| 摘要 |
A ribbon cassette (1) for use in typewriters comprises a casing (2) in which a supply spool (4) is mounted for rotation together with a toothed disc (20) on a common pin (3). A tensioning and guiding device (10) which also acts as a brake for the supply spool (4) consists of a bent wire having a first section (11), fixed at its free end to the casing at (2a), a second section (12) extending substantially perpendicularly to the first section and a junction portion (14) which is adapted to engage in the toothed disc (20) to prevent rotation of the supply spool. Ribbon unwound from the supply spool is guided round the free end (15) of the second section, which free end may carry a roller (17). The tensioning and guiding device is arranged such that, when tension is applied to the ribbon to unwind it from the supply spool, the second section (12) pivots about portion (14) by a predetermined extent before the detent portion becomes disengaged from the toothed disc on movement of the first section. A take up spool (7) is driven by spikes on a wheel (8) penetrating into the ribbon being wound onto spool (7). The spool (7) is carried on a pivotable lever (5) so that spool (7) pivots towards the supply spool (4) as the diameter of the ribbon wound on spool (7) increases. The device (10) delays movement of the supply spool until slightly after drive wheel (8) has started rotating so that the raising of the ribbon (16) to its printing position is not hindered. <IMAGE> |
