Appeal No. 1995-5010
Application 08/116,261
the pending claims in the case.
The invention concerns an apparatus comprised of an
ultrasonic surgical handpiece driven by a piezoelectric
crystal transducer having a frequency control loop and an
automatic gain control loop. The latter has a limiter
connected to its output so a maximum error signal output of
the automatic gain control may be operator adjusted and
limited to achieve tissue selectivity. A low value resistor
in series and an inductor in parallel to the output of the
voltage source amplifier, which drives the transducer, provide
added stability of the operation of the transducer. The
invention is further illustrated by the following claim.
Claim 1 is selected as representative of the invention
and is reproduced below:
1. An electrical apparatus and an ultrasonic
piezoelectric crystal transducer in a surgical handpiece for
the fragmentation and aspiration of tissue the ultrasonic
piezoelectric crystal transducer driven by the apparatus,
which apparatus comprises:
a voltage controlled oscillator in series with an
amplifier and a first electronic control loop connected from a
feedback piezoelectric crystal through a phase comparator and
a loop filter to the voltage controlled oscillator, which
feedback crystal is mechanically coupled to an ultrasonic
-2-
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