1. Purpose
The loader is mainly used to shovel soil, unload and transport soil, stones and other bulk materials during loading. It can also carry out light excavation operations on rocks and hard soil. If you change to other working equipment, it can also complete the bulldozer work, lift and load other materials. It is mainly used for filling subgrade works, asphalt and cement concrete yard aggregate, loading and other operations in highway construction. Because of its fast running speed, good mobility and light operation, it has developed rapidly and become the main machinery in earthwork.
2、 Classification
The commonly used single-bucket loader classifies different loading methods according to the walking structure of the engine power transmission form.
（1）. Engine power:
① Small loader with power less than 74kw.
② Medium loader with power of 74-147kw
③ 147-515kw power is large loader
④ Ultra-large loader with power greater than 515kw
（2）. Transmission mode:
① Hydro-mechanical transmission, small vibration, long service life, easy to operate, speed and external load can be automatically adjusted, usually used for medium and large loaders;
② Hydraulic transmission: stepless speed regulation, easy operation, but poor starting, usually only used for small loaders;
③ Electric drive: stepless speed regulation, reliable operation and maintenance, simple and high cost, usually used for large loaders.
（3）. Pedestrian structure:
① Tire type: light weight, fast and flexible, high mobility and efficiency, not easy to damage the road surface, high ground contact pressure, poor trafficability, but it is widely used;
② Crawler type: low ground pressure, good transmissibility, low center of gravity, good stability, strong adhesion, high traction, high cutting force, low speed, relatively poor flexibility, high cost, easy to damage the road when walking.
（4）. Loading and unloading method:
① Front unloading type: simple structure, reliable working vision, applicable to all kinds of workplaces, and wider application range;
② Rotary type: the working device is installed on a rotatable 360 ° turntable. The side unloading does not need to turn around, and the working efficiency is high, but the structure is complex, high quality, high cost, and the side stability is poor. It is suitable for small places.
③ Rear unloading type: front loading, rear unloading, high efficiency and poor safety.
3、 Selection principle
（1）. Model selection: It is mainly select and determined according to the use occasion and purpose. Generally, operations are carried out in quarries and soft bases, and crawler loaders are often used;
（2）. Power selection: diesel engines are usually used for construction machinery. If the altitude is higher than 3000m in special areas, special plateau diesel engines should be used.
（3）. Selection of transmission type: usually use hydro-mechanical transmission. The key component is the choice of torque converter form. At present, most loaders produced in China use double turbochargers, single stage, two-phase torque devices.
（4）. When selecting a loader, fully consider the braking performance of the loader, including multiple brake parking brakes and emergency brakes. There are three types of brakes: shoe brake, caliper disc type and wet multi-disc type. The driving mechanism of the brake generally adopts an afterburner, and its power is compressed air, which has three types: air cap oil and hydraulic type. At present, the air cap oil brake system is commonly used. Generally, the dual-circuit brake system is used to improve the driving safety.
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