A safety device for locking a plurality of operation levers, the device comprising a frame on which the levers are mounted for pivotal movement with respect thereto, two lock plates mounted side by side on the frame for movement towards and away from one another between locked and unlocked positions of the device in response to rotary movement of a cam disposed therebetween; a respective link pivoted to each of the levers having its free end supported for linear reciprocal movement in response to the pivotal movement of the respective lever, the link having an engaging portion which co-operates with an engaging portion on the respective lock plate on movement of the lock plate towards the locked position to lock the link against the said reciprocal movement.