| 摘要 |
A pleated fabric is connected between an upper fixed sill and a movable sill. The movable sill is between the upper fixed sill and a lower fixed sill. Strings are resiliently secured to the sills and slidably frictionally engaged with the movable sill symmetrical relative to the sills. The friction engagement tends to keep the movable sill in place at whatever location the sill is moved regardless the blind orientation relative to gravity. A projection symmetrically located on the movable sill receives an apertured connector attached to a pole. The connector closely engages the projection and movable sill for remotely moving the movable sill parallel to an axis which is symmetrical to the friction load produced by the strings. The connector transmits a force vector from the pole to the movable sill symmetrical with respect to the friction load of the strings to avoid tilting the movable sill during its movement. |
