A locking differential includes a pair of clutch members that are biased together by a resilient disc and friction pack assembly toward a cross pin that extends diametrically across the central chamber of a cylindrical housing driven by the drive shaft of a vehicle, thereby to drive a pair of side gears and the output shafts splined thereto. The shaft has a hollow cavity formed therein and extending along a major length of the shaft and terminating subjacent to the proximal end. The compounds are generally aryl sulfonamide derivatives and are useful in pharmaceutical compositions, methods for the treatment of CCR2-mediated diseases, CCR9-mediated diseases, as controls in assays for the identification of CCR2 antagonists and as controls in assays for the identification of CCR9 antagonists. A chain drive transmits the intermittent drive movement finally from the lower end of the rocker to the upper end of the rocker, onto the drive shaft which is coaxial to the rocker pivoting axis and is intended for the driving-chain wheel of the envelope-gripper chain. Such a process makes it possible to avoid parasitic GaN deposition on the walls of the reactor.