Dual-Spring Seat Tilting Mechanism for Progressive Backrest Resistance
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Solution Overview
Problem
Existing seat tilting mechanisms face challenges in providing consistent resistance to rotation, leading to uncontrollable tilting due to varying user weights, and existing solutions either require complex configurations or increased costs and complexity when trying to adjust angular displacement ratios.
Innovation Solution
A seat tilting mechanism that incorporates a first coil spring and a second coil spring with an engagement mechanism, where the second coil spring is activated at a pre-determined length of extension, providing increased resistance to prevent over-rotation and ensuring user control throughout the tilting range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stronger resistance coil spring is used to prevent uncontrollable tilting, then the backrest can be supported against user weight, but it becomes too difficult for lighter users to push the backrest away from vertical initially
Solution Approach 1:
The resistance mechanism is segmented into two distinct coil springs: a first coil spring that provides initial resistance for easy tilting, and a second coil spring that engages at a pre-determined extension point to provide additional resistance for preventing over-rotation. This segmentation allows each spring to be optimized for its specific function, resolving the contradiction between ease of operation and stability.
Solution Approach 2:
The resistance mechanism transitions dynamically from a single-spring system to a dual-spring system as the first coil spring reaches its pre-determined extension length. The engagement mechanism activates the second coil spring only when needed, creating a dynamic resistance profile that adapts to the tilting angle and user force, thereby maintaining ease of operation for light users while ensuring stability for heavy users.
2Ease of operation
If a resistance coil spring is used to provide resistance to tilting, then some control is provided, but the force applied by the user increases the further the backrest is rotated, reducing control at extreme angles
Solution Approach 1:
The second coil spring is pre-configured with an engagement mechanism that activates at a pre-determined extension length of the first coil spring. This preliminary arrangement ensures that additional resistance is automatically applied before the backrest reaches extreme angles where user control would naturally diminish, maintaining consistent control throughout the entire tilting range.
Solution Approach 2:
The dual-spring system provides progressive feedback resistance: the first coil spring provides initial feedback for normal tilting operations, and when it reaches its pre-determined extension, the engagement mechanism activates the second coil spring to provide additional feedback resistance. This feedback mechanism ensures consistent control by adapting the resistance level to the tilting angle and user force applied.
3Reliability
If concentric inner and outer compression springs are used to increase spring rate, then resistance is improved at certain compression degrees, but this arrangement cannot be used with chairs that have space only for extension springs
Solution Approach 1:
The invention uses a universal extension spring mechanism that can be applied to both quadrilateral hinge systems and other tilting mechanisms. By using extension springs instead of compression springs, the design achieves multi-functionality and broad compatibility across different chair types, eliminating the limitation of Stevens' concentric spring design which only works with specific compression-based mechanisms.
Solution Approach 2:
The mechanism dynamically transitions from single-spring to dual-spring operation based on extension length rather than using fixed concentric arrangements. This dynamic approach allows the system to adapt to available space and provides the increased spring rate effect of concentric springs while maintaining compatibility with extension spring-based quadrilateral hinge systems.
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 mechanism offers enhanced user control and comfort by maintaining consistent resistance to tilting, preventing uncontrollable rotation and addressing the exponential increase in weight's impact on resistance, while being compact and cost-effective.
Implementation Method 1
a first coil spring mounted between said main body and said support member to provide resistance to rotation of said support member
Implementation Method 2
a second coil spring and an engagement mechanism which engages said second coil spring for resistance to rotation of said support member when said first coil spring reaches a pre-determined length when placed under load in use
Data Source
Figure 1~2
Figure 3~4
AI summary
A seat tilting mechanism comprising a main body, a support member rotationally mounted to said main body, and a first extension coil spring mounted between said main body and said support member to provide resistance to rotation of said support member, in which said seat tilting mechanism further comprises a second extension coil spring and an engagement mechanism which engages said second extension coil spring for resistance to rotation of said support member when said first extension coil spring reaches a pre-determined point of extension.