The hydraulic rotary joint is designed to transfer hydraulic power between stationary and rotating components.
Its performance depends on precise internal structure, reliable sealing technology, and durable mechanical design.
Main Structure of Hydraulic Rotary Joint
A typical excavator rotary joint consists of several key components:
1. Housing (Stator)
The housing is the fixed part connected to the excavator undercarriage.It provides:
(1) External protection;
(2) Hydraulic connection ports;
(3) Internal oil passages.
2. Rotor (Rotating Shaft)
The rotor rotates together with the excavator upper structure.
It connects hydraulic circuits to working components and transfers oil flow during rotation.
3. Sealing System
The sealing system is one of the most important parts of the rotary joint.
It separates different hydraulic channels and prevents internal oil leakage, external oil leakage, pressure loss.
Common sealing materials include PU, PTFE, High-performance hydraulic sealing material.
4. Bearing System
Bearings support smooth rotation between the rotor and housing.
They help:
(1) Reduce friction;
(2) Improve rotation stability;
(3) Handle axial and radial loads.
Working Principle
Step 1: Hydraulic Oil Transmission
Hydraulic oil from the pump enters the rotary joint through fixed pipelines.
The oil passes through:
Housing → Annular oil grooves → Rotor passages → Working actuators
Different oil channels control different functions independently.
Step 2: Dynamic Sealing During Rotation
When the excavator rotates, the rotor turns inside the housing.
The sealing system maintains separation between hydraulic channels while allowing continuous rotation.
This ensures:
Stable pressure;
No oil mixing;
Reliable operation.
Step 3: Continuous 360° Rotation
The internal circular oil passage design allows unlimited rotation without interrupting hydraulic transmission.
This enables smooth and continuous excavator operation
Through precision machining and advanced sealing technology, hydraulic rotary joints provide reliable hydraulic transmission under demanding working conditions.
