Flexible Rotary Shaft Sheath Bending and Vibration Control
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Solution Overview
Problem
Existing devices for transmitting rotational movement in vehicle seat adjustment systems face challenges in being economically produced with quality guarantees, requiring flexibility to bend with small radii, reducing vibration amplitudes, providing insulation during contact, and ensuring lubrication and limited contact between components.
Innovation Solution
A one-piece plastic sheath with a continuous peripheral wall featuring axial and radial protuberances that allows bending while resisting deformation, incorporating annular and radial protrusions for enhanced flexibility and insulation, and annular wings for contact zones, ensuring smooth operation and reduced vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sheath is made flexible to bend with small radii in confined spaces, then the adaptability to tormented shapes is improved, but the structural strength and resistance to deformation deteriorates
Solution Approach 1:
The sheath is divided into multiple axial sections, each capable of independent bending. The peripheral wall is segmented into repeating units that can flex relative to each other, allowing the sheath to navigate tormented paths while maintaining overall structural integrity through the modular design.
Solution Approach 2:
The sheath employs a thin-walled plastic structure with optimized wall thickness and geometric reinforcement. The peripheral wall is designed as a flexible shell that can bend with small radii while the overall cylindrical form and material selection maintain sufficient strength to resist deformation during operation.
2Ease of manufacture
If the sheath is made as a one-piece structure for ease of manufacture, then the manufacturing complexity is reduced, but the ability to provide localized insulation and contact zones deteriorates
Solution Approach 1:
The sheath incorporates axial sections with different external geometries - some sections have protuberances for insulation and contact, while others have smooth surfaces. This local differentiation of surface quality allows the one-piece sheath to provide localized insulation zones and contact areas appropriate for different operational requirements along its length.
Solution Approach 2:
The sheath design varies geometric parameters along its length, including outer diameter, wall thickness, and surface profile. By changing these parameters locally through the axial sections with protuberances and smooth zones, the sheath achieves differentiated functionality (insulation vs. contact) while remaining a single molded piece for ease of manufacture.
3Object-affected harmful factors
If the sheath provides insulation in contact zones to prevent harmful effects, then the protection against extrinsic parts is improved, but the friction and contact resistance increases
Solution Approach 1:
The sheath is segmented into alternating zones: axial sections with protuberances that provide insulation and protection from extrinsic parts, and smooth axial sections that minimize friction during contact. This segmentation allows the sheath to cycle between protective and low-friction modes as it moves through the adjustment mechanism.
Solution Approach 2:
The sheath exhibits periodic variation in its surface geometry along its length, with repeating patterns of protuberanced sections followed by smooth sections. This periodic structure enables the sheath to alternately engage in protective contact (insulation phase) and low-resistance sliding (smooth phase) as it navigates the tormented path between motor and toothed wheel.
Data Source
Figure 1~4B
Figure 5~6
Figure 7~10B
AI summary
The sheath (1) for a flexible rotary shaft comprises a continuous peripheral wall (5) made of plastic bounding a tubular passage (6) for the shaft, able to be curved but resistant to kinking, the wall (5) comprising a plurality of sections with radial and axial protuberances (10), bounded by two transverse planes and an outer peripheral face (10a) comprising a central part (11) inscribed inside a pseudo cylindrical external central shell (11a) and, at least in the regions that are to be curved, at least one radial and axial protrusion (12), extending axially, projecting from the external central shell (11a) and which, in a transverse plane, is situated in a radial plane and, if appropriate, outside this radial plane but near to it.