In elevators and lifts, a failed-safe brake is a critical safety component that ensures the elevator comes to a stop if there is a loss of power or any other emergency situation. This brake prevents the elevator from free-falling and provides an additional layer of protection for passengers and property. Here's how the failed-safe brake in elevators and lifts typically works :

1. Primary Braking System : Elevators and lifts are equipped with a primary braking system that holds the elevator car in place when it is stationary. This system uses an electric motor to drive the elevator and a mechanical brake that engages when the elevator stops moving.
    
2. Failed-Safe Brake : In addition to the primary braking system, elevators are equipped with a secondary failed-safe brake, also known as an emergency brake or safety brake. This brake is designed to engage automatically in the event of a power failure or other emergency situation. It ensures that the elevator car comes to a controlled stop and prevents it from descending rapidly.
    
3. Activation Mechanism : The failed-safe brake is usually spring-loaded. When the elevator is operating normally, the brake is disengaged, allowing the elevator car to move freely. However, if there is a power loss or an emergency, the springs in the brake are released, causing the brake shoes to engage the guide rails or a specialized braking surface along the elevator shaft.
    
4. Braking Force : Once engaged, the failed-safe brake generates a significant amount of friction against the guide rails or braking surface. This friction generates the necessary braking force to bring the elevator car to a stop relatively quickly and smoothly.
    
5. Passenger Safety : The activation of the failed-safe brake prevents the elevator car from falling in the event of power loss, cable failure, or other emergencies. This safety feature protects passengers, prevents damage to the elevator equipment, and ensures that the elevator remains safely stationary until proper maintenance or intervention can take place.

It's important to note that modern elevator systems are equipped with multiple safety features, including redundant braking systems, overspeed governors, and emergency communication systems. These features work together to ensure the safety of passengers and property even in the event of various failures.

The specific design and operation of failed-safe brakes in elevators and lifts may vary depending on the manufacturer and the type of elevator system being used. Regular maintenance and testing of all safety components, including the failed-safe brake, are crucial to ensure that elevators operate reliably and safely.

DC disc brakes are commonly used as a safety component in elevator systems with gearless traction machines. Gearless traction machines are often employed in modern elevator systems, particularly those designed for high-rise buildings or heavy-duty applications. These machines use a powerful electric motor directly coupled to the elevator's hoisting sheave (pulley) to move the elevator car. Here's how DC disc brakes are typically integrated into elevator systems with gearless traction machines :

Function and Purpose: DC disc brakes serve as a fail-safe mechanism to ensure the safety of passengers and property in the event of power loss, emergency stop, or other abnormal operating conditions. These brakes are designed to stop and hold the elevator car and counterweight securely in place, preventing unintended movement.

Components and Operation :

1. Brake Disc : The brake disc is attached to the drive shaft or sheave of the gearless traction machine. It rotates with the shaft during normal operation.
    
2. Brake Caliper : The brake caliper holds one or more brake pads in close proximity to the brake disc. The caliper is designed to exert pressure on the disc, generating friction and thereby stopping its rotation.
    
3. Activation : When the elevator system detects an emergency situation, such as power loss or a sudden stop command, the DC brake's electromagnet is energized, releasing the brake caliper and allowing the brake pads to make contact with the disc. This generates the necessary friction to bring the elevator car to a safe stop.
    
4. Engagement : The friction between the brake pads and the disc creates enough resistance to stop the rotation of the gearless traction machine's drive sheave. This action halts the movement of the elevator car and counterweight.
    
5. Safety and Reliability : DC disc brakes are designed to hold the elevator car securely in place even if power is lost or other emergency conditions occur. The brake remains engaged until power is restored and a controlled release is initiated.
    
6. Release : Once the emergency condition is resolved and normal operation is resumed, the electromagnet is de-energized, releasing the brake caliper from the disc. This allows the elevator to operate normally.

Advantages :

1. Quick Response : DC disc brakes provide rapid and reliable stopping capabilities, helping prevent accidents in emergency situations.
    
2. Fail-Safe Operation : The brake system's default state is engaged, which ensures that the elevator stops automatically if power is lost or an emergency occurs.
    
3. Durability : Disc brakes are designed for heavy-duty applications and can withstand frequent start-stop cycles.

Maintenance and Safety : Regular maintenance and inspection of the DC disc brake system are essential to ensure its proper operation. Elevator technicians perform routine checks to ensure that the brakes are functioning as intended, and any worn or damaged components are replaced promptly.

Overall, DC disc brakes are a crucial safety component in modern elevator systems with gearless traction machines, providing an important layer of protection for passengers and property.