Method for operating a spring in a flat rate mode particularly adapted for typewriter ribbon cartridges.

摘要

Flat rate spring (60) operating beyond the elastic limit of the material of which it is constructed. The spring (60) includes a length of resilient material having terminal end portions (62,63) and a central body portion (61). The terminal end portions (62, 63) are adapted for respective connections to a first member (50A) and a second member (52A). Each terminal end portion comprises a convoluted portion of the resilient material, having a central axis substantially perpendicular to the body portion (61). The convoluted portions (62,63) are dimensioned so that, upon separation of the first and second members (50A, 52A) due to a predetermined load, they uncoil and are stressed beyond the yield point of the material so that a substantially constant load placed on the convoluted portions by said separation effects further uncoiling of the convoluted portions. The spring (60) is particularly adapted to provide a bias between a ribbon take-up spool (51) and its spiked driver (52) within a typewriter ribbon cartridge.