On 15 Dec 2004 20:31:29 GMT Andrew Gabriel wrote: | In article , | email@example.com writes: |> On Wed, 15 Dec 2004 14:55:12 +0100 T.S. wrote: |> |>| I have an off-topic question: do landing doors in US elevators have |>| interlocks? |>| |>| According to the European lift standard EN 81 all landing doors have to be |>| equipped with interlocks so that the doors could not be easily open when for |>| example there is no car behind them. You need a special tool to open them in |>| emergency. An interlock also has a contact to be put in a safety circuit. |> |> I don't know about the rules, but every elevator I've been in has them. |> |> The inside car gate, however, did not have any interlock on all the |> elevators I saw when I was in college. It was a common school prank |> to open them while the elevator was moving. And of course when that |> happens the elevator stops at the next landing. But the interlock | | Same here in the UK, except forcing the internal doors normally | results in instant halt of the car, whereever it is, and without | any of the normal gradual breaking. Pushing the door closed again | used to result in resumption of service after a delay in the ones | I was familiar with.
Yes, forcing the gate (the term used for the inside door, at least in the USA) open would stop the elevators. But the stop is not instantaneous. It will still travel a couple feet. I know because I have ridden them with the gate wide open and manually (insulated) contacting the gate trip switch to simulate the gate being closed ... and then let it open. The elevator will stop when the pranks were done, too. Sometimes it would stop between floors where the gates could close again and the elevator resumes. That's might well have been most of the cases. But in at least some of the cases, this happened right at a floor, either as it was being passed by, or while it was slowing to a stop.
On the Otis elevators I've seen, there was a blade about 10 inches long on the gate that slid between two rollers on the inside of the door. At a floor landing, it stops between the rollers. As the gate opens, the outer roller is pushed by the blade bar. It swivels up and pulls a wire that releases a spring loaded interlock on the door at the top and bottom.
If it stopped at the floor with the gate already open, then the blade bar is now positioned "outside" of the roller and cannot push it outward to to release the interlock. When the gate attempts to close, it hits the outside of that roller, which prevents the gate from closing all the way. The gate stopped at that position does not close the trip switch, and the control system will not put the elevator in motion. The gate closure then times out and reopens, but to no avail since nothing can get the mechanics back into the correct position without moving the elevator car up or down by at least several inches.