Folding Chair Hinge Locking Structure for Stable Open and Folded States
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Solution Overview
Problem
Existing folding chairs lack a secure locking mechanism in both the folded and unfolded positions, leading to instability and the need for cumbersome straps or laces, which are aesthetically undesirable and pose accessibility issues for users with reduced mobility.
Innovation Solution
A tubular structure with coaxially hinged tubes featuring cylindrical grooves and cradles at the articulation points, allowing for secure locking in both positions without external restraints, using elastically deformable materials and metal frames with plastic half-shells for enhanced rigidity and aesthetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crutch with rack and pinion mechanism is used to lock the chair in unfolded position, then the chair can be locked in unfolded position, but the crutch is unsightly and can lead to pinching of user's fingers
Solution Approach 1:
The patent removes the traditional crutch mechanism entirely and replaces it with a locking system integrated directly into the hinge assembly. The hinge pin itself becomes the locking element, with locking surfaces formed on the hinge pin and corresponding recesses in the tubes, eliminating the need for separate crutches that cause aesthetic and safety issues.
Solution Approach 2:
The locking function is merged with the hinge assembly. The hinge pin incorporates both the articulation function and the locking function, with locking surfaces integrated into the hinge pin structure. This combines two previously separate functions (hinging and locking) into a single integrated component.
2Device complexity
If no locking mechanism is provided in folded position, then the structure remains simple, but the chair unfolds when stored in folded position
Solution Approach 1:
The hinge pin is designed with asymmetric locking surfaces that automatically engage in a specific orientation. When the chair is folded, the geometry of the locking surfaces ensures they mate in a configuration that prevents unfolding, providing preliminary action that maintains stability during storage without requiring additional locking mechanisms.
3Reliability
If connecting rods are used to lock the chair in unfolded position, then the chair can be locked, but the connecting rods form obstacles making it difficult to access the chair
Solution Approach 1:
The locking function is merged with the hinge assembly. The hinge pin incorporates both the articulation function and the locking function, with locking surfaces integrated into the hinge pin structure. This combines two previously separate functions (hinging and locking) into a single integrated component.
4Reliability
If laces or straps are used to prevent chair from unfolding in folded position, then the chair remains stable during storage, but the operation is tedious and aesthetically undesirable
Solution Approach 1:
The patent removes the need for external laces or straps by integrating the locking function into the hinge assembly itself. The asymmetric locking surfaces on the hinge pin automatically maintain the folded position without requiring separate restraining elements, eliminating the tedious operation of tying laces.
Solution Approach 2:
The hinge assembly with asymmetric locking surfaces serves itself to maintain the folded position. The geometry of the locking surfaces automatically prevents unfolding during storage without requiring user intervention with external laces or straps, making the system self-sufficient.
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 design provides a compact, aesthetically pleasing, and user-friendly folding chair that remains stable in both positions without the need for straps or laces, ensuring secure locking and easy access for all users.
Implementation Method 1
The walls of at least one cradle extend over more than half of the circumference of the tube that it is intended to receive and that the cradle be made of an elastically deformable material, so that in the unfolded position, the tube clips inside said cradle.
Data Source
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AI summary
The invention relates to a folding chair (1) capable of being moved between a folded position and an unfolded position, including: two units, each of which includes first (10, 12) and second (18, 20) tubes hinged together via a hinge pin (23); and a canvas sheet (4), characterized in that each assembly of two tubes comprises a rigid part (32) at the hinge pin thereof, said rigid part being arranged between the two tubes (12, 18) and having: a groove (40) for receiving a tube (12) of the assembly without any degree of freedom; first and second cradles (56, 61) arranged on either side of the hinge pin (23), such that when the chair (1) is in the unfolded position, the first cradle (56) bears against the upper section (18a) of the other tube (18) and the second cradle bears against the lower section (18b) of the other tube (18).