| 摘要 |
<p>A daisy wheel printer having a daisy wheel (10) with a central disc portion (12) and character stalks (14), wherein a masking disc (20) is attached coaxially to the daisy wheel, the mask being larger than the central disc portion of the wheel so that it obscures the daisy wheel stalks in a radial zone of the wheel inwardly of the character petals (16). The mask (20) is provided with a single slit (26) over the interstice between a unique pair of character stalks (14A, 14B), to thereby define a unique datum or home location on the daisy wheel. This datum slit is detected by means of a light source (28) and light-sensitive detector (30) which emits a pulse each time the datum slit passes through a light beam directed towards the detector at the radial zone of the daisy wheel whereat the datum slit is provided. The invention provides a datum slit enabling optical detection of a datum location on the daisy wheel without in any way affecting the performance of the daisy wheel for printing and, in particular, without affecting the flexibility of the character stalks.</p> |
