| 摘要 |
A covering system for apertures, such as windows, has a cross bar that is slidably mounted between a pair of tracks. Each end of the cross bar is connected to a belt that circulates in its respective track. The belts positively engage respective pulleys which are connected by a shaft. The cross bar is thereby prevented from becoming skewed as it is slid along the tracks. A locking device locks the cross bar at a desired position along the tracks. The free end of a roller blind may be connected to the cross bar. Preferably the roller blind turns with the pulleys and the belts are tapered so that the roller blind rolls and unrolls at the same rate that the cross bar is moved. This makes it unnecessary for the roller blind to be spring loaded. The cross bar may also be used to support horizontal or vertical slatted blinds.
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