Brake release device

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Brake release devices are components of safety brakes in conveyor technology and vehicle construction . (The word component "... lüft ..." in this case has nothing to do with air supply, but is derived from the Middle High German lüften = lift up.)

Safety brakes are normally held in the braking position by a spring or weights. The force of this braking device is only overcome by a brake release device and the brake is released during certain processes, for example during a defined lifting or moving process. These brake release devices are available in different versions for different application conditions. In the event of a malfunction (e.g. power failure), the brakes remain closed or are triggered by springs or weights.

A well-known example of this safety brake in the form of a double-shoe brake can be found in railway technology. The required compressive force is generated here by a spring. The mechanics required to release the brake are operated with compressed air.

interpretation

The relevant parameters and therefore the selection criteria of the brake release devices are the release work to be performed (W L ), the release stroke (h L ), the release force (F L ) as well as the switching frequency and the relative duty cycle ED.

Designs

The most important brake release devices are:

Magnetic brake fan :
They work on the electromagnetic principle. Air damping pistons are used to dampen the strong work shocks .

Sliding rotor brake motor :
It is a connection of drive motor, brake and brake lifting device and also operates on the electromagnetic principle. This type of construction is used, for example, in electric trains. It is characterized by the very short application and opening times of the brake.

Motor pusher :
The motor pusher works according to the electromotive principle. An electric motor drives a centrifugal arm system that converts the centrifugal force into lifting force and thus operates a fan linkage. After the motor has been switched off, the brake spring pushes back the linkage and closes the brake again. The integration of the brake spring into the ventilation device results in a simplified design.
The advantages of this design are any installation position and smooth operation. Long duty cycles and high switching frequencies are possible.

Eldro devices :
These brake release devices work on the electro-hydraulic principle. After the electric motor has been switched on, a centrifugal pump delivers hydraulic oil from a chamber into a cylinder, thereby pushing out a piston with the push rod attached, which releases the brake. The brake remains open as long as the motor is switched on. After switching off, the hydraulic fluid is returned to the chamber by the spring force with the piston and the brake shoes are pressed together. The braking force builds up evenly.

Advantages of the electro-hydraulic brake release devices are:

  • An almost shock-free, continuous build-up of the braking effect;
  • Constant thrust regardless of the piston position;
  • No overloading and readjustment of the braking points due to brake lining wear;
  • High duty cycle and high switching frequency.

Electro-hydraulic devices combine all elements of a hydraulic system in one structural unit. They consist of a hydraulic pump with an electric drive motor, a hydraulic control system and a working cylinder with piston and lifting rod. The hydraulic medium circulates in the housing. Brake release devices are low-pressure hydraulic systems. The requirements for brake release devices are regulated in DIN 15435.

Spindle lifting device :

This type of construction is rarely used today. The brake shoes are released using a spindle drive .

literature

  • Rudolf Griemert, Peter Römisch: Conveyor technology: selection and calculation of elements and assemblies. 11., revised. u. exp. Edition. Springer Vieweg, Wiesbaden 2015, ISBN 978-3-658-09083-8 , p. 56 ff.