Updated: Aug 9, 2018
The main hydraulic pump and the pilot pump of the crawler hydraulic excavator respectively output working pressure oil and pilot pressure oil. Operate the final drive handle to turn on the pilot pressure oil and push the left (right) walking main valve spool to slide. The working pressure oil travels through the left (right) main valve spool and the main valve body oil passage, the pipe and the central swivel joint to the left (right) travel motor. The travel motor rotates to drive the crawler travel device to realize the forward, reverse and steering functions of the excavator.
The central swivel joint connects the upper and lower body oil passages of the excavator, and is composed of a casing and a mandrel. The mandrel is mounted on the lower body, and the casing is mounted on the upper body. The mandrel is provided with an annular oil groove and a vertical oil hole, and the vertical oil hole is connected with the oil pipe. The pressure oil is delivered to the travel motor via the main valve spool, the oil port of the central swivel joint housing, the annular oil groove on the mandrel, and the vertical oil hole. When the centre revolving joint with the upper body, the oil port on the housing can be kept open to the oil groove on the mandrel.