Double shell seat
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Solution Overview
Problem
Existing chair designs that achieve synchronous motion between the seat and backrest, such as the 426 patent, rely on coil springs, which are not ideal due to their mechanical complexity and potential for discomfort or injury.
Innovation Solution
A double shell seat design featuring a movable inner shell within an outer shell, utilizing a resilient hinge and rollers on ramps to transition between upright and reclined positions without the need for coil springs, with flexible edges and padding for user comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil spring is used to achieve synchronous motion between seat and backrest, then the chair can alternate between original and reclined positions, but the mechanical complexity increases and potential for discomfort or injury arises
Solution Approach 1:
The patent removes the coil spring from the synchronous motion mechanism, extracting the problematic component while maintaining the essential function through a simplified design where the seat and backrest move together through geometric constraints rather than elastic storage
Solution Approach 2:
The patent replaces the elastic mechanical system (coil spring) with a geometric constraint system using linkages and pivot points that naturally enforce synchronous motion through their structural configuration, eliminating the need for energy storage elements
2Ease of operation
If a coil spring is used to restore the seat to original position, then the chair can return from reclined position, but user comfort and safety deteriorate due to potential pinching or discomfort
Solution Approach 1:
The patent removes the coil spring that caused discomfort and potential injury, eliminating the source of harmful factors while preserving the position restoration function through alternative means
Solution Approach 2:
The chair's weight and gravity naturally restore the seat to the original position after reclining, eliminating the need for active spring mechanisms that could pinch or discomfort the user - the system uses its own mass to return to equilibrium
3Strength
If the inner shell is made rigid for structural integrity, then the chair maintains strength, but finger pinching hazards increase between inner and outer shells
Solution Approach 1:
The patent applies flexible material to the edges of the inner shell that can deform under pressure, allowing the rigid structural core to maintain strength while the flexible edges prevent pinching by yielding when fingers are trapped during movement
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
Enables smooth synchronous motion between the seat and backrest, enhancing user comfort and safety by eliminating the need for coil springs and providing ergonomic adjustments through weight distribution, while maintaining structural integrity and reducing noise.
Implementation Method 1
The hinge may have resilience that helps restore the inner shell to the upright condition when a person's weight is removed from the inner shell
Implementation Method 2
cooperating ramps and rollers that are on the upper face and the bottom of the seat support are located at positions on the upper face and the bottom of the seat support so that the rollers encounter the ramps
Data Source
AI summary
A double shell seat includes a base for resting on a floor, an outer shell supported by the base, and an inner shell movably supported within the outer shell. The inner shell has a seat support, a backrest support, and a hinge between the seat support and the backrest support. The inner shell is movable with respect to the outer shell from an upright condition in which the seat support has a position toward the rear of the outer shell, the backrest support has a position that is relatively vertical, and the hinge is at a first angle, to a reclined condition in which the seat support is forward of its position in the upright condition, the backrest support is less vertical than its position in the upright condition, and the hinge is open at a greater angle than the first angle. The seat is preferably free of coil springs.