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 boom cylinder is connected with the fuselage and boom and is the power element to lift the whole working device and materials. Most small and medium-sized excavators with backhoes adopt the lower design of boom cylinder, that is, the boom cylinder is located at the front and lower part of the boom.
The lower hinge point of the boom cylinder is placed on the flange at the front of the turntable and is lower than the lower hinge point of the boom in the vertical direction. The upper hinge point of the boom cylinder of the medium excavator is placed on both sides of the middle of the boom, while the upper hinge point of the boom cylinder of the small excavator is placed on the lower plate in the middle of the boom. The reasonable arrangement of boom cylinder is of great significance to ensure the normal exertion of excavator excavation force and the smooth progress of excavation process.