The Modular Polymer Wheelchair
The main component – Made from HDPE. The part which serves several purposes. We went with a honeycomb structure in certain parts of the design and so on the central axle, which is a hexagonal tube, the main components slide on. 3 of the components are placed on either side, in different orientations. By doing this, they form the positions and supports for the arm rests, seat rest and back rest components. Additionally a further component connects to itself, to form the connection to the caster wheels. The numbers of this component per wheelchair is 8. The exploded view below illustrates the assembly and orientation of these components. It was designed to be simple to disassemble and construct, with little labour costs involved at manufacture.
Backrest – Component slides onto the innermost main components. This part is intended to be modular. So the width and shape of this part could be changed for an individual from a select number of options, meeting to their own needs and comfort levels. Padding can also be changed.
Seatrest – This part slides onto the middle main components. Also designed modular so width can be varied and padding altered. There is room on the central axle for variations in width within the design.
Armrest – This part is designed to be optional. If the person is not going to be sitting around stationary for long periods of the day they can opt to leave it off. There is also the option that much more padded armrest elements could be attached if the person knows they are going to be sitting stationary for long periods and therefore want addditional comfort.
Wheel – The wheel is designed to be injection moulded in two main parts. These interlock into each other forming a permanent part. There is a number of main snap fits and the honeycomb mesh essentially sandwiches into each other, making the parts very strong. It is designed to be made from nylon. Around the outside, the tyre would be fitting on. Research explored possible tyre options and there is the option to use any, but we thought the newer flat-less ones would be best suited.
Design for injection moulding
We also produced CAD designs to show the intended snap fits and how the components would be manufactured. The main component here, is designed to be made from two parts and permanently attached together using rugged large snap fits. Because the snap fits work at opposite angles to the way most of the forces act, we foresee little problem with this part structurally. We explored the limitations and the required wall thickness’s offered to us by the injection moulding process.