The digging and material handling operations of a loader are accomplished through the movements of its working device. The loader's working device consists of a bucket, boom, connecting rods, rocker arms, bucket cylinders, boom cylinders, and other components. The entire working device is articulated to the vehicle frame. The bucket is articulated to the bucket cylinders-via the connecting rods and rocker arms-to facilitate the loading and unloading of materials. The boom is articulated to both the frame and the boom cylinders, serving to raise and lower the bucket. Both the tilting of the bucket and the raising/lowering of the boom are hydraulically controlled.
During loader operation, the working device is designed to ensure the following: when the bucket cylinders are locked and the boom cylinders are raising or lowering, the linkage mechanism causes the bucket to undergo-or closely approximate-vertical translation, thereby preventing the bucket from tilting and spilling its load; furthermore, regardless of the boom's position, when the bucket rotates around the boom's pivot point to discharge material, its tilt angle is guaranteed to be no less than 45°, and upon the boom's subsequent descent after unloading, the bucket automatically levels itself. Based on a comprehensive review of loader working device structures both domestically and internationally, there are primarily seven distinct types. These are classified according to the number of components in the linkage mechanism-categorized as three-bar, four-bar, five-bar, six-bar, or eight-bar systems-and further classified based on whether the direction of rotation of the input and output links is identical (distinguished as "forward-rotating" or "reverse-rotating" linkage mechanisms). Regarding the structural design of buckets for earthmoving loaders, the main body is typically fabricated by welding together low-carbon, wear-resistant, high-strength steel plates; the cutting edge is constructed from wear-resistant medium-manganese alloy steel, while the side cutting edges and reinforcing corner plates are manufactured using high-strength, wear-resistant steel materials.
The cutting edges (teeth) of the bucket are classified into four distinct shapes. The selection of a specific tooth shape requires consideration of factors such as insertion resistance, wear resistance, and ease of replacement. Tooth shapes are broadly categorized into sharp teeth and blunt teeth; wheel loaders typically utilize sharp teeth, whereas crawler loaders predominantly employ blunt teeth. The number of bucket teeth is determined by the width of the bucket, with the standard spacing between teeth generally ranging from 150 to 300 mm. Bucket teeth are classified into two structural types: integral and split. Small and medium-sized loaders typically utilize the integral type, whereas large loaders-due to harsh operating conditions and severe tooth wear-commonly employ the split type. The split-type bucket tooth consists of two components: a base tooth (2) and a tooth tip (1); consequently, only the tooth tip requires replacement once worn.
