Spring Motor Assembly With Angled Capstans for Stable Cordless Shades
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Solution Overview
Problem
Conventional spring motor assemblies for architectural-structure coverings face challenges in balancing force variation, tortuous path drag, uneven cord wrapping, and jamming issues, particularly in cordless designs, leading to non-smooth operation and positioning instability.
Innovation Solution
A spring motor assembly with angled capstans and parallel longitudinal axes for lift cords, integrated geartrain, and a pancake-style configuration, which includes output, take-up, and storage spools, ensuring smooth cord wrapping and balanced force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a constant force spring motor is used to support the full weight of the covering, then the covering can be supported in the retracted position, but the covering cannot remain stable in the extended position due to excessive lifting force
Solution Approach 1:
The patent applies a variable force spring motor instead of a constant force spring motor. The spring motor is designed to provide different lifting forces at different positions: maximum force when the covering is retracted and minimum force when the covering is extended. This dynamic adjustment of force allows the covering to remain stable at both fully retracted and fully extended positions without requiring a clutch mechanism.
Solution Approach 2:
The spring motor's force output parameter is changed from constant to variable. The spring is configured with specific physical parameters (wire diameter, mean coil diameter, number of active coils, material properties) that enable the force to vary continuously as the covering moves between positions, matching the changing weight distribution and maintaining equilibrium throughout the range of motion.
2Volume of moving object
If lift cords pass through a tortuous path in the spring motor assembly, then the mechanism can be compact, but drag increases and dampens the spring motor assembly action
Solution Approach 1:
The patent reconfigures the lift cord path from a planar tortuous route to a three-dimensional routing that exits the spring motor assembly in a direction substantially perpendicular to the plane of the capstans and cord storage spools. This dimensional change allows the cords to bypass the tortuous path entirely, reducing drag while maintaining compact assembly dimensions.
Solution Approach 2:
The lift cords are extracted from the traditional path that passes through the maze of pins and along the face of the capstans. Instead, the cords are routed to exit from the rear of the spring motor assembly, removing them from the high-friction zones and eliminating the dampening effect of the tortuous path.
3Device complexity
If capstans are positioned perpendicular to cord storage spools, then the structure is simple, but lift cords wrap unevenly and may jam
Solution Approach 1:
The patent positions the capstans at an asymmetric angle of 30 to 60 degrees relative to the plane of the cord storage spools, rather than perpendicular (90 degrees) or parallel (0 degrees). This asymmetric positioning optimizes the cord wrapping path, ensuring smooth operation and preventing jamming while maintaining structural simplicity.
Solution Approach 2:
The angular parameter of capstan positioning is changed from the conventional perpendicular orientation to a specific range of 30-60 degrees. This parameter optimization ensures that the lift cords wrap evenly around the cord storage spools during both extension and retraction, preventing uneven stacking and jamming while maintaining ease of manufacture.
4Reliability
If the spring motor assembly is designed with multiple spools and capstans, then cord wrapping is improved, but assembly complexity increases
Solution Approach 1:
The patent combines multiple functional components (output spool, take-up spools, cord storage spools, and capstans) into a single integrated spring motor assembly unit. All components are mounted on a common housing with coordinated geometry, allowing the entire mechanism to be manufactured as one unit or pre-assembled module, thereby reducing installation complexity despite the multiple moving parts.
Solution Approach 2:
The spring motor assembly is designed as a multi-functional unit where the same housing and mounting structure serve multiple purposes: supporting the output spool, mounting the take-up spools, positioning the cord storage spools, and providing the angled capstan supports. This universal design reduces the number of separate components and simplifies assembly.
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 solution provides stable positioning and smooth operation of architectural-structure coverings by minimizing cord overlap and drag, maintaining equilibrium at desired positions, and facilitating easy assembly.
Implementation Method 1
Each of the one or more take-up spools including a spring coupled to the output spool, the spring configured to wrap about the output spool during extension of the covering and unwrap from the output spool during retraction of the covering
Data Source
AI summary
A spring motor assembly for use in an architectural-structure covering is disclosed. The spring motor assembly including an output spool, one or more take-up spools, one or more springs coupling the take-up spool(s) to the output spool, cord storage spools for wrapping and unwrapping lift cords thereabout, and capstans (e.g., one-way wheels). In some embodiments, the spring motor assembly includes one or more features to facilitate improved operation. For example, in some embodiments, the capstans include a central longitudinal axis that is angled relative to a central longitudinal axis of the cord storage spools. In addition, in some embodiment, the central longitudinal axis of the cord storage spools, the output spools, and the take-up spool(s) are parallel to a front surface of the covering. In addition, in some embodiments, the spring motor assembly is contained within a unitary housing.