| 摘要 |
This invention involves a spring operated, reversibly rotatable body having a surface on which a flexible, elongated object, e.g. a wire or a band, can be wound, said body being connected with a spring which is stretched by the rotation of the body during the unwinding of said elongated object. The improvement includes a transmission between the elongated object and the spring, said transmission having a gearing ratio which is varied during the rotation of the body. In a preferred embodiment, the transmission comprises two rotatable cones, said cones being connected by means of a traction wire which is wound on the surfaces of said cones. One of the cones is connected with the spring and the other with an output shaft. The aim of the improvement is to provide a means by which the tractive force caused by said spring in the elongated object during the rotation of said body will remain constant. The improvement is particularly useful in retractable safety belts to obtain a constant force in the belt strap during extension of the belt.
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