Laterally Movable Rod Seal Assembly for Oscillating Piston Rods

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Solution Overview

Problem

Existing rod seal assemblies for machines with crossheads and sealed oscillating piston rods face challenges in maintaining effective sealing due to lateral movement of the piston rod, leading to misalignment and leakage of lubrication oil and gas.

Innovation Solution

The proposed rod seal assembly includes a seal housing, a rod seal, a bushing, and a rod seal base, all of which are annular and designed to move laterally in relation to the seal housing. This design ensures that all lateral movement is aligned, reducing wear and maintaining sealing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the piston rod seal is designed to seal between high-pressure and low-pressure regions, then sealing performance is improved, but lateral movement of the piston rod causes misalignment and leakage

Engineering Contradiction:

Improvesealing performanceVSAvoidlateral movement capability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The rod seal assembly is designed with dynamic capability to follow lateral movements of the piston rod. The seal housing and rod seal base are configured to move laterally together with the piston rod, maintaining alignment and sealing effectiveness during oscillation. This dynamic design allows the seal to adapt to lateral displacements while preserving the pressure differential seal.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The rod seal assembly is divided into separate functional components: a seal housing that provides structural support and a rod seal base that directly follows the piston rod movement. This segmentation allows the rod seal base to move laterally with the piston rod while the seal housing remains relatively stable, resolving the contradiction between maintaining seal integrity and accommodating lateral movement.

Inventive Principle:

Principle #1Segmentation

2Reliability

If lubrication is applied to the piston rod to improve sealing, then sealing is improved, but lubrication enters the high-pressure region causing increased wear and reduced efficiency

Engineering Contradiction:

Improvesealing performanceVSAvoidlubrication leakage into high-pressure region

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The harmful factor of lubrication leakage into the high-pressure region is extracted and contained. The seal design specifically targets the lubrication film on the piston rod, preventing it from crossing into the high-pressure region while allowing the lubrication to remain on the low-pressure side where it continues to provide sealing assistance without causing wear.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The lubrication that would normally be considered harmful when entering the high-pressure region is instead utilized beneficially on the low-pressure side. The lubrication film on the piston rod aids sealing between the rod seal and piston rod surface, converting what would be a harmful leakage into a useful sealing mechanism while preventing it from reaching the high-pressure region where it would cause wear.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the rod seal is made laterally movable to follow piston rod movement, then misalignment is reduced, but device complexity increases

Engineering Contradiction:

Improvealignment accuracyVSAvoidrod seal assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The seal housing and rod seal base are merged into an integrated assembly where the rod seal base is positioned within the seal housing. This merging allows the entire assembly to move laterally as a unit following the piston rod, achieving good alignment without requiring complex independent movement mechanisms for each component. The integration simplifies the structure while maintaining the necessary lateral following capability.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3918235B1Improved rod seal assemblies for machines with crossheads and sealed oscillating rods

Publication Date: 2025.04.30 ENERGYINTEL SERVICES LTD

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Figure 3a~3c

AI summary

A rod seal assembly (1) for a machine comprising a crosshead (3) and a sealed oscillating piston rod (100), wherein the rod seal assembly (1) comprising: a seal housing (300), a rod seal (101), a bushing (400) and a rod seal base (200), wherein the rod seal (101), bushing (400) and the rod seal base (200) are annular and can be laterally moved in relation to the seal housing (300) the housing (300) axially supports the rod seal base (200), the rod seal base (200) is adapted to be arranged around the piston rod (100) and is provided with a base portion (106), wherein the base portion (106) comprises a lower axial surface (114) directed in a first axial direction an upper axial surface (113) directed in a second axial direction, wherein the lower axial surface (114) abut the housing (300) and the upper axial surface (113) is provided with a rod seal seat (201), the rod seal (101) is adapted to be arranged around the piston rod (100), and has a first end portion (102) and a second end portion (103), wherein the first end portion (103) is arranged to connect to the rod seal base (200) in the first axial direction, and the bushing (400) is arranged to abut the rod seal (101) in the first axial direction, and the rod seal base (200) and the bushing are arranged to have an axial overlap (250).