Cord-Winding Device for Cordless Blinds Using Constant Force Spring
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Solution Overview
Problem
Conventional blind assemblies without a pull cord face issues such as shortened service life of torsion springs due to deformation, complex component coordination, high costs, and unbalanced pulling forces, making them inconvenient and costly to assemble and use.
Innovation Solution
A cord-winding device comprising a base seat, an adjustment unit with a slide seat, rollers, and a constant force spring, where the lift cord winds around rollers and extends through the blind assembly, generating a balanced pulling force by counteracting the resilient restoring force of the constant force spring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If torsion springs are used to provide torsion for winding the drive cord, then the blind assembly can achieve cord-winding function, but the service life of the torsion springs is shortened due to large deformation and reverse winding
Solution Approach 1:
The patent changes the spring parameter from torsion spring to constant force spring, which maintains a constant restoring force throughout its extension range. This parameter change eliminates the large deformation and reverse winding issues of torsion springs, thereby extending service life while maintaining the cord-winding function
Solution Approach 2:
The patent replaces the expensive but short-lived torsion spring with a constant force spring that offers longer service life. Although constant force springs may be slightly more expensive initially, their extended durability reduces long-term replacement costs and maintenance requirements
2Ease of operation
If multiple components and complex coordination are used to achieve blind assembly operation, then the cord-winding function can be realized, but the assembly becomes inconvenient and cost increases
Solution Approach 1:
The patent merges multiple components into an integrated cord-winding device where the constant force spring, slide seat, and drive cord work together as a unified mechanism. This integration simplifies the overall structure, reduces the number of separate components, and makes assembly more convenient while maintaining full operational functionality
Solution Approach 2:
The constant force spring mechanism serves multiple functions simultaneously: it provides the restoring force for cord winding, enables blind assembly operation, and simplifies the overall device structure. This multi-functionality reduces the need for separate components and coordination mechanisms
3Force
If the tension space of the support frame is increased to provide sufficient elastic force, then the tension spring can generate adequate force, but the support frame length is restricted and elastic fatigue occurs
Solution Approach 1:
The patent changes from a tension spring requiring long tension space to a constant force spring that generates adequate force within a compact space. The constant force spring's unique parameter characteristics allow it to maintain sufficient restoring force without requiring extensive length, thus avoiding elastic fatigue while providing adequate force
4Force
If the tension of the tension spring is increased to balance the weight of the blind body, then the pulling force can be balanced, but excessive force is required to pull the blind body downward and damage may occur
Solution Approach 1:
The patent changes from a tension spring with variable force to a constant force spring that maintains a consistent, moderate restoring force throughout operation. This parameter change eliminates the need for excessive force to overcome high initial tension, allowing users to pull the blind body downward easily without risking damage, while still achieving weight balance
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 device achieves a force-balanced state, simplifies assembly and use, reduces component complexity and costs, and is suitable for various blind assembly sizes, ensuring smooth operation and prolonged service life.
Implementation Method 1
a spring unit including a constant force spring that has a first end fixed to the base seat and a second end fixed to the slide seat... The slide seat in turn pulls the constant force spring so that the constant force spring generates a resilient restoring force
Implementation Method 2
The lift cord winds around the rollers and extends through the base seat... The lift cord is configured to support the weight of the blind assembly to thereby generate a pulling force
Data Source
AI summary
A cord-winding device for a blind assembly having no pull cord includes a base seat defining a slide channel and having a bottom side configured to removably mount the blind assembly thereto, and an adjustment unit including a slide seat mounted slidably in the slide channel, a plurality of rollers mounted on the base seat and the slide seat, respectively, and a constant force spring having first and second ends respectively fixed to the base seat and the slide seat. A lift cord winds around the rollers and extends through the base seat. The lift cord is configured to extend through the blind assembly after extending through the base seat so as to be positioned to the base seat and the blind assembly.