The decelerator as conventionally used in the roller blind is one among air-damper, oil-damper and fly-wheel type brakes, thereforedisadvantageously requiring an accurate adjustment for desired performance.
More specifically the invention refers to a roller blind structure comprising cylindrical member having secured thereto one end of a screen and being rotatably mounted in two axially spaced apart brackets and being further provided with a pulleyto the hub of which is secured one end of a cord, said cord being intended to be wound upon said hub in a direction opposite to the direction in which said screen is wound upon said cylindrical member, such that unwinding cord from said pulley results insaid screen being wound upon said cylindrical member and vice versa.. This conventional roller blind structure is rather complicated and has a number of drawbacks, for instance the difficulty in stopping thescreen in a desired China Brake Drum Series Factory position, the bang occurring when the screen is wound up, the soiling of the screen when it is grabbed to wind up the screen and the fact that the screen will be situated at a distance from the window frame when in its rolled downposition, thereby causing loss of heat, draught and an insufficient light shielding.
The spring-motor type roller blind is desirably equipped with a decelerator to reduce the screen-winding speed to the extent that the screen is always wound up at moderate speeds even if it is fully payed out and then released. The one-way clutch permits the planet gears to rotate about the sun gear with the ring gear or tube in the direction in which thescreen is payed out but prevents the planet gears from rotating about the sun gear with the ring gear or tube in the opposite direction. Several attempts have therefore been made to provide a roller blind without the disadvantages of the conventional roller blind, and as it is obvious that the kind ofroller blind to which this invention refers may to a great extent eliminate these drawbacks, attempts have been made to practice the principles of said roller blind structure in designing such a roller blind.
For accomplishment of the object, the decelerator of the invention is used in roller blinds of the type having a spring-motor interposed between a fixed shaft and a tube, and composed of a one-way clutch having the stator thereof secured to thefixed shaft, an epicyclic gearing having a ring gear secured to the inside of the tube, a sun gear, a plurality of planet gears rotatably supported by the rotator of the one-way clutch, and a centrifugal brake having a rotary member secured to the sungear, centrifugally expansible brake shoes mounted on the rotary member and a brake drum secured to the inside of the tube. Otherwise, it iscaused to rise rapidly and make a noise by a strong resilience accumulated in the spring-motor while it is payed out