Rotary Union Face Seal With Hydraulic-Pneumatic Gap Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Air turbine shafts in machine tools generate heat during high-speed operation, which can lead to suboptimal coolant placement and potential damage due to dry-running conditions, especially in narrow workpiece cavities.
Innovation Solution
A rotary union with a non-rotating seal carrier and rotating seal element that uses hydraulic and pneumatic forces to maintain a mechanical face seal during coolant flow and separates when coolant is discontinued, preventing dry-running and ensuring accurate coolant placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical face seal is maintained during high-speed rotation, then coolant flow is sealed reliably, but the seal rings may damage under dry-running conditions
Solution Approach 1:
The seal carrier is designed to dynamically adjust its position between extended (sealing) and retracted (gap formation) positions based on operating conditions. During normal operation with coolant flow, the carrier extends to maintain the mechanical face seal. When coolant flow stops or during dry-running conditions, the carrier retracts to create a gap between seal rings, preventing damage while allowing the sealing function to be restored when coolant resumes
Solution Approach 2:
The seal carrier automatically responds to changes in coolant flow conditions without external control. The hydraulic pressure from coolant flow itself acts on the carrier to extend it into the sealing position, and when pressure drops, the carrier automatically retracts to protect the seal rings, creating a self-regulating protective mechanism
2Strength
If coolant flow is provided continuously, then seal rings are protected from dry-running damage, but inaccurate coolant placement occurs in narrow workpiece cavities
Solution Approach 1:
The seal carrier operates in periodic cycles of extension and retraction based on the presence or absence of coolant flow. This periodic action allows the system to alternate between sealing mode (when coolant is needed for protection) and gap formation mode (when precise coolant placement is required), optimizing both seal protection and machining precision at different operational phases
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The rotary union ensures reliable and accurate coolant flow during machining, preventing seal damage and excessive heating by creating a gap between seal rings when coolant is absent, thus maintaining seal integrity and efficiency.
Implementation Method 1
contact of an incompressible fluid under pressure with the net hydraulic surface creates a closing force in a closing direction tending to push the non-rotating seal carrier from the retracted position towards the extended position
Implementation Method 2
contact of a compressible fluid under pressure with the net pneumatic surface creates an opening force in an opening direction tending to push the non-rotating seal carrier from the extended position towards the retracted position
Implementation Method 3
the rotating and non-rotating seal elements are in contact to form a mechanical face seal
Data Source
AI summary
A rotary union for use along an incompressible fluid path between a rotating machine component and a non-rotating machine component includes a non-rotating seal carrier including a non-rotating seal element, which together with the non-rotating seal carrier define a net hydraulic surface on an internal side and a net pneumatic surface on an external side. Contact of an incompressible fluid under pressure with the net hydraulic surface creates a closing force, and contact of a compressible fluid under pressure with the net pneumatic surface creates an opening force.