Variable Diameter Screw Position Fixing for Window Coverings
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Solution Overview
Problem
Conventional roller shades require inconvenient operation to dispel the braking mechanism for rolling up, especially when mounted inside window frames, due to the proximity of the weight rod to the window frame's bottom margin, and rely on costly prestressed springs for sufficient rewinding force.
Innovation Solution
A position-fixing system incorporating a variable diameter screw, guiding portion, and elastic member that gradually increases radial tightening force as the roller tube rotates, allowing precise control of the roller tube's rotation and position fixation by deforming the elastic member along the screw's broadening working section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If prestressed springs with high elasticity are used to ensure sufficient rewinding force, then the rewinding force is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the parameter of the screw's diameter along its axis, creating a variable diameter screw where the diameter gradually increases from the first end to the second end. This parameter change allows the screw to generate variable friction force without requiring expensive prestressed springs, as the friction force is controlled by the geometric parameter (diameter) of the screw itself
Solution Approach 2:
The variable diameter screw structure allows the system to self-regulate the friction force based on the elastic member's deformation. As the elastic member deforms and expands, it automatically increases the normal force on the screw, which in turn increases the friction force to match the weight of the covering material, eliminating the need for externally controlled prestressed springs
2Reliability
If a braking mechanism is used to hold the covering material at any position, then the position fixation reliability is improved, but the ease of operation deteriorates when the weight rod is close to the window frame bottom margin
Solution Approach 1:
The patent replaces the conventional braking mechanism with a friction-based holding system. The variable diameter screw generates friction force through the meshing portion's interaction with the screw surface, eliminating the need for complex brake components and their associated operation procedures
Solution Approach 2:
The friction force parameter is dynamically adjusted by the variable diameter screw geometry. As the elastic member deforms during operation, the normal force on the screw changes, which automatically adjusts the friction force to match the load, providing reliable position fixation without requiring manual intervention to activate or deactivate brakes
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
Enables easy and reliable position fixation of the window covering material, reducing the need for costly prestressed springs and simplifying the operation by applying a variable friction force that corresponds to the degree of expansion, thus maintaining the covering's position effectively.
Implementation Method 1
The elastic member is adapted to slide along the guiding portion. The elastic member has a meshing portion provided along an inner side thereof and a guided portion provided along an outer side thereof. At least a part of the meshing portion meshes with the working section of the variable diameter screw. When the roller tube rotates in a first rotation direction, the elastic member moves along the working section of the variable diameter screw in a direction from the first end toward the second end, and the elastic member deforms correspondingly
Implementation Method 2
as the elastic member deforms, the elastic member exerts a gradually increasing unit tightening force to the variable diameter screw in a radial direction of the variable diameter screw, whereby to dampen a rotation of the roller tube in the first rotation direction
Data Source
AI summary
A position-fixing system for a window covering, which has a roller tube, includes a variable diameter screw, a guiding portion, and an elastic member. The variable diameter screw has a working section gradually broadening in a radial direction thereof. The guiding portion extends along an inner wall of the roller tube in an axial direction thereof. The elastic member fits around the variable diameter screw, and is movable along the guiding portion. The elastic member has a meshing portion provided on an inner side thereof to mesh with the working section, and a guided portion provided on an outer side thereof to slide along the guiding portion. When the roller tube rotates in a direction, the elastic member moves along the working section and deforms, whereby to exert a gradually increasing unit tightening force to the variable diameter screw in the radial direction, dampening its rotation.