Tilting Backrest Joint With Axial Spring Resistance
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Solution Overview
Problem
Existing chair designs with tilting backrests using elastic joints face limitations in opposing backward thrust due to limited elastic force and require additional aesthetic-detracting coverings like bellows.
Innovation Solution
The chair incorporates oscillation joints with a rigid support, a telescopic element, and a helical compression spring, where the elastic device compresses axially to pivot the lever, allowing a 17° angle of tilt without visible additional coverings, integrating the joints within the chair's structure for a unified aesthetic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If elastic elements deformable by bending are used in the elastic joints, then the chair allows backward tilting, but the elastic force opposing the backward thrust is limited
Solution Approach 1:
The patent changes the deformation mode of the elastic element from bending to axial compression. This parameter change allows the elastic element to generate significantly higher compressive forces while still enabling the desired backward tilting motion through the telescopic mechanism.
Solution Approach 2:
The patent introduces a telescopic element that adds a longitudinal dimension to the elastic joint. This allows the elastic force to be applied axially rather than through bending, fundamentally changing the force generation mechanism and enabling higher opposing forces.
2Force
If helical compression springs are arranged coaxially to the side uprights of the backrest, then the elastic force opposing backward thrust is increased, but the lever arm for spring compression is limited
Solution Approach 1:
The patent moves the spring arrangement from a coaxial configuration (limited to the vertical dimension) to a configuration where springs are arranged substantially horizontally. This dimensional change provides a much longer lever arm for spring compression while maintaining the same vertical space constraints.
Solution Approach 2:
The patent introduces a telescopic element that dynamically adjusts the position of the spring during tilting. As the backrest tilts backward, the telescopic element extends or retracts, maintaining optimal spring compression throughout the range of motion and maximizing the lever arm effect.
3Reliability
If additional covering elements such as bellows are used in the elastic joints, then the joints are protected, but the aesthetic appearance of the chair is compromised
Solution Approach 1:
The patent merges the protective covering function with the existing structural elements of the chair. The hollow side housings that are already part of the chair's design serve as the protective enclosure for the elastic joints, eliminating the need for separate bellows or coverings and maintaining a sleek aesthetic appearance.
Solution Approach 2:
The patent makes the hollow side housings multi-functional: they serve both as structural components of the chair and as protective enclosures for the elastic joints. This eliminates the need for additional aesthetic-detracting coverings while maintaining joint protection.
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 enhances the opposition to backward thrust while maintaining a sleek appearance by hiding the joints within the chair's hollow side housings, providing effective tilting functionality without compromising aesthetics.
Implementation Method 1
an elastic device (66) comprising a telescopic element (68) and a helical compression spring (70)
Implementation Method 2
the elastic device compresses axially to pivot the lever
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A chair comprising: - a base structure (12), - a seat (14) fixed to the base structure (12), - a backrest (16), and - a pair of oscillation joints (32) which connect the backrest (16) to the seat (14) or to the base structure (12) so as to allow tilting of the backrest (16) around a transverse axis between a rest position and a backwardly tilted position, wherein each of said oscillation joints (32) comprises: - an essentially L-shaped rigid support (34) - a rigid lever (54) articulated to the rigid support (34), and having a first and a second lever arm (56, 58) located on opposite sides with respect to the articulation axis, and - an elastic device (66) comprising a telescopic element (68) and a compression spring (70), wherein the elastic device (66) applies an elastic force between said rigid support (34) and said first lever arm (56) and wherein said second lever arm (58) protrudes outwards from said rigid support (34) and is fixed to a corresponding side edge of the backrest (16).