| 摘要 |
A spring drive system for a cordless window shade includes multiple rotary drums respectively connected with suspension cords, and one or more springs respectively connected with the rotary drums. The rotary drums are operatively connected with each other, so that they can synchronously rotate to wind and unwind the suspension cords. Moreover, each of the rotary drums is connected with an end of one spring. The spring torque can act to sustain a bottom part of the window shade at any desired height, and drive rotation of the rotary drums to wind the suspension cords when the bottom rail is raised upward. |
