Retention device for the winding shaft of a roller blind or the like actuable by a belt

摘要

The invention relates to a retention device for the winding shaft of roller blinds which are actuated manually by a belt. In these roller blinds, precautions must be taken in order to protect the lowered roller-blind armour against being pushed up from outside in an unauthorised manner. Corresponding devices for this purpose are known in different versions, but they all presuppose an automatic retention of the winding shaft. The present invention serves this purpose in that there is provided in a cavity (13) of the belt pulley (11) a continuous internal toothing (27) which is normally held by the force of a leaf spring (30) in blocking engagement with a fixed toothed quadrant (29) which is arranged on the lower half of a bearing housing (17) extending into the cavity (13) of the belt pulley (11). When a pull is exerted manually on the belt (12) downwards in the vertical direction, the internal toothing (27) is automatically separated from the fixed toothed quadrant (29), so that the winding shaft (10) is released for a rotational movement in the winding or unwinding direction. As soon as this manual pull is cancelled, the internal toothing (27) is once again brought automatically into blocking engagement with the toothed quadrant (29) by means of the leaf spring (30). For this purpose, a bearing journal (15) for the winding shaft (10) is supported in a ball bearing (16) which is arranged in the bearing housing (17) so as to be vertically displaceable and which is prestressed upwards by the leaf spring (30). <IMAGE>