Working Chair for Physically Disabled Children

Abstract

A product development process was initiated with the purpose of designing a saddle seat working chair for physically disabled children on behalf of Fysionord AB. An objectives tree diagram was made using Mindomo.com. Sub-functions in existing solutions were listed, leading to the discovery of four modules, constituting the working chair: footrest, seat, backrest and undercarriage with wheels. The latter was defined as outside of the system boundary of the project. A requirement specification was compiled, stating demands and wishes regarding the future product. Concepts were generated for each module. This resulted in an adjustable footrest fastened by levers to the rear part of a non-adjustable seat based on mean anthropometrical dimensions of the intended target group. As well as a double curved hexagonal backrest fastened on a sheet metal post, enabling height adjustment. The three module concepts were assembled into a final working chair concept, which was modeled in Autodesk Inventor 2018. Using Ansys Workbench, numerical and analytical strength analysis was implemented on two sheet metal components: the backrest post and the “hub” for fastening all modules. Based on the analysis, the components were iteratively redesigned to reduce stress prior to selecting material, carbon steel AISI 1095, using CES Edupak.