Blind Cord Spool Structure with Planetary Gears for Compact Spring Drive
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Solution Overview
Problem
Conventional blind cord mechanisms suffer from spring fatigue due to repetitive compression and extension, requiring larger springs and additional friction devices, leading to instability and increased cost, while lacking effective torque enhancement and space-efficient design.
Innovation Solution
A blind cord spool structure utilizing planetary gears and a force-receiving wheel to reduce the weight and volume of volute spiral springs, integrated with a long rectangular bottom case for a compact design, enhancing torque and reducing operational costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional spring reels and string reels are used without direct transmission relationship, then the mechanism can operate, but torque enhancement is not achieved and transmission mechanism size increases
Solution Approach 1:
The patent combines the spring reel and string reel into a single integrated cord spool structure where the volute spiral spring is reeled on the same spool that winds the cord. This merging eliminates the need for separate transmission mechanisms between spring reels and string reels, achieving torque enhancement while reducing overall mechanism volume.
Solution Approach 2:
The patent nests the volute spiral spring inside the cord spool structure, with the spring reeled on the inner circumference of the spool. This nested arrangement allows the spring to be contained within the same spatial envelope as the cord winding mechanism, eliminating additional external transmission components.
2Strength
If larger springs are used to augment elasticity, then spring strength increases, but spring volume and cost increase
Solution Approach 1:
The patent introduces a planetary gear mechanism as an intermediary between the user's pulling force and the spring loading. The planetary gears provide mechanical advantage, allowing a smaller spring to generate sufficient torque by amplifying the input force through gear ratio multiplication.
Solution Approach 2:
The patent changes the mechanical parameters of the system by introducing a planetary gear train with multiple sun gears and planet gears. This gear configuration creates a high reduction ratio that transforms small input movements into large torque output, enabling the use of a compact spring with adequate elasticity.
3Reliability
If position-limiting devices are mounted to provide friction, then spring protection from fatigue is achieved, but device complexity increases
Solution Approach 1:
The patent designs the cord spool with self-limiting mechanical features where the spool geometry and gear arrangement naturally prevent over-winding and over-compression of the spring. The structure itself provides the position-limiting function through its physical constraints, eliminating the need for separate friction-based limiting devices.
4Ease of operation
If reducers with leading and following wheels are used for indirect drive, then the mechanism can transmit motion, but assembly space requirements increase
Solution Approach 1:
The patent merges the leading wheel and following wheel functions into a single planetary gear system where multiple gear interactions occur within a compact arrangement. The sun gears, planet gears, and ring gear work together in a unified mechanism that provides the necessary motion transmission without requiring separate leading and following wheel assemblies.
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 structure achieves efficient, cost-effective operation with reduced spring weight and volume, facilitating easy installation and market competitiveness by minimizing the height and width of the spool, while extending the life of the cords and reducing wear.
Implementation Method 1
A blind cord spool structure utilizing planetary gears and a force-receiving wheel to reduce the weight and volume of volute spiral springs
Implementation Method 2
utilizing planetary gears and a force-receiving wheel to reduce the weight and volume of volute spiral springs, integrated with a long rectangular bottom case for a compact design, enhancing torque
Implementation Method 3
two rotatable units, two spool rollers and a top case. The bottom case is in long rectangular shape, with a planetary gear seat centrally disposed at the bottom case... with a volute spiral spring reeled on each of the two rotatable units
Data Source
AI summary
A blind cord spool structure has a cord spool. The cord spool includes a bottom case, force-receiving wheel, driven chainwheel, top case, two rotatable units, and two spool rollers. The bottom case is in long rectangular shape. The bottom case and the top case allow the force-receiving wheel, driven chainwheel, rotatable units and spool rollers to be fitted together. The force-receiving wheel meshes with the driven chainwheel through a plurality of planetary gears and interlocks with the spool rollers and rotatable units through a driven gear. The high speed reduction ratio of the planetary gears effectively reduces the required weight of a volute spiral spring and reduces the operation cost of the volute spiral spring. With the bottom case being in long rectangular shape, the force-receiving wheel, rotatable units and spool rollers can be collectively mounted on the same standard surface, allowing the cord spool to be structurally simple.