| 摘要 |
<p>A screen-positioning device for use in a roll blind comprising a fixed shaft (20) sustained by a bracket (12) for rotatably supporting the screen-roll (10), an extension shaft (21) secured to the fixed shaft (20) and formed with a drum portion (22) and a screw-bolt portion (23), a torsional spring (25) having one end thereof fixed to the drum portion (22) and the other end loosely turning around the screw-bolt portion (23), a screw-nut (26) mounted on the screw-bolt portion (23) and formed with a conical surface (28) for fitting engagement with the spring (25). When the surface (28) is raised to a predetermined height, the conical surface (28) is so engaged with the free end portion of the spring (25) that the spring (25) is caused to tighten on the drum portion (22). Whenever the screw-nut (26) is engaged with the spring (25), it undergoes the spring-back force to be rotated in the direction in which the screen (30) is lowered. The fixed shaft (20) is supported by the bracket (12) with the intervention of a one-way clutch mechanism comprising a brake drum (38) secured to the bracket (12), a brake coil spring (36) wound around the brake drum (38), a sector (34) secured to the fixed shaft (20) and fitted on the brake coil spring (36), a slit (35) formed in the periphery of the sector (34) to receive opposite ends (36a, 36b) of the brake coil spring (36), a dial-ring (40) loosely fitted on the sector (34) and provided with an inner projection (41) put in between the both ends (36a, 36b). The roll-up height of the screen is determined by an axial position of the screw-nut (26) on the screw-bolt portion (23). The axial position is easily adjusted by use of the dial-ring (40), which is rotatable together with the fixed shaft (20) or extension shaft (21) move the screw-nut (26) along the screw-bolt portion (23).</p> |
