| 摘要 |
917,562. Ink-ribbon mechanisms. AGFA A.G. Sept. 16, 1959 [Sept. 22, 1958], No. 31641/59. Class 100 (4). An ink-ribbon feed mechanism particularly for a franking machine has an automatic reversing mechanism controlled by an overcentre spring. A double pawl 8 is pivoted at 9a on a counterbalanced member 9, in turn pivoted at 9b on a rocker 11 capable of racking on a pin 11b, and is arranged to engage one of the ratchet wheels 6, 7 to effect feeding of an inkribbon 3 between spools 1, 2. Springs 10, 12 control the position of the pawl 8 and the member 9 respectively while a spring 15 tends to hold the rocker 11 against a stop 14. In operation of the franking machine a pin 11c is engaged to move the rocker 11 against a stop 13 and in the position of the pawl 8 shown to cause a feed stroke of the ratchet wheel 6. When the spool 2 is exhausted resistance to a feed stroke by the ratchet wheel 6 causes the pawl 8 to rock the counterbalanced member 9 against the force of the spring 12 and past its dead centre position until the member is arrested by a stop 11d and the spring 10 forces the pawl into engagement with the other ratchet wheel 7 to reverse the ribbon feed direction. Coil springs 16, 17 resists reverse movement of the ratchet wheels 6, 7 after a feed stroke but do not resist such a feed stroke. The feed stroke of the pawl 8 is not equal to an exact number of teeth on the ratchet wheel so that feed reversal usually requires two strokes to be effective and a different part of the ribbon is used after each reversal thus ensuring maximum wear. |
