Our team was tasked to create a chair for a child who has H.I.E. and Hypoxia. The child has no upper body support, and therefore cannot sit up by themselves. The child currently has a few different utility chairs/devices but is unable to sit upright in any of them without discomfort. This new chair would allow the child to be able to interact with family at dinner, easily sit upright for feedings, and much more.
Due to the child’s conditions, they do not have any upper body support. The main goal of this chair would be to give support to the chest and head regions. The supports should not be constricting, but also have enough force to keep the child from falling out of the chair. The chair would also have an area for a pole to attach, which would be used to store their feeding pouch and tubes. The chair would have some sort of strap on the back, so it could be attached to other chairs. The chair needs to stay light enough for travel purposes, but not so light that the child could tip it over. On top of this, we would like to add a few additional accessories to the chair which would make the family’s lives easier. These include but are not limited to an overhead attachment that could hang toys or a mobile, a side tray attachment that could be used for storage, armrests for the child to rest their arms on, a footrest that could be removed if necessary, etc.
Due to the child’s use of feeding tubes, the design must have measures to prevent any incident. The design should not have too many moving parts, as they could easy pinch or pull at the feeding tubes. Alongside this, the IV pole must stay upright as often as possible, to lower the risk of the feeding bags falling off.
Our first concept design is a much like a car seat for a small toddler. The seat includes a torso strap, head strap, 2 seat straps(back & bottom), a foot rest, and IV pole holder. The torso straps are fairly similar to backpack/car seat straps for small children. These straps help support the child’s upper body. The head straps do the same thing but for the child’s head and spine. We are thinking about using some kind of elastic band that provides a good amount of support but still enough where he can move his head freely if he so choses.
PROS: Simple, Cost Effective
CONS: Bulky, Non-Adjustable
This design has more adaptability to it than the first concept design. This design has telescopic legs on the foot rest so when the child gets older they can adjust for his height. The same telescopic mechanism is used for the head rest as well.
PROS: Adaptable, Less Bulky Than Concept 1
CONS: Multiple Parts, Still Not Easily Transportable
Concept 3 shares some similarities to other concepts such as the post holder, straps, and overall seat design. The main focus for this design was portability. The backrest will be able to pivot so that it can collapse. The arm rest will have to be shifted to the outside. Just like in concept 2, the head and foot rests are adjustable and detachable. The pivot will feature a pawl and ratchet in order to lock it in place and a switch to lock and unlock it. While it is not shown in the picture, we did discuss having some sort of bag that the chair could be put so it will be easier to carry.
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Cons:
For our final design, we’ve decided to adapt Concept Design 1, removing and adding a few things to make it more functional in many different scenarios. This would increase it’s portability ranking on our decision matrix, as well as allowing for more user control in our final product.
Our selected design takes heavy inspiration from our 1st concept design, as the rigid quality is perfect for our intentions. However, the first design was flawed, as its bulkiness caused a variety of problems and many scenarios in which it would be unusable. To overcome this, we have decided to remove the big, unmovable footrest. This allows for a lot of needed versatility. We have also scrapped the adjustable headrest, as our planned support structure would not accommodate it. We finally plan on modifying a Tomato Chair, to create our desired support structure.
Our design contains three major parts:
1. Chair: In order to achieve our desired support structure, we will purchase and modify a Tomato Chair. This chair naturally has great upper body support, as well as lightweight maneuverability. We intend on adding a Velcro headband to achieve the desired head support.
2. Base: In order to achieve the upright posture of the seat, we have decided to purchase a plastic chair to use as a base for the tomato chair, allowing us to add some additional amenities to the chair.
3. Amenities: There are a variety of additional features we would like to add to the base, such as an IV pole holder, mobile hanger, legs, etc. We plan on making most of these parts detachable, so the user can choose what parts they want to use at any given time. These parts will either be purchased separately and made detachable through screws (legs) or be 3D printed with a polypropylene filament, and attached via adhesive or a removable latch system.
The first picture is a von Mises stress analysis of the mobile hanger. The applied force is 10 lbf applied at the curved hanger end, which is heavier than any object that will be on the hanger. The areas that experience the highest stresses are the curved hanger end, and the base. However, the stresses are not high enough to cause any breaks in the material.
The second picture is a URES Resultant Displacement analysis of the mobile hanger. The applied force is still 10 lbf. The force would cause a slight deformation in the material over time; however, since the deformation is only 1.232 mm, it is not a problem.
This the simulated displacement of the chair with the current weight of the child (27lb) on the chair. The maximum displacement is only 0.002625 in. which is at the top of the backrest. This would be counteracted while the child is leaning back.
Our third analysis focuses on the IV pole holder. For this analysis, we assume that the IV pole does not slip, and that the shear force is uniform along the side of the pole.
We first calculate the shear force that will be experienced at any point along the pole. Then, we calculate our stress that force causes on the pole. We use an applied force of 100 lbs, pole holder length of 1 in, and pole diameter of 1.5 in for this analysis.
Most of our testing was done on the Tomato Chair straps and the armrests. We wanted to make sure the chest and head supports would stay strong when pushed or pulled at various different angles. We also ensured that the armrests would not break under any pressure that a child would be able to apply.
For safe use, please follow the following instructions:
Overall this project was a success. The chair provides ample head and chest support, all while keeping an upright posture. We are proud of the fact that we were able to achieve this, and with relative ease. However, there were a few shortcomings. We had a few amenities that we wanted to include in the final product, but were unable to for various reasons such as scope creep, 3-D printing problems, and/or time restrictions. We were able to include the things that we believed would be the most essential and overall useful. We would like to say thank you to Dr. Stephen Canfield, Mr. Chris Mills, and Mr. Jeff Randolph for your help and generosity throughout the semester.
