Patent ID: 7837176

Claim:
An apparatus for positioning an orifice plate, the apparatus comprising: a body having a straight flowbore; an orifice plate carrier moveably disposed in the flowbore, wherein the orifice plate carrier includes a pair of machined outer side surfaces; and a drive assembly, the drive assembly comprising: a rotatable shaft inserted though the body, wherein the shaft is rotatably coupled to the orifice plate carrier; and a pair of stuffing boxes disposed between the shaft and the body, and coupling the shaft to the body; wherein opposed inner ends of the stuffing boxes engage the pair of machined outer side surfaces of the carrier; wherein: the body includes two outer surfaces, each outer surface equidistant from a center of the flowbore as measured parallel to a first axis that is normal to a longitudinal axis of the flowbore; the drive assembly includes a pair of gears disposed on the shaft, each gear rotatably constrained relative to the shaft; the pair of stuffing boxes is concentrically disposed on the shaft, each stuffing box inner end engaging one of the gears, wherein each end is equidistant from one of the outer surfaces as measured parallel to the first axis; a center of an orifice through the orifice plate is equidistant between the ends of the stuffing boxes as measured parallel to the first axis; and rotation of the shaft displaces the plate carrier in a direction parallel to a second axis that is normal to the first axis and the longitudinal axis.