Assembly of a thruster brake
A thruster brake consists of cast iron shoes that are lined up with friction pads. Each shoe has a pivot fitted in the base and are situated on the main arm side arm of the brake. They are connected with each other by tie rod on the top which is locked in the swivel block in the side arm and pivoted to the main arm by a lock nut. There is a crank liver that is hinged on the main arm, whereas the other end is attached to the top clevis of the thruster with the help of a hinge pin. There is also a brake spring connected to the main arm and a locknut pre-loads it on the lever.
Pre-tension in the brake spring chooses the braking torque and the thruster is attached to the brain by a hinge pin.
Braking pressure is transferred to the shoe from the spring by the help of a simple and stiff lever / rod mechanism. Brake shoes are released which is caused by energizing the three phase thruster that overcomes the spring force. The shoes are then moved clearly off the drum through a lever arm linkage system. The entire operation is well balanced to provide equal shoe clearance.
Nowadays, thruster brakes are widely used as a part of modernizing of trolley, hoist and a bridge. In hoists, a thruster brake uses the internal torque spring that provides an easy application of the brake. The brake has an inherent cushioning effect that makes it perfect for jogging or cycling applications. These applications generally don't suit a clapper style brake as they tend to destroy it.
A thruster brake is also used with AC or DC motors and applies a fixed torque to stop any machinery. Other places where thruster brakes are used include lift bridges, crane travel drives, conveyors and other similar applications. The thruster brakes used here usually have hydraulic pump and an AC square-cage motor.