Conical Cord Drive for Easier Window Blind Operation
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Solution Overview
Problem
Existing cord drives for window coverings are cumbersome, requiring excessive force, complicated operation, and can be difficult to manage, especially when the blind is in fully raised or lowered positions, with issues like cord tangling and drag on the floor.
Innovation Solution
A cord drive system that reduces the distance the drive cord travels by up to 65% and provides a mechanical advantage, using a cone drive with a roller lock mechanism and tassel weight, allowing for easy operation with minimal force, and incorporating a spring assist for heavier blinds, with options for hidden or exposed cord configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional cord drive system is used to raise or lower window coverings, then the blind can be moved between extended and retracted positions, but excessive force is required and the cord must travel a long distance making it cumbersome to operate
Solution Approach 1:
The patent employs a conical spool with a variable radius instead of a traditional cylindrical spool. The cord wraps around the cone at different radial distances from the axis of rotation, creating a mechanical advantage that reduces the force required to operate the system. As the cord wraps closer to the cone's apex, the effective radius decreases, providing greater mechanical advantage and reducing the operating force needed.
Solution Approach 2:
The system dynamically adjusts the mechanical advantage during operation. As the blind moves from extended to retracted position, the cord's wrap location on the conical spool changes, automatically varying the leverage ratio. This dynamic adjustment optimizes the force requirements throughout the full range of motion, making the system easier to operate at all positions.
2Length of moving object
If the drive cord travels the full distance of the window covering movement, then the blind can be fully raised and lowered, but the cord becomes difficult to reach and manage
Solution Approach 1:
The conical spool geometry allows the cord to wrap at progressively smaller radii as it winds onto the spool. This reduces the effective circumference of each wrap, allowing the cord to achieve the necessary winding capacity in a more compact space. The result is that the cord doesn't need to travel as far linearly to accomplish the same function, improving accessibility.
Solution Approach 2:
The system changes the geometric parameter of the spool from a constant radius (cylinder) to a variable radius (cone). This parameter change allows the cord wrap length to be optimized - the cord wraps around smaller effective circumferences as it winds in, reducing the total cord travel distance required while still achieving full blind movement capability.
3Device complexity
If the cord wraps around a simple spool, then the mechanism is simple, but the cord easily tangles and drags when the blind is fully raised or lowered
Solution Approach 1:
The conical geometry of the spool naturally guides the cord into tight, uniform wraps as it winds onto the surface. The tapering shape prevents the cord from overlapping or tangling by ensuring each wrap sits neatly beside the previous one. This geometric constraint inherently manages the cord better than a cylindrical spool, reducing tangling and dragging issues.
4Ease of operation
If the drive cord is made accessible for easy operation, then the user can easily pull it, but the cord may drag on the floor when the blind is fully raised
Solution Approach 1:
By changing from a cylindrical to a conical spool geometry, the system reduces the total cord wrap length required. This parameter change allows the cord to be shorter while still achieving full blind movement, preventing the cord end from reaching the floor when the blind is in the fully raised position, thus eliminating the dragging problem while maintaining accessibility.
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 system simplifies operation, reduces the force required to raise or lower window coverings, prevents cord tangling, and keeps the blind in place securely, making it easier to use even for large or heavy window coverings, while maintaining accessibility and avoiding floor drag.
Implementation Method 1
A cord drive system that reduces the distance the drive cord travels by up to 65% and provides a mechanical advantage
Implementation Method 2
cone drive with a roller lock mechanism
Data Source
AI summary
A cord drive mechanism to convert linear motion to circular motion for use in coverings for architectural openings. Various controls are used to provide a braking force on the cord. Some of the embodiments incorporate a capstan.