Problem: Duracell needed a method to help shoppers intuitively identify the model of their coin cell battery to simplify the purchase of a replacement.
Solution: Invent a ramp and channel system to sort coin cell batteries by dropping a dead battery onto a ramp, where it registers next to the correct model label until it is retrieved by a simple push on the tray.
Design Requirements: Simple to operate, easily read and inexpensive.
Engineering Requirements: Able to discriminate differences in battery thicknesses as little as .008", reliable and durable.
Solution: Use custom engineered springs to keep a diameter-sorting deck in a controlled position under a thickness-sorting gauge plate. Battery diameter is determined by channels of increasing width molded into the rear deck - as a battery rolls down a ramp (A) it will fall into the first channel large enough to receive it. Molded on the inside of the gauge plate ribs of increasing thickness project into the channel. A thin battery will slide past ribs sized for thicker batteries, and be trapped by the ribs designed to register its specific thickness (B). The springs also permit the deck to pushed backwards (C), releasing the battery to slide past any remaining ribs until it can be collected (D).
The original rollout was for 7500 units, requiring mass production manufacturing techniques and limited hand assembly. Battery discrimination required extremely tight molding tolerances. Engineering deliverables included the creation of tooling-ready solid models, control documentation, quality documentation and evaluation / design approval of full scale, functional STL rapid prototypes.
