Nice videos about elevator operation.

[Riotpack]

I was sick in bed for a week and spent a bit of time on youtube.
I stumbled across some fun videos about elevator operation.





Relay Logic


Info pt1&2

[android]

...and here one about the latest development in elevator technologyhttps://www.youtube.com/watch?v=JofRc_qQCAs#noexternalembed-ws

[Hydrawerk]

Here I made a special elevator video...

[SeanB]

An older one.........

[SeanB]

I did a little bit of work on firmware of lifts once. Specifically the bit that interfaces with the fire alarm and prevents it stopping on floors that are on fire or full of smoke. Once the alarm goes off the lift will only go to the ground floor, or if that is on fire the first floor, or if they are both on fire the first one that isn't.

I found it interesting because they always say you should not use lifts in the event of a fire, but apparently people do.

Think about being in Burg Khalifa on the top floor and having to go down 1km of stairs......

IIRC in the USSR they built high rise buildings where they only put stairs up to a certain level, then after that it was only lifts. Kind of bad in a power failure if there is no alternate power source, and if a fire burns out the power cabling.

[ConKbot]

this shows some of the relay logic, some more modern stuff, and a few things about how the controls work. 

[Richard Crowley]

And of course the classic TV series "The Secret Life of Machines" featured this eipsode about the Lift/Elevator

https://youtu.be/iSLmzjE_woQ

[Leiothrix]

I found it interesting because they always say you should not use lifts in the event of a fire, but apparently people do.

You shouldn't, but some people don't have much of a choice.

I work in a hospital so probably have more in the way of disabled people around me than the average office building does, but you're not getting down stairs in a wheelchair.  Well, not in one piece anyway.

[Red Squirrel]

Wow some really interesting stuff.  It kinda reminds me of old phone switching technology.  Even the current tech is interesting, and it's a rather niche thing to know about.  Not something the average person gets to work on that's for sure.

The spiral switch/sensor mechanism is interesting, I would have figured that there would be sensors at the actual floors with wires going back up, but guess this method cuts down on the amount of wiring needed and gives a central location to make adjustments.

[SeanB]

Wow some really interesting stuff.  It kinda reminds me of old phone switching technology.  Even the current tech is interesting, and it's a rather niche thing to know about.  Not something the average person gets to work on that's for sure.

The spiral switch/sensor mechanism is interesting, I would have figured that there would be sensors at the actual floors with wires going back up, but guess this method cuts down on the amount of wiring needed and gives a central location to make adjustments.

Spiral switch is Schindler, Otis uses a similar one ( but not the same, patents) or a polyamide fibre band running down the shaft with magnets on it, with the lift car having hall sensor detectors that pass close to it. Express used a series of changeover tappet switches at the side of the shaft and a guide on the car that flipped each cam as it passed, with the car stopping on the selected floor.

Most current systems which are new use a magnetic or proximity sensor on the car, with either steel tabs or magnets on the shaft side to actuate them. Your speed controls will use these to time ramp times, or just use a 2,3 or more speed motor to provide the ramps. Almost all use AC motors, always 3 phase, and a lot of the modern ones use an inverter to provide the drive, with it levelling always to the sensor setting. The desire is that the lift always stops absolutely level with the landing, within 2mm is perfect, and to do that from empty to with the testing load ( typically 2 times the plate rating inside the lift, for passenger lifts), and from both approaches for intermediate floors.

Every 6 months the lift will be tested for the electrical overrun protection operation. The mechanical one is only tested at the 5 year certification, as it does do damage to the shaft guide rails, which you have to file afterwards. Monthly will be lubrication, checking of operation, checking of lamps, doors and belts. With this is cleaning of the shaft and lift exterior, I have done a lot of painting in the shaft to add warning yellow and black on moving parts, along with replacing the shaft and car lighting to bring it into compliance with the new regulations as they came into force. Should have done that lift technician trade test I had as a choice.

If you are with Schindler AG and do the SA tour you come to the lift at work, as it is one of the samples of them on the inspection list. going for it's 50'th anniversary in a few years, still mostly all original, with only the main ropes having been changed in 1978, should need new selector and emergency ropes in a few years, they are still original, but still are within wear limits. Lift gearboxes always weep oil, if not then there is no oil, as they have large sleeve bushes on the shaft, no ball races there except on high speed units.

[Riotpack]

Thanks for posting those vids and for providing more info.
I have never really thought about what makes them tick before, so it has been fun learning about the systems and redundancies etc.
By the looks of things, the motor now sits on top of the car and the motor room is obsolete.

[SeanB]

No, the new MRL ( Motor Room Less) units rarely have the very heavy motor on the car. They are put on the side top of the shaft, where they can run the main lifting cable in a half wrap over the windlass drum. the way they do that is to have more than 2 times the length of the shaft as the main rope, and have the rope anchor at the top of the shaft, run the bundle down to the car, wrap around the bottom on 2 sheave sets and then up to the windlass drum, around and down to the counterweight, around the counterweight sheave and then back up to the top of shaft to the anchor and compensator. The car is supported on 2 sides, but the rope now has twice the wear from all those extra turns, and wears faster, but you now have the vibration at a higher frequency which is easier to damp with compression dampers that are intrinsically fail safe.

You do lose overload capacity, the old systems are designed so that any single lift rope can hold the entire fully laden car with double the car load inside, and still run it, but they put typically 4 ropes so that they get fatigue life of decades. MRL is running the rope closer to the fatigue limit. As wll MRL units are always inverter driven, as you cannot fit a switched multipole motor into the same space easily, as you already have a 11 or more pole motor to get the rotation speed down to something the car will handle. Hard to make a gearbox that is pancake thick at that power level.

[SeanB]

Mostly a reaction to user input. Japan wants a fast lift with slight user discomfort from high acceleration and slowdown, and the UK has nervous people who will complain if they feel the lift move.

Doors opening before stop is fine, it is just a timing issue, it will not open till the retiring cam is within the door release envelope, as it is a physical actuator that has to be driven out to contact a roller ended cam to release the door latch, and then a separate door follower in the car door operates the outer door in tandem with the inner door. There are safety switches on both the cam, the door leaves and the inner door, so that the lift motor is electrically inhibited ( not a software interlock, this is a relay contact closure along with both input state monitoring and relay monitoring) from moving the car while any door is open or the inner door is not fully closed. The car door has 3 switches, door open, door closed and door fully closed. The car is inhibited from movement if DFC is open. Door open stops the opening motor, and on closing door closed drops it to slow till the door fully locks, or on older ones it stops it, and inertia and an over centre latch holds the door closed with an electric brake keeping it closed. Power fail and the door will automatically open from a spring, as a safety feature.

[Hydrawerk]

Is there a safety brake that prevents free fall in case of cables failure? I think yes, but is it in all elevators?
http://en.wikipedia.org/wiki/Elevator#Elevator_safety

[SeanB]

There are typically 2 brakes. The main lifting cables have a spring loaded set of metal grips that engage cams that engage the guides if they break and the car drops without the cables. There is a second brake on the safety rope that will trip the supply, typically by shorting all 3 phases together to force a breaker trip or a fuse to blow. that is why your lift breakers have such a high breaking capacity, typically a 15-20kA breaking capacity, even if it only is a 40A breaker. The breaker in the motor room is rated to withstand this for multiple events, as this is tested on certification. This safety rope is also able to trip the main brake set because the governor will cause it to stop moving and this will trigger the main brake on the car via a sturdy lever.

Goods lifts now are also required to conform to almost all the safety regulations of passenger lifts, though they typically do not have in car controls, but still now have to have a trailing cable for connection to the internal door limit switches and have to have an emergency bell and lighting. Before they could be chain lifted with a single chain, but now they have to have a cable set and safety cable with governor.