1. Field of the Invention
The present invention relates to elevator hatchway door interlocking mechanisms, and particularly to an improved elevator hatchway door interlocking mechanism for use in conjunction with small elevator installations having hinged rather than sliding hatchway doors and which makes accidental or deliberate circumvention of the interlocking mechanism remote.
2. Description of the Prior Art
Elevator hatchway door interlocking mechanisms are known in the art. For example, U.S. Pat. No. 1,835,544 describes an elevator door having a dual latching mechanism with a plurality of electrical contacts which must complete an electrical circuit before the elevator car can move from the hatchway landing. U.S. Pat. No. 2,307,542 discloses another interlocking mechanism which uses a permanent magnet to pull a latching member into a recess in the elevator hatchway door. U.S. Pat. Nos. 2,611,840, 1,979,022, 2,280,805 and 2,918,988 disclose other hatchway door interlocking mechanisms. All of these interlocking mechanisms have various disadvantages. Some are more complex than they need to be to accomplish their function, i.e., the prevention of elevator car movement when it is not safe for such movement. For example, the mechanisms described in U.S. Pat. Nos. 2,307,542, 1,979,022 and 2,611,840 suffer from this disadvantage. Another drawback to many of the prior art interlocks is the rather simple way in which they can be deliberately circumvented. For example, U.S. Pat. No. 1,835,544 shows electrical contacts directly behind openings in the interlock housing for receiving corresponding contacts and latches which are not protected against deliberate short circuiting, as for example, by the insertion of a metal object into the opening.