Abstract: Driving member of the mixing centers are driven permanently by a transmission element for driving a coupling member with which a complementary coupling member of a stirring pot is brought in engagement. Each driving member comprises a pulley connected to the driving shaft of a coupling member by a resilient means associated with protrusions interposed between the shaft and the pulley, said protrusions disconnecting the shaft from the pulley when there is a unacceptable excess of a retaining torque applied to the coupling member.