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(11) | EP 0 402 754 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Vibration frequency setting mechanism of an engraving device provided with air pen |
| (57) There is disclosed a vibration frequency setting mechanism of an engraving device
provided with air pen. The vibration frequency setting mechanism comprises an engraving
device provided with an air pen (11) vibration frequency of which is varied in response
to compressed air to be supplied to the holder (12), a vibration frequency detector
(12) for detecting the vibration frequency of the air pen (11) and providing a pulse
signal (21) corresponding to the vibration frequency, a counter (4) for counting the
pulse signal (21), a pressure regulator (1) provided with a regulating terminal (2),
a vibration frequency setting circuit (5) for setting the vibration frequency (22)
of the air pen(11), a comparator (6) for receiving the output of the counter (4) and
the vibration frequency (22) and providing a logical "1" if the output of the counter
(4) is greater than the vibration frequency (22) and a logical "0" if the output of
the counter (4) is less than the vibration frequency (22), an output circuit (7) for
receiving the output of the comparator (6) and decrementing the analog output at a
given step if the output of the comparator (6) is a logical "1" and incrementing
the analog output at a given step if the output of the comparator (6) is a logical
"0", whereby the analog output of the output circuit (7) is supplied to the regulating
terminal (2) so that the compressed air is supplied to the holder (12). |