In elevators provided with automatic doors, the coupling between the car door and the landing door is generally effected using a door coupler which is mounted on the car door and engages counterparts mounted on the landing door by means of its gripping elements. The door coupler and the counterparts are so fitted relative to each other that, when the elevator car is moving past the landing door, the counterparts on the landing door are passed between the gripping elements of the door coupler. When the car is at a landing and the car doors are moving, the door coupler is in engagement with the counterparts. In this way, the landing door also moves when the car door is moved by a power means connected to the car door. Often the gripping elements are metal vanes projecting from the door coupler towards the landing door and forming a kind of a vertical slot which is open towards the landing door. The counterparts used often consist of rollers mounted on the landing door and projecting from the door towards the elevator shaft, the axle of the rollers being mounted in a position perpendicular to the plane of the door. The dual function of the door coupler in the closing of the door sometimes involves problems. In its dual function, the door coupler should move the landing door reliably to the end of its closing movement and, on the other hand, it should release the landing door before the elevator car starts moving. The requirement that these two functions be properly performed easily leads to complicated and expensive solutions, which may additionally involve limitations regarding the accomplishment of the transportation function of the entire elevator system, especially the transport capacity.
Regarding the closing of automatic elevator doors, adequate closing of the landing doors is a question that deserves special attention. For example, the air currents generated in the elevator shaft may be a hindrance to proper closing of the landing door. In practice, to ensure that the door is properly closed, it is possible to use e.g. a so-called closing weight which draws the door by means of a rope into the closed position, or even a separate motor or other gear acting on the landing door. Such solutions may be noisy, take up space and involve expenses and additional maintenance. Using such solutions also easily leads to longer door closing times, which has a direct negative effect on the transport capacity of the elevator.