Interference-Fit Box Lid Assembly for Secure Hardware-Free Closure
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Solution Overview
Problem
Existing box lids often require latches or hardware for secure closure, which can be cumbersome and may not suit all applications for ease of use.
Innovation Solution
A box lid assembly featuring a rigid outer lid, a compliant interference fastener with ribs, and a rigid inner lid, secured together with the fastener sandwiched between, uses a frictional fit to engage with the box body's interior walls without extending to the corners, allowing easy removal and secure closure without hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a latch or hardware is used to secure the lid, then the lid retention is reliable, but the device complexity and ease of operation deteriorate
Solution Approach 1:
The patent removes traditional latches, hinges, and locking hardware from the box lid assembly. Instead, it uses a simple friction-fit mechanism where the lid's edge region directly engages with the box body's rim, eliminating complex retaining components while maintaining secure closure.
Solution Approach 2:
The lid assembly is designed to self-retain through friction between the rigid outer lid's edge region and the box body's rim. The compliant material in the edge region automatically adjusts to maintain optimal friction contact, providing self-regulating retention without external control mechanisms.
2Ease of operation
If a friction fit is used for lid retention, then the ease of operation improves, but the reliability of lid retention may worsen
Solution Approach 1:
The patent modifies the physical parameters of the lid's edge region by incorporating a compliant material with specific mechanical properties (durometer 20-90 Shore A). This material creates an interference fit that generates sufficient friction force for reliable retention while allowing easy manual insertion and removal.
Solution Approach 2:
The lid assembly uses a composite structure combining a rigid outer lid material (such as molded plastic or metal) with a compliant edge region material (elastomer, rubber, or thermoplastic elastomer). This composite design provides both structural integrity and friction-based retention.
3Reliability
If the interference fastener ribs extend to the corners, then the lid retention improves, but the manufacturing precision and alignment sensitivity worsen
Solution Approach 1:
The interference fastener ribs are designed with localized engagement features that contact specific regions of the box body's interior surface. By concentrating engagement at discrete rib locations rather than requiring full-surface contact, the design reduces sensitivity to overall alignment while maintaining secure retention.
Solution Approach 2:
The ribs extend partially along the interior wall surfaces but do not reach the corners of the box body. This partial extension provides sufficient frictional engagement for reliable retention while avoiding the alignment precision requirements that would result from corner-to-corner engagement.
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
Provides a secure, easy-to-use lid closure mechanism that is resistant to misalignment and does not obstruct the box opening when closed, eliminating the need for undercuts or special hardware.
Implementation Method 1
The compliant interference fastener is secured to the outer lid and has two ribs extending in opposite lateral directions and arranged to engage the interior wall surfaces with the box lid assembly received at the one end of the box body
Implementation Method 2
uses a frictional fit to engage with the box body's interior walls
Data Source
AI summary
A box (10) has a body (12) and a lid assembly (14). The body has walls (18) with interior wall surfaces (20) bounding an interior space (16). The box lid assembly is removable and covers an opening (22) of the box, and includes a rigid outer lid (32) having an edge region positioned to bear against the one end of the box when the box lid assembly is covering the opening, a compliant interference fastener (34) secured to the outer lid and having two ribs (42) arranged to engage the interior wall surfaces, and a rigid inner lid (38) permanently secured to the rigid outer lid with the interference fastener sandwiched between the rigid outer lid and the rigid inner lid. The ribs of the interference fastener are of limited length (L) so as to not extend to the corners of the box body when engaging the interior wall surfaces.