Assistive Work Chair

Designers: Benjamin Hong
Client Coordinators: Judy Stroupe, Antonia Pedroza
Supervising Professor: Dr. Larry N. Bohs

Our client has autism and is employed in an office setting where she sits in a standard office chair.  The seat is too high for her because she is less than three feet tall.   She currently clambers into the seat, but this is both inconvenient and potentially dangerous.  A device was built which consists of a set of steps that extend and retract from a base under the chair.  This allows the client to step safely and comfortably into her seat.  Retraction of the steps is necessary for aesthetics, unobtrusiveness and safety in a crowded environment. The device couples the extension and retraction of the steps to the rotational swivel of the chair and does not require electrical power.

How this project helped
The assistive work chair has provided a safe and simple method for the client to sit in her chair.  Judy Stroupe, one of the client’s supervisor’s says, “The work chair has made [the client] much more comfortable in her work environment and her production has increased.”  Antonia Pedroza added, “The chair is a dream come true, it is the chair we have been wishing for since the consumer started working at Orange Enterprises. The consumer can now rest her feet and work more comfortably. The fact that this consumer has adjusted to this new chair so easily speaks volumes to the forethought and imagination the student put into the project.”

The assistive work chair is a standard office chair with a mechanically retractable step.  Figure 1 shows the work chair with the steps extended.  The rotation of the seat is coupled with the retraction or extension of the steps.  In its default position, the steps are retracted into the base under the chair.  When the seat is rotated 90 degrees (as in Figure 1), the seat locks into position and the steps extend outward, allowing the user to mount or dismount.

The steps are made of _” solid red oak, which provides a good combination of strength and weight efficiency. The steps weigh approximately 11 lbs. The base is made of plywood because it does not need to withstand any direct stress.  The steps are connected to the base via 24” drawer slides rated for loads of 100 lbs.  The drawer slides have friction-reducing ball bearings that enable the steps to slide in and out under their own weight when tilted.  The slides’ sole connection to the base is by a pivot rod, allowing them to tilt freely up and down about the pivot.  The default position of the slides is back-end tilted down as shown in Figure 2a.  This tilt is maintained by a spring of sufficient strength to pull down the back ends of the slides. When the drawer slides are tilted at this angle, gravity retracts the steps down into the base.

When the user wants to extend the steps, the seat is swivled until it is aligned with the steps as in Figure 1. A torque arm rotates with the seat, which pulls up on the back end of the drawer slides via a rope and pulley. This rope overcomes the counteracting spring force and reverses the tilt of the slides as shown in Figure 2b. Gravity then extends the steps out of the base, allowing the user to step onto or off the chair.  The seat is lightly locked into this position by a cabinet door latch (not pictured) whose spring-loaded jaws clamp onto the torque rod.  This lock prevents the chair from swiveling while the user is mounting or dismounting.

When the steps are no longer needed, the seat is jogged out of its lock and rotated to its original position. This slacks the rope holding up the drawer slides.  The spring is strong enough to force the drawer slides to tilt down again, enabling gravity to retract the steps back into the base.

The cost of parts for the device was $108.

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