| 摘要 |
A bi-directional clutch (10) particularly useful in window shade applications. The bi-directional clutch (10) includes a first or core member (34) and an unwrap spring (48), that is, a spring having an inside diameter somewhat smaller than the diameter of the core, the spring (48) being wound around the core (34). The unwrap spring has a number of helical turns (49) and spring tangs (50, 52) which extend outwardly past the circumference of the spring and generally perpendicular to the axis of the spring (48). The spring (48) is controlled by a second, control or driving member (66) which, when rotated, applies force to one or the other of the spring tangs (50, 52) to unwrap or loosen (48), thereby allowing the spring (48) to rotate relative to the core (34). As the spring (48) rotates, one of the spring tangs (50, 52) abuts a third or driven member. The third or driven member (98) is rotated by the spring (48), allowing the third member (98) to rotate relative to the first or core member (34). The third or driven member (98) continues to rotate, relative to the first or core member (34), until the second, control or driving member (66) stops rotating. However, when the driven member (98) is rotated directly, the spring (48) is locked onto the core member (34) and further rotation of the driven member (98) is prevented. According to a first embodiment of the invention, the spring tangs (50, 52) of the unwrap spring (48) are crossed-over, the second, control or driving member (66) has a U-shaped channel (92) which abuts either of the outer surfaces (58, 60) of the spring tangs (50, 52) as the driving member (66) rotates, and the third or driven member (98) has a rib (108), located between the spring tangs (50, 52) which is abutted by the inner surface (62) of the spring tangs (50, 52) to transfer rotation from the driving (66) to driven member (98). In a second embodiment, the spring tangs (116, 118) of the spring (48) are not crossed-over, the second, control or driving member (66) has a rib (132) located between the inner surfaces (124, 128) of the spring tangs (116, 118), and the third or driven member (98) has a U-shaped channel (138) which is moved by the outside surface (126) of the spring tangs to transfer rotation from the driving (66) to driven member (98). When the bi-directional clutch (10) is used as part of a window shade mechanism, the first or core member (34) is held stationary by attachment to a bracket (12) which is affixed to a window frame (14), the third or driven member (98) is fixedly attached to a window shade (20), and the second, control or driving member (66) is turned in a clockwise or counter clockwise direction by a window chain or cord (76), to either raise or lower the shade (20). |
