Variable-Stiffness Roller Tube Resists Deflection
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Solution Overview
Problem
Large roller shades for wide windows face the challenge of tube sag, which leads to undesirable aesthetic and operational issues such as visible sag lines and wrinkles in the shade material, due to the increased deflection of the roller tube.
Innovation Solution
A low-deflection roller tube configuration is implemented, featuring a hybrid design with a metal inner tube and a carbon fiber outer tube. The carbon fiber tube is additively constructed with layers of varying tensile moduli, creating sections with different material stiffness to minimize deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the roller tube length is increased to cover wide windows, then the coverage area is improved, but tube sag increases causing aesthetic and operational issues
Solution Approach 1:
The roller tube incorporates variable stiffness along its length, with higher stiffness in the middle section and lower stiffness at the ends. This local differentiation allows the tube to resist sagging in the critical middle region while maintaining flexibility at the supported ends, resolving the contradiction between long-span coverage and shape maintenance.
Solution Approach 2:
The roller tube uses a composite construction combining materials with different stiffness properties in a variable ratio along the tube length. This composite approach enables the tube to achieve both the structural rigidity needed to prevent sagging over wide spans and the flexibility required at support points, simultaneously improving coverage area while maintaining shape.
2Shape
If the tube diameter is increased to achieve increased stiffness, then tube sag is reduced, but additional space is required impacting aesthetic
Solution Approach 1:
Instead of uniformly increasing tube diameter throughout, the invention applies variable stiffness locally along the tube length. The middle section has higher stiffness to prevent sagging, while the end sections have lower stiffness to minimize volume. This resolves the contradiction by achieving the required shape stability without the penalty of increased overall volume.
Solution Approach 2:
The invention changes the stiffness parameter along the length of the tube rather than maintaining a constant diameter. By varying the stiffness parameter locally, the tube achieves adequate rigidity for preventing sag over wide spans while keeping the overall volume compact and aesthetically pleasing.
3Shape
If supports are added along the roller tube length to prevent sag, then tube sag is reduced, but movement of shade material over supports causes wear
Solution Approach 1:
The invention extracts the support function from discrete physical supports and embeds it directly into the roller tube structure through variable stiffness. By taking out the separate support components and integrating the support function into the tube itself, the design eliminates the mechanical interaction between shade material and supports, preventing wear while maintaining shape.
Solution Approach 2:
The variable stiffness sections of the roller tube act as an intermediary that provides structural support without requiring direct contact points with the shade material. The distributed stiffness gradient provides continuous support along the tube length, eliminating the need for discrete supports that would create wear points.
Data Source
AI summary
A low-deflection roller tube of a motorized roller shade may include a first tube and a second tube that is attached to the first tube. The first tube may be configured to operably couple to the motor drive unit of the roller shade. The second tube may comprise a plurality of carbon fiber layers additively constructed on the first tube, and may be fabricated such that first and second longitudinal portions of the roller tube exhibit different material stiffness characteristics from each other. The first and second portions of the roller tube may be made of carbon fiber material having different tensile moduli. Layers of carbon fiber material in the first portion may be staggered with layers of carbon fiber material in the second portion at an interface between the first and second portions.