| 摘要 |
<p>A spring drive system (15) for window covers (10, 20) is disclosed, which comprises a flat spring drive (26, 31, 41) and the combination whose elements are selected from (1) a band transmission (21) which provides varying ratio power transfer as the cover is opened and closed; (2) a gear arrangement (60) having various gear sets which provide frictional holding force and fixed power transfer ratios; and (3) a gear transmission (70) which provides fixed ratio power transfer as the cover (10, 20) is opened or closed. The combination permits the spring drive force at the cover (10, 20) such as a horizontal slat (10) or pleated or box blind (20) as the cover is opened and closed.</p> |
