Battery Door Design

Project Overview

Exploration of new battery door latching mechanism as modification to iPod classic architecture. I benchmarked existing products, conducted hand calculations, CADed the chosen design, recommended validation processes, and created a BOM with manufacturing requirements.

Project Duration

1 week

Skills

Solidworks, benchmarking, free body diagrams, BOM, design process, DFM, DFA

Given Design Requirements

User may only apply downward, normal force
Design includes door, release button, and door latching features that house and cover 2 AA batteries

I referenced additional sources to expand on the provided design requirements.

Constraints

5N force required to push button
Minimize design complexity
Button should be easy to locate and press (10 x 10 mm2 button area)
User applied downward force
Mechanism allows for easy battery removal
Button is within door outline
Sleek design (minimal external change aside from adding button)

Assumptions

Design for 2mm button displacement, with button flush with lid surface at maximum height
Using iPod classic dimensions, with modified height to accommodate for batteries

10 mm minimum diameter and 2mm displacement for push buttons, as recommended by Human-System Interface Guidelines from the US DOE

Reasoning to accommodate for larger actuation force than mechanically necessary, as quoted from research paper "Neuromechanics of a Button Press"

Benchmarking

Canon Camera

Common Characteristics in Benchmarked Mechanisms

Minimal parts
One-handed operation
Hinge (or another way to keep the lid attached even when unlocked)
Two stage motion often helps prevent accidental opening

Push-Push Mechanism

Chosen Design

Spring-Loaded Sliding Latch

The user unlocks the lid by pressing down on the button (1), which compresses the spring (5) and forces the latch (2) to move along the slanted part of the button. Once the rounded edge of the latch meets the leftmost corner of the flange (3), it moves along the slanted part of the flange, allowing the lid to rotate open via the hinge pin (7).

To lock, the user presses on the lid, during which the latch follows the same path, except in reverse, and is constrained by the lip on the bottom edge of the button and the inner corner of the flange.

*Latch and button housing not shown*

*Batteries and battery holder not shown in BOM*

Spring Tuning Technical Calculations

Latch FBD

Button FBD

Recommended Simulation and Validation Processes

Thermal: Verify mechanism works as intended under 0-35° C (iPod standard operating temperature)

HTHH (High temperature high humidity): Test for environmental effects (e.g. moisture and temperature) on latching performance
Vibration: Ensure components stay in place and that lid does not pop open with vibration, simulating product transportation
Dust and Ingress testing: Ensure excessive debris does not accumulate and impair mechanism motion
Cycling: Withstand 1000 cycles of latching/unlatching (based on AA battery lives and iPod life) without damage or wear
Drop test: Verify mechanism works as intended when dropped from 4 ft (around waist height)

Future User Experience Recommendations

Door-Enclosure Flushness

Lip on button and inner surface of flange controls bottommost latch position
Add ledge on button slanted surface to control topmost latch position
Control flatness and parallelism between button lip, latch, and inner flange surface

Click Feel

Tune spring preload to spring door open but not bias outwards when locked
Low friction pairing (nylon to steel) allows for smooth motion
Perform click feel testing to determine ideal click ratio and feel

Aesthetics

Reverse screw direction (screw head on inside of door)
Bead blast/anodize surfaces to control texture and color
Partially recess button within door outline to provide visual cue

Page updated

Google Sites

Report abuse