A clutch assembly for a surface treatment appliance includes an input clutch member, an output clutch member driven by the input clutch member, a motorized mechanism for effecting relative movement between the input clutch member and the output clutch member from an engaged position, in which torque is transmitted by the output clutch member to an output, to a disengaged position, in which torque is not transmitted to the output, and a control system for actuating the motorized mechanism.