Car door safety interlock

In an automatic operating mechanism for a power operated sliding door of an elevator car which travels in a hatchway that has a sliding hatch door at each landing, there being interengaging means on the car door and on each hatch door so that opening and closing of the car door at a landing also opens and closes the hatch door at said landing, a mechanical safety interlock to permit the elevator car door to be moved more than a critical distance from its closed position only when the elevator car is in a landing zone, said safety interlock comprising, in combination:

• a fixed interlock lug on the car frame above the car door;
• an interlock hook pivotally mounted on the car door, said hook having a normal position when the car door is closed in which a lug engaging portion thereof is aligned with said lug and spaced from the lug by said critical distance;
• a movable element on the car door which operatively engages the interlock hook so that movement of said element moves said hook from said normal position to a clearance position in which its lug engaging portion is out of alignment with the interlock lug;
• and element driving means mounted on the car door in a position to contact the interengaging means on a hatch door when the car door has moved part of said critical distance, said element driving means being thereafter moved by said contact with said interengaging means to move said element and thereby move the hook to its clearance position before the car door moves the rest of the critical distance, whereby the car door can be moved more than said critical distance only when the car is in a landing zone.