Today's excavators have a central swivel joint to realize free walking and free rotation of the upper part. However, how did the excavator give consideration to both rotation and walking before the central return switch? This article will describe how the excavator walked and turned before the invention of the central swivel.
Now the common central swivel joint is designed for hydraulic excavator. Before the emergence of hydraulic excavators, except that a few large excavators used electricity as power, most small and medium-sized excavators used mechanical excavators with gasoline or diesel engines. In order to transfer the power of the internal combustion engine to various parts that need power, these excavators use complex mechanical transmission devices, including transmission, clutch, gearbox, winch, steel wire rope, transmission shaft, chain and so on. The hydraulic excavator only needs to be connected to the hydraulic actuator on the corresponding part with pipeline.
As for the traveling device, mechanical excavators generally use the vertical transmission shaft to transmit the power to the lower part. The traveling transmission shaft is located in the center of the rotary table. The upper end is connected with the internal combustion engine through the gearbox and clutch to obtain power. The lower end changes the direction through a pair of bevel gears and transmits power to both sides of the crawler through the transverse horizontal shaft. In this way, no matter what the relative position of getting on and getting off, the power can be transmitted to the chassis.
Of course, after the power reaches the chassis, it still needs to continue to drive. The common way is to use chain drive, with a pair of chains connecting the transverse horizontal shaft and the sprocket on the driving wheel. In this way, when the traveling transmission shaft rotates, it will drive the two driving wheels to rotate and make the excavator walk in one direction through the crawler. Walking in the other direction only needs to change the rotation direction of the transmission shaft.
If you want to turn, like other tracked vehicles, you need a speed difference between the tracks on both sides. There are clutches and brakes on both sides of the horizontal transmission shaft, which can cut off the track power on one side by controlling the clutch to realize steering.
As mechanical excavators are gradually replaced by hydraulic excavators, the above transmission modes are gradually eliminated. As for chain drive walking, not only excavators, but also some crawler vehicles that do not need to rotate also use chain drive to realize walking.
