| 摘要 |
A projection screen arrangement has a housing mounting a rotary roller for winding in and unwinding a projection screen. A rotary knob which is actuable from the outside of the housing is non-rotatably connected to the roller for tensioning the projection screen in the extended position, while a terminal bar member is provided at the end of the projection screen remote from the roller. A push member is mounted for radial movement in the housing and is adapted to be actuated against a spring loading by the terminal bar member when the projection screen is fully wound into the housing. The push member displaces a detent member which co-operates with a further detent means which is non-rotatable with respect to the rotary knob, for locking the roller in the winding-in direction, whereby the winding of the projection screen on the roller in the fully wound-in condition can be slackened, without the spring loading the roller in the winding-in direction re-tightening the projection screen wound on the roller.
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