Shoe brake
The shoe brake is a mechanical brake in which a rotating cylinder (brake drum) is braked from the outside by pressed brake shoes.
Usually two opposing brake pads are pressed on. This design has the advantage that the shaft on which the brake drum is attached is not stressed by any bending moments. Due to the jaw guidance, there are basically three types of construction:
- The shoe brake with shoes that are rigidly attached to the brake levers is only used with low braking forces and for reasons of cost. The reason for this is that the brake shoes do not touch the entire surface of the drum, which means that even braking is not possible. The brake shoes can even tilt.
- The shoe brake with the shoes rotatably mounted on the brake levers has the advantage that the brake shoes adapt to the drum, which prevents tilting. This design is used most often.
- The best, but also the most expensive version is the shoe brake with radially guided shoes. The jaws are guided by two guides each radially over the brake lever or individually to the brake drum. This design achieves the best braking performance, but is rarely used due to the high construction costs.
The brake can be actuated pneumatically, hydraulically, electrically, mechanically or electromagnetically. In vehicle construction with compressed air actuation, it is only used as a block brake on rail vehicles . The main area of application of the shoe brake is in crane and hoist construction as a service and parking brake. Here, for safety reasons, the brake is always closed in the idle state and in the currentless state; only during operation are the brake shoes "released", ie raised, by so-called brake release devices . In order to achieve a permanent braking effect even if the energy supply fails, the actuation (the closing of the brake) is always carried out by a pretensioned compression spring, since in the event of a break (in contrast to the tension spring ) this only loses the force of an incline in the spring coil and therefore continues the braking effect applies, albeit to a lesser extent.