Stackable Plastic Rocking Chair Rockers That Prevent Splaying
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing stackable plastic rocking chairs fail to meet performance standards due to rocker instability and breakage under weight and repeated rocking, particularly when subjected to ASTM and BIFMA tests, as the outward divergence of legs leads to splaying and structural damage.
Innovation Solution
The design incorporates rockers with an inwardly curved center portion and a sloped base that ensures the inside edge contacts the surface, reducing outward force and incorporating a removable base with snap-fit tabs for expansion during impact, maintaining stability and preventing splaying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the legs diverge outwardly from top to bottom to enable stacking, then the chairs can be stacked for transport and storage, but the rockers splay outwardly under weight and repeated rocking, leading to breakage
Solution Approach 1:
The chair is designed with a nested structure where the rockers are positioned within the leg framework, allowing the rockers to be contained and stabilized by the overall chair geometry while maintaining stacking capability through the outwardly diverging legs
Solution Approach 2:
The solution addresses the splaying problem by introducing a dimensional constraint - the rockers are positioned and shaped to operate within a specific spatial envelope defined by the leg divergence, effectively constraining the rocking motion to a controlled plane and preventing outward splay
2Ease of operation
If the contact area between floor and rockers is small to enable stacking, then the chairs can be stacked, but the rockers are more prone to splaying and breaking under load
Solution Approach 1:
The rockers are designed with non-uniform geometry - the contact area with the floor is minimized at specific points to enable stacking, while the overall rocker structure maintains sufficient strength through varied cross-sections and strategic material distribution in critical load-bearing areas
3Ease of operation
If the legs extend outwardly from vertical for stacking, then the chairs can be stacked one on top of another, but the contact area changes during rocking, causing instability and breakage
Solution Approach 1:
The chair geometry is pre-configured with specifically shaped rockers and leg arrangements that anticipate and compensate for the changing contact area during rocking motion, maintaining stable contact throughout the rocking cycle while preserving stacking capability
Data Source
AI summary
A rocking chair has a seat, a back attached to the seat, a right rocker, at least one right leg connected to the seat and to the right rocker, a left rocker and at least one left leg connected to the seat and to the left rocker. The rockers each have a base having an inside edge and an outside edge the base having a slope such that when the rocking chair is placed on a flat surface a portion of the inside edge will be in contact with the flat surface and the outside edge will not be in contact will the flat surface. The rockers may alternatively or additionally each have an inwardly curving center portion. These features alone or in combination can prevent the rockers from splaying outward when a weight is dropped on the chair or while a person is rocking the chair.