Manual Wheelchair Storage System

James (YongJae) Chang, Jake Esselman, Ryan Raubolt, Matthias Beurer (University of Wisconsin-Madison)

ABSTRACT

The problem of storing and accessing personal belongings while using a manual wheelchair is surprisingly unknown to individuals who don’t use a manual wheelchair, but is an everyday frustration for wheelchair users.  The common solution of hanging a backpack over the backrest of the chair is problematic because issues such as the difficulty in accessing the backpack when seated in the chair arise.  Similarly, the lack of a horizontal surface on which to place items while maneuvering a chair is a problem user’s face while performing many everyday activities.  In light of this, a system for easy storage and access of items was designed which incorporates spaces for both often needed items, such as a cell phone or wallet, and larger items, such as a laptop or books.  A foldable work surface was also designed offering the user a compact, lightweight surface that quickly attaches and detaches from the chair.

STATEMENT OF PROBLEM

The problem of storage is well known to most wheelchair users.  Even in many of the modern advanced and ultra-light wheelchairs, little thought seems to have been given to incorporating storage solutions into chair design.  Rather, this challenge was left up to the user to solve themselves.

One common storage solution adopted by many wheelchair users is hanging a backpack over the backrest of the chair.  While this method provides an affordable and widely available solution, the weight of the backpack hanging on the chair can damage the wheelchair’s backrest and padding material.  The backpack also has a tendency to swing while maneuvering, causing the chair to become imbalanced.  A third problem encountered using the backpack is a difficulty in accessing its contents.  It is very difficult for many users to reach behind and find the desired item because they are unable to see behind them.  Accessing its contents usually requires removing the backpack from the chair and bringing it around front, but lifting the pack while removing the straps is difficult to do.  As an example, some users will lift the straps off of the backrest, let the backpack drop to the ground and then turn the wheelchair around to pick it up.  There is no good way to remove the backpack and putting it back is nearly impossible without assistance from someone else.

Another common problem experienced by manual wheelchair users is the lack of a flat surface on which to place items during everyday use.  Activities such as washing laundry, eating meals, and shopping are more difficult without a stable surface on which to set items while moving in a wheelchair.  Items are often placed in the lap of the wheelchair user, but can slip off easily and may be difficult to pick up again.  There are attachable surfaces available on the market, but most are bulky, heavy, and cannot be easily removed when not in use.
Research was conducted showing the activities of daily living and these activities, listed in Table 1, include dressing, laundry, managing medications and shopping. These activities can be challenging to wheelchair users and with the Manual Wheelchair Storage System (MWSS), these daily tasks can become easier. When the user must leave the house to go shopping at the grocery store, the upper storage system can be used to store keys, cell phone or wallet while the work surface can be used to hold a basket for the user to place items. Also when leaving the store, depending on how many items the user purchased, they can go in the lower storage unit. This is just one example of how this new system can make the tasks that arise in daily living easier for wheelchair users.

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Table 1: Activities of Daily Living and the issues manual wheelchair users face. The Manual Wheelchair Storage System can help to make these daily tasks easier on the wheelchair users.

Reference: www.pbs.org/wgbh/caringforyourparents/…/cfyp_adl_checklist.pdf

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OBJECTIVE

The goal of this project was to create a storage system and attachable work surface for users of manual wheelchairs.

METHOD

Members of the Madison Spinal Cord Injury (MSCI) group were consulted about their personal storage needs on their wheelchairs.  A set of design constraints was developed based on suggestions from group members.  These constraints were:

1. The devices should be lightweight and secure.
2. The devices should stay within the profile of the chair.
3. Attachment/Detachment would be quick and easy with little modification to the wheelchair.
4. The devices should be accessible while sitting in the chair.

It was also determined that there was a great desire for a work surface to assist in daily tasks.  The work surface would need to be lightweight, sturdy, and easily attach/detach to the wheelchair.  Also, the work surface should not interfere with user transfers to and from the wheelchair.

After the initial meeting, prototypes were developed and then evaluated by members of the Madison SCI group.

RESULTS

To begin, a Universal Attachment Frame (UAF) was developed and attached to the chair as shown in Figure 1 to allow for storage on the wheelchair. The UAF consists of two one-inch diameter aluminum tubes running parallel to the backrest tubes.  They were attached at the top by a bracket with expanding quills that are inserted into the tops of the tubes.

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Picture 2 - Lower Storage System. From left to right starting at the top: 1) The first prototype for the UAF design. 2) The final UAF design consisting of guide rails for the plastic knob to slide. 3) The UAF next to the pannier bag to show how the different elements lock into place. 4) The user reaching for the pannier bag. 5) The user removing the pannier bag from the UAF.

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After discussing with users their storage needs and wants, items needed to be stored were categorized into two types: smaller items such as keys or a wallet, and larger items such as books or a laptop.  From these, two different types of storage were developed.  To accommodate the smaller items that would be used with more frequency, two small baskets were designed to sit behind the shoulders of the user. The baskets are attached to a bracket that is able to rotate 90 degrees, locking into two positions, opened and closed. The bracket is also mounted onto a rail system that allows the basket to slide out towards the user to allow for easier access. When the baskets are in the storage (closed) position they are folded back against the seat of the chair and when they are swung out they are parallel to the wheels on the chair. These baskets provide easy access to smaller items like a pen, keys, or a wallet.  The baskets are locked into position by four spring plungers screwed into the bottom bracket that attaches to the main storage frame. The spring plungers are mounted in a circle where they are all 90 degrees apart from each other. The upper bracket that is attached to the basket and runs along the rail system has small divots in it in the same positions as the spring plungers so the balls on spring plungers will lock into place. The two brackets are held together by a pushpin that will allow for easy removal of the upper storage system. The first iterations of this design were created using magnets to hold the baskets in the open and closed positions. It was found that even when using strong neodymium magnets, the magnets were not strong enough to keep the baskets in place during normal use of the wheelchair. It was decided that a mechanical method was needed to keep the baskets in place. The method what was decided on was using the spring plungers. The spring plungers provide enough force to keep the baskets in place yet still allow the basket to rotate easily. In the final iteration of the design of the upper storage baskets, they will be fully enclosed with a canvas-like fabric that would provide security for the user. The fabric will have an easy opening enclosure such as Velcro so the user can easily open the baskets.

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Picture 1 - Upper Storage Baskets. From left to right starting at the top: 1). The first two prototypes for the attachment bracket. 2). Final prototype with basket attached on the UAF. 3). Close up of spring plungers on bottom bracket. 4). Close up of underside of upper bracket with pin attached. The small divots allow the balls on the spring plungers to lock into place. 5). Upper storage baskets in the closed position. 6). Upper storage baskets with one in the active (open) position.

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The lower storage consists of a pannier bag that attaches to two 3/8-inch diameter crossbars that are attached to the frame.  The crossbars are designed to accommodate many different types of pannier bags so the user is able to select the one they want. A Novara Safari pannier bag was used for the prototype because it has a locking system with a push button allowing the pannier bag to lock on the upper crossbar. A plastic knob was attached to the pannier bag near the bottom to grab hold of the lower crossbar preventing the pannier bag from swinging while the wheelchair is in motion. Also, two guide railings are attached vertically to easily guide the plastic knob to the lower crossbar when the user is putting the storage device away as shown in figure 3.

The initial portable work surface was made of two square sheets of polyethylene board connected on the sides by a piano hinge allowing it to fold down the center.  90 degree aluminum bars with slots cut the entire length of them were bolted to the underside of the surface to serve as guides for the fold down legs.  The legs of the work surface were attached to the wheelchair frame using AB-59480 wheelchair clamps and could be adjusted for different wheelchair widths.

Once the prototype was completed it was brought to the Madison SCI group for evaluation.  It was determined that the work surface needed to be lighter and it would be useful to be able to adjust the height.

The second prototype of the work surface used polycarbonate board instead of polyethylene board, greatly reduced the weight.  Strips of the polycarbonate board were stacked on the edges and used as guides for the work surface legs instead of the aluminum, also reducing the weight. Other benefits this prototype focused on was the height adjustability using telescoping bars and transparent polycarbonate board for the user to see where they are going when the work surface is in place. This prototype again was evaluated by peers and the Madison SCI group and it was determined that the legs “flopped” around when trying to deploy or put away the work surface, height adjustment was complicated, and the attachment for the table on the chair was not secure.

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Picture 3 – Evolution of Design for the Portable Work Surface Prototypes going from left to right starting at the top: 1) An exploded view of the work surface including the polyethylene pin, the polyethylene board support and the polycarbonate table. 2) The bayonet style mounting system for the Manfrotto arm. 3) The first prototype which was a full table made of polycarbonate, aluminum, and steel. 4 & 5) This was the second prototype was also a full table adding aluminum guide rails for the legs and a polyethylene surface. 6) This was the third prototype created made out of aluminum and polycarbonate, allowing for a much lighter design.

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DISCUSSION

The final design consists of five major components: the UAF, the lower storage unit, the upper storage unit, the mount for the work surface and the work surface itself.

Finalizing the design of the lower storage was a difficult decision.  There were two options being weighed:  a compartment that rotates out from the back of the chair, or a pannier bag that detaches and is lifted around the wheelchair.  After much debate, it was decided that the second option would be more practical and less complicated.  Having a compartment that rotates out from the back of the wheelchair could cause tipping concerns because it changes the center of mass of the wheelchair.  It also required a complicated mechanism for actuation.  In contrast, the pannier bag system is able to attach easily and securely using the UAF developed.

Using the QFD process, a third work surface design concept was developed. This concept would utilize the user feedback received taking into account being lightweight, easy deployment, being compact for storage capabilities and eliminating one leg. This prototype was made of polycarbonate (PC) and polyethylene (PE) board. The PC board was divided into five slats (Four 2” slats and one 4” slat) and covered with Super 22 material. These slats are designed to rotate around a pin in the center and fold up within the frame of the of the PE board (4” width). The table rests on a mechanical arm manufactured by Manfrotto and the arm rotates on three ball bearings. These ball bearings allow the user to place the table at any comfortable position and by activating the lever on the arm, the ball bearings lock into place. To stabilize this arm, a bayonet clamp system was used. The pin is connected to the Manfrotto arm and pushes through a mount. Once the pin is in and the user rotates it 90 degrees, they can pull up and lock the pin into place with a threaded handle. When the work surface is not in use, it is placed in the lower storage unit, still leaving room for a laptop or other important items.

Finally, the evaluation with the Madison SCI group provided future considerations for the design: add handles to the chair, try different sizes of upper storage baskets, consider storage underneath the chair, and tie in arm rests to the design.

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The Final Prototype with all 3 devices attached

Design of Personal Storage System and Work Surface for Manual Wheelchairs

James (YongJae) Chang, Jake Esselman, Ryan Raubolt, Matthias Beurer

Past Semester Members: Jared Kann and Matt Carlson

ARTe Design, 3053 ME,

1513 University Ave, Madison, WI 53706

(612)849-9251, jtesselman@wisc.edu