| 摘要 |
In roller blinds of the type having a spring-motor interposed between a fixed shaft and a tube to wind up a screen on the tube, a decelerator comprising a one-way clutch mounted on the fixed shaft, an epicyclic gearing having a sun gear, planet gears rotatably supported by the one-way clutch, and a ring gear coaxially secured to the inside of the tube, and a centrifugal brake having a brake drum secured to the inside of the tube, a rotary shaft directly connected to the sun gear, and centrifugally expansible brake shoes mounted on the rotary shaft for frictional engagement with the brake drum. The one way clutch permits the planet gears to rotate about the sun gear together with the tube when the screen is payed out. But, it prevents the planet gears from rotating about the sun gear when the screen is wound up by the spring-motor, resulting in that the sun gear or rotatary shaft rotates more rapidly in the direction opposite to the tube to force the brake shoes against the brake drum.
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