DESIGN OF ELECTRO-HYDRAULIC THRUSTER OPERATED FAIL-SAFE DRUM BRAKE
Introduction
Compared to normal brakes fail-safe brakes engage when the power supply is off. It’s especially useful in cases of crane hoisting mechanism, conveyor belts & anchor hoists in ships where a sudden power failure in the middle of operation can result in dangerous accidents. Normally when the driving force is gone, the load will fall under gravity or continue by inertia which is undesirable & is prevented by this brake which locks up instantly. It is operated by electrically driven thruster( containing a pump) which actuates the mechanism by hydraulic forces.
What is a Brake?
A brake is a device by means of which artificial frictional resistance is applied to a moving machine member, in order to retard or stop the motion of a machine. When the source of power is cut off, moving body will come to rest gradually and it will take a long time. But sometimes it is necessary to stop it within a very short time. Hence artificial frictional resistance is in the form of brake is applied to the moving body to stop it.
The design of a brake depends upon the following factors:
1. The unit pressure between the braking surfaces.
2. The coefficient of friction between braking surfaces.
3. The peripheral velocity of the brake drum.
4. The projected area of the friction surfaces, and
5. The ability of the brake to dissipate heat equivalent to the energy being dissipated.
Characteristics of Material for Brake Lining:
1. It should have high coefficient of friction with minimum fading.
2. The coefficient should remain constant over the entire surface with change in temperature.
3. It should have low wear rate.
4. It should have high heat resistance.
5. It should have high heat dissipation capacity.
6. It should have low coefficient of thermal expansion.
7. It should have adequate mechanical strength.
8. It should not be affected by moisture and oil.
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