A loader performs digging and material handling operations through the movement of its working mechanism. This mechanism consists of a bucket, boom, connecting rod, rocker arm, bucket cylinder, and boom cylinder. The entire assembly is pivotally mounted to the chassis. The bucket is connected to the bucket cylinder via the connecting rod and rocker arm to facilitate loading and unloading, while the boom connects to the chassis and the boom cylinder to raise and lower the bucket. Hydraulic controls operate both the bucket tilting and the boom lifting/lowering functions.
The working mechanism must meet specific operational requirements: when the bucket cylinder is locked and the boom is raised or lowered, the linkage ensures the bucket moves vertically (or nearly so) without tilting, thereby preventing material spillage; when the bucket rotates around the boom pivot point to discharge material-regardless of the boom's position-the tilt angle must be at least 45°, and the bucket must automatically return to a level position as the boom lowers after unloading. Loader working mechanisms generally fall into seven structural categories based on the number of linkage components (e.g., three-, four-, five-, six-, and eight-bar linkages) and the relative direction of input and output link rotation (e.g., direct-rotation vs. reverse-rotation linkages). Regarding bucket construction for earthmoving loaders, the bucket body is typically fabricated from welded low-carbon, wear-resistant, high-strength steel plate; the cutting edge utilizes wear-resistant medium-manganese alloy steel; and side cutters and reinforcing corner plates are made from high-strength, wear-resistant steel. Bucket cutting edges come in four distinct shapes. Tooth selection takes into account factors such as penetration resistance, wear resistance, and ease of replacement.
