If elevators could sweat, most of it would drip from the doors. The doors are definitely the hardest working part of the elevator. Each and every time the elevator stops at a floor, a car door and hatch door need to open and close efficiently without complaint. This hard working part of the average elevator opens and closes 200,000 times per year according to a major door manufacturer.
That produces a lot of wear and tear on the equipment that opens and closes the doors, especially if it is not properly maintained. As a result, elevator doors are the cause of over 70% of all service calls.
So here are the basics of elevator doors, the hardest working element of the vertical transport system.
Types of Doors
There are several different kinds of doors. They are usually described by the number of panels the door has, and range from single panel to four panel. The panels recess to the side when open, so the car must be at least twice as wide as the door to allow the full recess. If more door width is needed than the car provides, then multiple partial-width panels are used. They telescope together when open, so a 48″ 2-panel door only needs a 24″ recess.
When there are multiple panels, each moves at a different rate so they are called single speed, two speed and so on. The panel furthest from the edge where the door closes (otherwise know as strike side) moves the slowest. The leading panel moves faster to “catch up” when opening, so that all panels hit the fully recessed position at the same time.
Doors can open to one side (called side slide doors) or from the center (center parting doors). Both side slide and center parting doors can have multiple panels.
While there is a single door on the car that travels with it, every stop has a door called a hoistway or hatch door that keeps people from falling into the hoistway when the car is not there. These hatch doors must open and close at the same time that the car doors do.
How the Doors Operate
Of course there is an electric impulse from the elevator controller (the brain of the elevator) that causes an elevator door to open and close when the car is safely at the proper floor; however, most action in the door’s operation is mechanical.
The car top houses a machine called the door operator. When the car and hatch doors are lined up, a clutch on the back side of the car door slides down (or up) over pickup rollers on the back side of the hatch doors. The operator then drives the car door open, engaging the pickup rollers and taking the hatch door with it. To close, the operator drives the car door closed, pulling the hatch door along.
When the equipment is adjusted correctly, this is a smooth, unnoticeable process. When there are problems, it is very noticeable. The problems can be evidenced by doors not opening all the way (or at all).
An adjustment of the clutch and/or pickup rollers, to make sure they’re aligned, as well as the linkages that connect the moving parts, can correct this. These parts do not typically get out of alignment by normal use. Rather, misalignment is usually caused by someone forcing the door open or otherwise hitting or vandalizing it.
The hatch door has nylon or rubber wheels that run along an overhead track. If these are worn, the opening and closing of the door can be squeaky or grinding or bumpy.
The bottom of the door has gibs, which run along the grooves in the door sill. When there are obstructions in the sill, this can prevent the door from opening or closing. If a gib breaks, it can cause the door to be misaligned and bind when opening.
Let’s look more closely at the door operator itself. When told by the elevator controller to swing into action, it an electric motor spins a wheel connected to arms that are attached to the door. The arms move the car door along its track to the open position, taking the hatch door with it. The operator controls the speed with which doors open and close, and can be adjusted by a technician.
The belts or chains that drive the door operator do get worn from all their exertion and need to be changed every few years.
Because there is the potential for a breakdown of all of these moving parts, the door equipment needs to have regular inspection and maintenance. The tracks and sills should be cleaned, rollers and gibs inspected for wear, and linkages checked for alignment.
There are dozens of moving parts so to keep this hard working part of your elevator in top condition. Don’t let a problem with opening and closing doors fester. If you are having trouble with an elevator door call a technician. It is a matter of safety. Most problems can be fixed with some simple adjustments.
If consistent routine maintenance is completed by a certified technician, your elevator will keep giving you great service for a long time, without even breaking a sweat.