Swivel Joint Stem Layout for Leak-Safe Slewing Angle Sensing
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Solution Overview
Problem
Existing swivel joints for construction machines face maintainability issues due to the possibility of hydraulic oil leakage when inserting and withdrawing the rod through an oil passage and drain hole at the slewing center, affecting the reliability and maintenance of the sensor unit for detecting slewing angles.
Innovation Solution
A swivel joint design that includes a stem with a rod insertion hole and a stem-side drain oil passage, isolated from the rod insertion hole, allowing for independent drainage and preventing oil leakage during rod insertion and withdrawal, while maintaining the sensor unit's functionality and facilitating maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rod is inserted through an oil passage and drain hole at the slewing center for sensor unit installation, then the sensor unit can detect slewing angle, but hydraulic oil leakage occurs during rod insertion and withdrawal operations
Solution Approach 1:
The patent divides the stem into functionally independent parts: a rod insertion hole for sensor rod access and a separate drain oil passage for hydraulic fluid drainage. This segmentation allows the sensor rod to be installed and removed without interfering with the sealed drain oil passage, preventing hydraulic oil leakage while maintaining slewing angle detection capability.
Solution Approach 2:
The patent introduces a seal member as an intermediary element between the drain oil passage and the external environment. This seal member prevents hydraulic oil from leaking through the drain oil passage during rod insertion and withdrawal operations, while still allowing the drain oil to flow properly through the passage.
2Ease of repair
If the rod is repeatedly inserted and withdrawn through the oil passage for maintenance, then the sensor unit becomes maintainable, but the frequency of operations increases the risk of oil leakage
Solution Approach 1:
The patent separates the maintenance access path (rod insertion hole) from the hydraulic fluid path (drain oil passage). This allows the rod to be repeatedly inserted and withdrawn for sensor unit maintenance without compromising the seal integrity of the drain oil passage, as the two functions are spatially independent.
Solution Approach 2:
The patent pre-installs a seal member in the drain oil passage before any rod insertion or withdrawal operations. This seal member provides beforehand protection against hydraulic oil leakage, ensuring that even during frequent maintenance operations, the seal integrity is maintained and no oil leakage occurs.
3Volume of moving object
If the drain hole is positioned at the slewing center for compact design, then the overall size is reduced, but it becomes difficult to isolate from the rod insertion path
Solution Approach 1:
The patent segments the stem's internal passages into distinct functional channels: the rod insertion hole and the drain oil passage. Even though both are positioned in the compact slewing center area, their spatial separation within the stem allows independent access and sealing, maintaining compactness while avoiding the complexity of isolating overlapping paths.
Data Source
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AI summary
Provided is a swivel joint for a construction machine, which can detect a slewing angle of an upper slewing body and has a high maintainability. The swivel joint (4) includes a body (41), a stem (43), a lower cover (45), and a sensor unit (5). The sensor unit (5) includes: a rotation angle sensor (51) fixedly attached to an upper end of the stem (43); and a rod (53) having a distal end provided with a detection target (55) to be detected by the rotation angle sensor (51) and a proximal end fastened to the lower cover (45). The stem (43) is formed with: a rod insertion hole (431) for receiving the rod (53) to be inserted therethrough; and a stem-side drain oil passage (433) for allowing a drain oil to pass therethrough.