Cord Retractor Friction Mechanism for Window Covering Position Stability
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Solution Overview
Problem
Conventional cordless window coverings face issues with maintaining the bottom rail in a stationary position due to variable spring force, gravitational force, and friction, leading to unintended movement after operation.
Innovation Solution
A cord retractor system with a housing, driving wheel, spring, reeling wheel, friction member, and unidirectional transmission mechanism that provides constant resistance in one direction to stabilize the bottom rail, ensuring it remains in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spring mechanism is used to assist in extending or retracting the covering, then the operation of the window covering is automated and easier to operate, but the bottom rail cannot remain stationary at a designated position due to variable spring force and gravitational force
Solution Approach 1:
The patent applies a friction member that can dynamically adjust its frictional resistance based on the operating state. During extension, the friction member provides high friction to control descent speed; during retraction, it provides low friction to reduce resistance; and during stationary positioning, it provides controlled friction to maintain position. This dynamic adjustment resolves the contradiction between automated operation and position stability.
Solution Approach 2:
The friction member changes its frictional parameter (coefficient of friction or normal force) depending on the operational phase. By varying the frictional resistance parameter, the system achieves different operational characteristics: controlled extension, assisted retraction, and stable positioning, thereby resolving the contradiction between ease of operation and reliability.
2Force
If the spring force is increased to support the bottom rail and covering, then the bottom rail can be held up, but the bottom rail may move upward unexpectedly when the covering weight decreases
Solution Approach 1:
The friction member acts as a feedback mechanism that continuously adjusts the resistive force based on the balance between spring force and gravitational force. When the covering weight decreases, the friction member increases its resistive force to prevent upward movement, and when the weight increases, it reduces resistance. This feedback control resolves the contradiction between sufficient support force and precise position control.
Solution Approach 2:
The friction member serves as an intermediary between the spring mechanism and the bottom rail, mediating the interaction between spring force and gravitational force. It provides a controllable resistive force that balances the variable spring force with the variable gravitational force, preventing unexpected movement while maintaining support.
3Force
If the spring force is decreased to reduce upward movement, then the bottom rail can stay lower, but the bottom rail may move downward when the covering weight increases
Solution Approach 1:
The friction member dynamically adjusts its frictional resistance to compensate for changes in spring force and covering weight. When the covering weight increases, the friction member increases its resistive force to prevent downward movement. This dynamic adjustment allows the system to maintain position control without requiring a consistently high spring force.
4Reliability
If friction is increased to prevent bottom rail movement, then position stability is improved, but the operation of extending and retracting the covering becomes more difficult
Solution Approach 1:
The friction member dynamically varies its frictional resistance based on the operational phase. During extension and retraction operations, it reduces friction to minimize resistance and ease of operation. During stationary positioning, it increases friction to provide position stability. This dynamic behavior resolves the contradiction between position stability and ease of operation.
Solution Approach 2:
The system changes the friction parameter (coefficient of friction or contact force) depending on whether the system is in motion or stationary. High friction is applied only when positioning is required, while low friction is maintained during operation. This parameter switching resolves the contradiction between stability and operational ease.
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 cord retractor system effectively maintains the bottom rail's position by providing consistent resistance, preventing unwanted movement and allowing controlled operation of the window covering.
Implementation Method 1
one of a first frictional force and a second frictional force is generated for providing substantially constant resistance to rotation of the reeling wheel. The first frictional force is generated between the first limiting member and the friction member, as the first limiting member rotates with respect to the friction member, and the second frictional force is generated between the friction member and the shaft, as the friction member is driven by the first limiting member to rotate with respect to the shaft.
Data Source
AI summary
A cord retractor for a window covering comprises a housing and a driving wheel, a reeling wheel, a spring, a friction member and a unidirectional transmission mechanism. The driving wheel and the reeling wheel can rotate with each other. The spring is coupled with the driving wheel and is wound on or unwound from the driving wheel according to a rotating direction of the driving wheel. The friction member is in a closed loop shape and surrounding a shaft of the housing. The unidirectional transmission mechanism is coupled with the friction member and the reeling wheel, and operated in different operation modes according to a rotating direction of the reeling wheel, by which the friction member provides constant resistance to the rotation of the reeling wheel when the reeling wheel rotates in a first direction, and stops providing resistance when the reeling wheel rotates in a second direction.