Composite Door Frame Mullion for Moisture-Resistant Rigidity
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Solution Overview
Problem
Existing door frame materials, particularly wood, are prone to decay from moisture and lack durability and rigidity, while alternatives like aluminum and vinyl are expensive or susceptible to deformation.
Innovation Solution
A door assembly with a core made of decay-resistant materials, such as a cellulosic-plastic composite, and a two-piece top piece formed of a composite including wood fiber and thermoplastic, providing structural stability and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wood frame material is used, then the appearance and structural integrity are maintained, but the frame is prone to decay from moisture and lacks durability
Solution Approach 1:
The patent applies composite materials by combining a wood fiber core with a thermoplastic outer layer to create a frame member that resists moisture decay while maintaining wood-like appearance. The composite structure integrates the aesthetic benefits of wood with the durability and moisture resistance of plastic materials, directly resolving the contradiction between appearance and decay resistance.
2Reliability
If aluminum cladded wood frames are used, then decay resistance is improved, but the cost increases significantly
Solution Approach 1:
The patent changes the material parameters by using a thermoplastic outer layer instead of expensive aluminum cladding. This parameter change maintains decay resistance and durability while significantly reducing manufacturing cost, making the frame member more economically viable without sacrificing protective performance.
3Strength
If vinyl film cladded wood frames are used, then appearance is maintained, but impact damage resistance is poor
Solution Approach 1:
The patent uses a composite material structure with a thermoplastic outer layer that provides superior impact resistance compared to vinyl film cladding. The thermoplastic material's inherent toughness and flexibility allow it to absorb impact energy without cracking or peeling, while still maintaining the wood-like appearance desired by consumers.
4Reliability
If all plastic extruded frames are used, then decay resistance is improved, but rigidity and structural stability deteriorate under heat
Solution Approach 1:
The patent employs a composite material design where the wood fiber core provides structural rigidity and dimensional stability that prevents thermal deformation, while the thermoplastic outer layer contributes decay resistance. This synergistic combination resolves the contradiction by ensuring the frame maintains its shape and structural integrity under heat while remaining resistant to moisture decay.
5Reliability
If protective coatings are applied to wood frames, then appearance and basic protection are improved, but moisture wicking from bottom ends still causes decay over time
Solution Approach 1:
The patent uses a composite material structure where the thermoplastic outer layer completely prevents moisture wicking from the bottom ends, eliminating the decay problem that plagues coated wood frames. The non-porous nature of the thermoplastic barrier stops moisture migration at the source, providing superior long-term protection compared to surface coatings alone.
Data Source
AI summary
A door assembly is shown and described herein. The door assembly may include at least one door panel and a door frame having a plurality of frame members including a header and a mullion. The invention may also be considered a frame member. The frame member may be a mullion and include a core; and a two-piece top piece adjoining the core to form a structural member. The door assembly may further include at least one adjacent panel. The inventions disclosed are also applicable to jambs and window structures. Also disclosed are methods and assemblies for a mullion door frame member.