crane machine often needs to start, brake or stop. Therefore, a good and reliable crane brake device is needed. crane brake system is divided into brake and stop.The crane brake system has the following functions: Support; Speed regulation or speed limit; Braking. Brake: use friction to convert part or all kinetic energy of mechanical motion into heat energy, and achieve the purpose of deceleration or braking. Stop: the use of mechanical backstop to support the object, to achieve the purpose of not moving the object. Crane Brake system The brake should meet the following basic requirements: A. Brake torque can be generated to meet the requirements. B. The loose brake and the lock brake are fast and steady, and the movement of crane brake is accurate and reliable C. The wear resistance and heat resistance of friction parts are good. D. Compact structure and small size. E. Adjustment and maintenance are convenient. Brake type is divided into block type, belt type and disk type according to the structure; according to the working state, there are two types of normally closed type and normally open type. Normally closed brake: when machine doesn’t work, the brake operation; when machine work, the brake release. Normally open type brake: brake is often in the release state, only when required. Structure and type of block brake Advantages: block brake structure is simple, convenient installation and adjustment, widely used in various types of electric crane. Block brake is divided into electromagnetic block brake and hydraulic brake block. The electromagnetic brake block is divided into short distance and the long distance. electromagnetic block brake Short stroke electromagnetic block brake Advantages: on the brake, brake action quickly; small volume and light weight; the hinge less death stroke is small; and the brake pad brake arm, the brake pad and the brake wheel contact wear uniform, uniform. Disadvantages: suction is limited, is often used in braking moment smaller institutions, brake wheel diameter is not greater than 300 mm. Therefore, when the brake torque is large, the electromagnetic block brake must be long stroke. Compared with the hydraulic block brake, electromagnetic block brake big disadvantage is the electromagnet big impact, cause the mechanism of vibration. Because of the frequent starting, braking and electromagnet collision, the service life of electromagnet is reduced, so it is necessary to overhaul and replace it frequently. Hydraulic push rod brake pad The hydraulic push rod releaser in hydraulic push rod brake pad, is an independent part of the hydraulic rod into electric hydraulic push rod and electromagnetic hydraulic push rod. Electric hydraulic push rod: Advantages: smooth movement; unit time of high engagement, thrust constant; motor power is small. Disadvantages: due to the large inertia of motor rotor and lever system, long time of brake and release, it is not suitable for lifting mechanism. Electromagnetic hydraulic push rod: Advantages: both hydraulic brake and electromagnetic brake two advantages, stable braking, no noise, reliable work, long life. Disadvantages: complex structure, high cost, difficult maintenance, popularization and application is limited.