Expandable Foam Sheet Locking via Slit-Defined Hinged Arms
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Solution Overview
Problem
Expandable foam sheets struggle to maintain their expanded configuration without external retention, often collapsing back due to lack of sufficient locking pressure, especially in low-density applications where the foam lacks the necessary structural integrity for secure locking.
Innovation Solution
The development of an expandable foam sheet with specific slit configurations, densities, and thicknesses that allow for high locking pressure, where the slit arrangement, shape, and proximity create a strong lock in the expanded configuration, enabling the foam to retain its shape without external support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If low density foam sheet is used to enhance softness and cushioning properties, then cushioning performance is improved, but the foam sheet lacks structural integrity to maintain expanded configuration without external retention
Solution Approach 1:
The foam sheet is divided into multiple unit cells by slits that partition the foam into discrete expandable compartments. Each unit cell contains expansion-and-locking arms that can independently pivot and lock, providing distributed structural support across the entire sheet while maintaining low overall density. This segmentation allows the foam to achieve both softness and structural integrity.
Solution Approach 2:
The expansion-and-locking arms are designed to dynamically transition between retracted and extended positions. During expansion, the arms pivot outward and lock into place, transforming the foam from a soft, unexpanded state to a rigid, locked configuration. This dynamic mechanism allows the same low-density material to provide both cushioning softness and expanded structural stability.
2Stability of the object's composition
If external retention means are used to maintain expanded configuration, then expanded configuration stability is improved, but device complexity increases
Solution Approach 1:
The foam sheet contains self-contained expansion-and-locking arms within each unit cell that automatically lock the expanded configuration without requiring external retention mechanisms. The arms pivot and lock based on the expansion force itself, making the system self-sufficient. This eliminates the need for separate adhesives, clips, or rigid supports while maintaining stable expanded configuration.
Solution Approach 2:
The locking function is extracted from external retention mechanisms and integrated directly into the foam structure itself. The expansion-and-locking arms are built into the foam matrix, allowing the foam to lock its own configuration internally. This extraction of the locking function from external systems simplifies the overall device by eliminating separate retention components.
3Stability of the object's composition
If slit arrangement, shape, and size are optimized to achieve high locking pressure, then expanded configuration stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes specific parameters of the slits and expansion arms, including slit width (0.5-2.0 mm), slit length (10-50 mm), and arm dimensions, to achieve the desired locking pressure. By carefully controlling these geometric parameters during manufacturing, the foam achieves high locking pressure while maintaining feasible manufacturing tolerances for standard production processes.
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 foam sheet effectively locks into an expanded configuration with high pressure-to-close, providing enhanced cushioning properties and stability, suitable for packaging and other applications without the need for additional retention methods.
Implementation Method 1
Expandable foam sheet made from thermoplastic foam such as polyethylene foam exhibits elastic character during expansion. That is, as force is applied to expand the foam sheet in one or more dimensions, the foam sheet exhibits an elastic restorative force that, unless opposed, results in the foam sheet returning to its unexpanded configuration.
Implementation Method 2
Each of the unit cells comprises a pair of expansion-and-locking arms hingedly connected at opposite ends to fingers extending from adjacent stabilization walls and hingedly connected at their midpoints to one another
Data Source
Figure 1
Figure 1A
Figure 1B
AI summary
A mechanically expandable foam sheet has comprising a plurality of discrete slits therein that allow the foam sheet to be expanded from an unexpanded foam sheet configuration to an expanded foam sheet configuration. The expandable foam sheet has a density of from 14 g/liter to 48 g/liter in the unexpanded configuration and a thickness of from 6 mm to 50 mm. The slits are of a kind and of a size and arrangement that the expanded foam sheet locks into the expanded configuration by exhibiting a pressure-to-close of at least 5 gm/cm2. Each of the slits provides only a single free volume in the expanded foam sheet. An expandable foam sheet having serpentine-shaped expansion and locking arms is also disclosed, as are various cushioning articles comprising expanded foam sheet.