(57) To provide an improved mechanical reversible spooling drive in a printer, a pair
of spool spindles (32; 34), each carrying an apertured circular plate with peripheral
ratchet teeth (32a; 32b: 34a; 34b) and a bail trigger (54: 55) spring loaded to extend
through the aperture from one side thereof, are provided at the limits of the print
path of a print head (24) driven reciprocally over the path. Print ribbon in the path
is spooled on and between the spindles generally obstructing the apertures and restraining
the triggers against the spring loading. Fixed abutments (52; 53) are engageable by
a respective trigger when its spool is empty to lock that spindle and to engage, when
the head is at the end of the path, a camming surface (64; 66) provided at each end
of a bail (20) pivotally mounted on the print head and rendered positionally bistable
by an overcentre mechanism (74) and place it in a position in which one of a pair
of pawis (60;62) engage the ratchet teeth to spool ribbon onto the "empty" spindle
each time the print head reaches that end of the print path.
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