Abstract: An elevator car has a drive mechanism mounted in a compact housing on the upper surface of the car. The drive mechanism includes a rotatable drive shaft, around which is mounted a linear actuator block having a plurality of ball bearings, obliquely arranged relative to the shaft, and firmly touching the shaft. Rotation of the shaft by a motor makes the block move linearly along the shaft. A bracket attached to the block carries an elevator door. Rotation of the shaft therefore opens and closes the door. The direction of movement of the block, and hence the door, depends on the direction of rotation of the shaft. The drive mechanism is compact and simple, and can be applied to new elevators or can be used to retrofit existing elevator cars.