Bellows Extensible Member Structure for Quiet Contraction
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Solution Overview
Problem
Conventional extensible members with thermoplastic elastomer materials often experience abnormal noise during extension and contraction due to air being trapped between surfaces, leading to stress concentration and reduced durability.
Innovation Solution
The extensible member features a design with alternating first and second protrusions on its contact surfaces, positioned at regular intervals around the center axis, facilitating air entry between surfaces and distributing stress uniformly, thereby reducing noise and maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the extensible portion is contracted and folded with the roots as fulcrums, then the two contact surfaces are brought into close contact, but air is trapped between the surfaces and abnormal noise occurs
Solution Approach 1:
The contact surfaces are segmented by providing multiple protrusions that divide the continuous contact area into multiple discrete contact points. This segmentation allows air to escape through the gaps between protrusions during contraction, preventing air entrapment and the associated abnormal noise while maintaining effective contact between surfaces.
Solution Approach 2:
The protrusions create local variations in the contact surface geometry, transforming the uniform contact surface into a non-uniform surface with specific contact points. This local quality change ensures that air can be expelled from specific regions during contraction, solving the noise problem without compromising the overall contact function.
2Reliability
If the protrusions are positioned on the contact surfaces, then air can enter between surfaces during separation, but stress concentration may occur
Solution Approach 1:
By distributing multiple protrusions across the contact surface rather than using a single large protrusion, the stress that would otherwise concentrate at one location is divided and distributed across multiple contact points. This segmentation of the protrusion structure prevents stress concentration while maintaining the air entry function.
Solution Approach 2:
The protrusions are designed to deform dynamically during extension and contraction cycles. The protrusions flex and adapt to the changing geometry of the extensible portion, allowing stress to be distributed throughout the material rather than concentrated at rigid points, thereby maintaining strength while enabling noise reduction.
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
This design effectively minimizes abnormal noise and stress concentration during extension and contraction, enhancing the durability of the extensible member by allowing air to enter between surfaces and ensuring uniform deformation and stress distribution.
Implementation Method 1
The extensible member (20) is made of a thermoplastic elastomer and includes an extensible portion (30) having an outer peripheral surface and an inner peripheral surface in a bellows shape
Data Source
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AI summary
[Problem] To provide an extensible member that allows abnormal noise during extension and contraction to be less likely to occur. [Solution] An extensible member (20) includes a tubular extensible portion (30) and protrusions (41, 42). The tubular extensible portion (30) made of a thermoplastic elastomer has an inner peripheral surface and an outer peripheral surface in a bellows shape in which mountains and troughs are continuous in an axis direction. The protrusions (41, 42) project from the outer peripheral surface. The outer peripheral surface includes outer crests (33), outer roots (34), and first contact surfaces (35) and second contact surfaces (36) between the outer crests (33) and the outer roots (34). The first contact surfaces (35) and second contact surfaces (36) are positioned to be contactable with one another when the extensible portion (30) axially contracts. The inner peripheral surface includes inner crests (37) and inner roots (38). The inner crests (37) are positioned radially inward of all of the outer roots (34). The inner roots (38) are positioned radially inward of all of the outer crests (33). The protrusion (41, 42) is disposed on at least one of the first contact surface (35) and the second contact surface (36).