Auto-Locking Consumer Safety Mechanism

Passive auto-locking retractable dog leash mechanism designed to improve safety during sudden lunging or acceleration.

Overview

Designed a passive auto-locking mechanism for a retractable dog leash to improve safety when a dog suddenly lunges or accelerates. The system used a ratchet wheel, slide block, bearing, roller, and spring mechanism to trigger automatic locking before the user could manually react. The project included concept generation, decision-matrix evaluation, component selection, design-for-manufacturing comparison, finite element analysis, and prototype testing.

Prototype overview and exploded assembly view showing the passive auto-locking leash architecture and its key internal components.

Recognition

This senior design project was recognized as an Honorable Mention at the 28th Annual UIC Engineering Senior Design Expo. The expo featured more than 130 engineering projects presented by over 500 students across the UIC College of Engineering.

Skills Demonstrated

Mechanism Design CAD Product Design Decision Matrix DFM FEA Prototyping Component Selection Mechanical Testing

My Role

Mechanical design, concept evaluation, CAD modeling, component selection, finite element analysis, prototyping, and testing.

Engineering Highlights

  • Developed and compared four mechanical locking concepts using a weighted decision matrix.
  • Selected and refined a ratchet-wheel-based locking mechanism for passive auto-locking.
  • Designed the mechanism around a spring-loaded slide block, bearing, roller, and ratchet assembly.
  • Performed finite element analysis to evaluate structural strength, achieving a reported safety factor of 5.0372.
  • Compared 3D printing and injection molding approaches for prototyping and scalable manufacturing.
  • Built and tested a functional prototype that successfully demonstrated auto-locking, retraction, and manual locking functions.
Four candidate passive locking concepts explored during concept generation, including roller, wedge, bearing, and lever-triggered locking approaches.
Weighted decision matrix used to compare concepts across size, reliability, safety, cost, service life, and ease of use.
Detailed mechanism view showing the spring-loaded slide block, bearing, roller, and ratchet-wheel engagement geometry.
Finite element analysis used to evaluate deformation and structural safety margin for the locking component geometry.