For general backhoe hydraulic excavators, no matter how heavy the machine is and how large the operation size is, they mainly excavate below the ground. Therefore, in order to meet the maximum excavation depth, the boom is usually made into a downward bending shape. The boom is hinged with the slewing platform and stick through the pin shaft. It is one of the main components of the backhoe working device. The integral curved boom of backhoe excavator has the advantages of simple structure, light weight and high stiffness, which can make the excavator have a large excavation depth. It is the most widely used structural form at present. Its disadvantage is that there are few replaceable working devices and poor universality. It is mostly used on excavators with similar long-term operating conditions.
The integral bending boom is the main form of the boom of backhoe excavator. The downward bending form is mainly used to achieve a large excavator depth. The boom consists of upper and lower straight sections and three sections bent in the middle. The boom is welded as a whole. In terms of structure, the integral bending boom is a left-right symmetrical closed medium empty box welded structure. Generally, the hinged parts of the upper and lower ends are steel castings, and the three sections in the middle are high-strength and high-quality steel plates.
Stiffened plates are generally welded inside the boom, especially at the hinge with the boom oil cylinder, to further strengthen the local strength and ensure that the boom has high bending and torsional strength as a whole.
Due to the bending and processing technology, the bending boom has inevitable welding deformation and stress concentration at the bending, so the processing technology and strength are very important. In the production process, ultrasonic flaw detection is usually used, and the boom without any small cracks will be considered as qualified products.
In order to meet the demand of heavy-duty operation, many excavator manufacturers will optimize the design of boom structure. For example, Sumitomo brand excavator adopts two-stage boom structure, and the upper and lower hinged ends adopt forged parts. According to the comparison of market users, the boom of caterpillar excavator will be relatively strong and durable. It is worth noting that long-time installation of crushing hammer and overweight excavation will cause great damage to the boom of the excavator.
