| 摘要 |
A roller blind including a roller of having a roller length and a roller outer diameter, a fabric attached to said roller for winding and unwinding from said roller. The fabric has a fabric length, a fabric weight, a fabric height, and fabric thickness. The blind includes a bottom bar having a bottom bar weight, and at least one spring operatively connected to the roller to drivingly rotate the roller in at least one direction of rotation. The spring is selected according to a Protocol such that it's length ensures that it drives the roller with a constant operating force. |
