The fluid valve synchronisation control has a drive input shaft (11) and an output shaft (12) with a valve opening and closing cam. A coupling (31) allows relative movement of the output shaft w.r.t. the input shaft to conform to its position. A sleeve (15) has a helical groove (17) on the input shaft. A base portion (32a,33a) engages in the groove and has a toothed section (32b,33b) to engage in the helical recess of a fixed part formed in the coupling to allow selective connection of the coupling and output shaft.
