Spring-loaded brake

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A spring-loaded brake is a braking unit used in trucks , buses and rail vehicles .

The brake pads are pressed purely mechanically against the brake disc or brake drum by means of spring force . In order to release the brake, a force must therefore be applied, which is usually achieved using compressed air ( pneumatic cylinder ) or hydraulic pumps .

Spring-loaded brakes work according to the “ fail-safe ” principle, i.e. H. if the actuating medium fails (e.g. if there is a leak in the compressed air system), the brake still works - it can therefore be used as an emergency brake and parking brake .

The spring-loaded brakes are used as parking brakes in many heavy vehicles . In some trucks from German manufacturers ( Daimler / MAN ) the spring-loaded brake can be graduated and is also used as an auxiliary brake. However, it is never used as a service brake in motor vehicles.

It also occurs as a parking brake (instead of hand brakes ) on rail vehicles . The abbreviation there is often FspBr or FspB. Spring-loaded brakes are often used as stopping brakes, especially on trams and light rail vehicles, which only use dynamic brakes for braking. The spring-loaded brake is prescribed for tram vehicles according to BOStrab.

In order to be able to release the brake in the event of failure of the actuation system (e.g. to tow a truck), an emergency release device is provided for spring-loaded brakes. A connection to the braking system of the towing vehicle is often sufficient. In rail vehicles, this can be a manually operated hydraulic pump; in trucks, individual manually operated threaded spindles are common, with which the springs can be tensioned if this should no longer be possible with compressed air.

Individual evidence

  1. Section 36 (5) BOStrab