Gas Spring Piston Rod Segmentation for Volume Reduction
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Solution Overview
Problem
Conventional gas springs with solid piston rods have limited force increase due to small diameter ratio, leading to increased manufacturing costs and gas chamber volume when attempting to achieve longer strokes, resulting in inefficient force distribution and pressure increase.
Innovation Solution
A two-piece piston rod design with a hollow second portion connected to a first portion, allowing for a larger diameter and longer length at reduced cost, featuring a rod guide for guided movement and a seal to prevent gas leakage, which reduces the gas chamber volume and maintains effective force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the piston rod diameter is increased to gain more effective force, then the force increases, but the gas chamber volume increases and pressure increase during stroke becomes excessive
Solution Approach 1:
The piston rod is divided into two separate portions: a first portion with a blind bore cavity and a second portion as a hollow tube. This segmentation allows the piston rod to achieve the necessary force while maintaining a smaller overall volume in the gas chamber, as the hollow construction reduces the displaced gas volume compared to a solid rod of equivalent strength.
Solution Approach 2:
The rod guide is disposed within the hollow second portion of the piston rod, nesting the guiding mechanism inside the piston rod structure itself. This eliminates the need for additional external guiding components that would consume gas chamber volume, thereby maintaining compact dimensions while providing necessary guidance for the piston rod reciprocation.
2Length of moving object
If the piston rod length is increased to achieve longer stroke, then the stroke length increases, but the manufacturing cost increases dramatically due to deeper bore requirements
Solution Approach 1:
The piston rod is segmented into two portions that can be manufactured separately and then connected. The first portion requires a blind bore only for its specific functional length, not for the entire stroke length. This segmentation allows each portion to be manufactured with reasonable bore depths, avoiding the exponentially increasing costs associated with machining very deep bores in a single-piece rod.
Solution Approach 2:
Instead of achieving the full hollow length in a single piece (which would require a prohibitively deep bore), the hollow configuration is achieved by connecting a partially-hollow first portion with a hollow second portion. This dimensional approach allows the effective hollow length to be extended without requiring a single continuous deep bore, thereby reducing manufacturing complexity and cost.
3Volume of stationary object
If a hollow piston rod is used to reduce gas chamber volume, then the volume is reduced, but the manufacturing cost increases dramatically with deeper bores
Solution Approach 1:
The hollow piston rod is segmented into two portions: the first portion with a blind bore of moderate depth, and the second portion as a hollow tube. This segmentation achieves the volume reduction benefit of a hollow rod while avoiding the prohibitively high manufacturing costs associated with creating a single deep bore through the entire rod length. Each portion can be manufactured with reasonable bore depths.
Solution Approach 2:
The hollow configuration is applied partially rather than excessively - the first portion has a blind bore only as deep as necessary for its specific function, and the second portion is hollow but connects to it. This partial application of hollow construction achieves sufficient volume reduction without requiring excessive bore depths that would make manufacturing prohibitively expensive.
4Length of moving object
If a longer bearing surface is provided to achieve longer stroke, then the stroke length increases, but the gas chamber volume consumed by the bearing assembly increases
Solution Approach 1:
The rod guide is nested within the hollow second portion of the piston rod, with the bearing surface for guiding the piston rod reciprocation located inside the hollow structure. This nesting eliminates the need for a separate external bearing assembly that would consume additional gas chamber volume, thereby allowing longer stroke without proportionally increasing the volume consumed by bearing components.
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 two-piece piston rod design enhances force delivery with a flat force curve, achieving increased effective force while minimizing gas chamber volume and manufacturing costs, allowing for longer strokes with improved guided movement and reduced pressure increase.
Implementation Method 1
a gas chamber which receives a pressurized gas that provides a force on a piston
Implementation Method 2
a seal generally provided between the piston rod and the casing to prevent gas leakage from the gas chamber
Data Source
AI summary
In at least one embodiment, a gas spring includes a casing (14) having an inner surface defining in part a gas chamber (24), a piston rod (12) and a seal (86). The piston rod (12) is received at least partially in the casing (14) for reciprocation along an axis between extended and retracted positions. The piston rod (12) has an internal cavity defining a hollow space, a stop and a rod guide (68) disposed adjacent to the inner surface of the casing to guide the reciprocation of the piston rod at least in part. The seal (86) generally is provided between the piston rod and the casing to prevent gas leakage from the gas chamber.