Mail Feeder Stripper With Variable Stiffness Leaf Springs
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Solution Overview
Problem
Existing mail sorting systems face issues with slow response time and improper damping in strippers, leading to frequent doubles and damage to mail pieces due to rigid links and normal spring forces, causing noise and misfeeds.
Innovation Solution
A stripper with a flexible backing sheet and leaf springs that apply resilient force outwardly, providing variable stiffness and critical damping to ensure smooth singulation of mail pieces, preventing flapping and misfeeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If rigid links and normal spring forces are used in the stripper, then the stripper can apply force to mail pieces, but the mail pieces flap, bend and become damaged
Solution Approach 1:
The patent applies a flexible friction shoe cover made of elastomeric material over the stripper friction surface. This flexible cover conforms to the mail piece surface and distributes the stripping force across a larger area, preventing localized stress concentrations that would cause mail pieces to flap, bend, or become damaged while still providing effective singulation.
2Force
If normal spring forces are used in the stripper, then the stripper can engage mail pieces, but large impact and displacement of friction shoes causes noise
Solution Approach 1:
The patent employs elastomeric friction shoe covers that provide cushioning before impact occurs. The compliant material absorbs impact energy through deformation, reducing the shock and displacement of the friction shoes during mail piece engagement, thereby significantly reducing noise generation while maintaining effective stripping action.
3Ease of manufacture
If rigid mounting brackets are used to position friction shoes, then the friction surface location can be adjusted, but the response time is slow and damping is improper
Solution Approach 1:
The patent changes the physical parameters of the friction surface by using elastomeric material with specific durometer ratings (e.g., 40-70 Shore A). This material provides both the necessary friction characteristics for effective stripping and the compliance needed for rapid response and proper damping, eliminating the slow response time associated with rigid mounting systems while maintaining adjustable positioning capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The stripper effectively reduces noise and misfeeds by applying lateral drag forces, ensuring proper singulation and preventing damage to mail pieces, with performance independent of mail properties.
Implementation Method 1
a friction shoe including a leaf spring disposed beneath the backing sheet such that external pressure against the friction surface results in resilient bending of the spring such that force is exerted outwardly against the backing by the spring
Implementation Method 2
The stripper has a flexible backing sheet having an outwardly exposed friction surface for applying friction to a face of a passing mail piece
Data Source
AI summary
A stripper of the invention uses flat metal springs (leaf springs) preferably made of spring steel and a flexible polymer based friction material covering the springs on one side so that the friction material contacts an incoming mail piece passing by the stripper along the friction surface presented by the outside of the friction material. A stripper according to the invention has variable stiffness, is quick responding, and is critically damped, meaning that incoming mail pieces will not bounce off it with excessive force likely to cause a misfeed or loss of control of the mail piece.