Flexible Bottom Bar for Roll-Up Door Wind Resistance
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Solution Overview
Problem
Overhead roll-up doors face challenges in resisting high wind loads and maintaining breakaway ability from guided paths when impacted, with existing solutions often requiring frequent replacement of components due to the inverse flexibility and rigidity issues of bottom bars and tabs.
Innovation Solution
A door assembly with a stiffened bottom bar and bottom bar guides that engage the bottom bar to enhance wind load resistance and facilitate disengagement from side columns, featuring a configuration where the bottom bar guides are attached to the opening's lower boundary or side columns, with angled faces and end tabs to manage wind pressure and impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flexible tabs are used on the bottom bar to engage side columns, then the door can disengage from side columns upon impact, but the door loses wind load resistance capability
Solution Approach 1:
The bottom bar is designed with dynamic characteristics, being flexible enough to allow disengagement from side columns during impact events while maintaining engagement during normal operation. The flexibility enables the bottom bar to bend and release from the rigid stop, providing breakaway capability without requiring separate flexible tabs that would compromise wind resistance.
Solution Approach 2:
The invention changes the flexibility parameter of the bottom bar itself, making the entire bottom bar flexible rather than adding separate flexible tabs. This parameter change allows the bottom bar to maintain engagement with side columns under wind load while automatically disengaging when impacted, resolving the contradiction between wind resistance and breakaway ability.
2Strength
If rigid tabs are used on the bottom bar to engage side columns, then the door maintains wind load resistance, but the door cannot disengage from side columns upon impact
Solution Approach 1:
The bottom bar transitions from a static rigid structure to a dynamic flexible structure that can adapt its state based on loading conditions. During normal operation, it maintains a rigid-like engagement with side columns for wind resistance. Upon impact, it becomes flexible enough to disengage, providing the needed breakaway capability.
Solution Approach 2:
The flexibility parameter of the bottom bar is optimized to provide sufficient rigidity for wind load resistance while maintaining enough flexibility for impact disengagement. This parameter optimization eliminates the need for separate rigid and flexible components, resolving the contradiction between maintaining engagement and enabling breakaway.
3Strength
If the bottom bar extends close to or between side columns to enhance engagement, then wind load resistance improves, but the complexity of ensuring proper engagement and disengagement increases
Solution Approach 1:
The invention extracts the engagement mechanism from a complex multi-component system (separate tabs, rigid stops, flexible elements) and simplifies it to a single flexible bottom bar. The bottom bar itself provides both the engagement function and the disengagement capability through its flexibility, eliminating the need for additional engagement mechanisms.
Solution Approach 2:
The flexible bottom bar serves multiple functions simultaneously: it provides structural support for wind load resistance, engages with side columns during normal operation, and automatically disengages upon impact. This multi-functionality in a single component reduces device complexity while maintaining effectiveness.
Data Source
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AI summary
A door assembly having a flexible door panel wound and unwound on a drum or the like to selectively block or permit access through an opening, the flexible door panel having a stiffness, a width, and a length. The door assembly further includes vertically extending side columns disposed on opposite sides of the opening, the side columns being configured to engage a marginal edge of the flexible panel to vertically guide the panel while opening or closing. Attached to a leading edge of the door panel is a bottom bar having a greater stiffness than the door panel and a narrower width than a distance between the vertical panel guide assemblies. Bottom bar guides are disposed proximate a lower portion of the opening and are configured to engage a portion of the bottom bar only when the bottom bar is located in at least a partially closed position.