Certified fail-safe brake – spring-applied brake as holding brake and service brake

The modular system for BFK458, BFK458-L spring-operated brakes

The BFK458 spring-applied brake is a standard product for universal use. Due to its modularity, this brake is used in a wide range of industry sectors with special requirements.

The Long Life version of this spring-operated brake guarantees excellent durability with particularly low life-cycle costs. The spring-applied brake can be used in systems as a holding brake, a service brake, and for emergency stops from high speeds.

Electromagnetically released spring-applied brake are used in all instances where a mass in motion needs to be decelerated in the shortest time possible, or where masses need to be held in place in a defined manner. The braking force is applied by compression springs. Hence, the braking torque generated via a friction fit is also available in a deenergised state in the event of a mains failure. The release of the spring-applied brake takes place electromagnetically.

Functional description

This brake is an electrically released spring-applied brake with a rotary brake disk that is outfitted with friction linings on both sides, the rotor. In a deenergised state, it is tensioned between the armature plate and a counter friction face by a braking normal force applied by compression springs. Hence, its function corresponds to the fail-safe principle. The braking torque is also generated in the event of a power failure or cable breakage. Hence, the spring-operated brake is used as a fail-safe brake. The braking torque applied to the rotor is transmitted to the drive shaft via an axially toothed hub.

The asbestos-free friction linings ensure a reliable braking torque and low wear. In addition to a high-performance standard friction lining, special friction linings are also available for the various application areas, e.g. with a high resistance to wear or increased friction factor.

In order to release the brake, the armature plate is lifted off the rotor electromagnetically (release). The rotor, which is axially displaceable and thereby relieved of the spring pressure, can turn freely.

Application area / utilisation

Via the combination of basic modules with specific units, a very high degree of flexibility is achieved for a wide field of application.

  • Brake motors
  • Conveyors
  • Machine tools
  • Crane construction
  • Wood working machines
  • Automation technology
  • Mechanical engineering

Product features

  • Powerful full range for BFK458 spring-applied brake
  • In 9 sizes, Long Life version in 4 sizes
  • Standard voltages [V DC] 24, 96, 103, 170, 180, 190, 205
  • Stepped torque from 1.5 - 600 Nm, Long Life version 1.5 to 31 Nm
  • Short delivery times with a wide range of different models thanks to tailored logistics
  • Versatile: Modular design for almost all fields of use
  • Torque transmission: Friction-fit during dry running
  • Quick and easy installation: Air gap is preset, the characteristic torques are achieved after just a few actuations thanks to the special processing of the friction surfaces. Locating bearing not required on brake side
  • Durable: The insulation system according to temperature class F (+155 °C) ensures a long service life for the winding. The brakes are designed for a 100% operating time (brake is energised)
  • Low-maintenance: Long, low-wear rotor/hub guide with tried-and-tested involute teeth

Special features

The spring-applied brake is certified for functional safety. The springs used in the BFK458 series which serve to generate the braking torque, are recognised in accordance with the standard DIN EN ISO 13849-2 Table A.2 as a tried-and-tested component. The classification of the safety function takes place based on the Performance Level PL (DIN EN ISO 13849:2015) as well as the Safety Integrity Level SIL (EN 61508).

The main components of the modular system consist of the two basic modules E and N. These modules are available in various torque levels. It is only in module E that the spring pressure, and hence the braking torque, can be reduced and/or adjusted by unscrewing the centrally aligned torque adjustment ring.

The long life version is configurable for the sizes 06 to 12 in combination with the specified characteristic torques in the modular system.