Elastomeric Mold Coating for Lightweight Pulp Coffin
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Solution Overview
Problem
Existing pulp molding methods struggle to produce large, lightweight coffins with uniform strength and smooth surfaces due to thermal expansion and contraction of metal mold halves, leading to compromised strength and surface quality.
Innovation Solution
A large lightweight molded coffin design featuring an outer shell of molded pulp with a core reinforcing spacer material, such as Re-board or paper honeycomb, and an inner shell made of molded pulp, using elastomeric-coated mold halves to absorb dimensional variations and ensure even drying under pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal mold halves are used for compression molding, then the structural strength and durability of the mold are improved, but thermal expansion and contraction cause dimensional instability and surface unevenness in the finished product
Solution Approach 1:
An elastomeric material layer is introduced as an intermediary between the rigid metal mold half and the pulp material. This elastomeric layer absorbs thermal expansion and contraction of the metal mold, preventing dimensional instability and surface unevenness while allowing the metal mold to maintain its structural strength
Solution Approach 2:
The invention changes the physical state and properties of the mold surface by coating it with elastomeric material. This creates a compliant surface that can deform elastically to compensate for thermal effects, transforming the rigid metal surface into a dynamically adaptable molding surface
2Weight of moving object
If pulp molding is used to create large containers, then the lightweight and cost-effective advantages are achieved, but uniform strength and smooth surface finish become difficult to obtain
Solution Approach 1:
The elastomeric coating acts as a mediator that ensures uniform pressure distribution across the large pulp mold surface, preventing weak spots and surface defects while maintaining the lightweight nature of the pulp-based coffin
Solution Approach 2:
The elastomeric material is pre-applied to the mold surface before molding, creating a prepared interface that will compensate for thermal effects during the molding process, ensuring consistent quality from the start
3Strength
If integral ribs are added for reinforcement, then the structural strength is improved, but the smooth surface and classic coffin shape are compromised
Solution Approach 1:
The solution nests multiple functional layers within the coffin structure: an outer smooth aesthetic layer, an intermediate reinforcing layer with ribs, and an inner functional layer. This allows the strength-providing ribs to be hidden within the structure while the outer surface maintains its smooth, classic appearance
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 solution enables the production of strong, smooth, and lightweight coffins with improved dimensional stability and surface finish, reducing manufacturing complexity and reject rates while maintaining cost-effectiveness.
Implementation Method 1
The mold half is covered with an elastomeric material which has proved to absorb dimensional variations in the mold half, thereby compensating for any thermal expansion or contraction
Implementation Method 2
a wire mesh is then laid in multiple layers which will further contribute to distributing the vacuum forces more evenly
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
A large lightweight molded coffin comprises a large pulp molded outer shell (17) lined with a reinforcing spacer material(18)such as single faced ReBoardTM, a honeycomb structure or a molded spacer material conforming to and adhering to said shell and an inner shell(19)made of molded pulp or a paper based material. A method for manufacturing such a lightweight coffin involves pressing slurried pulp between a first male mold half (5) covered with elastomeric material (6) and a second female mold half (3), to form the molded pulp shell (17),and gluing the reinforcing spacer (18) material to the interior of said outer molded pulp shell (17)and the inner shell.