The device has a lower arm (34) and an upper arm movable in rotation along axes (A, B) with respect to a chassis and the lower arm, respectively. A mechanical control unit (56) has a main drive device (58) that drives a heddle-marker (42) along an axis (C1). The main drive device has a drive pinion (60) that is movable with respect to the upper arm and is connected to the heddle-marker. A toothed bar (62) engages with the pinion and is fixed to a rod (64) of a cylinder (66). The bar is maintained on the pinion by a slide connection (63) i.e. U-shaped pad, connecting the bar with the upper arm.
