25/10/2016
Since the invention of the elevator, there has been continual improvement in operation and safety, and elevator doors are no exception. Over the years, there have been significant advances in how doors function to ensure passenger safety and convenience.
Before we go into any details about the hardest working part of the elevator, let’s start with rule #1: Never try to force open an elevator door to enter or exit a stuck car! That job should be reserved for elevator technicians and emergency personnel only when necessary. They will use a key to open the door and operate the elevator safely. Forcing and prying the door will damage the elevator unnecessarily and could injure people in or outside the elevator. Also, if the cab begins moving while someone is half in or half out of the car, the results could be devastating.
Keep in mind that elevators are extremely safe, but common sense and precautions need to be followed to keep them that way. As a matter of fact, many do not know that statistically, elevators are the safest mode of transportation around. In the United States, elevators make approximately 18 billion passenger trips per year. Those trips result in approximately 27 deaths annually, according to estimates from the U.S. Bureau of Labor Statistics and the Consumer Product Safety Commission. That works out to a fatality rate of 0.00000015% per trip, or the safest mode of transportation available.
Occasionally, there are accidents. You may have heard the tragic (but true) tale of the man that was decapitated because the elevator door closed on him and then continued to the next floor. Fortunately, these kinds of accidents are extremely rare because elevators have multiple safeguards that keep people in the safest place; inside the elevator car. The doors are designed with passenger safety in mind.
Some of these safeguards include mechanisms that ensure the car door only opens when they are supposed to, which is when the car is safely at a floor. If the car door opens in between floors, there is space between that door and the shaft wall that would allow someone to fall out and down the shaft, causing injury and potentially death.
The first safeguard is that automatic opening will only happen when the car door clutch and the hatch door pickup rollers align, which is when the car is at a landing.
The second safeguard prevents manual opening between floors, as a passenger might be tempted to do if the elevator stops mid-ride. Door restrictors prevent the car door from being forced open when not aligned with a hatch door.
There are two types of restrictors: mechanical and electro-mechanical. The mechanical version physically holds the door closed until it is at a landing. Think of a pin in the door track that blocks the car door from moving, but is released by a cam on the hatch door track when they mate. This pin could also be pulled manually by an elevator technician from the car top. This way of opening the elevator door would be much simpler and less destructive than beating on the door with an ax until the door restrictor bends and lets the door scrape by.
An electro-mechanical restrictor works without physical interaction between hoistway and car doors. This is an electronic eye on the car above the door that interrupts the door operator circuit, preventing opening, until it “sees” a matching eye above a hoistway door, and allows the circuit to complete.
Another safeguard prevents premature closure on arms and legs. The initial solution for an elevator car closing on limbs was a bumper edge that sensed when it came into contact with something solid and automatically reopened the door. As improvements were made, electronic eyes came along, working similar to those on garage doors. Mounted at approximately waist-height, when something crosses the beam of light, the doors stay open. Current technology is a curtain of infrared beams that cover over 90% of the elevator opening. As a safety feature, if the beams are obscured for a certain period of time, the doors will close slowly in case of fire and smoke. However, if they are obstructed by an object, the doors will open.
Door safety can be improved by having a technician make adjustments to the opening and closing rate (and no, pushing the “door close” button repeatedly will not change this setting). Wait time can be shortened or lengthened, depending on your needs. Speed of opening and closing is also adjustable. So if your door operation seems to be faster or slower than it should be, or if the force seems too heavy, let your elevator technician know. They can adjust things so they run smoothly, safely and efficiently.
If you treat your doors well, giving them proper maintenance and adjustments, they will return the favor by protecting you. So leave the ax at home and trust that your doors will let you in and out only when it’s safe to do so.
