Bellows-Sealed Hydraulic Damper for External Leakage Elimination
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Solution Overview
Problem
Hydraulic dampers experience external leakage of damping fluid due to worn or damaged seals, leading to unscheduled maintenance and increased through-life costs, particularly in aerospace applications where extended Mean Time Before Overhaul (MTBO) is desired.
Innovation Solution
A hydraulic damper design featuring a sealed bellows assembly without traditional seals, where the first and second bellows sections are welded to closure elements and the damping plate, and an annular space with a threaded retaining ring secures the end cap, preventing fluid leakage and allowing for axial movement between cylinders to facilitate fluid transfer through a damping passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional rod gland seals are used to prevent leakage, then seal reliability is improved, but leakage occurs due to worn or damaged seals and planned leakage for lubrication
Solution Approach 1:
The patent removes the traditional rod gland seal entirely from the system. Instead of using a seal at the rod-gland interface, the invention extracts the sealing function and relocates it to a bellows assembly that hermetically seals the damping fluid within the piston assembly, eliminating the source of external leakage around the rod.
Solution Approach 2:
The bellows assembly acts as an intermediary component that provides the sealing function. Rather than relying on contact seals between the rod and gland, the bellows hermetically encloses the damping fluid, mediating the sealing requirement without direct contact between moving parts.
2Reliability
If rod gland seals are used to contain damping fluid, then fluid containment is improved, but leakage onto adjacent hot surfaces occurs causing safety hazards
Solution Approach 1:
The patent extracts the sealing function from the traditional rod gland seal location and relocates it to the bellows assembly. This removes the vulnerability point where leakage onto hot surfaces occurs, as the bellows hermetically seals the fluid within the piston assembly away from external surfaces.
Solution Approach 2:
The bellows assembly provides beforehand cushioning by hermetically sealing the damping fluid before it can potentially leak onto hot surfaces. The sealed bellows structure prevents fluid escape in advance, protecting against the harmful effect of hazardous leakage before it can occur.
3Ease of operation
If traditional seals are used in the damper, then seal lubrication is maintained through planned leakage, but unscheduled removal is required due to seal wear and damage
Solution Approach 1:
The patent removes the traditional seal arrangement that requires lubrication through controlled leakage. By extracting the seal from the rod-gland interface and replacing it with a bellows assembly, the system eliminates the need for seal lubrication while extending service life, as the bellows hermetically seals without requiring lubrication.
Solution Approach 2:
The invention replaces the expensive, wear-prone rod gland seal with a more durable bellows assembly that does not require periodic replacement due to wear. The bellows provides long-term reliable sealing without the maintenance cycle associated with traditional seals.
4Object-generated harmful factors
If a sealed bellows assembly is used without traditional seals, then external leakage is eliminated, but the complexity of welding and assembly increases
Solution Approach 1:
The patent merges the sealing function into the bellows assembly structure itself, combining the bellows with the piston assembly in a hermetically sealed unit. This integration eliminates the need for separate rod gland seals and their associated complex assembly requirements, as the bellows itself provides the hermetic seal.
Solution Approach 2:
The invention replaces the mechanical seal system (rod gland seal with contact surfaces) with a bellows-based hermetic sealing system. This substitution eliminates the complexity of seal installation, adjustment, and maintenance associated with traditional mechanical seals.
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 solution completely contains the damping fluid, reducing external leakage, improving damper performance by eliminating internal leakage through piston head seals, and enabling on-condition maintenance, suitable for low to medium amplitude, high frequency applications.
Implementation Method 1
hydraulic fluid within the contracting chamber is forced from the contracting chamber, through the damping passage, and into the expanding chamber
Implementation Method 2
A hydraulic damper having a closed hydraulic circuit without seals
Data Source
Figure 1
AI summary
A hydraulic damper (10) comprises an outer cylinder (12), and an inner cylinder (20) slidably mounted within the outer cylinder (12) for movement relative to the outer cylinder (12) along a longitudinal axis (A). The inner cylinder (20) has a circumferential wall (37) circumscribing a bellows assembly (B). The bellows assembly (B) comprises a first bellows section (24), a second bellows section (28), a damping plate (32) attached to and separating the first and second bellows sections (24, 28), a first closure element (46) closing an end (45) of the first bellows section (24) opposite the damping plate (32) to define a first chamber (26), and a second closure element (60) closing an end of the second bellows section (28) opposite the damping plate (32) to define a second chamber (30). The first closure element (46) is attached to the inner cylinder (20) for movement therewith relative to the outer cylinder (12). The second closure element (60) is also attached to the inner cylinder (20) for movement therewith relative to the outer cylinder (12). The damping plate (32) has a damping passage (40) extending therethrough and fluidly connecting the first chamber (26) and the second chamber (30). The damping plate (32) is fixed to the outer cylinder (12) by a plurality of elements (34), each element (34) extending through a respective opening (36) in the circumferential wall (37) of the inner cylinder (20), whereby the damping plate (32) remains fixed relative to the outer cylinder (12) in the longitudinal direction during movement of the inner cylinder (20) relative to the outer cylinder (12) in the longitudinal direction.