Window Screen Assembly With Tension Equalizer for Sag Control
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Solution Overview
Problem
Horizontally moving screen assemblies face challenges in maintaining a flat appearance due to sagging, as they are unsupported at the bottom edge and experience increasing tension issues when extended, leading to difficulty in operation and potential damage to the screen material.
Innovation Solution
A screen assembly design that incorporates a tension equalizer by cutting or forming the screen material and edge members to provide consistent tension across the screen, using a combination of pulleys and biasing means to maintain uniform tension and prevent sagging, while allowing for easy operation and reduced material stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the screen material is supported only at two vertical edges for horizontally moving screens, then the screen can be easily retracted and operated, but the screen material sags under gravity and loses its flat appearance
Solution Approach 1:
The screen material is divided into multiple longitudinal zones with individual tensioning mechanisms. Each zone can be independently tensioned to counteract sagging while maintaining overall screen flexibility and retraction capability.
Solution Approach 2:
Tension equalizers are pre-installed within the edge members to provide continuous tension to the screen material before operation begins. This preliminary tensioning prevents sagging from occurring in the first place while allowing smooth retraction.
2Shape
If tension is increased to keep the screen material taut and flat, then the flat appearance is improved, but the screen material experiences increased stress and potential damage
Solution Approach 1:
Different longitudinal zones of the screen material are tensioned according to their specific needs. The tension equalizers distribute tension locally across each zone rather than applying uniform high tension across the entire screen, reducing overall material stress while maintaining flat appearance.
Solution Approach 2:
The tensioning system allows dynamic adjustment of tension parameters across different zones. By optimizing tension levels rather than maximizing them, the system maintains screen flatness while preventing excessive stress that could damage the material.
3Area of stationary object
If the screen material is made larger to cover large openings, then the coverage area is improved, but the sagging becomes more pronounced and difficult to control
Solution Approach 1:
Large screen materials are segmented into multiple longitudinal zones, each with its own tension equalizer. This segmentation allows independent control of tension in each zone, enabling effective sagging control across large areas that would be impossible with a single uniform tensioning system.
Solution Approach 2:
Tension equalizers act as intermediary elements between the screen material and the supporting edge members. These intermediaries distribute and equalize tension across the material, enabling large screens to maintain their shape by mediating the forces acting on the extended material.
4Shape
If a weighted bottom rail is used to tension the screen material, then the screen remains taut and flat, but the screen cannot be rolled up about the vertical rod for horizontal movement
Solution Approach 1:
Instead of a single bottom rail, the tensioning function is segmented into multiple longitudinal zones with individual tension equalizers integrated into the edge members. This segmentation eliminates the need for a bottom rail that would prevent rolling, while maintaining tensioning capability across the entire screen width.
Solution Approach 2:
Rather than applying tension from the bottom edge (as with weighted rails), the tensioning system is inverted by integrating tension equalizers into the vertical edge members. This inversion allows the screen to be tensioned from the sides, enabling both taut appearance and horizontal rolling movement.
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 effectively maintains a flat appearance of the screen across large openings by ensuring uniform tension, reducing sagging, and preventing material damage, while allowing for smooth operation and reduced maintenance needs.
Implementation Method 1
a tension equalizer (420) which comprises a biasing means (432). The biasing means is attached to the tension equalizer and is configured to apply a force to the tension equalizer
Implementation Method 2
The force applied to the tension equalizer is redirected through a combination of pulleys
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A flexible screen material can be cut out of square, or part of the screen frame can be formed out of square such that when the screen is fitted to the screen frame, there is less sagging.