Easy folding cross brace design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional director's chairs suffer from a 'snapping' action during folding and finger pinching due to the design of the frame, which compromises ease of use and transportation, as the frame members spread apart, stretching the fabric and causing discomfort.
Innovation Solution
The design features pivotally connected cross-members that collapse from an X-shape to a parallel relationship, allowing the frame side assemblies to nest within the cross-members, reducing the chair's footprint and eliminating finger pinching through the use of slotted links and snubbers to prevent over-center motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the frame members are designed to spread apart during folding, then the chair can be collapsed to a flat condition, but this causes a snapping action and fabric stretching that leads to finger pinching
Solution Approach 1:
A fabric loop is introduced as an intermediary element between the spreading frame members and the fabric back support. The loop is attached to one frame member and passes through a guide on the opposing frame member, allowing the frame to spread during folding while the loop controls the motion to prevent snapping and fabric stretching that causes finger pinching
Solution Approach 2:
The design changes the motion parameter of the frame members during folding by using the fabric loop and guide system to convert the direct spreading motion into a controlled motion that maintains fabric tension without excessive stretching, thereby eliminating the snapping action while still achieving flat collapse
2Volume of moving object
If the cross-members are pivotally connected to facilitate side-by-side folding, then the chair can be collapsed to a flat condition, but this requires precise pivot positioning to prevent over-center motion
Solution Approach 1:
Snubbers are introduced as intermediary elements between the pivot points and the cross-members. These snubbers act as mechanical stops that prevent the cross-members from rotating past the center position during folding, eliminating the need for complex over-center mechanisms while maintaining the flat collapse capability
Solution Approach 2:
The snubbers are positioned to engage before the cross-members can complete their rotation past center, preliminarily stopping the motion at the appropriate point. This preliminary action prevents over-center rotation without requiring the cross-members to be designed with complex built-in stopping mechanisms
Data Source
AI summary
First and second U-shaped cross-members each have legs connected by cross bars and pivotally connected with each other at central portions thereof, and are mutually movable from a generally X-shaped setup condition in which the cross bars are transversely spaced apart, to a generally flat collapsed condition. Right and left frame side assemblies respectively are pivotally connected to the first and second cross-members at terminal ends of their respective front and rear portions and by at least one lost motion linkage.