, wherein the gripper chain system comprises: a pair of spaced gripper chain drive sprockets mounted on a drive sprocket shaft for supporting a gripper chain, wherein the gripper chain is adapted to engage coiled tubing, and the drive sprocket shaft has a centerline corresponding to an axis of rotation of the drive sprockets; and a pair of spaced idler sprockets mounted on an idler sprocket shaft positioned below the gripper chain drive sprockets for supporting the gripper chain, wherein the idler sprocket shaft has a centerline corresponding to an axis of rotation of the idler sprockets, and the centerlines of the drive sprocket shaft and the idler sprocket shaft have a first distance therebetween at first ends of the drive sprocket shaft and idler sprocket shaft and a second distance therebetween at second ends of the drive sprocket shaft and idler sprocket shaft; wherein: the first and second distances are initially substantially identical so that the centerlines of the drive sprocket shaft and the idler sprocket shaft are parallel; the initial substantially identical first and second distances are established by noting the position of the first and second ends of the idler sprocket shaft relative to witness marks on the first and second outer plates; and the position of the first and second ends of the idler sprocket shaft can be adjusted to maintain a parallel relationship between the centerlines of the drive sprocket shaft and the idler sprocket shaft if the position of the first or second end of the idler sprocket shaft moves during operation.