Reciprocating Compressor Wiper Assembly with Nested Scraper Rings
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Solution Overview
Problem
Existing scraper arrangements in reciprocating compressors face issues with inefficient oil scraping, potential damage to the piston rod, lack of gas-tightness, and limited adjustability due to wear, leading to oil leakage into the compression chamber.
Innovation Solution
A scraper arrangement featuring two scraper rings with an annular recess and pointed scraping edges, where the second scraper ring is fixed within the first, preventing tilting and floating, and incorporating anti-rotation devices and tension springs for adjustability, ensuring efficient oil scraping and gas-tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single scraper ring is used, then the structure is simple, but the scraping efficiency is insufficient and oil leakage occurs
Solution Approach 1:
The scraper ring is divided into multiple segments (first scraper ring with outer diameter larger than rod, second scraper ring with inner diameter smaller than rod) that work together to improve scraping efficiency. The segmented structure allows each ring to perform specific functions while maintaining overall simplicity
Solution Approach 2:
The second scraper ring is nested within the first scraper ring, with the second ring positioned in an annular recess of the first ring. This nesting arrangement maximizes scraping efficiency within a compact structure, preventing oil leakage without significantly increasing overall device complexity
2Strength
If metal scraper rings are used, then the structural strength is high, but the piston rod can be damaged
Solution Approach 1:
The scraper rings are made of composite material (metal matrix with polymer coating) that combines the high strength and stiffness of metal with the low friction and non-damaging properties of polymer. This allows the scraper ring to maintain structural integrity while being gentle on the piston rod surface
Solution Approach 2:
The material parameters of the scraper ring are changed by applying a polymer coating (such as PTFE) on the metal substrate. This changes the surface properties to reduce friction and prevent damage to the piston rod, while the metal core maintains the required mechanical strength
3Stability of the object's composition
If the scraper ring is fixed rigidly, then the positioning is stable, but the ring cannot be readjusted for wear
Solution Approach 1:
The scraper ring incorporates a dynamic adjustment mechanism with tension springs that allow the ring to self-adjust its position as it wears. The springs provide continuous radial force to maintain contact between the scraper edges and the piston rod, enabling the ring to adapt to wear over time while maintaining stable positioning during operation
4Adaptability or versatility
If the scraper ring is made flexible, then the adaptability to wear is improved, but the gas tightness is reduced
Solution Approach 1:
The scraper ring is segmented into multiple rigid segments connected by flexible joints. This segmentation allows the ring to adapt to wear through small angular adjustments at the joints while maintaining the rigidity needed for gas tightness. Each segment remains structurally sound while the overall ring can accommodate wear
Solution Approach 2:
The use of composite materials with appropriate mechanical properties provides sufficient rigidity to maintain gas tightness while allowing for controlled flexibility in the adjustment mechanism. The material selection balances stiffness for sealing with enough compliance for wear accommodation
5Ease of operation
If the scraper ring tilts axially, then the installation is easier, but the wiping efficiency decreases
Solution Approach 1:
The scraper ring incorporates curved or tapered surfaces that guide the ring into proper alignment during installation. The curved geometry allows the ring to self-align and reduce axial tilting as it is installed, maintaining wiping efficiency while facilitating easier installation through self-centering action
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 arrangement enhances scraping efficiency, prevents oil leakage, and extends the service life of the piston rod by maintaining contact with the rod and ensuring continuous sealing, even with wear, thus preventing oil from entering the compression chamber.
Implementation Method 1
incorporating anti-rotation devices and tension springs for adjustability, ensuring efficient oil scraping and gas-tightness
Implementation Method 2
designed to scrape the oil off the piston rod as completely as possible
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A wiper assembly (1) for wiping a medium to be sealed from a rod (4), preferably for wiping oil from the rod of a reciprocating compressor, is described. The wiper assembly (1) consists of a first wiper ring (2) and a second wiper ring (3) enclosed in a circumferential recess (14) of the first wiper ring (2). Both the first wiper ring (2) and the second wiper ring (3) have separate wiper edges (7, 24). This significantly increases the wiping and sealing efficiency and prevents or significantly minimizes the wiper rings from "floating" on the rod (4), since the wiper edges (7, 24) do not make contact with the rod (4) over a surface area but only at specific points in the axial direction. This point contact ensures that the wiper edges (7, 24) remain in contact even during tilting movements of the wiper assembly (1) initiated by the rod movement.The wiper assembly (1) can be made gas-tight by means of an overlapping joint (31) of the second wiper ring (3), thus preventing even indirect leakage paths. The wiper assembly (1) can be completed by a pressure ring (34), which applies axial force to the wiper assembly (1), thereby pressing the sealing surfaces (13, 28) of the first wiper ring (2) and the second wiper ring (3) against the wall of the housing (48) or the cover.