Elevator parachute system

2024 July 23

Read time : 13 m

Parachute or Safety Brake

The safety brake, or parachute, is one of the most vital components of an elevator, used to stop the cabin or counterweight. These brakes are designed and installed in two types: one-way and two-way. A one-way parachute only operates in case of the elevator falling, while a two-way type can stop the elevator both when it is ascending and descending. If the emergency brake is of the one-way type, the direction of rotation that causes the parachute to operate must be marked on the governor in the machine room.

The elevator emergency brake is a component that is placed below or on the elevator cabin yoke on both sides and can stop the cabin on the rails with the help of its two jaws. Parachutes are most commonly used when the elevator, for any reason, exceeds the permissible speed or when the wire rope breaks and the elevator falls. The movement of the elevator cabin is done by the wire rope or chains hanging upwards and downwards. In case of power failure or elevator fall, the emergency brake or parachute system is used to stop the elevator. When the cabin speed exceeds one meter per second, the parachute system activates and stops the cabin.

This parachute is activated by the governor or speed control system when the elevator speed exceeds the allowable limit. The emergency brake receives the stop command from the governor and activates, resulting in locking onto the guide rails of the cabin or counterweight and stopping the elevator movement. In general, the task of the parachute is to stop the elevator cabin in dangerous situations and prevent potential harm to passengers.

Components of the Parachute

Contrary to its small appearance, this elevator componenta

The emergency brake system or parachute in an elevator is composed of various parts that can effectively operate to stop the elevator. On the main body of the parachute, locking components and friction jaws are installed. The brake operation is carried out by the locking components, and the friction jaws directly engage with the rail. The emergency brake is responsible for connecting the two safety brakes. Other components of the parachute are as follows:

Safety contacts
Governor wire rope
Command lever
Holding springs

These components work together to provide a safe and reliable performance for the elevator emergency brake system.

has many applications. Guide shoes are used in all elevators, including hydraulic, traction, and magnetic ones. As mentioned, the main role of guide shoes is to assist in the smooth movement and reduce the slippage of the elevator cabin and the counterweight along the elevator guide rails. All this contributes to the improved movement of the elevator.

How the Safety Brake or Parachute Works

The safety brake, or parachute, in elevators, operates simply and effectively, activating in the event of a potential elevator fall. The mechanism works as follows: when the elevator speed exceeds the standard limit, the wire rope connected to the governor stops. Following the stop of the wire rope, the lever connected to the safety brake activates. Consequently, at high speeds, the parachute jaws create friction with the rails, causing the cabin to stop. This process effectively prevents the elevator from falling and ensures passenger safety.

Types of Safety Brakes or Parachutes

With the advancement of technology and the production of high-speed elevators, the need for appropriate parachutes or emergency brakes for each type of elevator has become more pronounced. In the elevator industry, emergency brakes with different functionalities have been designed, and categorized into three types: instant-action parachutes, instant-action with shock absorber effect, and gradual-action parachutes.

Instant-Action Parachute: This type of parachute comes in two forms: toothed and roller. The operation of this brake is such that the jaws directly and quickly strike the rails, and the impact is felt immediately in the cabin. This parachute can be used at speeds up to 0.6 meters per second and is also applicable in hydraulic elevators.

Instant Action with Shock Absorber Effect: In this type of parachute, the braking force on the cabin and counterweight frame is very intense. Therefore, this brake system uses shock absorbers to mitigate a significant portion of the impact. Using this parachute results in less force being exerted on passengers and the elevator cabin. This type of parachute can be used at speeds up to 1 meter per second.

Gradual-Action Parachute: In this type of parachute, the jaws gently engage with the rails. The elevator speed is gradually reduced, and the impact force on the cabin, counterweight, and passengers is minimized. Stopping elevators equipped with this type of parachute take more time and exert less force on the jaws. This type of parachute can be used at any speed.

Counterweight Frame Parachute: Using an emergency brake for the counterweight frame is generally not necessary; however, if there is a passageway below the counterweight frame, the law requires an emergency brake for the counterweight. For example, in buildings with a ground floor where the elevator starts from the first floor and there is the possibility of people moving underneath the counterweight, an emergency brake must be used. To ensure that the cabin parachute activates first, the counterweight parachute should have a governor nominal speed that is 10% higher than the cabin governor. Otherwise, the initial activation of the emergency brake on the counterweight would exert a sudden and substantial force on the cabin.

Important Considerations for Elevator Parachutes

Capacity: The term “P+Q” is marked on parachutes, indicating the weight of the cabin plus the number of passengers (with each passenger considered to weigh 75 kg). In Iranian parachutes, a specific range is written, and the capacity should be between these numbers, while in foreign parachutes, a fixed number is marked, and the capacity can be 7% more or less than this number.
Speed: The cabin speed must match the parachute speed to ensure proper and safe operation.
Rail Blade: The rail engagement blade must match the rail to ensure proper parachute performance. This alignment is crucial so that when the parachute activates, it makes appropriate contact with the rail, ensuring the elevator stops correctly.