Method and apparatus for controlling elevator cars in a common sling

A method for controlling an elevator, the elevator having at least two cars arranged in a common car sling which travels in an elevator hoistway in a building having a plurality of floors and is driven by a hoisting machine via a suspension rope, comprising the steps of:

• a. determining and storing in memory a distance (SD) value for a distance between each pair of adjacent floors served by two cars arranged in a common car sling travelling in an elevator hoistway in a multi-floor building;
• b. determining and storing in memory a mean deck-distance (MDD) value representing a mean of the largest and smallest distance (SD) values determined in said step a.;
• c. determining and storing in memory a floor difference (DMDD) value representing a difference between the mean deck-distance (MDD) value and the distance (SD) value corresponding to each pair of the adjacent floors;
• d. selecting one of the pairs of adjacent floors at which to stop the cars;
• e. determining a car difference (IDMDD) value representing a difference between the value of the actual deck-distance between the cars and the mean deck-distance (MDD) value;
• f. determining a movement distance (SDSS) value representing the difference between the floor difference (DMDD) value corresponding to the selected adjacent floors and the car difference (IDMDD) value;
• g. moving the cars the movement distance (SDSS) value relative to one another;
• and
• h. stopping the cars at a predetermined position relative to the selected adjacent floors.

An apparatus for controlling an elevator having at least two cars in a common car sling which travels in an elevator hoistway in a multi-floor building comprising:

• a deck-distance drive machine attached to a common car sling supporting at least two elevator cars for travel in a hoistway, at least one of the cars being movable relative to the car sling, said deck-distance machine being coupled to the at least one car;
• and a control connected to said deck-distance drive machine for receiving a signal representing a selected pair of adjacent floors at which the cars are to be stopped whereby when said deck-distance drive machine is attached to the car sling and coupled to the at least one car, said deck-distance drive machine responds to said control to selectively adjust the distance between the cars to correspond to a distance between the selected pair of adjacent floors to be served by the cars;
• said control including a memory containing calculated floor difference (DMDD) values relative to a mean deck-distance (MDD) value of floor-to-floor distance (SD) values of all pairs of adjacent floors and said control comparing the one of said calculated floor difference (DMDD) values corresponding to the selected pair of adjacent floors with an actual car distance (IDMDD) value representing a difference between a value of the actual distance between the cars and said mean deck-difference (MDD value to control said deck-distance drive machine.