Description

Re-designed the device clip adapter to prevent damage and fracture to mobile screen protectors

The clip adaptor allows for attachment of the Inito monitor to the user's mobile phone and align the phone camera with the device lens.

The existing design of the clip established clamping using the top surface of the phone and the bottom edges. Being sensitive to the thickness of the phone, any additional protector on the screen such as a tempered glass would lead to breaking and peeling off of the protector.

Inito Device System

Contributions

Problem definition and first requirements
Research on phone profiles and trends
Cause resolution
Ideation and Concept generation
User experiments on perception and force requirements
Concept reviews, iteration and final design

Identification

Using customer cases and internal evaluation, failure modes were identified as:

Caused by direct-butting of the protector edge with the clip during insertion
Excessive compressive force on the tempered glass corner in assembled condition

Clip

Direct - Butting

Clip

Compressive Loading

Research

Protector Data

Phone Screen Protectors were segregated based on their topological shape. Whereas filleted 2.5D shape seemed to account for the least failure, the most common shape was found to be 2D. Also, for phones with curved screens, there were 3D protectors which followed the screen curves and thus, contact with them would be unavoidable in the given clip profile.

Phone Shapes and Screen Types

Using smartphone sales data in India and the US market, the 50 top selling phones from the 2 previous years were identified.

Shape of the phone cross-sections were analyzed to establish trends and to identify the median phone shape to design for.

Definition of Clamping Force Requirement

Using in-built phone sensors, a jerk and vibration test was carried out to define the engineering requirement for clamping force of the clip on the phone. Through the process of testing with the Inito monitor it is imperative that the alignment of the camera and device lenses remains intact.

As conclusion of this test, a peak acceleration of 4G was defined as the engineering requirement for clip clamp retention.

It was found that the existing design was in line with this requirement considering the interaction between the plastic clip and phone surfaces (metal and glass)

Approach

Based on the phone trends and protector types, there were two major approaches:

Reducing Clamping Force required with the current profile
Changing the clip profile to avoid contact with the screen

Ideation

Reduction in clamping pressure: Friction between the clip and phone needed to be increased which called for introducing a higher friction material between interacting surfaces
New Clip Profile: Clip profile changes were conceived to avoid contacting the phone screen and shifting clip contact over to the top edge instead

Prototyping

Clip prototypes were made using SLS and Polyjet 3D printing to suitably represent actual part characteristics in quick-turn.

Reduced Clamping Force

Concept 1

The existing clip profile was layered with silicone for increased friction

Concept 2

The pen clip profile allowed gradual loading of the phone screen and a larger contact patch

Concept 3

Upper and lower contact were made disjoint and independent for softness

New Contact Profile

The idea of shifting contact on to the top edge brought forward the advantage of having a convex contact surface. This would guarantee (geometrically) that the clip would continue to stay away from the phone on either side of the point of actual contact. Three primary profiles were conceptualized.

Concept 1

Straight angled profile

(Failed to avoid contact with mobile buttons)

Concept 2

Independent Convex Profile

(Provides flexibility in contact faces but made the setup bulkier)

Concept 3

Singular Convex Profile

(Provides reliable contact with a sleek look)

Final Design

The idea of adding silicone was dropped due to higher tooling lead time and product cost. The singular convex concept was selected and finetuned.

A secure wall was added on top to prevent the phone from flexing out of the clip. It was prototyped and tested for different phone shapes successfully avoiding screen protector contact.