How Elevators Work

Push Vs Pull

  • Pull = Traction
  • Push = Hydraulic

The first elevator started out as platform / cubicle attached to a lifting system. A rope attached to the platform & wound around a drum, gave you the first elevator.

Of course, modern passenger and freight elevators are a lot more elaborate than this. They need advanced mechanical systems to handle the substantial weights and speeds. They need sophisticated, redundant control mechanisms to operate the elevators, safely & smoothly.

There are two major elevator designs in use today:

  • Traction roped elevators.
  • hydraulic elevators and

Traction System

The most popular & efficient elevator design is the roped elevator. In roped elevators, the car is raised and lowered by traction steel ropes.

The ropes are attached to the elevator car, and looped around a sheave. A sheave is just a pulley with grooves around the circumference. The sheave grips the hoist ropes, so when you rotate the sheave, the ropes move too.

The sheave is connected to an electric motor through a gear box. When the motor turns one way, the sheave raises the elevator; when the motor turns the other way, the sheave lowers the elevator. In gearless elevators, the motor is directly connected to the sheave and movement is controlled very precisely by movements of the motor. Typically, the sheave, the motor and the control system are all housed in a machine room above the elevator shaft.

The ropes that lift the car are also connected to a counterweight, which hangs on the other side of the sheave. The counterweight weighs about the same as the car filled to 40-percent capacity. In other words, when the car is 40 percent full (an average amount), the counterweight and the car are perfectly balanced.

The purpose of this balance is to conserve energy. With equal loads on each side of the sheave, it only takes a little bit of force to tip the balance one way or the other. Basically, the motor only has to overcome friction -- the weight on the other side does most of the work. To put it another way, the balance maintains a near constant potential energy level in the system as a whole. Using up the potential energy in the elevator car (letting it descend to the ground) builds up the potential energy in the weight (the weight rises to the top of the shaft). The same thing happens in reverse when the elevator goes up. The system is just like a see-saw that has an equally heavy kid on each end.

Both the elevator car and the counterweight ride on guide rails along the sides of the elevator shaft. The rails keep the car and counterweight from swaying back and forth, and they also work with the safety system to stop the car in an emergency.

Roped elevators are much more versatile than hydraulic elevators, as well as more efficient.

Hydraulic Elevators

Hydraulic elevator systems lift a car using a hydraulic piston mounted inside a cylinder and driven by pressurized oil through a pump and valve system.

The cylinder is connected to a fluid-pumping system. The hydraulic system has three parts:

  • A tank (the fluid reservoir)
  • A pump, powered by an electric motor
  • A valve between the cylinder and the reservoir The pump forces fluid from the tank into a pipe leading to the cylinder. When the valve is opened, the pressurized fluid will take the path of least resistance and return to the fluid reservoir. But when the valve is closed, the pressurized fluid has nowhere to go except into the cylinder. As the fluid collects in the cylinder, it pushes the piston up, lifting the elevator car.

    When the car approaches the correct floor, the control system sends a signal to the electric motor to gradually shut off the pump. With the pump off, there is no more fluid flowing into the cylinder, but the fluid that is already in the cylinder cannot escape (it can't flow backward through the pump, and the valve is still closed). The piston rests on the fluid, and the car stays where it is.

    To lower the car, the elevator control system sends a signal to the valve. The valve is operated electrically by a basic solenoid switch. When the solenoid opens the valve, the fluid that has collected in the cylinder can flow out into the fluid reservoir. The weight of the car and the cargo pushes down on the piston, which drives the fluid into the reservoir. The car gradually descends. To stop the car at a lower floor, the control system closes the valve again.

    Thus the system only uses power through the motor for upward movement and gravitational force for downward movement.

ABOUT US

EROS ELEVATORS, the pioneer of the Indian Elevator Industry was established in 1947, head quartered in Mumbai and with branches in Pune, Bangalore, Ahmedabad, Surat, Rajkot, Nashik, Vapi, Daman & Hyderabad.

HEAD OFFICE

Eros Group of Companies,
405, Bharat Industrial Estate, T.J. Road,
Sewree (W) Mumbai – 400015, India.

9:30 am to 6:00 pm

CONTACT DETAILS

Phone: +91 22 2413 2425 / 2414 3431
Maintenance Toll Free Number: 1800 833 0230
Email: info@eroselevators.com
Fax: +91 22 2415 3192
Contact