Elevator Governor
The elevator governor is a crucial safety device used in elevators to control the cabin’s speed. The primary function of the governor is to prevent the cabin from exceeding its permissible speed and to avert sudden falls. This device is designed to activate in case of any fault or technical issue that causes a sudden increase in cabin speed.
The governor uses safety gear on the cabin and a connected cable to monitor and reduce the cabin’s speed. Under normal conditions, the governor’s sheave and elevator cabin speed are equal. If a fault or issue causes a sudden increase in cabin speed, the governor stops the movement before the cabin speed reaches 115% of the rated speed. If the cabin’s speed exceeds the allowed limit, the governor stops the cabin by engaging its jaws or pendulum clamps with specific and fixed gears.
Additionally, the governor prevents the cabin from falling in situations like cable breakage or excessive elevator speed. Overall, the purpose of designing and using the governor in elevators is to ensure passenger safety and prevent accidents.
Components of an Elevator Governor
The structure of the elevator governor (Governor) includes several parts, each with a specific function to ensure the elevator’s safe operation.
- Main sheave or governor: This part includes components like the pendulum arm or anchor under spring tension, allowing it to swing back and forth. The governor has a V-groove designed for the cable to sit on the main sheave, with a smaller V-groove for testing the governor. Fixed and specific gears are also installed on the main sheave.
- Pit sheave: This component is installed at the lowest point of the elevator shaft and is responsible for guiding the cable and maintaining proper tension.
- Contacts and microswitches: These electrical components send the necessary signals to cut off or connect the power supply and stop the elevator’s operation in case of any technical malfunction.
- Six-millimeter diameter cable: These cables are used to transmit force and movement to the elevator cabin and play a critical role in the safety and proper functioning of the elevator.
Types of Elevator Governors
Elevator governors can be categorized into two types based on their movement.
Vertical or Pendulum Governor:
This type of governor has a lever in the middle that oscillates bi-directionally and rotates in sync with the elevator’s speed. When the elevator’s speed increases, this lever oscillates more. This oscillation triggers the drive rod and engages the lower lever with the governor wheel, eventually stopping the governor. In other words, as the elevator’s speed increases, the pendulums gradually move upwards, and when the speed exceeds the limit, the elevator cabin is stopped.
Centrifugal Governor:
The main body of this type of governor consists of a rotating wheel and a horizontal mechanical lever, along with an internal electric sensor. When the elevator’s acceleration suddenly increases, the mechanical lever locks inside the rotating wheel and the mechanical pawl locks onto the rails, stopping the elevator cabin. In this situation, the electric sensor inside the governor activates the safety circuit and stops the motor.
Types of Elevator Governors Based on Engagement Direction
Governors can also be divided into two types based on their speed range: unidirectional and bidirectional.
Unidirectional Governor: This type of governor operates correctly at a specific speed and ensures the elevator’s safety when the cabin’s speed increases downwards.
Bidirectional Governor: A bidirectional governor prevents the cabin from falling when the elevator’s speed increases upwards or downwards. This type of governor is mandatory for gearless motors.
Function and Operation of Elevator Governors
To explain the operation and function of an elevator governor, it must be noted that as the cabin’s speed increases, centrifugal force is generated, pushing the governor’s jaws outward and causing them to engage with the governor’s fixed edge or gears, stopping the governor. In this situation, microswitches issue a command to cut off the motor, preventing it from running. Then, with the activation of the parachute, the elevator cabin stops at any height.
The operation of the microswitch to issue the motor stop command works as follows: when the cable moves freely, the stop levers remain in their initial position due to the springs. When the governor’s main sheave locks, the stop levers are activated by the governor cable, sending a stop command from the elevator control panel to the other safety components. As a result, the elevator motor stops, the parachute is activated, and the elevator cabin is brought to a halt.
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