Reciprocating Compressor Wrist Pin Retention Using Non-Metallic Plugs
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Solution Overview
Problem
Reciprocating refrigeration compressors face challenges in effectively retaining wrist pins, which can lead to axial movement and wear issues, particularly when using traditional retention methods like clips and polymeric washers.
Innovation Solution
The use of non-metallic plugs with a hollow stem and head, where the stem protrudes from the underside of the head and features a pressure relief channel, provides axial retention of wrist pins by cooperating with the cylinder walls, eliminating the need for clips or press-fitting tools, and is made from polybutylene terephthalate for durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional retention methods like clips and polymeric washers are used, then the wrist pin can be retained, but axial movement and wear issues occur
Solution Approach 1:
The invention removes the traditional clips and polymeric washers from the retention system and replaces them with plugs that are integrated into the piston structure. The plugs are pressed directly into recesses in the piston, eliminating the need for separate retention components and their associated failure modes.
Solution Approach 2:
The plugs serve as intermediary elements between the wrist pin and the piston. They are pressed into recesses in the piston and engage with the wrist pin, providing a reliable retention mechanism that prevents axial movement while distributing loads more effectively than traditional clips.
2Reliability
If clips are used to retain the wrist pin, then retention is achieved, but the assembly process becomes complex requiring press-fitting tools
Solution Approach 1:
The retention function is merged into the piston structure itself through the plugs. The plugs are pressed into recesses that are part of the piston manufacturing process, combining the retention mechanism with the piston assembly and eliminating the need for separate retention components and specialized assembly tools.
Solution Approach 2:
The plugs are designed to be self-retaining through their press-fit connection to the piston. Once pressed into the recesses, they automatically secure the wrist pin without requiring additional tools or complex assembly procedures, making the process simpler and more self-contained.
3Reliability
If traditional retention mechanisms are used, then the wrist pin is retained, but pressure-driven outward movement can still occur
Solution Approach 1:
The plugs provide localized reinforcement at the wrist pin retention points in the piston. By pressing plugs into recesses at the specific locations where the wrist pin contacts the piston, the structure is strengthened locally to resist pressure-driven outward movement without affecting the overall piston design.
Solution Approach 2:
The plugs appear to be made from a composite or engineered material that combines strength and durability properties. This material provides enhanced resistance to pressure-driven movement compared to traditional retention methods, while also being durable enough to withstand the operating conditions.
Data Source
AI summary
A compressor (20) has a case (22) and a crankshaft (38). The case has a number of cylinders (30-32). For each of the cylinders, the compressor includes a piston (34) mounted for reciprocal movement at least partially within the cylinder. A connecting rod (36) couples each piston to the crankshaft. A pin (44) couples each connecting rod to the associated piston. Each pin has first (52) and second (53) end portions mounted to first (56) and second (57) receiving portions of the associated piston and a central portion (48) engaging the associated connecting rod. For each of the pistons a pair of first and second at least partially non-metallic plugs have respective stems received in the pin first and second end portions and respective heads facing a wall surface of the associated cylinder.