Shape Memory Locking Ring for Turbomachine Bearing Centering
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Solution Overview
Problem
The existing shaft guide bearings in turbomachines face challenges with precise axial positioning and sealing due to the limitations of traditional threaded systems, which can lead to damage of labyrinth seals and poor centering, resulting in leakage and premature wear of abradable tracks.
Innovation Solution
A shaft guide bearing with an inner ring and an axial locking ring featuring an annular ring made of shape memory material that expands radially when heated above its transition temperature, eliminating the need for threads and allowing for secure axial locking and sealing without damaging tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded element is used to clamp the inner ring axially, then the inner ring can be securely positioned, but the threads have small dimensions resulting in poor centering of the element on the cylindrical bearing surface
Solution Approach 1:
The patent replaces the traditional threaded mechanical connection system with a friction-based mechanical press fit system. The locking ring is pressed onto the cylindrical bearing surface using friction and interference fit, eliminating threads entirely. This substitution resolves the centering issue by providing a large contact area between the locking ring's bearing surface and the cylindrical bearing surface, ensuring accurate alignment without the poor centering caused by small-diameter threads.
Solution Approach 2:
The patent transitions from a one-point contact (thread engagement) to a surface contact system. The locking ring incorporates a cylindrical bearing surface that contacts the shaft's cylindrical bearing surface over an extended axial length, moving the constraint from a single dimensional thread interface to a two-dimensional surface interface, thereby improving centering precision.
2Reliability
If tooling is used to screw the element onto the cylindrical bearing surface, then the element can be secured, but the tooling can damage the lips of the labyrinth seals
Solution Approach 1:
The patent eliminates the screwing operation entirely by replacing the threaded connection with a friction-based press fit system. The locking ring is axially pressed onto the cylindrical bearing surface using a pressing tool that applies force through the locking ring's own structure, not through threaded engagement. This eliminates the need for thread-engaging tooling that could damage labyrinth seal lips, while still achieving secure axial positioning through friction and interference fit.
Solution Approach 2:
The patent extracts and removes the threaded connection mechanism from the assembly process. By eliminating threads from both the locking ring and the cylindrical bearing surface, the patent removes the source of damage to labyrinth seals that occurs during threaded fastening operations, while maintaining the securing function through alternative friction-based mechanisms.
3Volume of moving object
If the small dimensions of the threads are used, then the element can be compact, but the clearance required between the labyrinth seals and the abradable tracks cannot be obtained
Solution Approach 1:
The patent transitions from point-contact threads to extended surface contact. The locking ring's cylindrical bearing surface provides an extended axial contact area with the shaft's cylindrical bearing surface, distributing the securing force over a longer length. This allows adequate radial clearance to be maintained between the labyrinth seals and abradable tracks, which would be impossible with the concentrated stress field of small-diameter threads.
Solution Approach 2:
The patent segments the securing function from the connection function. Instead of using threads that combine both connection and centering in a single small-diameter interface, the patent separates these functions: the friction-based press fit provides centering and positioning, while the axial pressing provides securing, allowing each function to be optimized independently with appropriate dimensions.
4Reliability
If threads are used for mounting, then the element can be secured, but the threaded length is short and the radial dimension of the threads is small making assembly delicate
Solution Approach 1:
The patent replaces the threaded mounting system with a friction-based press fit system. The locking ring is mounted by axial pressing onto the cylindrical bearing surface, creating a secure interference fit without requiring threaded engagement. This eliminates the assembly difficulties associated with short threaded length and small radial thread dimensions, as the pressing operation can be performed with simple axial force application and provides adequate mounting security through friction and interference fit.
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
This solution ensures precise axial positioning and effective sealing by avoiding damage to labyrinth seals and facilitating easy centering, while the shape memory effect allows for multiple deformation cycles, extending the ring's lifespan and maintaining effective blocking at ambient turbomachine temperatures.
Implementation Method 1
an annular ring made of shape memory material mounted in an annular space delimited by two annular grooves formed facing each other in the cylindrical bearing surface and in the internal surface of the ring, the annular ring being able to expand radially by shape memory effect when it is subjected to a temperature above a transition temperature of its material
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
The bearing has a circular sectioned annular retaining ring (64) e.g. split ring, made of shape memory material and mounted in an annular space delimited by two annular grooves (56, 60) formed opposite to one another in a cylindrical seating (26) and an internal surface of a ring (34). The retaining ring radially expands memory shape effect when the retaining ring is subjected to temperature above transition temperature of the material to move from a position in which the retaining ring is contained in the annular groove (56) in a locking position of the ring (34) on the seating.