Chuck jaw support coupling mechanism - has grooved inner rod thrusting rollers in outer rod into pockets

The mechanism connects the jaw supports of a chuck to the hollow actuating rod passing through a lathe spindle to the piston of clamping cylinder, the latter being connected to the spindle. The rear side of the support has a central opening to match the OD of the rod, and in which are pockets open radially inwards and forming part of an expanding coupling. The coupling has rollers movable in a ring of apertures in the rod, and of larger dia, than the wall thickness of the latter. An inner actuating rod has an external peripheral groove, by means of which the rollers can be thrust outwards so as to engage in the pockets. The inner and outer rods are coupled to independent pistons in the clamping cylinder.