Motorized Blind Slat Adjustment With Variable-Ratio Bevel Gears
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Solution Overview
Problem
Conventional slat angle adjustment mechanisms in window blinds utilize worm gears, which require high torque for complete closure, leading to slow operation and inconvenience due to back-drive issues.
Innovation Solution
A slat angle adjustment mechanism using bevel gears with a lower gear ratio and pulleys with varying radial profiles, enabling faster slat rotation and increased torque when needed, while resisting back-drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If worm gears are used to provide high torque for complete slat closure, then the slats can be completely closed, but the operation becomes slow and inconvenient
Solution Approach 1:
The patent applies a variable ratio transmission mechanism where the gear ratio changes during operation. Initially, a lower gear ratio provides high speed for most of the rotation range, and then a higher gear ratio engages to provide high torque for the final closure phase. This dynamic switching resolves the contradiction by providing both high speed and high torque at appropriate moments.
Solution Approach 2:
The transmission mechanism is segmented into multiple stages with different gear ratios. The first stage uses a lower gear ratio for fast rotation, and the second stage uses a higher gear ratio for high torque. This segmentation allows the system to optimize performance for different phases of the slat closure operation.
2Reliability
If worm gears are used to resist back-drive from slat weight, then the slats remain closed, but many turns are required to close the slats
Solution Approach 1:
The variable ratio transmission dynamically adjusts the mechanical advantage during operation. For most of the rotation, a lower gear ratio provides fast movement with sufficient friction to resist back-drive. In the final closure phase, a higher gear ratio provides increased mechanical advantage and friction to ensure complete closure and resist back-drive from slat weight.
Solution Approach 2:
The system changes the transmission ratio parameter during operation to optimize performance. The lower gear ratio is used for fast operation during most of the range, while the higher gear ratio is engaged when needed for complete closure and to resist back-drive, thus reducing the total time required.
3Speed
If a lower gear ratio is used for faster slat rotation, then operation speed increases, but torque decreases
Solution Approach 1:
The system dynamically switches between different gear ratios based on the operational phase. During the majority of the rotation where high speed is needed, a lower gear ratio is used. When the slats approach complete closure and high torque is needed to overcome the back-drive from slat weight, the mechanism transitions to a higher gear ratio to provide the necessary force.
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 mechanism provides high-speed slat rotation with adjustable torque, improving ease of use and efficiency by up to 5-10 times compared to conventional worm gear systems, allowing for both manual and motorized actuation.
Implementation Method 1
a first bevel gear coupled with the rod, a second bevel gear in mechanical communication with the first bevel gear and coupled with the shaft
Implementation Method 2
two pulleys coupled with the shaft and the slats, wherein the pulleys cause adjustment of the tilt angle of the slats in response to rotation of the shaft
Data Source
AI summary
An apparatus for adjusting a tilt angle of a plurality of slats in a window blind is disclosed. The window blind includes a headrail having disposed therein a shaft that causes the tilt angle of the slats to be adjusted when the shaft is rotated. The apparatus comprises a first bevel gear, a second bevel gear in mechanical communication with the first bevel gear and coupled with the shaft, and a motor coupled to the shaft. Actuation of the first bevel gear causes a corresponding rotation of the shaft to adjust the tilt angle of the slats, and actuation by the motor causes a rotation of the shaft to adjust the tilt angle of the slats.