L-Shaped Lug Child-Resistant Closure Friction Reduction
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Solution Overview
Problem
Existing child-resistant closures with inner and outer plastic shells require precise axial force and rotation to engage lugs effectively, which can be cumbersome and may not prevent accidental opening by children due to potential misalignment or insufficient force application.
Innovation Solution
The design incorporates L-shaped internal lugs on the outer shell and angularly spaced external lugs on the inner shell with rounded surfaces for reduced friction and improved alignment, allowing for easier application and removal by ensuring line or surface contact between lug faces, thus preventing accidental rotation without sufficient axial force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer shell is pushed axially against the inner shell and rotated to engage lugs, then the closure can be removed from the container, but the operation becomes cumbersome and may not prevent accidental opening by children
Solution Approach 1:
The patent applies curvature by providing rounded radially inwardly facing surfaces on the second portions of the L-shaped lugs. This curvature reduces sliding friction between the lugs during rotation, enabling smoother and easier removal of the closure while maintaining the mechanical interlocking mechanism that prevents accidental opening by children.
2Ease of manufacture
If the lugs have flat surfaces for engagement, then the manufacturing is simpler, but the sliding friction during rotation increases making the operation more difficult
Solution Approach 1:
The patent applies local quality by providing rounded surfaces only on the specific portions of the lugs that contact each other during rotation (the radially inwardly facing surfaces of the second portions). The rest of the lug structures maintain their simple geometric forms for easy manufacturing. This localized curvature reduces friction where needed while keeping overall manufacturing simple.
3Strength
If the central portions of the shell base walls are made thicker for strength, then the structural integrity is improved, but the weight and manufacturing cost increase
Solution Approach 1:
The patent applies local quality by providing different thicknesses in different portions of the shell base walls. The peripheral portions maintain sufficient thickness for structural strength and lug support, while the central portions are made thinner to reduce weight and manufacturing cost. This differential thickness design optimizes the strength-to-weight ratio of the closure.
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
This design enhances the user experience by simplifying the opening process while maintaining child-resistance by ensuring that the lugs engage properly only with sufficient force, reducing the weight and cost of the closure through thinner central shell portions without compromising strength.
Implementation Method 1
The second portions of the L-shaped lugs preferably have rounded radially inwardly facing surfaces for reduced sliding friction with the skirt of the inner shell
Implementation Method 2
The internal lugs on the outer shell and the external lugs on the inner shell have opposed rounded axially facing surfaces such that the internal lugs on the outer shell cannot rest on the external lugs of the inner shell upon application of force to the outer shell
Data Source
Figure 1~4
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Figure 9~11
AI summary
A child-resistant closure includes a plastic inner shell (42) having a base wall (64) with a peripheral skirt (66), at least one internal thread segment (68) on the peripheral skirt and a plurality of internal lugs (74) on the base wall adjacent to the skirt. A plastic outer shell (44) has a base wall (46) with a peripheral skirt (48) and a plurality of internal L-shaped lugs (54) at a juncture of the base wall and the peripheral skirt. Each of the L-shaped lugs includes a first portion (56) extending radially inwardly along an undersurface of the base wall of the outer shell for engaging the external lugs on the inner shell, and a second portion (58) extending axially along an inner surface of the peripheral skirt of the outer shell for slidably engaging the inner shell and aligning the inner shell within the outer shell. The second portions of the L-shaped lugs preferably have rounded radially inwardly facing surfaces (62) for reduced sliding friction with the skirt of the inner shell.