Mobile for Children at Duke Hospital

Designers: Charles E. Wells
Client Coordinators: Michelle Ashford
Supervising Professor: Dr. Larry N. Bohs

The Child & Adolescent Life Program (CALP) at Duke Hospital has been unable to find a safe commercial mobile for use with infants. Several mobiles have been tried, but either the hospital safety department has declared them unsafe or the manufacturer has recalled them due to safety issues. The goal of this project was to design and build a mobile that met hospital requirements. A custom mobile was constructed by modifying a commercial mobile designed for home cribs. This mobile mounts securely on a variety of hospital cribs, and has a removable gooseneck arm with a locking hook on the end, allowing a variety of objects to be attached.

How this project helped
The mobile is currently being used at Duke Hospital. Given that no other mobiles are approved, the device is receiving constant use. Hospital staff members are pleased with its features and performance, and have asked for five more units to be constructed. Michelle Ashford, director of CALP, said “We have used the mobile and it has been great. It is secure and the stand itself was great. Having (only) one has been challenging for us because we want to share it with every infant patient and there are lots of infants in right now.”

Initial research identified a commercial mobile, made by Tiny Love, that met the hospital staff’s requests for music, and contained a removable fixed arm. The commercial base (Figure 2, left panel) was adapted so that it would attach securely to pediatric crib rails by attaching a 3mm diameter round aluminum plate to the plastic wing-nut, providing a stronger and more extensive rail attachment (Figure 2, right panel).

The fixed plastic arm of the commercial mobile was replaced with a flexible metal gooseneck. The mobile base had a round 22 mm opening, 50 mm deep, to accommodate the plastic arm. A 10″ straight aluminum rod was machined to insert securely into this opening; the other end of the rod was threaded to attach to a commercial 19″ microphone stand gooseneck. The length of the fixed rod limited the distance the gooseneck could extend down in the crib, thus ensuring it could not contact a child. A strain relief was designed to prevent the plastic base from breaking due to stress from the cantilevered arm. The strain relief was milled from two aluminum sections that sandwiched the plastic hanging flange (Figure 2, left panel). When screwed together, the two sections contained a round opening through which the fixed rod inserted.

To secure the fixed rod, a spring plunger was added to the strain relief (Figure 2, left panel). This plunger engaged into a hole in the fixed rod for security, but also allowed the arm to be easily removed.

A spring hook was attached to the gooseneck end of the flexible arm, allowing appropriate commercial toys or mobile ends to be securely attached. For the prototype, a commercial plastic X-shaped hanger was attached to the hook, and washable plastic toys hung from its ends.

Finally, a blue rubber hose with an inside diameter of ¾” was slid over the metal gooseneck to provide a slick, colorful covering that was easy to clean. All sharp edges were carefully filed, and all machined components coated with spray-on protective Plasti-Dip.

The prototype mobile has one large on/off switch, three large musical buttons on the front, a speaker, and volume control that are easily accessible. The buttons and switches can be actuated with very little force. The final product is durable enough to withstand forceful movements of the arm, excessive tightening of the wing nut and heavy items being placed on the arm hook.

The cost of parts was about $106, including the commercial mobile base.

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