Folding Chair Slotted Linkage for Flush Backrest-Seat Alignment
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Solution Overview
Problem
Conventional folding chair mechanisms, such as simple hinged joints and linkage hinges, compromise between full opening and full closing angles, leading to suboptimal compactness and potential damage during storage, as fixed linkages restrict the chair's range of motion.
Innovation Solution
A folding chair assembly featuring a slotted linkage system with pivot connections between the backrest, seat, and armrest structures, allowing the backrest to fold flush against the seat, minimizing bulk and enhancing stability through a complex movement mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple hinged joint is used to join the seat to the backrest, then the chair can be folded, but the seat engages the backrest at a slight angle preventing them from being parallel when folded closed
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed-length linkage to a slotted linkage that allows dynamic adjustment of the connection point. The slot enables the linkage to move along its length during folding, allowing the seat and backrest to achieve parallel alignment when closed while maintaining the folding capability. This dynamic adjustment resolves the geometric constraint that prevented parallel alignment in fixed linkage designs.
2Ease of operation
If a linkage hinge with fixed length linkages is used, then the chair can open and close, but the fixed length prevents the chair from opening to a wide angle
Solution Approach 1:
The slotted linkage transforms the fixed-length constraint into a dynamic system where the effective linkage length can vary. As the chair opens and closes, the connection point moves along the slot, allowing the linkage to accommodate a wider range of opening angles while maintaining smooth operation throughout the folding cycle.
3Volume of moving object
If the chair is compressed flat during packing or storage, then space is saved, but the hinge can break or bend damaging the chair
Solution Approach 1:
The slotted linkage provides dynamic movement capability that allows the hinge to accommodate compression forces during packing. Rather than being rigid and prone to breaking, the slot allows the linkage to shift position and absorb the stress of compression, maintaining hinge integrity while achieving compact storage.
4Weight of moving object
If minimal components are used to make the chair lightweight, then portability is improved, but the folding mechanism lacks the complexity needed for optimal folding performance
Solution Approach 1:
The slotted linkage can be implemented as a separate component that integrates with the existing lightweight tube structure. This segmentation allows the added complexity to be localized to the folding mechanism while maintaining the overall lightweight construction, rather than requiring reinforcement of the entire chair structure.
Data Source
AI summary
A folding chair assembly with an improved folding mechanism. The folding chair assembly has a backrest structure, a seat structure, and an armrest structure that are all made from shaped tube forms. The tube form of the armrest structure is attached to the tube form of the backrest structure with a pivot connection. The tube form of the armrest structure is also attached to the tube form of the seat structure at a pivot connection. A slotted linkage is provided that extends between the tube form of the backrest and the tube form of the seat. The slotted linkage is pivotably connected to either the backrest structure or to the seat structure. The slotted linkage defines a slot. The slot engages a fixed pin on either the seat structure or the backrest structure. The fixed pin reciprocally moves within the slot as the folding chair assembly is manipulated.